The Width of a Solar Coronal Mass Ejection and the Source of the Driving Magnetic Explosion

NASA Technical Reports Server (NTRS)

Moore, Ronald L.; Sterling, Alphonse C.; Suess, Steven T.

2007-01-01

We show that the strength of the magnetic field in the area covered by the flare arcade following a CME-producing ejective solar eruption can be estimated from the final angular width of the CME in the outer corona and the final angular width of the flare arcade. We assume (1) the flux-rope plasmoid ejected from the flare site becomes the interior of the CME plasmoid, (2) in the outer corona (R greater than 2R(sub Sun)) the CME is roughly a spherical plasmoid with legs shaped like a light bulb, and (3) beyond some height in or below the outer corona the CME plasmoid is in lateral pressure balance with the surrounding magnetic field. The strength of the nearly radial magnetic field in the outer corona is estimated from the radial component of the interplanetary magnetic field measured by Ulysses. We apply this model to three well-observed CMEs that exploded from flare regions of extremely different size and magnetic setting. One of these CMEs is an over-and-out CME that exploded from a laterally far offset compact ejective flare. In each event, the estimated source-region field strength is appropriate for the magnetic setting of the flare. This agreement (1) indicates that CMEs are propelled by the magnetic field of the CME plasmoid pushing against the surrounding magnetic field, (2) supports the magnetic-arch-blowout scenario for over-and-out CMEs, and (3) shows that a CME s final angular width in the outer corona can be estimated from the amount of magnetic flux covered by the source-region flare arcade.

Observations of the Coronal Mass Ejection with a Complex Acceleration Profile

NASA Astrophysics Data System (ADS)

Reva, A. A.; Kirichenko, A. S.; Ulyanov, A. S.; Kuzin, S. V.

2017-12-01

We study the coronal mass ejection (CME) with a complex acceleration profile. The event occurred on 2009 April 23. It had an impulsive acceleration phase, an impulsive deceleration phase, and a second impulsive acceleration phase. During its evolution, the CME showed signatures of different acceleration mechanisms: kink instability, prominence drainage, flare reconnection, and a CME–CME collision. The special feature of the observations is the usage of the TESIS EUV telescope. The instrument could image the solar corona in the Fe 171 Å line up to a distance of 2 {R}ȯ from the center of the Sun. This allows us to trace the CME up to the LASCO/C2 field of view without losing the CME from sight. The onset of the CME was caused by kink instability. The mass drainage occurred after the kink instability. The mass drainage played only an auxiliary role: it decreased the CME mass, which helped to accelerate the CME. The first impulsive acceleration phase was caused by the flare reconnection. We observed the two-ribbon flare and an increase of the soft X-ray flux during the first impulsive acceleration phase. The impulsive deceleration and the second impulsive acceleration phases were caused by the CME–CME collision. The studied event shows that CMEs are complex phenomena that cannot be explained with only one acceleration mechanism. We should seek a combination of different mechanisms that accelerate CMEs at different stages of their evolution.

Determination of Geometric and Kinematical Parameters of Coronal Mass Ejections Using STEREO Data

NASA Astrophysics Data System (ADS)

Fainshtein, V. G.; Tsivileva, D. M.; Kashapova, L. K.

2010-03-01

We present a new, relatively simple and fast method to determine true geometric and kinematical CME parameters from simultaneous STEREO A, B observations of CMEs. These parameters are the three-dimensional direction of CME propagation, velocity and acceleration of CME front, CME angular sizes and front position depending on time. The method is based on the assumption that CME shape may be described by a modification of so-called ice-cream cone models. The method has been tested for several CMEs.

Over-and-Out Coronal Mass Ejections: Blowouts of Magnetic Arches by Ejective Flares in One Foot

NASA Technical Reports Server (NTRS)

Moore, Ronald L.; Sterling, Alphonse C.

2006-01-01

Streamer puffs from compact ejective flares in the foot of an outer loop of the magnetic arcade under a streamer were recently identified as a new variety of coronal mass ejection (CME) (Bemporad, Sterling, Moore, & Poletto 2006, ApJ Letters, in press). In the reported examples, the compact flares produced only weak to moderate soft X-ray bursts having peak intensities no stronger than GOES class C3. Here, we present two examples of this type of CME in which the compact flare in the flank of the steamer base is much stronger (one M-class, the other X-class in GOES X-rays) and the resulting streamer puff is wider and brighter than in the discovery examples. Coronal dimming observed in SOHOBIT Fe XII images in the launching of each of these two CMEs M e r supports the view that these CMEs are produced by a high loop of the steamer arcade being blown out by magnetoplasma ejecta exploding up the leg of the loop from the flare. In addition, we present evidence that this same type of CME occurs on larger scales than in the above examples. We examine a sequence of flare eruptions seated on the north side of AR 8210 as it rotated across the southern hemisphere in late April and early May 1998. Each flare occurs in synchrony with the launching of a large CME centered on the equator. Coronal dimming in EIT Fe XII images shows the trans-equatorial footprints of these CMEs extending north from the flare site. The set of flare-with-CME events includes the trans-equatorial loop eruptions reported by Khan & Hudson (1998, GRL, 27, 1083). Our observations indicate that these CMEs were not driven by the self-eruption of the transequatorial loops, but that these loops were part of a trans-equatorial magnetic arch that was blown open by ejecta from the flares on the north side of AR 8210. Thus, a relatively compact ejective flare can be the driver of a CME that is much larger in lateral extent than the flare and is laterally far offset from the flare. It has previously been thought that such spatial disparities between the flare and the CME prohibited the flare explosion from being the driver of the CME (e.g., Kahler 1992, ARA&A, 30, 113).

Global Energetics of Solar Flares. VI. Refined Energetics of Coronal Mass Ejections

NASA Astrophysics Data System (ADS)

Aschwanden, Markus J.

2017-09-01

In this study, we refine the coronal mass ejection (CME) model that was presented in an earlier study of the global energetics of solar flares and associated CMEs and apply it to all (860) GOES M- and X-class flare events observed during the first seven years (2010-2016) of the Solar Dynamics Observatory (SDO) mission. The model refinements include (1) the CME geometry in terms of a 3D volume undergoing self-similar adiabatic expansion, (2) the solar gravitational deceleration during the propagation of the CME, which discriminates between eruptive and confined CMEs, (3) a self-consistent relationship between the CME center-of-mass motion detected during EUV dimming and the leading-edge motion observed in white-light coronagraphs, (4) the equipartition of the CME’s kinetic and thermal energies, and (5) the Rosner-Tucker-Vaiana scaling law. The refined CME model is entirely based on EUV-dimming observations (using Atmospheric Imager Assembly (AIA)/SDO data) and complements the traditional white-light scattering model (using Large-Angle and Spectrometric Coronagraph Experiment (LASCO)/Solar and Heliospheric Observatory data), and both models are independently capable of determining fundamental CME parameters. Comparing the two methods, we find that (1) LASCO is less sensitive than AIA in detecting CMEs (in 24% of the cases), (2) CME masses below {m}{cme}≲ {10}14 g are underestimated by LASCO, (3) AIA and LASCO masses, speeds, and energies agree closely in the statistical mean after the elimination of outliers, and (4) the CME parameters speed v, emission measure-weighted flare peak temperature T e , and length scale L are consistent with the following scaling laws: v\\propto {T}e1/2, v\\propto {({m}{cme})}1/4, and {m}{cme}\\propto {L}2.

DATA-CONSTRAINED CORONAL MASS EJECTIONS IN A GLOBAL MAGNETOHYDRODYNAMICS MODEL

DOE Office of Scientific and Technical Information (OSTI.GOV)

Jin, M.; Manchester, W. B.; Van der Holst, B.

We present a first-principles-based coronal mass ejection (CME) model suitable for both scientific and operational purposes by combining a global magnetohydrodynamics (MHD) solar wind model with a flux-rope-driven CME model. Realistic CME events are simulated self-consistently with high fidelity and forecasting capability by constraining initial flux rope parameters with observational data from GONG, SOHO /LASCO, and STEREO /COR. We automate this process so that minimum manual intervention is required in specifying the CME initial state. With the newly developed data-driven Eruptive Event Generator using Gibson–Low configuration, we present a method to derive Gibson–Low flux rope parameters through a handful ofmore » observational quantities so that the modeled CMEs can propagate with the desired CME speeds near the Sun. A test result with CMEs launched with different Carrington rotation magnetograms is shown. Our study shows a promising result for using the first-principles-based MHD global model as a forecasting tool, which is capable of predicting the CME direction of propagation, arrival time, and ICME magnetic field at 1 au (see the companion paper by Jin et al. 2016a).« less

Near-Sun and 1 AU magnetic field of coronal mass ejections: a parametric study

NASA Astrophysics Data System (ADS)

Patsourakos, S.; Georgoulis, M. K.

2016-11-01

Aims: The magnetic field of coronal mass ejections (CMEs) determines their structure, evolution, and energetics, as well as their geoeffectiveness. However, we currently lack routine diagnostics of the near-Sun CME magnetic field, which is crucial for determining the subsequent evolution of CMEs. Methods: We recently presented a method to infer the near-Sun magnetic field magnitude of CMEs and then extrapolate it to 1 AU. This method uses relatively easy to deduce observational estimates of the magnetic helicity in CME-source regions along with geometrical CME fits enabled by coronagraph observations. We hereby perform a parametric study of this method aiming to assess its robustness. We use statistics of active region (AR) helicities and CME geometrical parameters to determine a matrix of plausible near-Sun CME magnetic field magnitudes. In addition, we extrapolate this matrix to 1 AU and determine the anticipated range of CME magnetic fields at 1 AU representing the radial falloff of the magnetic field in the CME out to interplanetary (IP) space by a power law with index αB. Results: The resulting distribution of the near-Sun (at 10 R⊙) CME magnetic fields varies in the range [0.004, 0.02] G, comparable to, or higher than, a few existing observational inferences of the magnetic field in the quiescent corona at the same distance. We also find that a theoretically and observationally motivated range exists around αB = -1.6 ± 0.2, thereby leading to a ballpark agreement between our estimates and observationally inferred field magnitudes of magnetic clouds (MCs) at L1. Conclusions: In a statistical sense, our method provides results that are consistent with observations.

Coronal Mass Ejections and Dimmings: A Comparative Study using MHD Simulations and SDO Observations

NASA Astrophysics Data System (ADS)

Jin, M.; Cheung, C. M. M.; DeRosa, M. L.; Nitta, N.; Schrijver, K.

2017-12-01

Solar coronal dimmings have been observed extensively in the past two decades. Due to their close association with coronal mass ejections (CMEs), there is a critical need to improve our understanding of the physical processes that cause dimmings and determine their relationship with CMEs. In this study, we investigate coronal dimmings by combining simulation and observational efforts. By utilizing a data-driven global magnetohydrodynamics model (AWSoM: Alfven-wave Solar Model), we simulate coronal dimmings resulting from different CME energetics and flux rope configurations. We synthesize the emissions of different EUV spectral bands/lines and compare with SDO/AIA and EVE observations. A detailed analysis of simulation and observation data suggests that although the transient dimming / brightening patterns could relate to plasma heating processes (either by adiabatic compression or reconnection), the long-lasting "core" and "remote" (also known as "secondary") dimmings both originate from regions with open/quasi-open fields and are caused by mass loss process. The mass loss in the remote dimming region is induced by CME-driven shock. Using metrics such as dimming depth, dimming slope, and recovery time, we investigate the relationship between dimmings and CME properties (e.g., CME mass, CME speed) in the simulation. Our result suggests that coronal dimmings encode important information about CME energetics, CME-driven shock properties, and magnetic configuration of erupting flux ropes. We also discuss how our knowledge about solar coronal dimmings could be extended to the study of stellar CMEs, which may prove important for exoplanet atmospheres and habitability but which are currently not observable.

Understanding Coronal Dimming and its Relation to Coronal Mass Ejections

NASA Astrophysics Data System (ADS)

Mason, J. P.; Woods, T. N.; Caspi, A.; Hock, R. A.

2013-12-01

When extreme ultraviolet (EUV) emitting material in the corona is lost during a coronal mass ejection (CME), the solar spectral irradiance is impacted and these effects are observed in data from the Solar Dynamics Observatory (SDO) EUV Variability Experiment (EVE) and Atmospheric Imaging Assembly (AIA). This process is one of the physical mechanisms that can lead to the observation of 'coronal dimming,' a phenomenon lasting eight hours on average and rarely persisting longer than one day. Other mechanisms that can cause observed dimming include obscuration of bright material (e.g., flare arcade) by dark material (e.g., filament), temperature evolution (e.g., cool plasma being heated causing transient decreases in characteristic emission lines), and propagation of global waves. Each of these processes has a unique spectral signature, which will be explained and exemplified. In particular, the 7 August 2010 M1.0 flare with associated ~870 km/s CME will be analyzed in detail using both AIA and EVE to demonstrate new techniques for isolating dimming due to the CME ('core dimming'). Further analysis will estimate CME mass and velocity using only parameterization of core dimming and compare these estimates to traditionally calculated CME kinetics.

Multi-spacecraft Observations of the Coronal and Interplanetary Evolution of a Solar Eruption Associated with Two Active Regions

DOE Office of Scientific and Technical Information (OSTI.GOV)

Hu, Huidong; Liu, Ying D.; Wang, Rui

We investigate the coronal and interplanetary evolution of a coronal mass ejection (CME) launched on 2010 September 4 from a source region linking two active regions (ARs), 11101 and 11103, using extreme ultraviolet imaging, magnetogram, white-light, and in situ observations from SDO , STEREO , SOHO , VEX , and Wind . A potential-field source-surface model is employed to examine the configuration of the coronal magnetic field surrounding the source region. The graduated cylindrical shell model and a triangulation method are applied to determine the kinematics of the CME in the corona and interplanetary space. From the remote sensing andmore » in situ observations, we obtain some key results: (1) the CME was deflected in both the eastward and southward directions in the low corona by the magnetic pressure from the two ARs, and possibly interacted with another ejection, which caused that the CME arrived at VEX that was longitudinally distant from the source region; (2) although VEX was closer to the Sun, the observed and derived CME arrival times at VEX are not earlier than those at Wind , which suggests the importance of determining both the frontal shape and propagation direction of the CME in interplanetary space; and (3) the ICME was compressed in the radial direction while the longitudinal transverse size was extended.« less

Global Energetics in Solar Flares and Coronal Mass Ejections

NASA Astrophysics Data System (ADS)

Aschwanden, Markus J.

2017-08-01

We present a statistical study of the energetics of coronal mass ejections (CME) and compare it with the magnetic, thermal, and nonthermal energy dissipated in flares. The physical parameters of CME speeds, mass, and kinetic energies are determined with two different independent methods, i.e., the traditional white-light scattering method using LASCO/SOHO data, and the EUV dimming method using AIA/SDO data. We analyze all 860 GOES M- and X-class flare events observed during the first 7 years (2010-2016) of the SDO mission. The new ingredients of our CME modeling includes: (1) CME geometry in terms of a self-similar adiabatic expansion, (2) DEM analysis of CME mass over entire coronal temperature range, (3) deceleration of CME due to gravity force which controls the kinetic and potentail CME energy as a function of time, (4) the critical speed that controls eruptive and confined CMEs, (5) the relationship between the center-of-mass motion during EUV dimming and the leading edge motion observed in white-light coronagraphs. Novel results are: (1) Physical parameters obtained from both the EUV dimming and white-light method can be reconciled; (2) the equi-partition of CME kinetic and thermal flare energy; (3) the Rosner-Tucker-Vaiana scaling law. We find that the two methods in EUV and white-light wavelengths are highly complementary and yield more complete models than each method alone.

EIT Observations of Coronal Mass Ejections

NASA Technical Reports Server (NTRS)

Gurman, J. B.; Fisher, Richard B. (Technical Monitor)

2000-01-01

Before the Solar and Heliospheric Observatory (SOHO), we had only the sketchiest of clues as to the nature and topology of coronal mass ejections (CMEs) below 1.1 - 1.2 solar radii. Occasionally, dimmings (or 'transient coronal holes') were observed in time series of soft X-ray images, but they were far less frequent than CME's. Simply by imaging the Sun frequently and continually at temperatures of 0.9 - 2.5 MK we have stumbled upon a zoo of CME phenomena in this previously obscured volume of the corona: (1) waves, (2) dimmings, and (3) a great variety of ejecta. In the three and a half years since our first observations of coronal waves associated with CME's, combined Large Angle Spectroscopic Coronagraph (LASCO) and extreme ultra-violet imaging telescope (EIT) synoptic observations have become a standard prediction tool for space weather forecasters, but our progress in actually understanding the CME phenomenon in the low corona has been somewhat slower. I will summarize the observations of waves, hot (> 0.9 MK) and cool ejecta, and some of the interpretations advanced to date. I will try to identify those phenomena, analysis of which could most benefit from the spectroscopic information available from ultraviolet coronograph spectrometer (UVCS) observations.

Solar radio bursts as a tool for space weather forecasting

NASA Astrophysics Data System (ADS)

Klein, Karl-Ludwig; Matamoros, Carolina Salas; Zucca, Pietro

2018-01-01

The solar corona and its activity induce disturbances that may affect the space environment of the Earth. Noticeable disturbances come from coronal mass ejections (CMEs), which are large-scale ejections of plasma and magnetic fields from the solar corona, and solar energetic particles (SEPs). These particles are accelerated during the explosive variation of the coronal magnetic field or at the shock wave driven by a fast CME. In this contribution, it is illustrated how full Sun microwave observations can lead to (1) an estimate of CME speeds and of the arrival time of the CME at the Earth, (2) the prediction of SEP events attaining the Earth. xml:lang="fr"

The soft X-ray coronal mass ejection above solar limb of 1998 April 23

NASA Astrophysics Data System (ADS)

Chen, Xiao-juan

Using the observational materials of SXT/HXT aboard satellite Yohkoh and the Nobeyama Radioheliograph (NoRH) on 1998-04-23, a comprehensive study of the soft X-ray coronal mass ejection (CME) above solar SE limb shows that there were two magnetic dipolar sources (MDSs), one magnetic capacity belt (MCB) between the MDSs, one neutral current sheet (NCS) and some rare activation sources (ASs). When the MCB was changed by the ASs to become a magnetic energy belt (MEB), both mass and energy were concentrated to form the NCS. When the MDSs were connected by the MEB, the NCS was formed and the CME occurred. Mass was ejected not only from the NCS, but also from the whole MEB. The expanding loop of the CME had the two MDSs as footpoints. The top of the loop was always inclined towards the footpoint of the weaker source, and its locus marks the NCS.

Effect of gravitational stratification on the propagation of a CME

NASA Astrophysics Data System (ADS)

Pagano, P.; Mackay, D. H.; Poedts, S.

2013-12-01

Context. Coronal mass ejections (CMEs) are the most violent phenomenon found on the Sun. One model that explains their occurrence is the flux rope ejection model. A magnetic flux rope is ejected from the solar corona and reaches the interplanetary space where it interacts with the pre-existing magnetic fields and plasma. Both gravity and the stratification of the corona affect the early evolution of the flux rope. Aims: Our aim is to study the role of gravitational stratification on the propagation of CMEs. In particular, we assess how it influences the speed and shape of CMEs and under what conditions the flux rope ejection becomes a CME or when it is quenched. Methods: We ran a set of MHD simulations that adopt an eruptive initial magnetic configuration that has already been shown to be suitable for a flux rope ejection. We varied the temperature of the backgroud corona and the intensity of the initial magnetic field to tune the gravitational stratification and the amount of ejected magnetic flux. We used an automatic technique to track the expansion and the propagation of the magnetic flux rope in the MHD simulations. From the analysis of the parameter space, we evaluate the role of gravitational stratification on the CME speed and expansion. Results: Our study shows that gravitational stratification plays a significant role in determining whether the flux rope ejection will turn into a full CME or whether the magnetic flux rope will stop in the corona. The CME speed is affected by the background corona where it travels faster when the corona is colder and when the initial magnetic field is more intense. The fastest CME we reproduce in our parameter space travels at ~850 km s-1. Moreover, the background gravitational stratification plays a role in the side expansion of the CME, and we find that when the background temperature is higher, the resulting shape of the CME is flattened more. Conclusions: Our study shows that although the initiation mechanisms of the CME are purely magnetic, the background coronal plasma plays a key role in the CME propagation, and full MHD models should be applied when one focuses especially on the production of a CME from a flux rope ejection. Movies are available in electronic form at http://www.aanda.org

ARE HALO-LIKE SOLAR CORONAL MASS EJECTIONS MERELY A MATTER OF GEOMETRIC PROJECTION EFFECTS?

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kwon, Ryun-Young; Zhang, Jie; Vourlidas, Angelos, E-mail: ryunyoung.kwon@gmail.com

2015-02-01

We investigated the physical nature of halo coronal mass ejections (CMEs) based on the stereoscopic observations from the two STEREO spacecraft, Ahead and Behind (hereafter A and B), and the SOHO spacecraft. Sixty-two halo CMEs occurred as observed by SOHO LASCO C2 for the three-year period from 2010 to 2012 during which the separation angles between SOHO and STEREO were nearly 90°. In such quadrature configuration, the coronagraphs of STEREO, COR2-A and -B, showed the side view of those halo CMEs seen by C2. It has been widely believed that the halo appearance of a CME is caused by themore » geometric projection effect, i.e., a CME moves along the Sun-observer line. In other words, it would appear as a non-halo CME if viewed from the side. However, to our surprise, we found that 41 out of 62 events (66%) were observed as halo CMEs by all coronagraphs. This result suggests that a halo CME is not just a matter of the propagating direction. In addition, we show that a CME propagating normal to the line of sight can be observed as a halo CME due to the associated fast magnetosonic wave or shock front. We conclude that the apparent width of CMEs, especially halos or partial halos is driven by the existence and the extent of the associated waves or shocks and does not represent an accurate measure of the CME ejecta size. This effect needs to be taken into careful consideration in space weather predictions and modeling efforts.« less

A CORONAL HOLE'S EFFECTS ON CORONAL MASS EJECTION SHOCK MORPHOLOGY IN THE INNER HELIOSPHERE

DOE Office of Scientific and Technical Information (OSTI.GOV)

Wood, B. E.; Wu, C.-C.; Howard, R. A.

2012-08-10

We use STEREO imagery to study the morphology of a shock driven by a fast coronal mass ejection (CME) launched from the Sun on 2011 March 7. The source region of the CME is located just to the east of a coronal hole. The CME ejecta is deflected away from the hole, in contrast with the shock, which readily expands into the fast outflow from the coronal hole. The result is a CME with ejecta not well centered within the shock surrounding it. The shock shape inferred from the imaging is compared with in situ data at 1 AU, wheremore » the shock is observed near Earth by the Wind spacecraft, and at STEREO-A. Shock normals computed from the in situ data are consistent with the shock morphology inferred from imaging.« less

Flares, ejections, proton events

NASA Astrophysics Data System (ADS)

Belov, A. V.

2017-11-01

Statistical analysis is performed for the relationship of coronal mass ejections (CMEs) and X-ray flares with the fluxes of solar protons with energies >10 and >100 MeV observed near the Earth. The basis for this analysis was the events that took place in 1976-2015, for which there are reliable observations of X-ray flares on GOES satellites and CME observations with SOHO/LASCO coronagraphs. A fairly good correlation has been revealed between the magnitude of proton enhancements and the power and duration of flares, as well as the initial CME speed. The statistics do not give a clear advantage either to CMEs or the flares concerning their relation with proton events, but the characteristics of the flares and ejections complement each other well and are reasonable to use together in the forecast models. Numerical dependences are obtained that allow estimation of the proton fluxes to the Earth expected from solar observations; possibilities for improving the model are discussed.

Connecting white light to in situ observations of 22 coronal mass ejections from the Sun to 1 AU

NASA Astrophysics Data System (ADS)

Moestl, C.; Amla, K.; Farrugia, C. J.; Hall, J. R.; Liewer, P. C.; De Jong, E.; Colaninno, R. C.; Vourlidas, A.; Veronig, A. M.; Rollett, T.; Temmer, M.; Peinhart, V.; Davies, J.; Lugaz, N.; Liu, Y. D.; McEnulty, T.; Luhmann, J. G.; Galvin, A. B.

2013-12-01

We study the feasibility of using a Heliospheric Imager (HI) instrument, such as STEREO/HI, for unambiguously connecting remote images to in situ observations of coronal mass ejection (CMEs). Our goal is to develop and test methods to predict CME parameters from heliospheric images, but our dataset can actually be used to benchmark any ICME propagation model. The results are of interest concerning future missions such as Solar Orbiter, or a dedicated space weather mission at the Sun-Earth L5 point (e.g. EASCO mission concept). We compare the predictions for speed and arrival time for 22 CME events (between 2008-2012), each observed remotely by one STEREO spacecraft, to the interplanetary coronal mass ejection (ICME) speed and arrival time observed at in situ observatories (STEREO PLASTIC/IMPACT, Wind SWE/MFI). We use forward modeling for STEREO-COR2, and geometrical models for STEREO-HII, assuming different CME front shapes (Fixed-Phi, Harmonic Mean, Self-similar expansion), and fit them to the CME time-elongation functions with the SolarSoft SATPLOT tool, assuming constant CME speed and direction. The arrival times derived from imaging match the in situ ones +/- 8 hours, and speeds are consistent within +/-300 km/s, including CME apex/flank effects. We find no preference in the predictive capability for any of the 3 geometries used on the full dataset, consisting of front- and backsided, slow and fast CMEs (up to 2700 km/s). We search for new empirical relations between the predicted and observed speeds and arrival times, enhancing the HI predictive capabilities. Additionally, for very fast and back-sided CMEs, strong differences between the results of the HI models arise, consistent with theoretical expectations by Lugaz and Kintner (2013, Solar Physics). This work has received funding from the European Commission FP7 Project COMESEP (263252).

Evidence for a current sheet forming in the wake of a coronal mass ejection from multi-viewpoint coronagraph observations

NASA Astrophysics Data System (ADS)

Patsourakos, S.; Vourlidas, A.

2011-01-01

Context. Ray-like features observed by coronagraphs in the wake of coronal mass ejections (CMEs) are sometimes interpreted as the white light counterparts of current sheets (CSs) produced by the eruption. The 3D geometry of these ray-like features is largely unknown and its knowledge should clarify their association to the CS and place constraints on CME physics and coronal conditions. Aims: If these rays are related to field relaxation behind CMEs, therefore representing current sheets, then they should be aligned to the CME axis. With this study we test these important implications for the first time. Methods: An example of such a post-CME ray was observed by various coronagraphs, including these of the Sun Earth Connection Coronal and Heliospheric investigation (SECCHI) onboard the Solar Terrestrial Relations Observatory (STEREO) twin spacecraft and the Large Angle Spectrometric Coronagraph (LASCO) onboard the Solar and Heliospheric Observatory (SOHO). The ray was observed in the aftermath of a CME which occurred on 9 April 2008. The twin STEREO spacecraft were separated by about 48° on that day. This significant separation combined with a third “eye” view supplied by LASCO allow for a truly multi-viewpoint observation of the ray and of the CME. We applied 3D forward geometrical modeling to the CME and to the ray as simultaneously viewed by SECCHI-A and B and by SECCHI-A and LASCO, respectively. Results: We found that the ray can be approximated by a rectangular slab, nearly aligned with the CME axis, and much smaller than the CME in both terms of thickness and depth (≈0.05 and 0.15 R⊙ respectively). The ray electron density and temperature were substantially higher than their values in the ambient corona. We found that the ray and CME are significantly displaced from the associated post-CME flaring loops. Conclusions: The properties and location of the ray are fully consistent with the expectations of the standard CME theories for post-CME current sheets. Therefore, our multi-viewpoint observations supply strong evidence that the observed post-CME ray is indeed related to a post-CME current sheet. Movies are only available in electronic form at http://www.aanda.org

The Width of a Solar Coronal Mass Ejection and the Source of the Driving Magnetic Explosion: A Test of the Standard Scenario for CME Production

NASA Technical Reports Server (NTRS)

Moore, Ronald L.; Sterling, Alphonse C.; Suess, Steven T.

2007-01-01

We show that the strength (B(sub F1are)) of the magnetic field in the area covered by the flare arcade following a CME-producing ejective solar eruption can be estimated from the final angular width (Final Theta(sub CME)) of the CME in the outer corona and the final angular width (Theta(sub Flare)) of the flare arcade: B(sub Flare) approx. equals 1.4[(Final Theta(sub CME)/Theta(sub Flare)] (exp 2)G. We assume (1) the flux-rope plasmoid ejected from the flare site becomes the interior of the CME plasmoid; (2) in the outer corona (R > 2 (solar radius)) the CME is roughly a "spherical plasmoid with legs" shaped like a lightbulb; and (3) beyond some height in or below the outer corona the CME plasmoid is in lateral pressure balance with the surrounding magnetic field. The strength of the nearly radial magnetic field in the outer corona is estimated from the radial component of the interplanetary magnetic field measured by Ulysses. We apply this model to three well-observed CMEs that exploded from flare regions of extremely different size and magnetic setting. One of these CMEs was an over-and-out CME, that is, in the outer corona the CME was laterally far offset from the flare-marked source of the driving magnetic explosion. In each event, the estimated source-region field strength is appropriate for the magnetic setting of the flare. This agreement (1) indicates that CMEs are propelled by the magnetic field of the CME plasmoid pushing against the surrounding magnetic field; (2) supports the magnetic-arch-blowout scenario for over-and-out CMEs; and (3) shows that a CME's final angular width in the outer corona can be estimated from the amount of magnetic flux covered by the source-region flare arcade.

A STEREO Survey of Magnetic Cloud Coronal Mass Ejections Observed at Earth in 2008–2012

DOE Office of Scientific and Technical Information (OSTI.GOV)

Wood, Brian E.; Wu, Chin-Chun; Howard, Russell A.

We identify coronal mass ejections (CMEs) associated with magnetic clouds (MCs) observed near Earth by the Wind spacecraft from 2008 to mid-2012, a time period when the two STEREO spacecraft were well positioned to study Earth-directed CMEs. We find 31 out of 48 Wind MCs during this period can be clearly connected with a CME that is trackable in STEREO imagery all the way from the Sun to near 1 au. For these events, we perform full 3D reconstructions of the CME structure and kinematics, assuming a flux rope (FR) morphology for the CME shape, considering the full complement ofmore » STEREO and SOHO imaging constraints. We find that the FR orientations and sizes inferred from imaging are not well correlated with MC orientations and sizes inferred from the Wind data. However, velocities within the MC region are reproduced reasonably well by the image-based reconstruction. Our kinematic measurements are used to provide simple prescriptions for predicting CME arrival times at Earth, provided for a range of distances from the Sun where CME velocity measurements might be made. Finally, we discuss the differences in the morphology and kinematics of CME FRs associated with different surface phenomena (flares, filament eruptions, or no surface activity).« less

Plasma Heating During Coronal Mass Ejections

NASA Astrophysics Data System (ADS)

Murphy, N. A.; Shen, C.; Rimple, R.; Raymond, J. C.

2016-12-01

Several recent observational analyses have shown that plasma heating enters into the energy budget of coronal mass ejections (CMEs) at about the same order of magnitude as the kinetic energy. The ultimate source of the heating is the magnetic field, but the mechanisms by which magnetic energy is converted to thermal energy are poorly understood. We will review observational evidence for CME heating and discuss candidate mechanisms that may be responsible for the heating. We will discuss the Python implementation of a non-equilibrium ionization model and its application to CME plasma, and report on progress on modeling three events where the Ultraviolet Coronagraph Spectrometer (UVCS) on the Solar and Heliospheric Observatory (SOHO) observed the same ejecta at multiple heights.

Determining the Full Halo Coronal Mass Ejection Characteristics

NASA Astrophysics Data System (ADS)

Fainshtein, V. G.

2010-11-01

Observing halo coronal mass ejections (HCMEs) in the coronagraph field of view allows one to only determine the apparent parameters in the plane of the sky. Recently, several methods have been proposed allowing one to find some true geometrical and kinematical parameters of HCMEs. In most cases, a simple cone model was used to describe the CME shape. Observations show that various modifications of the cone model ("ice cream models") are most appropriate for describing the shapes of individual CMEs. This paper uses the method of determining full HCME parameters proposed by the author earlier, for determining the parameters of 45 full HCMEs, with various modifications of their shapes. I show that the determined CME characteristics depend significantly on the chosen CME shape. I conclude that the absence of criteria for a preliminary evaluation of the CME shape is a major source of error in determining the true parameters of a full HCME with any of the known methods. I show that, regardless of the chosen CME form, the trajectory of practically all the HCMEs in question deviate from the radial direction towards the Sun-Earth axis at the initial stage of their movement, and their angular size, on average, significantly exceeds that of all the observable CMEs.

Constraints on CME Evolution from in situ Observations of Ionic Charge States

NASA Technical Reports Server (NTRS)

Gruesbeck, Jacob R.; Lepri, Susan T.; Zurbuchen, Thomas H.; Antiochos, Spiro K.

2010-01-01

We present a novel procedure for deriving the physical properties of Coronal Mass Ejections (CMES) in the corona. Our methodology uses in-situ measurements of ionic charge states of C, O, Si and Fe in the heliosphere and interprets them in the context of a model for the early evolution of ICME plasma, between 2 - 5 R-solar. We find that the data can be fit only by an evolution that consists of an initial heating of the plasma, followed by an expansion that ultimately results in cooling. The heating profile is consistent with a compression of coronal plasma due to flare reconnect ion jets and an expansion cooling due to the ejection, as expected from the standard CME/flare model. The observed frozen-in ionic charge states reflect this time-history and, therefore, provide important constraints for the heating and expansion time-scales, as well as the maximum temperature the CME plasma is heated to during its eruption. Furthermore, our analysis places severe limits on the possible density of CME plasma in the corona. We discuss the implications of our results for CME models and for future analysis of ICME plasma composition.

SUN-TO-EARTH CHARACTERISTICS OF THE 2012 JULY 12 CORONAL MASS EJECTION AND ASSOCIATED GEO-EFFECTIVENESS

DOE Office of Scientific and Technical Information (OSTI.GOV)

Hu, Huidong; Liu, Ying D.; Wang, Rui

We analyze multi-spacecraft observations associated with the 2012 July 12 coronal mass ejection (CME), covering the source region on the Sun from the Solar Dynamics Observatory , stereoscopic imaging observations from the Solar Terrestrial Relations Observatory ( STEREO ), magnetic field characteristics from Mercury Surface, Space Environment, Geochemistry, and Ranging ( MESSENGER ), and type II radio burst and in situ measurements from Wind . A triangulation method based on STEREO stereoscopic observations is employed to determine the kinematics of the CME, and the outcome is compared with the results derived from the type II radio burst using a solarmore » wind electron density model. A Grad–Shafranov technique is applied to Wind in situ data to reconstruct the flux-rope structure and compare it with the observations of the solar source region, which helps in understanding the geo-effectiveness associated with the CME structure. Our conclusions are as follows: (1) the CME undergoes an impulsive acceleration, a rapid deceleration before reaching MESSENGER , and then a gradual deceleration out to 1 au, which should be considered in CME kinematics models; (2) the type II radio burst was probably produced from a high-density interaction region between the CME-driven shock and a nearby streamer or from the shock flank with lower heights, which implies uncertainties in the determination of CME kinematics using solely type II radio bursts; (3) the flux-rope orientation and chirality deduced from in situ reconstructions at Wind agree with those obtained from solar source observations; (4) the prolonged southward magnetic field near the Earth is mainly from the axial component of the largely southward inclined flux rope, which indicates the importance of predicting both the flux-rope orientation and magnetic field components in geomagnetic activity forecasting.« less

GLOBAL ENERGETICS OF SOLAR FLARES. IV. CORONAL MASS EJECTION ENERGETICS

DOE Office of Scientific and Technical Information (OSTI.GOV)

Aschwanden, Markus J., E-mail: aschwanden@lmsal.com

2016-11-01

This study entails the fourth part of a global flare energetics project, in which the mass m {sub cme}, kinetic energy E {sub kin}, and the gravitational potential energy E {sub grav} of coronal mass ejections (CMEs) is measured in 399 M and X-class flare events observed during the first 3.5 years of the Solar Dynamics Observatory (SDO) mission, using a new method based on the EUV dimming effect. EUV dimming is modeled in terms of a radial adiabatic expansion process, which is fitted to the observed evolution of the total emission measure of the CME source region. The modelmore » derives the evolution of the mean electron density, the emission measure, the bulk plasma expansion velocity, the mass, and the energy in the CME source region. The EUV dimming method is truly complementary to the Thomson scattering method in white light, which probes the CME evolution in the heliosphere at r ≳ 2 R {sub ⊙}, while the EUV dimming method tracks the CME launch in the corona. We compare the CME parameters obtained in white light with the LASCO/C2 coronagraph with those obtained from EUV dimming with the Atmospheric Imaging Assembly onboard the SDO for all identical events in both data sets. We investigate correlations between CME parameters, the relative timing with flare parameters, frequency occurrence distributions, and the energy partition between magnetic, thermal, nonthermal, and CME energies. CME energies are found to be systematically lower than the dissipated magnetic energies, which is consistent with a magnetic origin of CMEs.« less

Deflections of Fast Coronal Mass Ejections and the Properties of Associated Solar Energetic Particle Events (POSTPRINT)

DTIC Science & Technology

2012-09-20

coronal mass ejection (CME) source regions can deflect fast CMEs from their expected trajectories in space, explaining the appearance of driverless shocks...the appearance of driverless shocks at 1 AU from CMEs ejected near solar central meridian (CM). This suggests that SEP events originating in CME-driven...interplanetary CME (ICME) drivers. Most such driverless shocks occur only from CMEs near the solar limbs, but these disk-center CMEs were located adjacent to CHs

The association of transequatorial loops in the solar corona with coronal mass ejection onset

NASA Astrophysics Data System (ADS)

Glover, A.; Harra, L. K.; Matthews, S. A.; Foley, C. A.

2003-03-01

It has been shown that transequatorial loops can disappear in association with the onset of a coronal mass ejection (CME) (Khan & Hudson \\cite{khan}). We extend this result by considering a larger sample of transequatorial loop systems (TLS) to investigate their associated flaring and CME activity. We find 10 of a total 18 TLS considered here to be associated with flaring and CME onset originating from a connected active region. A total 33 cases of flaring and associated CME onset are observed from these 10 systems during their lifetime. We observe the influence of this activity on the TLS in each case. In contrast to the Khan & Hudson result, we find evidence that transequatorial loop eruption leading to soft X-ray brightening equivalent in temperature to a B-class flare is equally as common as dimming in the corona. Consequently we conclude that the scenario observed by Khan & Hudson is not universal and that other types of CME-TLS association occur. It was found that for transequatorial loops that were associated with CMEs the asymmetry in longitude was larger than for those that were not associated to a CME by 10o. In addition, the extent in latitude (as a measure of the loop length) was nearly twice as large for those TLS associated with CMEs than those that were not. The asymmetry in latitude was actually on average larger for those TLS not associated with CMEs, than for those that were. This suggests that differential rotation is not a major contributor to the production of CMEs from transequatorial loops. Instead it is more likely for a CME to be produced if the loop is long, and if there is a large asymmetry in longitude. The implications of these results for CME onset prediction are discussed.

The Radial Speed - Expansion Speed Relation for Earth-Directed CMEs

NASA Astrophysics Data System (ADS)

Makela, P. A.; Gopalswamy, N.; Yashiro, S.

2013-12-01

The propagation speed of Earth-directed coronal mass ejections (CMEs) is an essential parameter needed in space weather forecasting. However, the true propagation speed of Earth-directed CMEs cannot be measured accurately from coronagraph images taken from Earth's view. In order to circumvent the inaccuracies of speed measurements due to the projection effects, empirical relations expressing the radial speed (Vrad) of the CME as a function of the CME expansion speed (Vexp) have been suggested. Vexp is defined as the apparent speed the CME is spreading in the coronagraph's field of view. During 2010-2012 STEREO spacecraft provided a side view of Earth-directed CMEs, allowing measurements of true CME speeds and widths. In a case study of the 2011 February 15 CME Gopalswamy et al. (2012) compared three Vrad-Vexp relations (flat cone, full or shallow ice cream cone - Gopalswamy et al., 2009) and found the closest match with the observations for the (full ice cream cone) relation Vrad = 1/2(1 + cot w)Vexp, where w is the half width of the CME. Using the STEREO/SECCHI and SOHO/LASCO observations during this opportune period, we expand this analysis to a larger set of Earth-directed CMEs. We compare the computed CME speed estimates with the measured true speeds and estimate the accuracy of the Vrad-Vexp relations. References: Gopalswamy, N. et al. (2009), The expansion and radial speeds of coronal mass ejections, Cent. Eur. Astrophys. Bull., 33, 115. Gopalswamy, N. et al. (2012), The relationship between the expansion speed and radial speed of CMEs confirmed using quadrature observations of the 2011 February 15 CME, Sun and Geosphere, 7(1), 7.

HOMOLOGOUS JET-DRIVEN CORONAL MASS EJECTIONS FROM SOLAR ACTIVE REGION 12192

DOE Office of Scientific and Technical Information (OSTI.GOV)

Panesar, Navdeep K.; Sterling, Alphonse C.; Moore, Ronald L., E-mail: navdeep.k.panesar@nasa.gov

We report observations of homologous coronal jets and their coronal mass ejections (CMEs) observed by instruments onboard the Solar Dynamics Observatory (SDO) and the Solar and Heliospheric Observatory (SOHO) spacecraft. The homologous jets originated from a location with emerging and canceling magnetic field at the southeastern edge of the giant active region (AR) of 2014 October, NOAA 12192. This AR produced in its interior many non-jet major flare eruptions (X- and M- class) that made no CME. During October 20 to 27, in contrast to the major flare eruptions in the interior, six of the homologous jets from the edgemore » resulted in CMEs. Each jet-driven CME (∼200–300 km s{sup −1}) was slower-moving than most CMEs, with angular widths (20°–50°) comparable to that of the base of a coronal streamer straddling the AR and were of the “streamer-puff” variety, whereby the preexisting streamer was transiently inflated but not destroyed by the passage of the CME. Much of the transition-region-temperature plasma in the CME-producing jets escaped from the Sun, whereas relatively more of the transition-region plasma in non-CME-producing jets fell back to the solar surface. Also, the CME-producing jets tended to be faster and longer-lasting than the non-CME-producing jets. Our observations imply that each jet and CME resulted from reconnection opening of twisted field that erupted from the jet base and that the erupting field did not become a plasmoid as previously envisioned for streamer-puff CMEs, but instead the jet-guiding streamer-base loop was blown out by the loop’s twist from the reconnection.« less

What Do High-Resolution EIT Waves Tell Us About CMEs?

NASA Technical Reports Server (NTRS)

Thompson, Barbara

2010-01-01

Although many studies have demonstrated that some coronal waves are not generated by corona) mass ejections, we have learned a great deal about the ability of corona) mass ejections to drive large-scale corona) waves, also called "EIT waves." We present new results based on EIT wave amplitude, timing, speed, and direction of propagation, with respect to their correlation with CME-related dimmings, speeds, locations and widths. Furthermore, we demonstrate the ability to correlate different aspects of EIT waves with some of the observed structure of CMEs observed in coronagraph data. Finally, we expand on the discussion of the types of wave modes that can be generated by a corona) mass ejection, and how these observations can serve as a diagnostic of the type of impulse a CME can deliver to the surrounding corona. These diagnostics are obtained by examining the motion of individual field lines, requiring high-resolution observations like those provided by TRACE and SDO/AIA.

A SOLAR CORONAL JET EVENT TRIGGERS A CORONAL MASS EJECTION

DOE Office of Scientific and Technical Information (OSTI.GOV)

Liu, Jiajia; Wang, Yuming; Shen, Chenglong

2015-11-10

In this paper, we present multi-point, multi-wavelength observations and analysis of a solar coronal jet and coronal mass ejection (CME) event. Employing the GCS model, we obtained the real (three-dimensional) heliocentric distance and direction of the CME and found it to propagate at a high speed of over 1000 km s{sup −1}. The jet erupted before the CME and shared the same source region. The temporal and spacial relationship between these two events lead us to the possibility that the jet triggered the CME and became its core. This scenario hold the promise of enriching our understanding of the triggeringmore » mechanism of CMEs and their relations to coronal large-scale jets. On the other hand, the magnetic field configuration of the source region observed by the Solar Dynamics Observatory (SDO)/HMI instrument along with the off-limb inverse Y-shaped configuration observed by SDO/AIA in the 171 Å passband provide the first detailed observation of the three-dimensional reconnection process of a large-scale jet as simulated in Pariat et al. The eruption process of the jet highlights the importance of filament-like material during the eruption of not only small-scale X-ray jets, but likely also of large-scale EUV jets. Based on our observations and analysis, we propose the most probable mechanism for the whole event, with a blob structure overlaying the three-dimensional structure of the jet, to describe the interaction between the jet and the CME.« less

Simulation of Homologous and Cannibalistic Coronal Mass Ejections produced by the Emergence of a Twisted Flux Rope into the Solar Corona

NASA Astrophysics Data System (ADS)

Chatterjee, Piyali; Fan, Yuhong

2013-11-01

We report the first results of a magnetohydrodynamic simulation of the development of a homologous sequence of three coronal mass ejections (CMEs) and demonstrate their so-called cannibalistic behavior. These CMEs originate from the repeated formations and partial eruptions of kink unstable flux ropes as a result of continued emergence of a twisted flux rope across the lower boundary into a pre-existing coronal potential arcade field. The simulation shows that a CME erupting into the open magnetic field created by a preceding CME has a higher speed. The second of the three successive CMEs is cannibalistic, catching up and merging with the first into a single fast CME before exiting the domain. All the CMEs including the leading merged CME, attained speeds of about 1000 km s-1 as they exit the domain. The reformation of a twisted flux rope after each CME eruption during the sustained flux emergence can naturally explain the X-ray observations of repeated reformations of sigmoids and "sigmoid-under-cusp" configurations at a low-coronal source of homologous CMEs.

A Small-Scale Flux Rope and its Associated CME and Shock.

NASA Astrophysics Data System (ADS)

Feng, L.; Ying, B.; Lu, L.; Zhang, J.

2016-12-01

A magnetic flux rope (MFR) is thought be a key ingredient of a coronal mass ejection (CME). It has been extensively explored after the Solar Dynamics Observatory (SDO) mission was launched. Previous studies are often concentrated on large-scale MFRs whose size are comparable to the active regions they reside. In this paper, we investigate the properties of a small-scale magnetic flux rope (SMFR) of a limb event observed by Atmospheric Imaging Assembly (AIA) . This SMFR originated from a very small and compact region at the edge of the active region and appeared mainly in the AIA 94 Å passband. It drove a coronal mass ejection (CME) and a type II burst was associated with the CME-driven shock. The type II burst started with a very high frequency. We obtain the compression ratio of the shock from the band splitting of the type II emissions and further derive the Alfvénic Mach number and the coronal magnetic field strength. On the other hand,we study the CME structure in LASCO coronagraph images and address its characteristics through measuring its mass and energy. Compared to the nature of the standard model of the CME, this CME triggered by the SMF are found to be different in some aspects.

The Width of a CME and the Source of the Driving Magnetic Explosion

NASA Technical Reports Server (NTRS)

Moore, R. L.; Sterling, A. C.; Suess, S. T.

2007-01-01

We show that the strength of the magnetic field in the area covered by the flare arcade following a CME-producing ejective solar eruption can be estimated from the final angular width of the CME in the outer corona and the final angular width of the flare arcade. We assume (1) the flux-rope plasmoid ejected from the flare site becomes the interior of the CME plasmoid, (2) in the outer corona the CME is roughly a "spherical plasmoid with legs" shaped like a light bulb, and (3) beyond some height in or below the outer corona the CME plasmoid is in lateral pressure balance with the surrounding magnetic field. The strength of the nearly radial magnetic field in the outer corona is estimated from the radial component of the interplanetary magnetic field measured by Ulysses. We apply this model to three well-observed CMEs that exploded from flare regions of extremely different size and magnetic setting. In each event, the estimated source-region field strength is appropriate for the magnetic setting of the flare. This agreement indicates via the model that CMEs (1) are propelled by the magnetic field of the CME plasmoid pushing against the surrounding magnetic field, and (2) can explode from flare regions that are laterally far offset from the radial path of the CME in the outer corona.

Three-dimensional global MHD modeling of a coronal mass ejection interacting with the solar wind

NASA Astrophysics Data System (ADS)

An, J.; Inoue, S.; Magara, T.; Lee, H.; Kang, J.; Hayashi, K.; Tanaka, T.; Den, M.

2013-12-01

We developed a three-dimensional (3D) magnetohydrodynamic (MHD) code to reproduce the structure of the solar wind, the propagation of a coronal mass ejection (CME), and the interaction between them. This MHD code is based on the finite volume method and total diminishing (TVD) scheme with an unstructured grid system. In particular, this grid system can avoid the singularity at the north and south poles and relax tight CFL conditions around the poles, both of which would arise in the spherical coordinate system (Tanaka 1995). In this study, we constructed a model of the solar wind driven by the physical values at 50 solar radii obtained from the MHD tomographic method (Hayashi et al. 2003) where an interplanetary scintillation (IPS) observational data is used. By comparing the result to the observational data obtained from the near-Earth OMNI dataset, we confirmed that our simulation reproduces the velocity, temperature and density profiles obtained from the near-Earth OMNI dataset. We then insert a spheromak-type CME (Kataoka et al. 2009) into our solar-wind model and investigate the propagation process of the CME interacting with the solar wind. In particular, we discuss how the magnetic twist accumulated in a CME affects the CME-solar wind interaction.

The Influence of Coronal Mass Ejections on the Mass-loss Rates of Hot-Jupiters

DOE Office of Scientific and Technical Information (OSTI.GOV)

Cherenkov, A.; Bisikalo, D.; Fossati, L.

Hot-Jupiters are subject to extreme radiation and plasma flows coming from their host stars. Past ultraviolet Hubble Space Telescope observations, supported by hydrodynamic models, confirmed that these factors lead to the formation of an extended envelope, part of which lies beyond the Roche lobe. We use gas-dynamic simulations to study the impact of time variations in the parameters of the stellar wind, namely that of coronal mass ejections (CMEs), on the envelope of the typical hot-Jupiter HD 209458b. We consider three CMEs characterized by different velocities and densities, taking their parameters from typical CMEs observed for the Sun. The perturbationsmore » in the ram-pressure of the stellar wind during the passage of each CME tear off most of the envelope that is located beyond the Roche lobe. This leads to a substantial increase of the mass-loss rates during the interaction with the CME. We find that the mass lost by the planet during the whole crossing of a CME is of ≈10{sup 15} g, regardless of the CME taken into consideration. We also find that over the course of 1 Gyr, the mass lost by the planet because of CME impacts is comparable to that lost because of high-energy stellar irradiation.« less

Theoretical basis for operational ensemble forecasting of coronal mass ejections

NASA Astrophysics Data System (ADS)

Pizzo, V. J.; de Koning, C.; Cash, M.; Millward, G.; Biesecker, D. A.; Puga, L.; Codrescu, M.; Odstrcil, D.

2015-10-01

We lay out the theoretical underpinnings for the application of the Wang-Sheeley-Arge-Enlil modeling system to ensemble forecasting of coronal mass ejections (CMEs) in an operational environment. In such models, there is no magnetic cloud component, so our results pertain only to CME front properties, such as transit time to Earth. Within this framework, we find no evidence that the propagation is chaotic, and therefore, CME forecasting calls for different tactics than employed for terrestrial weather or hurricane forecasting. We explore a broad range of CME cone inputs and ambient states to flesh out differing CME evolutionary behavior in the various dynamical domains (e.g., large, fast CMEs launched into a slow ambient, and the converse; plus numerous permutations in between). CME propagation in both uniform and highly structured ambient flows is considered to assess how much the solar wind background affects the CME front properties at 1 AU. Graphical and analytic tools pertinent to an ensemble approach are developed to enable uncertainties in forecasting CME impact at Earth to be realistically estimated. We discuss how uncertainties in CME pointing relative to the Sun-Earth line affects the reliability of a forecast and how glancing blows become an issue for CME off-points greater than about the half width of the estimated input CME. While the basic results appear consistent with established impressions of CME behavior, the next step is to use existing records of well-observed CMEs at both Sun and Earth to verify that real events appear to follow the systematic tendencies presented in this study.

Analysing spectroscopically the propagation of a CME from its source on the disk to its impact as it propagates outwards

NASA Astrophysics Data System (ADS)

Harra, Louise K.; Doschek, G. A.; Matthews, Sarah A.; De Pontieu, Bart; Long, David

We analyse a complex coronal mass ejection observed by Hinode, SDO and IRIS. SDO AIA shows that the eruption occurs between several active regions with flaring occurring in all of them. Hinode EIS observed one of the flaring active regions that shows a fast outwards propagation which is related to the CME lifting off. The eruption is then observed as it propagates away from the Sun, pushing the existing post-flare loops downwards as it goes. Spectroscopic observations are made during this time with IRIS measuring the impact that this CME front has as it pushes the loops downwards. Strong enhancements in the cool Mg II emission at these locations that show complex dynamics. We discuss these new observations in context of CME models.

MHD simulations of homologous and cannibalistic coronal mass ejections

NASA Astrophysics Data System (ADS)

Fan, Yuhong; Chatterjee, Piyali

2014-06-01

We present magneto-hydrodynamic simulations of the development of a homologous sequence of coronal mass ejections (CMEs) and demonstrate their so-called cannibalistic behavior. These CMEs originate from the repeated formations and partial eruptions of kink unstable flux ropes as a result of the continued emergence of a twisted flux rope across the lower boundary into a pre-existing coronal potential arcade field. The simulations show that a CME erupting into the open magnetic field created by a preceding CME has a higher speed, and therefore tends to be cannibalistic, catching up and merging with the preceding one into a single fast CME. All the CMEs attained speeds of about 1000 km/s as they exit the domain. The reformation of a twisted flux rope after each CME eruption during the sustained flux emergence can naturally explain the X-ray observations of repeated reformations of sigmoids and “sigmoid-under-cusp” configurations at a low-coronal source of homologous CMEs.

From SOHO to STEREO: Understanding Propagation of Coronal Mass Ejections

NASA Technical Reports Server (NTRS)

Gopalswamy, Natchimuthuk

2011-01-01

Direct comparison between coronal mass ejections (CMEs) from near the Sun and their solar wind counterparts became possible roughly a decade after the discovery of CMEs (Lindsay et aL 1999). This comparison revealed that fast CMEs decelerate and slow CMEs accelerate due to the interaction with the solar wind. Gopalswamy et al (2000) quantified this interaction as an interplanetary acceleration which is useful in predicting the arrival time and speed of CMEs at 1 AU. The interplanetary acceleration is essentially due to the aerodynamic drag between the CME and the solar wind because the propelling force and the solar gravity are effective only near the Sun. Combined remote-sensing and in situ observations from SOHO and Wind/ACE have helped us estimate the influence of the solar wind on the propagation of CMEs. However, these measurements have severe limitations because the remote sensed and in-situ observations correspond to different portions of the CME. Furthermore, the true speeds of Earth-directed CMEs cannot be measured accurately from a spacecraft located along the Sun-Earth line. There have been attempts to model the CME as a cone and get the space speed of the CME, which did improve the travel time predictions. Instruments on board the Solar Terrestrial Relations Observatory (STEREO) mission were able to provide observations of Earth-arriving CMEs without projection effects, while the same CMEs were observed at Sun-Earth L1 by Wind and ACE spacecraft. The quadrature between STEREO and L1 spacecraft presented an ideal situation to study the interplanetary evolution of CMEs and test earlier model results. The quadrature observations did improve the CME travel time predictions, but additional factors such as the unusually slow solar wind, CME cannibalism, and coronal-hole deflection need to be considered to reconcile the difference between observed and predicted travel times. This point is illustrated using the 2011 February 15 CME

INTERACTION BETWEEN TWO CORONAL MASS EJECTIONS IN THE 2013 MAY 22 LARGE SOLAR ENERGETIC PARTICLE EVENT

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ding, Liu-Guan; Xu, Fei; Gu, Bin

We investigate the eruption and interaction of two coronal mass ejections (CMEs) during the large 2013 May 22 solar energetic particle event using multiple spacecraft observations. Two CMEs, having similar propagation directions, were found to erupt from two nearby active regions (ARs), AR11748 and AR11745, at ∼08:48 UT and ∼13:25 UT, respectively. The second CME was faster than the first CME. Using the graduated cylindrical shell model, we reconstructed the propagation of these two CMEs and found that the leading edge of the second CME caught up with the trailing edge of the first CME at a height of ∼6 solar radii. Aftermore » about two hours, the leading edges of the two CMEs merged at a height of ∼20 solar radii. Type II solar radio bursts showed strong enhancement during this two hour period. Using the velocity dispersion method, we obtained the solar particle release (SPR) time and the path length for energetic electrons. Further assuming that energetic protons propagated along the same interplanetary magnetic field, we also obtained the SPR time for energetic protons, which were close to that of electrons. These release times agreed with the time when the second CME caught up with the trailing edge of the first CME, indicating that the CME-CME interaction (and shock-CME interaction) plays an important role in the process of particle acceleration in this event.« less

Radiation Belt response to the July 2017 Coronal Mass Ejection and the Interplanetary Shock

NASA Astrophysics Data System (ADS)

Kanekal, S. G.; Baker, D. N.; Jones, A. D.; Schiller, Q. A.; Sibeck, D. G.; Elkington, S. R.; Hoxie, V. C.; Jaynes, A. N.; Li, X.; Zhao, H.; Blake, J. B.; Claudepierre, S. G.; Fennell, J. F.; Turner, D. L.

2017-12-01

A coronal mass ejection that erupted on July 14, 2017 impacted the radiation belts on July 16, 2017 and resulted in a moderate geomagnetic storm. The immediate response of the energetic electrons to the interplanetary shock ahead of the CME, showed hock-induced energization as well as drift echoes in the L range of 4 to 5 . Increased electron fluxes were seen to energies up to 5 MeV as observed by the Relativistic Electron and Proton Telescope and the Magnetic Electron and Ion Sensors on board NASA's Van Allen Probes. We report on these observations, both immediately after the IP shock passage and the more gradual response to the CME. we discuss the observation in the context of electron dynamics in the terrestrial radiation belts.

How Interplanetary Scintillation Data Can Improve Modeling of Coronal Mass Ejection Propagation

NASA Astrophysics Data System (ADS)

Taktakishvili, A.; Mays, M. L.; Manoharan, P. K.; Rastaetter, L.; Kuznetsova, M. M.

2017-12-01

Coronal mass ejections (CMEs) can have a significant impact on the Earth's magnetosphere-ionosphere system and cause widespread anomalies for satellites from geosynchronous to low-Earth orbit and produce effects such as geomagnetically induced currents. At the NASA/GSFC Community Coordinated Modeling Center we have been using ensemble modeling of CMEs since 2012. In this presnetation we demonstrate that using of interplanetary scintillation (IPS) observations from the Ooty Radio Telescope facility in India can help to track CME propagaion and improve ensemble forecasting of CMEs. The observations of the solar wind density and velocity using IPS from hundreds of distant sources in ensemble modeling of CMEs can be a game-changing improvement of the current state of the art in CME forecasting.

An Unusual Coronal Mass Ejection: First Solar Wind Electron, Proton, Alpha Monitor (SWEPAM) Results from the Advanced Composition Explorer. Appendix 6

NASA Technical Reports Server (NTRS)

McComas, D. J.; Bame, S. J.; Barker, P. L.; Delapp, D. M.; Gosling, J. T.; Skoug, R. M.; Tokar, R. L.; Riley, P.; Feldman, W. C.; Santiago, E.

2001-01-01

This paper reports the first scientific results from the Solar Wind Electron Proton Alpha Monitor (SWEPAM) instrument on board the Advanced Composition Explorer (ACE) spacecraft. We analyzed a coronal mass ejection (CME) observed in the solar wind using data from early February, 1998. This event displayed several of the common signatures of CMEs, such as counterstreaming halo electrons and depressed ion and electron temperatures, as well as some unusual features. During a portion of the CME traversal, SWEPAM measured a very large helium to proton abundance ratio. Other heavy ions, with a set of ionization states consistent with normal (1 to 2x10(exp 6) K) coronal temperatures, were proportionately enhanced at this time. These observations suggest a source for at least some of the CME material, where heavy ions are initially concentrated relative to hydrogen and then accelerated up into the solar wind, independent of their mass and first ionization potential.

Interplanetary Propagation of Coronal Mass Ejections

NASA Technical Reports Server (NTRS)

Gopalswamy, Nat

2011-01-01

Although more than ten thousand coronal mass ejections (CMEs) are produced during each solar cycle at the Sun, only a small fraction hits the Earth. Only a small fraction of the Earth-directed CMEs ultimately arrive at Earth depending on their interaction with the solar wind and other large-scale structures such as coronal holes and CMEs. The interplanetary propagation is essentially controlled by the drag force because the propelling force and the solar gravity are significant only near the Sun. Combined remote-sensing and in situ observations have helped us estimate the influence of the solar wind on the propagation of CMEs. However, these measurements have severe limitations because the remote-sensed and in-situ observations correspond to different portions of the CME. Attempts to overcome this problem are made in two ways: the first is to model the CME and get the space speed of the CME, which can be compared with the in situ speed. The second method is to use stereoscopic observation so that the remote-sensed and in-situ observations make measurements on the Earth-arriving part of CMEs. The Solar Terrestrial Relations Observatory (STEREO) mission observed several such CMEs, which helped understand the interplanetary evolution of these CMEs and to test earlier model results. This paper discusses some of these issues and updates the CME/shock travel time estimates for a number of CMEs.

Mass-loss Rates from Coronal Mass Ejections: A Predictive Theoretical Model for Solar-type Stars

DOE Office of Scientific and Technical Information (OSTI.GOV)

Cranmer, Steven R.

Coronal mass ejections (CMEs) are eruptive events that cause a solar-type star to shed mass and magnetic flux. CMEs tend to occur together with flares, radio storms, and bursts of energetic particles. On the Sun, CME-related mass loss is roughly an order of magnitude less intense than that of the background solar wind. However, on other types of stars, CMEs have been proposed to carry away much more mass and energy than the time-steady wind. Earlier papers have used observed correlations between solar CMEs and flare energies, in combination with stellar flare observations, to estimate stellar CME rates. This papermore » sidesteps flares and attempts to calibrate a more fundamental correlation between surface-averaged magnetic fluxes and CME properties. For the Sun, there exists a power-law relationship between the magnetic filling factor and the CME kinetic energy flux, and it is generalized for use on other stars. An example prediction of the time evolution of wind/CME mass-loss rates for a solar-mass star is given. A key result is that for ages younger than about 1 Gyr (i.e., activity levels only slightly higher than the present-day Sun), the CME mass loss exceeds that of the time-steady wind. At younger ages, CMEs carry 10–100 times more mass than the wind, and such high rates may be powerful enough to dispel circumstellar disks and affect the habitability of nearby planets. The cumulative CME mass lost by the young Sun may have been as much as 1% of a solar mass.« less

Remote and In Situ Observations of an Unusual Earth-Directed Coronal Mass Ejection from Multiple Viewpoints

NASA Technical Reports Server (NTRS)

Nieves-Chinchilla, T.; Colaninno, R.; Vourlidas, A.; Szabo, A.; Lepping, R. P.; Boardsen, S. A.; Anderson, B. J.; Korth, H.

2012-01-01

During June 16-21, 2010, an Earth-directed Coronal Mass Ejection (CME) event was observed by instruments onboard STEREO, SOHO, MESSENGER and Wind. This event was the first direct detection of a rotating CME in the middle and outer corona. Here, we carry out a comprehensive analysis of the evolution of the CME in the interplanetary medium comparing in-situ and remote observations, with analytical models and three-dimensional reconstructions. In particular, we investigate the parallel and perpendicular cross section expansion of the CME from the corona through the heliosphere up to 1 AU. We use height-time measurements and the Gradual Cylindrical Shell (GCS) technique to model the imaging observations, remove the projection effects, and derive the 3-dimensional extent of the event. Then, we compare the results with in-situ analytical Magnetic Cloud (MC) models, and with geometrical predictions from past works. We nd that the parallel (along the propagation plane) cross section expansion agrees well with the in-situ model and with the Bothmer & Schwenn [1998] empirical relationship based on in-situ observations between 0.3 and 1 AU. Our results effectively extend this empirical relationship to about 5 solar radii. The expansion of the perpendicular diameter agrees very well with the in-situ results at MESSENGER ( 0:5 AU) but not at 1 AU. We also find a slightly different, from Bothmer & Schwenn [1998], empirical relationship for the perpendicular expansion. More importantly, we find no evidence that the CME undergoes a significant latitudinal over-expansion as it is commonly assumed

The CME Rate over Four Solar Cycles: Filling the Final Gap with MLSO MK3 Observations [1989-1996

NASA Astrophysics Data System (ADS)

St Cyr, O. C.; Flint, Q.; Quirk, C. A.; Burkepile, J.; Webb, D. F.; Lecinski, A. R.

2013-12-01

Coronal mass ejections (CMEs) were discovered in the early 1970's by the OSO-7 coronagraph, and large numbers were characterized for the first time by the Skylab ATM coronagraph. Since 1973 there has been only a single major gap in CME coverage in white light. Instruments that have contributed to estimates of the rate and properties of CMEs have included: Skylab ATM (1973-1974); Helios photometers (1974-1981); Solwind (1979-1985); SMM C/P (1980; 1984-1989); SOHO LASCO (1996-present); the Solar Mass Ejection Imager (SMEI, 2003-2011); and STEREO SECCHI (2006-present). We report here the first attempt to fill the 1989-1996 gap in the CME rate using the Mauna Loa Solar Observatory's MK3 K-coronameter. The MK3 instrument observed routinely several hours most days beginning in 1980 until it was upgraded to MK4 in 1998. MK3 CMEs detected from 1980-1989 were compared with Solwind and SMM and reported by St. Cyr et al. (1999). Since spaceborne instruments have more complete duty cycles than a groundbased instrument at a single location, we have 'calibrated' the MK3-derived CME rate from 1989 with the SMM C/P coronagraph, and from 1996 with the SOHO LASCO coronagraphs. CME rate calculations have been documented in Webb & Howard (1994), St. Cyr et al. (2000) and Robbrecht et al. (2009). Here we provide the preliminary CME rate calculation for 1989-1996 using the MLSO MK3 coronameter.

A soft x-ray coronal mass ejection occurred on solar limb on 1998 April 23

NASA Astrophysics Data System (ADS)

Cheng, X. J.

2001-11-01

Using some data observed with SXT/HXT aboard Yohkoh and the Nobeyama Radioheliograph (NoRH) on 1998 April 23, a comprehensive study on the soft X-ray coronal mass ejection (CME) on solar SE limb shows there were two magnetic dipole sources (MDSs), one magnetic capacity belt (MCB) between MDSs, one neutral current sheet (NCS) and only a few activation sources (ASs). During the MCB was changed by the ASs into a magnetic energy belt (MEB), the material and energy both concentrated to the NCS in the course of its formation. When the MDSs were put through by the MEB, the NCS formed and the CME occurred. The matter ejected not only from the NCS, but also from the whole MEB. The expanding loop of the CME had two footprints, they were just the MDSs. The head of the expanding loop always tended to the foot point of weak source. The locus of the head was just neutral line. From this, the position of NCS also could be determined.

Real­-Time Ensemble Forecasting of Coronal Mass Ejections Using the Wsa-Enlil+Cone Model

NASA Astrophysics Data System (ADS)

Mays, M. L.; Taktakishvili, A.; Pulkkinen, A. A.; Odstrcil, D.; MacNeice, P. J.; Rastaetter, L.; LaSota, J. A.

2014-12-01

Ensemble forecasting of coronal mass ejections (CMEs) provides significant information in that it provides an estimation of the spread or uncertainty in CME arrival time predictions. Real-time ensemble modeling of CME propagation is performed by forecasters at the Space Weather Research Center (SWRC) using the WSA-ENLIL+cone model available at the Community Coordinated Modeling Center (CCMC). To estimate the effect of uncertainties in determining CME input parameters on arrival time predictions, a distribution of n (routinely n=48) CME input parameter sets are generated using the CCMC Stereo CME Analysis Tool (StereoCAT) which employs geometrical triangulation techniques. These input parameters are used to perform n different simulations yielding an ensemble of solar wind parameters at various locations of interest, including a probability distribution of CME arrival times (for hits), and geomagnetic storm strength (for Earth-directed hits). We present the results of ensemble simulations for a total of 38 CME events in 2013-2014. For 28 of the ensemble runs containing hits, the observed CME arrival was within the range of ensemble arrival time predictions for 14 runs (half). The average arrival time prediction was computed for each of the 28 ensembles predicting hits and using the actual arrival time, an average absolute error of 10.0 hours (RMSE=11.4 hours) was found for all 28 ensembles, which is comparable to current forecasting errors. Some considerations for the accuracy of ensemble CME arrival time predictions include the importance of the initial distribution of CME input parameters, particularly the mean and spread. When the observed arrivals are not within the predicted range, this still allows the ruling out of prediction errors caused by tested CME input parameters. Prediction errors can also arise from ambient model parameters such as the accuracy of the solar wind background, and other limitations. Additionally the ensemble modeling sysem was used to complete a parametric event case study of the sensitivity of the CME arrival time prediction to free parameters for ambient solar wind model and CME. The parameter sensitivity study suggests future directions for the system, such as running ensembles using various magnetogram inputs to the WSA model.

Multi-viewpoint Coronal Mass Ejection Catalog Based on STEREO COR2 Observations

NASA Astrophysics Data System (ADS)

Vourlidas, Angelos; Balmaceda, Laura A.; Stenborg, Guillermo; Dal Lago, Alisson

2017-04-01

We present the first multi-viewpoint coronal mass ejection (CME) catalog. The events are identified visually in simultaneous total brightness observations from the twin SECCHI/COR2 coronagraphs on board the Solar Terrestrial Relations Observatory mission. The Multi-View CME Catalog differs from past catalogs in three key aspects: (1) all events between the two viewpoints are cross-linked, (2) each event is assigned a physics-motivated morphological classification (e.g., jet, wave, and flux rope), and (3) kinematic and geometric information is extracted semi-automatically via a supervised image segmentation algorithm. The database extends from the beginning of the COR2 synoptic program (2007 March) to the end of dual-viewpoint observations (2014 September). It contains 4473 unique events with 3358 events identified in both COR2s. Kinematic properties exist currently for 1747 events (26% of COR2-A events and 17% of COR2-B events). We examine several issues, made possible by this cross-linked CME database, including the role of projection on the perceived morphology of events, the missing CME rate, the existence of cool material in CMEs, the solar cycle dependence on CME rate, speeds and width, and the existence of flux rope within CMEs. We discuss the implications for past single-viewpoint studies and for Space Weather research. The database is publicly available on the web including all available measurements. We hope that it will become a useful resource for the community.

A CME-Driven Solar Wind Disturbance Observed at both Low and High Heliographic Latitudes

NASA Technical Reports Server (NTRS)

Gosling, J. T.; McComas, D. J.; Phillips, J. L.; Pizzo, V. J.; Goldstein, B. E.; Forsyth, R. J.; Lepping, R. P.

1995-01-01

A solar wind disturbance produced by a fast coronal mass ejection, CME, that departed from the Sun on February 20, 1994 was observed in the ecliptic plane at 1 AU by IMP 8 and at high heliographic latitudes at 3.53 AU by Ulysses. In the ecliptic the disturbance included a strong forward shock but no reverse shock, while at high latitudes the disturbance was bounded by a relatively weak forward-reverse shock pair. It is clear that the disturbance in the ecliptic plane was driven primarily by the relative speed between the CME and a slower ambient solar wind ahead, whereas at higher latitudes the disturbance was driven by expansion of the CME. The combined IMP 8 and Ulysses observations thus provide a graphic illustration of how a single fast CME can produce very different types of solar wind disturbances at low and high heliographic latitudes. Simple numerical simulations help explain observed differences at the two spacecraft.

Homologous and cannibalistic coronal mass ejections from twisted magnetic flux rope simulations

NASA Astrophysics Data System (ADS)

Chatterjee, Piyali; Fan, Yuhong

We present results from magnetohydrodynamic simulations of the development of homologous sequence of coronal mass ejections (CMEs) and demonstrate their so-called cannibalistic behavior. These CMEs originate from the repeated formations and partial eruptions of kink unstable flux ropes as a result of continued emergence of a twisted flux rope across the lower boundary into a pre-existing coronal potential arcade field. Our simulation shows that a CME erupting into the open magnetic field created by a preceding CME has a higher speed. The second of the three successive CMEs in one of the simulations is cannibalistic, catching up and merging with the first into a single fast CME before exiting the domain. All the CMEs including the leading merged CME, attained speeds of about 1000 km s-1 as they exit the domain. The reformation of a twisted flux rope after each CME eruption during the sustained flux emergence can naturally explain the X-ray observations of repeated reformations of sigmoids and "sigmoid-under-cusp" configurations at a low-coronal source of homologous CMEs. We also investigate the initiation mechanism and ejecta topology of these energetic CMEs as a function of the twist parameter of the flux rope.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Lu, Lei; Feng, Li; Liu, Siming

We present a detailed study of an Earth-directed coronal mass ejection (full-halo CME) event that happened on 2011 February 15, making use of white-light observations by three coronagraphs and radio observations by Wind /WAVES. We applied three different methods to reconstruct the propagation direction and traveling distance of the CME and its driven shock. We measured the kinematics of the CME leading edge from white-light images observed by Solar Terrestrial Relations Observatory ( STEREO ) A and B , tracked the CME-driven shock using the frequency drift observed by Wind /WAVES together with an interplanetary density model, and obtained themore » equivalent scattering centers of the CME by the polarization ratio (PR) method. For the first time, we applied the PR method to different features distinguished from LASCO/C2 polarimetric observations and calculated their projections onto white-light images observed by STEREO-A and STEREO-B . By combining the graduated cylindrical shell (GCS) forward modeling with the PR method, we proposed a new GCS-PR method to derive 3D parameters of a CME observed from a single perspective at Earth. Comparisons between different methods show a good degree of consistence in the derived 3D results.« less

CME Plasma Dynamics Using In-situ and Remote-sensing Observations

NASA Astrophysics Data System (ADS)

Kocher, Manan; Lepri, Susan; Landi, Enrico

2017-04-01

The thermal and kinetic energy of Coronal Mass Ejections [CMEs] can be best reconstructed if the plasma density, temperature and dynamics of each of their components are known. During periods of quadrature, we use a combination of in-situ measurements from ACE/SWICS and remote sensing observations from SDO/AIA and STEREO/EUVI to present several case studies of geo-effective halo-CMEs. We carry out density diagnostics and Differential Emission Measure [DEM] profile calculations to reconstruct a 3D picture of the CME plasma for the selected cases in the low solar corona. We then discuss these results in the context of models of CME initiation and release.

3D Modeling of CMEs observed with STEREO

NASA Astrophysics Data System (ADS)

Bosman, E.; Bothmer, V.

2012-04-01

From January 2007 until end of 2010, 565 typical large-scale coronal mass ejections (CMEs) have been identified in the SECCHI/COR2 synoptic movies of the STEREO Mission. A subset comprising 114 CME events, selected based on the CME's brightness appearance in the SECCHI/COR2 images, has been modeled through the Graduated Cylindrical Shell (GCS) Model developed by Thernisien et al. (2006). This study presents an overview of the GCS forward-modeling results and an interpretation of the CME characteristics in relationship to their solar source region properties and solar cycle appearances.

Recent VLA Measurements of CME-Induced Faraday Rotation

NASA Astrophysics Data System (ADS)

Kooi, Jason; Thomas, Najma; Guy, Michael; Spangler, Steven R.

2018-01-01

Observations of Faraday rotation, the change in polarization position angle of linearly polarized radiation as it propagates through a magnetized plasma, have been used for decades to determine the strength and structure of the coronal magnetic field and plasma density. Similarly, observations of Faraday rotation through a coronal mass ejection (CME) have the potential to improve our understanding of the CME’s plasma structure. We report recent results from simultaneous white-light coronagraph and radio observations made of a CME in July 2015. We made radio observations using the Karl G. Jansky Very Large Array (VLA) at 1 - 2 GHz frequencies of a set of cosmic radio sources through the solar corona at heliocentric distances that ranged between 8 - 23 solar radii. A unique aspect of these observations is that the CME occulted several of these radio sources and, therefore, our Faraday rotation measurements provide information on the plasma structure in different regions of the CME. We successfully measured CME-induced Faraday rotation along multiple lines of sight because we made special arrangements with the staff at the National Radio Astronomy Observatory to trigger VLA observations when a candidate CME appeared low in the corona in near real-time images from the Large Angle and Spectrometric Coronagraph (LASCO) C2 instrument.

Determining the full halo coronal mass ejection characteristics

NASA Astrophysics Data System (ADS)

Fainshtein, V. G.

2009-03-01

In this paper we determined the parameters of 45 full halo coronal mass ejections (HCMEs) for various modifications of their cone forms (“ice cream cone models”). We show that the CME determined characteristics depend significantly on the CME chosen form. We show that, regardless of the CME chosen form, the trajectory of practically all the considered HCMEs deviate from the radial direction to the Sun-to-Earth axis at the initial stage of their movement.

Magnetohydrodynamic simulations of the ejection of a magnetic flux rope

NASA Astrophysics Data System (ADS)

Pagano, P.; Mackay, D. H.; Poedts, S.

2013-06-01

Context. Coronal mass ejections (CME's) are one of the most violent phenomena found on the Sun. One model to explain their occurrence is the flux rope ejection model. In this model, magnetic flux ropes form slowly over time periods of days to weeks. They then lose equilibrium and are ejected from the solar corona over a few hours. The contrasting time scales of formation and ejection pose a serious problem for numerical simulations. Aims: We simulate the whole life span of a flux rope from slow formation to rapid ejection and investigate whether magnetic flux ropes formed from a continuous magnetic field distribution, during a quasi-static evolution, can erupt to produce a CME. Methods: To model the full life span of magnetic flux ropes we couple two models. The global non-linear force-free field (GNLFFF) evolution model is used to follow the quasi-static formation of a flux rope. The MHD code ARMVAC is used to simulate the production of a CME through the loss of equilibrium and ejection of this flux rope. Results: We show that the two distinct models may be successfully coupled and that the flux rope is ejected out of our simulation box, where the outer boundary is placed at 2.5 R⊙. The plasma expelled during the flux rope ejection travels outward at a speed of 100 km s-1, which is consistent with the observed speed of CMEs in the low corona. Conclusions: Our work shows that flux ropes formed in the GNLFFF can lead to the ejection of a mass loaded magnetic flux rope in full MHD simulations. Coupling the two distinct models opens up a new avenue of research to investigate phenomena where different phases of their evolution occur on drastically different time scales. Movies are available in electronic form at http://www.aanda.org

Three-dimensional stereoscopic analysis of a coronal mass ejection and comparison with UV spectroscopic data

DOE Office of Scientific and Technical Information (OSTI.GOV)

Susino, Roberto; Bemporad, Alessandro; Dolei, Sergio, E-mail: susino@oato.inaf.it, E-mail: sdo@oact.inaf.it

2014-07-20

A three-dimensional (3D) reconstruction of the 2007 May 20 partial-halo coronal mass ejection (CME) has been made using STEREO/EUVI and STEREO/COR1 coronagraphic images. The trajectory and kinematics of the erupting filament have been derived from Extreme Ultraviolet Imager (EUVI) image pairs with the 'tie-pointing' triangulation technique, while the polarization ratio technique has been applied to COR1 data to determine the average position and depth of the CME front along the line of sight. This 3D geometrical information has been combined for the first time with spectroscopic measurements of the O VI λλ1031.91, 1037.61 line profiles made with the Ultraviolet Coronagraphmore » Spectrometer (UVCS) on board the Solar and Heliospheric Observatory. Comparison between the prominence trajectory extrapolated at the altitude of UVCS observations and the core transit time measured from UVCS data made possible a firm identification of the CME core observed in white light and UV with the prominence plasma expelled during the CME. Results on the 3D structure of the CME front have been used to calculate synthetic spectral profiles of the O VI λ1031.91 line expected along the UVCS slit, in an attempt to reproduce the measured line widths. Observed line widths can be reproduced within the uncertainties only in the peripheral part of the CME front; at the front center, where the distance of the emitting plasma from the plane of the sky is greater, synthetic widths turn out to be ∼25% lower than the measured ones. This provides strong evidence of line broadening due to plasma heating mechanisms in addition to bulk expansion of the emitting volume.« less

Validation of the CME Geomagnetic Forecast Alerts Under the COMESEP Alert System

NASA Astrophysics Data System (ADS)

Dumbović, Mateja; Srivastava, Nandita; Rao, Yamini K.; Vršnak, Bojan; Devos, Andy; Rodriguez, Luciano

2017-08-01

Under the European Union 7th Framework Programme (EU FP7) project Coronal Mass Ejections and Solar Energetic Particles (COMESEP, http://comesep.aeronomy.be), an automated space weather alert system has been developed to forecast solar energetic particles (SEP) and coronal mass ejection (CME) risk levels at Earth. The COMESEP alert system uses the automated detection tool called Computer Aided CME Tracking (CACTus) to detect potentially threatening CMEs, a drag-based model (DBM) to predict their arrival, and a CME geoeffectiveness tool (CGFT) to predict their geomagnetic impact. Whenever CACTus detects a halo or partial halo CME and issues an alert, the DBM calculates its arrival time at Earth and the CGFT calculates its geomagnetic risk level. The geomagnetic risk level is calculated based on an estimation of the CME arrival probability and its likely geoeffectiveness, as well as an estimate of the geomagnetic storm duration. We present the evaluation of the CME risk level forecast with the COMESEP alert system based on a study of geoeffective CMEs observed during 2014. The validation of the forecast tool is made by comparing the forecasts with observations. In addition, we test the success rate of the automatic forecasts (without human intervention) against the forecasts with human intervention using advanced versions of the DBM and CGFT (independent tools available at the Hvar Observatory website, http://oh.geof.unizg.hr). The results indicate that the success rate of the forecast in its current form is unacceptably low for a realistic operation system. Human intervention improves the forecast, but the false-alarm rate remains unacceptably high. We discuss these results and their implications for possible improvement of the COMESEP alert system.

Constraints on particle density evolution within a CME at Mercury

NASA Astrophysics Data System (ADS)

Exner, W.; Liuzzo, L.; Heyner, D.; Feyerabend, M.; Motschmann, U. M.; Glassmeier, K. H.; Shiota, D.; Kusano, K.

2017-12-01

Mercury (RM=2440) is the closest orbiting planet around the Sun and is embedded in an intensive and highly varying solar wind.Mercury's intrinsic dipole with a southward magnetic moment is aligned with the rotation axis and has a northward offset of 0.2 RM.In-situ data from the MESSENGER spacecraft of the magnetic environment near Mercury indicate that a coronal mass ejection (CME) passed the planet on 8 May 2012. The data constrain the direction and magnitude of the CME magnetic field but no information on its particle density could be determined.We apply the hybrid (kinetic ions, electron fluid) code A.I.K.E.F. to study the interaction of Mercury's magnetosphere with the CME.We use MESSENGER magnetic field observations as well as simulation results to constrain the evolution of the particle density inside the CME.We show that within a 24-hour period the particle density within the CME had to vary between 1-100 cm-3 in order to explain MESSENGER magnetic field observations.

COMBINED MULTIPOINT REMOTE AND IN SITU OBSERVATIONS OF THE ASYMMETRIC EVOLUTION OF A FAST SOLAR CORONAL MASS EJECTION

DOE Office of Scientific and Technical Information (OSTI.GOV)

Rollett, T.; Möstl, C.; Temmer, M.

2014-07-20

We present an analysis of the fast coronal mass ejection (CME) of 2012  March 7, which was imaged by both STEREO spacecraft and observed in situ by MESSENGER, Venus Express, Wind, and Mars Express. Based on detected arrivals at four different positions in interplanetary space, it was possible to strongly constrain the kinematics and the shape of the ejection. Using the white-light heliospheric imagery from STEREO-A and B, we derived two different kinematical profiles for the CME by applying the novel constrained self-similar expansion method. In addition, we used a drag-based model to investigate the influence of the ambient solarmore » wind on the CME's propagation. We found that two preceding CMEs heading in different directions disturbed the overall shape of the CME and influenced its propagation behavior. While the Venus-directed segment underwent a gradual deceleration (from ∼2700 km s{sup –1} at 15 R {sub ☉} to ∼1500 km s{sup –1} at 154 R {sub ☉}), the Earth-directed part showed an abrupt retardation below 35 R {sub ☉} (from ∼1700 to ∼900 km s{sup –1}). After that, it was propagating with a quasi-constant speed in the wake of a preceding event. Our results highlight the importance of studies concerning the unequal evolution of CMEs. Forecasting can only be improved if conditions in the solar wind are properly taken into account and if attention is also paid to large events preceding the one being studied.« less

Morphological and kinematic evolution of three interacting coronal mass ejections of 2011 February 13-15

DOE Office of Scientific and Technical Information (OSTI.GOV)

Mishra, Wageesh; Srivastava, Nandita, E-mail: wageesh@prl.res.in

2014-10-10

During 2011 February 13-15, three Earth-directed coronal mass ejections (CMEs) launched in succession were recorded as limb CMEs by STEREO/SECCHI coronagraphs (COR). These CMEs provided an opportunity to study their geometrical and kinematic evolution from multiple vantage points. In this paper, we examine the differences in geometrical evolution of slow and fast CMEs during their propagation in the heliosphere. We also study their interaction and collision using STEREO/SECCHI COR and Heliospheric Imager (HI) observations. We have found evidence of interaction and collision between the CMEs of February 15 and 14 in the COR2 and HI1 field of view (FOV), respectively,more » while the CME of February 14 caught up with the CME of February 13 in the HI2 FOV. By estimating the true mass of these CMEs and using their pre- and post-collision dynamics, the momentum and energy exchange between them during the collision phase are studied. We classify the nature of the observed collision between the CMEs of February 14 and 15 as inelastic, reaching close to the elastic regime. Relating imaging observations with in situ WIND measurements at L1, we find that the CMEs move adjacent to each other after their collision in the heliosphere and are recognized as distinct structures in in situ observations. Our results highlight the significance of HI observations in studying CME-CME collision for the purpose of improved space weather forecasting.« less

Validation of the CME Geomagnetic forecast alerts under COMESEP alert system

NASA Astrophysics Data System (ADS)

Dumbovic, Mateja; Srivastava, Nandita; Khodia, Yamini; Vršnak, Bojan; Devos, Andy; Rodriguez, Luciano

2017-04-01

An automated space weather alert system has been developed under the EU FP7 project COMESEP (COronal Mass Ejections and Solar Energetic Particles: http://comesep.aeronomy.be) to forecast solar energetic particles (SEP) and coronal mass ejection (CME) risk levels at Earth. COMESEP alert system uses automated detection tool CACTus to detect potentially threatening CMEs, drag-based model (DBM) to predict their arrival and CME geo-effectiveness tool (CGFT) to predict their geomagnetic impact. Whenever CACTus detects a halo or partial halo CME and issues an alert, DBM calculates its arrival time at Earth and CGFT calculates its geomagnetic risk level. Geomagnetic risk level is calculated based on an estimation of the CME arrival probability and its likely geo-effectiveness, as well as an estimate of the geomagnetic-storm duration. We present the evaluation of the CME risk level forecast with COMESEP alert system based on a study of geo-effective CMEs observed during 2014. The validation of the forecast tool is done by comparing the forecasts with observations. In addition, we test the success rate of the automatic forecasts (without human intervention) against the forecasts with human intervention using advanced versions of DBM and CGFT (self standing tools available at Hvar Observatory website: http://oh.geof.unizg.hr). The results implicate that the success rate of the forecast is higher with human intervention and using more advanced tools. This work has received funding from the European Commission FP7 Project COMESEP (263252). We acknowledge the support of Croatian Science Foundation under the project 6212 „Solar and Stellar Variability".

Ensemble Modeling of the July 23, 2012 CME Event

NASA Astrophysics Data System (ADS)

Cash, M. D.; Biesecker, D. A.; Millward, G.; Arge, C. N.; Henney, C. J.

2013-12-01

On July 23, 2012 a large and very fast coronal mass ejection (CME) was observed by STEREO A. This CME was unusual in that the estimates of the speed of the CME ranged from 2125 km/s to 2780 km/s based on dividing the distance of STEREO A from the Sun by the transit time of the CME. Modeling of this CME event with the WSA-Enlil model has also suggested that a very fast speed is required in order to obtain the correct arrival time at 1 AU. We present a systematic study of parameter space for the July 23, 2012 CME event through an ensemble study using the WSA-Enlil model to predict the arrival time of the CME at STEREO A. We investigate how variations in the initial speed, angular width, and direction affect the predicted arrival time. We also explore how variations in the background solar wind influence CME arrival time by using varying ADAPT maps within our ensemble study. Factors involved in the fast transit time of this large CME are discussed and the optimal CME parameters are presented.

Automated detection of coronal mass ejections in three-dimensions using multi-viewpoint observations

NASA Astrophysics Data System (ADS)

Hutton, J.; Morgan, H.

2017-03-01

A new, automated method of detecting coronal mass ejections (CMEs) in three dimensions for the LASCO C2 and STEREO COR2 coronagraphs is presented. By triangulating isolated CME signal from the three coronagraphs over a sliding window of five hours, the most likely region through which CMEs pass at 5 R⊙ is identified. The centre and size of the region gives the most likely direction of propagation and approximate angular extent. The Automated CME Triangulation (ACT) method is tested extensively using a series of synthetic CME images created using a wireframe flux rope density model, and on a sample of real coronagraph data; including halo CMEs. The accuracy of the angular difference (σ) between the detection and true input of the synthetic CMEs is σ = 7.14°, and remains acceptable for a broad range of CME positions relative to the observer, the relative separation of the three observers and even through the loss of one coronagraph. For real data, the method gives results that compare well with the distribution of low coronal sources and results from another instrument and technique made further from the Sun. The true three dimension (3D)-corrected kinematics and mass/density are discussed. The results of the new method will be incorporated into the CORIMP database in the near future, enabling improved space weather diagnostics and forecasting.

Source Regions of the Type II Radio Burst Observed During a CME-CME Interaction on 2013 May 22

NASA Technical Reports Server (NTRS)

Makela, P.; Gopalswamy, N.; Reiner, M. J.; Akiyama, S.; Krupar, V.

2016-01-01

We report on our study of radio source regions during the type II radio burst on 2013 May 22 based on direction finding analysis of the Wind/WAVES and STEREO/WAVES (SWAVES) radio observations at decameter-hectometric wavelengths. The type II emission showed an enhancement that coincided with the interaction of two coronal mass ejections (CMEs) launched in sequence along closely spaced trajectories. The triangulation of the SWAVES source directions posited the ecliptic projections of the radio sources near the line connecting the Sun and the STEREO-A spacecraft. The WAVES and SWAVES source directions revealed shifts in the latitude of the radio source, indicating that the spatial location of the dominant source of the type II emission varies during the CME-CME interaction. The WAVES source directions close to 1MHz frequencies matched the location of the leading edge of the primary CME seen in the images of the LASCO/C3 coronagraph. This correspondence of spatial locations at both wavelengths confirms that the CME-CME interaction region is the source of the type II enhancement. Comparison of radio and white-light observations also showed that at lower frequencies scattering significantly affects radio wave propagation.

Tracking Energetics of a CME Core in the Low Solar Corona

NASA Astrophysics Data System (ADS)

Kocher, M.; Landi, E.; Lepri, S. T.

2017-12-01

In order to understand the processes that generate CMEs, and develop the ability to predict their evolution and geoeffectiveness, it is very important to determine how the plasma properties within coronal mass ejections (CME) evolve through their journey from the low corona through the solar environment. This study uses a combination of remote-sensing and in-situ observations of a filament eruption (that later formed the core of the CME) that left the Sun on August 4th, 2011 - shortly after an M-class flare. Separate absorption and emission diagnostic techniques are utilized to compute time-evolution estimates of the density and temperature of multiple plasma parcels within the filament using SDO/AIA EUV images. Twin STEREO spacecraft observations are used to estimate the height, speed, and acceleration of the CME at corresponding times. These observation-based densities, temperatures, and speeds allowed us to use the Michigan Ionization Code to compute the ionization history of this CME in the low solar corona. Along with the thermal and kinetic properties of this CME, we present a comparison with existing CME evolution models and draw inferences on its heating and acceleration.

LASCO White-Light Observations of Eruptive Current Sheets Trailing CMEs

NASA Astrophysics Data System (ADS)

Webb, David F.; Vourlidas, Angelos

2016-12-01

Many models of eruptive flares or coronal mass ejections (CMEs) involve formation of a current sheet connecting the ejecting CME flux rope with a magnetic loop arcade. However, there is very limited observational information on the properties and evolution of these structures, hindering progress in understanding eruptive activity from the Sun. In white-light images, narrow coaxial rays trailing the outward-moving CME have been interpreted as current sheets. Here, we undertake the most comprehensive statistical study of CME-rays to date. We use SOHO/LASCO data, which have a higher cadence, larger field of view, and better sensitivity than any previous coronagraph. We compare our results to a previous study of Solar Maximum Mission (SMM) CMEs, in 1984 - 1989, having candidate magnetic disconnection features at the CME base, about half of which were followed by coaxial bright rays. We examine all LASCO CMEs during two periods of minimum and maximum activity in Solar Cycle 23, resulting in many more events, ˜130 CME-rays, than during SMM. Important results include: The occurrence rate of the rays is ˜11 % of all CMEs during solar minimum, but decreases to ˜7 % at solar maximum; this is most likely related to the more complex coronal background. The rays appear on average 3 - 4 hours after the CME core, and are typically visible for three-fourths of a day. The mean observed current sheet length over the ray lifetime is ˜12 R_{⊙}, with the longest current sheet of 18.5 R_{⊙}. The mean CS growth rates are 188 km s^{-1} at minimum and 324 km s^{-1} at maximum. Outward-moving blobs within several rays, which are indicative of reconnection outflows, have average velocities of ˜350 km s^{-1} with small positive accelerations. A pre-existing streamer is blown out in most of the CME-ray events, but half of these are observed to reform within ˜1 day. The long lifetime and long lengths of the CME-rays challenge our current understanding of the evolution of the magnetic field in the aftermath of CMEs.

Formation of Radio Type II Bursts During a Multiple Coronal Mass Ejection Event

NASA Astrophysics Data System (ADS)

Al-Hamadani, Firas; Pohjolainen, Silja; Valtonen, Eino

2017-12-01

We study the solar event on 27 September 2001 that consisted of three consecutive coronal mass ejections (CMEs) originating from the same active region, which were associated with several periods of radio type II burst emission at decameter-hectometer (DH) wavelengths. Our analysis shows that the first radio burst originated from a low-density environment, formed in the wake of the first, slow CME. The frequency-drift of the burst suggests a low-speed burst driver, or that the shock was not propagating along the large density gradient. There is also evidence of band-splitting within this emission lane. The origin of the first shock remains unclear, as several alternative scenarios exist. The second shock showed separate periods of enhanced radio emission. This shock could have originated from a CME bow shock, caused by the fast and accelerating second or third CME. However, a shock at CME flanks is also possible, as the density depletion caused by the three CMEs would have affected the emission frequencies and hence the radio source heights could have been lower than usual. The last type II burst period showed enhanced emission in a wider bandwidth, which was most probably due to the CME-CME interaction. Only one shock that could reliably be associated with the investigated CMEs was observed to arrive near Earth.

Flux rope evolution in interplanetary coronal mass ejections: the 13 May 2005 event

NASA Astrophysics Data System (ADS)

Manchester, W. B., IV; van der Holst, B.; Lavraud, B.

2014-06-01

Coronal mass ejections (CMEs) are a dramatic manifestation of solar activity that release vast amounts of plasma into the heliosphere, and have many effects on the interplanetary medium and on planetary atmospheres, and are the major driver of space weather. CMEs occur with the formation and expulsion of large-scale magnetic flux ropes from the solar corona, which are routinely observed in interplanetary space. Simulating and predicting the structure and dynamics of these interplanetary CME magnetic fields are essential to the progress of heliospheric science and space weather prediction. We discuss the simulation of the 13 May 2005 CME event in which we follow the propagation of a flux rope from the solar corona to beyond Earth orbit. In simulating this event, we find that the magnetic flux rope reconnects with the interplanetary magnetic field, to evolve to an open configuration and later reconnects to reform a twisted structure sunward of the original rope. Observations of the 13 May 2005 CME magnetic field near Earth suggest that such a rearrangement of magnetic flux by reconnection may have occurred.

Testing the reliability of ice-cream cone model

NASA Astrophysics Data System (ADS)

Pan, Zonghao; Shen, Chenglong; Wang, Chuanbing; Liu, Kai; Xue, Xianghui; Wang, Yuming; Wang, Shui

2015-04-01

Coronal Mass Ejections (CME)'s properties are important to not only the physical scene itself but space-weather prediction. Several models (such as cone model, GCS model, and so on) have been raised to get rid of the projection effects within the properties observed by spacecraft. According to SOHO/ LASCO observations, we obtain the 'real' 3D parameters of all the FFHCMEs (front-side full halo Coronal Mass Ejections) within the 24th solar cycle till July 2012, by the ice-cream cone model. Considering that the method to obtain 3D parameters from the CME observations by multi-satellite and multi-angle has higher accuracy, we use the GCS model to obtain the real propagation parameters of these CMEs in 3D space and compare the results with which by ice-cream cone model. Then we could discuss the reliability of the ice-cream cone model.

Testing the reliability of ice-cream cone model

NASA Astrophysics Data System (ADS)

Pan, Z.; Shen, C.; Wang, Y.; Liu, K.

2013-12-01

Coronal Mass Ejections (CME)'s properties are important to not only the physical scene itself but spaceweather prediction. Several models(such as cone model, GCS model, and so on) have been raised to get rid of the projection effects within the properties observated by spacecraft. According to SOHO/ LASCO observations, we obtain the 'real' 3D parameters of 33 FFHCMEs (front-side full halo Coronal Mass Ejections) within the 24th solar cycle by the ice-cream cone model. Considering that the method to obtain 3D parameters from the CME observations by multi-satellite and multi-angle has higher accuracy, we use the GCS model to obtain the real propagation parameters of these CMEs in 3D space and compare the results with which by ice-cream cone model. It was demonstrated that the correlation coefficient for the speeds by using these both methods is 0.97.

A Brief History of CME Science

NASA Technical Reports Server (NTRS)

Alexander, David; Richardson, Ian G.; Zurbuchen, Thomas H.

2006-01-01

We present here a brief summary of the rich heritage of observational and theoretical research leading to the development of our current understanding of the initiation, structure, and evolution of Coronal Mass Ejections.

Kinematic and Energetic Properties of the 2012 March 12 Polar Coronal Mass Ejection

NASA Technical Reports Server (NTRS)

Gopalswamy, N.; Yashiro, Seiji; Akiyama, S.

2015-01-01

We report on the energetics of the 2012 March 12 polar coronal mass ejection (CME) originating from a southern latitude of approximately 60deg. The polar CME is similar to low-latitude (LL) CMEs in almost all respects: three-part morphology; post-eruption arcade (PEA), CME, and filament kinematics; CME mass and kinetic energy; and the relative thermal energy content of the PEA. From polarized brightness images, we estimate the CME mass, which is close to the average mass of LL CMEs. The CME kinetic energy (3.3 × 10(sup 30) erg) is also typical of the general population of CMEs. From photospheric magnetograms, we estimate the free energy (1.8 × 10(sup 31) erg) in the polar crown source region, which we find is sufficient to power the CME and the PEA. About 19% of the free energy went into the CME kinetic energy. We compute the thermal energy content of the PEA (2.3 × 10(sup 29) erg) and find it to be a small fraction (6.8%) of the CME kinetic energy. This fraction is remarkably similar to that in active region CMEs associated with major flares. We also show that the 2012 March 12 is one among scores of polar CMEs observed during the maximum phase of cycle 24. The cycle 24 polar crown prominence eruptions have the same rate of association with CMEs as those from LLs. This investigation supports the view that all CMEs are magnetically propelled from closed field regions, irrespective of their location on the Sun (polar crown filament regions, quiescent filament regions, or active regions).

KINEMATIC AND ENERGETIC PROPERTIES OF THE 2012 MARCH 12 POLAR CORONAL MASS EJECTION

DOE Office of Scientific and Technical Information (OSTI.GOV)

Gopalswamy, N.; Yashiro, S.; Akiyama, S., E-mail: nat.gopalswamy@nasa.gov

2015-08-10

We report on the energetics of the 2012 March 12 polar coronal mass ejection (CME) originating from a southern latitude of ∼60°. The polar CME is similar to low-latitude (LL) CMEs in almost all respects: three-part morphology; post-eruption arcade (PEA), CME, and filament kinematics; CME mass and kinetic energy; and the relative thermal energy content of the PEA. From polarized brightness images, we estimate the CME mass, which is close to the average mass of LL CMEs. The CME kinetic energy (3.3 × 10{sup 30} erg) is also typical of the general population of CMEs. From photospheric magnetograms, we estimatemore » the free energy (1.8 × 10{sup 31} erg) in the polar crown source region, which we find is sufficient to power the CME and the PEA. About 19% of the free energy went into the CME kinetic energy. We compute the thermal energy content of the PEA (2.3 × 10{sup 29} erg) and find it to be a small fraction (6.8%) of the CME kinetic energy. This fraction is remarkably similar to that in active region CMEs associated with major flares. We also show that the 2012 March 12 is one among scores of polar CMEs observed during the maximum phase of cycle 24. The cycle 24 polar crown prominence eruptions have the same rate of association with CMEs as those from LLs. This investigation supports the view that all CMEs are magnetically propelled from closed field regions, irrespective of their location on the Sun (polar crown filament regions, quiescent filament regions, or active regions)« less

Three-Dimensional Properties of Coronal Mass Ejections from STEREO/SECCHI Observations

NASA Astrophysics Data System (ADS)

Bosman, E.; Bothmer, V.; Nisticò, G.; Vourlidas, A.; Howard, R. A.; Davies, J. A.

2012-11-01

We identify 565 coronal mass ejections (CMEs) between January 2007 and December 2010 in observations from the twin STEREO/SECCHI/COR2 coronagraphs aboard the STEREO mission. Our list is in full agreement with the corresponding SOHO/LASCO CME Catalog (http://cdaw.gsfc.nasa.gov/CME_list/) for events with angular widths of 45∘ and up. The monthly event rates behave similarly to sunspot rates showing a three- to fourfold rise between September 2009 and March 2010. We select 51 events with well-defined white-light structure and model them as three-dimensional (3D) flux ropes using a forward-modeling technique developed by Thernisien, Howard and Vourlidas (Astrophys. J. 652, 763 - 773, 2006). We derive their 3D properties and identify their source regions. We find that the majority of the CME flux ropes (82 %) lie within 30∘ of the solar equator. Also, 82 % of the events are displaced from their source region, to a lower latitude, by 25∘ or less. These findings provide strong support for the deflection of CMEs towards the solar equator reported in earlier observations, e.g. by Cremades and Bothmer ( Astron. Astrophys. 422, 307 - 322, 2004).

Origin and Ion Charge State Evolution of Solar Wind Transients during 4 - 7 August 2011

NASA Astrophysics Data System (ADS)

Rodkin, D.; Goryaev, F.; Pagano, P.; Gibb, G.; Slemzin, V.; Shugay, Y.; Veselovsky, I.; Mackay, D. H.

2017-07-01

We present a study of the complex event consisting of several solar wind transients detected by the Advanced Composition Explorer (ACE) on 4 - 7 August 2011, which caused a geomagnetic storm with Dst=-110 nT. The supposed coronal sources, three flares and coronal mass ejections (CMEs), occurred on 2 - 4 August 2011 in active region (AR) 11261. To investigate the solar origin and formation of these transients, we study the kinematic and thermodynamic properties of the expanding coronal structures using the Solar Dynamics Observatory/Atmospheric Imaging Assembly (SDO/AIA) EUV images and differential emission measure (DEM) diagnostics. The Helioseismic and Magnetic Imager (HMI) magnetic field maps were used as the input data for the 3D magnetohydrodynamic (MHD) model to describe the flux rope ejection (Pagano, Mackay, and Poedts, 2013b). We characterize the early phase of the flux rope ejection in the corona, where the usual three-component CME structure formed. The flux rope was ejected with a speed of about 200 km s^{-1} to the height of 0.25 R_{⊙}. The kinematics of the modeled CME front agrees well with the Solar Terrestrial Relations Observatory (STEREO) EUV measurements. Using the results of the plasma diagnostics and MHD modeling, we calculate the ion charge ratios of carbon and oxygen as well as the mean charge state of iron ions of the 2 August 2011 CME, taking into account the processes of heating, cooling, expansion, ionization, and recombination of the moving plasma in the corona up to the frozen-in region. We estimate a probable heating rate of the CME plasma in the low corona by matching the calculated ion composition parameters of the CME with those measured in situ for the solar wind transients. We also consider the similarities and discrepancies between the results of the MHD simulation and the observations.

A Stealth CME Bracketed between Slow and Fast Wind Producing Unexpected Geoeffectiveness

NASA Astrophysics Data System (ADS)

He, Wen; Liu, Ying D.; Hu, Huidong; Wang, Rui; Zhao, Xiaowei

2018-06-01

We investigate how a weak coronal mass ejection (CME) launched on 2016 October 8 without obvious signatures in the low corona produced a relatively intense geomagnetic storm. Remote sensing observations from SDO, STEREO, and SOHO and in situ measurements from Wind are employed to track the CME from the Sun to the Earth. Using a graduated cylindrical shell model, we estimate the propagation direction and the morphology of the CME near the Sun. CME kinematics are determined from the wide-angle imaging observations of STEREO A and are used to predict the CME arrival time and speed at the Earth. We compare ENLIL MHD simulation results with in situ measurements to illustrate the background solar wind where the CME was propagating. We also apply a Grad–Shafranov technique to reconstruct the flux-rope structure from in situ measurements in order to understand the geoeffectiveness associated with the CME magnetic field structure. Key results are obtained concerning how a weak CME can generate a relatively intense geomagnetic storm: (1) there were coronal holes at low latitudes, which could produce high speed streams (HSSs) to interact with the CME in interplanetary space; (2) the CME was bracketed between a slow wind ahead and an HSS behind, which enhanced the southward magnetic field inside the CME and gave rise to the unexpected geomagnetic storm.

THE HELIOCENTRIC DISTANCE WHERE THE DEFLECTIONS AND ROTATIONS OF SOLAR CORONAL MASS EJECTIONS OCCUR

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kay, C.; Opher, M., E-mail: ckay@bu.edu

2015-10-01

Understanding the trajectory of a coronal mass ejection (CME), including any deflection from a radial path, and the orientation of its magnetic field is essential for space weather predictions. Kay et al. developed a model, Forecasting a CME’s Altered Trajectory (ForeCAT), of CME deflections and rotation due to magnetic forces, not including the effects of reconnection. ForeCAT is able to reproduce the deflection of observed CMEs. The deflecting CMEs tend to show a rapid increase of their angular momentum close to the Sun, followed by little to no increase at farther distances. Here we quantify the distance at which themore » CME deflection is “determined,” which we define as the distance after which the background solar wind has negligible influence on the total deflection. We consider a wide range in CME masses and radial speeds and determine that the deflection and rotation of these CMEs can be well-described by assuming they propagate with constant angular momentum beyond 10 R{sub ⊙}. The assumption of constant angular momentum beyond 10 R{sub ⊙} yields underestimates of the total deflection at 1 AU of only 1%–5% and underestimates of the rotation of 10%. Since the deflection from magnetic forces is determined by 10 R{sub ⊙}, non-magnetic forces must be responsible for any observed interplanetary deflections or rotations where the CME has increasing angular momentum.« less

MLSO Mark III K-Coronameter Observations of the CME Rate from 1989-1996

NASA Technical Reports Server (NTRS)

St Cyr, O. C.; Flint, Q. A.; Xie, H.; Webb, D. F.; Burkepile, J. T.; Lecinski, A. R.; Quirk, C.; Stanger, A. L.

2015-01-01

We report here an attempt to fill the 1990-1995 gap in the CME (coronal mass ejection) rate using the Mauna Loa Solar Observatory (MLSO)'s Mark III (Mk3) K-coronameter. The Mk3 instrument observed routinely several hours most days beginning in 1980 until it was upgraded to Mk4 in 1999. We describe the statistical properties of the CMEs detected during 1989-1996, and we determine a CME rate for each of those years. Since spaceborne coronagraphs have more complete duty cycles than a ground-based instrument at a single location, we compare the Mk3-derived CME rate from 1989 with the SMM C/P (Solar Maximum Mission Coronagraph/Polarimeter) coronagraph, and from 1996 with the SOHO (Solar and Hellospheric Observatory) LASCO (Large Angle and Spectrometric COronagraph) coronagraphs.

Real-time Ensemble Forecasting of Coronal Mass Ejections using the WSA-ENLIL+Cone Model

NASA Astrophysics Data System (ADS)

Mays, M. L.; Taktakishvili, A.; Pulkkinen, A. A.; MacNeice, P. J.; Rastaetter, L.; Kuznetsova, M. M.; Odstrcil, D.

2013-12-01

Ensemble forecasting of coronal mass ejections (CMEs) provides significant information in that it provides an estimation of the spread or uncertainty in CME arrival time predictions due to uncertainties in determining CME input parameters. Ensemble modeling of CME propagation in the heliosphere is performed by forecasters at the Space Weather Research Center (SWRC) using the WSA-ENLIL cone model available at the Community Coordinated Modeling Center (CCMC). SWRC is an in-house research-based operations team at the CCMC which provides interplanetary space weather forecasting for NASA's robotic missions and performs real-time model validation. A distribution of n (routinely n=48) CME input parameters are generated using the CCMC Stereo CME Analysis Tool (StereoCAT) which employs geometrical triangulation techniques. These input parameters are used to perform n different simulations yielding an ensemble of solar wind parameters at various locations of interest (satellites or planets), including a probability distribution of CME shock arrival times (for hits), and geomagnetic storm strength (for Earth-directed hits). Ensemble simulations have been performed experimentally in real-time at the CCMC since January 2013. We present the results of ensemble simulations for a total of 15 CME events, 10 of which were performed in real-time. The observed CME arrival was within the range of ensemble arrival time predictions for 5 out of the 12 ensemble runs containing hits. The average arrival time prediction was computed for each of the twelve ensembles predicting hits and using the actual arrival time an average absolute error of 8.20 hours was found for all twelve ensembles, which is comparable to current forecasting errors. Some considerations for the accuracy of ensemble CME arrival time predictions include the importance of the initial distribution of CME input parameters, particularly the mean and spread. When the observed arrivals are not within the predicted range, this still allows the ruling out of prediction errors caused by tested CME input parameters. Prediction errors can also arise from ambient model parameters such as the accuracy of the solar wind background, and other limitations. Additionally the ensemble modeling setup was used to complete a parametric event case study of the sensitivity of the CME arrival time prediction to free parameters for ambient solar wind model and CME.

The Search for Transient Mass Loss Events on Active Stars and Their Impacts

NASA Astrophysics Data System (ADS)

Crosley, Michael K.

2018-01-01

The conditions that determine the potential habitability of exoplanets are very diverse and still poorly understood. Magnetic eruptive events, such as flares and coronal mass ejections (CME's) are one such concern. Stellar flares are routinely observed and on cool stars but clear signatures of stellar CME's have been less forthcoming. CME’s are geoeffective and contribute to space weather. Stellar coronal mass ejections remain experimentally unconstrained, unlike the stellar flare counterpart which are observed ubiquitously across the electromagnetic spectrum. Low frequency radio bursts in the form of a type II burst offer the best means of identifying and constraining the rate and properties of stellar CME’s. CME properties can be further constrained and solar scaling relationships tested by simultaneously preforming flare observations. The interpretation for the multi-wavelength analysis of type II events and their associated flares is tested by fully constrained solar observations. There we find that velocity measurements are typically accurate to within a factor of two and that mass constraints are accurate to within an order of magnitude. We take these lessons and apply them to observations of the nearby, active M dwarf stars YZ Cmi and EQ Peg. These stars have the advantage of being well observed and constrained. Their well documented high flare activity is expected to be accompanied with high CME activity. They have been shown to have low frequency radio bursts in the past, and their constrained coronal properties allows us to extract the information required to interpret the type II burst. We report on 15 hours of Low Frequency Array (10-190 MHz) observations of YZ Cmi and to 64 hours of EQ Peg observations at the Jansky Very Large Array (230-470 MHz), 20 hours of which were observed simultaneously for flares at the Apache Point Observatory. During this time, solar scaling relationships tells us that ~70 large flares should have been produced which would be associated to a corresponding CME as well. From our results we can constraint event properties, detection limits, CME models, and atmospheric models.

SOHO Observations of a Coronal Mass Ejection

NASA Astrophysics Data System (ADS)

Akmal, Arya; Raymond, John C.; Vourlidas, Angelos; Thompson, Barbara; Ciaravella, A.; Ko, Y.-K.; Uzzo, M.; Wu, R.

2001-06-01

We describe a coronal mass ejection (CME) observed on 1999 April 23 by the Ultraviolet Coronagraph Spectrometer (UVCS), the Extreme-Ultraviolet Imaging Telescope (EIT), and the Large-Angle and Spectrometric Coronagraphs (LASCO) aboard the Solar and Heliospheric Observatory (SOHO). In addition to the O VI and C III lines typical of UVCS spectra of CMEs, this 480 km s-1 CME exhibits the forbidden and intercombination lines of O V at λλ1213.8 and 1218.4. The relative intensities of the O V lines represent an accurate electron density diagnostic not generally available at 3.5 Rsolar. By combining the density with the column density derived from LASCO, we obtain the emission measure of the ejected gas. With the help of models of the temperature and time-dependent ionization state of the expanding gas, we determine a range of heating rates required to account for the UV emission lines. The total thermal energy deposited as the gas travels to 3.5 Rsolar is comparable to the kinetic and gravitational potential energies. We note a core of colder material radiating in C III, surrounded by hotter material radiating in the O V and O VI lines. This concentration of the coolest material into small regions may be a common feature of CMEs. This event thus represents a unique opportunity to describe the morphology of a CME, and to characterize its plasma parameters.

Verification of real-time WSA-ENLIL+Cone simulations of CME arrival-time at the CCMC from 2010 to 2016

NASA Astrophysics Data System (ADS)

Wold, Alexandra M.; Mays, M. Leila; Taktakishvili, Aleksandre; Jian, Lan K.; Odstrcil, Dusan; MacNeice, Peter

2018-03-01

The Wang-Sheeley-Arge (WSA)-ENLIL+Cone model is used extensively in space weather operations world-wide to model coronal mass ejection (CME) propagation. As such, it is important to assess its performance. We present validation results of the WSA-ENLIL+Cone model installed at the Community Coordinated Modeling Center (CCMC) and executed in real-time by the CCMC space weather team. CCMC uses the WSA-ENLIL+Cone model to predict CME arrivals at NASA missions throughout the inner heliosphere. In this work we compare model predicted CME arrival-times to in situ interplanetary coronal mass ejection leading edge measurements at Solar TErrestrial RElations Observatory-Ahead (STEREO-A), Solar TErrestrial RElations Observatory-Behind (STEREO-B), and Earth (Wind and ACE) for simulations completed between March 2010 and December 2016 (over 1,800 CMEs). We report hit, miss, false alarm, and correct rejection statistics for all three locations. For all predicted CME arrivals, the hit rate is 0.5, and the false alarm rate is 0.1. For the 273 events where the CME was predicted to arrive at Earth, STEREO-A, or STEREO-B, and was actually observed (hit event), the mean absolute arrival-time prediction error was 10.4 ± 0.9 h, with a tendency to early prediction error of -4.0 h. We show the dependence of the arrival-time error on CME input parameters. We also explore the impact of the multi-spacecraft observations used to initialize the model CME inputs by comparing model verification results before and after the STEREO-B communication loss (since September 2014) and STEREO-A sidelobe operations (August 2014-December 2015). There is an increase of 1.7 h in the CME arrival time error during single, or limited two-viewpoint periods, compared to the three-spacecraft viewpoint period. This trend would apply to a future space weather mission at L5 or L4 as another coronagraph viewpoint to reduce CME arrival time errors compared to a single L1 viewpoint.

The three-dimensional angular widths of CMEs and their relations to the source regions

NASA Astrophysics Data System (ADS)

Zhao, X.; Feng, X. S.

2017-12-01

The angular width of a coronal mass ejection (CME) is an important factor to determine whether the corresponding interplanetary CME (ICME) and its preceding shock will reach our Earth. However, very few studies are involved to study the decisive factors of the CME's angular width. In this study, we use the three-dimensional (3D) angular width of CMEs obtained from the Graduated Cylindrical Shell (GCS) model based on observations of Solar Terrestrial Relations Observatory (STEREO) to study the relations between the CME's 3D width and characteristics of the CME's source region. We find that for the CMEs produced by active regions (ARs), the CME width has some correlations with the AR's area and flux, but these correlations are not strong. The magnetic flux contained in the CME seems to come from only part of the AR's total flux. For the CMEs produced by flare regions, the correlations between the CME angular width and the flare region's area and flux are strong. The magnetic flux within those CMEs seems to totally (even not enough) come from the flare region. Our findings prefer to support that the CME's 3D angular width can be generally estimated based on observations of Solar Dynamics Observatory (SDO) for its source region instead of the observations from coronagraphs onboard Solar and Heliospheric Observatory (SOHO) and STEREO.

RADIAL FLOW PATTERN OF A SLOW CORONAL MASS EJECTION

DOE Office of Scientific and Technical Information (OSTI.GOV)

Feng, Li; Gan, Weiqun, E-mail: lfeng@pmo.ac.cn; Inhester, Bernd

2015-06-01

Height–time plots of the leading edge of coronal mass ejections (CMEs) have often been used to study CME kinematics. We propose a new method to analyze the CME kinematics in more detail by determining the radial mass transport process throughout the entire CME. Thus, our method is able to estimate not only the speed of the CME front but also the radial flow speed inside the CME. We have applied this method to a slow CME with an average leading edge speed of about 480 km s{sup −1}. In the Lagrangian frame, the speeds of the individual CME mass elementsmore » stay almost constant within 2 and 15 R{sub S}, the range over which we analyzed the CME. Hence, we have no evidence of net radial forces acting on parts of the CME in this range or of a pile up of mass ahead of the CME. We find evidence that the leading edge trajectory obtained by tie-pointing may gradually lag behind the Lagrangian front-side trajectories derived from our analysis. Our results also allow a much more precise estimate of the CME energy. Compared with conventional estimates using the CME total mass and leading edge motion, we find that the latter may overestimate the kinetic energy and the gravitational potential energy.« less

Role of Ambient Solar Wind Conditions in CME evolution (P21)

NASA Astrophysics Data System (ADS)

Jadav, R.; Jadeja, A. K.; Iyer, K. N.

2006-11-01

ipsraj@yahoo.com Solar events are mainly responsible for producing storms at the Earth. Coronal Mass Ejection (CME) is a major cause for this. In this paper, Coronal Mass Ejections occurred during 1998-2004 are studied. Ambient solar wind does play some role in determining the effect of a CME. The effects produced at the Earth during the period 1999 2004 are considered and an attempt has been made to understand the role of ambient solar wind. This is to draw some conclusion about how some of the events become geo- effective.

A Sun-to-Earth Analysis of Magnetic Helicity of the 2013 March 17–18 Interplanetary Coronal Mass Ejection

NASA Astrophysics Data System (ADS)

Pal, Sanchita; Gopalswamy, Nat; Nandy, Dibyendu; Akiyama, Sachiko; Yashiro, Seiji; Makela, Pertti; Xie, Hong

2017-12-01

We compare the magnetic helicity in the 2013 March 17–18 interplanetary coronal mass ejection (ICME) flux rope at 1 au and in its solar counterpart. The progenitor coronal mass ejection (CME) erupted on 2013 March 15 from NOAA active region 11692 and is associated with an M1.1 flare. We derive the source region reconnection flux using the post-eruption arcade (PEA) method that uses the photospheric magnetogram and the area under the PEA. The geometrical properties of the near-Sun flux rope is obtained by forward-modeling of white-light CME observations. Combining the geometrical properties and the reconnection flux, we extract the magnetic properties of the CME flux rope. We derive the magnetic helicity of the flux rope using its magnetic and geometric properties obtained near the Sun and at 1 au. We use a constant-α force-free cylindrical flux rope model fit to the in situ observations in order to derive the magnetic and geometric information of the 1 au ICME. We find a good correspondence in both amplitude and sign of the helicity between the ICME and the CME, assuming a semi-circular (half torus) ICME flux rope with a length of π au. We find that about 83% of the total flux rope helicity at 1 au is injected by the magnetic reconnection in the low corona. We discuss the effect of assuming flux rope length in the derived value of the magnetic helicity. This study connecting the helicity of magnetic flux ropes through the Sun–Earth system has important implications for the origin of helicity in the interplanetary medium and the topology of ICME flux ropes at 1 au and hence their space weather consequences.

Coronal Current Sheet Evolution in the Aftermath of a CME

NASA Technical Reports Server (NTRS)

Bemporad, A.; Poletto, G.; Suess, S. T.; Ko, Y.-K.; Schwadron, N. A.; Elliott, H. A.; Raymond, J. C.

2005-01-01

We report on SOHO-UVCS observations of coronal restructuring following a Coronal Mass Ejection (CME) on November 26, 2002, at the time of a SOHO-Ulysses quadrature campaign. Starting about 3 hours after the CME, which was directed towards Ulysses, UVCS began taking spectra at 1.7 solar radii, covering emission from both cool and hot plasma. Observations continued, with occasional gaps, for more than 2 days. Emission in the 974.8 Angstrom line of [Fe XVIII], indicating temperatures above 6x10(6) K, was observed throughout the campaign in a spatially limited location. Comparison with EIT images shows the [Fe XVIII] emission to overlie a growing post-flare loop system formed in the aftermath of the CME. The emission most likely originates in a current sheet overlying the arcade. Analysis of the [Fe XVIII] emission allows us to infer the evolution of physical parameters in the current sheet over the entire span of our observations: in particular, we give the temperature vs. time in the current sheet and estimate the density. Ulysses was directly above the location of the CME and intercepted the ejecta. High ionization state Fe was detected by SWICS throughout the magnetic cloud associated with the CME, although the rapid temporal variation suggests bursty, rather than smooth, reconnection in the coronal current sheet. Both the remote and in situ observations are compared with predictions of theoretical CME models.

Current Sheet Evolution in the Aftermath of a CME Event

NASA Technical Reports Server (NTRS)

Bemporad, A.; Poletto, G.; Suess, S. T.; Ko, Y.-K.; Schwadron, N. A.; Elliott, H. A.; Raymond, J. C.

2005-01-01

We report on SOHO-UVCS observations of the coronal restructuring following a Coronal Mass Ejection (CME) on November 26,2002, at the time of a SOHO-Ulysses quadrature campaign. Starting about 3 hours after a CME in the NW quadrant, UVCS began taking spectra at 1.7 solar radius, covering emission from both cool and hot plasma. Observations continued, with occasional gaps, for more than 2 days. Emission in the 974.8 Angstrom line of [Fe XVIII], indicating temperatures above 6 x 10(exp 6) K, was observed throughout the campaign in a spatially limited location. Comparison with EIT images shows the Fe XVIII emission to overlie a growing post-flare loop system formed in the aftermath of the CME. The emission most likely originates in a current sheet overlying the arcade. Analysis of the [Fe XVIII] emission allows us to infer the evolution of physical parameters in the current sheet over the entire span of our observations: in particular, we give the temperature vs. time in the current sheet and estimate the density. At the time of the quadrature, Ulysses was directly above the location of the CME and intercepted the ejecta. High ionization state Fe was detected by Ulysses-SWICS throughout the magnetic cloud associated with the CME. Both the remote and in situ observations are compared with predictions of theoretical CME models.

PROPAGATION OF THE 2014 JANUARY 7 CME AND RESULTING GEOMAGNETIC NON-EVENT

DOE Office of Scientific and Technical Information (OSTI.GOV)

Mays, M. L.; Collinson, G.; Taktakishvili, A.

2015-10-20

On 2014 January 7 an X1.2 flare and coronal mass ejection (CME) with a radial speed ≈2500 km s{sup −1} was observed from near an active region close to disk center. This led many forecasters to estimate a rapid arrival at Earth (≈36 hr) and predict a strong geomagnetic storm. However, only a glancing CME arrival was observed at Earth with a transit time of ≈49 hr and a K{sub P} geomagnetic index of only 3−. We study the interplanetary propagation of this CME using the ensemble Wang-Sheeley-Arge (WSA)–ENLIL+Cone model, that allows a sampling of CME parameter uncertainties. We exploremore » a series of simulations to isolate the effects of the background solar wind solution, CME shape, tilt, location, size, and speed, and the results are compared with observed in situ arrivals at Venus, Earth, and Mars. Our results show that a tilted ellipsoid CME shape improves the initial real-time prediction to better reflect the observed in situ signatures and the geomagnetic storm strength. CME parameters from the Graduated Cylindrical Shell model used as input to WSA–ENLIL+Cone, along with a tilted ellipsoid cloud shape, improve the arrival-time error by 14.5, 18.7, 23.4 hr for Venus, Earth, and Mars respectively. These results highlight that CME orientation and directionality with respect to observatories play an important role in understanding the propagation of this CME, and for forecasting other glancing CME arrivals. This study also demonstrates the importance of three-dimensional CME fitting made possible by multiple viewpoint imaging.« less

Testing model for prediction system of 1-AU arrival times of CME-associated interplanetary shocks

NASA Astrophysics Data System (ADS)

Ogawa, Tomoya; den, Mitsue; Tanaka, Takashi; Sugihara, Kohta; Takei, Toshifumi; Amo, Hiroyoshi; Watari, Shinichi

We test a model to predict arrival times of interplanetary shock waves associated with coronal mass ejections (CMEs) using a three-dimensional adaptive mesh refinement (AMR) code. The model is used for the prediction system we develop, which has a Web-based user interface and aims at people who is not familiar with operation of computers and numerical simulations or is not researcher. We apply the model to interplanetary CME events. We first choose coronal parameters so that property of background solar wind observed by ACE space craft is reproduced. Then we input CME parameters observed by SOHO/LASCO. Finally we compare the predicted arrival times with observed ones. We describe results of the test and discuss tendency of the model.

Propagation Characteristics of CMEs Associated with Magnetic Clouds and Ejecta

NASA Astrophysics Data System (ADS)

Kim, R.-S.; Gopalswamy, N.; Cho, K.-S.; Moon, Y.-J.; Yashiro, S.

2013-05-01

We have investigated the characteristics of magnetic cloud (MC) and ejecta (EJ) associated coronal mass ejections (CMEs) based on the assumption that all CMEs have a flux rope structure. For this, we used 54 CMEs and their interplanetary counterparts (interplanetary CMEs: ICMEs) that constitute the list of events used by the NASA/LWS Coordinated Data Analysis Workshop (CDAW) on CME flux ropes. We considered the location, angular width, and speed as well as the direction parameter, D. The direction parameter quantifies the degree of asymmetry of the CME shape in coronagraph images, and shows how closely the CME propagation is directed to Earth. For the 54 CDAW events, we found the following properties of the CMEs: i) the average value of D for the 23 MCs (0.62) is larger than that for the 31 EJs (0.49), which indicates that the MC-associated CMEs propagate more directly toward the Earth than the EJ-associated CMEs; ii) comparison between the direction parameter and the source location shows that the majority of the MC-associated CMEs are ejected along the radial direction, while many of the EJ-associated CMEs are ejected non-radially; iii) the mean speed of MC-associated CMEs (946 km s-1) is faster than that of EJ-associated CMEs (771 km s-1). For seven very fast CMEs (≥ 1500 km s-1), all CMEs with large D (≥ 0.4) are associated with MCs and the CMEs with small D are associated with EJs. From the statistical analysis of CME parameters, we found the superiority of the direction parameter. Based on these results, we suggest that the CME trajectory essentially determines the observed ICME structure.

Solar Energetic Particle Events and CME Accelerations in the Low Corona: MLSO Observations

NASA Astrophysics Data System (ADS)

St Cyr, O. C.; Kahler, S. W.; Richardson, I. G.; Cane, H. V.; Xie, H.; Burkepile, J.

2016-12-01

The low solar corona (< 2.5 Rs) is the region in which maximum coronal mass ejection (CME) acceleration occurs and where Type II radio observations suggest that shock formation occurs (Mäkelä et al., 2015). It is therefore a key region for investigations of solar energetic particle (SEP) acceleration by CME-driven shocks. Observations very low in the corona are necessary to detect the rapid CME accelerations leading to shock formation and to assess the speeds of CMEs through the middle corona. However, these observations cannot be made by space borne coronagraphs in which CME trajectories above the occulting disk are usually characterized by a single (constant) speed: e.g., 80% of the speeds in the compilation of SMM CMEs (Burkepile and St. Cyr, 1993) and SOHO LASCO CMEs (St. Cyr et al., 2000). The Mk3/Mk4/K-Cor coronameters at the Mauna Loa Solar Observatory are able to measure the initial accelerations of CMEs low in the corona (i.e., < 2 Rs). We examine a subset of CMEs that were associated with SEP events between 1980-present. The subset is based on the CME launch occurring between 16 UT - 01 UT - the MLSO observing window. In most cases, the CME accelerations are significantly larger than those measured by spaceborne coronagraphs (e.g., SMM, Solwind, LASCO, SECCHI). We will present the preliminary results of a comparison of the SEP parameters with initial CME accelerations in the MLSO coronagraph field of view.

Predicting the Magnetic Field of Earth-Impacting CMEs

NASA Technical Reports Server (NTRS)

Kay, C.; Gopalswamy, N.; Reinard, A.; Opher, M.

2017-01-01

Predicting the impact of coronal mass ejections (CMEs) and the southward component of their magnetic field is one of the key goals of space weather forecasting. We present a new model, the ForeCAT In situ Data Observer (FIDO), for predicting the in situ magnetic field of CMEs. We first simulate a CME using ForeCAT, a model for CME deflection and rotation resulting from the background solar magnetic forces. Using the CME position and orientation from ForeCAT, we then determine the passage of the CME over a simulated spacecraft. We model the CME's magnetic field using a force-free flux rope and we determine the in situ magnetic profile at the synthetic spacecraft. We show that FIDO can reproduce the general behavior of four observed CMEs. FIDO results are very sensitive to the CME's position and orientation, and we show that the uncertainty in a CME's position and orientation from coronagraph images corresponds to a wide range of in situ magnitudes and even polarities. This small range of positions and orientations also includes CMEs that entirely miss the satellite. We show that two derived parameters (the normalized angular distance between the CME nose and satellite position and the angular difference between the CME tilt and the position angle of the satellite with respect to the CME nose) can be used to reliably determine whether an impact or miss occurs. We find that the same criteria separate the impacts and misses for cases representing all four observed CMEs.

Conditions for the existence of Kelvin-Helmholtz instability in a CME

NASA Astrophysics Data System (ADS)

Páez, Andrés; Jatenco-Pereira, Vera; Falceta-Gonçcalves, Diego; Opher, Merav

The presence of Kelvin-Helmholtz instability (KHI) in the sheaths of Coronal Mass Ejections (CMEs) has been proposed and observed by several authors in the literature. In the present work, we assume their existence and propose a method to constrain the local properties, like the CME magnetic field intensity for the development of KHI. We study a CME in the initiation phase interacting with the slow solar wind (Zone I) and with the fast solar wind (Zone II). Based on the theory of magnetic KHI proposed by Chandrasekhar (1961) we found the radial heliocentric interval for the KHI existence, in particular we constrain it with the CME magnetic field intensity. We conclude that KHI may exist in both CME Zones but it is perceived that Zone I is more appropriated for the KHI formation.

A Monster CME Obscuring a Demon Star Flare

NASA Astrophysics Data System (ADS)

Moschou, Sofia-Paraskevi; Drake, Jeremy J.; Cohen, Ofer; Alvarado-Gomez, Julian D.; Garraffo, Cecilia

2017-12-01

We explore the scenario of a coronal mass ejection (CME) being the cause of the observed continuous X-ray absorption of the 1997 August 30 superflare on the eclipsing binary Algol (the Demon Star). The temporal decay of the absorption is consistent with absorption by a CME undergoing self-similar evolution with uniform expansion velocity. We investigate the kinematic and energetic properties of the CME using the ice cream cone model for its three-dimensional structure in combination with the observed profile of the hydrogen column density decline with time. Different physically justified length scales were used that allowed us to estimate lower and upper limits of the possible CME characteristics. Further consideration of the maximum available magnetic energy in starspots leads us to quantify its mass as likely lying in the range 2× {10}21 {--} 2× {10}22 g and kinetic energy in the range 7× {10}35 {--} 3× {10}38 erg. The results are in reasonable agreement with extrapolated relations between flare X-ray fluence and CME mass and kinetic energy derived for solar CMEs.

The Interaction of Coronal Mass Ejections with Alfvénic Turbulence

NASA Astrophysics Data System (ADS)

Manchester, Ward, IV; Van Der Holst, Bart

2017-09-01

We provide a first attempt to understand the interaction between Alfvén wave turbulence, kinetic instabilities and temperature anisotropies in the environment of a fast coronal mass ejection (CME) near the Sun. The impact of a fast CME on the solar corona causes turbulent energy, thermal energy and dissipative heating to increase by orders of magnitude, and produces conditions suitable for a host of kinetic instabilities. We study these CME-induced effects with the recently developed Alfvén Wave Solar Model, with which we are able to self-consistently simulate the turbulent energy transport and dissipation as well as isotropic electron heating and anisotropic proton heating. Furthermore, the model also offers the capability to address the effects of fire hose, mirror mode, and cyclotron kinetic instabilities on proton energy partitioning all in a global-scale numerical simulation. We find amplified turbulent energy in the CME sheath, along with strong wave reflection at the shock combine to cause wave dissipation rates to increase by more than a factor of 100. In contrast, wave energy is greatly diminished by adiabatic expansion in the flux rope. Finally, we find proton temperature anisotropies are limited by kinetic instabilities to a level consistent with solar wind observations.

The Interaction of Coronal Mass Ejections with Alfvenic Turbulence

NASA Astrophysics Data System (ADS)

Manchester, W.; van der Holst, B.

2017-12-01

We provide a first attempt to understand the interaction between Alfven wave turbulence, kinetic instabilities and temperature anisotropies in the environment of a fast coronal mass ejection (CME). The impact of a fast CME on the solar corona causes turbulent energy, thermal energy and dissipative heating to increase by orders of magnitude, and produces conditions suitable for a host of kinetic instabilities. We study these CME-induced effects with the recently developed Alfven Wave Solar Model, with which we are able to self-consistently simulate the turbulent energy transport and dissipation as well as isotropic electron heating and anisotropic proton heating. Furthermore, the model also offers the capability to address the effects of firehose, mirror mode, and cyclotron kinetic instabilities on proton energy partitioning, all in a global-scale numerical simulation. We find turbulent energy greatly enhanced in the CME sheath, strong wave reflection at the shock, which leads to wave dissipation rates increasing by more than a factor of 100. In contrast, wave energy is greatly diminished by adiabatic expansion in the flux rope. Finally, we find proton temperature anisotropies are limited by kinetic instabilities to a level consistent with solar wind observations.

Simulating AIA observations of a flux rope ejection

NASA Astrophysics Data System (ADS)

Pagano, P.; Mackay, D. H.; Poedts, S.

2014-08-01

Context. Coronal mass ejections (CMEs) are the most violent phenomena observed on the Sun. Currently, extreme ultraviolet (EUV) images from the Atmospheric Imaging Assembly (AIA) on board the Solar Dynamic Observatory (SDO) are providing new insights into the early phase of CME evolution. In particular, observations now show the ejection of magnetic flux ropes from the solar corona and how they evolve into CMEs. While this is the case, these observations are difficult to interpret in terms of basic physical mechanisms and quantities. To fully understand CMEs we need to compare equivalent quantities derived from both observations and theoretical models. This will aid in bridging the gap between observations and models. Aims: To this end, we aim to produce synthesised AIA observations from simulations of a flux rope ejection. To carry this out we include the role of thermal conduction and radiative losses, both of which are important for determining the temperature distribution of the solar corona during a CME. Methods: We perform a simulation where a flux rope is ejected from the solar corona. From the density and temperature of the plasma in the simulation we synthesise AIA observations. The emission is then integrated along the line of sight using the instrumental response function of AIA. Results: We sythesise observations of AIA in the channels at 304 Å, 171 Å, 335 Å, and 94 Å. The synthesised observations show a number of features similar to actual observations and in particular reproduce the general development of CMEs in the low corona as observed by AIA. In particular we reproduce an erupting and expanding arcade in the 304 Å and 171 Å channels with a high density core. Conclusions: The ejection of a flux rope reproduces many of the features found in the AIA observations. This work is therefore a step forward in bridging the gap between observations and models, and can lead to more direct interpretations of EUV observations in terms of flux rope ejections. We plan to improve the model in future studies in order to perform a more quantitative comparison. Movies associated with Figs. 3, 9, and 10 are available in electronic form at http://www.aanda.org

Analysis of powerful heliospheric non-geoeffective event of the 28 April, 2015 in muon flux

NASA Astrophysics Data System (ADS)

Astapov, I. I.; Barbashina, N. S.; Veselovsky, I. S.; Osetrova, N. V.; Petrukhin, A. A.; Shutenko, V. V.

2016-02-01

The coronal mass ejection (CME) that occurred on April 28, 2015 is analyzed. The passage of the ejection did not cause geoeffective disturbances in the near-Earth space. At the same time, the CME had a significant impact on the flux of cosmic rays registered on the Earth's surface by the muon hodoscope URAGAN.

Changes in left ventricular ejection fraction and coronary flow reserve after coronary microembolization

PubMed Central

Ma, Jianying; Qian, Juying; Zeng, Xin; Sun, Aijun; Chang, Shufu; Chen, Zhangwei; Zou, Yunzeng

2012-01-01

Introduction Although coronary microembolization (CME) is a frequent phenomenon in patients undergoing percutaneous coronary intervention, few data are available on the changes in left ventricular ejection fraction (LVEF) and coronary flow reserve (CFR) after CME. Material and methods In this study, six miniature swine of either sex (body weight 21-25 kg) were used to prepare a CME model. After coronary angiography, 1.2 × 105 microspheres (42 µm) were selectively infused into the left anterior descending artery via an infusion catheter. Left ventricular ejection fraction was evaluated using transthoracic echocardiography; myocardial blood flow was measured using coloured microspheres; and CFR and coronary pressure were measured using Doppler and a pressure wire. Results Left ventricular ejection fraction was 0.77 ±0.08 at baseline, 0.69 ±0.08 at 2 h, 0.68 ±0.08 at 6 h, and 0.76 ±0.06 at 1 week (2 h vs. baseline p < 0.05; 6 h vs. baseline p < 0.01). After CME, left ventricular end systolic volume (LVESV) and end diastolic volume (LVEDV) were significant larger 1 week later (p < 0.01 for both), while CFR was significantly reduced at 6 h (1.24 ±0.10 at 6 h vs. 1.77 ±0.30 at baseline, p < 0.01) and myocardial blood flow remained unchanged. Serum ET-1 level was significantly higher only at 6 h after CME (6 h vs. baseline p < 0.05). Conclusions Reduction of CFR and LVEF is significant at 6 h after CME and recovers 1 week later with left ventricular dilation. PMID:22457677

ON THE ENHANCED CORONAL MASS EJECTION DETECTION RATE SINCE THE SOLAR CYCLE 23 POLAR FIELD REVERSAL

DOE Office of Scientific and Technical Information (OSTI.GOV)

Petrie, G. J. D.

2015-10-10

Compared to cycle 23, coronal mass ejections (CMEs) with angular widths >30° have been observed to occur at a higher rate during solar cycle 24, per sunspot number. This result is supported by data from three independent databases constructed using Large Angle and Spectrometric Coronagraph Experiment coronagraph images, two employing automated detection techniques and one compiled manually by human observers. According to the two databases that cover a larger field of view, the enhanced CME rate actually began shortly after the cycle 23 polar field reversal, in 2004, when the polar fields returned with a 40% reduction in strength andmore » the interplanetary radial magnetic field became ≈30% weaker. This result is consistent with the link between anomalous CME expansion and the heliospheric total pressure decrease recently reported by Gopalswamy et al.« less

VLA Measurements of Faraday Rotation through Coronal Mass Ejections

NASA Astrophysics Data System (ADS)

Kooi, Jason E.; Fischer, Patrick D.; Buffo, Jacob J.; Spangler, Steven R.

2017-04-01

Coronal mass ejections (CMEs) are large-scale eruptions of plasma from the Sun, which play an important role in space weather. Faraday rotation is the rotation of the plane of polarization that results when a linearly polarized signal passes through a magnetized plasma such as a CME. Faraday rotation is proportional to the path integral through the plasma of the electron density and the line-of-sight component of the magnetic field. Faraday-rotation observations of a source near the Sun can provide information on the plasma structure of a CME shortly after launch. We report on simultaneous white-light and radio observations made of three CMEs in August 2012. We made sensitive Very Large Array (VLA) full-polarization observations using 1 - 2 GHz frequencies of a constellation of radio sources through the solar corona at heliocentric distances that ranged from 6 - 15 R_{⊙}. Two sources (0842+1835 and 0900+1832) were occulted by a single CME, and one source (0843+1547) was occulted by two CMEs. In addition to our radioastronomical observations, which represent one of the first active hunts for CME Faraday rotation since Bird et al. ( Solar Phys., 98, 341, 1985) and the first active hunt using the VLA, we obtained white-light coronagraph images from the Large Angle and Spectrometric Coronagraph (LASCO) C3 instrument to determine the Thomson-scattering brightness [BT], providing a means to independently estimate the plasma density and determine its contribution to the observed Faraday rotation. A constant-density force-free flux rope embedded in the background corona was used to model the effects of the CMEs on BT and Faraday rotation. The plasma densities (6 - 22×103 cm^{-3}) and axial magnetic-field strengths (2 - 12 mG) inferred from our models are consistent with the modeling work of Liu et al. ( Astrophys. J., 665, 1439, 2007) and Jensen and Russell ( Geophys. Res. Lett., 35, L02103, 2008), as well as previous CME Faraday-rotation observations by Bird et al. (1985).

Two-step forecast of geomagnetic storm using coronal mass ejection and solar wind condition

PubMed Central

Kim, R-S; Moon, Y-J; Gopalswamy, N; Park, Y-D; Kim, Y-H

2014-01-01

To forecast geomagnetic storms, we had examined initially observed parameters of coronal mass ejections (CMEs) and introduced an empirical storm forecast model in a previous study. Now we suggest a two-step forecast considering not only CME parameters observed in the solar vicinity but also solar wind conditions near Earth to improve the forecast capability. We consider the empirical solar wind criteria derived in this study (Bz ≤ −5 nT or Ey ≥ 3 mV/m for t≥ 2 h for moderate storms with minimum Dst less than −50 nT) and a Dst model developed by Temerin and Li (2002, 2006) (TL model). Using 55 CME-Dst pairs during 1997 to 2003, our solar wind criteria produce slightly better forecasts for 31 storm events (90%) than the forecasts based on the TL model (87%). However, the latter produces better forecasts for 24 nonstorm events (88%), while the former correctly forecasts only 71% of them. We then performed the two-step forecast. The results are as follows: (i) for 15 events that are incorrectly forecasted using CME parameters, 12 cases (80%) can be properly predicted based on solar wind conditions; (ii) if we forecast a storm when both CME and solar wind conditions are satisfied (∩), the critical success index becomes higher than that from the forecast using CME parameters alone, however, only 25 storm events (81%) are correctly forecasted; and (iii) if we forecast a storm when either set of these conditions is satisfied (∪), all geomagnetic storms are correctly forecasted. PMID:26213515

Connecting Coronal Mass Ejections to Their Solar Active Region Sources: Combining Results from the HELCATS and FLARECAST Projects

NASA Astrophysics Data System (ADS)

Murray, Sophie A.; Guerra, Jordan A.; Zucca, Pietro; Park, Sung-Hong; Carley, Eoin P.; Gallagher, Peter T.; Vilmer, Nicole; Bothmer, Volker

2018-04-01

Coronal mass ejections (CMEs) and other solar eruptive phenomena can be physically linked by combining data from a multitude of ground-based and space-based instruments alongside models; however, this can be challenging for automated operational systems. The EU Framework Package 7 HELCATS project provides catalogues of CME observations and properties from the Heliospheric Imagers on board the two NASA/STEREO spacecraft in order to track the evolution of CMEs in the inner heliosphere. From the main HICAT catalogue of over 2,000 CME detections, an automated algorithm has been developed to connect the CMEs observed by STEREO to any corresponding solar flares and active-region (AR) sources on the solar surface. CME kinematic properties, such as speed and angular width, are compared with AR magnetic field properties, such as magnetic flux, area, and neutral line characteristics. The resulting LOWCAT catalogue is also compared to the extensive AR property database created by the EU Horizon 2020 FLARECAST project, which provides more complex magnetic field parameters derived from vector magnetograms. Initial statistical analysis has been undertaken on the new data to provide insight into the link between flare and CME events, and characteristics of eruptive ARs. Warning thresholds determined from analysis of the evolution of these parameters is shown to be a useful output for operational space weather purposes. Parameters of particular interest for further analysis include total unsigned flux, vertical current, and current helicity. The automated method developed to create the LOWCAT catalogue may also be useful for future efforts to develop operational CME forecasting.

Two-step forecast of geomagnetic storm using coronal mass ejection and solar wind condition.

PubMed

Kim, R-S; Moon, Y-J; Gopalswamy, N; Park, Y-D; Kim, Y-H

2014-04-01

To forecast geomagnetic storms, we had examined initially observed parameters of coronal mass ejections (CMEs) and introduced an empirical storm forecast model in a previous study. Now we suggest a two-step forecast considering not only CME parameters observed in the solar vicinity but also solar wind conditions near Earth to improve the forecast capability. We consider the empirical solar wind criteria derived in this study ( B z  ≤ -5 nT or E y  ≥ 3 mV/m for t ≥ 2 h for moderate storms with minimum Dst less than -50 nT) and a Dst model developed by Temerin and Li (2002, 2006) (TL model). Using 55 CME- Dst pairs during 1997 to 2003, our solar wind criteria produce slightly better forecasts for 31 storm events (90%) than the forecasts based on the TL model (87%). However, the latter produces better forecasts for 24 nonstorm events (88%), while the former correctly forecasts only 71% of them. We then performed the two-step forecast. The results are as follows: (i) for 15 events that are incorrectly forecasted using CME parameters, 12 cases (80%) can be properly predicted based on solar wind conditions; (ii) if we forecast a storm when both CME and solar wind conditions are satisfied (∩), the critical success index becomes higher than that from the forecast using CME parameters alone, however, only 25 storm events (81%) are correctly forecasted; and (iii) if we forecast a storm when either set of these conditions is satisfied (∪), all geomagnetic storms are correctly forecasted.

A Statistical Study of CME Properties and of the Correlation Between Flares and CMEs over Solar Cycles 23 and 24

NASA Astrophysics Data System (ADS)

Compagnino, A.; Romano, P.; Zuccarello, F.

2017-01-01

We investigated some properties of coronal mass ejections (CMEs), such as speed, acceleration, polar angle, angular width, and mass, using data acquired by the Large Angle Spectrometric Coronagraph (LASCO) onboard the Solar and Heliospheric Observatory (SOHO) from 31 July 1997 to 31 March 2014, i.e. during the Solar Cycles 23 and 24. We used two CME catalogs: one provided by the Coordinated Data Analysis Workshops (CDAW) Data Center and one obtained by the Computer Aided CME Tracking software (CACTus) detection algorithm. For each dataset, we found that the number of CMEs observed during the peak of Cycle 24 was higher than or comparable to the number during Cycle 23, although the photospheric activity during Cycle 24 was weaker than during Cycle 23. Using the CMEs detected by CACTus, we noted that the number of events [N] is of the same order of magnitude during the peaks of the two cycles, but the peak of the CME distribution during Cycle 24 is more extended in time (N > 1500 during 2012 and 2013). We ascribe the discrepancy between the CDAW and CACTus results to the observer bias for CME definition in the CDAW catalog. We also used a dataset containing 19,811 flares of C-, M-, and X-class observed by the Geostationary Operational Environmental Satellite (GOES) during the same period. Using both datasets, we studied the relationship between the mass ejected by the CMEs and the flux emitted during the corresponding flares: we found 11,441 flares that were temporally correlated with CMEs for CDAW and 9120 for CACTus. Moreover, we found a log-linear relationship between the flux of the flares integrated from the start to end in the 0.1 - 0.8 nm range and the CME mass. We also found some differences in the mean CMEs velocity and acceleration between the events associated with flares and those that were not.

On the deficit problem of mass and energy of solar coronal mass ejections connected with interplanetary shocks

NASA Technical Reports Server (NTRS)

Ivanchuk, V. I.; Pishkalo, N. I.

1995-01-01

Mean values of a number of parameters of the most powerful coronal mass ejections (CMEs) and interplanetary shocks generated by these ejections are estimated using an analysis of data obtained by the cosmic coronagraphs and spacecrafts, and geomagnetic storm measurements. It was payed attention that the shock mass and mechanical energy, averaging 5 x 10(exp 16) grm and 2 x 10(exp 32) erg respectively, are nearly 10 times larger than corresponding parameters of the ejections. So, the CME energy deficit problem seems to exist really. To solve this problem one can make an assumption that the process of the mass and energy growth of CMEs during their propagation out of the Sun observed in the solar corona is continued in supercorona too up to distances of 10-30 solar radii. This assumption is confirmed by the data analysis of five events observed using zodiacal light photometers of the HELIOS- I and HELIOS-2 spacecrafts. The mass growth rate is estimated to be equal to (1-7) x 10(exp 11) grm/sec. It is concluded that the CME contribution to mass and energy flows in the solar winds probably, is larger enough than the value of 3-5% adopted usually.

Estimation of a coronal mass ejection magnetic field strength using radio observations of gyrosynchrotron radiation

NASA Astrophysics Data System (ADS)

Carley, Eoin P.; Vilmer, Nicole; Simões, Paulo J. A.; Ó Fearraigh, Brían

2017-12-01

Coronal mass ejections (CMEs) are large eruptions of plasma and magnetic field from the low solar corona into interplanetary space. These eruptions are often associated with the acceleration of energetic electrons which produce various sources of high intensity plasma emission. In relatively rare cases, the energetic electrons may also produce gyrosynchrotron emission from within the CME itself, allowing for a diagnostic of the CME magnetic field strength. Such a magnetic field diagnostic is important for evaluating the total magnetic energy content of the CME, which is ultimately what drives the eruption. Here, we report on an unusually large source of gyrosynchrotron radiation in the form of a type IV radio burst associated with a CME occurring on 2014-September-01, observed using instrumentation from the Nançay Radio Astronomy Facility. A combination of spectral flux density measurements from the Nançay instruments and the Radio Solar Telescope Network (RSTN) from 300 MHz to 5 GHz reveals a gyrosynchrotron spectrum with a peak flux density at 1 GHz. Using this radio analysis, a model for gyrosynchrotron radiation, a non-thermal electron density diagnostic using the Fermi Gamma Ray Burst Monitor (GBM) and images of the eruption from the GOES Soft X-ray Imager (SXI), we were able to calculate both the magnetic field strength and the properties of the X-ray and radio emitting energetic electrons within the CME. We find the radio emission is produced by non-thermal electrons of energies >1 MeV with a spectral index of δ 3 in a CME magnetic field of 4.4 G at a height of 1.3 R⊙, while the X-ray emission is produced from a similar distribution of electrons but with much lower energies on the order of 10 keV. We conclude by comparing the electron distribution characteristics derived from both X-ray and radio and show how such an analysis can be used to define the plasma and bulk properties of a CME.

Solar origins of coronal mass ejections

NASA Technical Reports Server (NTRS)

Kahler, Stephen

1987-01-01

The large scale properties of coronal mass ejections (CMEs), such as morphology, leading edge speed, and angular width and position, have been cataloged for many events observed with coronagraphs on the Skylab, P-78, and SMM spacecraft. While considerable study has been devoted to the characteristics of the SMEs, their solar origins are still only poorly understood. Recent observational work has involved statistical associations of CMEs with flares and filament eruptions, and some evidence exists that the flare and eruptive-filament associated CMEs define two classes of events, with the former being generally more energetic. Nevertheless, it is found that eruptive-filament CMEs can at times be very energetic, giving rise to interplanetary shocks and energetic particle events. The size of the impulsive phase in a flare-associated CME seems to play no significant role in the size or speed of the CME, but the angular sizes of CMEs may correlate with the scale sizes of the 1-8 angstrom x-ray flares. At the present time, He 10830 angstrom observations should be useful in studying the late development of double-ribbon flares and transient coronal holes to yield insights into the CME aftermath. The recently available white-light synoptic maps may also prove fruitful in defining the coronal conditions giving rise to CMEs.

Height of shock formation in the solar corona inferred from observations of type II radio bursts and coronal mass ejections

NASA Astrophysics Data System (ADS)

Gopalswamy, N.; Xie, H.; Mäkelä, P.; Yashiro, S.; Akiyama, S.; Uddin, W.; Srivastava, A. K.; Joshi, N. C.; Chandra, R.; Manoharan, P. K.; Mahalakshmi, K.; Dwivedi, V. C.; Jain, R.; Awasthi, A. K.; Nitta, N. V.; Aschwanden, M. J.; Choudhary, D. P.

2013-06-01

Employing coronagraphic and EUV observations close to the solar surface made by the Solar Terrestrial Relations Observatory (STEREO) mission, we determined the heliocentric distance of coronal mass ejections (CMEs) at the starting time of associated metric type II bursts. We used the wave diameter and leading edge methods and measured the CME heights for a set of 32 metric type II bursts from solar cycle 24. We minimized the projection effects by making the measurements from a view that is roughly orthogonal to the direction of the ejection. We also chose image frames close to the onset times of the type II bursts, so no extrapolation was necessary. We found that the CMEs were located in the heliocentric distance range from 1.20 to 1.93 solar radii (Rs), with mean and median values of 1.43 and 1.38 Rs, respectively. We conclusively find that the shock formation can occur at heights substantially below 1.5 Rs. In a few cases, the CME height at type II onset was close to 2 Rs. In these cases, the starting frequency of the type II bursts was very low, in the range 25-40 MHz, which confirms that the shock can also form at larger heights. The starting frequencies of metric type II bursts have a weak correlation with the measured CME/shock heights and are consistent with the rapid decline of density with height in the inner corona.

Height of Shock Formation in the Solar Corona Inferred from Observations of Type II Radio Bursts and Coronal Mass Ejections

NASA Technical Reports Server (NTRS)

Gopalswamy, N.; Xie, H.; Makela, P.; Yashiro, S.; Akiyama, S.; Uddin, W.; Srivastava, A. K.; Joshi, N. C.; Chandra, R.; Manoharan, P. K.

2013-01-01

Employing coronagraphic and EUV observations close to the solar surface made by the Solar Terrestrial Relations Observatory (STEREO) mission, we determined the heliocentric distance of coronal mass ejections (CMEs) at the starting time of associated metric type II bursts. We used the wave diameter and leading edge methods and measured the CME heights for a set of 32 metric type II bursts from solar cycle 24. We minimized the projection effects by making the measurements from a view that is roughly orthogonal to the direction of the ejection. We also chose image frames close to the onset times of the type II bursts, so no extrapolation was necessary. We found that the CMEs were located in the heliocentric distance range from 1.20 to 1.93 solar radii (Rs), with mean and median values of 1.43 and 1.38 Rs, respectively. We conclusively find that the shock formation can occur at heights substantially below 1.5 Rs. In a few cases, the CME height at type II onset was close to 2 Rs. In these cases, the starting frequency of the type II bursts was very low, in the range 25-40 MHz, which confirms that the shock can also form at larger heights. The starting frequencies of metric type II bursts have a weak correlation with the measured CME/shock heights and are consistent with the rapid decline of density with height in the inner corona.

A Historic View of Solar Coronal Mass Ejections (CMEs)

NASA Technical Reports Server (NTRS)

SaintCyr, Orville C.

2010-01-01

We present a historic overview of CME observations, ending with concepts for future measurement capabilities. One of the first detections of what we now call a CME was provided by instrumentation on OSO-7 and reported by Tousey (1973); but the phrase "corona) mass ejection" was coined after the Skylab/ATM coronagraph detected dozens of the transients over its nine month observing run (e.g., Munro et al., 1979). Pre-discovery identification of likely CMEs were then reported in historic eclipse photographs and drawings (e.g., Eddy, 1974; Cliver, 1989). Multi-year observations followed with groundbased MLSO MK3/4 coronagraph (1980-present), and spacebased missions: Solwind (1979-1985), SMM (1980-1989), SOHO LASCO/EIT (1996-present), SMEI (2003-present), and STEREO SECCHI (2006-present). The Spartan 201 coronagraph flew in space multiple times. The influential Gosling (1993) "solar flare myth" manuscript identified CMEs as the cause of the most severe geomagnetic storms, thus cementing their importance in Sun-Earth connection studies. A new window into CMEs was opened with the launch of SOHO in 1995 when the UVCS spectrometer began returning plasma diagnostics of a significant number of events (e.g., Ciaravella et al., 2006). What about the future for CME research? Statistical properties of the UVCS CME observations are forthcoming; the STEREO mission should continue to return views of CMEs from unique vantage points; and the recent launch of SDO should provide new insights into the small spatial scale dynamics of activity associated with CMEs. Several new observing techniques have been demonstrated at total eclipses, and inclusion on spacebased platforms in the future could also prove valuable for understanding CMEs. A common element of several recent proposals is to image the white-light corona with extremely high spatial resolution. The momentary glimpses of the corona during total solar eclipses have shown fine structure that is not captured by global models, and dynamics of these structured elements may be important to resolve the question of CME initiation.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Krupar, V.; Eastwood, J. P.; Kruparova, O.

Coronal mass ejections (CMEs) are large-scale eruptions of magnetized plasma that may cause severe geomagnetic storms if Earth directed. Here, we report a rare instance with comprehensive in situ and remote sensing observations of a CME combining white-light, radio, and plasma measurements from four different vantage points. For the first time, we have successfully applied a radio direction-finding technique to an interplanetary type II burst detected by two identical widely separated radio receivers. The derived locations of the type II and type III bursts are in general agreement with the white-light CME reconstruction. We find that the radio emission arisesmore » from the flanks of the CME and are most likely associated with the CME-driven shock. Our work demonstrates the complementarity between radio triangulation and 3D reconstruction techniques for space weather applications.« less

DOE Office of Scientific and Technical Information (OSTI.GOV)

Bein, B. M.; Temmer, M.; Veronig, A. M.

Using combined STEREO-A and STEREO-B EUVI, COR1, and COR2 data, we derive deprojected coronal mass ejection (CME) kinematics and CME ''true'' mass evolutions for a sample of 25 events that occurred during 2007 December to 2011 April. We develop a fitting function to describe the CME mass evolution with height. The function considers both the effect of the coronagraph occulter, at the beginning of the CME evolution, and an actual mass increase. The latter becomes important at about 10-15 R{sub Sun} and is assumed to mostly contribute up to 20 R{sub Sun }. The mass increase ranges from 2% tomore » 6% per R{sub Sun} and is positively correlated to the total CME mass. Due to the combination of COR1 and COR2 mass measurements, we are able to estimate the ''true'' mass value for very low coronal heights (<3 R{sub Sun }). Based on the deprojected CME kinematics and initial ejected masses, we derive the kinetic energies and propelling forces acting on the CME in the low corona (<3 R{sub Sun }). The derived CME kinetic energies range between 1.0-66 Multiplication-Sign 10{sup 23} J, and the forces range between 2.2-510 Multiplication-Sign 10{sup 14} N.« less

CME Flux Rope and Shock Identifications and Locations: Comparison of White Light Data, Graduated Cylindrical Shell Model, and MHD Simulations

NASA Technical Reports Server (NTRS)

Schmidt, J. M.; Cairns, Iver H.; Xie, Hong; St. Cyr, O. C.; Gopalswamy, N.

2016-01-01

Coronal mass ejections (CMEs) are major transient phenomena in the solar corona that are observed with ground-based and spacecraft-based coronagraphs in white light or with in situ measurements by spacecraft. CMEs transport mass and momentum and often drive shocks. In order to derive the CME and shock trajectories with high precision, we apply the graduated cylindrical shell (GCS) model to fit a flux rope to the CME directed toward STEREO A after about 19:00 UT on 29 November 2013 and check the quality of the heliocentric distance-time evaluations by carrying out a three-dimensional magnetohydrodynamic (MHD) simulation of the same CME with the Block Adaptive Tree Solar-Wind Roe Upwind Scheme (BATS-R-US) code. Heliocentric distances of the CME and shock leading edges are determined from the simulated white light images and magnetic field strength data. We find very good agreement between the predicted and observed heliocentric distances, showing that the GCS model and the BATS-R-US simulation approach work very well and are consistent. In order to assess the validity of CME and shock identification criteria in coronagraph images, we also compute synthetic white light images of the CME and shock. We find that the outer edge of a cloud-like illuminated area in the observed and predicted images in fact coincides with the leading edge of the CME flux rope and that the outer edge of a faint illuminated band in front of the CME leading edge coincides with the CME-driven shock front.

Using the Coronal Evolution to Successfully Forward Model CMEs' In Situ Magnetic Profiles

NASA Astrophysics Data System (ADS)

Kay, C.; Gopalswamy, N.

2017-12-01

Predicting the effects of a coronal mass ejection (CME) impact requires knowing if impact will occur, which part of the CME impacts, and its magnetic properties. We explore the relation between CME deflections and rotations, which change the position and orientation of a CME, and the resulting magnetic profiles at 1 AU. For 45 STEREO-era, Earth-impacting CMEs, we determine the solar source of each CME, reconstruct its coronal position and orientation, and perform a ForeCAT (Forecasting a CME's Altered Trajectory) simulation of the coronal deflection and rotation. From the reconstructed and modeled CME deflections and rotations, we determine the solar cycle variation and correlations with CME properties. We assume no evolution between the outer corona and 1 AU and use the ForeCAT results to drive the ForeCAT In situ Data Observer (FIDO) in situ magnetic field model, allowing for comparisons with ACE and Wind observations. We do not attempt to reproduce the arrival time. On average FIDO reproduces the in situ magnetic field for each vector component with an error equivalent to 35% of the average total magnetic field strength when the total modeled magnetic field is scaled to match the average observed value. Random walk best fits distinguish between ForeCAT's ability to determine FIDO's input parameters and the limitations of the simple flux rope model. These best fits reduce the average error to 30%. The FIDO results are sensitive to changes of order a degree in the CME latitude, longitude, and tilt, suggesting that accurate space weather predictions require accurate measurements of a CME's position and orientation.

Testing ElEvoHI on a multi-point in situ detected Coronal Mass Ejection

NASA Astrophysics Data System (ADS)

Amerstorfer, Tanja; Möstl, Christian; Hess, Phillip; Mays, M. Leila; Temmer, Manuela

2017-04-01

The Solar TErrestrial RElations Observatory (STEREO) has provided us a deep insight into the interplanetary propagation of coronal mass ejections (CMEs). Especially the wide-angle heliospheric imagers (HI) enabled the development of a multitude of methods for analyzing the evolution of CMEs through interplanetary (IP) space. Methods able to forecast arrival times and speeds at Earth (or other targets) use the advantage of following a CME's path of propagation up to 1 AU. However, these methods were not able to reduce today's errors in arrival time forecasts to less than ±6 hours, arrival speeds are mostly overestimated by some 100 km s-1. One reason for that is the assumption of constant propagation speed, which is clearly incorrect for most CMEs—especially for those being faster than the ambient solar wind. ElEvoHI, the Ellipse Evolution model (ElEvo) based on HI observations, is a new prediction tool, which uses the benefits of different methods and observations. It provides the possibility to adjust the CME frontal shape (angular width, ellipse aspect ratio) and the direction of motion for each CME event individually. This information can be gained from Graduated Cylindrical Shell (GCS) flux-rope fitting within coronagraph images. Using the Ellipse Conversion (ElCon) method, the observed HI elongation angle is converted into a unit of distance, which reveals the kinematics of the event. After fitting the time-distance profile of the CME using the drag-based equation of motion, where real-time in situ solar wind speed from 1 AU is used as additional input, we receive all input parameters needed to run a forecast using the ElEvo model and to predict arrival times and speeds at any target of interest in IP space. Here, we present a test on a slow CME event of 3 November 2010, in situ detected by the lined-up spacecraft MESSENGER and STEREO Behind. We gain the shape of the CME front from a cut of the 3D GCS CME shape with the ecliptic plane, resulting in an almost ideal ElEvoHI forecast of arrival time and speed at 1 AU.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Liu, Ying D.; Luhmann, Janet G.; Moestl, Christian

We investigate how coronal mass ejections (CMEs) propagate through, and interact with, the inner heliosphere between the Sun and Earth, a key question in CME research and space weather forecasting. CME Sun-to-Earth kinematics are constrained by combining wide-angle heliospheric imaging observations, interplanetary radio type II bursts, and in situ measurements from multiple vantage points. We select three events for this study, the 2012 January 19, 23, and March 7 CMEs. Different from previous event studies, this work attempts to create a general picture for CME Sun-to-Earth propagation and compare different techniques for determining CME interplanetary kinematics. Key results are obtainedmore » concerning CME Sun-to-Earth propagation: (1) the Sun-to-Earth propagation of fast CMEs can be approximately formulated into three phases: an impulsive acceleration, then a rapid deceleration, and finally a nearly constant speed propagation (or gradual deceleration); (2) the CMEs studied here are still accelerating even after the flare maximum, so energy must be continuously fed into the CME even after the time of the maximum heating and radiation has elapsed in the corona; (3) the rapid deceleration, presumably due to interactions with the ambient medium, mainly occurs over a relatively short timescale following the acceleration phase; and (4) CME-CME interactions seem a common phenomenon close to solar maximum. Our comparison between different techniques (and data sets) has important implications for CME observations and their interpretations: (1) for the current cases, triangulation assuming a compact CME geometry is more reliable than triangulation assuming a spherical front attached to the Sun for distances below 50-70 solar radii from the Sun, but beyond about 100 solar radii we would trust the latter more; (2) a proper treatment of CME geometry must be performed in determining CME Sun-to-Earth kinematics, especially when the CME propagation direction is far away from the observer; and (3) our approach to comparing wide-angle heliospheric imaging observations with interplanetary radio type II bursts provides a novel tool in investigating CME propagation characteristics. Future CME observations and space weather forecasting are discussed based on these results.« less

Origin and Ion Charge State Evolution of Solar Wind Transients 4 - 7 August 2011

NASA Astrophysics Data System (ADS)

Rodkin, Denis; Goryaev, Farid; Pagano, Paolo; Gibb, Gordon; Slemzin, Vladimir; Shugay, Yulia; Veselovsky, Igor; Mackay, Duncan

2017-04-01

Identification of transients and their origins on the Sun is one of the most important problems of the space weather forecasting. In our work, we present a case study of the complex event consisting of several solar wind transients detected by ACE on 4 - 7 August 2011, that caused a geomagnetic storm with Dst= - 110 nT. The supposed coronal sources - three flares and coronal mass ejections (CMEs) occurred on 2 - 4 August 2011 in the active region AR 11261. To investigate the solar origins and formation of these transients, we studied kinematic and thermodynamic properties of expanding coronal structures using the SDO/AIA EUV images and the differential emission measure (DEM) diagnostics. The Helioseismic and Magnetic Imager (HMI) magnetic field maps were used as the input data for the 3D numerical model to describe the flux rope ejection. We characterize the early phase of the flux rope ejection in the corona, where the usual three-component CME structure formed. The flux rope ejected with the speed about 200 km/s to the height of 0.25 Rsun. The kinematics of the modeled CME front well agrees with the STEREO EUV measurements. Using the results of the plasma diagnostics and MHD modeling, we calculated the ion charge ratios of carbon and oxygen as well as the mean charge state of iron ions of the 2 August 2011 CME taking into account the processes of heating, cooling, expansion, ionization and recombination of the moving plasma in the corona up to the freeze-in region. We estimated a probable heating rate of the CME plasma in the low corona by matching the calculated ion composition parameters of the CME with that measured in-situ parameters of the solar wind transients. We also consider the similarities and discrepancies between the results of the MHD simulation and the observation of the event. Our results show that analysis of the ion composition of CMEs enables to disclose a relationship between parameters of the solar wind transients and properties of their solar origins, which opens new possibilities to validate and improve the solar wind forecasting models.

Validation of Real-time Modeling of Coronal Mass Ejections Using the WSA-ENLIL+Cone Heliospheric Model

NASA Astrophysics Data System (ADS)

Romano, M.; Mays, M. L.; Taktakishvili, A.; MacNeice, P. J.; Zheng, Y.; Pulkkinen, A. A.; Kuznetsova, M. M.; Odstrcil, D.

2013-12-01

Modeling coronal mass ejections (CMEs) is of great interest to the space weather research and forecasting communities. We present recent validation work of real-time CME arrival time predictions at different satellites using the WSA-ENLIL+Cone three-dimensional MHD heliospheric model available at the Community Coordinated Modeling Center (CCMC) and performed by the Space Weather Research Center (SWRC). SWRC is an in-house research-based operations team at the CCMC which provides interplanetary space weather forecasting for NASA's robotic missions and performs real-time model validation. The quality of model operation is evaluated by comparing its output to a measurable parameter of interest such as the CME arrival time and geomagnetic storm strength. The Kp index is calculated from the relation given in Newell et al. (2007), using solar wind parameters predicted by the WSA-ENLIL+Cone model at Earth. The CME arrival time error is defined as the difference between the predicted arrival time and the observed in-situ CME shock arrival time at the ACE, STEREO A, or STEREO B spacecraft. This study includes all real-time WSA-ENLIL+Cone model simulations performed between June 2011-2013 (over 400 runs) at the CCMC/SWRC. We report hit, miss, false alarm, and correct rejection statistics for all three spacecraft. For hits we show the average absolute CME arrival time error, and the dependence of this error on CME input parameters such as speed, width, and direction. We also present the predicted geomagnetic storm strength (using the Kp index) error for Earth-directed CMEs.

Turbulence and Heating in the Flank and Wake Regions of a Coronal Mass Ejection

NASA Astrophysics Data System (ADS)

Fan, Siteng; He, Jiansen; Yan, Limei; Tomczyk, Steven; Tian, Hui; Song, Hongqiang; Wang, Linghua; Zhang, Lei

2018-01-01

As a coronal mass ejection (CME) passes, the flank and wake regions are typically strongly disturbed. Various instruments, including the Large Angle and Spectroscopic Coronagraph (LASCO), the Atmospheric Imaging Assembly (AIA), and the Coronal Multi-channel Polarimeter (CoMP), observed a CME close to the east limb on 26 October 2013. A hot ({≈} 10 MK) rising blob was detected on the east limb, with an initial ejection flow speed of {≈} 330 km s^{-1}. The magnetic structures on both sides and in the wake of the CME were strongly distorted, showing initiation of turbulent motions with Doppler-shift oscillations enhanced from {≈} ± 3 km s^{-1} to {≈} ± 15 km s^{-1} and effective thermal velocities from {≈} 30 km s^{-1} to {≈} 60 km s^{-1}, according to the CoMP observations at the Fe xiii line. The CoMP Doppler-shift maps suggest that the turbulence behaved differently at various heights; it showed clear wave-like torsional oscillations at lower altitudes, which are interpreted as the antiphase oscillation of an alternating red/blue Doppler shift across the strands at the flank. The turbulence seems to appear differently in the channels of different temperatures. Its turnover time was {≈} 1000 seconds for the Fe 171 Å channel, while it was {≈} 500 seconds for the Fe 193 Å channel. Mainly horizontal swaying rotations were observed in the Fe 171 Å channel, while more vertical vortices were seen in the Fe 193 Å channel. The differential-emission-measure profiles in the flank and wake regions have two components that evolve differently: the cool component decreased over time, evidently indicating a drop-out of cool materials due to ejection, while the hot component increased dramatically, probably because of the heating process, which is suspected to be a result of magnetic reconnection and turbulence dissipation. These results suggest a new turbulence-heating scenario of the solar corona and solar wind.

3D Polarized Imaging of Coronal Mass Ejections: Chirality of a CME

NASA Astrophysics Data System (ADS)

DeForest, C. E.; de Koning, C. A.; Elliott, H. A.

2017-12-01

We report on a direct polarimetric determination of the chirality of a coronal mass ejection (CME), using the physics of Thomson scattering applied to synoptic polarized images from the Solar Terrestrial Relations Observatories/COR2 coronagraph. We confirmed the determination using in situ magnetic field measurements of the same CME with the ACE spacecraft. CME chirality is related to the helicity ejected from the solar corona along with the mass and field entrained in the CME. It is also important to prediction of the space-weather-relevant Z component of the CME magnetic field. Hence, remote measurement of CME chirality is an important step toward both understanding CME physics and predicting geoeffectiveness of individual CMEs. The polarimetric properties of Thomson scattering are well known and can, in principle, be used to measure the 3D structure of imaged objects in the solar corona and inner heliosphere. However, reduction of that principle to practice has been limited by the twin difficulties of background subtraction and the signal-to-noise ratio in coronagraph data. Useful measurements of the 3D structure require relative photometry at a few percent precision level in each linear polarization component of the K corona. This corresponds to a relative photometric precision of order 10-4 in direct images of the sky before subtraction of the F corona and related signal. Our measurement was enabled by recent developments in signal processing, which enable a better separation of the photometric signal from noise in the synoptic COR2 data. We discuss the relevance of this demonstration measurement to future instrument requirements, and to the future measurements of 3D structures in CMEs and other solar wind features.

The Interaction of Successive Coronal Mass Ejections: A Review

NASA Astrophysics Data System (ADS)

Lugaz, Noé; Temmer, Manuela; Wang, Yuming; Farrugia, Charles J.

2017-04-01

We present a review of the different aspects associated with the interaction of successive coronal mass ejections (CMEs) in the corona and inner heliosphere, focusing on the initiation of series of CMEs, their interaction in the heliosphere, the particle acceleration associated with successive CMEs, and the effect of compound events on Earth's magnetosphere. The two main mechanisms resulting in the eruption of series of CMEs are sympathetic eruptions, when one eruption triggers another, and homologous eruptions, when a series of similar eruptions originates from one active region. CME - CME interaction may also be associated with two unrelated eruptions. The interaction of successive CMEs has been observed remotely in coronagraphs (with the Large Angle and Spectrometric Coronagraph Experiment - LASCO - since the early 2000s) and heliospheric imagers (since the late 2000s), and inferred from in situ measurements, starting with early measurements in the 1970s. The interaction of two or more CMEs is associated with complex phenomena, including magnetic reconnection, momentum exchange, the propagation of a fast magnetosonic shock through a magnetic ejecta, and changes in the CME expansion. The presence of a preceding CME a few hours before a fast eruption has been found to be connected with higher fluxes of solar energetic particles (SEPs), while CME - CME interaction occurring in the corona is often associated with unusual radio bursts, indicating electron acceleration. Higher suprathermal population, enhanced turbulence and wave activity, stronger shocks, and shock - shock or shock - CME interaction have been proposed as potential physical mechanisms to explain the observed associated SEP events. When measured in situ, CME - CME interaction may be associated with relatively well organized multiple-magnetic cloud events, instances of shocks propagating through a previous magnetic ejecta or more complex ejecta, when the characteristics of the individual eruptions cannot be easily distinguished. CME - CME interaction is associated with some of the most intense recorded geomagnetic storms. The compression of a CME by another and the propagation of a shock inside a magnetic ejecta can lead to extreme values of the southward magnetic field component, sometimes associated with high values of the dynamic pressure. This can result in intense geomagnetic storms, but can also trigger substorms and large earthward motions of the magnetopause, potentially associated with changes in the outer radiation belts. Future in situ measurements in the inner heliosphere by Solar Probe+ and Solar Orbiter may shed light on the evolution of CMEs as they interact, by providing opportunities for conjunction and evolutionary studies.

Evolution of a Coronal Mass Ejection from the Sun to Mercury, Venus, Earth and Beyond

NASA Astrophysics Data System (ADS)

Wang, Y.; Shen, C.; Liu, J.; Mengjiao, X.; Guo, J.

2017-12-01

A clear magnetic cloud was observed by Messenger at Mercury. By using coronagraph images from SOHO/LASCO and STEREO/COR and the in-situ data from Wind near the Earth, we estimated its propgation velocity and identified the possible CME candidate in the corona and its counterpart recorded by Venus Express near Venus. By applying the CME's DIPS (Deflection in InterPlanetary Space) model, we show that the CME's arrivals at the three different heliocentric distance can be well reproduced. By extending the trajectory of the CME to the orbitor of Mars, we predict the arrival of the CME at Mars, which is in agreement with a significant Forbush decrease observed by MSL. We use uniformly-twisted force-free flux rope model to fit the in-situ measurements at Mercury, Venus and the Earth to study the evolution of the magnetic flux rope, and find that both axial magnetic flux and twist significantly decreased, suggesting that a significant erosion process was on-going and might change the averaged twist of the magnetic flux rope.

Heliocentric Distance of Coronal Mass Ejections at the Time of Energetic Particle Release: Revisiting the Ground Level Enhancement Events of Solar Cycle 23

NASA Technical Reports Server (NTRS)

Gopalswamy, Natchimuthuk

2011-01-01

Using the kinematics of coronal mass ejections (CMEs), onset time of soft X-ray flares, and the finite size of the pre-eruption CME structure, we derive the heliocentric distane at which the energetic particles during the ground level enhancement (GLE) events of Solar Cycle 23. We find that the GLE particles are released when the CMEs reach an average heliocentric distance of approx.3.25 solar radii (Rs). From this we infer that the shocks accelerating the particles are located at similar heights. Type II radio burst observations indicate that the CMEs are at much lower distances (average approx.1.4 Rs) when the CME-driven shock first forms. The shock seems to travel approx.1.8 Rs over a period of approox.30 min on the average before releasing the GLE particles. In deriving these results, we made three assumptions that have observational support: (i) the CME lift off occurs from an initial distance of about 1.25 Rs; (ii) the flare onset and CME onset are one and the same because these are two different manifestations of the same eruption; and (iii) the CME has positive acceleration from the onset to the first appearance in the coronagraphic field of view (2.5 to 6 Rs). Observations of coronal cavities in eclipse pictures and in coronagraphic images justify the assumption (i). The close relationship between the flare reconnection magnetic flux and the azimuthal flux of interplanetary magnetic clouds justify assumption (ii) consistent with the standard model (CSHKP) of solar eruption. Coronagraphic observations made close to the solar surface indicate a large positive acceleration of CMEs to a heliocentric distance of approx.3 Rs before they start slowing down due to the drag force. The inferred acceleration (approx.1.5 km/s/s) is consistent with reported values in the literature.

Reconciling CME Kinematics using Radio and White-light Observations from STEREO and SOHO

NASA Astrophysics Data System (ADS)

Gopalswamy, Nat; Yashiro, Seiji; Xie, Hong; Makela, Pertti; Akiyama, Sachiko; Reiner, Michael; MacDowall, Robert

2014-05-01

We study the characteristics of nonthermal radio emission associated with coronal mass ejections (CMEs) observed by STEREO, SOHO, and Wind spacecraft. In particular, we examine three backside CMEs associated with type II radio bursts at frequencies below 16 MHz. These bursts are known to be excellent indicators of solar energetic particle events. We use the universal drift rate spectrum of type II radio bursts and the inferred density scale heights in the corona and interplanetary medium o estimate the speed of the shock waves that produce the type II radio bursts. We find that the radio bursts can provide an accurate estimate of the CME speeds. We consider three backside events and a cannibalism event to show the usefulness of radio dynamic spectrum in inferring CME kinematics. We use radio direction finding technique to show that CME-CME interaction results in enhanced nonthermal radio emission. The radio data also provide constraints on the particle acceleration mechanisms and the reason for the energetic particles observed at wide-ranging longitudes. Finally we infer the shape and extent of the shock associated with one of the biggest solar energetic particle events in the space era.

Data-driven Simulations of Magnetic Connectivity in Behind-the-Limb Gamma-ray Flares and Associated Coronal Mass Ejections

NASA Astrophysics Data System (ADS)

Jin, M.; Petrosian, V.; Liu, W.; Nitta, N.; Omodei, N.; Rubio da Costa, F.; Effenberger, F.; Li, G.; Pesce-Rollins, M.

2017-12-01

Recent Fermi detection of high-energy gamma-ray emission from the behind-the-limb (BTL) solar flares pose a puzzle on the particle acceleration and transport mechanisms in such events. Due to the large separation between the flare site and the location of gamma-ray emission, it is believed that the associated coronal mass ejections (CMEs) play an important role in accelerating and subsequently transporting particles back to the Sun to produce obseved gamma-rays. We explore this scenario by simulating the CME associated with a well-observed flare on 2014 September 1 about 40 degrees behind the east solar limb and by comparing the simulation and observational results. We utilize a data-driven global magnetohydrodynamics model (AWSoM: Alfven-wave Solar Model) to track the dynamical evolution of the global magnetic field during the event and investigate the magnetic connectivity between the CME/CME-driven shock and the Fermi emission region. Moreover, we derive the time-varying shock parameters (e.g., compression ratio, Alfven Mach number, and ThetaBN) over the area that is magnetically connected to the visible solar disk where Fermi gamma-ray emission originates. Our simulation shows that the visible solar disk develops connections both to the flare site and to the CME-driven shock during the eruption, which indicate that the CME's interaction with the global solar corona is critical for understanding such Fermi BTL events and gamma-ray flares in general. We discuss the causes and implications of Fermi BTL events, in the framework of a potential shift of paradigm on particle acceleration in solar flares/CMEs.

The Dependence of Characteristic Times of Gradual SEP Events on Their Associated CME Properties

NASA Astrophysics Data System (ADS)

Pan, Z. H.; Wang, C. B.; Xue, X. H.; Wang, Y. M.

It is generally believed that coronal mass ejections CMEs are the drivers of shocks that accelerate gradual solar energetic particles SEPs One might expect that the characteristics of the SEP intensity time profiles observed at 1 AU are determined by properties of the associated CMEs such as the radial speed and the angular width Recently Kahler statistically investigated the characteristic times of gradual SEP events observed from 1998-2002 and their associated coronal mass ejection properties Astrophys J 628 1014--1022 2005 Three characteristic times of gradual SEP events are determined as functions of solar source longitude 1 T 0 the time from associated CME launch to SEP onset at 1 AU 2 T R the rise time from SEP onset to the time when the SEP intensity is a factor of 2 below peak intensity and 3 T D the duration over which the SEP intensity is within a factor of 2 of the peak intensity However in his study the CME speeds and angular widths are directly taken from the LASCO CME catalog In this study we analyze the radial speeds and the angular widths of CMEs by an ice-cream cone model and re-investigate their correlationships with the characteristic times of the corresponding SEP events We find T R and T D are significantly correlated with radial speed for SEP events in the best-connected longitude range and there is no correlation between T 0 and CME radial speed and angular width which is consistent with Kahler s results On the other hand it s found that T R and T D are also have

Sun-to-Earth simulations of geo-effective Coronal Mass Ejections with EUHFORIA: a heliospheric-magnetospheric model chain approach

NASA Astrophysics Data System (ADS)

Scolini, C.; Verbeke, C.; Gopalswamy, N.; Wijsen, N.; Poedts, S.; Mierla, M.; Rodriguez, L.; Pomoell, J.; Cramer, W. D.; Raeder, J.

2017-12-01

Coronal Mass Ejections (CMEs) and their interplanetary counterparts are considered to be the major space weather drivers. An accurate modelling of their onset and propagation up to 1 AU represents a key issue for more reliable space weather forecasts, and predictions about their actual geo-effectiveness can only be performed by coupling global heliospheric models to 3D models describing the terrestrial environment, e.g. magnetospheric and ionospheric codes in the first place. In this work we perform a Sun-to-Earth comprehensive analysis of the July 12, 2012 CME with the aim of testing the space weather predictive capabilities of the newly developed EUHFORIA heliospheric model integrated with the Gibson-Low (GL) flux rope model. In order to achieve this goal, we make use of a model chain approach by using EUHFORIA outputs at Earth as input parameters for the OpenGGCM magnetospheric model. We first reconstruct the CME kinematic parameters by means of single- and multi- spacecraft reconstruction methods based on coronagraphic and heliospheric CME observations. The magnetic field-related parameters of the flux rope are estimated based on imaging observations of the photospheric and low coronal source regions of the eruption. We then simulate the event with EUHFORIA, testing the effect of the different CME kinematic input parameters on simulation results at L1. We compare simulation outputs with in-situ measurements of the Interplanetary CME and we use them as input for the OpenGGCM model, so to investigate the magnetospheric response to solar perturbations. From simulation outputs we extract some global geomagnetic activity indexes and compare them with actual data records and with results obtained by the use of empirical relations. Finally, we discuss the forecasting capabilities of such kind of approach and its future improvements.

ON SUN-TO-EARTH PROPAGATION OF CORONAL MASS EJECTIONS: II. SLOW EVENTS AND COMPARISON WITH OTHERS

DOE Office of Scientific and Technical Information (OSTI.GOV)

Liu, Ying D.; Hu, Huidong; Wang, Chi

As a follow-up study on Sun-to-Earth propagation of fast coronal mass ejections (CMEs), we examine the Sun-to-Earth characteristics of slow CMEs combining heliospheric imaging and in situ observations. Three events of particular interest, the 2010 June 16, 2011 March 25, and 2012 September 25 CMEs, are selected for this study. We compare slow CMEs with fast and intermediate-speed events, and obtain key results complementing the attempt of Liu et al. to create a general picture of CME Sun-to-Earth propagation: (1) the Sun-to-Earth propagation of a typical slow CME can be approximately described by two phases, a gradual acceleration out tomore » about 20–30 solar radii, followed by a nearly invariant speed around the average solar wind level; (2) comparison between different types of CMEs indicates that faster CMEs tend to accelerate and decelerate more rapidly and have shorter cessation distances for the acceleration and deceleration; (3) both intermediate-speed and slow CMEs would have speeds comparable to the average solar wind level before reaching 1 au; (4) slow CMEs have a high potential to interact with other solar wind structures in the Sun–Earth space due to their slow motion, providing critical ingredients to enhance space weather; and (5) the slow CMEs studied here lack strong magnetic fields at the Earth but tend to preserve a flux-rope structure with an axis generally perpendicular to the radial direction from the Sun. We also suggest a “best” strategy for the application of a triangulation concept in determining CME Sun-to-Earth kinematics, which helps to clarify confusions about CME geometry assumptions in the triangulation and to improve CME analysis and observations.« less

Empirical Reconstruction and Numerical Modeling of the First Geoeffective Coronal Mass Ejection of Solar Cycle 24

NASA Astrophysics Data System (ADS)

Wood, B. E.; Wu, C.-C.; Howard, R. A.; Socker, D. G.; Rouillard, A. P.

2011-03-01

We analyze the kinematics and morphology of a coronal mass ejection (CME) from 2010 April 3, which was responsible for the first significant geomagnetic storm of solar cycle 24. The analysis utilizes coronagraphic and heliospheric images from the two STEREO spacecraft, and coronagraphic images from SOHO/LASCO. Using an empirical three-dimensional (3D) reconstruction technique, we demonstrate that the CME can be reproduced reasonably well at all times with a 3D flux rope shape, but the case for a flux rope being the correct interpretation is not as strong as some events studied with STEREO in the past, given that we are unable to infer a unique orientation for the flux rope. A model with an orientation angle of -80° from the ecliptic plane (i.e., nearly N-S) works best close to the Sun, but a model at 10° (i.e., nearly E-W) works better far from the Sun. Both interpretations require the cross section of the flux rope to be significantly elliptical rather than circular. In addition to our empirical modeling, we also present a fully 3D numerical MHD model of the CME. This physical model appears to effectively reproduce aspects of the shape and kinematics of the CME's leading edge. It is particularly encouraging that the model reproduces the amount of interplanetary deceleration observed for the CME during its journey from the Sun to 1 AU.

Hot plasma associated with a coronal mass ejection

DOE Office of Scientific and Technical Information (OSTI.GOV)

Landi, E.; Miralles, M. P.; Raymond, J. C.

2013-11-20

We analyze coordinated observations from the EUV Imaging Spectrometer (EIS) and X-Ray Telescope (XRT) on board Hinode of an X-ray Plasma Ejection (XPE) that occurred during the coronal mass ejection (CME) event of 2008 April 9. The XPE was trailing the CME core from behind, following the same trajectory, and could be identified both in EIS and XRT observations. Using the EIS spectrometer, we have determined the XPE plasma parameters, measuring the electron density, thermal distribution, and elemental composition. We have found that the XPE composition and electron density were very similar to those of the pre-event active region plasma.more » The XPE temperature was higher, and its thermal distribution peaked at around 3 MK; also, typical flare lines were absent from EIS spectra, indicating that any XPE component with temperatures in excess of 5 MK was likely either faint or absent. We used XRT data to investigate the presence of hotter plasma components in the XPE that could have gone undetected by EIS and found that—if at all present—these components have small emission measure values and their temperature is in the 8-12.5 MK range. The very hot plasma found in earlier XPE observations obtained by Yohkoh seems to be largely absent in this CME, although plasma ionization timescales may lead to non-equilibrium ionization effects that could make bright lines from ions formed in a 10 MK plasma not detectable by EIS. Our results supersede the XPE findings of Landi et al., who studied the same event with older response functions for the XRT Al-poly filter; the differences in the results stress the importance of using accurate filter response functions.« less

USING ForeCAT DEFLECTIONS AND ROTATIONS TO CONSTRAIN THE EARLY EVOLUTION OF CMEs

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kay, C.; Opher, M.; Colaninno, R. C.

2016-08-10

To accurately predict the space weather effects of the impacts of coronal mass ejection (CME) at Earth one must know if and when a CME will impact Earth and the CME parameters upon impact. In 2015 Kay et al. presented Forecasting a CME’s Altered Trajectory (ForeCAT), a model for CME deflections based on the magnetic forces from the background solar magnetic field. Knowing the deflection and rotation of a CME enables prediction of Earth impacts and the orientation of the CME upon impact. We first reconstruct the positions of the 2010 April 8 and the 2012 July 12 CMEs frommore » the observations. The first of these CMEs exhibits significant deflection and rotation (34° deflection and 58° rotation), while the second shows almost no deflection or rotation (<3° each). Using ForeCAT, we explore a range of initial parameters, such as the CME’s location and size, and find parameters that can successfully reproduce the behavior for each CME. Additionally, since the deflection depends strongly on the behavior of a CME in the low corona, we are able to constrain the expansion and propagation of these CMEs in the low corona.« less

The February 15 2011 CME-CME interaction and possibly associated radio emission

NASA Astrophysics Data System (ADS)

Magdalenic, Jasmina; Temmer, Manuela; Krupar, Vratislav; Marque, Christophe; Veronig, Astrid; Eastwood, Jonathan

2017-04-01

On February 15, 2011 a particular, continuum-like radio emission was observed by STEREO WAVES and WIND WAVES spacecraft. The radio event appeared to be associated with the complex interaction of two coronal mass ejections (CMEs) successively launched (February 14 and February 15) from the same active region. Although the CME-CME interaction was widely studied (e.g. Temmer et al., 2014, Maricic et al., 2014, Mishra & Srivastava, 2014) none of the analyses confirmed an association with the continuum-like radio emission. The usual method of establishing temporal coincidence of radio continuum and a CME-CME interaction is not applicable in this event due to a complex and long-lasting interaction of the CMEs. Therefore, we performed radio triangulation studies (see also Magdalenic et al., 2014) which provided us with the 3D source positions of the radio emission. Comparison of the positions of radio sources and the reconstructed positions of the interacting CMEs, shows that the source position of the continuum-like radio emission is about 0.5 AU away from the interacting CMEs. We can therefore concluded that, in this event, the continuum-like emission is not the radio signature of the CME-CME interaction.

Wide and Narrow CMEs and Their Source Explosions Observed at the Spring 2003 SOHO-Sun-Ulysses Quadrature

NASA Technical Reports Server (NTRS)

Suess, Steven; Corti, G.; Poletto, G.; Sterling, A.; Moore, R.

2006-01-01

At the time of the spring 2003 Ulysses-SOHO-Sun quadrature, Ulysses was off the East limb of the Sun at 14.5 degrees north latitude and 4.91 AU. LASCO/C2 images show small transient events that originated from near the limb on May 25, 26 and 27 in the north-east quadrant, along with a large Coronal Mass Ejection (CME) that originated from an active region near disk center on May 26. Ulysses data bear clear signatures of the large CME, specifically including an enhanced abundance of highly ionized Fe. SOHO/UVCS spectra at 1.75 solar radii, near the radial direction to Ulysses, give no evidence of emission from high temperature lines, even for the large CME: instead, for the small events, occasional transient high emission in cool lines was observed, such as the CIII 977 Angstrom line usually absent at coronal levels. Each of these events lasted ca. 1 hour or less and never affected lines from ions forming above ca. 106K. Compact eruptions in Helium 304 Angstrom EIT images, related to the small UVCS transients, were observed at the limb of the Sun over the same period. At least one of these surge events produced a narrow CME observed in LASCO/C2. Most probably all these events are compact magnetic explosions (surges/jets, from around a small island of included polarity) which ejected cool material from lower levels. Ulysses data have been analyzed to find evidence of the cool, narrow CME events, but none or little was found. This puzzling scenario, where events seen by UVCS have no in situ counterparts and vice versa, can be partially explained once the region where the large CME originated is recognized as being at the center of the solar disk so that the CME material was actually much further from the Sun than the 1.7 Rsun height of the UVCS slit off the limb. Conversely, the narrow events may simply have missed Ulysses or been too brief for reliable signatures in composition and ionization state. A basic feature demonstrated by these observations is that large magnetic explosions produce wide-angle CMEs whereas compact magnetic explosions produce narrow CMEs. The results show that quadrature observations need some luck to be successfull: that is, events must be in the plane of the sky to allow SOHO/UVCS and Ulysses to sample the same plasma. This will most easily occur in winter 2007 and winter 2008, when the quadrature geometry will allow for prolonged observations.

Interplanetary Propagation Behavior of the Fast Coronal Mass Ejection on 23 July 2012

NASA Astrophysics Data System (ADS)

Temmer, M.; Nitta, N. V.

2015-03-01

The fast coronal mass ejection (CME) on 23 July 2012 caused attention because of its extremely short transit time from the Sun to 1 AU, which was shorter than 21 h. In situ data from STEREO-A revealed the arrival of a fast forward shock with a speed of more than 2200 km s-1 followed by a magnetic structure moving with almost 1900 km s-1. We investigate the propagation behavior of the CME shock and magnetic structure with the aim to reproduce the short transit time and high impact speed as derived from in situ data. We carefully measured the 3D kinematics of the CME using the graduated cylindrical shell model and obtained a maximum speed of 2580±280 km s-1 for the CME shock and 2270±420 km s-1 for its magnetic structure. Based on the 3D kinematics, the drag-based model (DBM) reproduces the observational data reasonably well. To successfully simulate the CME shock, the ambient flow speed needs to have an average value close to the slow solar wind speed (450 km s-1), and the initial shock speed at a distance of 30 R ⊙ should not exceed ≈ 2300 km s-1, otherwise it would arrive much too early at STEREO-A. The model results indicate that an extremely small aerodynamic drag force is exerted on the shock, smaller by one order of magnitude than average. As a consequence, the CME hardly decelerates in interplanetary space and maintains its high initial speed. The low aerodynamic drag can only be reproduced when the density of the ambient solar wind flow, in which the fast CME propagates, is decreased to ρ sw=1 - 2 cm-3 at the distance of 1 AU. This result is consistent with the preconditioning of interplanetary space by a previous CME.

Breakout Reconnection Observed by the TESIS EUV Telescope

NASA Astrophysics Data System (ADS)

Reva, A. A.; Ulyanov, A. S.; Shestov, S. V.; Kuzin, S. V.

2016-01-01

We present experimental evidence of the coronal mass ejection (CME) breakout reconnection, observed by the TESIS EUV telescope. The telescope could observe solar corona up to 2 R⊙ from the Sun center in the Fe 171 Å line. Starting from 2009 April 8, TESIS observed an active region (AR) that had a quadrupolar structure with an X-point 0.5 R⊙ above photosphere. A magnetic field reconstructed from the Michelson Doppler Imager data also has a multipolar structure with an X-point above the AR. At 21:45 UT on April 9, the loops near the X-point started to move away from each other with a velocity of ≈7 km s-1. At 01:15 UT on April 10, a bright stripe appeared between the loops, and the flux in the GOES 0.5-4 Å channel increased. We interpret the loops’ sideways motion and the bright stripe as evidence of the breakout reconnection. At 01:45 UT, the loops below the X-point started to slowly move up. At 15:10 UT, the CME started to accelerate impulsively, while at the same time a flare arcade formed below the CME. After 15:50 UT, the CME moved with constant velocity. The CME evolution precisely followed the breakout model scenario.

Deflected Propagation of Coronal Mass Ejections: One of the Key Issues in Space Weather Forecasting

NASA Astrophysics Data System (ADS)

Wang, Y.; Shen, C.; Zhuang, B.; Pan, Z.

2016-12-01

As the most important driver of severe space weather, coronal mass ejections (CMEs) and their geoeffectiveness have been studied intensively. Previous statistical studies have shown that not all the front-side halo CMEs are geoeffective, and not all non-recurrent geomagnetic storms can be tracked back to a CME. These phenomena may cause some failed predictions of the geoeffectiveness of CMEs. The recent notable event exhibiting such a failure was on 2015 March 15 when a fast CME originated from the west hemisphere. Space Weather Prediction Center (SWPC) of NOAA initially forecasted that the CME would at most cause a very minor geomagnetic disturbance labeled as G1. However, the CME produced the largest geomagnetic storm so far, at G4 level with the provisional Dst value of -223 nT, in the current solar cycle 24 [e.g., Kataoka et al., 2015; Wang et al., 2016]. Such an unexpected phenomenon naturally raises the first question for the forecasting of the geoeffectiveness of a CME, i.e., whether or not a CME will hit the Earth even though we know the source location and initial kinematic properties of the CME. A full understanding of the propagation trajectory, e.g., the deflected propagation, of a CME from the Sun to 1 AU is the key. With a few cases, we show the importance of the deflection effect in the space weather forecasting. An automated CME arrival forecasting system containing a deflected propagation model is presented. References:[1] Kataoka, R., D. Shiota, E. Kilpua, and K. Keika, Pileup accident hypothesis of magnetic storm on 17 March 2015, Geophys. Res. Lett., 42, 5155-5161, 2015.[2] Wang, Yuming, Quanhao Zhang, Jiajia Liu, Chenglong Shen, Fang Shen, Zicai Yang, T. Zic, B. Vrsnak, D. F. Webb, Rui Liu, S. Wang, Jie Zhang, Q. Hu, and B. Zhuang, On the Propagation of a Geoeffective Coronal Mass Ejection during March 15 - 17, 2015, J. Geophys. Res., accepted, doi:10.1002/2016JA022924, 2016.

Rapid Acceleration of a Coronal Mass Ejection in the Low Corona and Implications of Propagation

NASA Technical Reports Server (NTRS)

Gallagher, Peter T.; Lawrence, Gareth R.; Dennis, Brian R.

2003-01-01

A high-velocity Coronal Mass Ejection (CME) associated with the 2002 April 21 X1.5 flare is studied using a unique set of observations from the Transition Region and Coronal Explorer (TRACE), the Ultraviolet Coronagraph Spectrometer (UVCS), and the Large-Angle Spectrometric Coronagraph (LASCO). The event is first observed as a rapid rise in GOES X-rays, followed by simultaneous conjugate footpoint brightenings connected by an ascending loop or flux-rope feature. While expanding, the appearance of the feature remains remarkably constant as it passes through the TRACE 195 A passband and LASCO fields-of-view, allowing its height-time behavior to be accurately determined. An analytic function, having exponential and linear components, is found to represent the height-time evolution of the CME in the range 1.05-26 R. The CME acceleration rises exponentially to approx. 900 km/sq s within approximately 20-min, peaking at approx.1400 m/sq s when the leading edge is at approx. 1.7 R. The acceleration subsequently falls off as a slowly varying exponential for approx.,90-min. At distances beyond approx. 3.4 R, the height-time profile is approximately linear with a constant velocity of approx. 2400 km/s. These results are briefly discussed in light of recent kinematic models of CMEs.

Coronal ``Wave'': Magnetic Footprint of a Coronal Mass Ejection?

NASA Astrophysics Data System (ADS)

Attrill, Gemma D. R.; Harra, Louise K.; van Driel-Gesztelyi, Lidia; Démoulin, Pascal

2007-02-01

We investigate the properties of two ``classical'' EUV Imaging Telescope (EIT) coronal waves. The two source regions of the associated coronal mass ejections (CMEs) possess opposite helicities, and the coronal waves display rotations in opposite senses. We observe deep core dimmings near the flare site and also widespread diffuse dimming, accompanying the expansion of the EIT wave. We also report a new property of these EIT waves, namely, that they display dual brightenings: persistent ones at the outermost edge of the core dimming regions and simultaneously diffuse brightenings constituting the leading edge of the coronal wave, surrounding the expanding diffuse dimmings. We show that such behavior is consistent with a diffuse EIT wave being the magnetic footprint of a CME. We propose a new mechanism where driven magnetic reconnections between the skirt of the expanding CME magnetic field and quiet-Sun magnetic loops generate the observed bright diffuse front. The dual brightenings and the widespread diffuse dimming are identified as innate characteristics of this process.

Multi-wave band SMM-VLA observations of an M2 flare and an associated coronal mass ejection

NASA Technical Reports Server (NTRS)

Willson, Robert F.; Lang, Kenneth R.; Schmelz, Joan T.; Gonzalez, Raymond D.; Smith, Kermit L.

1991-01-01

Results are presented of observations of an M2 flare and an associated coronal mass ejection CME by instruments on the SMM as well as by the VLA and other ground-based observatories on September 30, 1988. The multiwave band data show a gradual slowly changing event which lasted several hours. The microwave burst emission was found to originate in compact moderately circularly polarized sources located near the sites of bright H-alpha and soft X-ray emission. These data are combined with estimates of an electron temperature of 1.5 x 10 to the 7th K and an emission measure of about 2.0 x 10 to the 49th/cu cm obtained from Ca XIX and Fe XXV spectra to show that the microwave emission can be attributed to thermal gyrosynchrotron radiation in regions where the magnetic field strength is 425-650 G. The CME acceleration at low altitudes is measured on the basis of ground- and space-based coronagraphs.

Transient Mass-loss Analysis of Solar Observations Using Stellar Methods

DOE Office of Scientific and Technical Information (OSTI.GOV)

Crosley, M. K.; Norman, C.; Osten, R. A.

Low-frequency dynamic spectra of radio bursts from nearby stars offer the best chance to directly detect the stellar signature of transient mass loss on low-mass stars. Crosley et al. (2016) proposes a multi-wavelength methodology to determine coronal mass ejection (CME) parameters, such as speed, mass, and kinetic energy. We test the validity and accuracy of the results derived from the methodology by using Geostationary Operational Environmental Satellite X-ray observations and Bruny Island Radio Spectrometer radio observations. These are analogous observations to those that would be found in the stellar studies. Derived results from these observations are compared to direct whitemore » light measurements of the Large Angle and Spectrometric Coronagraph. We find that, when a pre-event temperature can be determined, the accuracy of CME speeds are within a few hundred km s{sup −1}, and are reliable when specific criteria has been met. CME mass and kinetic energies are only useful in determining the approximate order of magnitude measurements when considering the large errors associated to them. These results will be directly applicable to the interpretation of any detected stellar events and the derivation of stellar CME properties.« less

CME Interaction with Large-Scale Coronal Structures

NASA Technical Reports Server (NTRS)

Gopalswarny, Nat

2012-01-01

This talk presents some key observations that highlight the importance of CME interaction with other large scale structures such as CMEs and coronal holes . Such interactions depend on the phase of the solar cycle: during maximum, CMEs are ejected more frequently, so CME-CME interaction becomes dominant. During the rise phase, the polar coronal holes are strong, so the interaction between polar coronal holes and CMEs is important, which also leads to a possible increase in the number of interplanetary CMEs observed as magnetic clouds. During the declining phase, there are more equatorial coronal holes, so CMEs originating near these coronal holes are easily deflected. CMEs can be deflected toward and away from the Sun-Earth line resulting in interesting geospace consequences. For example, the largest geomagnetic storm of solar cycle 23 was due to a CME that was deflected towards the Sun-earth line from E22. CME deflection away from the Sun-Earth line diminishes the chance of a CME producing a geomagnetic storm. CME interaction in the coronagraphic field of view was first identified using enhanced radio emission, which is an indication of acceleration of low energy (approx.10 keV) electrons in the interaction site. CME interaction, therefore, may also have implications for proton acceleration. For example, solar energetic particle events typically occur with a higher intensity, whenever multiple CMEs occur in quick succession from the same source region. CME deflection may also have implications to the arrival of energetic particles to earth because magnetic connectivity may be changed by the interaction. I illustrate the above points using examples from SOHO, STEREO, Wind, and ACE data .

The Central Role of Tether-Cutting Reconnection in the Production of CMEs

NASA Technical Reports Server (NTRS)

Moore, Ron; Sterling, Alphonse; Suess, Steve

2007-01-01

This viewgraph presentation describes tether-cutting reconnection in the production of Coronal Mass Ejections (CMEs). The topics include: 1) Birth and Release of the CME Plasmoid; 2) Resulting CME in Outer Corona; 3) Governing Role of Surrounding Field; 4) Testable Prediction of the Standard Scenario Magnetic Bubble CME Model; 5) Lateral Pressure in Outer Corona; 6) Measured Angular Widths of 3 CMEs; 7) LASCO Image of each CME at Final Width; 8) Source of the CME of 2002 May 20; 9) Source of the CME of 1999 Feb 9; 10) Source of the CME of 2003 Nov 4; and 11) Test Results.

Homologous Flare-CME Events and Their Metric Type II Radio Burst Association

NASA Technical Reports Server (NTRS)

Yashiro, S.; Gopalswamy, N.; Makela, P.; Akiyama, S.; Uddin, W.; Srivastava, A. K.; Joshi, N. C.; Chandra, R.; Manoharan, P. K.; Mahalakshmi, K.;

Strong coronal channelling and interplanetary evolution of a solar storm up to Earth and Mars

PubMed Central

Möstl, Christian; Rollett, Tanja; Frahm, Rudy A.; Liu, Ying D.; Long, David M.; Colaninno, Robin C.; Reiss, Martin A.; Temmer, Manuela; Farrugia, Charles J.; Posner, Arik; Dumbović, Mateja; Janvier, Miho; Démoulin, Pascal; Boakes, Peter; Devos, Andy; Kraaikamp, Emil; Mays, Mona L.; Vršnak, Bojan

2015-01-01

The severe geomagnetic effects of solar storms or coronal mass ejections (CMEs) are to a large degree determined by their propagation direction with respect to Earth. There is a lack of understanding of the processes that determine their non-radial propagation. Here we present a synthesis of data from seven different space missions of a fast CME, which originated in an active region near the disk centre and, hence, a significant geomagnetic impact was forecasted. However, the CME is demonstrated to be channelled during eruption into a direction +37±10° (longitude) away from its source region, leading only to minimal geomagnetic effects. In situ observations near Earth and Mars confirm the channelled CME motion, and are consistent with an ellipse shape of the CME-driven shock provided by the new Ellipse Evolution model, presented here. The results enhance our understanding of CME propagation and shape, which can help to improve space weather forecasts. PMID:26011032

An empirical model for prediction of geomagnetic storms using initially observed CME parameters at the Sun

NASA Astrophysics Data System (ADS)

Kim, R.-S.; Cho, K.-S.; Moon, Y.-J.; Dryer, M.; Lee, J.; Yi, Y.; Kim, K.-H.; Wang, H.; Park, Y.-D.; Kim, Yong Ha

2010-12-01

In this study, we discuss the general behaviors of geomagnetic storm strength associated with observed parameters of coronal mass ejection (CME) such as speed (V) and earthward direction (D) of CMEs as well as the longitude (L) and magnetic field orientation (M) of overlaying potential fields of the CME source region, and we develop an empirical model to predict geomagnetic storm occurrence with its strength (gauged by the Dst index) in terms of these CME parameters. For this we select 66 halo or partial halo CMEs associated with M-class and X-class solar flares, which have clearly identifiable source regions, from 1997 to 2003. After examining how each of these CME parameters correlates with the geoeffectiveness of the CMEs, we find several properties as follows: (1) Parameter D best correlates with storm strength Dst; (2) the majority of geoeffective CMEs have been originated from solar longitude 15°W, and CMEs originated away from this longitude tend to produce weaker storms; (3) correlations between Dst and the CME parameters improve if CMEs are separated into two groups depending on whether their magnetic fields are oriented southward or northward in their source regions. Based on these observations, we present two empirical expressions for Dst in terms of L, V, and D for two groups of CMEs, respectively. This is a new attempt to predict not only the occurrence of geomagnetic storms, but also the storm strength (Dst) solely based on the CME parameters.

Super- and sub-critical regions in shocks driven by radio-loud and radio-quiet CMEs

PubMed Central

Bemporad, Alessandro; Mancuso, Salvatore

2012-01-01

White-light coronagraphic images of Coronal Mass Ejections (CMEs) observed by SOHO/LASCO C2 have been used to estimate the density jump along the whole front of two CME-driven shocks. The two events are different in that the first one was a “radio-loud” fast CME, while the second one was a “radio quiet” slow CME. From the compression ratios inferred along the shock fronts, we estimated the Alfvén Mach numbers for the general case of an oblique shock. It turns out that the “radio-loud” CME shock is initially super-critical around the shock center, while later on the whole shock becomes sub-critical. On the contrary, the shock associated with the “radio-quiet” CME is sub-critical at all times. This suggests that CME-driven shocks could be efficient particle accelerators at the shock nose only at the initiation phases of the event, if and when the shock is super-critical, while at later times they lose their energy and the capability to accelerate high energetic particles. PMID:25685431

Expanding CME-flare relations to other stellar systems

NASA Astrophysics Data System (ADS)

Moschou, Sofia P.; Drake, Jeremy J.; Cohen, Ofer

2017-05-01

Stellar activity is one of the main parameters in exoplanet habitability studies. While the effects of UV to X-ray emission from extreme flares on exoplanets are beginning to be investigated, the impact of coronal mass ejections is currently highly speculative because CMEs and their properties cannot yet be directly observed on other stars. An extreme superflare was observed in X-rays on the Algol binary system on August 30 1997, emitting a total of energy 1.4x 10^{37} erg and making it a great candidate for studying the upper energy limits of stellar superflares in solar-type (GK) stars. A simultaneous increase and subsequent decline in absorption during the flare was also observed and interpretted as being caused by a CME. Here we investigate the dynamic properties of a CME that could explain such time-dependent absorption and appeal to trends revealed from solar flare and CME statistics as a guide. Using the ice-cream cone model that is extensively used in solar physics to describe the three-dimensional CME structure, in combination with the temporal profile of the hydrogen column density evolution, we are able to characterize the CME and estimate its kinetic energy and mass. We examine the mass, kinetic and flare X-ray fluence in the context of solar relations to examine the extent to which such relations can be extrapolated to much more extreme stellar events.

ON A CORONAL BLOWOUT JET: THE FIRST OBSERVATION OF A SIMULTANEOUSLY PRODUCED BUBBLE-LIKE CME AND A JET-LIKE CME IN A SOLAR EVENT

DOE Office of Scientific and Technical Information (OSTI.GOV)

Shen Yuandeng; Liu Yu; Su Jiangtao

2012-02-01

The coronal blowout jet is a peculiar category among various jet phenomena, in which the sheared base arch, often carrying a small filament, experiences a miniature version of blowout eruption that produces large-scale coronal mass ejection (CME). In this paper, we report such a coronal blowout jet with high-resolution multi-wavelength and multi-angle observations taken from Solar Dynamics Observatory, Solar Terrestrial Relations Observatory, and Big Bear Solar Observatory. For the first time, we find that simultaneous bubble-like and jet-like CMEs were dynamically related to the blowout jet that showed cool and hot components next to each other. Our observational results indicatemore » that (1) the cool component resulted from the eruption of the filament contained within the jet's base arch, and it further caused the bubble-like CME; (2) the jet-like CME was associated with the hot component, which was the outward moving heated plasma generated by the reconnection of the base arch and its ambient open field lines. On the other hand, bifurcation of the jet's cool component was also observed, which resulted from the uncoupling of the erupting filament's two legs that were highly twisted at the very beginning. Based on these results, we propose a model to interpret the coronal blowout jet, in which the external reconnection not only produces the jet-like CME, but also leads to the rising of the filament. Subsequently, internal reconnection starts underneath the rising filament and thereby causes the bubble-like CME.« less

Prediction system of the 1-AU arrival times of CME-associated interplanetary shocks using three-dimensional simulations

NASA Astrophysics Data System (ADS)

den, Mitsue; Amo, Hiroyoshi; Sugihara, Kohta; Takei, Toshifumi; Ogawa, Tomoya; Tanaka, Takashi; Watari, Shinichi

We describe prediction system of the 1-AU arrival times of interplanetary shock waves associated with coromal mass ejections (CMEs). The system is based on modeling of the shock propagation using a three-dimensional adaptive mesh refinement (AMR) code. Once a CME is observed by LASCO/SOHO, firstly ambient solar wind is obtained by numerical simulation, which reproduces the solar wind parameters at that time observed by ACE spacecraft. Then we input the expansion speed and occurrence position data of that CME as initial condtions for an CME model, and 3D simulation of the CME and the shock propagation is perfomed until the shock wave passes the 1-AU. Input the parameters, execution of simulation and output of the result are available on Web, so a person who is not familiar with operation of computer or simulations or is not a researcher can use this system to predict the shock passage time. Simulated CME and shock evolution is visuallized at the same time with simulation and snap shots appear on the web automatically, so that user can follow the propagation. This system is expected to be useful for forecasters of space weather. We will describe the system and simulation model in detail.

Deriving and Constraining 3D CME Kinematic Parameters from Multi-Viewpoint Coronagraph Images

NASA Astrophysics Data System (ADS)

Thompson, B. J.; Mei, H. F.; Barnes, D.; Colaninno, R. C.; Kwon, R.; Mays, M. L.; Mierla, M.; Moestl, C.; Richardson, I. G.; Verbeke, C.

2017-12-01

Determining the 3D properties of a coronal mass ejection using multi-viewpoint coronagraph observations can be a tremendously complicated process. There are many factors that inhibit the ability to unambiguously identify the speed, direction and shape of a CME. These factors include the need to separate the "true" CME mass from shock-associated brightenings, distinguish between non-radial or deflected trajectories, and identify asymmetric CME structures. Additionally, different measurement methods can produce different results, sometimes with great variations. Part of the reason for the wide range of values that can be reported for a single CME is due to the difficulty in determining the CME's longitude since uncertainty in the angle of the CME relative to the observing image planes results in errors in the speed and topology of the CME. Often the errors quoted in an individual study are remarkably small when compared to the range of values that are reported by different authors for the same CME. For example, two authors may report speeds of 700 +- 50 km/sec and 500+-50 km/sec for the same CME. Clearly a better understanding of the accuracy of CME measurements, and an improved assessment of the limitations of the different methods, would be of benefit. We report on a survey of CME measurements, wherein we compare the values reported by different authors and catalogs. The survey will allow us to establish typical errors for the parameters that are commonly used as inputs for CME propagation models such as ENLIL and EUHFORIA. One way modelers handle inaccuracies in CME parameters is to use an ensemble of CMEs, sampled across ranges of latitude, longitude, speed and width. The CMEs simulated in order to determine the probability of a "direct hit" and, for the cases with a "hit," derive a range of possible arrival times. Our study will provide improved guidelines for generating CME ensembles that more accurately sample across the range of plausible values.

Eruptions from the Sun

NASA Astrophysics Data System (ADS)

Kohler, Susanna

2015-11-01

The Sun often exhibits outbursts, launching material from its surface in powerful releases of energy. Recent analysis of such an outburst captured on video by several Sun-monitoring spacecraft may help us understand the mechanisms that launch these eruptions.Many OutburstsSolar jets are elongated, transient structures that are thought to regularly release magnetic energy from the Sun, contributing to coronal heating and solar wind acceleration. Coronal mass ejections (CMEs), on the other hand, are enormous blob-like explosions, violently ejecting energy and mass from the Sun at incredible speeds.But could these two types of events actually be related? According to a team of scientists at the University of Science and Technology of China, they may well be. The team, led by Jiajia Liu, has analyzed observations of a coronal jet that they believe prompted the launch of a powerful CME.Observing an ExplosionGif of a movie of the CME, taken by the Solar Dynamics Observatorys Atmospheric Imaging Assembly at a wavelength of 304. The original movie can be found in the article. [Liu et al.]An army of spacecraft was on hand to witness the event on 15 Jan 2013 including the Solar Dynamics Observatory (SDO), the Solar and Heliospheric Observatory (SOHO), and the Solar Terrestrial Relations Observatory (STEREO). The instruments on board these observatories captured the drama on the northern limb of the Sun as, at 19:32 UT, a coronal jet formed. Just eight minutes later, a powerful CME was released from the same active region.The fact that the jet and CME occurred in the same place at roughly the same time suggests theyre related. But did the initial motions of the CME blob trigger the jet? Or did the jet trigger the CME?Tying It All TogetherIn a recently published study, Liu and collaborators analyzed the multi-wavelength observations of this event to find the heights and positions of the jet and CME. From this analysis, they determined that the coronal jet triggered the release of material to form the CME, which then erupted into space with the jet at its core at speeds of over 1000 km/s.Based on observed clues of the magnetic field configurations, the team has put together a theory for how this event unfolded. They believe that sudden magnetic reconnection in an active region accelerated plasma to form a large-scale coronal jet. This burst of energy also provided a push on a blob of gas, threaded with magnetic field lines, that lay above the jet. The blob then rose, and when the field lines broke, it was released as a CME with the jet at its core.CitationJiajia Liu et al 2015 ApJ 813 115. doi:10.1088/0004-637X/813/2/115

A long-duration active region: Evolution and quadrature observations of ejective events

NASA Astrophysics Data System (ADS)

Cremades, H.; Mandrini, C. H.; Fuentes, M. C. López; Merenda, L.; Cabello, I.; López, F. M.; Poisson, M.

2017-10-01

Unknown aspects of the initiation, evolution, and associated phenomena of coronal mass ejections (CMEs), together with their capability of perturbing the fragile technological equilibrium on which nowadays society depends, turn them a compelling subject of study. While space weather forecasts are thus far not able to predict when and where in the Sun will the next CME take place, various CME triggering mechanisms have been proposed, without reaching consensus on which is the predominant one. To improve our knowledge in these respects, we investigate a long-duration active region throughout its life, from birth until decay along five solar rotations, in connection with its production of ejective events. We benefit from the wealth of solar remote-sensing data with improved temporal, spatial, and spectral resolution provided by the ground-breaking space missions STEREO, SDO, and SOHO. During the investigated time interval, which covers the months July - November 2010, the STEREO spacecraft were nearly 180 degrees apart, allowing for the uninterrupted tracking of the active region and its ensuing CMEs. The ejective aspect is examined from multi-viewpoint coronagraphic images, while the dynamics of the active region photospheric magnetic field are inspected by means of SDO/HMI data for specific subintervals of interest. The ultimate goal of this work in progress is to identify common patterns in the ejective aspect that can be connected with the active region characteristics.

Solar Energetic Particle Warnings from a Coronagraph

NASA Technical Reports Server (NTRS)

St Cyr, O. C.; Posner, A.; Burkepile, J. T.

2017-01-01

We report here the concept of using near-real time observations from a coronagraph to provide early warning of a fast coronal mass ejection (CME) and the possible onset of a solar energetic particle (SEP) event. The 1 January 2016, fast CME, and its associated SEP event are cited as an example. The CME was detected by the ground-based K-Cor coronagraph at Mauna Loa Solar Observatory and by the SOHO Large Angle and Spectrometric Coronagraph. The near-real-time availability of the high-cadence K-Cor observations in the low corona leads to an obvious question: Why has no one attempted to use a coronagraph as an early warning device for SEP events? The answer is that the low image cadence and the long latency of existing spaceborne coronagraphs make them valid for archival studies but typically unsuitable for near-real-time forecasting. The January 2016 event provided favorable CME viewing geometry and demonstrated that the primary component of a prototype ground-based system for SEP warnings is available several hours on most days. We discuss how a conceptual CME-based warning system relates to other techniques, including an estimate of the relative SEP warning times, and how such a system might be realized.

Forbush Decrease Prediction Based on Remote Solar Observations

NASA Astrophysics Data System (ADS)

Dumbovic, Mateja; Vrsnak, Bojan; Calogovic, Jasa

2016-04-01

We study the relation between remote observations of coronal mass ejections (CMEs), their associated solar flares and short-term depressions in the galactic cosmic-ray flux (so called Forbush decreases). Statistical relations between Forbush decrease magnitude and several CME/flare parameters are examined. In general we find that Forbush decrease magnitude is larger for faster CMEs with larger apparent width, which is associated with stronger flares that originate close to the center of the solar disk and are (possibly) involved in a CME-CME interaction. The statistical relations are quantified and employed to forecast expected Forbush decrease magnitude range based on the selected remote solar observations of the CME and associated solar flare. Several verification measures are used to evaluate the forecast method. We find that the forecast is most reliable in predicting whether or not a CME will produce a Forbush decrease with a magnitude >3 %. The main advantage of the method is that it provides an early prediction, 1-4 days in advance. Based on the presented research, an online forecast tool was developed (Forbush Decrease Forecast Tool, FDFT) available at Hvar Observatory web page: http://oh.geof.unizg.hr/FDFT/fdft.php. We acknowledge the support of Croatian Science Foundation under the project 6212 "Solar and Stellar Variability" and of European social fond under the project "PoKRet".

Simulation of the 23 July 2012 Extreme Space Weather Event: What if This Extremely Rare CME Was Earth Directed?

NASA Technical Reports Server (NTRS)

Ngwira, Chigomezyo M.; Pulkkinen, Antti; Mays, M. Leila; Kuznetsova, Maria M.; Galvin, A. B.; Simunac, Kristin; Baker, Daniel N.; Li, Xinlin; Zheng, Yihua; Glocer, Alex

2013-01-01

Extreme space weather events are known to cause adverse impacts on critical modern day technological infrastructure such as high-voltage electric power transmission grids. On 23 July 2012, NASA's Solar Terrestrial Relations Observatory-Ahead (STEREO-A) spacecraft observed in situ an extremely fast coronal mass ejection (CME) that traveled 0.96 astronomical units (approx. 1 AU) in about 19 h. Here we use the SpaceWeather Modeling Framework (SWMF) to perform a simulation of this rare CME.We consider STEREO-A in situ observations to represent the upstream L1 solar wind boundary conditions. The goal of this study is to examine what would have happened if this Rare-type CME was Earth-bound. Global SWMF-generated ground geomagnetic field perturbations are used to compute the simulated induced geoelectric field at specific ground-based active INTERMAGNET magnetometer sites. Simulation results show that while modeled global SYM-H index, a high-resolution equivalent of the Dst index, was comparable to previously observed severe geomagnetic storms such as the Halloween 2003 storm, the 23 July CME would have produced some of the largest geomagnetically induced electric fields, making it very geoeffective. These results have important practical applications for risk management of electrical power grids.

Relationship of EUV Irradiance Coronal Dimming Slope and Depth to Coronal Mass Ejection Speed and Mass

NASA Technical Reports Server (NTRS)

Mason, James Paul; Woods, Thomas N.; Webb, David F.; Thompson, Barbara J.; Colaninno, Robin C.; Vourlidas, Angelos

2016-01-01

Extreme ultraviolet (EUV) coronal dimmings are often observed in response to solar eruptive events. These phenomena can be generated via several different physical processes. For space weather, the most important of these is the temporary void left behind by a coronal mass ejection (CME). Massive, fast CMEs tend to leave behind a darker void that also usually corresponds to minimum irradiance for the cooler coronal emissions. If the dimming is associated with a solar are, as is often the case, the are component of the irradiance light curve in the cooler coronal emission can be isolated and removed using simultaneous measurements of warmer coronal lines. We apply this technique to 37dimming events identified during two separate two-week periods in 2011, plus an event on 2010 August 7 analyzed in a previous paper, to parameterize dimming in terms of depth and slope. We provide statistics on which combination of wavelengths worked best for the flare-removal method, describe the fitting methods applied to the dimming light curves, and compare the dimming parameters with corresponding CME parameters of mass and speed. The best linear relationships found are nu(sub CME) [km/s] approx. equals 2.36 x 10 6 [km/%] x s(sub dim) [%/s] m(sub CME) [g] approx. equals 2.59 x 10(exp.15 [g/%] x the square root of d(sub dim) [%].These relationships could be used for space weather operations of estimating CME mass and speed using near-real-time irradiance dimming measurements.

Current Sheet Evolution In The Aftermath Of A CME Event

NASA Technical Reports Server (NTRS)

Bemporad, A.; Poletto, G.; Seuss, S. T.; Schwardron, N. A.; Elliott, H. A.; Raymond, J. C.

2006-01-01

We report on SOHO UVCS observations of the coronal restructuring following a coronal mass ejection (CME) on 2002 November 26, at the time of a SOHO-Ulysses quadrature campaign. Starting about 1.5 hr after a CME in the northwest quadrant, UVCS began taking spectra at 1.7 R, covering emission from both cool and hot plasma. Observations continued, with occasional gaps, for more than 2 days. Emission in the 974.8 A line of [Fe XVIII], indicating temperatures above 6 x 10(exp 6) K, was observed throughout the campaign in a spatially limited location. Comparison with EIT images shows the [Fe XVIII] emission to overlie a growing post-flare loop system formed in the aftermath of the CME. The emission most likely originates in a current sheet overlying the arcade. Analysis of the [Fe XVIII] emission allows us to infer the evolution of physical parameters in the current sheet over the entire span of our observations: in particular, we give the temperature versus time in the current sheet and estimate its density. At the time of the quadrature, Ulysses was directly above the location of the CME and intercepted the ejecta. High ionization state Fe was detected by the Ulysses SWICS throughout the magnetic cloud associated with the CME, although its rapid temporal variation suggests bursty, rather than smooth, reconnection in the coronal current sheet. The SOHO-Ulysses data set provided us with the unique opportunity of analyzing a current sheet structure from its lowest coronal levels out to its in situ properties. Both the remote and in situ observations are compared with predictions of theoretical CME models.

Automatic Determination of the Conic Coronal Mass Ejection Model Parameters

NASA Technical Reports Server (NTRS)

Pulkkinen, A.; Oates, T.; Taktakishvili, A.

2009-01-01

Characterization of the three-dimensional structure of solar transients using incomplete plane of sky data is a difficult problem whose solutions have potential for societal benefit in terms of space weather applications. In this paper transients are characterized in three dimensions by means of conic coronal mass ejection (CME) approximation. A novel method for the automatic determination of cone model parameters from observed halo CMEs is introduced. The method uses both standard image processing techniques to extract the CME mass from white-light coronagraph images and a novel inversion routine providing the final cone parameters. A bootstrap technique is used to provide model parameter distributions. When combined with heliospheric modeling, the cone model parameter distributions will provide direct means for ensemble predictions of transient propagation in the heliosphere. An initial validation of the automatic method is carried by comparison to manually determined cone model parameters. It is shown using 14 halo CME events that there is reasonable agreement, especially between the heliocentric locations of the cones derived with the two methods. It is argued that both the heliocentric locations and the opening half-angles of the automatically determined cones may be more realistic than those obtained from the manual analysis

Solar flares associated coronal mass ejection accompanied with DH type II radio burst in relation with interplanetary magnetic field, geomagnetic storms and cosmic ray intensity

NASA Astrophysics Data System (ADS)

Chandra, Harish; Bhatt, Beena

2018-04-01

In this paper, we have selected 114 flare-CME events accompanied with Deca-hectometric (DH) type II radio burst chosen from 1996 to 2008 (i.e., solar cycle 23). Statistical analyses are performed to examine the relationship of flare-CME events accompanied with DH type II radio burst with Interplanetary Magnetic field (IMF), Geomagnetic storms (GSs) and Cosmic Ray Intensity (CRI). The collected sample events are divided into two groups. In the first group, we considered 43 events which lie under the CME span and the second group consists of 71 events which are outside the CME span. Our analysis indicates that flare-CME accompanied with DH type II radio burst is inconsistent with CSHKP flare-CME model. We apply the Chree analysis by the superposed epoch method to both set of data to find the geo-effectiveness. We observed different fluctuations in IMF for arising and decay phase of solar cycle in both the cases. Maximum decrease in Dst during arising and decay phase of solar cycle is different for both the cases. It is noted that when flare lie outside the CME span CRI shows comparatively more variation than the flare lie under the CME span. Furthermore, we found that flare lying under the CME span is more geo effective than the flare outside of CME span. We noticed that the time leg between IMF Peak value and GSs, IMF and CRI is on average one day for both the cases. Also, the time leg between CRI and GSs is on average 0 to 1 day for both the cases. In case flare lie under the CME span we observed high correlation (0.64) between CRI and Dst whereas when flare lie outside the CME span a weak correlation (0.47) exists. Thus, flare position with respect to CME span play a key role for geo-effectiveness of CME.

First High-resolution Spectroscopic Observations by IRIS of a Fast, Helical Prominence Eruption Associated with a Coronal Mass Ejection

NASA Astrophysics Data System (ADS)

Liu, W.; De Pontieu, B.; Okamoto, T. J.; Vial, J. C.; Title, A. M.; Antolin, P.; Berger, T. E.; Uitenbroek, H.

2014-12-01

High-resolution spectroscopic observations of prominence eruptions and associated coronal mass ejections (CMEs) are rare but can provide valuable plasma and energy diagnostics. New opportunities have recently become available with the advent of the Interface Region Imaging Spectrograph (IRIS) mission equipped with high resolution of 0.33-0.4 arcsec in space and 1 km/s in velocity, together with the Hinode Solar Optical Telescope of 0.2 arcsec spatial resolution. We report the first result of joint IRIS-Hinode observations of a spectacular prominence eruption occurring on 2014-May-09. IRIS detected a maximum redshift of 450 km/s, which, combined with the plane-of-sky speed of 800 km/s, gives a large velocity vector of 920 km/s at 30 degrees from the sky plane. This direction agrees with the source location at 30 degrees behind the limb observed by STEREO-A and indicates a nearly vertical ejection. We found two branches of redshifts separated by 200 km/s appearing in all strong lines at chromospheric to transition-region temperatures, including Mg II k/h, C II, and Si IV, suggesting a hollow, rather than solid, cone in the velocity space of the ejected material. Opposite blue- and redshifts on the two sides of the prominence exhibit corkscrew variations both in space and time, suggestive of unwinding rotations of a left-handed helical flux rope. Some erupted material returns as nearly streamline flows, exhibiting distinctly narrow line widths (~10 km/s), about 50% of those of the nearby coronal rain at the apexes of coronal loops, where the rain material is initially formed out of cooling condensation. We estimate the mass and kinetic energy of the ejected and returning material and compare them with those of the associated CME. We will discuss the implications of these observations for CME initiation mechanisms.

Using Heliospheric Imaging for Storm Forecasting - SMEI CME Observations as a Tool for Operational Forecasting at AFWA

NASA Astrophysics Data System (ADS)

Webb, D. F.; Johnston, J. C.; Fry, C. D.; Kuchar, T. A.

2008-12-01

Observations of coronal mass ejections (CMEs) from heliospheric imagers such as the Solar Mass Ejection Imager (SMEI) can lead to significant improvements in operational space weather forecasting. We are working with the Air Force Weather Agency (AFWA) to ingest SMEI all-sky imagery with appropriate tools to help forecasters improve their operational space weather forecasts. We describe two approaches: 1) Near- real time analysis of propagating CMEs from SMEI images alone combined with near-Sun observations of CME onsets and, 2) Using these calculations of speed as a mid-course correction to the HAFv2 solar wind model forecasts. HAFv2 became operational at AFWA in late 2006. The objective is to determine a set of practical procedures that the duty forecaster can use to update or correct a solar wind forecast using heliospheric imager data. SMEI observations can be used inclusively to make storm forecasts, as recently discussed in Webb et al. (Space Weather, in press, 2008). We have developed a point-and-click analysis tool for use with SMEI images and are working with AFWA to ensure that timely SMEI images are available for analyses. When a frontside solar eruption occurs, especially if within about 45 deg. of Sun center, a forecaster checks for an associated CME observed by a coronagraph within an appropriate time window. If found, especially if the CME is a halo type, the forecaster checks SMEI observations about a day later, depending on the apparent initial CME speed, for possibly associated CMEs. If one is found, then the leading edge is measured over several successive frames and an elongation-time plot constructed. A minimum of three data points, i.e., over 3-4 orbits or about 6 hours, are necessary for such a plot. Using the solar source location and onset time of the CME from, e.g., SOHO observations, and assuming radial propagation, a distance-time relation is calculated and extrapolated to the 1 AU distance. As shown by Webb et al., the storm onset time is then expected to be about 3 hours after this 1 AU arrival time (AT). The prediction program is updated as more SMEI data become available. Currently when an appropriate solar event occurs, AFWA routinely runs the HAFv2 model to make a forecast of the shock and ejecta arrival times at Earth. SMEI data can be used to improve this prediction. The HAFv2 model can produce synthetic sky maps of predicted CME brightness for comparison with SMEI images. The forecaster uses SMEI imagery to observe and track the CME. The forecaster then measures the CME location and speed using the SMEI imagery and the HAFv2 synthetic sky maps. After comparing the SMEI and HAFv2 results, the forecaster can adjust a key input to HAFv2, such as the initial speed of the disturbance at the Sun or the mid-course speed. The forecaster then iteratively runs HAFv2 until the observed and forecast sky maps match. The final HAFv2 solution becomes the new forecast. When the CME/shock arrives at (or does not reach) Earth, the forecaster verifies the forecast and updates the forecast skill statistics. Eventually, we plan to develop a more automated version of this procedure.

First in-situ observations of exospheric response to CME impact at Mercury

NASA Astrophysics Data System (ADS)

Raines, J. M.; Wallace, K. L.; Sarantos, M.; Jasinski, J. M.; Tracy, P.; Dewey, R. M.; Weberg, M. J.; Slavin, J. A.

2017-12-01

We present the first in-situ observations of enhancements to Mercury's He exosphere generated by CME impact. We analyzed both plasma and magnetic field measurements from the Mercury Surface Space Environment, Geochemistry and Mapping (MESSENGER) spacecraft over a 60-hour period as a coronal mass ejection (CME) passed by the planet. We identified the shock, magnetic cloud and cavity regions of the moderate intensity CME while MESSENGER was in the solar wind. Inside the magnetosphere just after the CME shock passage, we observed a very active dayside magnetosphere, as evident from the high flux plasma parcels passing through the dayside and a broad northern magnetospheric cusp with exceptionally high planetary ion content. All of these signatures indicate substantial reconnection at the dayside magnetopause, making conditions that were excellent for solar wind access to Mercury's surface. The CME appeared to have been particularly enriched in He2+, causing the observed density of solar wind He2+ in the cusp to rise above 0.1 cm-3 and putting it in the top 1% of the over 3200 cusps analyzed. As the low-density CME cavity passed over the planet on the next orbit, the magnetosphere appeared much quieter, with smoother magnetic fields and a smaller, less intense northern cusp but with greatly enhanced He+ content. The elevated He+ observed density continued to increase on subsequent cusp crossings, peaking at 0.1 cm-3 36 hours after CME impact, the highest observed throughout the entire MESSENGER mission. We suggest that the enhancement in He+ indicates an increase to the neutral He exosphere density from the He-enriched CME, a phenomenon observed at the moon, possibly acting as follows: Increased access to the surface from CME-enhanced reconnection, combined with high He2+ flux, enhanced surface implantation. Neutral He atoms were then liberated at an increased rate by surface processes supplying the exosphere, causing a gradual increase in He exosphere density. This led to an increase in He+ abundance through photoionization and charge exchange, which, after acceleration on the dayside, was measured by MESSENGER. These first in-situ observations of exospheric response to CME impact at Mercury have implications for understanding exosphere generation and loss processes, as well space weathering of the planet's surface.

Correlated Flare and CME Energies for the October/November 2003 Events

NASA Technical Reports Server (NTRS)

Dennis, Brian R.; Haga, Leah; Medlin, Drew; Tolbert, A. Kimberly

2006-01-01

We find a strong correlation between the kinetic energies (KEs) of the coronal mass ejections (CMEs) and the radiated energies of the associated solar flares for the events that occurred during the period of intense solar activity between 18 October and 08 November 2003. CME start times, speeds, mass, and KEs were taken from Gopalswamy et al. (2005), who used SOHO/LASCO observations. The GOES observations of the associated flares were analyzed to find the peak SXR flux, the radiated energy in SXRs (L(sub sxr)), and the radiated energy from the SXR emitting plasma across all wavelengths (L(sub hot)). RHESSI observations were also used to find the energy in non-thermal electrons, ions, and the plasma thermal energy for some events. For two events, SORCE/TIM observations of the total solar irradiance during a flare were also available to give the total radiated flare energy (L(sub total)). We find that the total flare energies of the larger events are of the same order of magnitude as the CME KE with a stronger correlation than has been found in the past for other time intervals. The following rule-of-thumb (good to an order of magnitude for the larger events} can be used to relate flare and CME energies: CME KE l(sub total) 10 L(sub hot) 100 L(sub SXR).

Automated LASCO CME Catalog for Solar Cycle 23: Are CMEs Scale Invariant?

NASA Astrophysics Data System (ADS)

Robbrecht, E.; Berghmans, D.; Van der Linden, R. A. M.

2009-02-01

In this paper, we present the first automatically constructed LASCO coronal mass ejection (CME) catalog, a result of the application of the Computer Aided CME Tracking software (CACTus) on the LASCO archive during the interval 1997 September-2007 January. We have studied the CME characteristics and have compared them with similar results obtained by manual detection (CDAW CME catalog). On average, CACTus detects less than two events per day during solar minimum, up to eight events during maximum, nearly half of them being narrow (<20°). Assuming a correction factor, we find that the CACTus CME rate is surprisingly consistent with CME rates found during the past 30 years. The CACTus statistics show that small-scale outflow is ubiquitously observed in the outer corona. The majority of CACTus-only events are narrow transients related to previous CME activity or to intensity variations in the slow solar wind, reflecting its turbulent nature. A significant fraction (about 15%) of CACTus-only events were identified as independent events, thus not related to other CME activity. The CACTus CME width distribution is essentially scale invariant in angular span over a range of scales from 20° to 120° while previous catalogs present a broad maximum around 30°. The possibility that the size of coronal mass outflows follow a power-law distribution could indicate that no typical CME size exists, i.e., that the narrow transients are not different from the larger well defined CMEs.

MODELING THE INITIATION OF THE 2006 DECEMBER 13 CORONAL MASS EJECTION IN AR 10930: THE STRUCTURE AND DYNAMICS OF THE ERUPTING FLUX ROPE

DOE Office of Scientific and Technical Information (OSTI.GOV)

Fan, Yuhong, E-mail: yfan@ucar.edu

2016-06-20

We carry out a 3D magnetohydrodynamic simulation to model the initiation of the coronal mass ejection (CME) on 2006 December 13 in the emerging δ -sunspot active region NOAA 10930. The setup of the simulation is similar to a previous simulation by Fan, but with a significantly widened simulation domain to accommodate the wide CME. The simulation shows that the CME can result from the emergence of a east–west oriented twisted flux rope whose positive, following emerging pole corresponds to the observed positive rotating sunspot emerging against the southern edge of the dominant pre-existing negative sunspot. The erupting flux ropemore » in the simulation accelerates to a terminal speed that exceeds 1500 km s{sup −1} and undergoes a counter-clockwise rotation of nearly 180° such that its front and flanks all exhibit southward directed magnetic fields, explaining the observed southward magnetic field in the magnetic cloud impacting the Earth. With continued driving of flux emergence, the source region coronal magnetic field also shows the reformation of a coronal flux rope underlying the flare current sheet of the erupting flux rope, ready for a second eruption. This may explain the build up for another X-class eruptive flare that occurred the following day from the same region.« less

Two Distinct Types of CME-flare Relationships Based on SOHO and STEREO Observations

DOE Office of Scientific and Technical Information (OSTI.GOV)

Jang, Soojeong; Moon, Yong-Jae; Kim, Rok-Soon

In this paper, we present two distinct types of coronal mass ejection (CME)-flare relationships according to their observing time differences using 107 events from 2010 to 2013. The observing time difference, Δ T , is defined as flare peak time minus CME first appearance time at Solar Terrestrial Relations Observatory ( STEREO ) COR1 field of view. There are 41 events for group A (Δ T < 0) and 66 events for group B (Δ T ≥ 0). We compare CME 3D parameters (speed and kinetic energy) based on multi-spacecraft data ( SOlar and Heliospheric Observatory ( SOHO ) andmore » STEREO A and B ) and their associated flare properties (peak flux, fluence, and duration). Our main results are as follows. First, there are better relationships between CME and flare parameters for group B than that of group A. In particular, CME 3D kinetic energy for group B is well correlated with flare fluence with the correlation coefficient of 0.67, which is much stronger than that (cc = 0.31) of group A. Second, the events belonging to group A have short flare durations of less than 1 hr (mean = 21 minutes), while the events for group B have longer durations up to 4 hr (mean = 81 minutes). Third, the mean value of height at peak speed for group B is 4.05 Rs, which is noticeably higher than that of group A (1.89 Rs). This is well correlated with the CME acceleration duration (cc = 0.75). A higher height at peak speed and a longer acceleration duration of CME for group B could be explained by the fact that magnetic reconnections for group B continuously occur for a longer time than those for group A.« less

Correlation between Angular Widths of CMEs and Characteristics of Their Source Regions

DOE Office of Scientific and Technical Information (OSTI.GOV)

Zhao, X. H.; Feng, X. S.; Feng, H. Q.

The angular width of a coronal mass ejection (CME) is an important factor in determining whether the corresponding interplanetary CME (ICME) and its preceding shock will reach Earth. However, there have been very few studies of the decisive factors of the CME’s angular width. In this study, we use the three-dimensional (3D) angular width of CMEs obtained from the Graduated Cylindrical Shell model based on observations of Solar Terrestrial Relations Observatory ( STEREO ) to study the relations between the CME’s 3D width and characteristics of the CME’s source region. We find that for the CMEs produced by active regionsmore » (ARs), the CME width has some correlations with the AR’s area and flux, but these correlations are not strong. The magnetic flux contained in the CME seems to come from only part of the AR’s total flux. For the CMEs produced by flare regions, the correlations between the CME angular width and the flare region’s area and flux are strong. The magnetic flux within those CMEs seems to come from the whole flare region or even from a larger region than the flare. Our findings show that the CME’s 3D angular width can be generally estimated based on observations of Solar Dynamics Observatory for the CME’s source region instead of the observations from coronagraphs on board the Solar and Heliospheric Observatory and STEREO if the two foot points of the CME stay in the same places with no expansion of the CME in the transverse direction until reaching Earth.« less

Predicting the Magnetic Field of Earth-impacting CMEs

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kay, C.; Gopalswamy, N.; Reinard, A.

Predicting the impact of coronal mass ejections (CMEs) and the southward component of their magnetic field is one of the key goals of space weather forecasting. We present a new model, the ForeCAT In situ Data Observer (FIDO), for predicting the in situ magnetic field of CMEs. We first simulate a CME using ForeCAT, a model for CME deflection and rotation resulting from the background solar magnetic forces. Using the CME position and orientation from ForeCAT, we then determine the passage of the CME over a simulated spacecraft. We model the CME’s magnetic field using a force-free flux rope andmore » we determine the in situ magnetic profile at the synthetic spacecraft. We show that FIDO can reproduce the general behavior of four observed CMEs. FIDO results are very sensitive to the CME’s position and orientation, and we show that the uncertainty in a CME’s position and orientation from coronagraph images corresponds to a wide range of in situ magnitudes and even polarities. This small range of positions and orientations also includes CMEs that entirely miss the satellite. We show that two derived parameters (the normalized angular distance between the CME nose and satellite position and the angular difference between the CME tilt and the position angle of the satellite with respect to the CME nose) can be used to reliably determine whether an impact or miss occurs. We find that the same criteria separate the impacts and misses for cases representing all four observed CMEs.« less

DOE Office of Scientific and Technical Information (OSTI.GOV)

Zheng, Ruisheng; Chen, Yao; Du, Guohui

Jets are defined as impulsive, well-collimated upflows, occurring in different layers of the solar atmosphere with different scales. Their relationship with coronal mass ejections (CMEs), another type of solar impulsive events, remains elusive. Using high-quality imaging data from the Atmospheric Imaging Assembly/Solar Dynamics Observatory, we show a well-observed coronal jet event, in which the part of the jet with embedding coronal loops runs into a nearby coronal hole (CH) and gets bounced in the opposite direction. This is evidenced by the flat shape of the jet front during its interaction with the CH and the V-shaped feature in the time-slicemore » plot of the interaction region. About a half-hour later, a CME with an initially narrow and jet-like front is observed by the LASCO C2 coronagraph propagating along the direction of the post-collision jet. We also observe some 304 Å dark material flowing from the jet–CH interaction region toward the CME. We thus suggest that the jet and the CME are physically connected, with the jet–CH collision and the large-scale magnetic topology of the CH being important in defining the eventual propagating direction of this particular jet–CME eruption.« less

Predicting the magnetic vectors within coronal mass ejections arriving at Earth: 1. Initial architecture

NASA Astrophysics Data System (ADS)

Savani, N. P.; Vourlidas, A.; Szabo, A.; Mays, M. L.; Richardson, I. G.; Thompson, B. J.; Pulkkinen, A.; Evans, R.; Nieves-Chinchilla, T.

2015-06-01

The process by which the Sun affects the terrestrial environment on short timescales is predominately driven by the amount of magnetic reconnection between the solar wind and Earth's magnetosphere. Reconnection occurs most efficiently when the solar wind magnetic field has a southward component. The most severe impacts are during the arrival of a coronal mass ejection (CME) when the magnetosphere is both compressed and magnetically connected to the heliospheric environment. Unfortunately, forecasting magnetic vectors within coronal mass ejections remain elusive. Here we report how, by combining a statistically robust helicity rule for a CME's solar origin with a simplified flux rope topology, the magnetic vectors within the Earth-directed segment of a CME can be predicted. In order to test the validity of this proof-of-concept architecture for estimating the magnetic vectors within CMEs, a total of eight CME events (between 2010 and 2014) have been investigated. With a focus on the large false alarm of January 2014, this work highlights the importance of including the early evolutionary effects of a CME for forecasting purposes. The angular rotation in the predicted magnetic field closely follows the broad rotational structure seen within the in situ data. This time-varying field estimate is implemented into a process to quantitatively predict a time-varying Kp index that is described in detail in paper II. Future statistical work, quantifying the uncertainties in this process, may improve the more heuristic approach used by early forecasting systems.

The Solar Stormwatch CME catalogue: Results from the first space weather citizen science project

NASA Astrophysics Data System (ADS)

Barnard, L.; Scott, C.; Owens, M.; Lockwood, M.; Tucker-Hood, K.; Thomas, S.; Crothers, S.; Davies, J. A.; Harrison, R.; Lintott, C.; Simpson, R.; O'Donnell, J.; Smith, A. M.; Waterson, N.; Bamford, S.; Romeo, F.; Kukula, M.; Owens, B.; Savani, N.; Wilkinson, J.; Baeten, E.; Poeffel, L.; Harder, B.

2014-12-01

Solar Stormwatch was the first space weather citizen science project, the aim of which is to identify and track coronal mass ejections (CMEs) observed by the Heliospheric Imagers aboard the STEREO satellites. The project has now been running for approximately 4 years, with input from >16,000 citizen scientists, resulting in a data set of >38,000time-elongation profiles of CME trajectories, observed over 18 preselected position angles. We present our method for reducing this data set into a CME catalogue. The resulting catalogue consists of 144 CMEs over the period January 2007 to February 2010, of which 110 were observed by STEREO-A and 77 were observed by STEREO-B. For each CME, the time-elongation profiles generated by the citizen scientists are averaged into a consensus profile along each position angle that the event was tracked. We consider this catalogue to be unique, being at present the only citizen science-generated CME catalogue, tracking CMEs over an elongation range of 4° out to a maximum of approximately 70°. Using single spacecraft fitting techniques, we estimate the speed, direction, solar source region, and latitudinal width of each CME. This shows that at present, the Solar Stormwatch catalogue (which covers only solar minimum years) contains almost exclusively slow CMEs, with a mean speed of approximately 350 km s-1. The full catalogue is available for public access at www.met.reading.ac.uk/~spate/solarstormwatch. This includes, for each event, the unprocessed time-elongation profiles generated by Solar Stormwatch, the consensus time-elongation profiles, and a set of summary plots, as well as the estimated CME properties.

The Formation and Early Evolution of a CME and the Associated Shock on 2014 January 8

NASA Astrophysics Data System (ADS)

Wan, Linfeng; Cheng, Xin; Shi, Tong; Su, Wei; Ding, Mingde

2017-08-01

We study the formation and early evolution of a limb coronal mass ejection (CME) and its associated shock wave that occurred on 2014 January 8. The extreme ultraviolet (EUV) images provided by AIA on board \\textit{Solar Dynamics Observatory} disclose that the CME first appears as a bubble-like structure. Subsequently, its expansion forms the CME and causes a quasi-circular EUV wave. Both the CME and the wave front are clearly visible at all of the AIA EUV passbands. Through a detailed kinematical analysis, it is found that the expansion of the CME undergoes two phases: a first phase with a strong but transient lateral over-expansion followed by a second phase with a self-similar expansion. The temporal evolution of the expansion velocity coincides very well with the variation of the 25--50 keV hard X-ray (HXR) flux of the associated flare, which indicates that magnetic reconnection most likely plays an important role in driving the expansion. Moreover, we find that, when the velocity of the CME reaches $\\sim$600 km s$^{-1}$, the EUV wave starts to evolve into a shock wave, which is evidenced by the appearance of a type II radio burst. Interestingly, we also notice an unusual solar radio signal at $\\sim$4 GHz that is similar to the pattern of a type II radio burst but drifts to higher frequencies at a rate of $\\sim$0.3 MHz per second during about 7 minutes. Its derived density is $\\sim$5$\\times$10$^{10}$ cm$^{-3}$ and increases slowly with time. Joint imaging observations of HXR and EUV help to locate the loop-top region and calculate its thermal proprieties, including slowly increasing densities ($\\sim$5$\\times$10$^{10}$ cm$^{-3}$) and temperatures ($\\sim$14 MK). The similar results obtained from two different ways above imply the possibility of this scenario: plasma blobs that are ejected along the current sheet via magnetic reconnection collide with underlying flare loops that are undergoing chromospheric evaporation. Finally, we also study the thermal properties of the CME and the EUV wave. We find that the plasma in the CME leading front and the wave front has a temperature of $\\sim$2 MK, while that in the CME core region and the flare region has a much higher temperature of $\\ge$8 MK.

Correlation of the Coronal Mass Ejection Productivity of Solar Active Regions with Measures of their Global Nonpotentiality from Vector Magnetograms: Baseline Results

NASA Technical Reports Server (NTRS)

Falconer, D. A.; Moore, R. L.; Gary, G. A.

2002-01-01

Conventional magnetograms and chromospheric and coronal images show qualitatively that the fastest coronal mass ejections (CMEs) are magnetic explosions from sunspot active regions where the magnetic field is globally strongly sheared and twisted from its minimum-energy potential configuration. We present measurements from active region vector magnetograms that start to quantify the dependence of an active region's CME productivity on the global nonpotentiality of its magnetic field. From each of 17 magnetograms of 12 bipolar active regions, we measured the size of the active region (the magnetic flux content, phi) and three separate measures of the global nonpotentiality (L(sub SS), the length of strong-shear, strong-field main neutral line: I(sub N), the net electric current connecting one polarity to the other; and alpha = (mu)I(sub N)/phi), a flux normalized measure of the field twist). From these measurements and the observed CME productivity of the active regions, we find that: (1) All three measures of global nonpotentiality are statistically correlated with the active region flux content and with each other; (2) All three measures of global nonpotentiality are significantly correlated with CME productivity. The flux content correlates with CME productivity, but at a lower statistically significant confidence level (less than 95%); (3) The net current is less closely correlated with CME productivity than alpha and the correlation of CME productivity with flux content is even weaker. If these differences in correlation strength, and a significant correlation of alpha with flux content, persist to larger active regions, this would imply that the size of active regions does not affect CME productivity except through global nonpotentiality; and (4) For each of the four global magnetic quantities, the correlation with CME productivity is stronger for a two-day time window for the CME production than for windows half as wide or twice as wide. This plausibly is a result of the most counterproductive active regions producing less than one CME per day, and from the active region's evolution often significantly changing the global nonpotentiality over the course of several days. These results establish that measures of active region global nonpotentiality from vector magnetograms (such as L(sub SS), I(sub N), and alpha) should be useful for prediction a active region CMEs.

The Expansion and Radial Speeds of Coronal Mass Ejections

NASA Astrophysics Data System (ADS)

Gopalswamy, N.; Dal Lago, A.; Yashiro, S.; Akiyama, S.

We show the relation between radial (V_{rad}) and expansion (V_{exp}) speeds of coronal mass ejections (CMEs) depends on the CME width. As CME width increases, {V_{rad}/V_{exp}} decreases from a value >1 to <1. For widths approaching 180°, the ratio approaches 0 if the cone has a flat base, while it approaches 0.5 if the base has a bulge (ice cream cone). The speed difference between the limb and disk halos and the spherical expansion of super fast CMEs can be explained by the width dependence.

Active Longitude and Coronal Mass Ejection Occurrences

DOE Office of Scientific and Technical Information (OSTI.GOV)

Gyenge, N.; Kiss, T. S.; Erdélyi, R.

The spatial inhomogeneity of the distribution of coronal mass ejection (CME) occurrences in the solar atmosphere could provide a tool to estimate the longitudinal position of the most probable CME-capable active regions in the Sun. The anomaly in the longitudinal distribution of active regions themselves is often referred to as active longitude (AL). In order to reveal the connection between the AL and CME spatial occurrences, here we investigate the morphological properties of active regions. The first morphological property studied is the separateness parameter, which is able to characterize the probability of the occurrence of an energetic event, such asmore » a solar flare or CME. The second morphological property is the sunspot tilt angle. The tilt angle of sunspot groups allows us to estimate the helicity of active regions. The increased helicity leads to a more complex buildup of the magnetic structure and also can cause CME eruption. We found that the most complex active regions appear near the AL and that the AL itself is associated with the most tilted active regions. Therefore, the number of CME occurrences is higher within the AL. The origin of the fast CMEs is also found to be associated with this region. We concluded that the source of the most probably CME-capable active regions is at the AL. By applying this method, we can potentially forecast a flare and/or CME source several Carrington rotations in advance. This finding also provides new information for solar dynamo modeling.« less

Active Longitude and Coronal Mass Ejection Occurrences

NASA Astrophysics Data System (ADS)

Gyenge, N.; Singh, T.; Kiss, T. S.; Srivastava, A. K.; Erdélyi, R.

2017-03-01

The spatial inhomogeneity of the distribution of coronal mass ejection (CME) occurrences in the solar atmosphere could provide a tool to estimate the longitudinal position of the most probable CME-capable active regions in the Sun. The anomaly in the longitudinal distribution of active regions themselves is often referred to as active longitude (AL). In order to reveal the connection between the AL and CME spatial occurrences, here we investigate the morphological properties of active regions. The first morphological property studied is the separateness parameter, which is able to characterize the probability of the occurrence of an energetic event, such as a solar flare or CME. The second morphological property is the sunspot tilt angle. The tilt angle of sunspot groups allows us to estimate the helicity of active regions. The increased helicity leads to a more complex buildup of the magnetic structure and also can cause CME eruption. We found that the most complex active regions appear near the AL and that the AL itself is associated with the most tilted active regions. Therefore, the number of CME occurrences is higher within the AL. The origin of the fast CMEs is also found to be associated with this region. We concluded that the source of the most probably CME-capable active regions is at the AL. By applying this method, we can potentially forecast a flare and/or CME source several Carrington rotations in advance. This finding also provides new information for solar dynamo modeling.

Global MHD Simulation of the Coronal Mass Ejection on 2011 March 7: from Chromosphere to 1 AU

NASA Astrophysics Data System (ADS)

Jin, M.; Manchester, W.; van der Holst, B.; Oran, R.; Sokolov, I.; Toth, G.; Vourlidas, A.; Liu, Y.; Sun, X.; Gombosi, T. I.

2013-12-01

In this study, we present magnetohydrodynamics simulation results of a fast CME event that occurred on 2011 March 7 by using the newly developed Alfven Wave Solar Model (AWSoM) in Space Weather Modeling Framework (SWMF). The background solar wind is driven by Alfven-wave pressure and heated by Alfven-wave dissipation in which we have incorporated balanced turbulence at the top of the closed field lines. The magnetic field of the inner boundary is specified with a synoptic magnetogram from SDO/HMI. In order to produce the physically correct CME structures and CME-driven shocks, the electron and proton temperatures are separated so that the electron heat conduction is explicitly treated in conjunction with proton shock heating. Also, collisionless heat conduction is implemented for getting the correct electron temperature at 1 AU. We initiate the CME by using the Gibson-Low flux rope model and simulate the CME propagation to 1 AU. A comprehensive validation study is performed using remote as well as in-situ observations from SOHO, STEREOA/B, ACE, and WIND. Our result shows that the new model can reproduce most of the observed features and the arrival time of the CME is correctly estimated, which suggests the forecasting capability of the new model. We also examine the simulated CME-driven shock structures that are important for modeling the associated solar energetic event (SEP) with diffusive shock acceleration.

The symmetry and mass of halo Coronal Mass Ejections (CMEs) as quantitative predictors for severe space weather at Earth.

NASA Astrophysics Data System (ADS)

Fuselier, S.; Allegrini, F.; Bzowski, M.; Dayeh, M. A.; Desai, M. I.; Funsten, H. O.; Galli, A.; Heirtzler, D.; Janzen, P. H.; Kubiak, M. A.; Kucharek, H.; Lewis, W. S.; Livadiotis, G.; McComas, D. J.; Moebius, E.; Petrinec, S. M.; Quinn, M. S.; Schwadron, N.; Sokol, J. M.; Trattner, K. J.

2014-12-01

The Bureau of Meteorology's Space Weather Service operates an alert service for severe space weather events. The service relies on a statistical model which ingests observations of M and X class solar flares at or shortly after the time of the flare to predict the occurrence and severity of terrestrial impacts with a lead time of 1 to 4 days. This model has been operational since 2012 and caters to the needs of critical infrastructure groups in the Australian region. This paper reports on improvements to the forecast model by including SOHO LASCO coronagraph observations of Coronal Mass Ejections (CMEs). The coronagraphs are analysed to determine the Earthward direction parameter and the integrated intensity as a measure of the CME mass. Both of these parameters can help to predict whether a CME will be geo-effective. This work aims to increase the accuracy of the model predictions and lower the rate of false positives, as well as providing an estimate of the expected level of geomagnetic storm intensity.

The symmetry and mass of halo Coronal Mass Ejections (CMEs) as quantitative predictors for severe space weather at Earth.

NASA Astrophysics Data System (ADS)

Freeland, L. E.; Terkildsen, M. B.

2015-12-01

The Bureau of Meteorology's Space Weather Service operates an alert service for severe space weather events. The service relies on a statistical model which ingests observations of M and X class solar flares at or shortly after the time of the flare to predict the occurrence and severity of terrestrial impacts with a lead time of 1 to 4 days. This model has been operational since 2012 and caters to the needs of critical infrastructure groups in the Australian region. This paper reports on improvements to the forecast model by including SOHO LASCO coronagraph observations of Coronal Mass Ejections (CMEs). The coronagraphs are analysed to determine the Earthward direction parameter and the integrated intensity as a measure of the CME mass. Both of these parameters can help to predict whether a CME will be geo-effective. This work aims to increase the accuracy of the model predictions and lower the rate of false positives, as well as providing an estimate of the expected level of geomagnetic storm intensity.

Solar-Storm/Lunar Atmosphere Model (SSLAM): An Overview of the Effort and Description of the Driving Storm Environment

NASA Technical Reports Server (NTRS)

Farrell, W. M.; Halekas, J. S.; Killen, R. M.; Delroy, G. T.; Gross, N.; Bleacher, V; Krauss-Varben, D.; Hurley, D; Zimmerman, M. I.

2012-01-01

On 29 April 1998, a coronal mass ejection (CME) was emitted from the Sun that had a significant impact on bodies located at 1 AU. The terrestrial magnetosphere did indeed become more electrically active during the storm passage but an obvious question is the effect of such a storm on an exposed rocky body like our Moon. The solar-storm/lunar atmosphere modeling effort (SSLAM) brings together surface interactions, exosphere, plasma, and surface charging models all run with a common driver - the solar storm and CME passage occurring from 1-4 May 1998. We present herein an expanded discussion on the solar driver during the 1-4 May 1998 period that included the passage of an intense coronal mass ejection (CME) that had> 10 times the solar wind density and had a compositional component of He++ that exceeded 20%. We also provide a very brief overview oflhe SSLAM system layout and overarching results. One primary result is that the CME driver plasma can greatly increase the exospheric content via sputtering, with total mass loss rates that approach 1 kg/s during the 2-day CME passage. By analogy, we suggest that CME-related sputtering increases might also be expected during a CME passage by a near-earth asteroid or at the Mars exobase, resulting in an enhanced loss of material.

Why a geoeffective CME was missed by SOHO LASCO?

NASA Astrophysics Data System (ADS)

Chi, Y.; Zhang, J.; Shen, C.; Hess, P.; Feng, L.; Wang, Y.; Mishra, W.

2017-12-01

During 2011 May 25, two Earth directed coronal mass ejections (CMEs) were recorded by STEREO COR2 as limb CMEs, when the separation between twin STEREO spacecraft and Earth was approximately 90°. At the same time, SOHO LASCO did not record corresponding halo or partial halo CME. These CMEs provided an opportunity to study why SOHO LASCO may miss Earth direction CME. According to GCS model, we find the two CMEs both have small half angle and aspect ratio. Most part of CMEs are behind the occulter of SOHO LASCO C2. We also estimated the two CMEs' mass and find the both CMEs' mass is small. The expected CME brightness according to the CME's mass is in the same order of the noise of SOHO LASCO. In the HI1 Fov, We have found evidence of interaction between the two CMEs. Combining with the WIND in situ observations, we find the CMEs are adjacent to each other. The duration of the two flux rope structure are 7 and 6.6 hours, respectively. This may provide an evidence that small flux structure without corresponding CME is also the solar erupted structure.

Prediction of SEP Peak Proton Intensity Based on CME Speed, Direction and Observations of Associated Solar Phenomena

NASA Astrophysics Data System (ADS)

Richardson, I. G.; Mays, M. L.; Thompson, B. J.; Kwon, R.; Frechette, B. P.

2017-12-01

We assess whether a formula obtained by Richardson et al. (Solar Phys., 289, 3059, 2014; DOI 10.1007/s11207-014-0524-8) relating the intensity of 14-24 MeV protons in a solar energetic particle event at 1 AU to the solar event location and the speed of the associated coronal mass ejection (CME), may be used to "predict" the intensity of a solar energetic particle event. Starting with a subset of several hundred CMEs in the CCMC/SWRC DONKI real-time database (http://kauai.ccmc.gsfc.nasa.gov/DONKI/) selected without consideration of whether they were associated with SEP events, we first use the CME speed and direction to predict the proton intensity at Earth or the STEREO spacecraft using this formula. Since most of these CMEs were not in fact associated with SEP events, many "false alarms" result. We then examine whether considering other phenomena which may accompany the CMEs, such as the X-ray flare intensity and the properties of type II and type III radio emissions, may help to reduce the false alarm rate. We also use CME parameters calculated from an ellipsoidal shell fit to multi-spacecraft CME shock observations for a smaller number of events to predict the SEP intensity. We calculate skill scores for each case and assess whether the Richardson et al. (2014) formula, using additional observations to reduce the false alarm rate, has any potential as a SEP prediction tool, assuming that the required observations could be acquired sufficiently rapidly following the onset of the related solar event/CME.

Solar and interplanetary activities of isolated and non-isolated coronal mass ejections

NASA Astrophysics Data System (ADS)

Bendict Lawrance, M.; Shanmugaraju, A.; Moon, Y.-J.; Umapathy, S.

2017-07-01

We report our results on comparison of two halo Coronal Mass Ejections (CME) associated with X-class flares of similar strength (X1.4) but quite different in CME speed and acceleration, similar geo-effectiveness but quite different in Solar Energetic Particle (SEP) intensity. CME1 (non-isolated) was associated with a double event in X-ray flare and it was preceded by another fast halo CME of speed = 2684 km/s (pre-CME) associated with X-ray flare class X5.4 by 1 h from the same location. Since this pre-CME was more eastern, interaction with CME1 and hitting the earth were not possible. This event (CME1) has not suffered the cannibalism since pre-CME has faster speed than post-CME. Pre-CME plays a very important role in increasing the intensity of SEP and Forbush Decrease (FD) by providing energetic seed particles. So, the seed population is the major difference between these two selected events. CME2 (isolated) was a single event. We would like to address on the kinds of physical conditions related to such CMEs and their associated activities. Their associated activities such as, type II bursts, SEP, geomagnetic storm and FD are compared. The following results are obtained from the analysis. (1) The CME leading edge height at the start of metric/DH type II bursts are 2 R⊙/ 4 R⊙ for CME1, but 2 R⊙/ 2.75 R⊙ for CME2. (2) Peak intensity of SEP event associated with the two CMEs are quite different: 6530 pfu for CME1, but 96 pfu for CME2. (3) The Forbush decrease occurred with a minimum decrease of 9.98% in magnitude for CME1, but 6.90% for CME2. (4) These two events produced similar intense geomagnetic storms of intensity of Dst index -130 nT. (5) The maximum southward magnetic fields corresponding to Interplanetary CME (ICME) of these two events are nearly the same, but there is difference in Sheath Bz maximum (-14.2, -6.9 nT). (6) The time-line chart of the associated activities of two CMEs show some difference in the time delay between the onsets of activities with respect to the onset of flare/CME.

Is There a CME Rate Floor? CME and Magnetic Flux Values for the Last Four Solar Cycle Minima

NASA Astrophysics Data System (ADS)

Webb, D. F.; Howard, R. A.; St. Cyr, O. C.; Vourlidas, A.

2017-12-01

The recent prolonged activity minimum has led to the question of whether there is a base level of the solar magnetic field evolution that yields a “floor” in activity levels and also in the solar wind magnetic field strength. Recently, a flux transport model coupled with magneto-frictional simulations has been used to simulate the continuous magnetic field evolution in the global solar corona for over 15 years, from 1996 to 2012. Flux rope eruptions in the simulations are estimated (Yeates), and the results are in remarkable agreement with the shape of the SOlar Heliospheric Observatory/Large Angle and Spectrometric Coronagraph Experiment coronal mass ejection (CME) rate distribution. The eruption rates at the two recent minima approximate the observed-corrected CME rates, supporting the idea of a base level of solar magnetic activity. In this paper, we address this issue by comparing annual averages of the CME occurrence rates during the last four solar cycle minima with several tracers of the global solar magnetic field. We conclude that CME activity never ceases during a cycle, but maintains a base level of 1 CME every 1.5 to ∼3 days during minima. We discuss the sources of these CMEs.

Magnetic Causes of Solar Coronal Mass Ejections: Dominance of the Free Magnetic Energy Over the Magnetic Twist Alone

NASA Technical Reports Server (NTRS)

Falconer, D. A.; Moore, R. L.; Gary, g. A.

2006-01-01

We examine the magnetic causes of coronal mass ejections (CMEs) by examining, along with the correlations of active-region magnetic measures with each other, the correlations of these measures with active-region CME productivity observed in time windows of a few days, either centered on or extending forward from the day of the magnetic measurement. The measures are from 36 vector magnetograms of bipolar active regions observed within -30" of disk center by the Marshal Space Flight Center (MSFC) vector magnetograph. From each magnetogram, we extract six whole-active-region measures twice, once from the original plane-of-the-sky magnetogram and again a h r deprojection of the magnetogram to disk center. Three of the measures are alternative measures of the total nonpotentiality of the active region, two are alternative measures of the overall twist in the active-region's magnetic field, and one is a measure of the magnetic size of the active region (the active region's magnetic flux content). From the deprojected magnetograms, we find evidence that (1) magnetic twist and magnetic size are separate but comparably strong causes of active-region CME Productivity, and (2) the total free magnetic energy in an active region's magnetic field is a stronger determinant of the active region's CME productivity than is the field's overall twist (or helicity) alone. From comparison of results from the non-deprojected magnetograms with corresponding results from the deprojected magnetograms, we find evidence that (for prediction of active-region CME productivity and for further studies of active-region magnetic size as a cause of CMEs), for active regions within approx.30deg of disk center, active-region total nonpotentiality and flux content can be adequately measured from line-of-sight magnetograms, such as from SOH0 MDI.

Development and Parameters of a Non-Self-Similar CME Caused by the Eruption of a Quiescent Prominence

NASA Astrophysics Data System (ADS)

Kuzmenko, I. V.; Grechnev, V. V.

2017-10-01

The eruption of a large quiescent prominence on 17 August 2013 and an associated coronal mass ejection (CME) were observed from different vantage points by the Solar Dynamics Observatory (SDO), the Solar-Terrestrial Relations Observatory (STEREO), and the Solar and Heliospheric Observatory (SOHO). Screening of the quiet Sun by the prominence produced an isolated negative microwave burst. We estimated the parameters of the erupting prominence from a radio absorption model and measured them from 304 Å images. The variations of the parameters as obtained by these two methods are similar and agree within a factor of two. The CME development was studied from the kinematics of the front and different components of the core and their structural changes. The results were verified using movies in which the CME expansion was compensated for according to the measured kinematics. We found that the CME mass (3.6 × 10^{15} g) was mainly supplied by the prominence (≈ 6 × 10^{15} g), while a considerable part drained back. The mass of the coronal-temperature component did not exceed 10^{15} g. The CME was initiated by the erupting prominence, which constituted its core and remained active. The structural and kinematical changes started in the core and propagated outward. The CME structures continued to form during expansion, which did not become self-similar up to 25 R_{⊙}. The aerodynamic drag was insignificant. The core formed during the CME rise to 4 R_{⊙} and possibly beyond. Some of its components were observed to straighten and stretch outward, indicating the transformation of tangled structures of the core into a simpler flux rope, which grew and filled the cavity as the CME expanded.

Stationarity and periodicities of linear speed of coronal mass ejection: a statistical signal processing approach

NASA Astrophysics Data System (ADS)

Chattopadhyay, Anirban; Khondekar, Mofazzal Hossain; Bhattacharjee, Anup Kumar

2017-09-01

In this paper initiative has been taken to search the periodicities of linear speed of Coronal Mass Ejection in solar cycle 23. Double exponential smoothing and Discrete Wavelet Transform are being used for detrending and filtering of the CME linear speed time series. To choose the appropriate statistical methodology for the said purpose, Smoothed Pseudo Wigner-Ville distribution (SPWVD) has been used beforehand to confirm the non-stationarity of the time series. The Time-Frequency representation tool like Hilbert Huang Transform and Empirical Mode decomposition has been implemented to unearth the underneath periodicities in the non-stationary time series of the linear speed of CME. Of all the periodicities having more than 95% Confidence Level, the relevant periodicities have been segregated out using Integral peak detection algorithm. The periodicities observed are of low scale ranging from 2-159 days with some relevant periods like 4 days, 10 days, 11 days, 12 days, 13.7 days, 14.5 and 21.6 days. These short range periodicities indicate the probable origin of the CME is the active longitude and the magnetic flux network of the sun. The results also insinuate about the probable mutual influence and causality with other solar activities (like solar radio emission, Ap index, solar wind speed, etc.) owing to the similitude between their periods and CME linear speed periods. The periodicities of 4 days and 10 days indicate the possible existence of the Rossby-type waves or planetary waves in Sun.

ARE THE FAINT STRUCTURES AHEAD OF SOLAR CORONAL MASS EJECTIONS REAL SIGNATURES OF DRIVEN SHOCKS?

DOE Office of Scientific and Technical Information (OSTI.GOV)

Lee, Jae-Ok; Moon, Y.-J.; Lee, Kangjin

2014-11-20

Recently, several studies have assumed that the faint structures ahead of coronal mass ejections (CMEs) are caused by CME-driven shocks. In this study, we have conducted a statistical investigation to determine whether or not the appearance of such faint structures depends on CME speeds. For this purpose, we use 127 Solar and Heliospheric Observatory/Large Angle Spectroscopic COronagraph (LASCO) front-side halo (partial and full) CMEs near the limb from 1997 to 2011. We classify these CMEs into two groups by visual inspection of CMEs in the LASCO-C2 field of view: Group 1 has the faint structure ahead of a CME andmore » Group 2 does not have such a structure. We find the following results. (1) Eighty-seven CMEs belong to Group 1 and 40 CMEs belong to Group 2. (2) Group 1 events have much higher speeds (average = 1230 km s{sup –1} and median = 1199 km s{sup –1}) than Group 2 events (average = 598 km s{sup –1} and median = 518 km s{sup –1}). (3) The fraction of CMEs with faint structures strongly depends on CME speeds (V): 0.93 (50/54) for fast CMEs with V ≥ 1000 km s{sup –1}, 0.65 (34/52) for intermediate CMEs with 500 km s{sup –1} ≤ V < 1000 km s{sup –1}, and 0.14 (3/21) for slow CMEs with V < 500 km s{sup –1}. We also find that the fraction of CMEs with deca-hecto metric type II radio bursts is consistent with the above tendency. Our results indicate that the observed faint structures ahead of fast CMEs are most likely an enhanced density manifestation of CME-driven shocks.« less

Forecasting Space Weather Events for a Neighboring World

NASA Technical Reports Server (NTRS)

Zheng, Yihua; Mason, Tom; Wood, Erin L.

2015-01-01

Shortly after NASA's Mars Atmosphere and Volatile EvolutioN mission (MAVEN) spacecraft entered Mars' orbit on 21 September 2014, scientists glimpsed the Martian atmosphere's response to a front of solar energetic particles (SEPs) and an associated coronal mass ejection (CME). In response to some solar flares and CMEs, streams of SEPs burst from the solar atmosphere and are further accelerated in the interplanetary medium between the Sun and the planets. These particles deposit their energy and momentum into anything in their path, including the Martian atmosphere and MAVEN particle detectors. MAVEN scientists had been alerted to the likely CME-Mars encounter by a space weather prediction system that had its origins in space weather forecasting for Earth but now forecasts space weather for Earth's neighboring planets. The two Solar Terrestrial Relations Observatory spacecraft and Solar Heliospheric Observatory observed a CME on 26 September, with a trajectory that suggested a Mars intercept. A computer model developed for solar wind prediction, the Wang-Sheeley-Arge-Enlil cone model [e.g., Zheng et al., 2013; Parsons et al., 2011], running in real time at the Community Coordinated Modeling Center (CCMC) located at NASA Goddard since 2006, showed the CME propagating in the direction of Mars (Figure 1). According to MAVEN particle detectors, the disturbance and accompanying SEP enhancement at the leading edge of the CME reached Mars at approximately 17 hours Universal Time on 29 September 2014. Such SEPs may have a profound effect on atmospheric escape - they are believed to be a possible means for driving atmospheric loss. SEPs can cause loss of Mars' upper atmosphere through several loss mechanisms including sputtering of the atmosphere. Sputtering occurs when atoms are ejected from the atmosphere due to impacts with energetic particles.

ISEE 3 observations of low-energy proton bidirectional events and their relation to isolated interplanetary magnetic structures

NASA Technical Reports Server (NTRS)

Marsden, R. G.; Sanderson, T. R.; Tranquille, C.; Wenzel, K.-P.; Smith, E. J.

1987-01-01

The paper represents the results of a comprehensive survey of low-energy proton bidirectional anisotropies and associated transient magnetic structures as observed in the 35-1600 keV energy range on ISEE-3 during the last solar maximum. The majority of observed bidirectional flow (BDF) events (more than 70 percent) are associated with isolated magnetic structures which are postulated to be an interplanetary manifestation of coronal mass ejection (CME) events. The observed BDF events can be qualitatively grouped into five classes depending on the field signature of the related magnetic structure and the association (or lack of association) with an interplanetary shock. Concerning the topology of the CME-related magnetic structures, the observations are interpreted as being consistent with a detached bubble, comprising closed loops or tightly wound helices.

Influence of Convective Effect of Solar Winds on the CME Transit Time

NASA Astrophysics Data System (ADS)

Sun, Lu-yuan

2017-10-01

Based on an empirical model for predicting the transit time of coronal mass ejections (CMEs) proposed by Gopalswamy, 52 CME events which are related to the geomagnetic storms of Dst < -50 nT, and 10 CME events which caused extremely strong geomagnetic storms (Dst < -200 nT) in 1996- 2007 are selected, and combined with the observational data of the interplanetary solar winds that collected by the ACE satellite at 1AU, to analyze the influence of convective effect of ambient solar winds on the prediction of the CME transit time when it arrives at a place of 1 AU. After taking the convective effect of ambient solar winds into account, the standard deviation of predictions is reduced from 16.5 to 11.4 hours for the 52 CME events, and the prediction error is less than 15 hours for 68% of these events; while the standard deviation of predictions is reduced from 10.6 to 6.5 hours for the 10 CME events that caused extremely strong geomagnetic storms, and the prediction error is less than 5 hours for 6 of the 10 events. These results show that taking the convective effect of ambient solar winds into account can reduce the standard deviation of the predicted CME transit time, hence the convective effect of solar winds plays an important role for predicting the transit times of CME events.

Decameter Type IV Burst Associated with a Behind-the-limb CME Observed on 7 November 2013

NASA Astrophysics Data System (ADS)

Melnik, V. N.; Brazhenko, A. I.; Konovalenko, A. A.; Dorovskyy, V. V.; Rucker, H. O.; Panchenko, M.; Frantsuzenko, A. V.; Shevchuk, M. V.

2018-03-01

We report on the results of observations of a type IV burst made by the Ukrainian Radio interferometer of the Academy of Sciences (URAN-2) in the frequency range 22 - 33 MHz. The burst is associated with a coronal mass ejection (CME) initiated by a behind-the-limb active region (N05E151) and was also observed by the Nançay Decameter Array (NDA) radio telescope in the frequency band 30 - 60 MHz. The purpose of the article is the determination of the source of this type IV burst. After analysis of the observational data obtained with the URAN-2, the NDA, the Solar-Terrestrial Relations Observatory (STEREO) A and B spacecraft, and the Solar and Heliospheric Observatory (SOHO) spacecraft, we come to the conclusion that the source of the burst is the core of a behind-the-limb CME. We conclude that the radio emission can escape the center of the CME core at a frequency of 60 MHz and originates from the periphery of the core at a frequency of 30 MHz that is due to occultation by the solar corona at the corresponding frequencies. We find plasma densities in these regions assuming the plasma mechanism of radio emission. We show that the frequency drift of the start of the type IV burst is governed by an expansion of the CME core. The type III bursts that were observed against this type IV burst are shown to be generated by fast electrons propagating through the CME core plasma. A type II burst was registered at frequencies of 44 - 64 MHz and 3 - 16 MHz and was radiated by a shock with velocities of about 1000 km s^{-1} and 800 km s^{-1}, respectively.

Global Energetics of Solar Flares. V. Energy Closure in Flares and Coronal Mass Ejections

NASA Astrophysics Data System (ADS)

Aschwanden, Markus J.; Caspi, Amir; Cohen, Christina M. S.; Holman, Gordon; Jing, Ju; Kretzschmar, Matthieu; Kontar, Eduard P.; McTiernan, James M.; Mewaldt, Richard A.; O'Flannagain, Aidan; Richardson, Ian G.; Ryan, Daniel; Warren, Harry P.; Xu, Yan

2017-02-01

In this study we synthesize the results of four previous studies on the global energetics of solar flares and associated coronal mass ejections (CMEs), which include magnetic, thermal, nonthermal, and CME energies in 399 solar M- and X-class flare events observed during the first 3.5 yr of the Solar Dynamics Observatory (SDO) mission. Our findings are as follows. (1) The sum of the mean nonthermal energy of flare-accelerated particles ({E}{nt}), the energy of direct heating ({E}{dir}), and the energy in CMEs ({E}{CME}), which are the primary energy dissipation processes in a flare, is found to have a ratio of ({E}{nt}+{E}{dir}+{E}{CME})/{E}{mag}=0.87+/- 0.18, compared with the dissipated magnetic free energy {E}{mag}, which confirms energy closure within the measurement uncertainties and corroborates the magnetic origin of flares and CMEs. (2) The energy partition of the dissipated magnetic free energy is: 0.51 ± 0.17 in nonthermal energy of ≥slant 6 {keV} electrons, 0.17 ± 0.17 in nonthermal ≥slant 1 {MeV} ions, 0.07 ± 0.14 in CMEs, and 0.07 ± 0.17 in direct heating. (3) The thermal energy is almost always less than the nonthermal energy, which is consistent with the thick-target model. (4) The bolometric luminosity in white-light flares is comparable to the thermal energy in soft X-rays (SXR). (5) Solar energetic particle events carry a fraction ≈ 0.03 of the CME energy, which is consistent with CME-driven shock acceleration. (6) The warm-target model predicts a lower limit of the low-energy cutoff at {e}c≈ 6 {keV}, based on the mean peak temperature of the differential emission measure of T e = 8.6 MK during flares. This work represents the first statistical study that establishes energy closure in solar flare/CME events.

Halo CME

NASA Image and Video Library

2017-12-08

A giant cloud appears to expand outward from the sun in all directions in this image from Sept. 28, 2012, which is called a halo CME. This kind of image occurs when a CME moves toward Earth – as here – or directly away from it. Credit: ESA/NASA/SOHO CME WEEK: What To See in CME Images Two main types of explosions occur on the sun: solar flares and coronal mass ejections. Unlike the energy and x-rays produced in a solar flare – which can reach Earth at the speed of light in eight minutes – coronal mass ejections are giant, expanding clouds of solar material that take one to three days to reach Earth. Once at Earth, these ejections, also called CMEs, can impact satellites in space or interfere with radio communications. During CME WEEK from Sept. 22 to 26, 2014, we explore different aspects of these giant eruptions that surge out from the star we live with. When a coronal mass ejection blasts off the sun, scientists rely on instruments called coronagraphs to track their progress. Coronagraphs block out the bright light of the sun, so that the much fainter material in the solar atmosphere -- including CMEs -- can be seen in the surrounding space. CMEs appear in these images as expanding shells of material from the sun's atmosphere -- sometimes a core of colder, solar material (called a filament) from near the sun's surface moves in the center. But mapping out such three-dimensional components from a two-dimensional image isn't easy. Watch the slideshow to find out how scientists interpret what they see in CME pictures. The images in the slideshow are from the three sets of coronagraphs NASA currently has in space. One is on the joint European Space Agency and NASA Solar and Heliospheric Observatory, or SOHO. SOHO launched in 1995, and sits between Earth and the sun about a million miles away from Earth. The other two coronagraphs are on the two spacecraft of the NASA Solar Terrestrial Relations Observatory, or STEREO, mission, which launched in 2006. The two STEREO spacecraft are both currently viewing the far side of the sun. Together these instruments help scientists create a three-dimensional model of any CME as its journey unfolds through interplanetary space. Such information can show why a given characteristic of a CME close to the sun might lead to a given effect near Earth, or any other planet in the solar system...NASA image use policy. NASA Goddard Space Flight Center enables NASA’s mission through four scientific endeavors: Earth Science, Heliophysics, Solar System Exploration, and Astrophysics. Goddard plays a leading role in NASA’s accomplishments by contributing compelling scientific knowledge to advance the Agency’s mission. Follow us on Twitter Like us on Facebook Find us on Instagram

STEREO's View

NASA Image and Video Library

2017-12-08

STEREO witnessed the March 5, 2013, CME from the side of the sun – Earth is far to the left of this picture. While the SOHO images show a halo CME, STEREO shows the CME clearly moving away from Earth. Credit: NASA/STEREO --- CME WEEK: What To See in CME Images Two main types of explosions occur on the sun: solar flares and coronal mass ejections. Unlike the energy and x-rays produced in a solar flare – which can reach Earth at the speed of light in eight minutes – coronal mass ejections are giant, expanding clouds of solar material that take one to three days to reach Earth. Once at Earth, these ejections, also called CMEs, can impact satellites in space or interfere with radio communications. During CME WEEK from Sept. 22 to 26, 2014, we explore different aspects of these giant eruptions that surge out from the star we live with. When a coronal mass ejection blasts off the sun, scientists rely on instruments called coronagraphs to track their progress. Coronagraphs block out the bright light of the sun, so that the much fainter material in the solar atmosphere -- including CMEs -- can be seen in the surrounding space. CMEs appear in these images as expanding shells of material from the sun's atmosphere -- sometimes a core of colder, solar material (called a filament) from near the sun's surface moves in the center. But mapping out such three-dimensional components from a two-dimensional image isn't easy. Watch the slideshow to find out how scientists interpret what they see in CME pictures. The images in the slideshow are from the three sets of coronagraphs NASA currently has in space. One is on the joint European Space Agency and NASA Solar and Heliospheric Observatory, or SOHO. SOHO launched in 1995, and sits between Earth and the sun about a million miles away from Earth. The other two coronagraphs are on the two spacecraft of the NASA Solar Terrestrial Relations Observatory, or STEREO, mission, which launched in 2006. The two STEREO spacecraft are both currently viewing the far side of the sun. Together these instruments help scientists create a three-dimensional model of any CME as its journey unfolds through interplanetary space. Such information can show why a given characteristic of a CME close to the sun might lead to a given effect near Earth, or any other planet in the solar system. NASA image use policy. NASA Goddard Space Flight Center enables NASA’s mission through four scientific endeavors: Earth Science, Heliophysics, Solar System Exploration, and Astrophysics. Goddard plays a leading role in NASA’s accomplishments by contributing compelling scientific knowledge to advance the Agency’s mission. Follow us on Twitter Like us on Facebook Find us on Instagram

Faraday Rotation as a Probe of Coronal Mass Ejections

NASA Astrophysics Data System (ADS)

Kooi, J. E.; Spangler, S. R.; Kassim, N. E.

2016-12-01

Coronal mass ejections (CMEs) are large-scale eruptions of plasma from the Sun that play an important role in space weather. Although CMEs have been an active field of research since their discovery in the 1970s, there is still much to understand about the plasma structure of CMEs. Faraday rotation (FR) is the rotation of the plane of polarization that results when a linearly polarized signal passes through a magnetized plasma such as a CME. FR observations of a source near the Sun can provide information on the plasma structure of a CME shortly after launch. We made sensitive Very Large Array (VLA) full-polarization observations in August, 2012, using 1 — 2 GHz frequencies of a "constellation" of radio sources through the solar corona at heliocentric distances that ranged from 6 — 15 solar radii. Of the nine sources observed, three were occulted by CMEs. In addition to our radioastronomical observations, which represent one of the first active hunts for CME Faraday rotation since Bird et al. (1985) and the first active hunt using the VLA, we obtained white-light coronagraph images from the LASCO/C3 instrument to determine the Thomson scattering brightness, BT, providing a means to independently estimate the plasma density and determine its contribution to the observed Faraday rotation. A constant density force-free flux rope embedded in the background corona was used to model the effects of the CMEs on BT and FR. The single flux rope model successfully reproduces the observed BT and FR profiles for two sources. The third source (0843+1547) was occulted by two CMEs and, therefore, we modeled observations of this source using two flux ropes embedded in the background corona. The two flux rope model successfully reproduces both BT and FR profiles for 0843+1547 and, in particular, the two flux rope model successfully replicates the appropriate slope in FR before and after occultation by the second CME and predicts the observed change in sign to FR > 0 at the end of the observing session. The plasma densities (6 — 22 × 103 cm-3) and axial magnetic field strengths (2 — 12 mG) inferred from our models are consistent with the modeling work of Liu et al. (2007) and Jensen et al. (2008), as well as previous CME FR observations by Bird et al. (1985). This work was supported at the University of Iowa by grant ATM09-56901.

The Formation and Early Evolution of a Coronal Mass Ejection and its Associated Shock Wave on 2014 January 8

NASA Astrophysics Data System (ADS)

Wan, Linfeng; Cheng, Xin; Shi, Tong; Su, Wei; Ding, M. D.

2016-08-01

In this paper, we study the formation and early evolution of a limb coronal mass ejection (CME) and its associated shock wave that occurred on 2014 January 8. The extreme ultraviolet (EUV) images provided by the Atmospheric Imaging Assembly (AIA) on board the Solar Dynamics Observatory disclose that the CME first appears as a bubble-like structure. Subsequently, its expansion forms the CME and causes a quasi-circular EUV wave. Interestingly, both the CME and the wave front are clearly visible at all of the AIA EUV passbands. Through a detailed kinematical analysis, it is found that the expansion of the CME undergoes two phases: a first phase with a strong but transient lateral over-expansion followed by a second phase with a self-similar expansion. The temporal evolution of the expansion velocity coincides very well with the variation of the 25-50 keV hard X-ray flux of the associated flare, which indicates that magnetic reconnection most likely plays an important role in driving the expansion. Moreover, we find that, when the velocity of the CME reaches ˜600 km s-1, the EUV wave starts to evolve into a shock wave, which is evidenced by the appearance of a type II radio burst. The shock’s formation height is estimated to be ˜0.2 R sun, which is much lower than the height derived previously. Finally, we also study the thermal properties of the CME and the EUV wave. We find that the plasma in the CME leading front and the wave front has a temperature of ˜2 MK, while that in the CME core region and the flare region has a much higher temperature of ≥8 MK.

Snowy CME

NASA Image and Video Library

2017-12-08

A solar flare associated with the coronal mass ejection seen in this image generated a flurry of fast-moving solar protons. As each one hits the CCD camera on SOHO, it produces a brief snow-like speckle in the image. Credit: NASA/SOHO CME WEEK: What To See in CME Images Two main types of explosions occur on the sun: solar flares and coronal mass ejections. Unlike the energy and x-rays produced in a solar flare – which can reach Earth at the speed of light in eight minutes – coronal mass ejections are giant, expanding clouds of solar material that take one to three days to reach Earth. Once at Earth, these ejections, also called CMEs, can impact satellites in space or interfere with radio communications. During CME WEEK from Sept. 22 to 26, 2014, we explore different aspects of these giant eruptions that surge out from the star we live with. When a coronal mass ejection blasts off the sun, scientists rely on instruments called coronagraphs to track their progress. Coronagraphs block out the bright light of the sun, so that the much fainter material in the solar atmosphere -- including CMEs -- can be seen in the surrounding space. CMEs appear in these images as expanding shells of material from the sun's atmosphere -- sometimes a core of colder, solar material (called a filament) from near the sun's surface moves in the center. But mapping out such three-dimensional components from a two-dimensional image isn't easy. Watch the slideshow to find out how scientists interpret what they see in CME pictures. The images in the slideshow are from the three sets of coronagraphs NASA currently has in space. One is on the joint European Space Agency and NASA Solar and Heliospheric Observatory, or SOHO. SOHO launched in 1995, and sits between Earth and the sun about a million miles away from Earth. The other two coronagraphs are on the two spacecraft of the NASA Solar Terrestrial Relations Observatory, or STEREO, mission, which launched in 2006. The two STEREO spacecraft are both currently viewing the far side of the sun. Together these instruments help scientists create a three-dimensional model of any CME as its journey unfolds through interplanetary space. Such information can show why a given characteristic of a CME close to the sun might lead to a given effect near Earth, or any other planet in the solar system...NASA image use policy. NASA Goddard Space Flight Center enables NASA’s mission through four scientific endeavors: Earth Science, Heliophysics, Solar System Exploration, and Astrophysics. Goddard plays a leading role in NASA’s accomplishments by contributing compelling scientific knowledge to advance the Agency’s mission. Follow us on Twitter Like us on Facebook Find us on Instagram

Observations of CMEs and Models of the Eruptive Corona

NASA Technical Reports Server (NTRS)

Gopalswamy, Nat

2012-01-01

It is now realized that coronal mass ejections (CMEs) are the most energetic phenomenon in the heliosphere. Although early observations (in the 1970s and 19805) revealed most of the properties of CMEs, it is the extended and uniform data set from the Solar and Heliospheric Observatory (SOHO) mission that helped us consolidate our knowledge on CMEs. The Solar Terrestrial Relations Observatory (STEREO) mission has provided direct confirmation of the three-dimensional structure of CMEs. The broadside view provided by the STEREO coronagraphs helped us estimate the width of the halo CMEs and hence validate CME cone models. Current theoretical ideas on the internal structure of CMEs suggest that a flux rope is central to the CME structure, which has considerable observational support both from remote-sensing and in-situ observations. The flux-rope nature is also consistent with the post-eruption arcades with high-temperature plasma and the charge states observed within CMEs arriving at Earth. The quadrature observations also helped us understand the relation between the radial and expansion speeds of CMEs, which were only known from empirical relations in the past. This paper highlights some of these results obtained during solar cycle 23 and 24 and discusses implications for CME models.

Forecast of geomagnetic storms using CME parameters and the WSA-ENLIL model

NASA Astrophysics Data System (ADS)

Moon, Y.; Lee, J.; Jang, S.; Na, H.; Lee, J.

2013-12-01

Intense geomagnetic storms are caused by coronal mass ejections (CMEs) from the Sun and their forecast is quite important in protecting space- and ground-based technological systems. The onset and strength of geomagnetic storms depend on the kinematic and magnetic properties of CMEs. Current forecast techniques mostly use solar wind in-situ measurements that provide only a short lead time. On the other hand, techniques using CME observations near the Sun have the potential to provide 1-3 days of lead time before the storm occurs. Therefore, one of the challenging issues is to forecast interplanetary magnetic field (IMF) southward components and hence geomagnetic storm strength with a lead-time on the order of 1-3 days. We are going to answer the following three questions: (1) when does a CME arrive at the Earth? (2) what is the probability that a CME can induce a geomagnetic storm? and (3) how strong is the storm? To address the first question, we forecast the arrival time and other physical parameters of CMEs at the Earth using the WSA-ENLIL model with three CME cone types. The second question is answered by examining the geoeffective and non-geoeffective CMEs depending on CME observations (speed, source location, earthward direction, magnetic field orientation, and cone-model output). The third question is addressed by examining the relationship between CME parameters and geomagnetic indices (or IMF southward component). The forecast method will be developed with a three-stage approach, which will make a prediction within four hours after the solar coronagraph data become available. We expect that this study will enable us to forecast the onset and strength of a geomagnetic storm a few days in advance using only CME parameters and the physics-based models.

A Series of Jets that Drove Streamer-Puff CMEs from Giant Active Region of 2014

NASA Technical Reports Server (NTRS)

Panesar, Navdeep K.; Sterling, Alphonse C.; Moore, Ronald L.

2016-01-01

We investigate characteristics of solar coronal jets that originated from active region NOAA 12192 and produced coronal mass ejections (CMEs). This active region produced many non­-jet major flare eruptions (X and M class) that made no CME. A multitude of jets occurred from the southeast edge of the active region, and in contrast to the major-­flare eruptions in the core, six of these jets resulted in CMEs. Our jet observations are from SDO/AIA EUV channels and from Hinode/XRT, and CME observations are from the SOHO/LASCO C2 coronograph. Each jet-­driven CME was relatively slow-­moving (approx. 200 - 300 km/s) compared to most CMEs; had angular width (20deg - 50deg) comparable to that of the streamer base; and was of the "streamer­-puff" variety, whereby a pre-existing streamer was transiently inflated but not removed (blown out) by the passage of the CME. Much of the chromospheric-­temperature plasma of the jets producing the CMEs escaped from the Sun, whereas relatively more of the chromospheric plasma in the non-CME-producing jets fell back to the solar surface. We also found that the CME-producing jets tended to be faster in speed and longer in duration than the non-CME-­producing jets. We expect that the jets result from eruptions of mini-filaments. We further propose that the CMEs are driven by magnetic twist injected into streamer-­base coronal loops when erupting twisted mini-filament field reconnects with the ambient field at the foot of those loops.

A Series of Jets that Drove Streamer-Puff CMEs from Giant Active Region of 2014

NASA Technical Reports Server (NTRS)

Panesar, Navdeep K.; Sterling, Alphonse C.; Moore, Ronald L.

2016-01-01

We investigate characteristics of solar coronal jets that originated from active region NOAA 12192 and produced coronal mass ejections (CMEs). This active region produced many non-jet major flare eruptions (X and M class) that made no CME. A multiitude of jets occurred from the southeast edge of the active region, and in contrast to the major-flare eruptions in the core, six of these jets resulted in CMEs. Our jet observations are from multiple SDO/AIA EUV channels, including 304, 171 and 193 Angstrom, and CME observations are taken from SOHO/LASCO C2 coronograph. Each jet-driven CME was relatively slow-moving (approximately 200 - 300 km s(sup-1) compared to most CMEs; had angular width (20deg - 50deg) comparable to that of the streamer base; and was of the "streamer-puff" variety, whereby a preexisting streamer was transiently inflated but not removed (blown out) by the passage of the CME. Much of the chromospheric-temperature plasma of the jets producing the CMEs escaped from the Sun, whereas relatively more of the chromospheric plasma in the non-CME-producing jets fell back to the solar surface. We also found that the CME-producing jets tended to be faster in speed and longer in duration than the non-CME-producing jets. We expect that the jets result from eruptions of mini-filaments. We further propose that the CMEs are driven by magnetic twist injected into streamer-base coronal loops when erupting twisted mini-filament field reconnects with the ambient field at the foot of those loops.

SOURCE REGIONS OF THE TYPE II RADIO BURST OBSERVED DURING A CME–CME INTERACTION ON 2013 MAY 22

DOE Office of Scientific and Technical Information (OSTI.GOV)

Mäkelä, P.; Reiner, M. J.; Akiyama, S.

2016-08-20

We report on our study of radio source regions during the type II radio burst on 2013 May 22 based on direction-finding analysis of the Wind /WAVES and STEREO /WAVES (SWAVES) radio observations at decameter–hectometric wavelengths. The type II emission showed an enhancement that coincided with the interaction of two coronal mass ejections (CMEs) launched in sequence along closely spaced trajectories. The triangulation of the SWAVES source directions posited the ecliptic projections of the radio sources near the line connecting the Sun and the STEREO-A spacecraft. The WAVES and SWAVES source directions revealed shifts in the latitude of the radiomore » source, indicating that the spatial location of the dominant source of the type II emission varies during the CME–CME interaction. The WAVES source directions close to 1 MHz frequencies matched the location of the leading edge of the primary CME seen in the images of the LASCO/C3 coronagraph. This correspondence of spatial locations at both wavelengths confirms that the CME–CME interaction region is the source of the type II enhancement. Comparison of radio and white-light observations also showed that at lower frequencies scattering significantly affects radio wave propagation.« less

DOE Office of Scientific and Technical Information (OSTI.GOV)

Liu, Ying D.; Yang, Zhongwei; Wang, Rui

On 2012 September 30-October 1 the Earth underwent a two-step geomagnetic storm. We examine the Sun-to-Earth characteristics of the coronal mass ejections (CMEs) responsible for the geomagnetic storm with combined heliospheric imaging and in situ observations. The first CME, which occurred on 2012 September 25, is a slow event and shows an acceleration followed by a nearly invariant speed in the whole Sun-Earth space. The second event, launched from the Sun on 2012 September 27, exhibits a quick acceleration, then a rapid deceleration, and finally a nearly constant speed, a typical Sun-to-Earth propagation profile for fast CMEs. These two CMEsmore » interacted near 1 AU as predicted by the heliospheric imaging observations and formed a complex ejecta observed at Wind, with a shock inside that enhanced the pre-existing southward magnetic field. Reconstruction of the complex ejecta with the in situ data indicates an overall left-handed flux-rope-like configuration with an embedded concave-outward shock front, a maximum magnetic field strength deviating from the flux rope axis, and convex-outward field lines ahead of the shock. While the reconstruction results are consistent with the picture of CME-CME interactions, a magnetic cloud-like structure without clear signs of CME interactions is anticipated when the merging process is finished.« less

Inner Structure of CME Shock Fronts Revealed by the Electromotive Force and Turbulent Transport Coefficients in Helios-2 Observations

NASA Astrophysics Data System (ADS)

Bourdin, Philippe-A.; Hofer, Bernhard; Narita, Yasuhito

2018-03-01

Electromotive force is an essential quantity in dynamo theory. During a coronal mass ejection (CME), magnetic helicity gets decoupled from the Sun and advected into the heliosphere with the solar wind. Eventually, a heliospheric magnetic transient event might pass by a spacecraft, such as the Helios space observatories. Our aim is to investigate the electromotive force, the kinetic helicity effect (α term), the turbulent diffusion (β term), and the cross-helicity effect (γ term) in the inner heliosphere below 1 au. We set up a one-dimensional model of the solar wind velocity and magnetic field for a hypothetic interplanetary CME. Because turbulent structures within the solar wind evolve much slower than this structure needs to pass by the spacecraft, we use a reduced curl operator to compute the current density and vorticity. We test our CME shock-front model against an observed magnetic transient that passes by the Helios-2 spacecraft. At the peak of the fluctuations in this event we find strongly enhanced α, β, and γ terms, as well as a strong peak in the total electromotive force. Our method allows us to automatically identify magnetic transient events from any in situ spacecraft observations that contain magnetic field and plasma velocity data of the solar wind.

Statistical Study of Interplanetary Coronal Mass Ejections with Strong Magnetic Fields

NASA Astrophysics Data System (ADS)

Murphy, Matthew E.

Coronal Mass Ejections (CMEs) with strong magnetic fields (B ) are typically associated with significant Solar Energetic Particle (SEP) events, high solar wind speed and solar flare events. Successful prediction of the arrival time of a CME at Earth is required to maximize the time available for satellite, infrastructure, and space travel programs to take protective action against the coming flux of high-energy particles. It is known that the magnetic field strength of a CME is linked to the strength of a geomagnetic storm on Earth. Unfortunately, the correlations between strong magnetic field CMEs from the entire sun (especially from the far side or non-Earth facing side of the sun) to SEP and flare events, solar source regions and other relevant solar variables are not well known. New correlation studies using an artificial intelligence engine (Eureqa) were performed to study CME events with magnetic field strength readings over 30 nanoteslas (nT) from January 2010 to October 17, 2014. This thesis presents the results of this study, validates Eureqa to obtain previously published results, and presents previously unknown functional relationships between solar source magnetic field data, CME initial speed and the CME magnetic field. These new results enable the development of more accurate CME magnetic field predictions and should help scientists develop better forecasts thereby helping to prevent damage to humanity's space and Earth assets.

The Flare/CME Connection

NASA Technical Reports Server (NTRS)

Moore, Ron; Falconer, David; Sterling, Alphonse

2008-01-01

We present evidence supporting the view that, while many flares are produced by a confined magnetic explosion that does not produce a CME, every CME is produced by an ejective magnetic explosion that also produces a flare. The evidence is that the observed heliocentric angular width of the full-blown CME plasmoid in the outer corona (at 3 to 20 solar radii) is about that predicted by the standard model for CME production, from the amount of magnetic flux covered by the co-produced flare arcade. In the standard model, sheared and twisted sigmoidal field in the core of an initially closed magnetic arcade erupts. As it erupts, tether-cutting reconnection, starting between the legs of the erupting sigmoid and continuing between the merging stretched legs of the enveloping arcade, simultaneously produces a growing flare arcade and unleashes the erupting sigmoid and arcade to become the low-beta plasmoid (magnetic bubble) that becomes the CME. The flare arcade is the downward product of the reconnection and the CME plasmoid is the upward product. The unleashed, expanding CME plasmoid is propelled into the outer corona and solar wind by its own magnetic field pushing on the surrounding field in the inner and outer corona. This tether-cutting scenario predicts that the amount of magnetic flux in the full-blown CME plasmoid nearly equals that covered by the full-grown flare arcade. This equality predicts (1) the field strength in the flare region from the ratio of the angular width of the CME in the outer corona to angular width of the full-grown flare arcade, and (2) an upper bound on the angular width of the CME in the outer corona from the total magnetic flux in the active region from which the CME explodes. We show that these predictions are fulfilled by observed CMEs. This agreement validates the standard model. The model explains (1) why most CMEs have much greater angular widths than their co-produced flares, and (2) why the radial path of a CME in the outer corona can be laterally far offset from the co-produced flare.

Analysis of EIT/LASCO Observations Using Available MHD Models: Investigation of CME Initiation Propagation and Geoeffectiveness

NASA Technical Reports Server (NTRS)

Wu, S. T.

2001-01-01

The Sun's activity drives the variability of geospace (i.e., near-earth environment). Observations show that the ejection of plasma from the sun, called coronal mass ejections (CMEs), are the major cause of geomagnetic storms. This global-scale solar dynamical feature of coronal mass ejection was discovered almost three decades ago by the use of space-borne coronagraphs (OSO-7, Skylab/ATM and P78-1). Significant progress has been made in understanding the physical nature of the CMEs. Observations show that these global-scale CMEs have size in the order of a solar radius (approximately 6.7 x 10(exp 5) km) near the sun, and each event involves a mass of about 10(exp 15) g and an energy comparable to that of a large flare on the order of 10(exp 32) ergs. The radial propagation speeds of CMEs have a wide range from tens to thousands of kilometers per second. Thus, the transit time to near earth's environment [i.e., 1 AU (astronomical unit)] can be as fast as 40 hours to 100 hours. The typical transit time for geoeffective events is approximately 60-80 h. This paper consists of two parts: 1) A summary of the observed CMEs from Skylab to the present SOHO will be presented. Special attention will be made to SOHO/ LASCO/ EIT observations and their characteristics leading to a geoeffectiv a CME 2) The chronological development of theory and models to interpret the physical nature of this fascinating phenomenon will be reviewed. Finally, an example will be presented to illustrate the geoeffectiveness of the CMEs by using both observation and model.

The density compression ratio of shock fronts associated with coronal mass ejections

NASA Astrophysics Data System (ADS)

Kwon, Ryun-Young; Vourlidas, Angelos

2018-02-01

We present a new method to extract the three-dimensional electron density profile and density compression ratio of shock fronts associated with coronal mass ejections (CMEs) observed in white light coronagraph images. We demonstrate the method with two examples of fast halo CMEs (˜2000 km s-1) observed on 2011 March 7 and 2014 February 25. Our method uses the ellipsoid model to derive the three-dimensional geometry and kinematics of the fronts. The density profiles of the sheaths are modeled with double-Gaussian functions with four free parameters, and the electrons are distributed within thin shells behind the front. The modeled densities are integrated along the lines of sight to be compared with the observed brightness in COR2-A, and a χ2 approach is used to obtain the optimal parameters for the Gaussian profiles. The upstream densities are obtained from both the inversion of the brightness in a pre-event image and an empirical model. Then the density ratio and Alfvénic Mach number are derived. We find that the density compression peaks around the CME nose, and decreases at larger position angles. The behavior is consistent with a driven shock at the nose and a freely propagating shock wave at the CME flanks. Interestingly, we find that the supercritical region extends over a large area of the shock and lasts longer (several tens of minutes) than past reports. It follows that CME shocks are capable of accelerating energetic particles in the corona over extended spatial and temporal scales and are likely responsible for the wide longitudinal distribution of these particles in the inner heliosphere. Our results also demonstrate the power of multi-viewpoint coronagraphic observations and forward modeling in remotely deriving key shock properties in an otherwise inaccessible regime.

An Investigation of the Large Scale Evolution and Topology of Coronal Mass Ejections in the Solar Wind

NASA Technical Reports Server (NTRS)

Riley, Peter

2000-01-01

This investigation is concerned with the large-scale evolution and topology of coronal mass ejections (CMEs) in the solar wind. During this reporting period we have focused on several aspects of CME properties, their identification and their evolution in the solar wind. The work included both analysis of Ulysses and ACE observations as well as fluid and magnetohydrodynamic simulations. In addition, we analyzed a series of "density holes" observed in the solar wind, that bear many similarities with CMEs. Finally, this work was communicated to the scientific community at three meetings and has led to three scientific papers that are in various stages of review.

MHD shocks in coronal mass ejections

NASA Technical Reports Server (NTRS)

Steinolfson, R. S.

1991-01-01

The primary objective of this research program is the study of the magnetohydrodynamic (MHD) shocks and nonlinear simple waves produced as a result of the interaction of ejected lower coronal plasma with the ambient corona. The types of shocks and nonlinear simple waves produced for representative coronal conditions and disturbance velocities were determined. The wave system and the interactions between the ejecta and ambient corona were studied using both analytic theory and numerical solutions of the time-dependent, nonlinear MHD equations. Observations from the SMM coronagraph/polarimeter provided both guidance and motivation and are used extensively in evaluating the results. As a natural consequence of the comparisons with the data, the simulations assisted in better understanding the physical interactions in coronal mass ejections (CME's).

The Drag-based Ensemble Model (DBEM) for Coronal Mass Ejection Propagation

NASA Astrophysics Data System (ADS)

Dumbović, Mateja; Čalogović, Jaša; Vršnak, Bojan; Temmer, Manuela; Mays, M. Leila; Veronig, Astrid; Piantschitsch, Isabell

2018-02-01

The drag-based model for heliospheric propagation of coronal mass ejections (CMEs) is a widely used analytical model that can predict CME arrival time and speed at a given heliospheric location. It is based on the assumption that the propagation of CMEs in interplanetary space is solely under the influence of magnetohydrodynamical drag, where CME propagation is determined based on CME initial properties as well as the properties of the ambient solar wind. We present an upgraded version, the drag-based ensemble model (DBEM), that covers ensemble modeling to produce a distribution of possible ICME arrival times and speeds. Multiple runs using uncertainty ranges for the input values can be performed in almost real-time, within a few minutes. This allows us to define the most likely ICME arrival times and speeds, quantify prediction uncertainties, and determine forecast confidence. The performance of the DBEM is evaluated and compared to that of ensemble WSA-ENLIL+Cone model (ENLIL) using the same sample of events. It is found that the mean error is ME = ‑9.7 hr, mean absolute error MAE = 14.3 hr, and root mean square error RMSE = 16.7 hr, which is somewhat higher than, but comparable to ENLIL errors (ME = ‑6.1 hr, MAE = 12.8 hr and RMSE = 14.4 hr). Overall, DBEM and ENLIL show a similar performance. Furthermore, we find that in both models fast CMEs are predicted to arrive earlier than observed, most likely owing to the physical limitations of models, but possibly also related to an overestimation of the CME initial speed for fast CMEs.

Investigating the Wave Nature of the Outer Envelope of Halo Coronal Mass Ejections

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kwon, Ryun-Young; Vourlidas, Angelos, E-mail: rkwon@gmu.edu

We investigate the nature of the outer envelope of halo coronal mass ejections (H-CMEs) using multi-viewpoint observations from the Solar Terrestrial Relations Observatory-A , -B , and SOlar and Heliospheric Observatory coronagraphs. The 3D structure and kinematics of the halo envelopes and the driving CMEs are derived separately using a forward modeling method. We analyze three H-CMEs with peak speeds from 1355 to 2157 km s{sup −1}; sufficiently fast to drive shocks in the corona. We find that the angular widths of the halos range from 192° to 252°, while those of the flux ropes range between only 58° andmore » 91°, indicating that the halos are waves propagating away from the CMEs. The halo widths are in agreement with widths of Extreme Ultraviolet (EUV) waves in the low corona further demonstrating the common origin of these structures. To further investigate the wave nature of the halos, we model their 3D kinematic properties with a linear fast magnetosonic wave model. The model is able to reproduce the position of the halo flanks with realistic coronal medium assumptions but fails closer to the CME nose. The CME halo envelope seems to arise from a driven wave (or shock) close to the CME nose, but it is gradually becoming a freely propagating fast magnetosonic wave at the flanks. This interpretation provides a simple unifying picture for CME halos, EUV waves, and the large longitudinal spread of solar energetic particles.« less

PREDICTING CORONAL MASS EJECTIONS USING MACHINE LEARNING METHODS

DOE Office of Scientific and Technical Information (OSTI.GOV)

Bobra, M. G.; Ilonidis, S.

Of all the activity observed on the Sun, two of the most energetic events are flares and coronal mass ejections (CMEs). Usually, solar active regions that produce large flares will also produce a CME, but this is not always true. Despite advances in numerical modeling, it is still unclear which circumstances will produce a CME. Therefore, it is worthwhile to empirically determine which features distinguish flares associated with CMEs from flares that are not. At this time, no extensive study has used physically meaningful features of active regions to distinguish between these two populations. As such, we attempt to domore » so by using features derived from (1) photospheric vector magnetic field data taken by the Solar Dynamics Observatory ’s Helioseismic and Magnetic Imager instrument and (2) X-ray flux data from the Geostationary Operational Environmental Satellite’s X-ray Flux instrument. We build a catalog of active regions that either produced both a flare and a CME (the positive class) or simply a flare (the negative class). We then use machine-learning algorithms to (1) determine which features distinguish these two populations, and (2) forecast whether an active region that produces an M- or X-class flare will also produce a CME. We compute the True Skill Statistic, a forecast verification metric, and find that it is a relatively high value of ∼0.8 ± 0.2. We conclude that a combination of six parameters, which are all intensive in nature, will capture most of the relevant information contained in the photospheric magnetic field.« less

Activity associated with the solar origin of coronal mass ejections

NASA Technical Reports Server (NTRS)

Webb, D. F.; Hundhausen, A. J.

1987-01-01

Solar coronal mass ejections (CMEs) observed in 1980 with the HAO Coronagraph/Polarimeter on the Solar Maximum Mission (SMM) satellite are compared with other forms of solar activity that might be physically related to the ejections. The solar phenomena checked and the method of association used were intentionally patterned after those of Munro et al.'s (1979) analysis of mass ejections observed with the Skylab coronagraph to facilitate comparison of the two epochs. Comparison of the results reveals that the types and degree of CME associations are similar near solar activity minimum and at maximum. For both epochs, most CMEs with associations had associated eruptive prominences, and the proportions of association of all types of activity were similar. A high percentage of association between SMM CMEs and X-ray long duration events is also found, in agreement with Skylab results. It is concluded that most CMEs are the result of the destabilization and eruption of a prominence and its overlying coronal structure, or of a magnetic structure capable of supporting a prominence.

CME Simulations with Boundary Conditions Derived from Multiple Viewpoints of STEREO

NASA Astrophysics Data System (ADS)

Singh, T.; Yalim, M. S.; Pogorelov, N. V.

2017-12-01

Coronal Mass Ejections (CMEs) are major drivers of extreme space weather conditions, which is a matter of huge concern for our modern technologically dependent society. Development of numerical approaches that would reproduce CME propagation through the interplanetary space is an important step towards our capability to predict CME arrival time at Earth and their geo-effectiveness. It is also important that CMEs are propagating through a realistic, data-driven background solar wind (SW). In this study, we use a version of the flux-rope-driven Gibson-Low (GL) model to simulate CMEs. We derive inner boundary conditions for the GL flux rope model using the Graduate Cylindrical Shell (GCS) method. This method uses viewpoints from STEREO A and B, and SOHO/LASCO coronagraphs to determine the size and orientation of a CME flux rope as it starts to erupt from Sun. A flux rope created this way is inserted into an SDO/HMI vector magnetogram driven SW background obtained with the Multi-Scale Fluid-Kinetic Simulation Suite (MS-FLUKSS). Numerical results are compared with STEREO, SDO/AIA and SOHO/LASCO observations in particular in terms of the CME speed, acceleration and magnetic field structure.

Using Multi-Spacecraft Technique to Identify the Structure of Magnetic Field in CMEs

NASA Astrophysics Data System (ADS)

Al-haddad, N. A.; Jacobs, C.; Poedts, S.; Moestl, C.; Farrugia, C. J.; Lugaz, N.

2013-12-01

In order to understand the magnetic field structure of coronal mass ejections (CMEs), it is often required to investigate its local configuration at different positions of the CME. While this could be very challenging to implement observationally; it is rather applicable when using numerical simulations. In this work, we study the properties of a simulated CME using multi-spacecraft technique. We have shown previously how the reconstruction of magnetic fields from a single spacecraft, may yield misleading results. Here, we look into the reconstruction of the magnetic field using sets of two, and three spacecrafts at different longitudes, and discuss the effectiveness of this technique. This type of work can pave the way for future out-of-the-ecliptic missions such as Solar Probe or Solar Orbiter. Grad-Shafranov reconstruction of simulated satellite measurements of a CME containing writhed field lines.

CME productivity associated with Solar Flare peak X-ray emission flux

NASA Astrophysics Data System (ADS)

Suryanarayana, G. S.; Balakrishna, K. M.

2018-05-01

It is often noticed that the occurrence rate of Coronal Mass Ejections (CMEs) increases with increase in flare duration where peak flux too increase. However, there is no complete association between the duration and peak flux. Distinct characteristics have been reported for active regions (ARs) where flares and CMEs occur in contrast to ARs where flares alone occur. It is observed that peak flux of flares is higher when associated with CMEs compared to peak flux of flares with which CMEs are not associated. In other words, it is likely that flare duration and peak flux are independently affected by distinct active region dynamics. Hence, we examine the relative ability of flare duration and peak flux in enhancing the CME productivity. We report that CME productivity is distinctly higher in association with the enhancement of flare peak flux in comparison to corresponding enhancement of flare duration.

The solar cycle variation of the rates of CMEs and related activity

NASA Technical Reports Server (NTRS)

Webb, David F.

1991-01-01

Coronal mass ejections (CMEs) are an important aspect of the physics of the corona and heliosphere. This paper presents results of a study of occurrence frequencies of CMEs and related activity tracers over more than a complete solar activity cycle. To properly estimate occurrence rates, observed CME rates must be corrected for instrument duty cycles, detection efficiencies away from the skyplane, mass detection thresholds, and geometrical considerations. These corrections are evaluated using CME data from 1976-1989 obtained with the Skylab, SMM and SOLWIND coronagraphs and the Helios-2 photometers. The major results are: (1) the occurrence rate of CMEs tends to track the activity cycle in both amplitude and phase; (2) the corrected rates from different instruments are reasonably consistent; and (3) over the long term, no one class of solar activity tracer is better correlated with CME rate than any other (with the possible exception of type II bursts).

First Simultaneous Views of the Axial and Lateral Perspectives of a Coronal Mass Ejection

NASA Astrophysics Data System (ADS)

Cabello, I.; Cremades, H.; Balmaceda, L.; Dohmen, I.

2016-08-01

The different appearances exhibited by coronal mass ejections (CMEs) are believed to be in part the result of different orientations of their main axis of symmetry, consistent with a flux-rope configuration. There are observational reports of CMEs seen along their main axis (axial perspective) and perpendicular to it (lateral perspective), but no simultaneous observations of both perspectives from the same CME have been reported to date. The stereoscopic views of the telescopes onboard the Solar-Terrestrial Relations Observatory (STEREO) twin spacecraft, in combination with the views from the Solar and Heliospheric Observatory (SOHO) and the Solar Dynamics Observatory (SDO), allow us to study the axial and lateral perspectives of a CME simultaneously for the first time. In addition, this study shows that the lateral angular extent ( L) increases linearly with time, while the angular extent of the axial perspective ( D) presents this behavior only from the low corona to {≈} 5 R_{⊙}, where it slows down. The ratio L/D ≈ 1.6 obtained here as the average over several points in time is consistent with measurements of L and D previously performed on events exhibiting only one of the perspectives from the single vantage point provided by SOHO.

3D Dynamics of Magnetic Flux Ropes Across Scales: Solar Eruptions and Sun-Earth Plasma Coupling

NASA Astrophysics Data System (ADS)

Chen, James

2012-10-01

Central to the understanding of the eruptive phenomena on the Sun and their impact on the terrestrial plasma environment is the dynamics of coronal mass ejections (CMEs)---a 3D magnetic flux rope configuration---and the evolution of their magnetic fields. I will discuss the basic physics of CME eruption and solar flare energy release in the context of the analytic erupting flux rope model of CMEs. In this ideal MHD model, a CME is treated as a 3D flux rope with its two stationary footpoints anchored in the Sun. The model structure is non-axisymmetric and embedded in a model corona/solar wind. The initial flux rope is driven out of equilibrium by ``injection'' of poloidal flux and propagates under the Lorentz hoop force from the Sun to 1 AU, across a wide range of spatial and temporal scales. Comparisons of the model results and recent STEREO observations show that the solutions that best fit the observed CME position-time data (to within 1-2% of data) also correctly replicate the temporal profiles of associated flare X-ray emissions (GOES data) and the in situ magnetic field and plasma data of the CME ejecta at 1 AU where such data are available (e.g., ACE and STEREO/IMPAXCT/PLASTIC data), providing a unified basis of understanding CME dynamics and flare energetics.

Imaging Coronal Mass Ejections and Large-Scale Solar Wind Structure Using IPS and Thomson-Scattered Sunlight (Invited)

NASA Astrophysics Data System (ADS)

Clover, J. M.; Jackson, B. V.; Buffington, A.; Hick, P. P.; Bisi, M. M.; Tokumaru, M.; Fujiki, K.

2010-12-01

The Solar Mass Ejection Imager (SMEI) observes Thomson-scattered white light from heliospheric electrons across almost all of the sky nearly all of the time since early 2003. Interplanetary scintillation (IPS) observations of velocity and g-level provide similar structure information but with a less-complete sky-and-time coverage. The Solar TErrestrial RElations Observatory (STEREO) twin spacecraft outer Heliospheric Imagers (HI-2) currently image the heliosphere in Thomson-scattered light near the ecliptic plane far from Earth. The Solar-Terrestrial Environment Laboratory (STELab) IPS observations provide IPS velocity and g-level values, which in conjunction with our tomographic reconstruction program, yield velocities and densities of the inner heliosphere in three dimensions. The same tomographic program substitutes SMEI Thomson-scattering brightness information for the g-level values to derive heliospheric densities from these data alone. We look at the global structure of the heliosphere concentrating mainly on three events from 2007 through the rise phase of Solar Cycle 24. The first event, observed in both the IPS and SMEI defines the three-dimensional velocity and density structure around the time of the shock observed at Earth on 02:02 UT 17 December 2007. The second event, seen only by SMEI, is that of the 23-26 April 2008 coronal mass ejection (CME) and its interplanetary counterpart. The third event is the CME (and its interplanetary counterpart) that took place 17 January 2010 and arrived at STEREO-B about four days later. For each event, we isolate the particular portion of the heliosphere attributed to the transient density structure using our tomographic technique, and then estimate its extent.

Radio observations of a coronal mass ejection induced depletion in the outer solar corona

NASA Astrophysics Data System (ADS)

Ramesh, R.; Sastry, Ch. V.

2000-06-01

We report the first low frequency radio observations of a depletion that occurred in the outer solar corona in the aftermath of the CME event of 1986 June 5, with the large E-W one dimensional grating interferometer at the Gauribidanur radio observatory. We estimated the mass loss associated with the depletion and found that it agrees well with the value obtained through white light observations of the event. The radio brightness temperature at the location of the depletion was less by a factor of ~ 7 compared to the ambient. The angular extent over which the decrease in brightness took place was <= 3'. The electron density variation was found to be proportional to r-10. Since observations at different wavelength bands have different physical origins, the radio method might be useful in independently estimating the characteristics of CME induced coronal depletions.

Twisted Fields

NASA Image and Video Library

2017-12-08

OHO captured this image of a CME from the side – but the structure looks much different from the classic light bulb CME. The filament of material bursting off the sun has a helical magnetic structure, which is unraveling like a piece of yarn during the eruption. Credit: ESA/NASA/SOHO..---..CME WEEK: What To See in CME Images Two main types of explosions occur on the sun: solar flares and coronal mass ejections. Unlike the energy and x-rays produced in a solar flare – which can reach Earth at the speed of light in eight minutes – coronal mass ejections are giant, expanding clouds of solar material that take one to three days to reach Earth. Once at Earth, these ejections, also called CMEs, can impact satellites in space or interfere with radio communications. During CME WEEK from Sept. 22 to 26, 2014, we explore different aspects of these giant eruptions that surge out from the star we live with. When a coronal mass ejection blasts off the sun, scientists rely on instruments called coronagraphs to track their progress. Coronagraphs block out the bright light of the sun, so that the much fainter material in the solar atmosphere -- including CMEs -- can be seen in the surrounding space. CMEs appear in these images as expanding shells of material from the sun's atmosphere -- sometimes a core of colder, solar material (called a filament) from near the sun's surface moves in the center. But mapping out such three-dimensional components from a two-dimensional image isn't easy. Watch the slideshow to find out how scientists interpret what they see in CME pictures. The images in the slideshow are from the three sets of coronagraphs NASA currently has in space. One is on the joint European Space Agency and NASA Solar and Heliospheric Observatory, or SOHO. SOHO launched in 1995, and sits between Earth and the sun about a million miles away from Earth. The other two coronagraphs are on the two spacecraft of the NASA Solar Terrestrial Relations Observatory, or STEREO, mission, which launched in 2006. The two STEREO spacecraft are both currently viewing the far side of the sun. Together these instruments help scientists create a three-dimensional model of any CME as its journey unfolds through interplanetary space. Such information can show why a given characteristic of a CME close to the sun might lead to a given effect near Earth, or any other planet in the solar system...NASA image use policy. NASA Goddard Space Flight Center enables NASA’s mission through four scientific endeavors: Earth Science, Heliophysics, Solar System Exploration, and Astrophysics. Goddard plays a leading role in NASA’s accomplishments by contributing compelling scientific knowledge to advance the Agency’s mission. Follow us on Twitter Like us on Facebook Find us on Instagram

Fitting and Reconstruction of Thirteen Simple Coronal Mass Ejections

NASA Astrophysics Data System (ADS)

Al-Haddad, Nada; Nieves-Chinchilla, Teresa; Savani, Neel P.; Lugaz, Noé; Roussev, Ilia I.

2018-05-01

Coronal mass ejections (CMEs) are the main drivers of geomagnetic disturbances, but the effects of their interaction with Earth's magnetic field depend on their magnetic configuration and orientation. Fitting and reconstruction techniques have been developed to determine important geometrical and physical CME properties, such as the orientation of the CME axis, the CME size, and its magnetic flux. In many instances, there is disagreement between different methods but also between fitting from in situ measurements and reconstruction based on remote imaging. This could be due to the geometrical or physical assumptions of the models, but also to the fact that the magnetic field inside CMEs is only measured at one point in space as the CME passes over a spacecraft. In this article we compare three methods that are based on different assumptions for measurements by the Wind spacecraft for 13 CMEs from 1997 to 2015. These CMEs are selected from the interplanetary coronal mass ejections catalog on https://wind.nasa.gov/ICMEindex.php because of their simplicity in terms of: 1) slow expansion speed throughout the CME and 2) weak asymmetry in the magnetic field profile. This makes these 13 events ideal candidates for comparing codes that do not include expansion or distortion. We find that for these simple events, the codes are in relatively good agreement in terms of the CME axis orientation for six of the 13 events. Using the Grad-Shafranov technique, we can determine the shape of the cross-section, which is assumed to be circular for the other two models, a force-free fitting and a circular-cylindrical non force-free fitting. Five of the events are found to have a clear circular cross-section, even when this is not a precondition of the reconstruction. We make an initial attempt at evaluating the adequacy of the different assumptions for these simple CMEs. The conclusion of this work strongly suggests that attempts at reconciling in situ and remote-sensing views of CMEs must take into consideration the compatibility of the different models with specific CME structures to better reproduce flux ropes.

Investigation of the Large Scale Evolution and Topology of Coronal Mass Ejections in the Solar Wind

NASA Technical Reports Server (NTRS)

Riley, Pete

2001-01-01

This investigation is concerned with the large-scale evolution and topology of coronal mass ejections (CMEs) in the solar wind. During the course of this three-year investigation, we have undertaken a number of studies that are discussed in more detail in this report. For example, we conducted an analysis of all CMEs observed by the Ulysses spacecraft during its in-ecliptic phase between 1 and 5 AU. In addition to studying the properties of the ejecta, we also analyzed the shocks that could be unambiguously associated with the fast CMEs. We also analyzed a series of 'density holes' observed in the solar wind that bear many similarities with CMEs. To complement this analysis, we conducted a series of 1-D and 2 1/2-D fluid, MHD, and hybrid simulations to address a number of specific issues related to CME evolution in the solar wind. For example, we used fluid simulations to address the interpretation of negative electron temperature-density relationships often observed within CME/cloud intervals. As part of this investigation, a number of fruitful international collaborations were forged. Finally, the results of this work were presented at nine scientific meetings and communicated in eight scientific, refereed papers.

IMPULSIVE ACCELERATION OF CORONAL MASS EJECTIONS. II. RELATION TO SOFT X-RAY FLARES AND FILAMENT ERUPTIONS

DOE Office of Scientific and Technical Information (OSTI.GOV)

Bein, B. M.; Berkebile-Stoiser, S.; Veronig, A. M.

2012-08-10

Using high time cadence images from the STEREO EUVI, COR1, and COR2 instruments, we derived detailed kinematics of the main acceleration stage for a sample of 95 coronal mass ejections (CMEs) in comparison with associated flares and filament eruptions. We found that CMEs associated with flares reveal on average significantly higher peak accelerations and lower acceleration phase durations, initiation heights, and heights, at which they reach their peak velocities and peak accelerations. This means that CMEs that are associated with flares are characterized by higher and more impulsive accelerations and originate from lower in the corona where the magnetic fieldmore » is stronger. For CMEs that are associated with filament eruptions we found only for the CME peak acceleration significantly lower values than for events that were not associated with filament eruptions. The flare rise time was found to be positively correlated with the CME acceleration duration and negatively correlated with the CME peak acceleration. For the majority of the events the CME acceleration starts before the flare onset (for 75% of the events) and the CME acceleration ends after the soft X-ray (SXR) peak time (for 77% of the events). In {approx}60% of the events, the time difference between the peak time of the flare SXR flux derivative and the peak time of the CME acceleration is smaller than {+-}5 minutes, which hints at a feedback relationship between the CME acceleration and the energy release in the associated flare due to magnetic reconnection.« less

A Statistical Study of Interplanetary Type II Bursts: STEREO Observations

NASA Astrophysics Data System (ADS)

Krupar, V.; Eastwood, J. P.; Magdalenic, J.; Gopalswamy, N.; Kruparova, O.; Szabo, A.

2017-12-01

Coronal mass ejections (CMEs) are the primary cause of the most severe and disruptive space weather events such as solar energetic particle (SEP) events and geomagnetic storms at Earth. Interplanetary type II bursts are generated via the plasma emission mechanism by energetic electrons accelerated at CME-driven shock waves and hence identify CMEs that potentially cause space weather impact. As CMEs propagate outward from the Sun, radio emissions are generated at progressively at lower frequencies corresponding to a decreasing ambient solar wind plasma density. We have performed a statistical study of 153 interplanetary type II bursts observed by the two STEREO spacecraft between March 2008 and August 2014. These events have been correlated with manually-identified CMEs contained in the Heliospheric Cataloguing, Analysis and Techniques Service (HELCATS) catalogue. Our results confirm that faster CMEs are more likely to produce interplanetary type II radio bursts. We have compared observed frequency drifts with white-light observations to estimate angular deviations of type II burst propagation directions from radial. We have found that interplanetary type II bursts preferably arise from CME flanks. Finally, we discuss a visibility of radio emissions in relation to the CME propagation direction.

The radial speed-expansion speed relation for Earth-directed CMEs

NASA Astrophysics Data System (ADS)

Mäkelä, P.; Gopalswamy, N.; Yashiro, S.

2016-05-01

Earth-directed coronal mass ejections (CMEs) are the main drivers of major geomagnetic storms. Therefore, a good estimate of the disturbance arrival time at Earth is required for space weather predictions. The STEREO and SOHO spacecraft were viewing the Sun in near quadrature during January 2010 to September 2012, providing a unique opportunity to study the radial speed (Vrad)-expansion speed (Vexp) relationship of Earth-directed CMEs. This relationship is useful in estimating the Vrad of Earth-directed CMEs, when they are observed from Earth view only. We selected 19 Earth-directed CMEs observed by the Large Angle and Spectrometric Coronagraph (LASCO)/C3 coronagraph on SOHO and the Sun Earth Connection Coronal and Heliospheric Investigation (SECCHI)/COR2 coronagraph on STEREO during January 2010 to September 2012. We found that of the three tested geometric CME models the full ice-cream cone model of the CME describes best the Vrad-Vexp relationship, as suggested by earlier investigations. We also tested the prediction accuracy of the empirical shock arrival (ESA) model proposed by Gopalswamy et al. (2005a), while estimating the CME propagation speeds from the CME expansion speeds. If we use STEREO observations to estimate the CME width required to calculate the Vrad from the Vexp measurements, the mean absolute error (MAE) of the shock arrival times of the ESA model is 8.4 h. If the LASCO measurements are used to estimate the CME width, the MAE still remains below 17 h. Therefore, by using the simple Vrad-Vexp relationship to estimate the Vrad of the Earth-directed CMEs, the ESA model is able to predict the shock arrival times with accuracy comparable to most other more complex models.

Two-Step Forecast of Geomagnetic Storm Using Coronal Mass Ejection and Solar Wind Condition

NASA Technical Reports Server (NTRS)

Kim, R.-S.; Moon, Y.-J.; Gopalswamy, N.; Park, Y.-D.; Kim, Y.-H.

2014-01-01

To forecast geomagnetic storms, we had examined initially observed parameters of coronal mass ejections (CMEs) and introduced an empirical storm forecast model in a previous study. Now we suggest a two-step forecast considering not only CME parameters observed in the solar vicinity but also solar wind conditions near Earth to improve the forecast capability. We consider the empirical solar wind criteria derived in this study (Bz = -5 nT or Ey = 3 mV/m for t = 2 h for moderate storms with minimum Dst less than -50 nT) (i.e. Magnetic Field Magnitude, B (sub z) less than or equal to -5 nanoTeslas or duskward Electrical Field, E (sub y) greater than or equal to 3 millivolts per meter for time greater than or equal to 2 hours for moderate storms with Minimum Disturbance Storm Time, Dst less than -50 nanoTeslas) and a Dst model developed by Temerin and Li (2002, 2006) (TL [i.e. Temerin Li] model). Using 55 CME-Dst pairs during 1997 to 2003, our solar wind criteria produce slightly better forecasts for 31 storm events (90 percent) than the forecasts based on the TL model (87 percent). However, the latter produces better forecasts for 24 nonstorm events (88 percent), while the former correctly forecasts only 71 percent of them. We then performed the two-step forecast. The results are as follows: (i) for 15 events that are incorrectly forecasted using CME parameters, 12 cases (80 percent) can be properly predicted based on solar wind conditions; (ii) if we forecast a storm when both CME and solar wind conditions are satisfied (n, i.e. cap operator - the intersection set that is comprised of all the elements that are common to both), the critical success index becomes higher than that from the forecast using CME parameters alone, however, only 25 storm events (81 percent) are correctly forecasted; and (iii) if we forecast a storm when either set of these conditions is satisfied (?, i.e. cup operator - the union set that is comprised of all the elements of either or both), all geomagnetic storms are correctly forecasted.

Prediction of Shock Arrival Times from CME and Flare Data

NASA Technical Reports Server (NTRS)

Nunez, Marlon; Nieves-Chinchilla, Teresa; Pulkkinen, Antti

2016-01-01

This paper presents the Shock ARrival Model (SARM) for predicting shock arrival times for distances from 0.72 AU to 8.7 AU by using coronal mass ejections (CME) and flare data. SARM is an aerodynamic drag model described by a differential equation that has been calibrated with a dataset of 120 shocks observed from 1997 to 2010 by minimizing the mean absolute error (MAE), normalized to 1 AU. SARM should be used with CME data (radial, earthward or plane-of-sky speeds), and flare data (peak flux, duration, and location). In the case of 1 AU, the MAE and the median of absolute errors were 7.0 h and 5.0 h respectively, using the available CMEflare data. The best results for 1 AU (an MAE of 5.8 h) were obtained using both CME data, either radial or cone-model-estimated speeds, and flare data. For the prediction of shock arrivals at distances from 0.72 AU to 8.7 AU, the normalized MAE and the median were 7.1 h and 5.1 h respectively, using the available CMEflare data. SARM was also calibrated to be used with CME data alone or flare data alone, obtaining normalized MAE errors of 8.9 h and 8.6 h respectively for all shock events. The model verification was carried out with an additional dataset of 20 shocks observed from 2010 to 2012 with radial CME speeds to compare SARM with the empirical ESA model [Gopalswamy et al., 2005a] and the numerical MHD-based ENLIL model [Odstrcil et al., 2004]. The results show that the ENLIL's MAE was lower than the SARM's MAE, which was lower than the ESA's MAE. The SARM's best results were obtained when both flare and true CME speeds were used.

Challenging Some Contemporary Views of Coronal Mass Ejections. I. The Case for Blast Waves

NASA Astrophysics Data System (ADS)

Howard, T. A.; Pizzo, V. J.

2016-06-01

Since the closure of the “solar flare myth” debate in the mid-1990s, a specific narrative of the nature of coronal mass ejections (CMEs) has been widely accepted by the solar physics community. This narrative describes structured magnetic flux ropes at the CME core that drive the surrounding field plasma away from the Sun. This narrative replaced the “traditional” view that CMEs were blast waves driven by solar flares. While the flux rope CME narrative is supported by a vast quantity of measurements made over five decades, it does not adequately describe every observation of what have been termed CME-related phenomena. In this paper we present evidence that some large-scale coronal eruptions, particularly those associated with EIT waves, exhibit characteristics that are more consistent with a blast wave originating from a localized region (such as a flare site) rather than a large-scale structure driven by an intrinsic flux rope. We present detailed examples of CMEs that are suspected blast waves and flux ropes, and show that of our small sample of 22 EIT-wave-related CMEs, 91% involve a blast wave as at least part of the eruption, and 50% are probably blast waves exclusively. We conclude with a description of possible signatures to look for in determining the difference between the two types of CMEs and with a discussion on modeling efforts to explore this possibility.

Chromosphere to 1 AU Simulation of the 2011 March 7th Event: A Comprehensive Study of Coronal Mass Ejection Propagation

NASA Astrophysics Data System (ADS)

Jin, M.; Manchester, W. B.; van der Holst, B.; Sokolov, I.; Tóth, G.; Vourlidas, A.; de Koning, C. A.; Gombosi, T. I.

2017-01-01

We perform and analyze the results of a global magnetohydrodynamic simulation of the fast coronal mass ejection (CME) that occurred on 2011 March 7. The simulation is made using the newly developed Alfvén Wave Solar Model (AWSoM), which describes the background solar wind starting from the upper chromosphere and extends to 24 R⊙. Coupling AWSoM to an inner heliosphere model with the Space Weather Modeling Framework extends the total domain beyond the orbit of Earth. Physical processes included in the model are multi-species thermodynamics, electron heat conduction (both collisional and collisionless formulations), optically thin radiative cooling, and Alfvén-wave turbulence that accelerates and heats the solar wind. The Alfvén-wave description is physically self-consistent, including non-Wentzel-Kramers-Brillouin reflection and physics-based apportioning of turbulent dissipative heating to both electrons and protons. Within this model, we initiate the CME by using the Gibson-Low analytical flux rope model and follow its evolution for days, in which time it propagates beyond STEREO A. A detailed comparison study is performed using remote as well as in situ observations. Although the flux rope structure is not compared directly due to lack of relevant ejecta observation at 1 au in this event, our results show that the new model can reproduce many of the observed features near the Sun (e.g., CME-driven extreme ultraviolet [EUV] waves, deflection of the flux rope from the coronal hole, “double-front” in the white light images) and in the heliosphere (e.g., shock propagation direction, shock properties at STEREO A).

Interactions of Dust Grains with Coronal Mass Ejections and Solar Cycle Variations of the F-Coronal Brightness

NASA Technical Reports Server (NTRS)

Ragot, B. R.; Kahler, S. W.

2003-01-01

The density of interplanetary dust increases sunward to reach its maximum in the F corona, where its scattered white-light emission dominates that of the electron K corona above about 3 Solar Radius. The dust will interact with both the particles and fields of antisunward propagating coronal mass ejections (CMEs). To understand the effects of the CME/dust interactions we consider the dominant forces, with and without CMEs. acting on the dust in the 3-5 Solar Radius region. Dust grain orbits are then computed to compare the drift rates from 5 to 3 Solar Radius. for periods of minimum and maximum solar activity, where a simple CME model is adopted to distinguish between the two periods. The ion-drag force, even in the quiet solar wind, reduces the drift time by a significant factor from its value estimated with the Poynting-Robertson drag force alone. The ion-drag effects of CMEs result in even shorter drift times of the large (greater than or approx. 3 microns) dust grains. hence faster depletion rates and lower dust-pain densities, at solar maxima. If dominated by thermal emission, the near-infrared brightness will thus display solar cycle variations close to the dust plane of symmetry. While trapping the smallest of the grains, the CME magnetic fields also scatter the grains of intermediate size (0.1-3 microns) in latitude. If light scattering by small grains close to the Sun dominates the optical brightness. the scattering by the CME magnetic fields will result in a solar cycle variation of the optical brightness distribution not exceeding 100% at high latitudes, with a higher isotropy reached at solar maxima. A good degree of latitudinal isotropy is already reached at low solar activity since the magnetic fields of the quiet solar wind so close to the Sun are able to scatter the small (less than or approx. 3 microns) grains up to the polar regions in only a few days or less, producing strong perturbations of their trajectories in less than half their orbital periods. Finally, we consider possible observable consequences of individual CME/dust interactions. We show that the dust grains very likely have no observable effect on the dynamics of CMEs. The effect of an individual CME on the dust grains, however, might serve as a forecasting tool for the directions and amplitudes of the magnetic fields within the CME.

THE COUPLED EVOLUTION OF ELECTRONS AND IONS IN CORONAL MASS EJECTION-DRIVEN SHOCKS

DOE Office of Scientific and Technical Information (OSTI.GOV)

Manchester IV, W. B.; Van der Holst, B.; Toth, G.

2012-09-01

We present simulations of coronal mass ejections (CMEs) performed with a new two-temperature coronal model developed at the University of Michigan, which is able to address the coupled thermodynamics of the electron and proton populations in the context of a single fluid. This model employs heat conduction for electrons, constant adiabatic index ({gamma} = 5/3), and includes Alfven wave pressure to accelerate the solar wind. The Wang-Sheeley-Arge empirical model is used to determine the Alfven wave pressure necessary to produce the observed bimodal solar wind speed. The Alfven waves are dissipated as they propagate from the Sun and heat protonsmore » on open magnetic field lines to temperatures above 2 MK. The model is driven by empirical boundary conditions that includes GONG magnetogram data to calculate the coronal field, and STEREO/EUVI observations to specify the density and temperature at the coronal boundary by the Differential Emission Measure Tomography method. With this model, we simulate the propagation of fast CMEs and study the thermodynamics of CME-driven shocks. Since the thermal speed of the electrons greatly exceeds the speed of the CME, only protons are directly heated by the shock. Coulomb collisions low in the corona couple the protons and electrons allowing heat exchange between the two species. However, the coupling is so brief that the electrons never achieve more than 10% of the maximum temperature of the protons. We find that heat is able to conduct on open magnetic field lines and rapidly propagates ahead of the CME to form a shock precursor of hot electrons.« less

Statistical Study of Magnetic Nonpotential Measures in Confined and Eruptive Flares

NASA Astrophysics Data System (ADS)

Vasantharaju, N.; Vemareddy, P.; Ravindra, B.; Doddamani, V. H.

2018-06-01

Using Solar Dynamics Observatory/Helioseismic and Magnetic Imager vector magnetic field observations, we studied the relation between the degree of magnetic non-potentiality with the observed flare/coronal mass ejection (CME) in active regions (ARs). From a sample of 77 flare/CME cases, we found in general that the degree of non-potentiality is positively correlated with the flare strength and the associated CME speed. Since the magnetic flux in the flare-ribbon area is more related to the reconnection, we trace the strong gradient polarity inversion line (SGPIL) and Schrijver’s R value manually along the flare-ribbon extent. Manually detected SGPIL length and R values show higher correlation with the flare strength and CME speed than automatically traced values without flare-ribbon information. This highlights the difficulty of predicting the flare strength and CME speed a priori from the pre-flare magnetograms used in flare prediction models. Although the total potential magnetic energy proxies show a weak positive correlation, the decrease in free energy exhibits a higher correlation (0.56) with the flare strength and CME speed. Moreover, eruptive flares have thresholds of SGPIL length (31 Mm), R value (1.6 × 1019 Mx), and free energy decrease (2 × 1031 erg) compared to confined flares. In 90% of eruptive flares, the decay-index curve is steeper, reaching {n}crit}=1.5 within 42 Mm, whereas it is beyond this value in >70% of confined flares. While indicating improved statistics in the predictive capability of AR eruptive behavior with flare-ribbon information, our study provides threshold magnetic properties for a flare to be eruptive.

Two Coronal Mass Ejections Events Close to the Total Solar Eclipse Aug. 11, 1999

NASA Astrophysics Data System (ADS)

Churyumov, K. I.; Ivanchuk, V. I.

We present some results of exploration of the solar corona on the basis of analysis of its images obtained in Romania by K.I.Churyumov and in Bulgaria by V.Mormyl' and S.Kharchuk Aug. 11 1999. Structure of the corona is characterized by the presence of numerous power and thin rays which have mainly radial orientation in regard to the Sun. The high-latitude rays of the north hemisphere (especially in the NE sector) are inclined in the direction of the N-pole. The interesting peculiarity of the solar corona Aug. 11 1999 is the existence of the sabre-like thin double ray on the NE-limb, which goes from the solar limb region at p ~ 50o. It is close to the peculiar center of ``repulsion'', which is observed for the fan of rays of the E-limb. We proposed that the similar rays and the observed center of ``repulsion'' were an indicator (postcursor) which shows that in this place of the corona the phenomena of the coronal mass ejections (CME) of the coronal plasma occurred. This views was confirmed by observations of the solar corona with the help of the Lasco C2 coronograph of SOHO Aug. 10/11 1999. In the region of the NW-quadrant and near the W-equator the enough sharp transequatorial arc by height ~ 0.7Rsolar with the center at ϕo = +10 deg is detected. It is nonfull arcs which intersects set of rays structures and near its foundation on the altitude /~ 0.3Rsolar there is a coronal condensation with characteristic sizes Δ l ~ 0.1Rsolar. We think that it is tied with development of a coronal mass ejection (CME) detected by the coronograph Lasco C2 of SOHO Aug. 11/12, 1999. On the best pictures it is seen that CME had the angle sizes ~ 90 deg and filled in nearly the all NW quadrant as a not uniform buble. On the basis of the published data we determined several

MHD simulation of the Bastille day event

DOE Office of Scientific and Technical Information (OSTI.GOV)

Linker, Jon, E-mail: linkerj@predsci.com; Torok, Tibor; Downs, Cooper

2016-03-25

We describe a time-dependent, thermodynamic, three-dimensional MHD simulation of the July 14, 2000 coronal mass ejection (CME) and flare. The simulation starts with a background corona developed using an MDI-derived magnetic map for the boundary condition. Flux ropes using the modified Titov-Demoulin (TDm) model are used to energize the pre-event active region, which is then destabilized by photospheric flows that cancel flux near the polarity inversion line. More than 10{sup 33} ergs are impulsively released in the simulated eruption, driving a CME at 1500 km/s, close to the observed speed of 1700km/s. The post-flare emission in the simulation is morphologically similarmore » to the observed post-flare loops. The resulting flux rope that propagates to 1 AU is similar in character to the flux rope observed at 1 AU, but the simulated ICME center passes 15° north of Earth.« less

Impact of Major Coronal Mass Ejections on Geospace during 2005 September 7-13

NASA Astrophysics Data System (ADS)

Wang, Yuming; Xue, Xianghui; Shen, Chenglong; Ye, Pinzhong; Wang, S.; Zhang, Jie

2006-07-01

We have analyzed five major CMEs originating from NOAA active region (AR) 808 during the period of 2005 September 7-13, when the AR 808 rotated from the east limb to near solar meridian. Several factors that affect the probability of the CMEs' encounter with the Earth are demonstrated. The solar and interplanetary observations suggest that the second and third CMEs, originating from E67° and E47°, respectively, encountered the Earth, while the first CME originating from E77° missed the Earth, and the last two CMEs, although originating from E39° and E10°, respectively, probably only grazed the Earth. On the basis of our ice cream cone mode and CME deflection model, we find that the CME span angle and deflection are important for the probability of encountering Earth. The large span angles allowed the middle two CMEs to hit the Earth, even though their source locations were not close to the solar central meridian. The significant deflection made the first CME totally miss the Earth even though it also had wide span angle. The deflection may also have made the last CME nearly miss the Earth even though it originated close to the disk center. We suggest that, in order to effectively predict whether a CME will encounter the Earth, the factors of the CME source location, the span angle, and the interplanetary deflection should all be taken into account.

Impact of major coronal mass ejections on geo-space during September 7 -- 13, 2005

NASA Astrophysics Data System (ADS)

Wang, Y.; Xue, X.; Shen, C.; Ye, P.; Wang, S.; Zhang, J.

2006-05-01

We have analyzed five major CMEs originating from NOAA active region (AR) 808 during the period of September 7 to 13, 2005, when the AR 808 rotated from the east limb to near solar meridian. Several factors that affect the probability of the CMEs' encounter with the Earth are demonstrated. The solar and interplanetary observations suggest that the 2nd and 3rd CMEs, originating from E67 and E47 respectively, encountered the Earth, while the 1st CME originating from E77 missed the Earth, and the last two CMEs, originating from E39 and E10 respectively, probably only grazed the Earth. Based on our ice-cream cone model (Xue et al. 2005a) and CME deflection model (Wang et al. 2004b), we find that the CME span angle and deflection are important for the probability of encountering. The large span angles make middle two CMEs hit the Earth, though their source locations were not close to the solar central meridian. The significant deflection makes the first CME totally missed the Earth though it also had wide span angle. The deflection may also make the last CME nearly missed the Earth though it originated close to the disk center. We suggest that, in order to effectively predict whether a CME will encounter the Earth, the factors of the CME source location, the span angle, and the interplanetary deflection should all be taken into account.

Ground Level Enhancement in the 2014 January 6 Solar Energetic Particle Event

NASA Technical Reports Server (NTRS)

Thakur, N.; Gopalswamy, N.; Xie, H.; Makela, P.; Yashiro, S.; Akiyama, S.; Davila, J. M.

2014-01-01

We present a study of the 2014 January 6 solar energetic particle event which produced a small ground level enhancement (GLE), making it the second GLE of this unusual solar cycle 24. This event was primarily observed by the South Pole neutron monitors (increase of approximately 2.5 percent) while a few other neutron monitors recorded smaller increases. The associated coronal mass ejection (CME) originated behind the western limb and had a speed of 1960 kilometers per second. The height of the CME at the start of the associated metric type II radio burst, which indicates the formation of a strong shock, was measured to be 1.61 solar radii using a direct image from STEREO-A/EUVI. The CME height at the time of the GLE particle release (determined using the South Pole neutron monitor data) was directly measured as 2.96 solar radii based on STEREO-A/COR1 white-light observations. These CME heights are consistent with those obtained for GLE71, the only other GLE of the current cycle, as well as cycle-23 GLEs derived using back-extrapolation. GLE72 is of special interest because it is one of only two GLEs of cycle 24, one of two behind-the-limb GLEs, and one of the two smallest GLEs of cycles 23 and 24.

White-Light and Radioastronomical Remote-Sensing of Coronal Mass Ejections

NASA Astrophysics Data System (ADS)

Kooi, Jason E.; Spangler, Steven R.

2017-01-01

Coronal mass ejections (CMEs) are large-scale eruptions of plasma from the Sun that play an important role in space weather. Faraday rotation (FR) is the rotation of the plane of polarization that results when a linearly polarized signal passes through a magnetized plasma (such as a CME) and is proportional to the path integral through the plasma of the electron density and the line-of-sight component of the magnetic field. FR observations of a source near the Sun can provide information on the plasma structure of a CME shortly after launch; however, separating the contribution of the plasma density from the line-of-sight magnetic field is challenging.We report on simultaneous white-light and radio observations made of three CMEs in August 2012. We made radio observations using the Very Large Array (VLA) at 1 - 2 GHz frequencies of a "constellation" of radio sources through the solar corona at heliocentric distances that ranged from 6 - 15 solar radii: two sources (0842+1835 and 0900+1832) were occulted by a single CME and one source (0843+1547) was occulted by two CMEs. In addition to our radioastronomical observations, which represent one of the first active hunts for CME Faraday rotation since Bird et al. (1985) and the first active hunt using the VLA, we obtained white-light coronagraph images from the LASCO/C3 instrument to determine the Thomson scattering brightness (BT), providing a means to independently estimate the plasma density and determine its contribution to the observed Faraday rotation.A constant density force-free flux rope embedded in the background corona was used to model the effects of the CMEs on BT and FR and infer the plasma densities (6 - 22 x 103 cm-3) and axial magnetic field strengths (2 - 12 mG) for the three CMEs. A single flux rope model successfully reproduces the observed BT and FR profiles for 0842+1835 and 0900+1832; however 0843+1547 was occulted by two CMEs. Using the multiple viewpoints provided by LASCO/C3 and STEREO-A/COR2, we model observations of 0843+1547 using two flux ropes embedded in the background corona and demonstrate the model's ability to successfully reproduce both BT and FR profiles.

What Properties of CMEs are Most Important for Space Weather?

NASA Technical Reports Server (NTRS)

Gopalswamy, Nat

2012-01-01

Severe space weather is characterized by intense particle radiation from the Sun and major geomagnetic storm caused by magnetized solar plasmas arriving at Earth. Coronal mass ejections (CMEs) are key players in both these aspects. CMEs traveling at super-Alfv nic speeds drive fast-mode MHD shocks that create the high levels of particle radiation. When a CME arrives at Earth, the CME-associated magnetic fields reconnect with Earth s magnetopause fields resulting in solar plasma entry into the magnetosphere and a geomagnetic storm depending on the magnetic structure of the CME. Particle radiation starts affecting geospace as soon as the CMEs leave the Sun and the geospace may be immersed in the radiation for several days. On the other hand, the geomagnetic storm happens only upon CME arrival at Earth. The requirements for the production of particles and magnetic storms by CMEs are different in a number of respects: solar source location, CME magnetic structure, conditions in the ambient solar wind, and shock-driving ability of CMEs. Intense shocks arriving at Earth have additional space weather effects such as sudden impulse that shrinks the magnetosphere often exposing satellites in geosynchronous orbit to the solar wind and energetic storm particle events. This paper highlights these space weather effects using CME observations space and ground based instruments during of solar cycles 23 and 24.

CME Expansion as the Driver of Metric Type II Shock Emission as Revealed by Self-consistent Analysis of High-Cadence EUV Images and Radio Spectrograms

NASA Astrophysics Data System (ADS)

Kouloumvakos, A.; Patsourakos, S.; Hillaris, A.; Vourlidas, A.; Preka-Papadema, P.; Moussas, X.; Caroubalos, C.; Tsitsipis, P.; Kontogeorgos, A.

2014-06-01

On 13 June 2010, an eruptive event occurred near the solar limb. It included a small filament eruption and the onset of a relatively narrow coronal mass ejection (CME) surrounded by an extreme ultraviolet (EUV) wave front recorded by the Solar Dynamics Observatory's (SDO) Atmospheric Imaging Assembly (AIA) at high cadence. The ejection was accompanied by a GOES M1.0 soft X-ray flare and a Type-II radio burst; high-resolution dynamic spectra of the latter were obtained by the Appareil de Routine pour le Traitement et l'Enregistrement Magnetique de l'Information Spectral (ARTEMIS IV) radio spectrograph. The combined observations enabled a study of the evolution of the ejecta and the EUV wave front and its relationship with the coronal shock manifesting itself as metric Type-II burst. By introducing a novel technique, which deduces a proxy of the EUV compression ratio from AIA imaging data and compares it with the compression ratio deduced from the band-split of the Type-II metric radio burst, we are able to infer the potential source locations of the radio emission of the shock on that AIA images. Our results indicate that the expansion of the CME ejecta is the source for both EUV and radio shock emissions. Early in the CME expansion phase, the Type-II burst seems to originate in the sheath region between the EUV bubble and the EUV shock front in both radial and lateral directions. This suggests that both the nose and the flanks of the expanding bubble could have driven the shock.

The Significance of the Influence of the CME Deflection in Interplanetary Space on the CME Arrival at Earth

NASA Astrophysics Data System (ADS)

Zhuang, Bin; Wang, Yuming; Shen, Chenglong; Liu, Siqing; Wang, Jingjing; Pan, Zonghao; Li, Huimin; Liu, Rui

2017-08-01

As one of the most violent astrophysical phenomena, coronal mass ejections (CMEs) have strong potential space weather effects. However, not all Earth-directed CMEs encounter the Earth and produce geo-effects. One reason is the deflected propagation of CMEs in interplanetary space. Although there have been several case studies clearly showing such deflections, it has not yet been statistically assessed how significantly the deflected propagation would influence the CME’s arrival at Earth. We develop an integrated CME-arrival forecasting (iCAF) system, assembling the modules of CME detection, three-dimensional (3D) parameter derivation, and trajectory reconstruction to predict whether or not a CME arrives at Earth, and we assess the deflection influence on the CME-arrival forecasting. The performance of iCAF is tested by comparing the two-dimensional (2D) parameters with those in the Coordinated Data Analysis Workshop (CDAW) Data Center catalog, comparing the 3D parameters with those of the gradual cylindrical shell model, and estimating the success rate of the CME Earth-arrival predictions. It is found that the 2D parameters provided by iCAF and the CDAW catalog are consistent with each other, and the 3D parameters derived by the ice cream cone model based on single-view observations are acceptable. The success rate of the CME-arrival predictions by iCAF with deflection considered is about 82%, which is 19% higher than that without deflection, indicating the importance of the CME deflection for providing a reliable forecasting. Furthermore, iCAF is a worthwhile project since it is a completely automatic system with deflection taken into account.

Modeling AWSoM CMEs with EEGGL: A New Approach for Space Weather Forecasting

NASA Astrophysics Data System (ADS)

Jin, M.; Manchester, W.; van der Holst, B.; Sokolov, I.; Toth, G.; Vourlidas, A.; de Koning, C. A.; Gombosi, T. I.

2015-12-01

The major source of destructive space weather is coronal mass ejections (CMEs). However, our understanding of CMEs and their propagation in the heliosphere is limited by the insufficient observations. Therefore, the development of first-principals numerical models plays a vital role in both theoretical investigation and providing space weather forecasts. Here, we present results of the simulation of CME propagation from the Sun to 1AU by combining the analytical Gibson & Low (GL) flux rope model with the state-of-art solar wind model AWSoM. We also provide an approach for transferring this research model to a space weather forecasting tool by demonstrating how the free parameters of the GL flux rope can be prescribed based on remote observations via the new Eruptive Event Generator by Gibson-Low (EEGGL) toolkit. This capability allows us to predict the long-term evolution of the CME in interplanetary space. We perform proof-of-concept case studies to show the capability of the model to capture physical processes that determine CME evolution while also reproducing many observed features both in the corona and at 1 AU. We discuss the potential and limitations of this model as a future space weather forecasting tool.

The solar cycle variation of coronal mass ejections and the solar wind mass flux

NASA Technical Reports Server (NTRS)

Webb, David F.; Howard, Russell A.

1994-01-01

Coronal mass ejections (CMEs) are an important aspect of coronal physics and a potentially significant contributor to perturbations of the solar wind, such as its mass flux. Sufficient data on CMEs are now available to permit study of their longer-term occurrency patterns. Here we present the results of a study of CME occurrence rates over more than a complete 11-year solar sunspot cycle and a comparison of these rates with those of other activity related to CMEs and with the solar wind particle flux at 1 AU. The study includes an evaluation of correlations to the CME rates, which include instrument duty cycles, visibility functions, mass detection thresholds, and geometrical considerations. The main results are as follows: (1) The frequency of occurrence of CMEs tends to track the solar activity cycle in both amplitude and phase; (2) the CME rates from different instruments, when corrected for both duty cycles and visibility functions, are reasonably consistent; (3) considering only longer-term averages, no one class of solar activity is better correlated with CME rate than any other; (4) the ratio of the annualized CME to solar wind mass flux tends to track the solar cycle; and (5) near solar maximum, CMEs can provide a significant fraction (i.e., approximately equals 15%) of the average mass flux to the near-ecliptic solar wind.

Which Bow Shock Theory, Gasdynamic or Magnetohydrodynamic, Better Explains CME Stand-off Distance Ratios from LASCO-C2 Observations ?

NASA Astrophysics Data System (ADS)

Lee, Jae-Ok; Moon, Y.-J.; Lee, Jin-Yi; Kim, R.-S.; Cho, K.-S.

2017-03-01

It is generally believed that fast coronal mass ejections (CMEs) can generate their associated shocks, which are characterized by faint structures ahead of CMEs in white-light coronagraph images. In this study, we examine whether the observational stand-off distance ratio, defined as the CME stand-off distance divided by its radius, can be explained by bow shock theories. Of 535 SOHO/LASCO CMEs (from 1996 to 2015) with speeds greater than 1000 km s-1 and angular widths wider than 60°, we select 18 limb CMEs with the following conditions: (1) their Alfvénic Mach numbers are greater than one under Mann’s magnetic field and Saito’s density distributions; and (2) the shock structures ahead of the CMEs are well identified. We determine observational CME stand-off distance ratios by using brightness profiles from LASCO-C2 observations. We compare our estimates with theoretical stand-off distance ratios from gasdynamic (GD) and magnetohydrodynamic (MHD) theories. The main results are as follows. Under the GD theory, 39% (7/18) of the CMEs are explained in the acceptable ranges of adiabatic gamma (γ) and CME geometry. Under the MHD theory, all the events are well explained when we consider quasi-parallel MHD shocks with γ = 5/3. When we use polarized brightness (pB) measurements for coronal density distributions, we also find similar results: 8% (1/12) under GD theory and 100% (12/12) under MHD theory. Our results demonstrate that the bow shock relationships based on MHD theory are more suitable than those based on GD theory for analyzing CME-driven shock signatures.

Which Bow Shock Theory, Gasdynamic or Magnetohydrodynamic, Better Explains CME Stand-off Distance Ratios from LASCO-C2 Observations ?

DOE Office of Scientific and Technical Information (OSTI.GOV)

Lee, Jae-Ok; Moon, Y.-J.; Lee, Jin-Yi

It is generally believed that fast coronal mass ejections (CMEs) can generate their associated shocks, which are characterized by faint structures ahead of CMEs in white-light coronagraph images. In this study, we examine whether the observational stand-off distance ratio, defined as the CME stand-off distance divided by its radius, can be explained by bow shock theories. Of 535 SOHO /LASCO CMEs (from 1996 to 2015) with speeds greater than 1000 km s{sup −1} and angular widths wider than 60°, we select 18 limb CMEs with the following conditions: (1) their Alfvénic Mach numbers are greater than one under Mann’s magneticmore » field and Saito’s density distributions; and (2) the shock structures ahead of the CMEs are well identified. We determine observational CME stand-off distance ratios by using brightness profiles from LASCO-C2 observations. We compare our estimates with theoretical stand-off distance ratios from gasdynamic (GD) and magnetohydrodynamic (MHD) theories. The main results are as follows. Under the GD theory, 39% (7/18) of the CMEs are explained in the acceptable ranges of adiabatic gamma ( γ ) and CME geometry. Under the MHD theory, all the events are well explained when we consider quasi-parallel MHD shocks with γ = 5/3. When we use polarized brightness (pB) measurements for coronal density distributions, we also find similar results: 8% (1/12) under GD theory and 100% (12/12) under MHD theory. Our results demonstrate that the bow shock relationships based on MHD theory are more suitable than those based on GD theory for analyzing CME-driven shock signatures.« less

PREDICTION OF GEOMAGNETIC STORM STRENGTH FROM INNER HELIOSPHERIC IN SITU OBSERVATIONS

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kubicka, M.; Möstl, C.; Amerstorfer, T.

2016-12-20

Prediction of the effects of coronal mass ejections (CMEs) on Earth strongly depends on knowledge of the interplanetary magnetic field southward component, B{sub z}. Predicting the strength and duration of B{sub z} inside a CME with sufficient accuracy is currently impossible, forming the so-called B{sub z} problem. Here, we provide a proof-of-concept of a new method for predicting the CME arrival time, speed, B{sub z}, and resulting disturbance storm time ( Dst ) index on Earth based only on magnetic field data, measured in situ in the inner heliosphere (<1 au). On 2012 June 12–16, three approximately Earthward-directed and interactingmore » CMEs were observed by the Solar Terrestrial Relations Observatory imagers and Venus Express (VEX) in situ at 0.72 au, 6° away from the Sun–Earth line. The CME kinematics are calculated using the drag-based and WSA–Enlil models, constrained by the arrival time at VEX , resulting in the CME arrival time and speed on Earth. The CME magnetic field strength is scaled with a power law from VEX to Wind . Our investigation shows promising results for the Dst forecast (predicted: −96 and −114 nT (from 2 Dst models); observed: −71 nT), for the arrival speed (predicted: 531 ± 23 km s{sup −1}; observed: 488 ± 30 km s{sup −1}), and for the timing (6 ± 1 hr after the actual arrival time). The prediction lead time is 21 hr. The method may be applied to vector magnetic field data from a spacecraft at an artificial Lagrange point between the Sun and Earth or to data taken by any spacecraft temporarily crossing the Sun–Earth line.« less

Multiple Views

NASA Image and Video Library

2017-12-08

This CME image from Oct. 7, 2012, captured by two instruments on STEREO, shows the eruption from its base out into space. The base of the CME near the sun is seen in extreme ultraviolet light emitted directly from the solar material; the growing loop is seen in visible light. Credit: NASA/STEREO CME WEEK: What To See in CME Images Two main types of explosions occur on the sun: solar flares and coronal mass ejections. Unlike the energy and x-rays produced in a solar flare – which can reach Earth at the speed of light in eight minutes – coronal mass ejections are giant, expanding clouds of solar material that take one to three days to reach Earth. Once at Earth, these ejections, also called CMEs, can impact satellites in space or interfere with radio communications. During CME WEEK from Sept. 22 to 26, 2014, we explore different aspects of these giant eruptions that surge out from the star we live with. When a coronal mass ejection blasts off the sun, scientists rely on instruments called coronagraphs to track their progress. Coronagraphs block out the bright light of the sun, so that the much fainter material in the solar atmosphere -- including CMEs -- can be seen in the surrounding space. CMEs appear in these images as expanding shells of material from the sun's atmosphere -- sometimes a core of colder, solar material (called a filament) from near the sun's surface moves in the center. But mapping out such three-dimensional components from a two-dimensional image isn't easy. Watch the slideshow to find out how scientists interpret what they see in CME pictures. The images in the slideshow are from the three sets of coronagraphs NASA currently has in space. One is on the joint European Space Agency and NASA Solar and Heliospheric Observatory, or SOHO. SOHO launched in 1995, and sits between Earth and the sun about a million miles away from Earth. The other two coronagraphs are on the two spacecraft of the NASA Solar Terrestrial Relations Observatory, or STEREO, mission, which launched in 2006. The two STEREO spacecraft are both currently viewing the far side of the sun. Together these instruments help scientists create a three-dimensional model of any CME as its journey unfolds through interplanetary space. Such information can show why a given characteristic of a CME close to the sun might lead to a given effect near Earth, or any other planet in the solar system...NASA image use policy. NASA Goddard Space Flight Center enables NASA’s mission through four scientific endeavors: Earth Science, Heliophysics, Solar System Exploration, and Astrophysics. Goddard plays a leading role in NASA’s accomplishments by contributing compelling scientific knowledge to advance the Agency’s mission. Follow us on Twitter Like us on Facebook Find us on Instagram

Detection of Coronal Mass Ejections Using Multiple Features and Space-Time Continuity

NASA Astrophysics Data System (ADS)

Zhang, Ling; Yin, Jian-qin; Lin, Jia-ben; Feng, Zhi-quan; Zhou, Jin

2017-07-01

Coronal Mass Ejections (CMEs) release tremendous amounts of energy in the solar system, which has an impact on satellites, power facilities and wireless transmission. To effectively detect a CME in Large Angle Spectrometric Coronagraph (LASCO) C2 images, we propose a novel algorithm to locate the suspected CME regions, using the Extreme Learning Machine (ELM) method and taking into account the features of the grayscale and the texture. Furthermore, space-time continuity is used in the detection algorithm to exclude the false CME regions. The algorithm includes three steps: i) define the feature vector which contains textural and grayscale features of a running difference image; ii) design the detection algorithm based on the ELM method according to the feature vector; iii) improve the detection accuracy rate by using the decision rule of the space-time continuum. Experimental results show the efficiency and the superiority of the proposed algorithm in the detection of CMEs compared with other traditional methods. In addition, our algorithm is insensitive to most noise.

Effect on the Lunar Exosphere of a CME Passage

NASA Technical Reports Server (NTRS)

Killen, Rosemary M.; Hurley, Dana M.; Farrell, William M.; Sarantos, Menelaos

2011-01-01

It has long been recognized that solar wind bombardment onto exposed surfaces in the solar system will produce an energetic component to the exospheres about those bodies. Laboratory experiments have shown that the sputter yield can be noticeably increased in the case of a good insulating surface. It is now known that the solar wind composition is highly dependent on the origin of the particular plasma. Using the measured composition of the slow wind, fast wind, solar energetic particle (SEP) population, and coronal mass ejection (CME), broken down into its various components, we have estimated the total sputter yield for each type of solar wind. The heavy ion component, especially the He++ component, greatly enhances the total sputter yield during times when the heavy ion population is enhanced, most notably during a coronal mass ejection. To simulate the effect on the lunar exosphere of a CME passage past the Moon, we ran a Monte Carlo code for the species Na, K, Mg and Ca.

New Evidence that CMEs are Self-Propelled Magnetic Bubbles

NASA Technical Reports Server (NTRS)

Moore, Ronald L.; Sterling, Alphonse C.; Seuss, Steven T.

2007-01-01

We briefly describe the "standard model" for the production of coronal mass ejections (CMEs), and our view of how it works. We then summarize pertinent recent results that we have found from SOHO observations of CMEs and the flares at the sources of these magnetic explosions. These results support our interpretation of the standard model: a CME is basically a self-propelled magnetic bubble, a low-beta plasmoitl, that (1) is built and unleashed by the tether-cutting reconnection that builds and heats the coronal flare arcade, (2) can explode from a flare site that is far from centered under the full-blown CME in the outer corona, and (3) drives itself out into the solar wind by pushing on the surrounding coronal magnetic field.

Combined Images

NASA Image and Video Library

2017-12-08

Four different instruments on SOHO show a large CME on Nov. 6, 1997. The sun is at the center, with three coronagraph images of different sizes around it. The streaks of white light are from protons hitting the SOHO cameras producing a snowy effect typical of a significant flare. ..Credit: NASA/SOHO..---..CME WEEK: What To See in CME Images Two main types of explosions occur on the sun: solar flares and coronal mass ejections. Unlike the energy and x-rays produced in a solar flare – which can reach Earth at the speed of light in eight minutes – coronal mass ejections are giant, expanding clouds of solar material that take one to three days to reach Earth. Once at Earth, these ejections, also called CMEs, can impact satellites in space or interfere with radio communications. During CME WEEK from Sept. 22 to 26, 2014, we explore different aspects of these giant eruptions that surge out from the star we live with. When a coronal mass ejection blasts off the sun, scientists rely on instruments called coronagraphs to track their progress. Coronagraphs block out the bright light of the sun, so that the much fainter material in the solar atmosphere -- including CMEs -- can be seen in the surrounding space. CMEs appear in these images as expanding shells of material from the sun's atmosphere -- sometimes a core of colder, solar material (called a filament) from near the sun's surface moves in the center. But mapping out such three-dimensional components from a two-dimensional image isn't easy. Watch the slideshow to find out how scientists interpret what they see in CME pictures. The images in the slideshow are from the three sets of coronagraphs NASA currently has in space. One is on the joint European Space Agency and NASA Solar and Heliospheric Observatory, or SOHO. SOHO launched in 1995, and sits between Earth and the sun about a million miles away from Earth. The other two coronagraphs are on the two spacecraft of the NASA Solar Terrestrial Relations Observatory, or STEREO, mission, which launched in 2006. The two STEREO spacecraft are both currently viewing the far side of the sun. Together these instruments help scientists create a three-dimensional model of any CME as its journey unfolds through interplanetary space. Such information can show why a given characteristic of a CME close to the sun might lead to a given effect near Earth, or any other planet in the solar system...NASA image use policy. NASA Goddard Space Flight Center enables NASA’s mission through four scientific endeavors: Earth Science, Heliophysics, Solar System Exploration, and Astrophysics. Goddard plays a leading role in NASA’s accomplishments by contributing compelling scientific knowledge to advance the Agency’s mission. Follow us on Twitter Like us on Facebook Find us on Instagram

Photospheric magnetic field of an eroded-by-solar-wind coronal mass ejection

NASA Astrophysics Data System (ADS)

Palacios, J.; Cid, C.; Saiz, E.; Guerrero, A.

2017-10-01

We have investigated the case of a coronal mass ejection that was eroded by the fast wind of a coronal hole in the interplanetary medium. When a solar ejection takes place close to a coronal hole, the flux rope magnetic topology of the coronal mass ejection (CME) may become misshapen at 1 AU as a result of the interaction. Detailed analysis of this event reveals erosion of the interplanetary coronal mass ejection (ICME) magnetic field. In this communication, we study the photospheric magnetic roots of the coronal hole and the coronal mass ejection area with HMI/SDO magnetograms to define their magnetic characteristics.

Conditions for the existence of Kelvin-Helmholtz instability in a CME

NASA Astrophysics Data System (ADS)

Jatenco-Pereira, Vera; Páez, Andrés; Falceta-Gonçalves, Diego; Opher, Merav

2015-08-01

The presence of Kelvin-Helmholtz instability (KHI) in the sheaths of the Coronal Mass Ejection (CME) has motivated several analysis and simulations to test their existence. In the present work we assume the existence of the KHI and propose a method to identify the regions where it is possible the development of KHI for a CME propagating in a fast and slow solar wind. We build functions for the velocities, densities and magnetic fields for two different zones of interaction between the solar wind and a CME. Based on the theory of magnetic KHI proposed by Chandrasekhar (1961) and we found conditions for the existence of KHI in the CME sheaths. Using this method it is possible to determine the range of parameters, in particular CME magnetic fields in which the KHI could exist. We conclude that KHI may exist in the two CME flanks and it is perceived that the zone with boundaries with the slow solar wind is more appropriated for the formation of the KHI.

CMEs in the Heliosphere: I. A Statistical Analysis of the Observational Properties of CMEs Detected in the Heliosphere from 2007 to 2017 by STEREO/HI-1

NASA Astrophysics Data System (ADS)

Harrison, R. A.; Davies, J. A.; Barnes, D.; Byrne, J. P.; Perry, C. H.; Bothmer, V.; Eastwood, J. P.; Gallagher, P. T.; Kilpua, E. K. J.; Möstl, C.; Rodriguez, L.; Rouillard, A. P.; Odstrčil, D.

2018-05-01

We present a statistical analysis of coronal mass ejections (CMEs) imaged by the Heliospheric Imager (HI) instruments on board NASA's twin-spacecraft STEREO mission between April 2007 and August 2017 for STEREO-A and between April 2007 and September 2014 for STEREO-B. The analysis exploits a catalogue that was generated within the FP7 HELCATS project. Here, we focus on the observational characteristics of CMEs imaged in the heliosphere by the inner (HI-1) cameras, while following papers will present analyses of CME propagation through the entire HI fields of view. More specifically, in this paper we present distributions of the basic observational parameters - namely occurrence frequency, central position angle (PA) and PA span - derived from nearly 2000 detections of CMEs in the heliosphere by HI-1 on STEREO-A or STEREO-B from the minimum between Solar Cycles 23 and 24 to the maximum of Cycle 24; STEREO-A analysis includes a further 158 CME detections from the descending phase of Cycle 24, by which time communication with STEREO-B had been lost. We compare heliospheric CME characteristics with properties of CMEs observed at coronal altitudes, and with sunspot number. As expected, heliospheric CME rates correlate with sunspot number, and are not inconsistent with coronal rates once instrumental factors/differences in cataloguing philosophy are considered. As well as being more abundant, heliospheric CMEs, like their coronal counterparts, tend to be wider during solar maximum. Our results confirm previous coronagraph analyses suggesting that CME launch sites do not simply migrate to higher latitudes with increasing solar activity. At solar minimum, CMEs tend to be launched from equatorial latitudes, while at maximum, CMEs appear to be launched over a much wider latitude range; this has implications for understanding the CME/solar source association. Our analysis provides some supporting evidence for the systematic dragging of CMEs to lower latitude as they propagate outwards.

Reconstructing the Morphology of an Evolving Coronal Mass Ejection

DTIC Science & Technology

2009-01-01

694, 707 Wood, B. E., Howard, R. A ., Thernisien, A ., Plunkett, S. P., & Socker, D. G. 2009b, Sol. Phys., 259, 163 Wood, B. E., Karovska , M., Chen, J...Reconstructing the Morphology of an Evolving Coronal Mass Ejection B. E. Wood, R. A . Howard, D. G. Socker Naval Research Laboratory, Space Science...mission, we empirically reconstruct the time-dependent three-dimensional morphology of a coronal mass ejection (CME) from 2008 June 1, which exhibits

Constraining Stellar Coronal Mass Ejections through Multi-wavelength Analysis of the Active M Dwarf EQ Peg

NASA Astrophysics Data System (ADS)

Crosley, M. K.; Osten, R. A.

2018-03-01

Stellar coronal mass ejections remain experimentally unconstrained, unlike their stellar flare counterparts, which are observed ubiquitously across the electromagnetic spectrum. Low-frequency radio bursts in the form of a type II burst offer the best means of identifying and constraining the rate and properties of stellar CMEs. CME properties can be further improved through the use of proposed solar-stellar scaling relations and multi-wavelength observations of CMEs through the use of type II bursts and the associated flares expected to occur alongside them. We report on 20 hr of observation of the nearby, magnetically active, and well-characterized M dwarf star EQ Peg. The observations are simultaneously observed with the Jansky Very Large Array at their P-band (230–470 MHz) and at the Apache Point observatory in the SDSS u‧ filter (λ = 3557 Å). Dynamic spectra of the P-band data, constructed to search for signals in the frequency-time domains, did not reveal evidence of drifting radio bursts that could be ascribed to type II bursts. Given the sensitivity of our observations, we are able to place limits on the brightness temperature and source size of any bursts that may have occurred. Using solar scaling rations on four observed stellar flares, we predict CME parameters. Given the constraints on coronal density and photospheric field strength, our models suggest that the observed flares would have been insufficient to produce detectable type II bursts at our observed frequencies. We consider the implications of these results, and other recent findings, on stellar mass loss.

PROPAGATION AND EVOLUTION OF THE JUNE 1st 2008 CME IN THE INTERPLANETARY MEDIUM

NASA Astrophysics Data System (ADS)

Nieves-Chinchilla, T.; Lamb, D. A.; Davila, J. M.; Vinas, A. F.; Moestl, C.; Hidalgo, M. A.; Farrugia, C. J.; Malandraki, O.; Dresing, N.; Gómez-Herrero, R.

2009-12-01

In this work we present a study of the coronal mass ejection (CME) of June 1st of 2008 in the interplanetary medium. This event has been extensively studied by others because of its favorable geometry and the possible consequences of its peculiar initiation for space weather forecasting. We show an analysis of the evolution of the CME in the interplanetary medium in order to shed some light on the propagation mechanism of the ICME. We have determined the typical shock associated characteristics of the ICME in order to understand the propagation properties. Using two different non force-free models of the magnetic cloud allows us to incorporate expansion of the cloud. We use in-situ measurements from STEREO B/IMPACT to characterize the ICME. In addition, we use images from STEREO A/SECCHI-HI to analyze the propagation and visual evolution of the associated flux rope in the interplanetary medium. We compare and contrast these observations with the results of the analytical models.

Anticipated Electrical Environment at Phobos: Nominal and Solar Storm Conditions

NASA Technical Reports Server (NTRS)

Farrell, W. M.; Halekas, J. S.; Fatemi, S.; Poppe, A. R.; Hartzell, C.; Marshall, J. R.; Stubbs, T. J.; Zimmerman, M. I.; Zheng, Y.

2017-01-01

A passing coronal mass ejection (CME) will manifest a different response at an airless body compared to a magnetized planet. Specifically,because the regolith-rich surfaces of airless bodies are directly exposed to the variations in the plasma flow, the surfaces are found to undergo anomalous surface charging during the passing of CME fast plasma events. In this study, we model the surface charging expected at Phobos for nominal solar wind conditions and also those associated with disturbed solar wind conditions during the passage of a CME similar to that observed by MAVEN at Mars in early March 2015. We use an ambipolar diffusion model to examine the development of the trailing wake void in the plasma flow behind Phobos and the formation of mini-wakes within obstruction regions like Stickney Crater. We also consider the roving of an astronaut in Stickney Crater for Phobos positioned near 10 hours Local Time relative to Mars. We examine the plasma dissipation of the collected astronaut charge from contact electrification with the regolith.

Solar wind composition from sector boundary crossings and coronal mass ejections

NASA Technical Reports Server (NTRS)

Ogilvie, K. W.; Coplan, M. A.; Geiss, J.

1992-01-01

Using the Ion Composition Instrument (ICI) on board the ISEE-3/ICE spacecraft, average abundances of He-4, He-3, O, Ne, Si, and Fe have been determined over extended periods. In this paper the abundances of He-4, O, Ne, Si, and Mg obtained by the ICI in the region of sector boundary crossings (SBCs), magnetic clouds and bidirectional streaming events (BDSs) are compared with the average abundances. Both magnetic clouds and BDSs are associated with coronal mass ejections (CMEs). No variation of abundance is seen to occur at SBCs except for helium, as has already been observed. In CME-related material, the abundance of neon appears to be high and variable, in agreement with recent analysis of spectroscopic observations of active regions. We find that our observations can be correlated with the magnetic topology in the corona.

THE FORMATION AND EARLY EVOLUTION OF A CORONAL MASS EJECTION AND ITS ASSOCIATED SHOCK WAVE ON 2014 JANUARY 8

DOE Office of Scientific and Technical Information (OSTI.GOV)

Wan Linfeng; Cheng, Xin; Shi, Tong

2016-08-01

In this paper, we study the formation and early evolution of a limb coronal mass ejection (CME) and its associated shock wave that occurred on 2014 January 8. The extreme ultraviolet (EUV) images provided by the Atmospheric Imaging Assembly (AIA) on board the Solar Dynamics Observatory disclose that the CME first appears as a bubble-like structure. Subsequently, its expansion forms the CME and causes a quasi-circular EUV wave. Interestingly, both the CME and the wave front are clearly visible at all of the AIA EUV passbands. Through a detailed kinematical analysis, it is found that the expansion of the CMEmore » undergoes two phases: a first phase with a strong but transient lateral over-expansion followed by a second phase with a self-similar expansion. The temporal evolution of the expansion velocity coincides very well with the variation of the 25–50 keV hard X-ray flux of the associated flare, which indicates that magnetic reconnection most likely plays an important role in driving the expansion. Moreover, we find that, when the velocity of the CME reaches ∼600 km s{sup −1}, the EUV wave starts to evolve into a shock wave, which is evidenced by the appearance of a type II radio burst. The shock’s formation height is estimated to be ∼0.2 R {sub sun}, which is much lower than the height derived previously. Finally, we also study the thermal properties of the CME and the EUV wave. We find that the plasma in the CME leading front and the wave front has a temperature of ∼2 MK, while that in the CME core region and the flare region has a much higher temperature of ≥8 MK.« less

Studying aerodynamic drag for modeling the kinematical behavior of CMEs

NASA Astrophysics Data System (ADS)

Temmer, M.; Vrsnak, B.; Moestl, C.; Zic, T.; Veronig, A. M.; Rollett, T.

2013-12-01

With the SECCHI instrument suite aboard STEREO, coronal mass ejections (CMEs) can be observed from multiple vantage points during their entire propagation all the way from the Sun to 1 AU. The propagation behavior of CMEs in interplanetary space is mainly influenced by the ambient solar wind flow. CMEs that are faster than the ambient solar wind get decelerated, whereas slower ones are accelerated until the CME speed is finally adjusted to the solar wind speed. On a statistical basis, empirical models taking into account the drag force acting on CMEs, are able to describe the observed kinematical behaviors. For several well observed CME events we derive the kinematical evolution by combining remote sensing and in situ data. The observed kinematical behavior is compared to results from current empirical and numerical propagation models. For this we mainly use the drag based model DBM as well as the MHD model ENLIL. We aim to obtain the distance regime at which the solar wind drag force is dominating the CME propagation and quantify differences between different model results. This work has received funding from the FWF: V195-N16, and the European Commission FP7 Projects eHEROES (284461, www.eheroes.eu) and COMESEP (263252, www.comesep.eu).

Calculating Coronal Mass Ejection Magnetic Field at 1 AU Using Solar Observables

NASA Astrophysics Data System (ADS)

Chen, J.; Kunkel, V.

2013-12-01

It is well-established that most major nonrecurrent geomagnetic storms are caused by solar wind structures with long durations of strong southward (Bz < 0) interplanetary magnetic field (IMF). Such geoeffective IMF structures are associated with CME events at the Sun. Unfortunately, neither the duration nor the internal magnetic field vector of the ejecta--the key determinants of geoeffectiveness--is measurable until the observer (e.g., Earth) passes through the ejecta. In this paper, we discuss the quantitative relationships between the ejecta magnetic field at 1 AU and remotely observable solar quantities associated with the eruption of a given CME. In particular, we show that observed CME trajectories (position-time data) within, say, 1/3 AU of the Sun, contain sufficient information to allow the calculation of the ejecta magnetic field (magnitude and components) at 1 AU using the Erupting Flux Rope (EFR) model of CMEs. Furthermore, in order to accurately determine the size and arrival time of the ejecta as seen by a fixed observer at 1 AU (e.g., ACE), it is essential to accurately calculate the three-dimensional geometry of the underlying magnetic structure. Accordingly, we have extended the physics-based EFR model to include a self-consistent calculation of the transverse expansion taking into account the non-symmetric drag coupling between an expanding CME flux rope and the ambient solar wind. The dependence of the minor radius of the flux rope at 1 AU that determines the perceived size of the ejecta on solar quantities is discussed. Work supported by the NRL Base Program.

CHALLENGING SOME CONTEMPORARY VIEWS OF CORONAL MASS EJECTIONS. I. THE CASE FOR BLAST WAVES

DOE Office of Scientific and Technical Information (OSTI.GOV)

Howard, T. A.; Pizzo, V. J., E-mail: howard@boulder.swri.edu

Since the closure of the “solar flare myth” debate in the mid-1990s, a specific narrative of the nature of coronal mass ejections (CMEs) has been widely accepted by the solar physics community. This narrative describes structured magnetic flux ropes at the CME core that drive the surrounding field plasma away from the Sun. This narrative replaced the “traditional” view that CMEs were blast waves driven by solar flares. While the flux rope CME narrative is supported by a vast quantity of measurements made over five decades, it does not adequately describe every observation of what have been termed CME-related phenomena.more » In this paper we present evidence that some large-scale coronal eruptions, particularly those associated with EIT waves, exhibit characteristics that are more consistent with a blast wave originating from a localized region (such as a flare site) rather than a large-scale structure driven by an intrinsic flux rope. We present detailed examples of CMEs that are suspected blast waves and flux ropes, and show that of our small sample of 22 EIT-wave-related CMEs, 91% involve a blast wave as at least part of the eruption, and 50% are probably blast waves exclusively. We conclude with a description of possible signatures to look for in determining the difference between the two types of CMEs and with a discussion on modeling efforts to explore this possibility.« less

Relation Between Type II Bursts and CMEs Inferred from STEREO Observations

NASA Technical Reports Server (NTRS)

Gopalswamy, N.; Thompson, W.; Davila, J.; Kaiser, M. L.; Yashiro, S.; Maekelae, P.; Michalek, G.; Bougeret, J.-L.; Hoawrd, R. A.

2010-01-01

The inner coronagraph (COR1) of the Solar Terrestrial Relations Observatory (STEREO) mission has made it possible to observe coronal mass ejections (CMEs) a in the spatial domain overlapping with that of the metric type II radio bursts. The type II bursts were associated with generally weak flares (mostly B and C class soft X-ray flares), but the CMEs were quite energetic. Using CME data for a set of type II bursts during the declining phase of solar cycle 23, we determine the CME height when the type II bursts start, thus giving an estimate of the heliocentric distance at which CME-driven shocks form. This distance has been determined to be approximately 1.5Rs (solar radii), which coincides with the distance at which the Alfv?n speed profile has a minimum value. We also use type II radio observations from STEREO/WAVES and Wind/WAVES observations to show that CMEs with moderate speed drive either weak shocks or no shock at all when they attain a height where the Alfv?n speed peaks (?3Rs ? 4Rs). Thus the shocks seem to be most efficient in accelerating electrons in the heliocentric distance range of 1.5Rs to 4Rs. By combining the radial variation of the CME speed in the inner corona (CME speed increase) and interplanetary medium (speed decrease) we were able to correctly account for the deviations from the universal drift-rate spectrum of type II bursts, thus confirming the close physical connection between type II bursts and CMEs. The average height (approximately 1.5 Rs) of STEREO CMEs at the time of type II bursts is smaller than that (2.2 Rs) obtained for SOHO (Solar and Heliospheric Observatory) CMEs. We suggest that this may indicate, at least partly, the density reduction in the corona between the maximum and declining phases, so a given plasma level occurs closer to the Sun in the latter phase. In two cases, there was a diffuse shock-like feature ahead of the main body of the CME, indicating a standoff distance of 1Rs - 2Rs by the time the CME left the LASCO field of view.

Ultraviolet Properties of Halo Coronal Mass Ejections: Doppler Shifts, Angles, Shocks, and Bulk Morphology

NASA Astrophysics Data System (ADS)

Ciaravella, A.; Raymond, J. C.; Kahler, S. W.

2006-11-01

We present UV spectral information for 22 halo or partial halo CMEs observed by UVCS. The CME fronts show broad line profiles, while the line intensities are comparable to the background corona. The Doppler shifts of the front material are generally small, showing that the motion of gas in the fronts is mostly transverse to the line of sight. This indicates that, at least in halo CMEs, the fronts generally correspond to coronal plasma swept up by a shock or compression wave, rather than plasma carried outward by magnetic loops. This favors an ice cream cone (or a spherical shell) model, as opposed to an expanding arcade of loops. We use the line widths to discriminate between shock heating and bulk expansion. Of 14 cases where we detected the CME front, the line broadening in 7 cases can be attributed to shock heating, while in 3 cases it is the line-of-sight component of the CME expansion. For the CME cores we determine the angles between the motion and the plane of the sky, along with the actual heliocentric distances, in order to provide quantitative estimates of projection effects.

Origin and Structures of Solar Eruptions I: Magnetic Flux Rope

NASA Astrophysics Data System (ADS)

Cheng, Xin; Guo, Yang; Ding, MingDe

2017-08-01

Coronal mass ejections (CMEs) and solar flares are the large-scale and most energetic eruptive phenomena in our solar system and able to release a large quantity of plasma and magnetic flux from the solar atmosphere into the solar wind. When these high-speed magnetized plasmas along with the energetic particles arrive at the Earth, they may interact with the magnetosphere and ionosphere, and seriously affect the safety of human high-tech activities in outer space. The travel time of a CME to 1 AU is about 1-3 days, while energetic particles from the eruptions arrive even earlier. An efficient forecast of these phenomena therefore requires a clear detection of CMEs/flares at the stage as early as possible. To estimate the possibility of an eruption leading to a CME/flare, we need to elucidate some fundamental but elusive processes including in particular the origin and structures of CMEs/flares. Understanding these processes can not only improve the prediction of the occurrence of CMEs/flares and their effects on geospace and the heliosphere but also help understand the mass ejections and flares on other solar-type stars. The main purpose of this review is to address the origin and early structures of CMEs/flares, from multi-wavelength observational perspective. First of all, we start with the ongoing debate of whether the pre-eruptive configuration, i.e., a helical magnetic flux rope (MFR), of CMEs/flares exists before the eruption and then emphatically introduce observational manifestations of the MFR. Secondly, we elaborate on the possible formation mechanisms of the MFR through distinct ways. Thirdly, we discuss the initiation of the MFR and associated dynamics during its evolution toward the CME/flare. Finally, we come to some conclusions and put forward some prospects in the future.

Correlation Analyses Between the Characteristic Times of Gradual Solar Energetic Particle Events and the Properties of Associated Coronal Mass Ejections

NASA Astrophysics Data System (ADS)

Pan, Z. H.; Wang, C. B.; Wang, Yuming; Xue, X. H.

2011-06-01

It is generally believed that gradual solar energetic particles (SEPs) are accelerated by shocks associated with coronal mass ejections (CMEs). Using an ice-cream cone model, the radial speed and angular width of 95 CMEs associated with SEP events during 1998 - 2002 are calculated from SOHO/LASCO observations. Then, we investigate the relationships between the kinematic properties of these CMEs and the characteristic times of the intensity-time profile of their accompanied SEP events observed at 1 AU. These characteristic times of SEP are i) the onset time from the accompanying CME eruption at the Sun to the SEP arrival at 1 AU, ii) the rise time from the SEP onset to the time when the SEP intensity is one-half of peak intensity, and iii) the duration over which the SEP intensity is within a factor of two of the peak intensity. It is found that the onset time has neither significant correlation with the radial speed nor with the angular width of the accompanying CME. For events that are poorly connected to the Earth, the SEP rise time and duration have no significant correlation with the radial speed and angular width of the associated CMEs. However, for events that are magnetically well connected to the Earth, the SEP rise time and duration have significantly positive correlations with the radial speed and angular width of the associated CMEs. This indicates that a CME event with wider angular width and higher speed may more easily drive a strong and wide shock near to the Earth-connected interplanetary magnetic field lines, may trap and accelerate particles for a longer time, and may lead to longer rise time and duration of the ensuing SEP event.

An ice-cream cone model for coronal mass ejections

NASA Astrophysics Data System (ADS)

Xue, X. H.; Wang, C. B.; Dou, X. K.

2005-08-01

In this study, we use an ice-cream cone model to analyze the geometrical and kinematical properties of the coronal mass ejections (CMEs). Assuming that in the early phase CMEs propagate with near-constant speed and angular width, some useful properties of CMEs, namely the radial speed (v), the angular width (α), and the location at the heliosphere, can be obtained considering the geometrical shapes of a CME as an ice-cream cone. This model is improved by (1) using an ice-cream cone to show the near real configuration of a CME, (2) determining the radial speed via fitting the projected speeds calculated from the height-time relation in different azimuthal angles, (3) not only applying to halo CMEs but also applying to nonhalo CMEs.

NASA's IRIS Observed a Gigantic Eruption on the Sun!

NASA Image and Video Library

2014-05-30

A coronal mass ejection, or CME, surged off the side of the sun on May 9, 2014, and NASA's newest solar observatory caught it in extraordinary detail. This was the first CME observed by the Interface Region Imaging Spectrograph, or IRIS, which launched in June 2013 to peer into the lowest levels of the sun's atmosphere with better resolution than ever before. Watch the movie to see how a curtain of solar material erupts outward at speeds of 1.5 million miles per hour. Read more: 1.usa.gov/1kp7O4F Credit: NASA's Goddard Space Flight Center NASA image use policy. NASA Goddard Space Flight Center enables NASA’s mission through four scientific endeavors: Earth Science, Heliophysics, Solar System Exploration, and Astrophysics. Goddard plays a leading role in NASA’s accomplishments by contributing compelling scientific knowledge to advance the Agency’s mission. Follow us on Twitter Like us on Facebook Find us on Instagram

A New Tool for CME Arrival Time Prediction using Machine Learning Algorithms: CAT-PUMA

NASA Astrophysics Data System (ADS)

Liu, Jiajia; Ye, Yudong; Shen, Chenglong; Wang, Yuming; Erdélyi, Robert

2018-03-01

Coronal mass ejections (CMEs) are arguably the most violent eruptions in the solar system. CMEs can cause severe disturbances in interplanetary space and can even affect human activities in many aspects, causing damage to infrastructure and loss of revenue. Fast and accurate prediction of CME arrival time is vital to minimize the disruption that CMEs may cause when interacting with geospace. In this paper, we propose a new approach for partial-/full halo CME Arrival Time Prediction Using Machine learning Algorithms (CAT-PUMA). Via detailed analysis of the CME features and solar-wind parameters, we build a prediction engine taking advantage of 182 previously observed geo-effective partial-/full halo CMEs and using algorithms of the Support Vector Machine. We demonstrate that CAT-PUMA is accurate and fast. In particular, predictions made after applying CAT-PUMA to a test set unknown to the engine show a mean absolute prediction error of ∼5.9 hr within the CME arrival time, with 54% of the predictions having absolute errors less than 5.9 hr. Comparisons with other models reveal that CAT-PUMA has a more accurate prediction for 77% of the events investigated that can be carried out very quickly, i.e., within minutes of providing the necessary input parameters of a CME. A practical guide containing the CAT-PUMA engine and the source code of two examples are available in the Appendix, allowing the community to perform their own applications for prediction using CAT-PUMA.

Global MHD modeling of an ICME focused on the physics involved in an ICME interacting with a solar wind

NASA Astrophysics Data System (ADS)

An, Jun-Mo; Magara, Tetsuya; Inoue, Satoshi; Hayashi, Keiji; Tanaka, Takashi

2015-04-01

We developed a three-dimensional (3D) magnetohydrodynamic (MHD) code to investigate the structure of a solar wind, the properties of a coronal mass ejection (CME) and the interaction between them. This MHD code is based on the finite volume method incorporating total variation diminishing (TVD) scheme with an unstructured grid system. In particular, this grid system can avoid the singularity at the north and south poles and relax tight CFL conditions around the poles, both of which would arise in a spherical coordinate system (Tanaka 1994). In this model, we first apply an MHD tomographic method (Hayashi et al. 2003) to interplanetary scintillation (IPS) observational data and derive a solar wind from the physical values obtained at 50 solar radii away from the Sun. By comparing the properties of this solar wind to observational data obtained near the Earth orbit, we confirmed that our model captures the velocity, temperature and density profiles of a solar wind near the Earth orbit. We then insert a spheromak-type CME (Kataoka et al. 2009) into the solar wind to reproduce an actual CME event occurred on 29 September 2013. This has been done by introducing a time-dependent boundary condition to the inner boundary of our simulation domain (50rs < r < 300rs). On the basis of a comparison between the properties of a simulated CME and observations near the Earth, we discuss the physics involved in an ICME interacting with a solar wind.

On Flare-CME Characteristics from Sun to Earth Combining Remote-Sensing Image Data with In Situ Measurements Supported by Modeling

NASA Astrophysics Data System (ADS)

Temmer, Manuela; Thalmann, Julia K.; Dissauer, Karin; Veronig, Astrid M.; Tschernitz, Johannes; Hinterreiter, Jürgen; Rodriguez, Luciano

2017-07-01

We analyze the well-observed flare and coronal mass ejection (CME) from 1 October 2011 (SOL2011-10-01T09:18) covering the complete chain of effects - from Sun to Earth - to better understand the dynamic evolution of the CME and its embedded magnetic field. We study in detail the solar surface and atmosphere associated with the flare and CME using the Solar Dynamics Observatory (SDO) and ground-based instruments. We also track the CME signature off-limb with combined extreme ultraviolet (EUV) and white-light data from the Solar Terrestrial Relations Observatory (STEREO). By applying the graduated cylindrical shell (GCS) reconstruction method and total mass to stereoscopic STEREO-SOHO ( Solar and Heliospheric Observatory) coronagraph data, we track the temporal and spatial evolution of the CME in the interplanetary space and derive its geometry and 3D mass. We combine the GCS and Lundquist model results to derive the axial flux and helicity of the magnetic cloud (MC) from in situ measurements from Wind. This is compared to nonlinear force-free (NLFF) model results, as well as to the reconnected magnetic flux derived from the flare ribbons (flare reconnection flux) and the magnetic flux encompassed by the associated dimming (dimming flux). We find that magnetic reconnection processes were already ongoing before the start of the impulsive flare phase, adding magnetic flux to the flux rope before its final eruption. The dimming flux increases by more than 25% after the end of the flare, indicating that magnetic flux is still added to the flux rope after eruption. Hence, the derived flare reconnection flux is most probably a lower limit for estimating the magnetic flux within the flux rope. We find that the magnetic helicity and axial magnetic flux are lower in the interplanetary space by ˜ 50% and 75%, respectively, possibly indicating an erosion process. A CME mass increase of 10% is observed over a range of {˜} 4 - 20 R_{⊙}. The temporal evolution of the CME-associated core-dimming regions supports the scenario that fast outflows might supply additional mass to the rear part of the CME.

The first in situ observation of torsional Alfvén waves during the interaction of large-scale magnetic clouds

NASA Astrophysics Data System (ADS)

Raghav, Anil N.; Kule, Ankita

2018-05-01

The large-scale magnetic cloud such as coronal mass ejections (CMEs) is the fundamental driver of the space weather. The interaction of the multiple-CMEs in interplanetary space affects their dynamic evolution and geo-effectiveness. The complex and merged multiple magnetic clouds appear as the in situ signature of the interacting CMEs. The Alfvén waves are speculated to be one of the major possible energy exchange/dissipation mechanism during the interaction. However, no such observational evidence has been found in the literature. The case studies of CME-CME collision events suggest that the magnetic and thermal energy of the CME is converted into the kinetic energy. Moreover, magnetic reconnection process is justified to be responsible for merging of multiple magnetic clouds. Here, we present unambiguous evidence of sunward torsional Alfvén waves in the interacting region after the super-elastic collision of multiple CMEs. The Walén relation is used to confirm the presence of Alfvén waves in the interacting region of multiple CMEs/magnetic clouds. We conclude that Alfvén waves and magnetic reconnection are the possible energy exchange/dissipation mechanisms during large-scale magnetic clouds collisions. This study has significant implications not only in CME-magnetosphere interactions but also in the interstellar medium where interactions of large-scale magnetic clouds are possible.

Direct Evidence of an Eruptive, Filament-hosting Magnetic Flux Rope Leading to a Fast Solar Coronal Mass Ejection

NASA Astrophysics Data System (ADS)

Chen, Bin; Bastian, T. S.; Gary, D. E.

2014-10-01

Magnetic flux ropes (MFRs) are believed to be at the heart of solar coronal mass ejections (CMEs). A well-known example is the prominence cavity in the low corona that sometimes makes up a three-part white-light (WL) CME upon its eruption. Such a system, which is usually observed in quiet-Sun regions, has long been suggested to be the manifestation of an MFR with relatively cool filament material collecting near its bottom. However, observational evidence of eruptive, filament-hosting MFR systems has been elusive for those originating in active regions. By utilizing multi-passband extreme-ultraviolet (EUV) observations from Solar Dynamics Observatory/Atmospheric Imaging Assembly, we present direct evidence of an eruptive MFR in the low corona that exhibits a hot envelope and a cooler core; the latter is likely the upper part of a filament that undergoes a partial eruption, which is later observed in the upper corona as the coiled kernel of a fast, WL CME. This MFR-like structure exists more than 1 hr prior to its eruption, and displays successive stages of dynamical evolution, in which both ideal and non-ideal physical processes may be involved. The timing of the MFR kinematics is found to be well correlated with the energy release of the associated long-duration C1.9 flare. We suggest that the long-duration flare is the result of prolonged energy release associated with the vertical current sheet induced by the erupting MFR.

Influence of Sun and Other Cosmic Factors on Environment of the Earth

DTIC Science & Technology

2010-01-07

of the secondary cosmic rays (mostly muons , electrons, neutrons and gammas) can provide highly cost-effective information on the key characteristics...Coronal mass ejection (CME) from the Sun the impact on the Galactic Cosmic rays (GCR) will be observed. Particle detector is vital for measuring the...modulation effects the sun poses on the ambient population of the Galactic Cosmic Rays (GCR). The known agents of these modulation effects are Solar Flares

Prospective Out-of-ecliptic White-light Imaging of Coronal Mass Ejections Traveling through the Corona and Heliosphere

NASA Astrophysics Data System (ADS)

Xiong, Ming; Davies, Jackie A.; Harrison, Richard A.; Zhou, Yufen; Feng, Xueshang; Xia, Lidong; Li, Bo; Liu, Ying D.; Hayashi, Keiji; Li, Huichao; Yang, Liping

2018-01-01

The in-flight performance of the Coriolis/SMEI and STEREO/HI instruments substantiates the high-technology readiness level of white-light (WL) imaging of coronal mass ejections (CMEs) in the inner heliosphere. The WL intensity of a propagating CME is jointly determined by its evolving mass distribution and the fixed Thomson-scattering geometry. From their in-ecliptic viewpoints, SMEI and HI, the only heliospheric imagers that have been flown to date, integrate the longitudinal dimension of CMEs. In this paper, using forward magnetohydrodynamic modeling, we synthesize the WL radiance pattern of a typical halo CME viewed from an out-of-ecliptic (OOE) vantage point. The major anatomical elements of the CME identified in WL imagery are a leading sheath and a trailing ejecta; the ejecta-driven sheath is the brightest feature of the CME. The sheath, a three-dimensional (3D) dome-like density structure, occupies a wide angular extent ahead of the ejecta itself. The 2D radiance pattern of the sheath depends critically on viewpoint. For a CME modeled under solar minimum conditions, the WL radiance pattern of the sheath is generally a quasi-straight band when viewed from an in-ecliptic viewpoint and a semicircular arc from an OOE viewpoint. The dependence of the radiance pattern of the ejecta-driven sheath on viewpoint is attributed to the bimodal nature of the 3D background solar wind flow. Our forward-modeling results suggest that OOE imaging in WL radiance can enable (1) a near-ecliptic CME to be continuously tracked from its coronal initiation, (2) the longitudinal span of the CME to be readily charted, and (3) the transporting speed of the CME to be reliably determined. Additional WL polarization measurements can significantly limit the ambiguity of localizing CMEs. We assert that a panoramic OOE view in WL would be highly beneficial in revealing CME morphology and kinematics in the hitherto-unresolved longitudinal dimension and hence for monitoring the propagation and evolution of near-ecliptic CMEs for space weather operations.

Investigating the Origins of Two Extreme Solar Particle Events: Proton Source Profile and Associated Electromagnetic Emissions

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kocharov, Leon; Usoskin, Ilya; Pohjolainen, Silja

We analyze the high-energy particle emission from the Sun in two extreme solar particle events in which protons are accelerated to relativistic energies and can cause a significant signal even in the ground-based particle detectors. Analysis of a relativistic proton event is based on modeling of the particle transport and interaction, from a near-Sun source through the solar wind and the Earth’s magnetosphere and atmosphere to a detector on the ground. This allows us to deduce the time profile of the proton source at the Sun and compare it with observed electromagnetic emissions. The 1998 May 2 event is associatedmore » with a flare and a coronal mass ejection (CME), which were well observed by the Nançay Radioheliograph, thus the images of the radio sources are available. For the 2003 November 2 event, the low corona images of the CME liftoff obtained at the Mauna Loa Solar Observatory are available. Those complementary data sets are analyzed jointly with the broadband dynamic radio spectra, EUV images, and other data available for both events. We find a common scenario for both eruptions, including the flare’s dual impulsive phase, the CME-launch-associated decimetric-continuum burst, and the late, low-frequency type III radio bursts at the time of the relativistic proton injection into the interplanetary medium. The analysis supports the idea that the two considered events start with emission of relativistic protons previously accelerated during the flare and CME launch, then trapped in large-scale magnetic loops and later released by the expanding CME.« less

Tracking CMEs using data from the Solar Stormwatch project; observing deflections and other properties

NASA Astrophysics Data System (ADS)

Jones, Shannon R.; Barnard, Luke A.; Scott, Christopher J.; Owens, Mathew J.; Wilkinson, Julia

2017-09-01

With increasing technological dependence, society is becoming ever more affected by changes in the near-Earth space environment caused by space weather. The primary driver of these hazards are coronal mass ejections (CMEs). Solar Stormwatch is a citizen science project in which volunteers participated in several activities which characterized CMEs in the remote sensing images from the Sun Earth Connection Coronal and Heliospheric Investigation (SECCHI) instrument package on the twin STEREO spacecraft. Here we analyze the results of the "Track-it-back" activity, in which CMEs were tracked back through the COR1, COR2, and EUVI images. Analysis of the COR1, COR2, and EUVI data together allows CMEs to be studied consistently throughout the whole field of view spanned by these instruments (out to 15 RS). A total of 4783 volunteers took part in this activity, creating a data set containing 23,801 estimates of CME timing, location, and size. We used these data to produce a catalogue of 41 CMEs, which is the first to consistently track CMEs through each of these instruments. We assess how the CME speeds, propagation directions, and widths vary as the CMEs propagate through the fields of view of the different imagers. In particular, we compare the observed CME deflections between the COR1 and COR2 fields of view to the separation between the CME source region and the heliospheric current sheet (HCS), demonstrating that in general, these CMEs appear to deflect toward the HCS, consistent with other modeling studies of CME propagation.

The Radial Speed-Expansion Speed Relation for Earth-Directed CMEs

NASA Technical Reports Server (NTRS)

Makela, P.; Gopalswamy, N.; Yashiro, S.

2016-01-01

Earth-directed coronal mass ejections (CMEs) are the main drivers of major geomagnetic storms. Therefore, a good estimate of the disturbance arrival time at Earth is required for space weather predictions. The STEREO and SOHO spacecraft were viewing the Sun in near quadrature during January 2010 to September 2012, providing a unique opportunity to study the radial speed (V (sub rad)) to expansion speed(V (sub exp)) relationship of Earth-directed CMEs. This relationship is useful in estimating the V (sub rad) of Earth-directed CMEs, when they are observed from Earth view only. We selected 19 Earth-directed CMEs observed by the Large Angle and Spectrometric Coronagraph (LASCO)/C3 coronagraph on SOHO and the Sun Earth Connection Coronal and Heliospheric Investigation (SECCHI)/COR2 coronagraph on STEREO during January 2010 to September 2012. We found that of the three tested geometric CME models the full ice-cream cone model of the CME describes best the V (sub rad) to V (sub exp) relationship, as suggested by earlier investigations. We also tested the prediction accuracy of the empirical shock arrival (ESA) model proposed by Gopalswamy et al.(2005a), while estimating the CME propagation speeds from the CME expansion speeds. If we use STEREO observations to estimate the CME width required to calculate the V (sub rad) from the V (sub exp) measurements, the mean absolute error (MAE) of the shock arrival times of the ESA model is 8.4 hours. If the LASCO measurements are used to estimate the CME width, the MAE still remains below 17 hours. Therefore, by using the simple V (sub rad) to V (sub exp) relationship to estimate the V (sub rad) of the Earth-directed CMEs, the ESA model is able to predict the shock arrival times with accuracy comparable to most other more complex models.

MULTI-VIEWPOINT OBSERVATIONS OF A WIDELY DISTRIBUTED SOLAR ENERGETIC PARTICLE EVENT: THE ROLE OF EUV WAVES AND WHITE-LIGHT SHOCK SIGNATURES

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kouloumvakos, A.; Patsourakos, S.; Nindos, A.

2016-04-10

On 2012 March 7, two large eruptive events occurred in the same active region within 1 hr from each other. Each consisted of an X-class flare, a coronal mass ejection (CME), an extreme-ultraviolet (EUV) wave, and a shock wave. The eruptions gave rise to a major solar energetic particle (SEP) event observed at widely separated (∼120°) points in the heliosphere. From multi-viewpoint energetic proton recordings we determine the proton release times at STEREO B and A (STB, STA) and the first Lagrange point (L1) of the Sun–Earth system. Using EUV and white-light data, we determine the evolution of the EUVmore » waves in the low corona and reconstruct the global structure and kinematics of the first CME’s shock, respectively. We compare the energetic proton release time at each spacecraft with the EUV waves’ arrival times at the magnetically connected regions and the timing and location of the CME shock. We find that the first flare/CME is responsible for the SEP event at all three locations. The proton release at STB is consistent with arrival of the EUV wave and CME shock at the STB footpoint. The proton release time at L1 was significantly delayed compared to STB. Three-dimensional modeling of the CME shock shows that the particle release at L1 is consistent with the timing and location of the shock’s western flank. This indicates that at L1 the proton release did not occur in low corona but farther away from the Sun. However, the extent of the CME shock fails to explain the SEP event observed at STA. A transport process or a significantly distorted interplanetary magnetic field may be responsible.« less

Tethered Prominence-CME Systems Captured during the 2012 November 13 and 2013 November 3 Total Solar Eclipses

NASA Astrophysics Data System (ADS)

Druckmüller, Miloslav; Habbal, Shadia R.; Alzate, Nathalia; Emmanouilidis, Constantinos

2017-12-01

We report on white light observations of high latitude tethered prominences acquired during the total solar eclipses of 2012 November 13 and 2013 November 3, at solar maximum, with a field of view spanning several solar radii. Distinguished by their pinkish hue, characteristic of emission from neutral hydrogen and helium, the four tethered prominences were akin to twisted flux ropes, stretching out to the limit of the field of view, while remaining anchored at the Sun. Cotemporal observations in the extreme ultraviolet from the Solar Dynamics Observatory (SDO/AIA) clearly showed that the pinkish emission from the cool (≈ {10}4-{10}5 K) filamentary prominences was cospatial with the 30.4 nm He II emission, and was directly linked to filamentary structures emitting at coronal temperatures ≥slant {10}6 K in 17.1 and 19.3 nm. The tethered prominences evolved from typical tornado types. Each one formed the core of different types of coronal mass ejections (CMEs), as inferred from coordinated LASCO C2, C3, and STEREO A and B coronagraph observations. Two of them evolved into a series of faint, unstructured puffs. One was a normal CME. The most striking one was a “light-bulb” type CME, whose three-dimensional structure was confirmed from all four coronagraphs. These first uninterrupted detections of prominence-CME systems anchored at the Sun, and stretching out to at least the edge of the field of view of LASCO C3, provide the first observational confirmation for the source of counter-streaming electron fluxes measured in interplanetary CMEs, or ICMEs.

Major geomagnetic storm due to solar activity (2006-2013).

NASA Astrophysics Data System (ADS)

Tiwari, Bhupendra Kumar

Major geomagnetic storm due to solar activity (2006-2013). Bhupendra Kumar Tiwari Department of Physics, A.P.S.University, Rewa(M.P.) Email: - btiwtari70@yahoo.com mobile 09424981974 Abstract- The geospace environment is dominated by disturbances created by the sun, it is observed that coronal mass ejection (CME) and solar flare events are the causal link to solar activity that produces geomagnetic storm (GMS).CMEs are large scale magneto-plasma structures that erupt from the sun and propagate through the interplanetary medium with speeds ranging from only a few km/s to as large as 4000 km/s. When the interplanetary magnetic field associated with CMEs impinges upon the earth’s magnetosphere and reconnect occur geomagnetic storm. Based on the observation from SOHO/LASCO spacecraft for solar activity and WDC for geomagnetism Kyoto for geomagnetic storm events are characterized by the disturbance storm time (Dst) index during the period 2006-2013. We consider here only intense geomagnetic storm Dst <-100nT, are 12 during 2006-2013.Geomagnetic storm with maximum Dst< -155nT occurred on Dec15, 2006 associated with halo CME with Kp-index 8+ and also verify that halo CME is the main cause to produce large geomagnetic storms.

Sigmoid CME Source Regions at the Sun: Some Recent Results

NASA Technical Reports Server (NTRS)

Sterling, Alphonse C.; Rose, M. Franklin (Technical Monitor)

2000-01-01

Identifying Coronal Mass Ejection (CME) precursors in the solar corona would be an important step in space weather forecasting, as well as a vital key to understanding the physics of CMEs. Twisted magnetic field structures are suspected of being the source of at least some CMEs. These features can appear sigmoid (S or inverse-S) shaped in soft X-ray (SXR) images. We review recent observations of these structures and their relation to CMEs, using soft X-ray (SXR) data from the Soft X-ray Telescope (SXT) on the Yohkoh satellite, and EUV data from the EUV Imaging Telescope (EIT) on the SOHO satellite. These observations indicate that the pre-eruption sigmoid patterns are more prominent in SXRs than in EUV, and that sigmoid precursors are present in over 50% of CMEs. These findings are important for CME research, and may potentially be a major component to space weather forecasting. So far, however, the studies have been subject to restrictions that will have to be relaxed before sigmoid morphology can be used as a reliable predictive tool. Moreover, some CMEs do not display a SXR sigmoid structure prior to eruption, and some others show no prominent SXR signature of any kind before or during eruption.

Sigmoid CME Source Regions at The Sun: Some Recent Results

NASA Technical Reports Server (NTRS)

Sterling, Alphonse C.

2000-01-01

Identifying coronal mass ejection (CME) precursors in the solar corona would be an important step in space weather forecasting, as well as a vital key to understanding the physics of CMEs. Twisted magnetic field structures are suspected of being the source of at least some CMEs. These features can appear sigmoid (S or inverse-S) shaped in soft X-ray, (SXR) images. We review recent observations of these structures and their relation to CMEs. using SXR data from the Soft X-ray Telescope (SXT) on the Yohkoh satellite, and EUV data from the EUV Imaging Telescope (EIT) on the SOHO satellite. These observations indicate that the pre-eruption sigmoid patterns are more prominent in SXRs than in EUV, and that sigmoid precursors are present in over 50% of CMEs. These findings are important for CME research, and may potentially be a major component to space weather forecasting. So far, however, the studies have been subject to restrictions that will have to be relaxed before sigmoid morphology can be used as a reliable predictive too[. Moreover, some CMEs do not display a SXR sigmoid structure prior to eruption, and some others show no prominent SXR signature of any kind before or during eruption.

Dynamical and Physical Properties of a Post-Coronal Mass Ejection Current Sheet

NASA Technical Reports Server (NTRS)

Ko, Yuan-Kuen; Raymond, John C.; Lin, Jun; Lawrence, Gareth; Li, Jing; Fludra, Andrzej

2003-01-01

In the eruptive process of the Kopp-Pneuman type, the closed magnetic field is stretched by the eruption so much that it is usually believed to be " open " to infinity. Formation of the current sheet in such a configuration makes it possible for the energy in the coronal magnetic field to quickly convert into thermal and kinetic energies and cause significant observational consequences, such as growing postflare/CME loop system in the corona, separating bright flare ribbons in the chromosphere, and fast ejections of the plasma and the magnetic flux. An eruption on 2002 January 8 provides us a good opportunity to look into these observational signatures of and place constraints on the theories of eruptions. The event started with the expansion of a magnetic arcade over an active region, developed into a coronal mass ejection (CME), and left some thin streamer-like structures with successively growing loop systems beneath them. The plasma outflow and the highly ionized states of the plasma inside these streamer-like structures, as well as the growing loops beneath them, lead us to conclude that these structures are associated with a magnetic reconnection site, namely, the current sheet, of this eruptive process. We combine the data from the Ultraviolet Coronagraph Spectrometer, Large Angle and Spectrometric Coronagraph Experiment, EUV Imaging Telescope, and Coronal Diagnostic Spectrometer on board the Solar and Heliospheric Observatory, as well is from the Mauna Loa Solar Observatory Mark IV K-coronameter, to investigate the morphological and dynamical properties of this event, as well as the physical properties of the current sheet. The velocity and acceleration of the CME reached up to 1800 km/s and 1 km/sq s, respectively. The acceleration is found to occur mainly at the lower corona (<2.76 Solar Radius). The post-CME loop systems showed behaviors of both postflare loops (upward motion with decreasing speed) and soft X-ray giant arches (upward motion with constant speed, or acceleration) according to the definition of Svestka. In the current sheet, the presence of highly ionized ions, such as Fe(+17) and Ca(+13), suggests temperature as high as (3-4) x 10(exp 6) K, and the plasma outflows have speeds ranging from 300 to 650 km/s. Absolute elemental abundances in the current sheet show a strong first ionization potential effect and have values similar to those found in the active region streamers. The magnetic field strength in the vicinity of the current sheet is found to be of the order of 1 G.

Comparison of interplanetary CME arrival times and solar wind parameters based on the WSA-ENLIL model with three cone types and observations

NASA Astrophysics Data System (ADS)

Jang, Soojeong; Moon, Y.-J.; Lee, Jae-Ok; Na, Hyeonock

2014-09-01

We have made a comparison between coronal mass ejection (CME)-associated shock propagations based on the Wang-Sheeley-Arge (WSA)-ENLIL model using three cone types and in situ observations. For this we use 28 full-halo CMEs, whose cone parameters are determined and their corresponding interplanetary shocks were observed at the Earth, from 2001 to 2002. We consider three different cone types (an asymmetric cone model, an ice cream cone model, and an elliptical cone model) to determine 3-D CME cone parameters (radial velocity, angular width, and source location), which are the input values of the WSA-ENLIL model. The mean absolute error of the CME-associated shock travel times for the WSA-ENLIL model using the ice-cream cone model is 9.9 h, which is about 1 h smaller than those of the other models. We compare the peak values and profiles of solar wind parameters (speed and density) with in situ observations. We find that the root-mean-square errors of solar wind peak speed and density for the ice cream and asymmetric cone model are about 190 km/s and 24/cm3, respectively. We estimate the cross correlations between the models and observations within the time lag of ± 2 days from the shock travel time. The correlation coefficients between the solar wind speeds from the WSA-ENLIL model using three cone types and in situ observations are approximately 0.7, which is larger than those of solar wind density (cc ˜0.6). Our preliminary investigations show that the ice cream cone model seems to be better than the other cone models in terms of the input parameters of the WSA-ENLIL model.

Modeling observations of solar coronal mass ejections with heliospheric imagers verified with the Heliophysics System Observatory.

PubMed

Möstl, C; Isavnin, A; Boakes, P D; Kilpua, E K J; Davies, J A; Harrison, R A; Barnes, D; Krupar, V; Eastwood, J P; Good, S W; Forsyth, R J; Bothmer, V; Reiss, M A; Amerstorfer, T; Winslow, R M; Anderson, B J; Philpott, L C; Rodriguez, L; Rouillard, A P; Gallagher, P; Nieves-Chinchilla, T; Zhang, T L

2017-07-01

We present an advance toward accurately predicting the arrivals of coronal mass ejections (CMEs) at the terrestrial planets, including Earth. For the first time, we are able to assess a CME prediction model using data over two thirds of a solar cycle of observations with the Heliophysics System Observatory. We validate modeling results of 1337 CMEs observed with the Solar Terrestrial Relations Observatory (STEREO) heliospheric imagers (HI) (science data) from 8 years of observations by five in situ observing spacecraft. We use the self-similar expansion model for CME fronts assuming 60° longitudinal width, constant speed, and constant propagation direction. With these assumptions we find that 23%-35% of all CMEs that were predicted to hit a certain spacecraft lead to clear in situ signatures, so that for one correct prediction, two to three false alarms would have been issued. In addition, we find that the prediction accuracy does not degrade with the HI longitudinal separation from Earth. Predicted arrival times are on average within 2.6 ± 16.6 h difference of the in situ arrival time, similar to analytical and numerical modeling, and a true skill statistic of 0.21. We also discuss various factors that may improve the accuracy of space weather forecasting using wide-angle heliospheric imager observations. These results form a first-order approximated baseline of the prediction accuracy that is possible with HI and other methods used for data by an operational space weather mission at the Sun-Earth L5 point.

Radio Remote Sensing of Coronal Mass Ejections: Implications for Parker Solar Probe and Solar Orbiter

NASA Astrophysics Data System (ADS)

Kooi, J. E.; Thomas, N. C.; Guy, M. B., III; Spangler, S. R.

2017-12-01

Coronal mass ejections (CMEs) are fast-moving magnetic field structures of enhanced plasma density that play an important role in space weather. The Solar Orbiter and Parker Solar Probe will usher in a new era of in situ measurements, probing CMEs within distances of 60 and 10 solar radii, respectively. At the present, only remote-sensing techniques such as Faraday rotation can probe the plasma structure of CMEs at these distances. Faraday rotation is the change in polarization position angle of linearly polarized radiation as it propagates through a magnetized plasma (e.g. a CME) and is proportional to the path integral of the electron density and line-of-sight magnetic field. In conjunction with white-light coronagraph measurements, Faraday rotation observations have been used in recent years to determine the magnetic field strength of CMEs. We report recent results from simultaneous white-light and radio observations made of a CME in July 2015. We made radio observations using the Karl G. Jansky Very Large Array (VLA) at 1 - 2 GHz frequencies of a set of radio sources through the solar corona at heliocentric distances that ranged between 8 - 23 solar radii. These Faraday rotation observations provide a priori estimates for comparison with future in situ measurements made by the Solar Orbiter and Parker Solar Probe. Similar Faraday rotation observations made simultaneously with observations by the Solar Orbiter and Parker Solar Probe in the future could provide information about the global structure of CMEs sampled by these probes and, therefore, aid in understanding the in situ measurements.

Modeling observations of solar coronal mass ejections with heliospheric imagers verified with the Heliophysics System Observatory

PubMed Central

Isavnin, A.; Boakes, P. D.; Kilpua, E. K. J.; Davies, J. A.; Harrison, R. A.; Barnes, D.; Krupar, V.; Eastwood, J. P.; Good, S. W.; Forsyth, R. J.; Bothmer, V.; Reiss, M. A.; Amerstorfer, T.; Winslow, R. M.; Anderson, B. J.; Philpott, L. C.; Rodriguez, L.; Rouillard, A. P.; Gallagher, P.; Nieves‐Chinchilla, T.; Zhang, T. L.

2017-01-01

Abstract We present an advance toward accurately predicting the arrivals of coronal mass ejections (CMEs) at the terrestrial planets, including Earth. For the first time, we are able to assess a CME prediction model using data over two thirds of a solar cycle of observations with the Heliophysics System Observatory. We validate modeling results of 1337 CMEs observed with the Solar Terrestrial Relations Observatory (STEREO) heliospheric imagers (HI) (science data) from 8 years of observations by five in situ observing spacecraft. We use the self‐similar expansion model for CME fronts assuming 60° longitudinal width, constant speed, and constant propagation direction. With these assumptions we find that 23%–35% of all CMEs that were predicted to hit a certain spacecraft lead to clear in situ signatures, so that for one correct prediction, two to three false alarms would have been issued. In addition, we find that the prediction accuracy does not degrade with the HI longitudinal separation from Earth. Predicted arrival times are on average within 2.6 ± 16.6 h difference of the in situ arrival time, similar to analytical and numerical modeling, and a true skill statistic of 0.21. We also discuss various factors that may improve the accuracy of space weather forecasting using wide‐angle heliospheric imager observations. These results form a first‐order approximated baseline of the prediction accuracy that is possible with HI and other methods used for data by an operational space weather mission at the Sun‐Earth L5 point. PMID:28983209

A new view of solar coronal mass ejections with the Heliophysics System Observatory (Arne Richter Award for Outstanding Young Scientists Lecture)

NASA Astrophysics Data System (ADS)

Moestl, Christian

2016-04-01

Solar coronal mass ejections (CMEs) play a pivotal role in solar, heliospheric and planetary physics because they lead to connections of plasma phenomena from the Sun to the planets throughout the solar system. CMEs drive the strongest geomagnetic storms, fill the heliosphere with energetic particles, illuminate planetary skies with aurorae, modulate cosmic rays on planetary surfaces, and lead to erosion of planetary atmospheres over long time scales. Thus, even for studying the detection of life on exoplanets, the role of possible stellar CMEs should not be neglected. However, besides the simple fascination of studying the biggest explosions in the solar system, they are of increasingly high practical significance concerning risk mitigation of natural desasters and the protection of our common wealth. As the impact of a "super-CME", a rare but possible event, may affect the entire planet Earth, coordinated international efforts for their fundamental understanding, as well as building dedicated space weather missions for daily forecasts is necessary. There is a chance of a CME on the order of a Carrington event, with a minimum Dst of about -1000 nT, impacting Earth once every 100 years - or a 10% chance in a given solar cycle. An impact of such a super-CME is expected to cause e.g. wide-spread electricity blackouts and satellite failures. In the last 10 years, the field has made major advantages in understanding how CMEs evolve from the Sun to the planets. Because of the extension of CMEs on the order of 60-100 degree heliospheric longitude and radial sizes around 0.1-0.2 AU, multipoint imaging and in situ observations are inevitably necessary to understand basic CME physics. To this end, I will show data, as provided by the Heliophysics System Observatory (HSO), and their interpretation with various modeling effors. The HSO can be understood as a web of sensors placed throughout the heliosphere, consisting of spacecraft such as STEREO, Wind, ACE, Venus Express and MESSENGER. They provide, mainly with their magnetometers, multipoint in situ observations of CMEs. The STEREO mission plays a key role, as it has provided for the first time data of heliospheric imagers far away from the Sun-Earth line. This data set now covers almost a full solar cycle, bridging the observational gap between the Sun and the terrestrial planets. This means that we are now entering a new era where big catalogues of solar and heliospheric events are routinely available. I further focus on unsolved problems in the field, such as finding connections between coronagraph, heliospheric imaging and in situ CME detections, and understanding the global shape of the CME shock and magnetic flux rope. The biggest problem concerns the prediction of the CME core magnetic field, and in particular its Bz profile, which is the main reason why space weather prediction is still quite inaccurate. Finally, the upcoming missions Solar Orbiter and Solar Probe Plus are bound to disruptively transform the field in the upcoming years with out-of-ecliptic heliospheric imaging and in situ observations of the Sun's corona.

Farside Halo

NASA Image and Video Library

2017-12-08

There's no way to tell from this SOHO image whether the halo CME on March 5, 2013, originated from the front or far of the sun. But the STEREO spacecraft were watching the sun from the sides and showed it was from the far side. The bright planet is Venus. Credit: NASA/SOHO CME WEEK: What To See in CME Images Two main types of explosions occur on the sun: solar flares and coronal mass ejections. Unlike the energy and x-rays produced in a solar flare – which can reach Earth at the speed of light in eight minutes – coronal mass ejections are giant, expanding clouds of solar material that take one to three days to reach Earth. Once at Earth, these ejections, also called CMEs, can impact satellites in space or interfere with radio communications. During CME WEEK from Sept. 22 to 26, 2014, we explore different aspects of these giant eruptions that surge out from the star we live with. When a coronal mass ejection blasts off the sun, scientists rely on instruments called coronagraphs to track their progress. Coronagraphs block out the bright light of the sun, so that the much fainter material in the solar atmosphere -- including CMEs -- can be seen in the surrounding space. CMEs appear in these images as expanding shells of material from the sun's atmosphere -- sometimes a core of colder, solar material (called a filament) from near the sun's surface moves in the center. But mapping out such three-dimensional components from a two-dimensional image isn't easy. Watch the slideshow to find out how scientists interpret what they see in CME pictures. The images in the slideshow are from the three sets of coronagraphs NASA currently has in space. One is on the joint European Space Agency and NASA Solar and Heliospheric Observatory, or SOHO. SOHO launched in 1995, and sits between Earth and the sun about a million miles away from Earth. The other two coronagraphs are on the two spacecraft of the NASA Solar Terrestrial Relations Observatory, or STEREO, mission, which launched in 2006. The two STEREO spacecraft are both currently viewing the far side of the sun. Together these instruments help scientists create a three-dimensional model of any CME as its journey unfolds through interplanetary space. Such information can show why a given characteristic of a CME close to the sun might lead to a given effect near Earth, or any other planet in the solar system...NASA image use policy. NASA Goddard Space Flight Center enables NASA’s mission through four scientific endeavors: Earth Science, Heliophysics, Solar System Exploration, and Astrophysics. Goddard plays a leading role in NASA’s accomplishments by contributing compelling scientific knowledge to advance the Agency’s mission. Follow us on Twitter Like us on Facebook Find us on Instagram

X-ray and EUV Observations of CME Eruption Onset

NASA Technical Reports Server (NTRS)

Sterling, A. C.

2004-01-01

Why Coronal Mass Ejections (CMEs) erupt is a major outstanding puzzle of solar physics. Signatures observable at the earliest stages of eruption onset may hold precious clues about the onset mechanism. We present observations from SOHO/EIT and from TRACE in EUV, and from Yohkoh/SXT in soft X-rays of the pre-eruption and eruption phases of CME expulsion, along with the eruption's magnetic setting found from SOHO/MDI magnetograms. Most of our events involve clearly-observable filament eruptions and multiple neutral lines, and we use the magnetic settings and motions of the filaments to help infer the geometry and behavior of the associated erupting magnetic fields. Pre-eruption and early-eruption signatures include a relatively slow filament rise prior to eruption, and intensity "dimmings" and brightenings, both in the immediate neighborhood of the "core" (location of greatest magnetic shear) of the erupting fields and at locations remote from the core. These signatures and their relative timings place observational constraints on eruption mechanisms; our recent work has focused on implications for the so-called "tether cutting" and "breakout" models, but the same observational constraints are applicable to any model.

Observations and Interpretations of Energetic Neutral Hydrogen Atoms from the December 5, 2006 Solar Event

NASA Technical Reports Server (NTRS)

Mewaldt, R. A.; Leske, R. A.; Shih, A. Y.; Stone, E. C.; Barghouty, A. f.; Cohen, C. M. S.; Cummings, A. c.; Labrador, A. W.; vonRosenvinge, T. T.

2009-01-01

We discuss recently reported observations of energetic neutral hydrogen atoms (ENAs) from an X9 solar flare/coronal mass ejection event on 5 December 2006, located at E79. The observations were made by the Low Energy Telescopes (LETs) on STEREO A and B. Prior to the arrival of the main solar energetic particle (SEP) event at Earth, both LETs observed a sudden burst of 1.6 to 15 MeV energetic neutral hydrogen atoms produced by either flare or shock-accelerated protons. RHESSI measurements of the 2.2-MeV gamma-ray line provide an estimate of the number of interacting flare-accelerated protons in this event, which leads to an improved estimate of ENA production by flare-accelerated protons. Taking into account ENA losses, we find that the observed ENAs must have been produced in the high corona at heliocentric distances > or equal to 2 solar radii. Although there are no CME images from this event, it is shown that CME-shock-accelerated protons can, in principle, produce a time-history consistent with the observations.

Coronal Mass Ejections and their Implications for the Corona and Heliosphere

NASA Technical Reports Server (NTRS)

Antiochos, Spiro K.

2008-01-01

Coronal mass ejections (CMEs) are the largest and most energetic form of transients that connect the Sun to the heliosphere. They are critically important both for understanding the physical mechanisms of explosive solar activity and for predicting space weather. Furthermore they are an extreme example of how cross-scale coupling can play a critical role in determining the properties of a large-scale dynamical system. In this presentation CME theories are reviewed and the latest results from 3D numerical modeling of CME initiation propagation to the heliosphere are presented. In particular the focus is on the breakout model, but many of the results hold for the flux rope models as well. The implications of these results for understanding heliospheric structure and dynamics and for upcoming space missions will be discussed.

Asymmetry in the CME-CME interaction process for the events from 2011 February 14-15

DOE Office of Scientific and Technical Information (OSTI.GOV)

Temmer, M.; Veronig, A. M.; Peinhart, V.

2014-04-20

We present a detailed study of the interaction process of two coronal mass ejections (CMEs) successively launched on 2011 February 14 (CME1) and 2011 February 15 (CME2). Reconstructing the three-dimensional shape and evolution of the flux ropes, we verify that the two CMEs interact. The frontal structure of both CMEs, measured along different position angles (PAs) over the entire latitudinal extent, reveals differences in the kinematics for the interacting flanks and the apexes. The interaction process is strongly PA-dependent in terms of timing as well as kinematical evolution. The central interaction occurs along PA-100°, which shows the strongest changes inmore » kinematics. During interaction, CME1 accelerates from ∼400 km s{sup –1} to ∼700 km s{sup –1} and CME2 decelerates from ∼1300 km s{sup –1} to ∼600 km s{sup –1}. Our results indicate that a simplified scenario such as inelastic collision may not be sufficient to describe the CME-CME interaction. The magnetic field structures of the intertwining flux ropes and the momentum transfer due to shocks each play an important role in the interaction process.« less

Coronal mass ejection (CME) activity of low mass M stars as an important factor for the habitability of terrestrial exoplanets. I. CME impact on expected magnetospheres of Earth-like exoplanets in close-in habitable zones.

PubMed

Khodachenko, Maxim L; Ribas, Ignasi; Lammer, Helmut; Griessmeier, Jean-Mathias; Leitner, Martin; Selsis, Franck; Eiroa, Carlos; Hanslmeier, Arnold; Biernat, Helfried K; Farrugia, Charles J; Rucker, Helmut O

2007-02-01

Low mass M- and K-type stars are much more numerous in the solar neighborhood than solar-like G-type stars. Therefore, some of them may appear as interesting candidates for the target star lists of terrestrial exoplanet (i.e., planets with mass, radius, and internal parameters identical to Earth) search programs like Darwin (ESA) or the Terrestrial Planet Finder Coronagraph/Inferometer (NASA). The higher level of stellar activity of low mass M stars, as compared to solar-like G stars, as well as the closer orbital distances of their habitable zones (HZs), means that terrestrial-type exoplanets within HZs of these stars are more influenced by stellar activity than one would expect for a planet in an HZ of a solar-like star. Here we examine the influences of stellar coronal mass ejection (CME) activity on planetary environments and the role CMEs may play in the definition of habitability criterion for the terrestrial type exoplanets near M stars. We pay attention to the fact that exoplanets within HZs that are in close proximity to low mass M stars may become tidally locked, which, in turn, can result in relatively weak intrinsic planetary magnetic moments. Taking into account existing observational data and models that involve the Sun and related hypothetical parameters of extrasolar CMEs (density, velocity, size, and occurrence rate), we show that Earth-like exoplanets within close-in HZs should experience a continuous CME exposure over long periods of time. This fact, together with small magnetic moments of tidally locked exoplanets, may result in little or no magnetospheric protection of planetary atmospheres from a dense flow of CME plasma. Magnetospheric standoff distances of weakly magnetized Earth-like exoplanets at orbital distances

Coronal mass ejection hits mercury: A.I.K.E.F. hybrid-code results compared to MESSENGER data

NASA Astrophysics Data System (ADS)

Exner, W.; Heyner, D.; Liuzzo, L.; Motschmann, U.; Shiota, D.; Kusano, K.; Shibayama, T.

2018-04-01

Mercury is the closest orbiting planet around the sun and is therefore embedded in an intensive and highly varying solar wind. In-situ data from the MESSENGER spacecraft of the plasma environment near Mercury indicates that a coronal mass ejection (CME) passed the planet on 23 November 2011 over the span of the 12 h MESSENGER orbit. Slavin et al. (2014) derived the upstream parameters of the solar wind at the time of that orbit, and were able to explain the observed MESSENGER data in the cusp and magnetopause segments of MESSENGER's trajectory. These upstream parameters will be used for our first simulation run. We use the hybrid code A.I.K.E.F. which treats ions as individual particles and electrons as a mass-less fluid, to conduct hybrid simulations of Mercury's magnetospheric response to the impact of the CME on ion gyro time scales. Results from the simulation are in agreement with magnetic field measurements from the inner day-side magnetosphere and the bow-shock region. However, at the planet's nightside, Mercury's plasma environment seemed to be governed by different solar wind conditions, in conclusion, Mercury's interaction with the CME is not sufficiently describable by only one set of upstream parameters. Therefore, to simulate the magnetospheric response while MESSENGER was located in the tail region, we use parameters obtained from the MHD solar wind simulation code SUSANOO (Shiota et al. (2014)) for our second simulation run. The parameters of the SUSANOO model achieve a good agreement of the data concerning the plasma tail crossing and the night-side approach to Mercury. However, the polar and closest approach are hardly described by both upstream parameters, namely, neither upstream dataset is able to reproduce the MESSENGER crossing of Mercury's magnetospheric cusp. We conclude that the respective CME was too variable on the timescale of the MESSENGER orbit to be described by only two sets of upstream conditions. Our results suggest locally strong and highly variable dynamics of the CME on timescales of 15 min while MESSENGER was near closest approach.

Relativistic Heliospheric Electrons - Source, Energization and Magnetic Topology

NASA Astrophysics Data System (ADS)

Roth, Ilan

2010-05-01

Relativistic Solar Electrons are observed in conjunction with flares or coronal mass ejections (CMEs), however their origin, energization and the underlying topology seem elusive. The existence of non-thermal electrons in the solar atmosphere and along the heliospheric field lines is deduced through emission of electromagnetic waves and via direct in situ measurements. Magnetic reconnection at the flare sites may result in short term fluxes of energetic electrons, however it cannot explain the long-term relativistic fluxes as observed at 1 AU. In contrast to ions, electrons are not observed with MeV energies at the propagating CME shock. Their spectral shapes and the relative timing with respect to imaging and spectrographic observations may identify potential acceleration topology and processes controlling the formation of the (delayed with respect to a timing of a flare or initiation of CME) relativistic electrons. It is conjectured that the acceleration occurs along the stretched, closed coronal field lines, when an anisotropic seed population of low-energy electrons is injected in conjunction with the high frequency coronal radio bursts behind the large CME, as recorded by radioheliographs. This topology allows sufficient time for incubation of the accelerated electrons while the energization proceeds as a bootstrap process due to resonant interaction with oblique whistler waves, which are excited by the seed electrons. The flare serves mainly as a time reference for the electromagnetic emissions, while the CME subsequently opens an access for the relativistic electrons to the interplanetary medium. Power-laws of the energetic electron distributions are shown to be due to statistical interaction allowing discerning of the processes, which result in the observed non-Gaussian distributions, as well as time scales of their evolution.

Combining Stereo SECCHI COR2 and HI1 Images for Automatic CME Front Edge Tracking

NASA Technical Reports Server (NTRS)

Kirnosov, Vladimir; Chang, Lin-Ching; Pulkkinen, Antti

2016-01-01

COR2 coronagraph images are the most commonly used data for coronal mass ejection (CME) analysis among the various types of data provided by the STEREO (Solar Terrestrial Relations Observatory) SECCHI (Sun-Earth Connection Coronal and Heliospheric Investigation) suite of instruments. The field of view (FOV) in COR2 images covers 215 solar radii (Rs) that allow for tracking the front edge of a CME in its initial stage to forecast the lead-time of a CME and its chances of reaching the Earth. However, estimating the lead-time of a CME using COR2 images gives a larger lead-time, which may be associated with greater uncertainty. To reduce this uncertainty, CME front edge tracking should be continued beyond the FOV of COR2 images. Therefore, heliospheric imager (HI1) data that covers 1590 Rs FOV must be included. In this paper, we propose a novel automatic method that takes both COR2 and HI1 images into account and combine the results to track the front edges of a CME continuously. The method consists of two modules: pre-processing and tracking. The pre-processing module produces a set of segmented images, which contain the signature of a CME, for both COR2 and HI1 separately. In addition, the HI1 images are resized and padded, so that the center of the Sun is the central coordinate of the resized HI1 images. The resulting COR2 andHI1 image set is then fed into the tracking module to estimate the position angle (PA) and track the front edge of a CME. The detected front edge is then used to produce a height-time profile that is used to estimate the speed of a CME. The method was validated using 15 CME events observed in the period from January 1, 2008 to August 31, 2009. The results demonstrate that the proposed method is effective for CME front edge tracking in both COR2 and HI1 images. Using this method, the CME front edge can now be tracked automatically and continuously in a much larger range, i.e., from 2 to 90 Rs, for the first time. These improvement scan greatly help in making the quantitative CME analysis more accurate and have the potential to assist in space weather forecasting.

The Relationship Between CME Properties in the CDAW, CACTUS and SEEDS Catalogs and ?25 MeV Solar Proton Event Intensities

NASA Astrophysics Data System (ADS)

Richardson, I. G.; von Rosenvinge, T. T.; Cane, H. V.

2013-12-01

The existence of a correlation between the intensity of solar energetic proton (SEP) events and the speed of the associated coronal mass ejection near the Sun is well known, and is often interpreted as evidence for particle acceleration at CME-driven shocks. However, this correlation is far from perfect and might be improved by taking other parameters into consideration (e.g., CME width). In studies of cycle 23 SEP events, values of CME speed, width and other parameters were typically taken from the CDAWWeb LASCO CME catalog. This is compiled 'by hand' from examination of LASCO images by experienced observers. Other automated LASCO CME catalogs have now been developed, e.g., CACTUS (Royal Observatory of Belgium) and SEEDS (George Mason University), but the basic CME parameters do not always agree with those from the CDAWweb catalog since they are not determined in the same way. For example the 'CME speed' might be measured at a specific position angle against the plane of the sky in one catalog, or be the average of speeds taken along the CME front in another. Speeds may also be based on linear or higher order fits to the coronagraph images. There will also be projection effects in these plane of the sky speeds. Similarly, CME widths can vary between catalogs and are dependent on how they are defined. For example, the CDAW catalog lists any CME that surrounds the occulting disk as a 'halo' (360 deg. width) CME even though the CME may be highly-asymmetric and originate from a solar event far from central meridian. Another catalog may give a smaller width for the same CME. The problem of obtaining the 'true' CME width is especially acute for assessing the relationship between CME width and SEP properties when using the CDAW catalog since a significant fraction, if not the majority, of the CMEs associated with major SEP events are reported to be halo CMEs. In principle, observations of CMEs from the STEREO A and B spacecraft, launched in late 2006, might be used to overcome some of these problems. In particular, a spacecraft in quadrature with the solar source of an SEP event should observe the 'true' width and speed of the associated CME. However, STEREO CME parameters are derived using the CACTUS method, and cannot be directly compared with the LASCO CDAW catalog values that have been so widely used for many years. In this study, we will examine the relationship between the properties of CMEs in various catalogs and the intensities of a large sample of particle events that include ˜25 MeV protons in cycles 23 and 24. In particular, we will compare the proton intensity-speed relationships obtained using the CDAW, CACTUS and SEEDS LASCO catalogs, and also using the CACTUS values from whichever spacecraft (STEREO A, B or SOHO) is best in quadrature with the solar event. We will also examine whether there is any correlation between the width of the CMEs in the automated catalogs and proton intensity, and whether a combination of CME speed and width might improve the correlation with proton intensity.

Observations and Analyses of Heliospheric Faraday Rotation of a Coronal Mass Ejection (CME) Using the LOw Frequency ARray (LOFAR) and Space-Based Imaging Techniques

NASA Astrophysics Data System (ADS)

Bisi, Mario Mark; Jensen, Elizabeth; Sobey, Charlotte; Fallows, Richard; Jackson, Bernard; Barnes, David; Giunta, Alessandra; Hick, Paul; Eftekhari, Tarraneh; Yu, Hsiu-Shan; Odstrcil, Dusan; Tokumaru, Munetoshi; Wood, Brian

2017-04-01

Geomagnetic storms of the highest intensity are general driven by coronal mass ejections (CMEs) impacting the Earth's space environment. Their intensity is driven by the speed, density, and, most-importantly, their magnetic-field orientation and magnitude of the incoming solar plasma. The most-significant magnetic-field factor is the North-South component (Bz in Geocentric Solar Magnetic - GSM - coordinates). At present, there are no reliable prediction methods available for this magnetic-field component ahead of the in-situ monitors around the Sun-Earth L1 point. Observations of Faraday rotation (FR) can be used to attempt to determine average magnetic-field orientations in the inner heliosphere. Such a technique has already been well demonstrated through the corona, ionosphere, and also the interstellar medium. Measurements of the polarisation of astronomical (or spacecraft in superior conjunction) radio sources (beacons/radio frequency carriers) through the inner corona of the Sun to obtain the FR have been demonstrated but mostly at relatively-high radio frequencies. Here we show some initial results of true heliospheric FR using the Low Frequency Array (LOFAR) below 200 MHz to investigate the passage of a coronal mass ejection (CME) across the line of sight. LOFAR is a next-generation low-frequency radio interferometer, and a pathfinder to the Square Kilometre Array (SKA) - LOW telescope. We demonstrate preliminary heliospheric FR results through the analysis of observations of pulsar J1022+1001, which commenced on 13 August 2014 at 13:00UT and spanned over 150 minutes in duration. We also show initial comparisons to the FR results via various modelling techniques and additional context information to understand the structure of the inner heliosphere being detected. This observation could indeed pave the way to an experiment which might be implemented for space-weather purposes that will eventually lead to a near-global method for determining the magnetic field throughout the inner heliosphere.

Observational methods for solar origin diagnostics of energetic protons

NASA Astrophysics Data System (ADS)

Miteva, Rositsa

2017-12-01

The aim of the present report is to outline the observational methods used to determine the solar origin - in terms of flares and coronal mass ejections (CMEs) - of the in situ observed solar energetic protons. Several widely used guidelines are given and different sources of uncertainties are summarized and discussed. In the present study, a new quality factor is proposed as a certainty check on the so-identified flare-CME pairs. In addition, the correlations between the proton peak intensity and the properties of their solar origin are evaluated as a function of the quality factor.

Study of magnetic helicity injection in the active region NOAA 9236 producing multiple flare-associated coronal mass ejection events

DOE Office of Scientific and Technical Information (OSTI.GOV)

Park, Sung-Hong; Cho, Kyung-Suk; Bong, Su-Chan

To better understand a preferred magnetic field configuration and its evolution during coronal mass ejection (CME) events, we investigated the spatial and temporal evolution of photospheric magnetic fields in the active region NOAA 9236 that produced eight flare-associated CMEs during the time period of 2000 November 23-26. The time variations of the total magnetic helicity injection rate and the total unsigned magnetic flux are determined and examined not only in the entire active region but also in some local regions such as the main sunspots and the CME-associated flaring regions using SOHO/MDI magnetogram data. As a result, we found thatmore » (1) in the sunspots, a large amount of positive (right-handed) magnetic helicity was injected during most of the examined time period, (2) in the flare region, there was a continuous injection of negative (left-handed) magnetic helicity during the entire period, accompanied by a large increase of the unsigned magnetic flux, and (3) the flaring regions were mainly composed of emerging bipoles of magnetic fragments in which magnetic field lines have substantially favorable conditions for making reconnection with large-scale, overlying, and oppositely directed magnetic field lines connecting the main sunspots. These observational findings can also be well explained by some MHD numerical simulations for CME initiation (e.g., reconnection-favored emerging flux models). We therefore conclude that reconnection-favored magnetic fields in the flaring emerging flux regions play a crucial role in producing the multiple flare-associated CMEs in NOAA 9236.« less

Current Sheet Structures Observed by the TESIS EUV Telescope during a Flux Rope Eruption on the Sun

NASA Astrophysics Data System (ADS)

Reva, A. A.; Ulyanov, A. S.; Kuzin, S. V.

2016-11-01

We use the TESIS EUV telescope to study the current sheet signatures observed during flux rope eruption. The special feature of the TESIS telescope was its ability to image the solar corona up to a distance of 2 {R}⊙ from the Sun’s center in the Fe 171 Å line. The Fe 171 Å line emission illuminates the magnetic field lines, and the TESIS images reveal the coronal magnetic structure at high altitudes. The analyzed coronal mass ejection (CME) had a core with a spiral—flux rope—structure. The spiral shape indicates that the flux rope radius varied along its length. The flux rope had a complex temperature structure: cold legs (70,000 K, observed in He 304 Å line) and a hotter core (0.7 MK, observed in Fe 171 Å line). Such a structure contradicts the common assumption that the CME core is a cold prominence. When the CME impulsively accelerated, a dark double Y-structure appeared below the flux rope. The Y-structure timing, location, and morphology agree with the previously performed MHD simulations of the current sheet. We interpreted the Y-structure as a hot envelope of the current sheet and hot reconnection outflows. The Y-structure had a thickness of 6.0 Mm. Its length increased over time from 79 Mm to more than 411 Mm.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Lugaz, N.; Shibata, K.; Downs, C.

We present a numerical investigation of the coronal evolution of a coronal mass ejection (CME) on 2005 August 22 using a three-dimensional thermodynamic magnetohydrodynamic model, the space weather modeling framework. The source region of the eruption was anemone active region (AR) 10798, which emerged inside a coronal hole. We validate our modeled corona by producing synthetic extreme-ultraviolet (EUV) images, which we compare to EIT images. We initiate the CME with an out-of-equilibrium flux rope with an orientation and chirality chosen in agreement with observations of an H{alpha} filament. During the eruption, one footpoint of the flux rope reconnects with streamermore » magnetic field lines and with open field lines from the adjacent coronal hole. It yields an eruption which has a mix of closed and open twisted field lines due to interchange reconnection and only one footpoint line-tied to the source region. Even with the large-scale reconnection, we find no evidence of strong rotation of the CME as it propagates. We study the CME deflection and find that the effect of the Lorentz force is a deflection of the CME by about 3{sup 0} R{sup -1}{sub sun} toward the east during the first 30 minutes of the propagation. We also produce coronagraphic and EUV images of the CME, which we compare with real images, identifying a dimming region associated with the reconnection process. We discuss the implication of our results for the arrival at Earth of CMEs originating from the limb and for models to explain the presence of open field lines in magnetic clouds.« less

An Analysis of the Origin and Propagation of the Multiple Coronal Mass Ejections of 2010 August 1

NASA Technical Reports Server (NTRS)

Harrison, R. A.; Davies, J. A.; Moestl, C.; Liu, Y.; Temmer, M.; Bisi, M. M.; Eastwood, J. P.; DeKoning, C. A.; Nitta, N.; Rollett, T.;

Numerical modeling of coronal mass ejections based on various pre-event model atmospheres

NASA Technical Reports Server (NTRS)

Suess, S. T.; Wang, A. H.; Wu, S. T.; Poletto, G.

1994-01-01

We examine how the initial state (pre-event corona) affects the numerical MHD simulation for a coronal mass ejection (CME). Earlier simulations based on a pre-event corona with a homogeneous density and temperature distribution at lower boundary (i.e. solar surface) have been used to analyze the role of streamer properties in determining the characteristics of loop-like transients. The present paper extends these studies to show how a broader class of global coronal properties leads not only to different types of CME's, but also modifies the adjacent quiet corona and/or coronal holes. We consider four pre-event coronal cases: (1) Constant boundary conditions and a polytropic gas with gamma = 1.05; (2) Non-constant (latitude dependent) boundary conditions and a polytropic gas with gamma = 1.05; (3) Constant boundary conditions with a volumetric energy source and gamma = 1.67; (4) Non-constant (latitude dependent) boundary conditions with a volumetric energy source and gamma = 1.67. In all models, the pre-event magnetic fields separate the corona into closed field regions (streamers) and open field regions. The CME's initiation is simulated by introducing at the base of the corona, within the streamer region, a standard pressure pulse and velocity change. Boundary values are determined using MHD characteristic theory. The simulations show how different CME's, including loop-like transients, clouds, and bright rays, might occur. There are significant new features in comparison to published results. We conclude that the pre-event corona is a crucial factor in dictating CME's properties.

Numerical Modeling of Coronal Mass Ejections Based on Various Pre-event Model Atmospheres

NASA Technical Reports Server (NTRS)

Wang, A. H.; Wu, S. T.; Suess, S. T.; Poletto, G.

1995-01-01

We examine how the initial state (pre-event corona) affects the numerical MHD simulation for a coronal mass ejection (CME). Earlier simulations based on a pre-event corona with a homogeneous density and temperature distribution, at the lower boundary (i.e., solar surface) have been used to analyze the role of streamer properties in determining the characteristics of loop-like transients. The present paper extends these studies to show how a broader class of global coronal properties leads not only to different types of CME's, but also modifies the adjacent quiet corona and/or coronal holes. We consider four pre-event coronal cases: (1) constant boundary conditions and a polytropic gas with gamma = 1.05; (2) non-constant (latitude dependent) boundary conditions and a polytropic gas with gamma = 1.05; (3) constant boundary conditions with a volumetric energy source and gamma = 1.67; (4) non-constant (latitude dependent) boundary conditions with a volumetric energy source and gamma = 1.67. In all models, the pre-event magnetic fields separate the corona into closed field regions (streamers) and open field regions. The CME's initiation is simulated by introducing at the base of the corona, within the streamer region, a standard pressure pulse and velocity change. Boundary values are determined using magnetohydrodynamic (MHD) characteristic theory. The simulations show how different CME's, including loop-like transients, clouds and bright rays, might occur. There are significant new features in comparison to published results. We conclude that the pre-event corona is a crucial factor in dictating CME's properties.

Effect of Solar Wind Drag on the Determination of the Properties of Coronal Mass Ejections from Heliospheric Images

NASA Astrophysics Data System (ADS)

Lugaz, N.; Kintner, P.

2013-07-01

The Fixed-Φ (FΦ) and Harmonic Mean (HM) fitting methods are two methods to determine the "average" direction and velocity of coronal mass ejections (CMEs) from time-elongation tracks produced by Heliospheric Imagers (HIs), such as the HIs onboard the STEREO spacecraft. Both methods assume a constant velocity in their descriptions of the time-elongation profiles of CMEs, which are used to fit the observed time-elongation data. Here, we analyze the effect of aerodynamic drag on CMEs propagating through interplanetary space, and how this drag affects the result of the FΦ and HM fitting methods. A simple drag model is used to analytically construct time-elongation profiles which are then fitted with the two methods. It is found that higher angles and velocities give rise to greater error in both methods, reaching errors in the direction of propagation of up to 15∘ and 30∘ for the FΦ and HM fitting methods, respectively. This is due to the physical accelerations of the CMEs being interpreted as geometrical accelerations by the fitting methods. Because of the geometrical definition of the HM fitting method, it is more affected by the acceleration than the FΦ fitting method. Overall, we find that both techniques overestimate the initial (and final) velocity and direction for fast CMEs propagating beyond 90∘ from the Sun-spacecraft line, meaning that arrival times at 1 AU would be predicted early (by up to 12 hours). We also find that the direction and arrival time of a wide and decelerating CME can be better reproduced by the FΦ due to the cancelation of two errors: neglecting the CME width and neglecting the CME deceleration. Overall, the inaccuracies of the two fitting methods are expected to play an important role in the prediction of CME hit and arrival times as we head towards solar maximum and the STEREO spacecraft further move behind the Sun.

Solar Radio Bursts and Space Weather

NASA Technical Reports Server (NTRS)

Gopalswamy, Natchimuthuk,

2012-01-01

Radio bursts from the Sun are produced by electron accelerated to relativistic energies by physical processes on the Sun such as solar flares and coronal mass ejections (CMEs). The radio bursts are thus good indicators of solar eruptions. Three types of nonthermal radio bursts are generally associated with CMEs. Type III bursts due to accelerated electrons propagating along open magnetic field lines. The electrons are thought to be accelerated at the reconnection region beneath the erupting CME, although there is another view that the electrons may be accelerated at the CME-driven shock. Type II bursts are due to electrons accelerated at the shock front. Type II bursts are also excellent indicators of solar energetic particle (SEP) events because the same shock is supposed accelerate electrons and ions. There is a hierarchical relationship between the wavelength range of type /I bursts and the CME kinetic energy. Finally, Type IV bursts are due to electrons trapped in moving or stationary structures. The low frequency stationary type IV bursts are observed occasionally in association with very fast CMEs. These bursts originate from flare loops behind the erupting CME and hence indicate tall loops. This paper presents a summary of radio bursts and their relation to CMEs and how they can be useful for space weather predictions.

Sawtooth events and O+ in the plasma sheet and boundary layer: CME- and SIR-driven events

NASA Astrophysics Data System (ADS)

Lund, E. J.; Nowrouzi, N.; Kistler, L. M.; Cai, X.; Liao, J.

2017-12-01

The role of ionospheric ions in sawtooth events is an open question. Simulations[1,2,3] suggest that O+ from the ionosphere produces a feedback mechanism for driving sawtooth events. However, observational evidence[4,5] suggest that the presence of O+ in the plasma sheet is neither necessary nor sufficient. In this study we investigate whether the solar wind driver of the geomagnetic storm has an effect on the result. Building on an earlier study[4] that used events for which Cluster data is available in the plasma sheet and boundary layer, we perform a superposed epoch analysis for coronal mass ejection (CME) driven storms and streaming interaction region (SIR) driven storms separately, to investigate the hypothesis that ionospheric O+ is an important contributor for CME-driven storms but not SIR-driven storms[2]. [1]O. J. Brambles et al. (2011), Science 332, 1183.[2]O. J. Brambles et al. (2013), JGR 118, 6026.[3]R. H. Varney et al. (2016), JGR 121, 9688.[4]J. Liao et al. (2014), JGR 119, 1572.[5]E. J. Lund et al. (2017), JGR, submitted.

Capabilities of a Global 3D MHD Model for Monitoring Extremely Fast CMEs

NASA Astrophysics Data System (ADS)

Wu, C. C.; Plunkett, S. P.; Liou, K.; Socker, D. G.; Wu, S. T.; Wang, Y. M.

2015-12-01

Since the start of the space era, spacecraft have recorded many extremely fast coronal mass ejections (CMEs) which have resulted in severe geomagnetic storms. Accurate and timely forecasting of the space weather effects of these events is important for protecting expensive space assets and astronauts and avoiding communications interruptions. Here, we will introduce a newly developed global, three-dimensional (3D) magnetohydrodynamic (MHD) model (G3DMHD). The model takes the solar magnetic field maps at 2.5 solar radii (Rs) and intepolates the solar wind plasma and field out to 18 Rs using the algorithm of Wang and Sheeley (1990, JGR). The output is used as the inner boundary condition for a 3D MHD model. The G3DMHD model is capable of simulating (i) extremely fast CME events with propagation speeds faster than 2500 km/s; and (ii) multiple CME events in sequence or simultaneously. We will demonstrate the simulation results (and comparison with in-situ observation) for the fastest CME in record on 23 July 2012, the shortest transit time in March 1976, and the well-known historic Carrington 1859 event.

PREDICTING CME EJECTA AND SHEATH FRONT ARRIVAL AT L1 WITH A DATA-CONSTRAINED PHYSICAL MODEL

DOE Office of Scientific and Technical Information (OSTI.GOV)

Hess, Phillip; Zhang, Jie, E-mail: phess4@gmu.edu

2015-10-20

We present a method for predicting the arrival of a coronal mass ejection (CME) flux rope in situ, as well as the sheath of solar wind plasma accumulated ahead of the driver. For faster CMEs, the front of this sheath will be a shock. The method is based upon geometrical separate measurement of the CME ejecta and sheath. These measurements are used to constrain a drag-based model, improved by including both a height dependence and accurate de-projected velocities. We also constrain the geometry of the model to determine the error introduced as a function of the deviation of the CMEmore » nose from the Sun–Earth line. The CME standoff-distance in the heliosphere fit is also calculated, fit, and combined with the ejecta model to determine sheath arrival. Combining these factors allows us to create predictions for both fronts at the L1 point and compare them against observations. We demonstrate an ability to predict the sheath arrival with an average error of under 3.5 hr, with an rms error of about 1.58 hr. For the ejecta the error is less than 1.5 hr, with an rms error within 0.76 hr. We also discuss the physical implications of our model for CME expansion and density evolution. We show the power of our method with ideal data and demonstrate the practical implications of having a permanent L5 observer with space weather forecasting capabilities, while also discussing the limitations of the method that will have to be addressed in order to create a real-time forecasting tool.« less

The 2015 Summer Solstice Storm: One of the Major Geomagnetic Storms of Solar Cycle 24 Observed at Ground Level

NASA Astrophysics Data System (ADS)

Augusto, C. R. A.; Navia, C. E.; de Oliveira, M. N.; Nepomuceno, A. A.; Raulin, J. P.; Tueros, E.; de Mendonça, R. R. S.; Fauth, A. C.; Vieira de Souza, H.; Kopenkin, V.; Sinzi, T.

2018-05-01

We report on the 22 - 23 June 2015 geomagnetic storm that occurred at the summer solstice. There have been fewer intense geomagnetic storms during the current solar cycle, Solar Cycle 24, than in the previous cycle. This situation changed after mid-June 2015, when one of the largest solar active regions (AR 12371) of Solar Cycle 24 that was located close to the central meridian, produced several coronal mass ejections (CMEs) associated with M-class flares. The impact of these CMEs on the Earth's magnetosphere resulted in a moderate to severe G4-class geomagnetic storm on 22 - 23 June 2015 and a G2 (moderate) geomagnetic storm on 24 June. The G4 solstice storm was the second largest (so far) geomagnetic storm of Cycle 24. We highlight the ground-level observations made with the New-Tupi, Muonca, and the CARPET El Leoncito cosmic-ray detectors that are located within the South Atlantic Anomaly (SAA) region. These observations are studied in correlation with data obtained by space-borne detectors (ACE, GOES, SDO, and SOHO) and other ground-based experiments. The CME designations are taken from the Computer Aided CME Tracking (CACTus) automated catalog. As expected, Forbush decreases (FD) associated with the passing CMEs were recorded by these detectors. We note a peculiar feature linked to a severe geomagnetic storm event. The 21 June 2015 CME 0091 (CACTus CME catalog number) was likely associated with the 22 June summer solstice FD event. The angular width of CME 0091 was very narrow and measured {˜} 56° degrees seen from Earth. In most cases, only CME halos and partial halos lead to severe geomagnetic storms. We perform a cross-check analysis of the FD events detected during the rise phase of Solar Cycle 24, the geomagnetic parameters, and the CACTus CME catalog. Our study suggests that narrow angular-width CMEs that erupt in a westward direction from the Sun-Earth line can lead to moderate and severe geomagnetic storms. We also report on the strong solar proton radiation storm that began on 21 June. We did not find a signal from this SEP at ground level. The details of these observations are presented.

The initiation of coronal mass ejections by newly emerging magnetic flux

NASA Technical Reports Server (NTRS)

Feynman, J.; Martin, S. F.

1995-01-01

We present observational evidence that eruptions of quiescent filaments and associated coronal mass ejections (CMEs) occur as a consequence of the destabilization of large-scale coronal arcades due to interactions between these structures and new and growing active regions. Both statistical and case studies have been carried out. In a case study of a 'bulge' observed by the High-Altitude Observatory Solar Maximum Mission coronagraph, the high-resolution magnetograms from the Big Bear Solar Observatory show newly emerging and rapidly changing flux in the magnetic fields that apparently underlie the bugle. For other case studies and in the statistical work the eruption of major quiescent filaments was taken as a proxy for CME eruption. We have found that two thirds of the quiescent-filament-associated CMEs occurred after substantial amounts of new magnetic flux emerged in the vicinity of the filament. In addition, in a study of all major quiescent filaments and active regions appearing in a 2-month period we found that 17 of the 22 filaments that were associated with new active regions erupted and 26 of the 31 filaments that were not associated with new flux did not erupt. In all cases in which the new flux was oriented favorably for reconnection with the preexisting large-scale coronal arcades; the filament was observed to erupt. The appearance of the new flux in the form of new active regions begins a few days before the eruption and typically is still occurring at the time of the eruption. A CME initiation scenario taking account of these observational results is proposed.

Direct Observations of Magnetic Flux Rope Formation during a Solar Coronal Mass Ejection

NASA Astrophysics Data System (ADS)

Song, H. Q.; Zhang, J.; Chen, Y.; Cheng, X.

2014-09-01

Coronal mass ejections (CMEs) are the most spectacular eruptive phenomena in the solar atmosphere. It is generally accepted that CMEs are the results of eruptions of magnetic flux ropes (MFRs). However, there is heated debate on whether MFRs exist prior to the eruptions or if they are formed during the eruptions. Several coronal signatures, e.g., filaments, coronal cavities, sigmoid structures, and hot channels (or hot blobs), are proposed as MFRs and observed before the eruption, which support the pre-existing MFR scenario. There is almost no reported observation of MFR formation during the eruption. In this Letter, we present an intriguing observation of a solar eruptive event that occurred on 2013 November 21 with the Atmospheric Imaging Assembly on board the Solar Dynamic Observatory, which shows the formation process of the MFR during the eruption in detail. The process began with the expansion of a low-lying coronal arcade, possibly caused by the flare magnetic reconnection underneath. The newly formed ascending loops from below further pushed the arcade upward, stretching the surrounding magnetic field. The arcade and stretched magnetic field lines then curved in just below the arcade vertex, forming an X-point. The field lines near the X-point continued to approach each other and a second magnetic reconnection was induced. It is this high-lying magnetic reconnection that led to the formation and eruption of a hot blob (~10 MK), presumably an MFR, producing a CME. We suggest that two spatially separated magnetic reconnections occurred in this event, which were responsible for producing the flare and the hot blob (CME).

Direct Observations of Magnetic Flux Rope Formation during a Solar Coronal Mass Ejection

NASA Astrophysics Data System (ADS)

Song, H.; Zhang, J.; Chen, Y.; Cheng, X.

2014-12-01

Coronal mass ejections (CMEs) are the most spectacular eruptive phenomena in the solar atmosphere. It is generally accepted that CMEs are results of eruptions of magnetic flux ropes (MFRs). However, a heated debate is on whether MFRs pre-exist before the eruptions or they are formed during the eruptions. Several coronal signatures, e.g., filaments, coronal cavities, sigmoid structures and hot channels (or hot blobs), are proposed as MFRs and observed before the eruption, which support the pre existing MFR scenario. There is almost no reported observation about MFR formation during the eruption. In this presentation, we present an intriguing observation of a solar eruptive event with the Atmospheric Imaging Assembly on board the Solar Dynamic Observatory, which shows a detailed formation process of the MFR during the eruption. The process started with the expansion of a low lying coronal arcade, possibly caused by the flare magnetic reconnection underneath. The newly-formed ascending loops from below further pushed the arcade upward, stretching the surrounding magnetic field. The arcade and stretched magnetic field lines then curved-in just below the arcade vertex, forming an X-point. The field lines near the X-point continued to approach each other and a second magnetic reconnection was induced. It is this high-lying magnetic reconnection that led to the formation and eruption of a hot blob (~ 10 MK), presumably a MFR, producing a CME. We suggest that two spatially-separated magnetic reconnections occurred in this event, responsible for producing the flare and the hot blob (CME), respectively.

Transforming in-situ observations of CME-driven shock accelerated protons into the shock's reference frame.

NASA Astrophysics Data System (ADS)

Robinson, I. M.; Simnett, G. M.

2005-07-01

We examine the solar energetic particle event following solar activity from 14, 15 April 2001 which includes a "bump-on-the-tail" in the proton energy spectra at 0.99 AU from the Sun. We find this population was generated by a CME-driven shock which arrived at 0.99 AU around midnight 18 April. As such this population represents an excellent opportunity to study in isolation, the effects of proton acceleration by the shock. The peak energy of the bump-on-the-tail evolves to progressively lower energies as the shock approaches the observing spacecraft at the inner Lagrange point. Focusing on the evolution of this peak energy we demonstrate a technique which transforms these in-situ spectral observations into a frame of reference co-moving with the shock whilst making allowance for the effects of pitch angle scattering and focusing. The results of this transform suggest the bump-on-the-tail population was not driven by the 15 April activity but was generated or at least modulated by a CME-driven shock which left the Sun on 14 April. The existence of a bump-on-the-tail population is predicted by models in Rice et al. (2003) and Li et al. (2003) which we compare with observations and the results of our analysis in the context of both the 14 April and 15 April CMEs. We find an origin of the bump-on-the-tail at the 14 April CME-driven shock provides better agreement with these modelled predictions although some discrepancy exists as to the shock's ability to accelerate 100 MeV protons. Keywords. Solar physics, astrophysics and astronomy (Energetic particles; Flares and mass ejections) Space plasma physics (Transport processes)

Origin of coronal mass ejection and magnetic cloud: Thermal or magnetic driven?

NASA Technical Reports Server (NTRS)

Zhang, Gong-Liang; Wang, Chi; He, Shuang-Hua

1995-01-01

A fundamental problem in Solar-Terrestrial Physics is the origin of the solar transient plasma output, which includes the coronal mass ejection and its interplanetary manifestation, e.g. the magnetic cloud. The traditional blast wave model resulted from solar thermal pressure impulse has faced with challenge during recent years. In the MHD numerical simulation study of CME, the authors find that the basic feature of the asymmetrical event on 18 August 1980 can be reproduced neither by a thermal pressure nor by a speed increment. Also, the thermal pressure model fails in simulating the interplanetary structure with low thermal pressure and strong magnetic field strength, representative of a typical magnetic cloud. Instead, the numerical simulation results are in favor of the magnetic field expansion as the likely mechanism for both the asymmetrical CME event and magnetic cloud.

Helicity charging and eruption of magnetic flux from the Sun

NASA Technical Reports Server (NTRS)

Rust, David M.; Kumar, A.

1994-01-01

The ejection of helical toroidal fields from the solar atmosphere and their detection in interplanetary space are described. The discovery that solar magnetic fields are twisted and that they are segregated by hemisphere according to their chirality has important implications for the escape process. The roles played by erupting prominences, coronal mass ejections (CME's) and active region (AR) loops in expressing the escape of magnetic flux and helicity are discussed. Sporadic flux escape associated with filament eruptions accounts for less than one-tenth the flux loss. Azimuthal flux loss by CME's could account for more, but the major contributor to flux escape may be AR loop expansion. It is shown how the transfer of magnetic helicity from the sun's interior into emerged loops ('helicity charging') could be the effective driver of solar eruptions and of flux loss from the sun.

Interaction Between Two CMEs During 14 - 15 February 2011 and Their Unusual Radio Signature

NASA Astrophysics Data System (ADS)

Shanmugaraju, A.; Prasanna Subramanian, S.; Vrsnak, Bojan; Ibrahim, M. Syed

2014-12-01

We report a detailed analysis of an interaction between two coronal mass ejections (CMEs) that were observed on 14 - 15 February 2011 and the corresponding radio enhancement, which was similar to the "CME cannibalism" reported by Gopalswamy et al. ( Astrophys. J. 548, L91, 2001). A primary CME, with a mean field-of-view velocity of 669 km s-1 in the Solar and Heliospheric Observatory (SOHO)/ Large Angle Spectrometric Coronagraph (LASCO), was more than as twice as fast as the slow CME preceding it (326 km s-1), which indicates that the two CMEs interacted. A radio-enhancement signature (in the frequency range 1 MHz - 400 kHz) due to the CME interaction was analyzed and interpreted using the CME data from LASCO and from the Solar Terrestrial Relations Observatory (STEREO) HI-1, radio data from Wind/ Radio and Plasma Wave Experiment (WAVES), and employing known electron-density models and kinematic modeling. The following results are obtained: i) The CME interaction occurred around 05:00 - 10:00 UT in a height range 20 - 25 R⊙. An unusual radio signature is observed during the time of interaction in the Wind/WAVES dynamic radio spectrum. ii) The enhancement duration shows that the interaction segment might be wider than 5 R⊙. iii) The shock height estimated using density models for the radio enhancement region is 10 - 30 R⊙. iv) Using kinematic modeling and assuming a completely inelastic collision, the decrease of kinetic energy based on speeds from LASCO data is determined to be 0.77×1023 J, and 3.67×1023 J if speeds from STEREO data are considered. vi) The acceleration, momentum, and force are found to be a=-168 m s-2, I=6.1×1018 kg m s-1, and F=1.7×1015 N, respectively, using STEREO data.

A First for NASA's IRIS: Observing a Gigantic Eruption of Solar Material

NASA Image and Video Library

2014-05-30

Watch a video from this event here: www.flickr.com/photos/gsfc/14118958800/ A coronal mass ejection, or CME, surged off the side of the sun on May 9, 2014, and NASA's newest solar observatory caught it in extraordinary detail. This was the first CME observed by the Interface Region Imaging Spectrograph, or IRIS, which launched in June 2013 to peer into the lowest levels of the sun's atmosphere with better resolution than ever before. Watch the movie to see how a curtain of solar material erupts outward at speeds of 1.5 million miles per hour. Read more: 1.usa.gov/1kp7O4F NASA image use policy. NASA Goddard Space Flight Center enables NASA’s mission through four scientific endeavors: Earth Science, Heliophysics, Solar System Exploration, and Astrophysics. Goddard plays a leading role in NASA’s accomplishments by contributing compelling scientific knowledge to advance the Agency’s mission. Follow us on Twitter Like us on Facebook Find us on Instagram

CME Dynamics Using STEREO and LASCO Observations: The Relative Importance of Lorentz Forces and Solar Wind Drag

NASA Astrophysics Data System (ADS)

Sachdeva, Nishtha; Subramanian, Prasad; Vourlidas, Angelos; Bothmer, Volker

2017-09-01

We seek to quantify the relative contributions of Lorentz forces and aerodynamic drag on the propagation of solar coronal mass ejections (CMEs). We use Graduated Cylindrical Shell (GCS) model fits to a representative set of 38 CMEs observed with the Solar and Heliospheric Observatory (SOHO) and the Solar and Terrestrial Relations Observatory (STEREO) spacecraft. We find that the Lorentz forces generally peak between 1.65 and 2.45 R⊙ for all CMEs. For fast CMEs, Lorentz forces become negligible in comparison to aerodynamic drag as early as 3.5 - 4 R⊙. For slow CMEs, however, they become negligible only by 12 - 50 R⊙. For these slow events, our results suggest that some of the magnetic flux might be expended in CME expansion or heating. In other words, not all of it contributes to the propagation. Our results are expected to be important in building a physical model for understanding the Sun-Earth dynamics of CMEs.

The Mass of a Solar Quiescent Prominence

NASA Technical Reports Server (NTRS)

Low, B. C.; Fong, B.; Fan, Y.

2003-01-01

This paper follows up on our recent paper on the role of prominence mass in the storage of magnetic energy for driving a coronal mass ejection (CME). The previous paper erroneously rejected a set of sheet- prominence solutions, the recovery of which allows for a simple theoretical estimate of the mass of a quiescent prominence. For coronal fields of 5-10 G, these hydromagnetic solutions suggest that a prominence mass of (1-26) x 10(exp 6) g is needed to hold detached magnetic fields of intensity comparable to the coronal fields in an unbounded atmosphere such that the global magnetic field is energetically able to spontaneously open up and still have enough energy to account for the kinetic and gravitational potential energies carried away in a CME. This simple result is discussed in relation to observed prominence magnetic field intensities, densities, and masses, pointing to the relevance of such observations to the question of magnetic energy storage in the solar corona.

Photospheric Magnetic Evolution in the WHI Active Regions

NASA Technical Reports Server (NTRS)

Welsch, B. T.; McTiernan, J. M.; Christe, S.

2012-01-01

Sequences of line-of-sight (LOS) magnetograms recorded by the Michelson Doppler Imager are used to quantitatively characterize photospheric magnetic structure and evolution in three active regions that rotated across the Sun s disk during the Whole Heliosphere Interval (WHI), in an attempt to relate the photospheric magnetic properties of these active regions to flares and coronal mass ejections (CMEs). Several approaches are used in our analysis, on scales ranging from whole active regions, to magnetic features, to supergranular scales, and, finally, to individual pixels. We calculated several parameterizations of magnetic structure and evolution that have previously been associated with flare and CME activity, including total unsigned magnetic flux, magnetic flux near polarity-inversion lines, amount of canceled flux, the "proxy Poynting flux," and helicity flux. To catalog flare events, we used flare lists derived from both GOES and RHESSI observations. By most such measures, AR 10988 should have been the most flare- and CME-productive active region, and AR 10989 the least. Observations, however, were not consistent with this expectation: ARs 10988 and 10989 produced similar numbers of flares, and AR 10989 also produced a few CMEs. These results highlight present limitations of statistics-based flare and CME forecasting tools that rely upon line-of-sight photospheric magnetic data alone.

Association of solar flares with coronal mass ejections accompanied by Deca-Hectometric type II radio burst for two solar cycles 23 and 24

NASA Astrophysics Data System (ADS)

Kharayat, Hema; Prasad, Lalan; Pant, Sumit

2018-05-01

The aim of present study is to find the association of solar flares with coronal mass ejections (CMEs) accompanied by Deca-Hectometric (DH) type II radio burst for the period 1997-2014 (solar cycle 23 and ascending phase of solar cycle 24). We have used a statistical analysis and found that 10-20∘ latitudinal belt of northern region and 80-90∘ longitudinal belts of western region of the sun are more effective for flare-CME accompanied by DH type II radio burst events. M-class flares (52%) are in good association with the CMEs accompanied by DH type II radio burst. Further, we have calculated the flare position and found that most frequent flare site is at the center of the CME span. However, the occurrence probability of all flares is maximum outside the CME span. X-class flare associated CMEs have maximum speed than that of M, C, and B-class flare associated CMEs. We have also found a good correlation between flare position and central position angle of CMEs accompanied by DH type II radio burst.

The Correlation Between Solar Energetic Particle Events and Coronal Mass Ejections

NASA Astrophysics Data System (ADS)

Karelitz, A. M.; Pulkkinen, A.

2012-12-01

Solar energetic particle (SEP) events are a wide scale phenomena that are not only an issue for the 2,000+ costly satellites in the sky but also have negative implications on aviation, and even ground based communication. Forecasting the magnitude and duration of strong SEP events based on preceding events that are often associated with them, such as coronal mass ejections (CMEs) and solar flares, is an important step in future operational space weather as well as research. In order to provide a model connecting SEP and CME characteristics, six specific CMEs between 8/14/2010 and 5/17/12 that met specific qualifications (i.e. earth directed), were chosen and several parameters characterizing the connections were derived. From the derived data, correlations between many of the different parameters were tested. One of the more meaningful correlations that was found is between the peak flux of >10 MeV GOES protons and the speed of the CME. A logarithmic correlation between these two entities is clearly seen with a R^2 value of 0.78 and a fit of y=2.74e.^(003x). For forecasting purposes, the times of the arrival of the SEP event with respect to the evolution of the CME was also recorded. Another possibly meaningful correlation was found between SEP duration and CME speed with R^2 value of 0.56. The identified connections were verified by adding an event that occurred on July 12, 2012. Using the model connecting SEP peak flux and CME speed as produced in this study, space weather forecasters can better predict the magnitude of the SEP event that is a result of an earth directed CME. Doing so will enable precautions to be taken on spacecraft as well as ground based entities that are vulnerable to the high-energy protons. In future work, we plan to perform

Deflected Propagation of CMEs and Its Importance on the CME Arrival Forecasting

NASA Astrophysics Data System (ADS)

Wang, Yuming; Zhuang, Bin; Shen, Chenglong

2017-04-01

As the most important driver of severe space weather, coronal mass ejections (CMEs) and their geoeffectiveness have been studied intensively. Previous statistical studies have shown that not all the front-side halo CMEs are geoeffective, and not all non-recurrent geomagnetic storms can be tracked back to a CME. These phenomena may cause some failed predictions of the geoeffectiveness of CMEs. The recent notable event exhibiting such a failure was on 2015 March 15 when a fast CME originated from the west hemisphere. Space Weather Prediction Center (SWPC) of NOAA initially forecasted that the CME would at most cause a very minor geomagnetic disturbance labeled as G1. However, the CME produced the largest geomagnetic storm so far, at G4 level with the provisional Dst value of -223 nT, in the current solar cycle 24 [e.g., Kataoka et al., 2015; Wang et al., 2016]. Such an unexpected phenomenon naturally raises the first question for the forecasting of the geoeffectiveness of a CME, i.e., whether or not a CME will hit the Earth even though we know the source location and initial kinematic properties of the CME. A full understanding of the propagation trajectory, e.g., the deflected propagation, of a CME from the Sun to 1 AU is the key. With a few cases, we show the importance of the deflection effect in the space weather forecasting. An automated CME arrival forecasting system containing a deflected propagation model is presented.

Mechanisms and Observations of Coronal Dimming for the 2010 August 7 Event

NASA Technical Reports Server (NTRS)

Mason, James P.; Woods, Thomas N.; Caspi, Amir; Thompson, Barbara J.; Hock, Rachel A.

2014-01-01

Coronal dimming of extreme ultraviolet (EUV) emission has the potential to be a useful forecaster of coronal mass ejections (CMEs). As emitting material leaves the corona, a temporary void is left behind which can be observed in spectral images and irradiance measurements. The velocity and mass of the CMEs should impact the character of those observations. However, other physical processes can confuse the observations. We describe these processes and the expected observational signature, with special emphasis placed on the differences. We then apply this understanding to a coronal dimming event with an associated CME that occurred on 2010 August 7. Data from the Solar Dynamics Observatory's (SDO) Atmospheric Imaging Assembly (AIA) and EUV Variability Experiment (EVE) are used for observations of the dimming, while the Solar and Heliospheric Observatory's (SoHO) Large Angle and Spectrometric Coronagraph (LASCO) and the Solar Terrestrial Relations Observatory's (STEREO) COR1 and COR2 are used to obtain velocity and mass estimates for the associated CME. We develop a technique for mitigating temperature effects in coronal dimming from full-disk irradiance measurements taken by EVE. We find that for this event, nearly 100% of the dimming is due to mass loss in the corona.

Mechanisms and observations of coronal dimming for the 201 August 7 event

DOE Office of Scientific and Technical Information (OSTI.GOV)

Mason, James Paul; Woods, T. N.; Caspi, A.

2014-07-01

Coronal dimming of extreme ultraviolet (EUV) emission has the potential to be a useful forecaster of coronal mass ejections (CMEs). As emitting material leaves the corona, a temporary void is left behind which can be observed in spectral images and irradiance measurements. The velocity and mass of the CMEs should impact the character of those observations. However, other physical processes can confuse the observations. We describe these processes and the expected observational signature, with special emphasis placed on the differences. We then apply this understanding to a coronal dimming event with an associated CME that occurred on 2010 August 7.more » Data from the Solar Dynamics Observatory's Atmospheric Imaging Assembly and EUV Variability Experiment (EVE) are used for observations of the dimming, while the Solar and Heliospheric Observatory's Large Angle and Spectrometric Coronagraph and the Solar Terrestrial Relations Observatory's COR1 and COR2 are used to obtain velocity and mass estimates for the associated CME. We develop a technique for mitigating temperature effects in coronal dimming from full-disk irradiance measurements taken by EVE. We find that for this event, nearly 100% of the dimming is due to mass loss in the corona.« less

Future capabilities of CME polarimetric 3D reconstructions with the METIS instrument: A numerical test

NASA Astrophysics Data System (ADS)

Pagano, P.; Bemporad, A.; Mackay, D. H.

2015-10-01

Context. Understanding the 3D structure of coronal mass ejections (CMEs) is crucial for understanding the nature and origin of solar eruptions. However, owing to the optical thinness of the solar corona we can only observe the line of sight integrated emission. As a consequence the resulting projection effects hide the true 3D structure of CMEs. To derive information on the 3D structure of CMEs from white-light (total and polarized brightness) images, the polarization ratio technique is widely used. The soon-to-be-launched METIS coronagraph on board Solar Orbiter will use this technique to produce new polarimetric images. Aims: This work considers the application of the polarization ratio technique to synthetic CME observations from METIS. In particular we determine the accuracy at which the position of the centre of mass, direction and speed of propagation, and the column density of the CME can be determined along the line of sight. Methods: We perform a 3D MHD simulation of a flux rope ejection where a CME is produced. From the simulation we (i) synthesize the corresponding METIS white-light (total and polarized brightness) images and (ii) apply the polarization ratio technique to these synthesized images and compare the results with the known density distribution from the MHD simulation. In addition, we use recent results that consider how the position of a single blob of plasma is measured depending on its projected position in the plane of the sky. From this we can interpret the results of the polarization ratio technique and give an estimation of the error associated with derived parameters. Results: We find that the polarization ratio technique reproduces with high accuracy the position of the centre of mass along the line of sight. However, some errors are inherently associated with this determination. The polarization ratio technique also allows information to be derived on the real 3D direction of propagation of the CME. The determination of this is of fundamental importance for future space weather forecasting. In addition, we find that the column density derived from white-light images is accurate and we propose an improved technique where the combined use of the polarization ratio technique and white-light images minimizes the error in the estimation of column densities. Moreover, by applying the comparison to a set of snapshots of the simulation we can also assess the errors related to the trajectory and the expansion of the CME. Conclusions: Our method allows us to thoroughly test the performance of the polarization ratio technique and allows a determination of the errors associated with it, which means that it can be used to quantify the results from the analysis of the forthcoming METIS observations in white light (total and polarized brightness). Finally, we describe a satellite observing configuration relative to the Earth that can allow the technique to be efficiently used for space weather predictions. A movie attached to Fig. 15 is available in electronic form at http://www.aanda.org

Understanding the evolution and propagation of coronal mass ejections and associated plasma sheaths in interplanetary space

NASA Astrophysics Data System (ADS)

Hess, Phillip

A Coronal Mass Ejection (CME) is an eruption of magnetized plasma from the Coronaof the Sun. Understanding the physical process of CMEs is a fundamental challenge in solarphysics, and is also of increasing importance for our technological society. CMEs are knownthe main driver of space weather that has adverse effects on satellites, power grids, com-munication and navigation systems and astronauts. Understanding and predicting CMEs is still in the early stage of research. In this dissertation, improved observational methods and advanced theoretical analysis are used to study CMEs. Unlike many studies in the past that treat CMEs as a single object, this study divides aCME into two separate components: the ejecta from the corona and the sheath region thatis the ambient plasma compressed by the shock/wave running ahead of the ejecta; bothstructures are geo-effective but evolve differently. Stereoscopic observations from multiplespacecraft, including STEREO and SOHO, are combined to provide a three-dimensionalgeometric reconstruction of the structures studied. True distances and velocities of CMEs are accurately determined, free of projection effects, and with continuous tracking from the low corona to 1 AU.To understand the kinematic evolution of CMEs, an advanced drag-based model (DBM) is proposed, with several improvements to the original DBM model. The new model varies the drag parameter with distance; the variation is constrained by thenecessary conservation of physical parameters. Second, the deviation of CME-nose from the Sun-Earth-line is taken into account. Third, the geometric correction of the shape of the ejecta front is considered, based on the assumption that the true front is a flattened croissant-shaped flux rope front. These improvements of the DBM model provide a framework for using measurement data to make accurate prediction of the arrival times of CME ejecta and sheaths. Using a set of seven events to test the model, it is found that the evolution of the ejecta front can be accurately predicted, with a slightly poorer performance on the sheath front. To improve the sheath prediction, the standoff-distance between the ejecta and the sheath front is used to model the evolution. The predicted arrivals of both the sheath and ejecta fronts at Earth are determined to within an average 3.5 hours and 1.5 hours of observed arrivals,respectively. These prediction errors show a significant improvement over predictions made by other researches. The results of this dissertation study demonstrate that accurate space weather prediction is possible, and also reveals what observations are needed in the future for realistic operational space weather prediction.

Magnificent CME Erupts on the Sun with Earth to Scale

NASA Image and Video Library

2017-12-08

On August 31, 2012 a long filament of solar material that had been hovering in the sun's atmosphere, the corona, erupted out into space at 4:36 p.m. EDT. The coronal mass ejection, or CME, traveled at over 900 miles per second. The CME did not travel directly toward Earth, but did connect with Earth's magnetic environment, or magnetosphere, causing aurora to appear on the night of Monday, September 3. The image above includes an image of Earth to show the size of the CME compared to the size of Earth. Credit: NASA/GSFC/SDO NASA image use policy. NASA Goddard Space Flight Center enables NASA’s mission through four scientific endeavors: Earth Science, Heliophysics, Solar System Exploration, and Astrophysics. Goddard plays a leading role in NASA’s accomplishments by contributing compelling scientific knowledge to advance the Agency’s mission. Follow us on Twitter Like us on Facebook Find us on Instagram

Predicting the magnetic vectors within coronal mass ejections arriving at Earth: 2. Geomagnetic response

NASA Astrophysics Data System (ADS)

Savani, N. P.; Vourlidas, A.; Richardson, I. G.; Szabo, A.; Thompson, B. J.; Pulkkinen, A.; Mays, M. L.; Nieves-Chinchilla, T.; Bothmer, V.

2017-02-01

This is a companion to Savani et al. (2015) that discussed how a first-order prediction of the internal magnetic field of a coronal mass ejection (CME) may be made from observations of its initial state at the Sun for space weather forecasting purposes (Bothmer-Schwenn scheme (BSS) model). For eight CME events, we investigate how uncertainties in their predicted magnetic structure influence predictions of the geomagnetic activity. We use an empirical relationship between the solar wind plasma drivers and Kp index together with the inferred magnetic vectors, to make a prediction of the time variation of Kp (Kp(BSS)). We find a 2σ uncertainty range on the magnetic field magnitude (|B|) provides a practical and convenient solution for predicting the uncertainty in geomagnetic storm strength. We also find the estimated CME velocity is a major source of error in the predicted maximum Kp. The time variation of Kp(BSS) is important for predicting periods of enhanced and maximum geomagnetic activity, driven by southerly directed magnetic fields, and periods of lower activity driven by northerly directed magnetic field. We compare the skill score of our model to a number of other forecasting models, including the NOAA/Space Weather Prediction Center (SWPC) and Community Coordinated Modeling Center (CCMC)/SWRC estimates. The BSS model was the most unbiased prediction model, while the other models predominately tended to significantly overforecast. The True skill score of the BSS prediction model (TSS = 0.43 ± 0.06) exceeds the results of two baseline models and the NOAA/SWPC forecast. The BSS model prediction performed equally with CCMC/SWRC predictions while demonstrating a lower uncertainty.

Far-Side Halo Outburst

NASA Image and Video Library

2017-12-08

The Sun blew out a powerful coronal mass ejection (CME) from just around the edge of the Sun (Oct. 14, 2014). The particle cloud expanded around all the Sun in a rough circle, hence the name 'halo' CME. This event was also associated with a fairly strong flare. The active region that was the source of these events is just rotating into view. Then, we can better observe its size and structure. The bright object to the right and just above the Sun is Venus now on the far side of the Sun. Credit: NASA/ESA/SOHO NASA image use policy. NASA Goddard Space Flight Center enables NASA’s mission through four scientific endeavors: Earth Science, Heliophysics, Solar System Exploration, and Astrophysics. Goddard plays a leading role in NASA’s accomplishments by contributing compelling scientific knowledge to advance the Agency’s mission. Follow us on Twitter Like us on Facebook Find us on Instagram

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kahler, S. W., E-mail: stephen.kahler@kirtland.af.mil

Prompt onsets and short rise times to peak intensities Ip have been noted in a few solar energetic (E > 10 MeV) particle (SEP) events from far behind (≥25°) the west limb. We discuss 15 archival and recent examples of these prompt events, giving their source longitudes, onset and rise times, and associated coronal mass ejection (CME) speeds. Their timescales and CME speeds are not exceptional in comparison with a larger set of SEP events from behind the west limb. A further statistical comparison of observed timescales of SEP events from behind the west limb with events similarly poorly magneticallymore » connected to the eastern hemisphere (EH) shows the longer timescales of the latter group. We interpret this result in terms of a difference between SEP production at parallel shocks on the eastern flanks of western backside events and at perpendicular shocks on the western flanks of EH events.« less

Geometrical Properties of Coronal Mass Ejections

NASA Astrophysics Data System (ADS)

Cremades, Hebe; Bothmer, Volker

Based on the SOHO/LASCO dataset, a collection of "structured" coronal mass ejections (CMEs) has been compiled within the period 1996-2002, in order to analyze their three-dimensional configuration. These CME events exhibit white-light fine structures, likely indicative of their possible 3D topology. From a detailed investigation of the associated low coronal and photospheric source regions, a generic scheme has been deduced, which considers the white-light topology of a CME projected in the plane of the sky as being primarily dependent on the orientation and position of the source region's neutral line on the solar disk. The obtained results imply that structured CMEs are essentially organized along a symmetry axis, in a cylindrical manner. The measured dimensions of the cylinder's base and length yield a ratio of 1.6. These CMEs seem to be better approximated by elliptic cones, rather than by the classical ice cream cone, characterized by a circular cross section.

Anomalous Expansion of Coronal Mass Ejections During Solar Cycle 24 and Its Space Weather Implications

NASA Technical Reports Server (NTRS)

Gopalswamy, Nat; Akiyama, Sachiko; Yashiro, Seiji; Xie, Hong; Makela, Pertti; Michalek, Grzegorz

2014-01-01

The familiar correlation between the speed and angular width of coronal mass ejections (CMEs) is also found in solar cycle 24, but the regression line has a larger slope: for a given CME speed, cycle 24 CMEs are significantly wider than those in cycle 23. The slope change indicates a significant change in the physical state of the heliosphere, due to the weak solar activity. The total pressure in the heliosphere (magnetic + plasma) is reduced by approximately 40%, which leads to the anomalous expansion of CMEs explaining the increased slope. The excess CME expansion contributes to the diminished effectiveness of CMEs in producing magnetic storms during cycle 24, both because the magnetic content of the CMEs is diluted and also because of the weaker ambient fields. The reduced magnetic field in the heliosphere may contribute to the lack of solar energetic particles accelerated to very high energies during this cycle.

Challenging Some Contemporary Views of Coronal Mass Ejections. II. The Case for Absent Filaments

NASA Astrophysics Data System (ADS)

Howard, T. A.; DeForest, C. E.; Schneck, U. G.; Alden, C. R.

2017-01-01

When a coronal mass ejection (CME) appears in a coronagraph it often exhibits three parts. This “classic” three-part configuration consists of a bright leading edge, a dark circular- or teardrop-shaped cavity, and a bright core within the cavity. It is generally accepted that these are manifestations of coronal plasma pileup, the driving magnetic flux rope, and the associated eruptive filament, respectively. The latter has become accepted by the community since coronagraph CMEs have been commonly associated with eruptive filaments for over 40 years. In this second part of our series challenging views on CMEs, we present the case that the inner core of the three-part coronagraph CME may not be, and in the most common cases is not, a filament. We present our case in the form of four exhibits showing that most of the CMEs in a broad survey are not associated with an eruptive filament at the Sun, and that the cores of those CMEs that are filament-associated do not geometrically resemble or consist of material from the associated filament. We conclude with a discussion on the possible causes of the bright CME core and what happens to the filament material postlaunch. We discuss how the CME core could arise spontaneously from the eruption of a flux rope from the Sun, or could be the result of a mathematical caustic produced by the geometric projection of a twisted flux rope.

CHALLENGING SOME CONTEMPORARY VIEWS OF CORONAL MASS EJECTIONS. II. THE CASE FOR ABSENT FILAMENTS

DOE Office of Scientific and Technical Information (OSTI.GOV)

Howard, T. A.; DeForest, C. E.; Schneck, U. G.

2017-01-01

When a coronal mass ejection (CME) appears in a coronagraph it often exhibits three parts. This “classic” three-part configuration consists of a bright leading edge, a dark circular- or teardrop-shaped cavity, and a bright core within the cavity. It is generally accepted that these are manifestations of coronal plasma pileup, the driving magnetic flux rope, and the associated eruptive filament, respectively. The latter has become accepted by the community since coronagraph CMEs have been commonly associated with eruptive filaments for over 40 years. In this second part of our series challenging views on CMEs, we present the case that themore » inner core of the three-part coronagraph CME may not be, and in the most common cases is not, a filament. We present our case in the form of four exhibits showing that most of the CMEs in a broad survey are not associated with an eruptive filament at the Sun, and that the cores of those CMEs that are filament-associated do not geometrically resemble or consist of material from the associated filament. We conclude with a discussion on the possible causes of the bright CME core and what happens to the filament material postlaunch. We discuss how the CME core could arise spontaneously from the eruption of a flux rope from the Sun, or could be the result of a mathematical caustic produced by the geometric projection of a twisted flux rope.« less

WAITING TIMES OF QUASI-HOMOLOGOUS CORONAL MASS EJECTIONS FROM SUPER ACTIVE REGIONS

DOE Office of Scientific and Technical Information (OSTI.GOV)

Wang Yuming; Liu Lijuan; Shen Chenglong

Why and how do some active regions (ARs) frequently produce coronal mass ejections (CMEs)? These are key questions for deepening our understanding of the mechanisms and processes of energy accumulation and sudden release in ARs and for improving our space weather prediction capability. Although some case studies have been performed, these questions are still far from fully answered. These issues are now being addressed statistically through an investigation of the waiting times of quasi-homologous CMEs from super ARs in solar cycle 23. It is found that the waiting times of quasi-homologous CMEs have a two-component distribution with a separation atmore » about 18 hr. The first component is a Gaussian-like distribution with a peak at about 7 hr, which indicates a tight physical connection between these quasi-homologous CMEs. The likelihood of two or more occurrences of CMEs faster than 1200 km s{sup -1} from the same AR within 18 hr is about 20%. Furthermore, the correlation analysis among CME waiting times, CME speeds, and CME occurrence rates reveals that these quantities are independent of each other, suggesting that the perturbation by preceding CMEs rather than free energy input is the direct cause of quasi-homologous CMEs. The peak waiting time of 7 hr probably characterizes the timescale of the growth of the instabilities triggered by preceding CMEs. This study uncovers some clues from a statistical perspective for us to understand quasi-homologous CMEs as well as CME-rich ARs.« less

Interaction of Two Filaments in a Long Filament Channel Associated with Twin Coronal Mass Ejections

DOE Office of Scientific and Technical Information (OSTI.GOV)

Zheng, Ruisheng; Chen, Yao; Wang, Bing

Using the high-quality observations of the Solar Dynamics Observatory , we present the interaction of two filaments (F1 and F2) in a long filament channel associated with twin coronal mass ejections (CMEs) on 2016 January 26. Before the eruption, a sequence of rapid cancellation and emergence of the magnetic flux has been observed, which likely triggered the ascending of the west filament (F1). The east footpoints of rising F1 moved toward the east far end of the filament channel, accompanied by post-eruption loops and flare ribbons. This likely indicated a large-scale eruption involving the long filament channel, which resulted frommore » the interaction between F1 and the east filament (F2). Some bright plasma flew over F2, and F2 stayed at rest during the eruption, likely due to the confinement of its overlying lower magnetic field. Interestingly, the impulsive F1 pushed its overlying magnetic arcades to form the first CME, and F1 finally evolved into the second CME after the collision with the nearby coronal hole. We suggest that the interaction of F1 and the overlying magnetic field of F2 led to the merging reconnection that forms a longer eruptive filament loop. Our results also provide a possible picture of the origin of twin CMEs and show that the large-scale magnetic topology of the coronal hole is important for the eventual propagation direction of CMEs.« less

Halo Coronal Mass Ejections during Solar Cycle 24: reconstruction of the global scenario and geoeffectiveness

NASA Astrophysics Data System (ADS)

Scolini, Camilla; Messerotti, Mauro; Poedts, Stefaan; Rodriguez, Luciano

2018-02-01

In this study we present a statistical analysis of 53 fast Earth-directed halo CMEs observed by the SOHO/LASCO instrument during the period Jan. 2009-Sep. 2015, and we use this CME sample to test the capabilities of a Sun-to-Earth prediction scheme for CME geoeffectiveness. First, we investigate the CME association with other solar activity features by means of multi-instrument observations of the solar magnetic and plasma properties. Second, using coronagraphic images to derive the CME kinematical properties at 0.1 AU, we propagate the events to 1 AU by means of the WSA-ENLIL+Cone model. Simulation results at Earth are compared with in-situ observations at L1. By applying the pressure balance condition at the magnetopause and a solar wind-Kp index coupling function, we estimate the expected magnetospheric compression and geomagnetic activity level, and compare them with global data records. The analysis indicates that 82% of the CMEs arrived at Earth in the next 4 days. Almost the totality of them compressed the magnetopause below geosynchronous orbits and triggered a geomagnetic storm. Complex sunspot-rich active regions associated with energetic flares result the most favourable configurations from which geoeffective CMEs originate. The analysis of related SEP events shows that 74% of the CMEs associated with major SEPs were geoeffective. Moreover, the SEP production is enhanced in the case of fast and interacting CMEs. In this work we present a first attempt at applying a Sun-to-Earth geoeffectiveness prediction scheme - based on 3D simulations and solar wind-geomagnetic activity coupling functions - to a statistical set of potentially geoeffective halo CMEs. The results of the prediction scheme are in good agreement with geomagnetic activity data records, although further studies performing a fine-tuning of such scheme are needed.

Radio-loud CMEs from the Disk Center Lacking Shocks at 1 AU

NASA Technical Reports Server (NTRS)

Gopalswamy, N; Makela, P.; Akiyama, S.; Yashiro, S.; Xie, H.; MacDowall, R. J.; Kaiser, M. L.

2013-01-01

A coronal mass ejection (CME) associated with a type II burst and originating close to the center of the solar disk typically results in a shock at Earth in 2-3 days and hence can be used to predict shock arrival at Earth. However, a significant fraction (about 28%) of such CMEs producing type II bursts were not associated with shocks at Earth. We examined a set of 21 type II bursts observed by the Wind/WAVES experiment at decameter-hectometric (DH) wavelengths that had CME sources very close to the disk center (within a central meridian distance of 30 degrees), but did not have a shock at Earth. We find that the near-Sun speeds of these CMEs average to 644 km/s, only slightly higher than the average speed of CMEs associated with radio-quiet shocks. However, the fraction of halo CMEs is only 30%, compared to 54% for the radio-quiet shocks and 91% for all radio-loud shocks. We conclude that the disk-center radio-loud CMEs with no shocks at 1 AU are generally of lower energy and they drive shocks only close to the Sun and dissipate before arriving at Earth. There is also evidence for other possible processes that lead to the lack of shock at 1 AU: (i) overtaking CME shocks merge and one observes a single shock at Earth, and (ii) deflection by nearby coronal holes can push the shocks away from the Sun-Earth line, such that Earth misses these shocks. The probability of observing a shock at 1 AU increases rapidly above 60% when the CME speed exceeds 1000 km/s and when the type II bursts propagate to frequencies below 1 MHz.

Prediction of Coronal Mass Ejections From Vector Magnetograms: Quantitative Measures as Predictors

NASA Technical Reports Server (NTRS)

Falconer, D. A.; Moore, R. L.; Gary, G. A.; Rose, M. Franklin (Technical Monitor)

2001-01-01

We derived two quantitative measures of an active region's global nonpotentiality from the region's vector magnetogram, 1) the net current (I(sub N)), and 2) the length of strong-shear, strong-field main neutral line (Lss), and used these two measures in a pilot study of the CME productivity of 4 active regions. We compared the global nonpotentiality measures to the active regions' CME productivity determined from GOES and Yohkoh/SXT observations. We found that two of the active regions were highly globally nonpotential and were CME productive, while the other two active regions had little global nonpotentiality and produced no CMEs. At the Fall 2000 AGU, we reported on an expanded study (12 active regions and 17 magnetograms) in which we evaluated four quantitative global measures of an active region's magnetic field and compared these measures with the CME productivity. The four global measures (all derived from MSFC vector magnetograms) included our two previous measures (I(sub N) and L(sub ss)) as well as two new ones, the total magnetic flux (PHI) (a measure of an active region's size), and the normalized twist (alpha (bar)= muIN/PHI). We found that the three quantitative measures of global nonpotentiality (I(sub N), L(sub ss), alpha (bar)) were all well correlated (greater than 99% confidence level) with an active region's CME productivity within plus or minus 2 days of the day of the magnetogram. We will now report on our findings of how good our quantitative measures are as predictors of active-region CME productivity, using only CMEs that occurred after the magnetogram. We report the preliminary skill test of these quantitative measures as predictors. We compare the CME prediction success of our quantitative measures to the CME prediction success based on an active region's past CME productivity. We examine the cases of the handful of false positive and false negatives to look for improvements to our predictors. This work is funded by NSF through the Space Weather Program and by NASA through the Solar Physics Supporting Research and Technology Program.

Prediction of Coronal Mass Ejections from Vector Magnetograms: Quantitative Measures as Predictors

NASA Astrophysics Data System (ADS)

Falconer, D. A.; Moore, R. L.; Gary, G. A.

2001-05-01

In a pilot study of 4 active regions (Falconer, D.A. 2001, JGR, in press), we derived two quantitative measures of an active region's global nonpotentiality from the region's vector magnetogram, 1) the net current (IN), and 2) the length of the strong-shear, strong-field main neutral line (LSS), and used these two measures of the CME productivity of the active regions. We compared the global nonpotentiality measures to the active regions' CME productivity determined from GOES and Yohkoh/SXT observations. We found that two of the active regions were highly globally nonpotential and were CME productive, while the other two active regions had little global nonpotentiality and produced no CMEs. At the Fall 2000 AGU (Falconer, Moore, & Gary, 2000, EOS 81, 48 F998), we reported on an expanded study (12 active regions and 17 magnetograms) in which we evaluated four quantitative global measures of an active region's magnetic field and compared these measures with the CME productivity. The four global measures (all derived from MSFC vector magnetograms) included our two previous measures (IN and LSS) as well as two new ones, the total magnetic flux (Φ ) (a measure of an active region's size), and the normalized twist (α =μ IN/Φ ). We found that the three measures of global nonpotentiality (IN, LSS, α ) were all well correlated (>99% confidence level) with an active region's CME productivity within (2 days of the day of the magnetogram. We will now report on our findings of how good our quantitative measures are as predictors of active-region CME productivity, using only CMEs that occurred after the magnetogram. We report the preliminary skill test of these quantitative measures as predictors. We compare the CME prediction success of our quantitative measures to the CME prediction success based on an active region's past CME productivity. We examine the cases of the handful of false positive and false negatives to look for improvements to our predictors. This work is funded by NSF through the Space Weather Program and by NASA through the Solar Physics Supporting Research and Technology Program.

Empirical Modeling of ICMEs Using ACE/SWICS Ionic Distributions

NASA Astrophysics Data System (ADS)

Rivera, Y.; Landi, E.; Lepri, S. T.; Gilbert, J. A.

2017-12-01

Coronal Mass Ejections (CMEs) are some of the largest, most energetic events in the solar system releasing an immense amount of plasma and magnetic field into the Heliosphere. The Earth-bound plasma plays a large role in space weather, causing geomagnetic storms that can damage space and ground based instrumentation. As a CME is released, the plasma experiences heating, expansion and acceleration; however, the physical mechanism supplying the heating as it lifts out of the corona still remains uncertain. From previous work we know the ionic composition of solar ejecta undergoes a gradual transition to a state where ionization and recombination processes become ineffective rendering the ionic composition static along its trajectory. This property makes them a good indicator of thermal conditions in the corona, where the CME plasma likely receives most of its heating. We model this so-called `freeze-in' process in Earth-directed CMEs using an ionization code to empirically determine the electron temperature, density and bulk velocity. `Frozen-in' ions from an ensemble of independently modeled plasmas within the CME are added together to fit the full range of observational ionic abundances collected by ACE/SWICS during ICME events. The models derived using this method are used to estimate the CME energy budget to determine a heating rate used to compare with a variety of heating mechanisms that can sustain the required heating with a compatible timescale.

The Major Geoeffective Solar Eruptions of 2012 March 7: Comprehensive Sun-to-Earth Analysis

NASA Astrophysics Data System (ADS)

Patsourakos, S.; Georgoulis, M. K.; Vourlidas, A.; Nindos, A.; Sarris, T.; Anagnostopoulos, G.; Anastasiadis, A.; Chintzoglou, G.; Daglis, I. A.; Gontikakis, C.; Hatzigeorgiu, N.; Iliopoulos, A. C.; Katsavrias, C.; Kouloumvakos, A.; Moraitis, K.; Nieves-Chinchilla, T.; Pavlos, G.; Sarafopoulos, D.; Syntelis, P.; Tsironis, C.; Tziotziou, K.; Vogiatzis, I. I.; Balasis, G.; Georgiou, M.; Karakatsanis, L. P.; Malandraki, O. E.; Papadimitriou, C.; Odstrčil, D.; Pavlos, E. G.; Podlachikova, O.; Sandberg, I.; Turner, D. L.; Xenakis, M. N.; Sarris, E.; Tsinganos, K.; Vlahos, L.

2016-01-01

During the interval 2012 March 7-11 the geospace experienced a barrage of intense space weather phenomena including the second largest geomagnetic storm of solar cycle 24 so far. Significant ultra-low-frequency wave enhancements and relativistic-electron dropouts in the radiation belts, as well as strong energetic-electron injection events in the magnetosphere were observed. These phenomena were ultimately associated with two ultra-fast (>2000 km s-1) coronal mass ejections (CMEs), linked to two X-class flares launched on early 2012 March 7. Given that both powerful events originated from solar active region NOAA 11429 and their onsets were separated by less than an hour, the analysis of the two events and the determination of solar causes and geospace effects are rather challenging. Using satellite data from a flotilla of solar, heliospheric and magnetospheric missions a synergistic Sun-to-Earth study of diverse observational solar, interplanetary and magnetospheric data sets was performed. It was found that only the second CME was Earth-directed. Using a novel method, we estimated its near-Sun magnetic field at 13 R⊙ to be in the range [0.01, 0.16] G. Steep radial fall-offs of the near-Sun CME magnetic field are required to match the magnetic fields of the corresponding interplanetary CME (ICME) at 1 AU. Perturbed upstream solar-wind conditions, as resulting from the shock associated with the Earth-directed CME, offer a decent description of its kinematics. The magnetospheric compression caused by the arrival at 1 AU of the shock associated with the ICME was a key factor for radiation-belt dynamics.

Pseudo-automatic Determination of Coronal Mass Ejections’ Kinematics in 3D

DOE Office of Scientific and Technical Information (OSTI.GOV)

Braga, Carlos Roberto; Dal Lago, Alisson; Echer, Ezequiel

Coronal mass ejection (CME) events are among the main drivers of geomagnetic disturbances, and hence play a central role in the Sun–Earth system. Their monitoring and, in particular, the determination of their speed and direction of propagation are key issues for the forecasting of space weather near to Earth. We have implemented a method to track CME events in three dimensions by combining triangulation and tie-pointing analysis with a supervised computer vision algorithm. This novel approach does not rely on any geometric constraint, and eliminates the need for visual identification of the CME boundaries. We applied our method to 17more » CME events observed simultaneously by the twin Solar Terrestrial Relations Observatory ( STEREO ) COR2 coronagraph imagers from 2008 December to 2011 November in order to obtain their 3D kinematical characterization (i.e., the velocity vector) along with their morphological properties. About ten of these events have already been analyzed using other methodologies. In these cases, we carried out a thorough comparison with our results and found that, in spite of the different nature and spatial coverage range of the other methods with respect to CORSET3D, the majority of the results agree. We found, however, that three events exhibited discrepancies in the magnitude of the velocity vector, four in the longitudinal direction of propagation, and in only one case was there a discrepancy in latitude. The discrepancies appeared in those cases where quasi-simultaneous, quasi-co-located events were observed in the coronagraphs’ fields of view.« less

Imaging Prominence Eruptions out to 1 AU

NASA Astrophysics Data System (ADS)

Wood, Brian E.; Howard, Russell A.; Linton, Mark G.

2016-01-01

Views of two bright prominence eruptions trackable all the way to 1 AU are here presented, using the heliospheric imagers on the Solar TErrestrial RElations Observatory (STEREO) spacecraft. The two events first erupted from the Sun on 2011 June 7 and 2012 August 31, respectively. Only these two examples of clear prominence eruptions observable this far from the Sun could be found in the STEREO image database, emphasizing the rarity of prominence eruptions this persistently bright. For the 2011 June event, a time-dependent 3D reconstruction of the prominence structure is made using point-by-point triangulation. This is not possible for the August event due to a poor viewing geometry. Unlike the coronal mass ejection (CME) that accompanies it, the 2011 June prominence exhibits little deceleration from the Sun to 1 AU, as a consequence moving upwards within the CME. This demonstrates that prominences are not necessarily tied to the CME's magnetic structure far from the Sun. A mathematical framework is developed for describing the degree of self-similarity for the prominence's expansion away from the Sun. This analysis suggests only modest deviations from self-similar expansion, but close to the Sun the prominence expands radially somewhat more rapidly than self-similarity would predict.

Earth-Directed X-Class Flare and CME

NASA Image and Video Library

2014-09-15

An active region just about squarely facing Earth erupted with an X 1.6 flare (largest class) as well as a coronal mass ejection (CME) on Sept. 10-11, 2014. This event featured both a long flare decay time and a storm of electrically charged, energetic particles. The particles can be seen as bright white specks scattering across the frames. The coronagraph movie shows the cloud of particles expanding in all directions as if it were creating a halo around the Sun. Data shows that the CME was heading towards Earth that could generate strong aurora displays several days later. In coronagraph images the Sun (represented by the small white circle in the center) is blocked by an occulting disk so that we can observe faint features in the corona and beyond. Credit: NASA/ESA/Goddard/SOHO NASA image use policy. NASA Goddard Space Flight Center enables NASA’s mission through four scientific endeavors: Earth Science, Heliophysics, Solar System Exploration, and Astrophysics. Goddard plays a leading role in NASA’s accomplishments by contributing compelling scientific knowledge to advance the Agency’s mission. Follow us on Twitter Like us on Facebook Find us on Instagram

The CME Flare Arcade and the Width of the CME in the Outer Corona

NASA Technical Reports Server (NTRS)

Moore, Ron; Falconer, David; Sterling, Alphonse

2008-01-01

Moore, Sterling, & Suess (2007, ApJ, 668, 1221) present evidence that (1) a CME is typically a magnetic bubble, a low-beta gplasmoid with legs h having roughly the 3D shape of a light bulb, and (2) in the outer corona the CME plasmoid is in lateral pressure equilibrium with the ambient magnetic field. They present three CMEs observed by SOHO/LASCO, each from a very different source located near the limb. One of these CMEs came from a compact ejective eruption from a small part of a sunspot active region, another came from a large quiet-region filament eruption, and the third CME, an extremely large and fast one, was produced in tandem with an X20 flare arcade that was centered on a huge delta sunspot. Each of these CMEs had more or less the classic lightbulb silhouette and attained a constant heliocentric angular width in the outer corona. This indicates that the CME plasmoid attained lateral magnetic pressure balance with the ambient radial magnetic field in the outer corona. This lateral pressure balance, together with the standard scenario for CME production by the eruption of a sheared-core magnetic arcade, yields the following simple estimate of the strength B(sub Flare) of the magnetic field in the flare arcade produced together with the CME: B(sub Flare) 1.4(theta CME/theta Flare)sup 2 G, where theta (sub CME) is the heliocentric angular width of the CME plasmoid in the outer corona and theta (sub Flare) is the heliocentric angular width of the full-grown flare arcade. Conversely, theta (sub CME) approximately equal to (R(sub Sun)sup -1(phi(sub Flare)/1.4)sup 1/2 radians, where Flare is the magnetic flux covered by the full-grown flare arcade. In addition to presenting the three CMEs of Moore, Sterling, & Suess (2007) and their agreement with this relation between CME and Flare, we present a further empirical test of this relation. For CMEs that erupt from active regions, the co-produced flare arcade seldom if ever covers the entire active region: if AR is the total magnetic flux of the active region, Flare . AR, and we predict that CME. (R(sub Sun))sup -1(theta AR/1.4)sup 1/2 radians. For a random sample of 31 CMEs that erupted from active regions within 30 of the limb, for each CME we have measured CME from LASCO/C3 and have measured AR from a SOHO/MDI magnetogram of the source active region when it was within 30 of disk center. We find that each CME obeys the above predicted inequality, none having width greater than half of the upper bound given by theta(sub AR). Thus, an active region's magnetic flux content, together with its location on the solar disk, largely determines whether the active region can possibly produce a CME that is wide enough to intercept the Earth.

Observation and Interpretation of Energetic Neutral Hydrogen Atoms from the December 5, 2006 Solar Event

NASA Technical Reports Server (NTRS)

Mewaldt, R. A.; Leske, R. A.; Stone, E. C.; Barghouty, A. F.; Shih, A. Y.; von Rosenvinge, T. T.; Labrador, A. W.; Cohen, C. M. S.; Cummings, A. C.; Cummings, A. C.

2009-01-01

We report the first observations of energetic neutral atoms (ENAs) from a solar flare/coronal mass ejection event. The observations were made during the December 5, 2006 X9 solar flare, located at E79, by the Low Energy Telescopes (LETs) on the STEREO A and B spacecraft. Within 1-2 hours of the flare onset, both LETs observed a sudden burst of 1.6 to 15 MeV protons arriving hours before the onset of the main solar energetic particle (SEP) event at Earth. More than 70% of these particles arrived from a longitude within +-10 degrees of the Sun. The derived emission profile at the Sun lasted for more than an hour and had a profile remarkably similar to the GOES soft X-ray profile. The observed arrival directions and energy spectrum argue strongly that the particle events <5 MeV were due to energetic neutral hydrogen atoms that were stripped of their electrons upon entering the LET sensor. To our knowledge, this is the first reported observation of ENA emission from a solar flare/coronal mass ejection. We discuss possible origins for the production of ENAs in solar events, including charge-transfer reactions involving both flare and shock-accelerated protons. Assuming isotropic emission, we find that 2 x 10E28 ENAs escaped from the Sun in the upper hemisphere. Based on the 2.2 MeV gamma-ray emission observed by RHESSI in this event, and using measured and theoretical cross sections, we estimate that 3 x 10E31 ENAs with 1.8 - 5 MeV could be produced by protons accelerated in the flare. CME-driven shock acceleration is also a possible ENA source, but unfortunately there were no CME observations available from this event. Taking into account ENA losses, we conclude that the observed ENAs were most likely produced in the high corona at heliocentric distances 1.6 solar radii.

Identification of prominence ejecta by the proton distribution function and magnetic fine structure in interplanetary coronal mass ejections in the inner heliosphere

NASA Astrophysics Data System (ADS)

Yao, Shuo; Marsch, Eckart; Tu, Chuan-Yi; Schwenn, Rainer

2010-05-01

This work presents in situ solar wind observations of three magnetic clouds (MCs) that contain cold high-density material when Helios 2 was located at 0.3 AU on 9 May 1979, 0.5 AU on 30 March 1976, and 0.7 AU on 24 December 1978. In the cold high-density regions embedded in the interplanetary coronal mass ejections we find (1) that the number density of protons is higher than in other regions inside the magnetic cloud, (2) the possible existence of He+, (3) that the thermal velocity distribution functions are more isotropic and appear to be colder than in the other regions of the MC, and the proton temperature is lower than that of the ambient plasma, and (4) that the associated magnetic field configuration can for all three MC events be identified as a flux rope. This cold high-density region is located at the polarity inversion line in the center of the bipolar structure of the MC magnetic field (consistent with previous solar observation work that found that a prominence lies over the neutral line of the related bipolar solar magnetic field). Specifically, for the first magnetic cloud event on 8 May 1979, a coronal mass ejection (CME) was related to an eruptive prominence previously reported as a result of the observation of Solwind (P78-1). Therefore, we identify the cold and dense region in the MC as the prominence material. It is the first time that prominence ejecta were identified by both the plasma and magnetic field features inside 1 AU, and it is also the first time that the thermal ion velocity distribution functions were used to investigate the microstate of the prominence material. Moreover, from our three cases, we also found that this material tended to fall behind the magnetic cloud and become smaller as it propagated farther away from the Sun, which confirms speculations in previous work. Overall, our in situ observations are consistent with three-part CME models.

Evidences on the Existence of Magnetic Flux Rope Before and During a Solar Eruption

NASA Astrophysics Data System (ADS)

Zhang, Jie; Cheng, Xin; Liu, Kai

2013-03-01

We report the observational evidences from the advanced SDO observations that magnetic flux ropes exist before and during solar eruptions. The solar eruption is defined as coronal mass ejection, whether or not associated with a solar flare. Magnetic flux ropes are directly observed as hot EUV channels as seen in the hot AIA 131 (10 MK) and/or AIA 94 (6.4 MK) passbands, but are absent in cool AIA passbands. The fact that flux ropes are only seen in hot temperatures explains their evasion of detection from previous EUV observations, such as SOHO/EIT, TRACE and STEREO/EUVI. The hot channel usually appears as a writhed sigmoidal shape and slowly rises prior to the onset of the impulsive acceleration as well as the onset of the flare. The hot channel transforms into a CME-like semi-circular shape in a continuous way, indicating its trapping or organization by a coherent magnetic structure. The dynamic and thermal properties of flux ropes will also be presented. We further discuss the critical role of flux ropes in CME initiation and subsequent acceleration, in light of contrasting the standard eruptive flare models.

Global Acceleration of Coronal Mass Ejections

NASA Technical Reports Server (NTRS)

Gopalswamy, Nat; Lara, Alejandro; Lepping, Ronald; Kaiser, Michael; Berdichevsky, Daniel; St. Cyr, O. Chris; Lazarus, Al

1999-01-01

Using the observed relation between speeds of coronal mass ejections (CMEs) near the Sun and in the solar wind, we estimate a global acceleration acting on the CMEs. Our study quantifies the qualitative results of Gosling [1997] and numerical simulations that CMEs at 1 AU with speeds closer to the solar wind. We found a linear relation between the global acceleration and the initial speed of the CMEs and the absolute value of the acceleration is similar to the slow solar wind acceleration. Our study naturally divides CMEs into fast and slow ones, the dividing line being the solar wind speed. Our results have important implications to space weather prediction models which need to incorporate this effect in estimating the CME arrival time at 1 AU. We show that the arrival times of CMEs at 1 AU are drastically different from the zero acceleration case.

3D numerical study of the propagation characteristics of a consequence of coronal mass ejections in a structured ambient solar wind

NASA Astrophysics Data System (ADS)

Zhou, Y.; Feng, X. S.

2015-12-01

CMEs have been identified as a prime causal link between solar activity and large, nonrecurrent geomagnetic storm. In order to improve geomagnetic storm predictions, a careful study of CME's propagation characteristics is important. Here, we analyze and quantitatively study the evolution and propagation characteristics of coronal mass ejections (CMEs) launched at several positions into a structured real ambient solar wind by using a three-dimensional (3D) numerical magnetohydrodynamics (MHD) simulation. The ambient solar wind structure during Carrington rotation 2095 is selected, which is an appropriate around activity minimum and declining phase. The CME is initiated by a simple spherical plasmoid model: a spheromak magnetic structure with high speed, high pressure and high plasma density plasmoid. We present a detailed analysis of the plasma, magnetic field, geoeffectiveness, and composition signatures of these CMEs. Results show that the motion and local appearance of a CME in interplanetary space is strongly affected by its interaction with the background solar wind structure, including its velocity, density, and magnetic structures. The simulations show that the initial launched position substantially affects the IP evolution of the CMEs influencing the propagation velocity, the shape, the trajectory and even the geo-effectiveness

MEASURING THE MAGNETIC FIELD OF CORONAL MASS EJECTIONS NEAR THE SUN USING PULSARS

DOE Office of Scientific and Technical Information (OSTI.GOV)

Howard, T. A.; Stovall, K.; Dowell, J.

The utility of Faraday rotation to measure the magnetic field of the solar corona and large-scale transients within is a small, yet growing field in solar physics. This is largely because it has been recognized as a potentially valuable frontier in space weather studies, because the ability to measure the intrinsic magnetic field within coronal mass ejections (CMEs) when they are close to the Sun is of great interest for understanding a key element of space weather. Such measurements have been attempted over the last few decades using radio signals from artificial sources (i.e., spacecraft on the far side ofmore » the Sun), but studies involving natural radio sources are scarce in the literature. We report on a preliminary study involving an attempt to detect the Faraday rotation of a CME that passed in front of a pulsar (PSR B0950+08) in 2015 August. We combine radio measurements with those from a broadband visible light coronagraph, to estimate the upper limit of the magnetic field of the CME when it was in the corona. We find agreement between different approaches for obtaining its density, and values that are consistent with those predicted from prior studies of CME density close to the Sun.« less

Single ICMEs and Complex Transient Structures in the Solar Wind in 2010 - 2011

NASA Astrophysics Data System (ADS)

Rodkin, D.; Slemzin, V.; Zhukov, A. N.; Goryaev, F.; Shugay, Y.; Veselovsky, I.

2018-05-01

We analyze the statistics, solar sources, and properties of interplanetary coronal mass ejections (ICMEs) in the solar wind. The total number of coronal mass ejections (CMEs) registered in the Coordinated Data Analysis Workshops catalog (CDAW) during the first eight years of Cycle 24 was 61% larger than in the same period of Cycle 23, but the number of X-ray flares registered by the Geostationary Operational Environmental Satellite (GOES) was 20 % smaller because the solar activity was lower. The total number of ICMEs in the given period of Cycle 24 in the Richardson and Cane list was 29% smaller than in Cycle 23, which may be explained by a noticeable number of non-classified ICME-like events in the beginning of Cycle 24. For the period January 2010 - August 2011, we identify solar sources of the ICMEs that are included in the Richardson and Cane list. The solar sources of ICME were determined from coronagraph observations of the Earth-directed CMEs, supplemented by modeling of their propagation in the heliosphere using kinematic models (a ballistic and drag-based model). A detailed analysis of the ICME solar sources in the period under study showed that in 11 cases out of 23 (48%), the observed ICME could be associated with two or more sources. For multiple-source events, the resulting solar wind disturbances can be described as complex (merged) structures that are caused by stream interactions, with properties depending on the type of the participating streams. As a reliable marker to identify interacting streams and their sources, we used the plasma ion composition because it freezes in the low corona and remains unchanged in the heliosphere. According to the ion composition signatures, we classify these cases into three types: complex ejecta originating from weak and strong CME-CME interactions, as well as merged interaction regions (MIRs) originating from the CME high-speed stream (HSS) interactions. We describe temporal profiles of the ion composition for the single-source and multi-source solar wind structures and compared them with the ICME signatures determined from the kinematic and magnetic field parameters of the solar wind. In single-source events, the ion charge state, as a rule, has a one-peak enhancement with an average duration of about one day, which is similar to the mean ICME duration of 1.12 days derived from the Richardson and Cane list. In the multi-source events, the total profile of the ion charge state consists of a sequence of enhancements that is associated with the interaction between the participating streams. On average, the total duration of the complex structures that appear as a result of the CME-CME and CME-HSS interactions as determined from their ion composition is 2.4 days, which is more than twice longer than that of the single-source events.

PHYSICAL CONDITIONS OF CORONAL PLASMA AT THE TRANSIT OF A SHOCK DRIVEN BY A CORONAL MASS EJECTION

DOE Office of Scientific and Technical Information (OSTI.GOV)

Susino, R.; Bemporad, A.; Mancuso, S., E-mail: susino@oato.inaf.it

2015-10-20

We report here on the determination of plasma physical parameters across a shock driven by a coronal mass ejection using white light (WL) coronagraphic images and radio dynamic spectra (RDS). The event analyzed here is the spectacular eruption that occurred on 2011 June 7, a fast CME followed by the ejection of columns of chromospheric plasma, part of them falling back to the solar surface, associated with a M2.5 flare and a type-II radio burst. Images acquired by the Solar and Heliospheric Observatory/LASCO coronagraphs (C2 and C3) were employed to track the CME-driven shock in the corona between 2–12 R{submore » ⊙} in an angular interval of about 110°. In this interval we derived two-dimensional (2D) maps of electron density, shock velocity, and shock compression ratio, and we measured the shock inclination angle with respect to the radial direction. Under plausible assumptions, these quantities were used to infer 2D maps of shock Mach number M{sub A} and strength of coronal magnetic fields at the shock's heights. We found that in the early phases (2–4 R{sub ⊙}) the whole shock surface is super-Alfvénic, while later on (i.e., higher up) it becomes super-Alfvénic only at the nose. This is in agreement with the location for the source of the observed type-II burst, as inferred from RDS combined with the shock kinematic and coronal densities derived from WL. For the first time, a coronal shock is used to derive a 2D map of the coronal magnetic field strength over intervals of 10 R{sub ⊙} altitude and ∼110° latitude.« less

A coronagraph for operational space weather predication

NASA Astrophysics Data System (ADS)

Middleton, Kevin F.

2017-09-01

Accurate prediction of the arrival of solar wind phenomena, in particular coronal mass ejections (CMEs), at Earth, and possibly elsewhere in the heliosphere, is becoming increasingly important given our ever-increasing reliance on technology. The potentially severe impact on human technological systems of such phenomena is termed space weather. A coronagraph is arguably the instrument that provides the earliest definitive evidence of CME eruption; from a vantage point on or near the Sun-Earth line, a coronagraph can provide near-definitive identification of an Earth-bound CME. Currently, prediction of CME arrival is critically dependent on ageing science coronagraphs whose design and operation were not optimized for space weather services. We describe the early stages of the conceptual design of SCOPE (the Solar Coronagraph for OPErations), optimized to support operational space weather services.

Flux-Rope Structure of Coronal Mass Ejections

NASA Technical Reports Server (NTRS)

Gopalswamy, N.; Nieves-Chinchilla, T.; Hidalgo, M.; Zhang, J.; Riley, P.; van Driel-Gesztelyi, L.; Mandrini, C. H.

2013-01-01

This Topical Issue (TI) of Solar Physics, devoted to the study of flux-rope structure in coronal mass ejections (CMEs), is based on two Coordinated Data Analysis Workshops (CDAWs) held in 2010 (20-23 September in Dan Diego, California, USA) and 2011 (5-9 September in Alcala, Spain). The primary purpose of the CDAWs was to address the question whether all CMEs have a flux rope structure. Each CDAW was attended by about 50 scientists interested in the origin, propagation, and interplanetary manifestation of CME phenomena.

Predicting ICME properties at 1AU

NASA Astrophysics Data System (ADS)

Lago, A.; Braga, C. R.; Mesquita, A. L.; De Mendonça, R. R. S.

2017-12-01

Coronal mass ejections (CMEs) are among the main origins of geomagnetic disturbances. They change the properties of the near-earth interplanetary medium, enhancing some key parameters, such as the southward interplanetary magnetic field and the solar wind speed. Both quantities are known to be related to the energy transfer from the solar wind to the Earth's magnetosphere via the magnetic reconnection process. Many attempts have been made to predict the magnetic filed and the solar wind speed from coronagraph observations. However, we still have much to learn about the dynamic evolution of ICMEs as they propagate through the interplanetary space. Increased observation capability is probably needed. Among the several attempts to establish correlations between CME and ICME properties, it was found that the average CME propagation speed to 1AU is highly correlated to the ICME peak speed (Dal Lago et al, 2004). In this work, we present an extended study of such correlation, which confirms the results found in our previous study. Some suggestions on how to use this kind of results for space weather estimates are explored.

Evolution of the magnetic helicity flux during the formation and eruption of flux ropes

DOE Office of Scientific and Technical Information (OSTI.GOV)

Romano, P.; Zuccarello, F. P.; Guglielmino, S. L.

We describe the evolution and the magnetic helicity flux for two active regions (ARs) since their appearance on the solar disk: NOAA 11318 and NOAA 11675. Both ARs hosted the formation and destabilization of magnetic flux ropes. In the former AR, the formation of the flux rope culminated in a flare of C2.3 GOES class and a coronal mass ejection (CME) observed by Large Angle and Spectrometric Coronagraph Experiment. In the latter AR, the region hosting the flux rope was involved in several flares, but only a partial eruption with signatures of a minor plasma outflow was observed. We foundmore » a different behavior in the accumulation of the magnetic helicity flux in the corona, depending on the magnetic configuration and on the location of the flux ropes in the ARs. Our results suggest that the complexity and strength of the photospheric magnetic field is only a partial indicator of the real likelihood of an AR producing the eruption of a flux rope and a subsequent CME.« less

Galactic Cosmic-Ray Anistropy During the Forbush Decrease Starting 2013 April 13

NASA Astrophysics Data System (ADS)

Tortermpun, U.; Ruffolo, D.; Bieber, J. W.

2018-01-01

The flux of Galactic cosmic rays (GCRs) can undergo a Forbush decrease (FD) during the passage of a shock, sheath region, or magnetic flux rope associated with a coronal mass ejection (CME). Cosmic-ray observations during FDs can provide information complementary to in situ observations of the local plasma and magnetic field, because cosmic-ray distributions allow remote sensing of distant conditions. Here we develop techniques to determine the GCR anisotropy before and during an FD using data from the worldwide network of neutron monitors, for a case study of the FD starting on 2013 April 13. We find that at times with strong magnetic fluctuations and strong cosmic-ray scattering, there were spikes of high perpendicular anisotropy and weak parallel anisotropy. In contrast, within the CME flux rope there was a strong parallel anisotropy in the direction predicted from a theory of drift motions into one leg of the magnetic flux rope and out the other, confirming that the anisotropy can remotely sense a large-scale flow of GCRs through a magnetic flux structure.

Dependence of the Peak Fluxes of Solar Energetic Particles on CME 3D Parameters from STEREO and SOHO

DOE Office of Scientific and Technical Information (OSTI.GOV)

Park, Jinhye; Moon, Y.-J.; Lee, Harim, E-mail: jinhye@khu.ac.kr

We investigate the relationships between the peak fluxes of 18 solar energetic particle (SEP) events and associated coronal mass ejection (CME) 3D parameters (speed, angular width, and separation angle) obtained from SOHO , and STEREO-A / B for the period from 2010 August to 2013 June. We apply the STEREO CME Analysis Tool (StereoCAT) to the SEP-associated CMEs to obtain 3D speeds and 3D angular widths. The separation angles are determined as the longitudinal angles between flaring regions and magnetic footpoints of the spacecraft, which are calculated by the assumption of a Parker spiral field. The main results are asmore » follows. (1) We find that the dependence of the SEP peak fluxes on CME 3D speed from multiple spacecraft is similar to that on CME 2D speed. (2) There is a positive correlation between SEP peak flux and 3D angular width from multiple spacecraft, which is much more evident than the relationship between SEP peak flux and 2D angular width. (3) There is a noticeable anti-correlation ( r = −0.62) between SEP peak flux and separation angle. (4) The multiple-regression method between SEP peak fluxes and CME 3D parameters shows that the longitudinal separation angle is the most important parameter, and the CME 3D speed is secondary on SEP peak flux.« less

Observation of quasi-periodic solar radio bursts associated with propagating fast-mode waves

NASA Astrophysics Data System (ADS)

Goddard, C. R.; Nisticò, G.; Nakariakov, V. M.; Zimovets, I. V.; White, S. M.

2016-10-01

Aims: Radio emission observations from the Learmonth and Bruny Island radio spectrographs are analysed to determine the nature of a train of discrete, periodic radio "sparks" (finite-bandwidth, short-duration isolated radio features) which precede a type II burst. We analyse extreme ultraviolet (EUV) imaging from SDO/AIA at multiple wavelengths and identify a series of quasi-periodic rapidly-propagating enhancements, which we interpret as a fast wave train, and link these to the detected radio features. Methods: The speeds and positions of the periodic rapidly propagating fast waves and the coronal mass ejection (CME) were recorded using running-difference images and time-distance analysis. From the frequency of the radio sparks the local electron density at the emission location was estimated for each. Using an empirical model for the scaling of density in the corona, the calculated electron density was used to obtain the height above the surface at which the emission occurs, and the propagation velocity of the emission location. Results: The period of the radio sparks, δtr = 1.78 ± 0.04 min, matches the period of the fast wave train observed at 171 Å, δtEUV = 1.7 ± 0.2 min. The inferred speed of the emission location of the radio sparks, 630 km s-1, is comparable to the measured speed of the CME leading edge, 500 km s-1, and the speeds derived from the drifting of the type II lanes. The calculated height of the radio emission (obtained from the density) matches the observed location of the CME leading edge. From the above evidence we propose that the radio sparks are caused by the quasi-periodic fast waves, and the emission is generated as they catch up and interact with the leading edge of the CME. The movie associated to Fig. 2 is available at http://www.aanda.org

Statistical Analysis of Solar Events Associated with SSC over Year of Solar Maximum during Cycle 23: 1. Identification of Related Sun-Earth Events

NASA Astrophysics Data System (ADS)

Grison, B.; Bocchialini, K.; Menvielle, M.; Chambodut, A.; Cornilleau-Wehrlin, N.; Fontaine, D.; Marchaudon, A.; Pick, M.; Pitout, F.; Schmieder, B.; Regnier, S.; Zouganelis, Y.

2017-12-01

Taking the 32 sudden storm commencements (SSC) listed by the observatory de l'Ebre / ISGI over the year 2002 (maximal solar activity) as a starting point, we performed a statistical analysis of the related solar sources, solar wind signatures, and terrestrial responses. For each event, we characterized and identified, as far as possible, (i) the sources on the Sun (Coronal Mass Ejections -CME-), with the help of a series of herafter detailed criteria (velocities, drag coefficient, radio waves, polarity), as well as (ii) the structure and properties in the interplanetary medium, at L1, of the event associated to the SSC: magnetic clouds -MC-, non-MC interplanetary coronal mass ejections -ICME-, co-rotating/stream interaction regions -SIR/CIR-, shocks only and unclear events that we call "miscellaneous" events. The categorization of the events at L1 is made on published catalogues. For each potential CME/L1 event association we compare the velocity observed at L1 with the one observed at the Sun and the estimated balistic velocity. Observations of radio emissions (Type II, Type IV detected from the ground and /or by WIND) associated to the CMEs make the solar source more probable. We also compare the polarity of the magnetic clouds with the hemisphere of the solar source. The drag coefficient (estimated with the drag-based model) is calculated for each potential association and it is compared to the expected range values. We identified a solar source for 26 SSC related events. 12 of these 26 associations match all criteria. We finally discuss the difficulty to perform such associations.

Relativistic Electron Response to the Combined Magnetospheric Impact of a Coronal Mass Ejection Overlapping with a High-Speed Stream: Van Allen Probes Observations

NASA Technical Reports Server (NTRS)

Kanekal, S. G.; Baker, D. N.; Henderson, M. G.; Li, W.; Fennell, J. F.; Zheng, Y.; Richardson, I. G.; Jones, A.; Ali, A. F.; Elkington, S. R.;

Steps Towards Detecting Coronal Mass Ejections on Stars: Tests Using Solar Data

NASA Astrophysics Data System (ADS)

Saar, S.; Cressman, A.

2017-12-01

One important parameter affecting exoplanet habitability is the frequency and energy spectrum of coronal mass ejections (CMEs) and their associated energetic particle fluences. Estimates of CME rates have been made based on magnetic fluxes, and the frequency of strong flares, but actual detections have been sparse and debated. We propose a new way to detect stellar CMEs by watching for their effect on the He I 1083 nm line with high cadence, high S/N data. Filaments are dark against the background chromosphere in He I, and a filament eruption (FE) or CME should lead to a sudden, small step function increase in total emission, provided the rest of the star was unchanging. He I disk integrated velocity should show a similar change, depending on the relative velocity of the newly uncovered underlying material. We test this idea using CRISP data from the Mauna Loa Solar Observatory compared to the AIA FE list of MacCauley et al. Though hampered by the typically short observing window each day, which is not always well matched to the solar events, we identify several FE with the distinctive expected He I signatures in integrated light. We compare our "detections" with the He I signatures of flares (with and without CMEs), and with randomly selected days of data to better understand the detection success rate, and the number of false positives. We note that the signature of flares typically evolves more quickly, and exhibits more complex intensity and velocity changes (often with positive and negative excursions). We conclude that He I observations hold promise for obtaining statistics on stellar CMEs. We plan test stellar observations in the near future. This work was supported by NASA Heliophysics grant NNX16AB79G.

Low coronal signatures of coronal mass ejections

NASA Astrophysics Data System (ADS)

Attrill, Gemma Diana Ruth

Coronal mass ejections (CMEs) are vast eruptions of magnetised plasma that explode from the solar atmosphere. This thesis focuses on understanding the nascent stages of CMEs, and their magnetic development as they expand into the interplanetary space of our solar system. This is an important part of our effort to understand the space weather environment that we live in, and increasingly interact with through satellite communications technologies. Predominantly through combining extreme ultra-violet imaging and magnetogram data, two low coronal signatures of CMEs, namely coronal waves and dimmings, are studied. A comprehensive list of observational properties of EIT coronal waves is compiled and potential counterparts in radio, Ha, soft X-rays and He n wavelengths are also discussed. New observational constraints on EIT coronal waves are presented, most notably diffuse coronal waves are shown to have a magnetic nature. Finding that many observational constraints are not satisfactorily explained by current theories, a new model for understanding the physical nature of diffuse coronal waves is developed. The new model interprets diffuse coronal "wave" bright fronts to be the low coronal magnetic footprint of CMEs. Implications for developing our understanding of how CMEs become large-scale in the low corona are discussed. Application of the model demonstrates how an understanding of the formation of complex global-scale coronal dimmings can be derived. For the first time it is shown that study of the evolution and magnetic nature of coronal dimming regions can be used to probe the post-eruptive evolution of the CME. Finally, a study is presented regarding why and how CME-related dimmings recover, despite the "open" magnetic connectivity of the ejecta to the Sun being maintained as indicated by electron heat flux measurements at 1 AU.

DESTABILIZATION OF A SOLAR PROMINENCE/FILAMENT FIELD SYSTEM BY A SERIES OF EIGHT HOMOLOGOUS ERUPTIVE FLARES LEADING TO A CME

DOE Office of Scientific and Technical Information (OSTI.GOV)

Panesar, Navdeep K.; Moore, Ronald L.; Sterling, Alphonse C.

2015-09-20

Homologous flares are flares that occur repetitively in the same active region, with similar structure and morphology. A series of at least eight homologous flares occurred in active region NOAA 11237 over 2011 June 16–17. A nearby prominence/filament was rooted in the active region, and situated near the bottom of a coronal cavity. The active region was on the southeast solar limb as seen from the Solar Dynamics Observatory/Atmospheric Imaging Assembly, and on the disk as viewed from the Solar TErrestrial RElations Observatory/EUVI-B. The dual perspective allows us to study in detail behavior of the prominence/filament material entrained in themore » magnetic field of the repeatedly erupting system. Each of the eruptions were mainly confined, but expelled hot material into the prominence/filament cavity system (PFCS). The field carrying and containing the ejected hot material interacted with the PFCS and caused it to inflate, resulting in a step-wise rise of the PFCS approximately in step with the homologous eruptions. The eighth eruption triggered the PFCS to move outward slowly, accompanied by a weak coronal dimming. As this slow PFCS eruption was underway, a final “ejective” flare occurred in the core of the active region, resulting in strong dimming in the EUVI-B images and expulsion of a coronal mass ejection (CME). A plausible scenario is that the repeated homologous flares could have gradually destabilized the PFCS, and its subsequent eruption removed field above the acitive region and in turn led to the ejective flare, strong dimming, and CME.« less

Statistical study of coronal mass ejection source locations: Understanding CMEs viewed in coronagraphs

NASA Astrophysics Data System (ADS)

Wang, Yuming; Chen, Caixia; Gui, Bin; Shen, Chenglong; Ye, Pinzhong; Wang, S.

2011-04-01

How to properly understand coronal mass ejections (CMEs) viewed in white light coronagraphs is crucial to many relative researches in solar and space physics. The issue is now particularly addressed in this paper through studying the source locations of all the 1078 Large Angle and Spectrometric Coronagraph (LASCO) CMEs listed in Coordinated Data Analysis Workshop (CDAW) CME catalog during 1997-1998 and their correlation with CMEs' apparent parameters. By manually checking LASCO and Extreme Ultraviolet Imaging Telescope (EIT) movies of these CMEs, we find that, except 231 CMEs whose source locations cannot be identified due to poor data, there are 288 CMEs with location identified on the frontside solar disk, 234 CMEs appearing above solar limb, and 325 CMEs without evident eruptive signatures in the field of view of EIT. On the basis of the statistical results of CMEs' source locations, there are four physical issues: (1) the missing rate of CMEs by SOHO LASCO and EIT, (2) the mass of CMEs, (3) the causes of halo CMEs, and (4) the deflections of CMEs in the corona, are exhaustively analyzed. It is found that (1) about 32% frontside CMEs cannot be recognized by SOHO, (2) the brightness of a CME at any heliocentric distance is roughly positively correlated with its speed, and the CME mass derived from the brightness is probably overestimated, (3) both projection effect and violent eruption are the major causes of halo CMEs, and especially for limb halo CMEs the latter is the primary one, and (4) most CMEs deflected toward equator near the solar minimum; these deflections can be classified into three types: the asymmetrical expansion, the nonradial ejection, and the deflected propagation.

A Comparative Study of Shock Structures for the Halloween 2003 and the 23 July 2012 CME Events

NASA Astrophysics Data System (ADS)

Wu, C. C.; Liou, K.

2015-12-01

Interplanetary (IP) shocks driven by coronal mass ejections (CMEs) play an important role in space weather. For example, solar energetic particles are accelerated at the shock and storm sudden commencements are produced by the impingement of the Earth by the shocks. Here, we study shocks associated with two major CME events - the Halloween 2003 and the 23 July 2012 CME events, using a three-dimensional (3D) magnetohydrodynamics model (H3DMHD). The H3DMHD (Wu et al. 2007, JGR) combines the kinematic solar wind model (HAF) for regions near the solar surface (2.5-18 Rs) and a 3D magnetohydrodynamics model (Han et al. 1988), which takes output from HAF at 18 Rs and propagates outward up to 1.7 AU. The H3DMHD code has been fully tested and is capable of simulating disturbances propagating in the solar wind. We will focus on the temporal and spatial structure of the CME-driven shocks, including the shock type and strength.

The Solar Energetic Particle Event of 2010 August 14: Connectivity with the Solar Source Inferred from Multiple Spacecraft Observations and Modeling

DOE Office of Scientific and Technical Information (OSTI.GOV)

Lario, D.; Kwon, R.-Y.; Raouafi, N. E.

We analyze one of the first solar energetic particle (SEP) events of solar cycle 24 observed at widely separated spacecraft in order to assess the reliability of models currently used to determine the connectivity between the sources of SEPs at the Sun and spacecraft in the inner heliosphere. This SEP event was observed on 2010 August 14 by near-Earth spacecraft, STEREO-A (∼80° west of Earth) and STEREO-B (∼72° east of Earth). In contrast to near-Earth spacecraft, the footpoints of the nominal magnetic field lines connecting STEREO-A and STEREO-B with the Sun were separated from the region where the parent fastmore » halo coronal mass ejection (CME) originated by ∼88° and ∼47° in longitude, respectively. We discuss the properties of the phenomena associated with this solar eruption. Extreme ultraviolet and white-light images are used to specify the extent of the associated CME-driven coronal shock. We then assess whether the SEPs observed at the three heliospheric locations were accelerated by this shock or whether transport mechanisms in the corona and/or interplanetary space provide an alternative explanation for the arrival of particles at the poorly connected spacecraft. A possible scenario consistent with the observations indicates that the observation of SEPs at STEREO-B and near Earth resulted from particle injection by the CME shock onto the field lines connecting to these spacecraft, whereas SEPs reached STEREO-A mostly via cross-field diffusive transport processes. The successes, limitations, and uncertainties of the methods used to resolve the connection between the acceleration sites of SEPs and the spacecraft are evaluated.« less

Properties of Ground Level Enhancement Events and the Associated Solar Eruptions During Solar Cycle 23

NASA Technical Reports Server (NTRS)

Gopalswamy, N.; Xie, H.; Yashiro, S.; Akiyama, S.; Makela, P.; Usokin, I. G.

2012-01-01

Solar cycle 23 witnessed the most complete set of observations of coronal mass ejections (CMEs) associated with the Ground Level Enhancement (GLE) events. We present an overview of the observed properties of the GLEs and those of the two associated phenomena, viz., flares and CMEs, both being potential sources of particle acceleration. Although we do not find a striking correlation between the GLE intensity and the parameters of flares and CMEs, the solar eruptions are very intense involving X-class flares and extreme CME speeds (average approx. 2000 km/s). An M7.1 flare and a 1200 km/s CME are the weakest events in the list of 16 GLE events. Most (80 %) of the CMEs are full halos with the three non-halos having widths in the range 167 to 212 degrees. The active regions in which the GLE events originate are generally large: 1290 msh (median 1010 msh) compared to 934 msh (median: 790 msh) for SEP-producing active regions. For accurate estimation of the CME height at the time of metric type II onset and GLE particle release, we estimated the initial acceleration of the CMEs using flare and CME observations. The initial acceleration of GLE-associated CMEs is much larger (by a factor of 2) than that of ordinary CMEs (2.3 km/sq s vs. 1 km/sq s). We confirmed the initial acceleration for two events for which CME measurements are available in the inner corona. The GLE particle release is delayed with respect to the onset of all electromagnetic signatures of the eruptions: type II bursts, low frequency type III bursts, soft X-ray flares and CMEs. The presence of metric type II radio bursts some 17 min (median: 16 min; range: 3 to 48 min) before the GLE onset indicates shock formation well before the particle release. The release of GLE particles occurs when the CMEs reach an average height of approx 3.09 R(sub s) (median: 3.18 R (sub s) ; range: 1.71 to 4.01 R (sub s) ) for well-connected events (source longitude in the range W20–W90). For poorly connected events, the average CME height at GLE particle release is 66 % larger (mean: 5.18 R (sub s) ; median: 4.61 R (sub s) ; range: 2.75–8.49 R (sub s) ). The longitudinal dependence is consistent with shock accelerations because the shocks from poorly connected events need to expand more to cross the field lines connecting to an Earth observer. On the other hand, the CME height at metric type II burst onset has no longitudinal dependence because electromagnetic signals do not require magnetic connectivity to the observer. For several events, the GLE particle release is very close to the time of first appearance of the CME in the coronagraphic field of view, so we independently confirmed the CME height at particle release. The CME height at metric type II burst onset is in the narrow range 1.29 to 1.8 R(sub s), with mean and median values of 1.53 and 1.47 R(sub s). The CME heights at metric type II burst onset and GLE particle release correspond to the minimum and maximum in the Alfven speed profile. The increase in CME speed between these two heights suggests an increase in Alfvenic Mach number from 2 to 3. The CME heights at GLE particle release are in good agreement with those obtained from the velocity dispersion analysis, including the source longitude dependence. We also discuss the implications of the delay of GLE particle release with respect to complex type III bursts by approx 18 min (median: 16 in; range: 2 to 44 min) for the flare acceleration mechanism. A similar analysis is also performed on the delay of particle release relative to the hard X-ray emission.

THE MAJOR GEOEFFECTIVE SOLAR ERUPTIONS OF 2012 MARCH 7: COMPREHENSIVE SUN-TO-EARTH ANALYSIS

DOE Office of Scientific and Technical Information (OSTI.GOV)

Patsourakos, S.; Nindos, A.; Kouloumvakos, A.

During the interval 2012 March 7–11 the geospace experienced a barrage of intense space weather phenomena including the second largest geomagnetic storm of solar cycle 24 so far. Significant ultra-low-frequency wave enhancements and relativistic-electron dropouts in the radiation belts, as well as strong energetic-electron injection events in the magnetosphere were observed. These phenomena were ultimately associated with two ultra-fast (>2000 km s{sup −1}) coronal mass ejections (CMEs), linked to two X-class flares launched on early 2012 March 7. Given that both powerful events originated from solar active region NOAA 11429 and their onsets were separated by less than an hour,more » the analysis of the two events and the determination of solar causes and geospace effects are rather challenging. Using satellite data from a flotilla of solar, heliospheric and magnetospheric missions a synergistic Sun-to-Earth study of diverse observational solar, interplanetary and magnetospheric data sets was performed. It was found that only the second CME was Earth-directed. Using a novel method, we estimated its near-Sun magnetic field at 13 R{sub ⊙} to be in the range [0.01, 0.16] G. Steep radial fall-offs of the near-Sun CME magnetic field are required to match the magnetic fields of the corresponding interplanetary CME (ICME) at 1 AU. Perturbed upstream solar-wind conditions, as resulting from the shock associated with the Earth-directed CME, offer a decent description of its kinematics. The magnetospheric compression caused by the arrival at 1 AU of the shock associated with the ICME was a key factor for radiation-belt dynamics.« less

A FAST PROPAGATING EXTREME-ULTRAVIOLET WAVE ASSOCIATED WITH A MINI-FILAMENT ERUPTION

DOE Office of Scientific and Technical Information (OSTI.GOV)

Zheng Ruisheng; Jiang Yunchun; Yang Jiayan

The fast extreme-ultraviolet (EUV) waves (>1000 km s{sup -1}) in the solar corona were very rare in the past. Taking advantage of the high temporal and spatial resolution of the Solar Dynamics Observatory observations, we present a fast EUV wave associated with a mini-filament eruption, a C1.0 flare, and a coronal mass ejection (CME) on 2011 September 30. The event took place at the periphery between two active regions (ARs). The mini-filament rapidly erupted as a blowout jet associated with a flare and a CME. The CME front was likely developed from the large-scale overlying loops. The wave onset wasmore » nearly simultaneous with the start of the jet and the flare. The wave departed far from the flare center and showed a close location relative to the rapid jet. The wave had an initial speed of about 1100 km s{sup -1} and a slight deceleration in the last phase, and the velocity decreased to about 500 km s{sup -1}. The wave propagated in a narrow angle extent, likely to avoid the ARs on both sides. All the results provide evidence that the fast EUV wave was a fast-mode MHD wave. The wave resisted being driven by the CME, because it opened up the large-scale loops and its front likely formed later than the wave. The wave was most likely triggered by the jet, due to their close timing and location relations.« less

Can We Predict CME Deflections Based on Solar Magnetic Field Configuration Alone?

NASA Astrophysics Data System (ADS)

Kay, C.; Opher, M.; Evans, R. M.

2013-12-01

Accurate space weather forecasting requires knowledge of the trajectory of coronal mass ejections (CMEs), including predicting CME deflections close to the Sun and through interplanetary space. Deflections of CMEs occur due to variations in the background magnetic field or solar wind speed, magnetic reconnection, and interactions with other CMEs. Using our newly developed model of CME deflections due to gradients in the background solar magnetic field, ForeCAT (Kay et al. 2013), we explore the questions: (a) do all simulated CMEs ultimately deflect to the minimum in the background solar magnetic field? (b) does the majority of the deflection occur in the lower corona below 4 Rs? ForeCAT does not include temporal variations in the magnetic field of active regions (ARs), spatial variations in the background solar wind speed, magnetic reconnection, or interactions with other CMEs. Therefore we focus on the effects of the steady state solar magnetic field. We explore two different Carrington Rotations (CRs): CR 2029 (April-May 2005) and CR 2077 (November-December 2008). Little is known about how the density and magnetic field fall with distance in the lower corona. We consider four density models derived from observations (Chen 1996, Mann et al. 2003, Guhathakurta et al. 2006, Leblanc et al. 1996) and two magnetic field models (PFSS and a scaled model). ForeCAT includes drag resulting from both CME propagation and deflection through the background solar wind. We vary the drag coefficient to explore the effect of drag on the deflection at 1 AU.

Tracking the Momentum Flux of a CME and Quantifying Its Influence on Geomagnetically Induced Currents at Earth

NASA Technical Reports Server (NTRS)

Savani, N. P.; Vourlidas, A.; Pulkkinen, A.; Nieves-Chinchilla, T.; Lavraud, B.; Owens, M. J.

2013-01-01

We investigate a coronal mass ejection (CME) propagating toward Earth on 29 March 2011. This event is specifically chosen for its predominately northward directed magnetic field, so that the influence from the momentum flux onto Earth can be isolated. We focus our study on understanding how a small Earth-directed segment propagates. Mass images are created from the white-light cameras onboard STEREO which are also converted into mass height-time maps (mass J-maps). The mass tracks on these J-maps correspond to the sheath region between the CME and its associated shockfront as detected by in situ measurements at L1. A time series of mass measurements from the STEREOCOR-2A instrument is made along the Earth propagation direction. Qualitatively, this mass time series shows a remarkable resemblance to the L1 in situ density series. The in situ measurements are used as inputs into a three-dimensional (3-D) magnetospheric space weather simulation from the Community Coordinated Modeling Center. These simulations display a sudden compression of the magnetosphere from the large momentum flux at the leading edge of the CME, and predictions are made for the time derivative of the magnetic field (dBdt) on the ground. The predicted dBdt values were then compared with the observations from specific equatorially located ground stations and showed notable similarity. This study of the momentum of a CME from the Sun down to its influence on magnetic ground stations on Earth is presented as a preliminary proof of concept, such that future attempts may try to use remote sensing to create density and velocity time series as inputs to magnetospheric simulations.

Comparing Automatic CME Detections in Multiple LASCO and SECCHI Catalogs

DOE Office of Scientific and Technical Information (OSTI.GOV)

Hess, Phillip; Colaninno, Robin C., E-mail: phillip.hess.ctr@nrl.navy.mil, E-mail: robin.colaninno@nrl.navy.mil

With the creation of numerous automatic detection algorithms, a number of different catalogs of coronal mass ejections (CMEs) spanning the entirety of the Solar and Heliospheric Observatory ( SOHO ) Large Angle Spectrometric Coronagraph (LASCO) mission have been created. Some of these catalogs have been further expanded for use on data from the Solar Terrestrial Earth Observatory ( STEREO ) Sun Earth Connection Coronal and Heliospheric Investigation (SECCHI) as well. We compare the results from different automatic detection catalogs (Solar Eruption Event Detection System (SEEDS), Computer Aided CME Tracking (CACTus), and Coronal Image Processing (CORIMP)) to ensure the consistency ofmore » detections in each. Over the entire span of the LASCO catalogs, the automatic catalogs are well correlated with one another, to a level greater than 0.88. Focusing on just periods of higher activity, these correlations remain above 0.7. We establish the difficulty in comparing detections over the course of LASCO observations due to the change in the instrument image cadence in 2010. Without adjusting catalogs for the cadence, CME detection rates show a large spike in cycle 24, despite a notable drop in other indices of solar activity. The output from SEEDS, using a consistent image cadence, shows that the CME rate has not significantly changed relative to sunspot number in cycle 24. These data, and mass calculations from CORIMP, lead us to conclude that any apparent increase in CME rate is a result of the change in cadence. We study detection characteristics of CMEs, discussing potential physical changes in events between cycles 23 and 24. We establish that, for detected CMEs, physical parameters can also be sensitive to the cadence.« less

Coronal Structure of a Flaring Region and Associated Coronal Mass Ejection

NASA Technical Reports Server (NTRS)

Kundu, Mukul R.; Manoharan, P. K.

2003-01-01

We report the multiwavelength investigations of an eruptive flare event that occurred on 2001 April 2 at about 11 UT. The manifestations associated with this flare event have been studied from the near-Sun region to about 0.5 AU. The H-alpha images from the Meudon Spectroheliograph reveal a fast spectacular eruption of plasmoids from the flare site to the west and a Moreton wave disturbance propagating toward the south, A bright, fast, wide coronal mass ejection (CME) associated with this eruptive event was imaged by SOHO/LASCO and the remote-sensing interplanetary scintillation technique. The timings and positions of the Type II radio bursts, H-alpha eruption, and CME onset as well as the magnetic field configuration suggest a release of energy at the null point. The results seem to support the "breakout" scenario proposed by Antiochos and coworkers, and they are also suggestive that the energy release is followed by magnetic reconnection between the low-lying loops near the separatrix and the loop system above them.

EUV Dimmings as a Diagnostic of CMEs and Related Phenomena

NASA Technical Reports Server (NTRS)

Thompson, Barbara J.; Mays, M. Leila; Webb, David F.; West, Matthew J.

2012-01-01

Large-scale coronal EUV dimmings, developing on timescaJes of minutes to hours in association with a flare or filament eruption, are known to exhibit a high correlation with coronal mass ejections. While most observations indicate that the decrease in emission in a dimming is due, at least in part, to a density decrease, a complete understanding requires us to examine at least four mechanisms that have been observed to cause darkened regions in the corona: 1) mass loss, 2) cooling, 3) heating, and 4) absorption/obscuration. Recent advances in automatic detection, observations with improved cadence and resolution, multi-viewpoint imaging, and spectroscopic studies have continued to shed light on dimming formation, evolution, and recovery. However, there are still some outstanding questions, including 1) Why do some CMEs show dimming and some do not? 2) What determines the location of a dimming? 3) What determines the temporal evolution of a dimming? 4) How does the post-eruption dimming connect to the ICME? 5) What is the relationship between dimmings and other CME-associated phenomena? The talk will emphasize the different formation mechanisms of dimmings and their relationship to CMEs and CME-associated phenomena.

The magnetospheric and ionospheric response to a very strong interplanetary shock and coronal mass ejection

NASA Astrophysics Data System (ADS)

Ridley, A. J.; De Zeeuw, D. L.; Manchester, W. B.; Hansen, K. C.

2006-01-01

We present results from a coupled magnetospheric and ionospheric simulation of a very strong solar wind shock and coronal mass ejection (CME). The solar wind drivers that are used for this simulation were output from the Sun-to-Earth MHD simulation of the Carrington-like CME reported in Manchester et al. [Manchester IV, W., Ridley, A., Gombosi, T., De Zeeuw, D. Modeling the Sun-Earth propagation of a very fast cme. Adv. Space Res. 38 (this issue), 2006]. We use the University of Michigan's BATS-R-US MHD code to model the global magnetosphere and coupled height integrated ionosphere. As the interplanetary shock swept over the magnetosphere, a wave is observed to propagate through the system. This is evident both in the magnetosphere and ionosphere. On the dayside, the magnetospheric bowshock is shown to bifurcate. The inner shock is pushed close to the inner boundary, where it "bounces" and propagates back outwards to meet the outer bowshock, which is propagating inwards. The inward and outward motion of the bowshocks can be observed propagating down the flanks of the magnetosphere. In the ionosphere, the wave is manifested as two pairs of field-aligned currents moving antisunward. The first pair is opposite of the normal region-1 current system, while the second pair is in the same sense as the normal region-1 system. The ionospheric potential shows a behavior consistent with the field-aligned current pattern, given the strong gradient in the conductance from the dayside to the nightside. As the magnetic cloud flows over the system, the entire magnetopause boundary is observed to move inside of geosynchronous orbit (6.6 Re). At the time of the most extreme solar wind conditions, the magnetopause boundary encounters the inner edge of the magnetospheric simulation domain. During the magnetic cloud, the ionospheric cross-polar cap potential is shown to match the Siscoe et al. [Siscoe, G.L., Erickson, G., Sonnerup, B., Maynard, N., Schoendorf, J., Siebert, K., Weimer, D., White, W., Wilson, G. Hill model of transpolar potential saturation: comparisons with MHD simulations. J. Geophys. Res. 107, 1321, doi:10.1029/2001JA009176, 2002] formulation relating the ionospheric potential to the solar wind and IMF conditions. It is shown that by using this formulation, the extremely large potentials observed in the MHD results are most likely saturated.

The Physical Processes of CME/ICME Evolution

NASA Astrophysics Data System (ADS)

Manchester, Ward; Kilpua, Emilia K. J.; Liu, Ying D.; Lugaz, Noé; Riley, Pete; Török, Tibor; Vršnak, Bojan

2017-11-01

As observed in Thomson-scattered white light, coronal mass ejections (CMEs) are manifest as large-scale expulsions of plasma magnetically driven from the corona in the most energetic eruptions from the Sun. It remains a tantalizing mystery as to how these erupting magnetic fields evolve to form the complex structures we observe in the solar wind at Earth. Here, we strive to provide a fresh perspective on the post-eruption and interplanetary evolution of CMEs, focusing on the physical processes that define the many complex interactions of the ejected plasma with its surroundings as it departs the corona and propagates through the heliosphere. We summarize the ways CMEs and their interplanetary CMEs (ICMEs) are rotated, reconfigured, deformed, deflected, decelerated and disguised during their journey through the solar wind. This study then leads to consideration of how structures originating in coronal eruptions can be connected to their far removed interplanetary counterparts. Given that ICMEs are the drivers of most geomagnetic storms (and the sole driver of extreme storms), this work provides a guide to the processes that must be considered in making space weather forecasts from remote observations of the corona.

"Driverless" Shocks in the Interplanetary Medium

NASA Technical Reports Server (NTRS)

Gopalswamy, N.; Kaiser, M. L.; Lara, A.

1999-01-01

Many interplanetary shocks have been detected without an obvious driver behind them. These shocks have been thought to be either blast waves from solar flares or shocks due to sudden increase in solar wind speed caused by interactions between large scale open and closed field lines of the Sun. We investigated this problem using a set of interplanetary shock detected {\\it in situ} by the Wind space craft and tracing their solar origins using low frequency radio data obtained by the Wind/WAVES experiment. For each of these "driverless shocks" we could find a unique coronal mass ejections (CME) event observed by the SOHO (Solar and Heliospheric Observatory) coronagraphs. We also found that these CMEs were ejected at large angles from the Sun-Earth line. It appears that the "driverless shocks" are actually driver shocks, but the drivers were not intercepted by the spacecraft. We conclude that the interplanetary shocks are much more extended than the driving CMEs.

Eruption of a Multiple-Turn Helical Magnetic Flux Tube in a Large Flare: Evidence for External and Internal Reconnection that Fits the Breakout Model of Solar Magnetic Eruptions

NASA Technical Reports Server (NTRS)

Gary, G. Allen; Moore, R. L.

2004-01-01

We present observations and an interpretation of a unique multiple-turn spiral flux tube eruption from active region 10030 on 2002 July 15. The TRACE C IV observations clearly show a flux tube that is helical and erupting from within a sheared magnetic field. These observations are interpreted in the context of the breakout model for magnetic field explosions. The initiation of the helix eruption. as determined by a linear backward extrapolation, starts 25 s after the peak of the flare's strongest impulsive spike of microwave gyrosynchrotron radiation early in the flare s explosive phase, implying that the sheared core field is not the site of the initial reconnection. Within the quadrupolar configuration of the active region, the external and internal reconnection sites are identified in each of two consecutive eruptive flares that produce a double coronal mass ejection (CME). The first external breakout reconnection apparently releases an underlying sheared core field and allows it to erupt, leading to internal reconnection in the wake of the erupting helix. This internal reconnection releases the helix and heats the two-ribbon flare. These events lead to the first CME and are followed by a second breakout that initiates a second and larger halo CME. The strong magnetic shear in the region is compatible with the observed rapid proper motion and evolution of the active region. The multiple-turn helix originates from above a sheared-field magnetic inversion line within a filament channel. and starts to erupt only after fast breakout reconnection has started. These observations are counter to the standard flare model and support the breakout model for eruptive flare initiation.

Comparison of CME radial velocities from a flux rope model and an ice cream cone model

NASA Astrophysics Data System (ADS)

Kim, T.; Moon, Y.; Na, H.

2011-12-01

Coronal Mass Ejections (CMEs) on the Sun are the largest energy release process in the solar system and act as the primary driver of geomagnetic storms and other space weather phenomena on the Earth. So it is very important to infer their directions, velocities and three-dimensional structures. In this study, we choose two different models to infer radial velocities of halo CMEs since 2008 : (1) an ice cream cone model by Xue et al (2005) using SOHO/LASCO data, (2) a flux rope model by Thernisien et al. (2009) using the STEREO/SECCHI data. In addition, we use another flux rope model in which the separation angle of flux rope is zero, which is morphologically similar to the ice cream cone model. The comparison shows that the CME radial velocities from among each model have very good correlations (R>0.9). We will extending this comparison to other partial CMEs observed by STEREO and SOHO.

IMAGING PROMINENCE ERUPTIONS OUT TO 1 AU

DOE Office of Scientific and Technical Information (OSTI.GOV)

Wood, Brian E.; Howard, Russell A.; Linton, Mark G., E-mail: brian.wood@nrl.navy.mil

2016-01-10

Views of two bright prominence eruptions trackable all the way to 1 AU are here presented, using the heliospheric imagers on the Solar TErrestrial RElations Observatory (STEREO) spacecraft. The two events first erupted from the Sun on 2011 June 7 and 2012 August 31, respectively. Only these two examples of clear prominence eruptions observable this far from the Sun could be found in the STEREO image database, emphasizing the rarity of prominence eruptions this persistently bright. For the 2011 June event, a time-dependent 3D reconstruction of the prominence structure is made using point-by-point triangulation. This is not possible for the August event due to amore » poor viewing geometry. Unlike the coronal mass ejection (CME) that accompanies it, the 2011 June prominence exhibits little deceleration from the Sun to 1 AU, as a consequence moving upwards within the CME. This demonstrates that prominences are not necessarily tied to the CME's magnetic structure far from the Sun. A mathematical framework is developed for describing the degree of self-similarity for the prominence's expansion away from the Sun. This analysis suggests only modest deviations from self-similar expansion, but close to the Sun the prominence expands radially somewhat more rapidly than self-similarity would predict.« less

X-ray Magnetosheath Emission from Solar Wind Charge Exchange During Two CME Events in 2001

NASA Astrophysics Data System (ADS)

Sembay, S.; Whittaker, I. C.; Read, A.; Carter, J. A.; Milan, S. E.; Palmroth, M.

2016-12-01

Using a combination of the GUMICS-4 MHD model and observed solar wind heavy ion abundances from ACE, we produce case studies looking at X-ray emission from charge exchange in the Earth's magnetosheath. We specifically look in the 0.5-0.7 keV range, which is dominated by highly ionised oxygen emission. Previous studies looking at solar wind charge exchange (SWCX) emission have verified our modelling process via comparison to the XMM-Newton X-ray observatory, and we use the same simulation process here. This study investigates the emission magnitude changes that occur during two coronal mass ejection (CME) events (31 March 2001 and 21 October 2001). As part of this work we also provide a novel masking technique to exclude the plasma of terrestrial origin in the MHD model. As expected the two CME cases examined provide an increased dynamic pressure which pushes the magnetopause closer to the Earth, with a high temporal variation. We show how these changes cause an increase in the peak SWCX emission signature by over an order of magnitude from the quiescent solar wind case. Imaging of this SWCX emission allows a global view of the magnetopause shape and position, a technique planned for future missions such as SMILE (Solar wind Magnetosphere Ionosphere Link Explorer).

New Aspects of a Lid-Removal Mechanism in the Onset of a SEP-Producing Eruption Sequence

NASA Technical Reports Server (NTRS)

Sterling, Alphonse C.; Moore, Ronald L.; Falconer, David A.; Knox, Javon M.

2014-01-01

We examine a sequence of two ejective eruptions from a single active region on 2012 January 23, using magnetograms and EUV images from SDO/HMI and SDO/AIA, and EUV images from STEREO. Cheng et al. (2013) showed that the first eruption's ("Eruption 1'') flux rope was apparent only in "hotter'' AIA channels, and that it removed overlying field that allowed the second eruption (``Eruption 2'') to begin via ideal MHD instability; here we say Eruption 2 began via a ``lid removal'' mechanism. We show that during Eruption-1's onset, its flux rope underwent ``tether weakening'' (TW) reconnection with the field of an adjacent active region. Standard flare loops from Eruption 1 developed over Eruption-2's flux rope and enclosed filament, but these overarching new loops were unable to confine that flux rope/filament. Eruption-1's flare loops, from both TW reconnection and standard-flare-model internal reconnection, were much cooler than Eruption-2's flare loops (GOES thermal temperatures of approx. 9 MK compared to approx. 14 MK). This eruption sequence produced a strong solar energetic particle (SEP) event (10 MeV protons, >10(exp 3) pfu for 43 hrs), apparently starting when Eruption-2's CME blasted through Eruption-1's CME at 5-10 R_s. This occurred because the two CMEs originated in close proximity and in close time sequence: Eruption-1's fast rise started soon after the TW reconnection; the lid removal by Eruption-1's ejection triggered the slow onset of Eruption 2; and Eruption-2's CME, which started approx. 1 hr later, was three times faster than Eruption-1's CME.

LATERAL OFFSET OF THE CORONAL MASS EJECTIONS FROM THE X-FLARE OF 2006 DECEMBER 13 AND ITS TWO PRECURSOR ERUPTIONS

DOE Office of Scientific and Technical Information (OSTI.GOV)

Sterling, Alphonse C.; Moore, Ronald L.; Harra, Louise K., E-mail: alphonse.sterling@nasa.gov, E-mail: ron.moore@nasa.gov, E-mail: lkh@mssl.ucl.ac.uk

2011-12-10

Two GOES sub-C-class precursor eruptions occurred within {approx}10 hr prior to and from the same active region as the 2006 December 13 X4.3-class flare. Each eruption generated a coronal mass ejection (CME) with center laterally far offset ({approx}> 45 Degree-Sign ) from the co-produced bright flare. Explaining such CME-to-flare lateral offsets in terms of the standard model for solar eruptions has been controversial. Using Hinode/X-Ray Telescope (XRT) and EUV Imaging Spectrometer (EIS) data, and Solar and Heliospheric Observatory (SOHO)/Large Angle and Spectrometric Coronagraph (LASCO) and Michelson Doppler Imager (MDI) data, we find or infer the following. (1) The first precursormore » was a 'magnetic-arch-blowout' event, where an initial standard-model eruption of the active region's core field blew out a lobe on one side of the active region's field. (2) The second precursor began similarly, but the core-field eruption stalled in the side-lobe field, with the side-lobe field erupting {approx}1 hr later to make the CME either by finally being blown out or by destabilizing and undergoing a standard-model eruption. (3) The third eruption, the X-flare event, blew out side lobes on both sides of the active region and clearly displayed characteristics of the standard model. (4) The two precursors were offset due in part to the CME originating from a side-lobe coronal arcade that was offset from the active region's core. The main eruption (and to some extent probably the precursor eruptions) was offset primarily because it pushed against the field of the large sunspot as it escaped outward. (5) All three CMEs were plausibly produced by a suitable version of the standard model.« less

Forecasting Propagation and Evolution of CMEs in an Operational Setting: What Has Been Learned

NASA Technical Reports Server (NTRS)

Zheng, Yihua; Macneice, Peter; Odstrcil, Dusan; Mays, M. L.; Rastaetter, Lutz; Pulkkinen, Antti; Taktakishvili, Aleksandre; Hesse, Michael; Kuznetsova, M. Masha; Lee, Hyesook;

Forecasting propagation and evolution of CMEs in an operational setting: What has been learned

NASA Astrophysics Data System (ADS)

Zheng, Yihua; Macneice, Peter; Odstrcil, Dusan; Mays, M. L.; Rastaetter, Lutz; Pulkkinen, Antti; Taktakishvili, Aleksandre; Hesse, Michael; Masha Kuznetsova, M.; Lee, Hyesook; Chulaki, Anna

2013-10-01

of the major types of solar eruption, coronal mass ejections (CMEs) not only impact space weather, but also can have significant societal consequences. CMEs cause intense geomagnetic storms and drive fast mode shocks that accelerate charged particles, potentially resulting in enhanced radiation levels both in ions and electrons. Human and technological assets in space can be endangered as a result. CMEs are also the major contributor to generating large amplitude Geomagnetically Induced Currents (GICs), which are a source of concern for power grid safety. Due to their space weather significance, forecasting the evolution and impacts of CMEs has become a much desired capability for space weather operations worldwide. Based on our operational experience at Space Weather Research Center at NASA Goddard Space Flight Center (http://swrc.gsfc.nasa.gov), we present here some of the insights gained about accurately predicting CME impacts, particularly in relation to space weather operations. These include: 1. The need to maximize information to get an accurate handle of three-dimensional (3-D) CME kinetic parameters and therefore improve CME forecast; 2. The potential use of CME simulation results for qualitative prediction of regions of space where solar energetic particles (SEPs) may be found; 3. The need to include all CMEs occurring within a 24 h period for a better representation of the CME interactions; 4. Various other important parameters in forecasting CME evolution in interplanetary space, with special emphasis on the CME propagation direction. It is noted that a future direction for our CME forecasting is to employ the ensemble modeling approach.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Jin, M.; Manchester, W. B.; Holst, B. van der

We perform and analyze the results of a global magnetohydrodynamic simulation of the fast coronal mass ejection (CME) that occurred on 2011 March 7. The simulation is made using the newly developed Alfvén Wave Solar Model (AWSoM), which describes the background solar wind starting from the upper chromosphere and extends to 24 R {sub ⊙}. Coupling AWSoM to an inner heliosphere model with the Space Weather Modeling Framework extends the total domain beyond the orbit of Earth. Physical processes included in the model are multi-species thermodynamics, electron heat conduction (both collisional and collisionless formulations), optically thin radiative cooling, and Alfvén-wavemore » turbulence that accelerates and heats the solar wind. The Alfvén-wave description is physically self-consistent, including non-Wentzel–Kramers–Brillouin reflection and physics-based apportioning of turbulent dissipative heating to both electrons and protons. Within this model, we initiate the CME by using the Gibson-Low analytical flux rope model and follow its evolution for days, in which time it propagates beyond STEREO A . A detailed comparison study is performed using remote as well as in situ observations. Although the flux rope structure is not compared directly due to lack of relevant ejecta observation at 1 au in this event, our results show that the new model can reproduce many of the observed features near the Sun (e.g., CME-driven extreme ultraviolet [EUV] waves, deflection of the flux rope from the coronal hole, “double-front” in the white light images) and in the heliosphere (e.g., shock propagation direction, shock properties at STEREO A ).« less

Tracking Prominence Eruptions to 1 AU with STEREO Heliospheric Imaging

NASA Astrophysics Data System (ADS)

Wood, B. E.; Howard, R.; Linton, M.

2015-12-01

It is rare for prominence eruptions to be observable far from the Sun in the inner heliosphere, either in imaging or with in situ plasma instruments. Nevertheless, we here discuss two examples of particularly bright eruptions that are continuously trackable all the way to 1 AU by imagers on the Solar TErrestrial RElations Observatory (STEREO) spacecraft. The two events are from 2011 June 7 and 2012 August 31. Only these two examples of clear prominence eruptions observable this far from the Sun could be found in the STEREO 2007-2014 image database, consistent with the rarity of unambiguous cold prominence material being observed in situ at 1 AU. Full 3-D reconstructions are made of the coronal mass ejections (CMEs) that accompany the prominence eruptions. For the 2011 June event, a time-dependent 3-D reconstruction of the prominence structure is made using point-by-point triangulation, which unfortunately is not possible for the August event due to a poor viewing geometry. However, for the 2012 August event, shock normals computed from plasma measurements at STEREO-B and Wind using the shock jump conditions agree well with expectations from the image-based CME reconstruction. Unlike its accompanying CME, the 2011 June prominence exhibits little deceleration from the Sun to 1 AU, as a consequence moving upwards within the CME. Detailed analysis of the prominence's expansion reveals that deviation from self-similar expansion is never large, but close to the Sun the prominence expands somewhat more rapidly than self-similarity, with this effect decreasing with time.

Multi-spacecraft Observations of the Rotation and Nonradial Motion of a CME Flux Rope Causing an Intense Geomagnetic Storm

NASA Astrophysics Data System (ADS)

Liu, Yi A.; Liu, Ying D.; Hu, Huidong; Wang, Rui; Zhao, Xiaowei

2018-02-01

We present an investigation of the rotation and nonradial motion of a coronal mass ejection (CME) from AR 12468 on 2015 December 16 using observations from SDO, SOHO, STEREO A, and Wind. The EUV and HMI observations of the source region show that the associated magnetic flux rope (MFR) axis pointed to the east before the eruption. We use a nonlinear force-free field (NLFFF) extrapolation to determine the configuration of the coronal magnetic field and calculate the magnetic energy density distributions at different heights. The distribution of the magnetic energy density shows a strong gradient toward the northeast. The propagation direction of the CME from a Graduated Cylindrical Shell (GCS) modeling deviates from the radial direction of the source region by about 45° in longitude and about 30° in latitude, which is consistent with the gradient of the magnetic energy distribution around the AR. The MFR axis determined by the GCS modeling points southward, which has rotated counterclockwise by about 95° compared with the orientation of the MFR in the low corona. The MFR reconstructed by a Grad–Shafranov (GS) method at 1 au has almost the same orientation as the MFR from the GCS modeling, which indicates that the MFR rotation occurred in the low corona. It is the rotation of the MFR that caused the intense geomagnetic storm with the minimum D st of ‑155 nT. These results suggest that the coronal magnetic field surrounding the MFR plays a crucial role in the MFR rotation and propagation direction.

An atlas of solar events: 1996 2005

NASA Astrophysics Data System (ADS)

Artzner, G.; Auchère, F.; Delaboudinière, J. P.; Bougnet, M.

2006-01-01

Coronal mass ejections (CMEs) are observed in the plane of the sky in coronographic images. As the solar surface is masked by an occulting disk it is not clear whether halo CMEs are directed towards or away from the Earth. Observations of the solar corona on the solar disk by the extreme ultraviolet imaging telescope (EIT) on board the Solar Heliospheric Observatory SoHO can help to resolve this. Quasi-continuous observations of the solar corona were obtained from April 1997 up to the current date at a 12 min cadence in the coronal line of FeXII, as part of a “CME watch program”. At a slower 6 h cadence an additional synoptic program investigates the chromosphere and the corona at four different wavelengths. Large coronal solar events appear when viewing animations of the CME watch program. Fainter events do appear when viewing running difference animations of the CME watch program. When looking for additional spectral information from raw running differences of the synoptic program it is difficult to disentangle intrinsic solar events from the parasitic effect of the solar rotation. We constructed at www.ias.u-psud.fr/medoc/EIT/movies/ an atlas of more than 40,000 difference images from the synoptic programme, corrected for an average solar rotation, as well as more than 200,000 instantaneous and difference images from the CME watch program. We present case studies of specific events in order to investigate the source of darkenings or dimmings in difference images, due to the removal of emitting material, the presence of obscuring material or large changes in temperature. As the beneficial effect of correcting for the solar rotation vanishes at the solar limb, we do not investigate the case of prominence Doppler dimming. As a by-product of the atlas of solar events we obtain a number of quiet time sequences well suited to precisely measure the differential solar rotation by the apparent displacement of tracers.

Longitudinal Dependence of SEP Peak Intensities as Evidence of CME-Driven Shock Particle Acceleration

NASA Astrophysics Data System (ADS)

Lario, D.; Roelof, E. C.; Decker, R. B.

2014-05-01

Multi-spacecraft observations of solar energetic particle (SEP) events allow us to estimate the longitudinal distributions of SEP peak intensities. By fitting a Gaussian functional form to the ensemble of SEP peak intensities measured by two or more spacecraft as a function of the longitudinal distance between the associated parent solar flare and the footpoint labels of the magnetic field lines connecting each spacecraft with the Sun, we found that such distributions are not centered at nominal well-connected flare longitudes but slightly offset to the west of the associated flare (Lario et al. 2006, 2013). We offer an interpretation of this result in terms of long-lived particle injection from shocks driven by the associated coronal mass ejections (CMEs). By assuming that (i) CME-driven shocks are centered on the longitude of the associated solar flare, (ii) the injection of shock accelerated particles maximizes at the nose of the shock which propagates radially outward from the Sun, and (iii) SEP particle injection from the shock starts at a certain distance above the solar surface, we infer an average radial distance where shocks are located when peak intensities in the prompt component of the SEP events are observed. We estimate the heliocentric distance of the CME-driven shock when particle injection from the shock maximizes and conclude that the injection of ˜20 MeV protons and near-relativistic electrons maximizes well inside ˜0.2 AU.

Global Energetics of Several Large Solar Eruptive Events

NASA Technical Reports Server (NTRS)

Emslie, A. G.; Dennis, B. R.; Shih, A. Y.; Chamberlin, P. C.; Mewaldt, R. A.; Share, G. H.; Vourlidas, A.; Welsch, B. T.

2012-01-01

We have evaluated the energetics of 38 solar eruptive events observed by a variety of spacecraft instruments between February 2002 and December 2006, as accurately as the observations allow. The measured energetic components include: (1) the radiated energy in the GOES 1 { 8 A band; (2) the total energy radiated from the soft X-ray (SXR) emitting plasma; (3) the peak energy in the SXR-emitting plasma; (4) the bolometric radiated energy over the full duration of the event; (5) the energy in are-accelerated electrons above 20 keV and in ions above 1 MeV; (6) the kinetic and potential energies of the coronal mass ejection (CME); (7) the energy in solar energetic particles (SEPs); and (8) the amount of free (nonpotential) magnetic energy estimated to be available in the pertinent active region. Major conclusions include: (1) the energy radiated by the SXR-emitting plasma exceeds, by about half an order of magnitude, the peak energy content of the thermal plasma that produces this radiation; (2) the energy content in are-accelerated electrons and ions is sufficient to supply the bolometric energy radiated across all wavelengths throughout the event; (3) the energy contents of are-accelerated electrons and ions are comparable; (4) the energy in SEPs is typically a few percent of the CME kinetic energy (measured in the rest frame of the solar wind); and (5) the available magnetic energy is sufficient to power the CME, the are-accelerated particles, and the hot thermal plasma.

CORONAL AND CHROMOSPHERIC SIGNATURES OF LARGE-SCALE DISTURBANCES ASSOCIATED WITH A MAJOR SOLAR ERUPTION

DOE Office of Scientific and Technical Information (OSTI.GOV)

Zong, Weiguo; Dai, Yu, E-mail: ydai@nju.edu.cn

We present both coronal and chromospheric observations of large-scale disturbances associated with a major solar eruption on 2005 September 7. In the Geostationary Operational Environmental Satellites/Solar X-ray Imager (SXI), arclike coronal brightenings are recorded propagating in the southern hemisphere. The SXI front shows an initially constant speed of 730 km s{sup −1} and decelerates later on, and its center is near the central position angle of the associated coronal mass ejection (CME) but away from the flare site. Chromospheric signatures of the disturbances are observed in both Mauna Loa Solar Observatory (MLSO)/Polarimeter for Inner Coronal Studies Hα and MLSO/Chromospheric Helium Imore » Imaging Photometer He i λ10830 and can be divided into two parts. The southern signatures occur in regions where the SXI front sweeps over, with the Hα bright front coincident with the SXI front, while the He i dark front lags the SXI front but shows a similar kinematics. Ahead of the path of the southern signatures, oscillations of a filament are observed. The northern signatures occur near the equator, with the Hα and He i fronts coincident with each other. They first propagate westward and then deflect to the north at the boundary of an equatorial coronal hole. Based on these observational facts, we suggest that the global disturbances are associated with the CME lift-off and show a hybrid nature: a mainly non-wave CME flank nature for the SXI signatures and the corresponding southern chromospheric signatures, and a shocked fast-mode coronal MHD wave nature for the northern chromospheric signatures.« less

Prompt Acceleration of Magnetospheric Electrons to Ultrarelativistic Energies by the 17 March 2015 Interplanetary Shock

NASA Technical Reports Server (NTRS)

Kanekal, S. G.; Baker, D. N.; Fennell, J. F.; Jones, A.; Schiller, Q.; Richardson, I.G.; Li, X.; Turner, D. L.; Califf, S.; Claudepierre, S. G.;

Early evolution of an energetic coronal mass ejection and its relation to EUV waves

DOE Office of Scientific and Technical Information (OSTI.GOV)

Liu, Rui; Wang, Yuming; Shen, Chenglong, E-mail: rliu@ustc.edu.cn

2014-12-10

We study a coronal mass ejection (CME) associated with an X-class flare whose initiation is clearly observed in the low corona with high-cadence, high-resolution EUV images, providing us a rare opportunity to witness the early evolution of an energetic CME in detail. The eruption starts with a slow expansion of cool overlying loops (∼1 MK) following a jet-like event in the periphery of the active region. Underneath the expanding loop system, a reverse S-shaped dimming is seen immediately above the brightening active region in hot EUV passbands. The dimming is associated with a rising diffuse arch (∼6 MK), which wemore » interpret as a preexistent, high-lying flux rope. This is followed by the arising of a double hot channel (∼10 MK) from the core of the active region. The higher structures rise earlier and faster than lower ones, with the leading front undergoing extremely rapid acceleration up to 35 km s{sup –2}. This suggests that the torus instability is the major eruption mechanism and that it is the high-lying flux rope rather than the hot channels that drives the eruption. The compression of coronal plasmas skirting and overlying the expanding loop system, whose aspect ratio h/r increases with time as a result of the rapid upward acceleration, plays a significant role in driving an outward-propagating global EUV wave and a sunward-propagating local EUV wave, respectively.« less

Particle Acceleration by Cme-driven Shock Waves

NASA Technical Reports Server (NTRS)

Reames, Donald V.

1999-01-01

In the largest solar energetic particle (SEP) events, acceleration occurs at shock waves driven out from the Sun by coronal mass ejections (CMEs). Peak particle intensities are a strong function of CME speed, although the intensities, spectra, and angular distributions of particles escaping the shock are highly modified by scattering on Alfven waves produced by the streaming particles themselves. Element abundances vary in complex ways because ions with different values of Q/A resonate with different parts of the wave spectrum, which varies with space and time. Just recently, we have begun to model these systematic variations theoretically and to explore other consequences of proton-generated waves.

Blasting CME

NASA Image and Video Library

2017-12-08

This LASCO C2 image, taken 8 January 2002, shows a widely spreading coronal mass ejection (CME) as it blasts more than a billion tons of matter out into space at millions of kilometers per hour. The C2 image was turned 90 degrees so that the blast seems to be pointing down. An EIT 304 Angstrom image from a different day was enlarged and superimposed on the C2 image so that it filled the occulting disk for effect. Credit: NASA/GSFC/SOHO/ESA To learn more go to the SOHO website: sohowww.nascom.nasa.gov/home.html To learn more about NASA's Sun Earth Day go here: sunearthday.nasa.gov/2010/index.php

The Triggering of Large-Scale Waves by CME Initiation

NASA Astrophysics Data System (ADS)

Forbes, Terry

Studies of the large-scale waves generated at the onset of a coronal mass ejection (CME) can provide important information about the processes in the corona that trigger and drive CMEs. The size of the region where the waves originate can indicate the location of the magnetic forces that drive the CME outward, and the rate at which compressive waves steepen into shocks can provide a measure of how the driving forces develop in time. However, in practice it is difficult to separate the effects of wave formation from wave propagation. The problem is particularly acute for the corona because of the multiplicity of wave modes (e.g. slow versus fast MHD waves) and the highly nonuniform structure of the solar atmosphere. At the present time large-scale numerical simulations provide the best hope for deconvolving wave propagation and formation effects from one another.

WHY IS THE GREAT SOLAR ACTIVE REGION 12192 FLARE-RICH BUT CME-POOR?

DOE Office of Scientific and Technical Information (OSTI.GOV)

Sun, Xudong; Bobra, Monica G.; Hoeksema, J. Todd

Solar active region (AR) 12192 of 2014 October hosts the largest sunspot group in 24 years. It is the most prolific flaring site of Cycle 24 so far, but surprisingly produced no coronal mass ejection (CME) from the core region during its disk passage. Here, we study the magnetic conditions that prevented eruption and the consequences that ensued. We find AR 12192 to be “big but mild”; its core region exhibits weaker non-potentiality, stronger overlying field, and smaller flare-related field changes compared to two other major flare-CME-productive ARs (11429 and 11158). These differences are present in the intensive-type indices (e.g.,more » means) but generally not the extensive ones (e.g., totals). AR 12192's large amount of magnetic free energy does not translate into CME productivity. The unexpected behavior suggests that AR eruptiveness is limited by some relative measure of magnetic non-potentiality over the restriction of background field, and that confined flares may leave weaker photospheric and coronal imprints compared to their eruptive counterparts.« less

Development of a Full Ice-cream Cone Model for Halo Coronal Mass Ejections

NASA Astrophysics Data System (ADS)

Na, Hyeonock; Moon, Y.-J.; Lee, Harim

2017-04-01

It is essential to determine three-dimensional parameters (e.g., radial speed, angular width, and source location) of coronal mass ejections (CMEs) for the space weather forecast. In this study, we investigate which cone type represents a halo CME morphology using 29 CMEs (12 Solar and Heliospheric Observatory (SOHO)/Large Angle and Spectrometric Coronagraph (LASCO) halo CMEs and 17 Solar Terrestrial Relations Observatory (STEREO)/Sun-Earth Connection Coronal and Heliospheric Investigation COR2 halo CMEs) from 2010 December to 2011 June. These CMEs are identified as halo CMEs by one spacecraft (SOHO or one of STEREO A and B) and limb ones by the other spacecraft (One of STEREO A and B or SOHO). From cone shape parameters of these CMEs, such as their front curvature, we find that the CME observational structures are much closer to a full ice-cream cone type than a shallow ice-cream cone type. Thus, we develop a full ice-cream cone model based on a new methodology that the full ice-cream cone consists of many flat cones with different heights and angular widths to estimate the three-dimensional parameters of the halo CMEs. This model is constructed by carrying out the following steps: (1) construct a cone for a given height and angular width, (2) project the cone onto the sky plane, (3) select points comprising the outer boundary, and (4) minimize the difference between the estimated projection speeds with the observed ones. By applying this model to 12 SOHO/LASCO halo CMEs, we find that 3D parameters from our method are similar to those from other stereoscopic methods (I.e., a triangulation method and a Graduated Cylindrical Shell model).

Development of a Full Ice-cream Cone Model for Halo Coronal Mass Ejections

DOE Office of Scientific and Technical Information (OSTI.GOV)

Na, Hyeonock; Moon, Y.-J.; Lee, Harim, E-mail: nho0512@khu.ac.kr, E-mail: moonyj@khu.ac.kr

It is essential to determine three-dimensional parameters (e.g., radial speed, angular width, and source location) of coronal mass ejections (CMEs) for the space weather forecast. In this study, we investigate which cone type represents a halo CME morphology using 29 CMEs (12 Solar and Heliospheric Observatory (SOHO) /Large Angle and Spectrometric Coronagraph (LASCO) halo CMEs and 17 Solar Terrestrial Relations Observatory ( STEREO )/Sun–Earth Connection Coronal and Heliospheric Investigation COR2 halo CMEs) from 2010 December to 2011 June. These CMEs are identified as halo CMEs by one spacecraft ( SOHO or one of STEREO A and B ) and limbmore » ones by the other spacecraft (One of STEREO A and B or SOHO ). From cone shape parameters of these CMEs, such as their front curvature, we find that the CME observational structures are much closer to a full ice-cream cone type than a shallow ice-cream cone type. Thus, we develop a full ice-cream cone model based on a new methodology that the full ice-cream cone consists of many flat cones with different heights and angular widths to estimate the three-dimensional parameters of the halo CMEs. This model is constructed by carrying out the following steps: (1) construct a cone for a given height and angular width, (2) project the cone onto the sky plane, (3) select points comprising the outer boundary, and (4) minimize the difference between the estimated projection speeds with the observed ones. By applying this model to 12 SOHO /LASCO halo CMEs, we find that 3D parameters from our method are similar to those from other stereoscopic methods (i.e., a triangulation method and a Graduated Cylindrical Shell model).« less

Inflows in the Inner White-light Corona: The Closing-down of Flux after Coronal Mass Ejections

NASA Astrophysics Data System (ADS)

Hess, P.; Wang, Y.-M.

2017-11-01

During times of high solar activity, the Solar and Heliospheric Observatory/Large Angle and Spectrometric Coronagraph C2 coronagraph has recorded multitudes of small features moving inward through its 2{--}6 {R}⊙ field of view. These outer-coronal inflows, which are concentrated around the heliospheric current sheet, tend to be poorly correlated with individual coronal mass ejection (CME) events. Using running-difference movies constructed from Solar Terrestrial Relations Observatory/COR1 coronagraph images taken during 2008-2014, we have identified large numbers of inward-moving features at heliocentric distances below 2 {R}⊙ , with the rate increasing with sunspot and CME activity. Most of these inner-coronal inflows are closely associated with CMEs, being observed during and in the days immediately following the eruptions. Here, we describe several examples of the pinching-off of tapered streamer structures in the wake of CMEs. This type of inflow event is characterized by a separation of the flow into incoming and outgoing components connected by a thin spike, which is interpreted as a continually elongating current sheet viewed edge-on; by the prior convergence of narrow rays toward the current sheet; and by a succession of collapsing loops that form a cusp-shaped structure at the base of the current sheet. The re-forming streamer overlies a growing post-eruption arcade that is visible in EUV images. These observations provide support for standard reconnection models for the formation/evolution of flux ropes during solar eruptive events. We suggest that inflow streams that occur over a relatively wide range of position angles result from the pinching-off of loop arcades whose axes are oriented parallel rather than perpendicular to the sky plane.

Quasi-periodic Fast-mode Wave Trains Within a Global EUV Wave and Sequential Transverse Oscillations Detected by SDO-AIA

NASA Technical Reports Server (NTRS)

Liu, Wei; Ofman, Leon; Nitta, Nariaki; Aschwanden, Markus J.; Schrijver, Carolus J.; Title, Alan M.; Tarbell, Theodore D.

2012-01-01

We present the first unambiguous detection of quasi-periodic wave trains within the broad pulse of a global EUV wave (so-called EIT wave) occurring on the limb. These wave trains, running ahead of the lateral coronal mass ejection (CME) front of 2-4 times slower, coherently travel to distances greater than approximately solar radius/2 along the solar surface, with initial velocities up to 1400 kilometers per second decelerating to approximately 650 kilometers per second. The rapid expansion of the CME initiated at an elevated height of 110 Mm produces a strong downward and lateral compression, which may play an important role in driving the primary EUV wave and shaping its front forwardly inclined toward the solar surface. The wave trains have a dominant 2 minute periodicity that matches the X-ray flare pulsations, suggesting a causal connection. The arrival of the leading EUV wave front at increasing distances produces an uninterrupted chain sequence of deflections and/or transverse (likely fast kink mode) oscillations of local structures, including a flux-rope coronal cavity and its embedded filament with delayed onsets consistent with the wave travel time at an elevated (by approximately 50%) velocity within it. This suggests that the EUV wave penetrates through a topological separatrix surface into the cavity, unexpected from CME-caused magnetic reconfiguration. These observations, when taken together, provide compelling evidence of the fast-mode MHD wave nature of the primary (outer) fast component of a global EUV wave, running ahead of the secondary (inner) slow component of CME-caused restructuring.

Observational properties of decameter type IV bursts

NASA Astrophysics Data System (ADS)

Melnik, Valentin; Brazhenko, Anatoly; Rucker, Helmut; Konovalenko, Alexander; Briand, Carine; Dorovskyy, Vladimir; Zarka, Philippe; Frantzusenko, Anatoly; Panchenko, Michael; Poedts, Stefan; Zaqarashvili, Teimuraz; Shergelashvili, Bidzina

2013-04-01

Oscillations of decameter type IV bursts were registered during observations of solar radio emission by UTR-2, URAN-2 and NDA in 2011-2012. Large majority of these bursts were accompanied by coronal mass ejections (CMEs), which were observed by SOHO and STEREO in the visible light. Only in some cases decameter type IV bursts were not associated with CMEs. The largest periods of oscillations P were some tens of minutes. There were some modes of long periods of oscillations simultaneously. Periods of oscillations in flux and in polarization profiles were close. Detailed properties of oscillations at different frequencies were analyzed on the example of two type IV bursts. One of them was observed on April 7, 2011 when a CME happened. Another one (August 1, 2011) was registered without any CME. The 7 April type IV burst had two periods in the frames 75-85 and 35-85 minutes. Interesting feature of these oscillations is decreasing periods with time. The observed decreasing rates dP/dt equaled 0.03-0.07. Concerning type IV burst observed on August 1, 2011 the period of its oscillations increases from 17 min. at 30 MHz to 44 min. at 10 MHz. Connection of type IV burst oscillations with oscillations of magnetic arches and CMEs at corresponding altitudes are discussed. The work is fulfilled in the frame of FP7 project "SOLSPANET".

Modeling Coronal Mass Ejections with EUHFORIA: A Parameter Study of the Gibson-Low Flux Rope Model using Multi-Viewpoint Observations

NASA Astrophysics Data System (ADS)

Verbeke, C.; Asvestari, E.; Scolini, C.; Pomoell, J.; Poedts, S.; Kilpua, E.

2017-12-01

Coronal Mass Ejections (CMEs) are one of the big influencers on the coronal and interplanetary dynamics. Understanding their origin and evolution from the Sun to the Earth is crucial in order to determine the impact on our Earth and society. One of the key parameters that determine the geo-effectiveness of the coronal mass ejection is its internal magnetic configuration. We present a detailed parameter study of the Gibson-Low flux rope model. We focus on changes in the input parameters and how these changes affect the characteristics of the CME at Earth. Recently, the Gibson-Low flux rope model has been implemented into the inner heliosphere model EUHFORIA, a magnetohydrodynamics forecasting model of large-scale dynamics from 0.1 AU up to 2 AU. Coronagraph observations can be used to constrain the kinematics and morphology of the flux rope. One of the key parameters, the magnetic field, is difficult to determine directly from observations. In this work, we approach the problem by conducting a parameter study in which flux ropes with varying magnetic configurations are simulated. We then use the obtained dataset to look for signatures in imaging observations and in-situ observations in order to find an empirical way of constraining the parameters related to the magnetic field of the flux rope. In particular, we focus on events observed by at least two spacecraft (STEREO + L1) in order to discuss the merits of using observations from multiple viewpoints in constraining the parameters.

Magnetic Evolution Linked to the Interrelated Activity Complexes Involving Transequatorial Coronal Holes

NASA Astrophysics Data System (ADS)

Gutiérrez, Heidy; Taliashvili, Lela; Lazarian, Alexandre

2018-06-01

We studied a magnetic evolution linked to a cadence of interrelated activities developed in a large solar region during Carrington rotations, CRs 2119 - 2121, based on multi-wavelength and multi-spacecraft observations. Three coronal holes (CHs), two transequatorial and one isolated, eight filaments and some active regions were distributed closely in the region. Every of these filaments partial and/or complete eruption was linked to a Coronal Mass Ejection (CME) or coronal jet. We found different types of interrelated activities: eruptions of three pairs of interrelated filaments close to a CH and eruptions of two filaments close to the active region and CH. Some indicators of the magnetic reconnection were observed frequently during the pre- as well as post-filament eruptions. Additionally, post-filament eruption and/or post-CME processes show their implication in the evolution of nearby CHs and newly formed transient CHs or dimming regions, including a new CH formation. We discussed the small- and large-scale magnetic reconfigurations associated with these interrelated activity complexes, the ones involving long-lived transequatorial CHs, and their possible implication in the evolution of the global solar magnetic field, especially with the starting processes of quadruple configuration and polarity reversal of the solar cycle 24.

Studying the Kinematic Behavior of Coronal Mass Ejections and Other Solar Phenomena using the Time-Convolution Mapping Method

NASA Astrophysics Data System (ADS)

Hess Webber, Shea A.; Thompson, Barbara J.; Kwon, Ryun Young; Ireland, Jack

2018-01-01

An improved understanding of the kinematic properties of CMEs and CME-associated phenomena has several impacts: 1) a less ambiguous method of mapping propagating structures into their inner coronal manifestations, 2) a clearer view of the relationship between the “main” CME and CME-associated brightenings, and 3) an improved identification of the heliospheric sources of shocks, Type II bursts, and SEPs. We present the results of a mapping technique that facilitates the separation of CMEs and CME-associated brightenings (such as shocks) from background corona. The Time Convolution Mapping Method (TCMM) segments coronagraph data to identify the time history of coronal evolution, the advantage being that the spatiotemporal evolution profiles allow users to separate features with different propagation characteristics. For example, separating “main” CME mass from CME-associated brightenings or shocks is a well-known obstacle, which the TCMM aids in differentiating. A TCMM CME map is made by first recording the maximum value each individual pixel in the image reaches during the traversal of the CME. Then the maximum value is convolved with an index to indicate the time that the pixel reached that value. The TCMM user is then able to identify continuous “kinematic profiles,” indicating related kinematic behavior, and also identify breaks in the profiles that indicate a discontinuity in kinematic history (i.e. different structures or different propagation characteristics). The maps obtained from multiple spacecraft viewpoints (i.e., STEREO and SOHO) can then be fit with advanced structural models to obtain the 3D properties of the evolving phenomena. We will also comment on the TCMM's further applicability toward the tracking of prominences, coronal hole boundaries and coronal cavities.

PROBABILITY OF CME IMPACT ON EXOPLANETS ORBITING M DWARFS AND SOLAR-LIKE STARS

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kay, C.; Opher, M.; Kornbleuth, M., E-mail: ckay@bu.edu

2016-08-01

Solar coronal mass ejections (CMEs) produce adverse space weather effects at Earth. Planets in the close habitable zone of magnetically active M dwarfs may experience more extreme space weather than at Earth, including frequent CME impacts leading to atmospheric erosion and leaving the surface exposed to extreme flare activity. Similar erosion may occur for hot Jupiters with close orbits around solar-like stars. We have developed a model, Forecasting a CME's Altered Trajectory (ForeCAT), which predicts a CME's deflection. We adapt ForeCAT to simulate CME deflections for the mid-type M dwarf V374 Peg and hot Jupiters with solar-type hosts. V374 Peg'smore » strong magnetic fields can trap CMEs at the M dwarfs's Astrospheric Current Sheet, that is, the location of the minimum in the background magnetic field. Solar-type CMEs behave similarly, but have much smaller deflections and do not become trapped at the Astrospheric Current Sheet. The probability of planetary impact decreases with increasing inclination of the planetary orbit with respect to the Astrospheric Current Sheet: 0.5–5 CME impacts per day for M dwarf exoplanets, 0.05–0.5 CME impacts per day for solar-type hot Jupiters. We determine the minimum planetary magnetic field necessary to shield a planet's atmosphere from CME impacts. M dwarf exoplanets require values between tens and hundreds of Gauss. Hot Jupiters around a solar-type star, however, require a more reasonable <30 G. These values exceed the magnitude required to shield a planet from the stellar wind, suggesting that CMEs may be the key driver of atmospheric losses.« less

Comet Plunge and CME on the Sun

NASA Image and Video Library

2017-12-08

A small comet was streaking towards the Sun when the Sun blew out a "halo" coronal mass ejection (CME) Aug. 19-20, 2013). The CME originated from the far side of the Sun and did not have any interaction with the comet. The comet, only perhaps 30 meters across, was not seen after it went out of view, likely disintegrated by the heat and radiation from the Sun. We call this a "full halo" CME since the front edge of the CME is expanding in all directions around the Sun like a halo. The images were taken by SOHO's coronagraphs in which a disk (red) blocks the Sun and some of the area around it so we can see faint structures beyond that. Here we superimposed the Sun from NASA's SDO. The movie covers about five hours of activity and can be seen here: www.flickr.com/photos/gsfc/9601034896/ Credit: NASA/Goddard/SOHO NASA image use policy. NASA Goddard Space Flight Center enables NASA’s mission through four scientific endeavors: Earth Science, Heliophysics, Solar System Exploration, and Astrophysics. Goddard plays a leading role in NASA’s accomplishments by contributing compelling scientific knowledge to advance the Agency’s mission. Follow us on Twitter Like us on Facebook Find us on Instagram

Coronal mass ejection (CME) activity of low mass M stars as an important factor for the habitability of terrestrial exoplanets. II. CME-induced ion pick up of Earth-like exoplanets in close-in habitable zones.

PubMed

Lammer, Helmut; Lichtenegger, Herbert I M; Kulikov, Yuri N; Griessmeier, Jean-Mathias; Terada, N; Erkaev, Nikolai V; Biernat, Helfried K; Khodachenko, Maxim L; Ribas, Ignasi; Penz, Thomas; Selsis, Franck

2007-02-01

Atmospheric erosion of CO2-rich Earth-size exoplanets due to coronal mass ejection (CME)-induced ion pick up within close-in habitable zones of active M-type dwarf stars is investigated. Since M stars are active at the X-ray and extreme ultraviolet radiation (XUV) wave-lengths over long periods of time, we have applied a thermal balance model at various XUV flux input values for simulating the thermospheric heating by photodissociation and ionization processes due to exothermic chemical reactions and cooling by the CO2 infrared radiation in the 15 microm band. Our study shows that intense XUV radiation of active M stars results in atmospheric expansion and extended exospheres. Using thermospheric neutral and ion densities calculated for various XUV fluxes, we applied a numerical test particle model for simulation of atmospheric ion pick up loss from an extended exosphere arising from its interaction with expected minimum and maximum CME plasma flows. Our results indicate that the Earth-like exoplanets that have no, or weak, magnetic moments may lose tens to hundreds of bars of atmospheric pressure, or even their whole atmospheres due to the CME-induced O ion pick up at orbital distances

ANATOMY OF DEPLETED INTERPLANETARY CORONAL MASS EJECTIONS

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kocher, M.; Lepri, S. T.; Landi, E.

We report a subset of interplanetary coronal mass ejections (ICMEs) containing distinct periods of anomalous heavy-ion charge state composition and peculiar ion thermal properties measured by ACE /SWICS from 1998 to 2011. We label them “depleted ICMEs,” identified by the presence of intervals where C{sup 6+}/C{sup 5+} and O{sup 7+}/O{sup 6+} depart from the direct correlation expected after their freeze-in heights. These anomalous intervals within the depleted ICMEs are referred to as “Depletion Regions.” We find that a depleted ICME would be indistinguishable from all other ICMEs in the absence of the Depletion Region, which has the defining property ofmore » significantly low abundances of fully charged species of helium, carbon, oxygen, and nitrogen. Similar anomalies in the slow solar wind were discussed by Zhao et al. We explore two possibilities for the source of the Depletion Region associated with magnetic reconnection in the tail of a CME, using CME simulations of the evolution of two Earth-bound CMEs described by Manchester et al.« less

A spectacular coronal mass ejection event and associated phenomena

NASA Astrophysics Data System (ADS)

Ma, Yuan; Li, Chun-Sheng; Song, Qian

Based on the data taken from S. G. D. and relevant simultaneous observations of solar radio bursts, gamma-ray emission and geophysical effects on June 15, 1991 the relationships among these phenomena are discussed in this paper. Through the analyses it is considered that proton events and GLE events occurred on June 15 in 1991, which were the geophysic responses caused by CME (V>=750 km/s). Simultaneous observation of the bursts at the centimetric and decimetric wavelengths can obtain the U-shape spectrum of speak fluxes, which is still one of the effective tools for predicting proton events and its production mechanism can be explained by using the acceleration of the direct current field parallel to the magnetic field in the electric current sheet formed in the process of the production of spray prominences. However, the process in which electrons are accelerated up to the high energy state remains to be explained. The whole event of June 15 1991, from the coronal matter ejection (or the spray prominences in active regions) to the production of various geophysic effects, has explained and verified.

Heliospheric Imaging of 3D Density Structures During the Multiple Coronal Mass Ejections of Late July to Early August 2010

NASA Astrophysics Data System (ADS)

Webb, D. F.; Möstl, C.; Jackson, B. V.; Bisi, M. M.; Howard, T. A.; Mulligan, T.; Jensen, E. A.; Jian, L. K.; Davies, J. A.; de Koning, C. A.; Liu, Y.; Temmer, M.; Clover, J. M.; Farrugia, C. J.; Harrison, R. A.; Nitta, N.; Odstrcil, D.; Tappin, S. J.; Yu, H.-S.

2013-07-01

It is usually difficult to gain a consistent global understanding of a coronal mass ejection (CME) eruption and its propagation when only near-Sun imagery and the local measurements derived from single-spacecraft observations are available. Three-dimensional (3D) density reconstructions based on heliospheric imaging allow us to "fill in" the temporal and spatial gaps between the near-Sun and in situ data to provide a truly global picture of the propagation and interactions of the CME as it moves through the inner heliosphere. In recent years the heliospheric propagation of dense structures has been observed and measured by the heliospheric imagers of the Solar Mass Ejection Imager (SMEI) and on the twin Solar TErrestrial RElations Observatory (STEREO) spacecraft. We describe the use of several 3D reconstruction techniques based on these heliospheric imaging data sets to distinguish and track the propagation of multiple CMEs in the inner heliosphere during the very active period of solar activity in late July - early August 2010. We employ 3D reconstruction techniques used at the University of California, San Diego (UCSD) based on a kinematic solar wind model, and also the empirical Tappin-Howard model. We compare our results with those from other studies of this active period, in particular the heliospheric simulations made with the ENLIL model by Odstrcil et al. ( J. Geophys. Res., 2013) and the in situ results from multiple spacecraft provided by Möstl et al. ( Astrophys. J. 758, 10 - 28, 2012). We find that the SMEI results in particular provide an overall context for the multiple-density flows associated with these CMEs. For the first time we are able to intercompare the 3D reconstructed densities with the timing and magnitude of in situ density structures at five spacecraft spread over 150° in ecliptic longitude and from 0.4 to 1 AU in radial distance. We also model the magnetic flux-rope structures at three spacecraft using both force-free and non-force-free modelling, and compare their timing and spatial structure with the reconstructed density flows.

Modeling of coronal mass ejections with the STEREO heliospheric imagers verified with in situ observations by the Heliophysics System Observatory

NASA Astrophysics Data System (ADS)

Möstl, Christian; Isavnin, Alexey; Kilpua, Emilia; Bothmer, Volker; Mrotzek, Nicolas; Boakes, Peter; Rodriguez, Luciano; Krupar, Vratislav; Eastwood, Jonathan; Davies, Jackie; Harrison, Richard; Barnes, David; Winslow, Reka; Helcats Team

2017-04-01

We present the first study to verify modeling of CMEs as observed by the heliospheric imagers on the two STEREO spacecraft with a large scale dataset of in situ plasma and magnetic field observations from the Heliophysics System Observatory, including MESSENGER, VEX, Wind, and the in situ measurements on the two STEREO spacecraft. To this end, we have established a new interplanetary CME catalog (ICMECAT) for these spacecraft by gathering and updating individual ICME lists. In addition, we have re-calculated the in situ parameters in a consistent way, resulting in 668 events observed between 2007-2015. We then calculated the efficacy of the STEREO/HI instruments for predicting (in hindsight) with the SSEF30 model the arrival time and speed of CMEs as well as hit/miss ratios. We also show how ICMECAT gives decent statistics concerning CME impacts on all of the terrestrial planets, including Mars. The results show some major implications for future heliospheric imagers which may be used for space weather forecasting. Our effort should also serve as a baseline for the upcoming new era in heliospheric science with Solar Orbiter, Solar Probe Plus, BepiColombo returning partly comparable observations in the next decade. The presented work has received funding from the European Union Seventh Framework Programme (FP7/ 2007-2013) under grant agreement No. 606692 [HELCATS].

Mass-Loss Evolution in the EUV Low Corona from SDO/AIA Data

NASA Astrophysics Data System (ADS)

López, Fernando M.; Hebe Cremades, M.; Nuevo, Federico A.; Balmaceda, Laura A.; Vásquez, Alberto M.

2017-01-01

We carry out an analysis of the mass that is ejected from three coronal dimming regions observed by the Atmospheric Imaging Assembly (AIA) on board the Solar Dynamics Observatory. The three events are unambiguously identified with white-light coronal mass ejections (CMEs) that are associated in turn with surface activity of diverse nature: an impulsive (M-class) flare, a weak (B-class) flare, and a filament eruption without a flare. The use of three AIA coronal passbands allows applying a differential emission measure technique to define the dimming regions and identify their ejected mass through the analysis of the electronic density depletion associated with the eruptions. The temporal evolution of the mass loss from the three dimmings can be approximated by an exponential equation followed by a linear fit. We determine the mass of the associated CMEs from COR2 data. The results show that the ejected masses from the low corona represent a considerable amount of the CME mass. We also find that plasma is still being ejected from the low corona at the time when the CMEs reach the COR2 field of view. The temporal evolution of the angular width of the CMEs, of the dimming regions in the low corona, and of the flux registered by GOES in soft X-rays are all in close relation with the behavior of mass ejection from the low corona. We discuss the implications of our findings toward a better understanding of the temporal evolution of several parameters associated with the analyzed dimmings and CMEs.

The Effect on the Lunar Exosphere of a Coroual Mass Ejection Passage

NASA Technical Reports Server (NTRS)

Killen, R. M.; Hurley, D. M.; Farrell, W. M.

2011-01-01

Solar wind bombardment onto exposed surfaces in the solar system produces an energetic component to the exospheres about those bodies. The solar wind energy and composition are highly dependent on the origin of the plasma. Using the measured composition of the slow wind, fast wind, solar energetic particle (SEP) population, and coronal mass ejection (CME), broken down into their various components, we have estimated the total sputter yield for each type of solar wind. We show that the heavy ion component, especially the He++ and 0+7 can greatly enhance the total sputter yield during times when the heavy ion population is enhanced. Folding in the flux, we compute the source rate for several species during different types of solar wind. Finally, we use a Monte Carlo model developed to simulate the time-dependent evolution of the lunar exosphere to study the sputtering component of the exosphere under the influence of a CME passage. We simulate the background exosphere of Na, K, Ca, and Mg. Simulations indicate that sputtering increases the mass of those constituents in the exosphere a few to a few tens times the background values. The escalation of atmospheric density occurs within an hour of onset The decrease in atmospheric density after the CME passage is also rapid, although takes longer than the increase, Sputtered neutral particles have a high probability of escaping the moon,by both Jeans escape and photo ionization. Density and spatial distribution of the exosphere can be tested with the LADEE mission.

TRIGGER OF A BLOWOUT JET IN A SOLAR CORONAL MASS EJECTION ASSOCIATED WITH A FLARE

DOE Office of Scientific and Technical Information (OSTI.GOV)

Li, Xiaohong; Yang, Shuhong; Chen, Huadong

2015-11-20

Using the multi-wavelength images and the photospheric magnetograms from the Solar Dynamics Observatory, we study the flare that was associated with the only coronal mass ejection (CME) in active region (AR) 12192. The eruption of a filament caused a blowout jet, and then an M4.0 class flare occurred. This flare was located at the edge of the AR instead of in the core region. The flare was close to the apparently “open” fields, appearing as extreme-ultraviolet structures that fan out rapidly. Due to the interaction between flare materials and “open” fields, the flare became an eruptive flare, leading to themore » CME. Then, at the same site of the first eruption, another small filament erupted. With the high spatial and temporal resolution Hα data from the New Vacuum Solar Telescope at the Fuxian Solar Observatory, we investigate the interaction between the second filament and the nearby “open” lines. The filament reconnected with the “open” lines, forming a new system. To our knowledge, the detailed process of this kind of interaction is reported for the first time. Then the new system rotated due to the untwisting motion of the filament, implying that the twist was transferred from the closed filament system to the “open” system. In addition, the twist seemed to propagate from the lower atmosphere to the upper layers and was eventually spread by the CME to the interplanetary space.« less

Triennial Report 2006-2009. Commission 10: Solar Activity

NASA Technical Reports Server (NTRS)

Klimchuk, James A.

2008-01-01

Commission 10 deals with solar activity in all of its forms, ranging from the smallest nanoflares to the largest coronal mass ejections. This report reviews scientific progress over the roughly two-year period ending in the middle of 2008. This has been an exciting time in solar physics, highlighted by the launches of the Hinode and STEREO missions late in 2006. The report is reasonably comprehensive, though it is far from exhaustive. Limited space prevents the inclusion of many significant results. The report is divided into following sections: Photosphere and Chromosphere; Transition Region; Corona and Coronal Heating; Coronal Jets; Flares; Coronal Mass Ejection Initiation; Global Coronal Waves and Shocks; Coronal Dimming; The Link Between Low Coronal CME signatures and Magnetic Clouds; Coronal Mass Ejections in the Heliosphere; and Coronal Mass Ejections and Space Weather. Primary authorship is indicated at the beginning of each section.

The Magnetic Free Energy in Active Regions

NASA Technical Reports Server (NTRS)

Metcalf, Thomas R.; Mickey, Donald L.; LaBonte, Barry J.

2001-01-01

The magnetic field permeating the solar atmosphere governs much of the structure, morphology, brightness, and dynamics observed on the Sun. The magnetic field, especially in active regions, is thought to provide the power for energetic events in the solar corona, such as solar flares and Coronal Mass Ejections (CME) and is believed to energize the hot coronal plasma seen in extreme ultraviolet or X-rays. The question remains what specific aspect of the magnetic flux governs the observed variability. To directly understand the role of the magnetic field in energizing the solar corona, it is necessary to measure the free magnetic energy available in active regions. The grant now expiring has demonstrated a new and valuable technique for observing the magnetic free energy in active regions as a function of time.

Kinematic properties of solar coronal mass ejections: Correction for projection effects in spacecraft coronagraph measurements

NASA Astrophysics Data System (ADS)

Howard, T. A.; Nandy, D.; Koepke, A. C.

2008-01-01

One of the main sources of uncertainty in quantifying the kinematic properties of coronal mass ejections (CMEs) using coronagraphs is the fact that coronagraph images are projected into the sky plane, resulting in measurements which can differ significantly from their actual values. By identifying solar surface source regions of CMEs using X-ray and Hα flare and disappearing filament data, and through considerations of CME trajectories in three-dimensional (3-D) geometry, we have devised a methodology to correct for the projection effect. We outline this method here. The methodology was automated and applied to over 10,000 CMEs in the Coordinated Data Analysis Workshop (CDAW) (SOHO Large Angle Spectroscopic Coronagraph) catalog spanning 1996-2005, in which we could associate 1961 CMEs with an appropriate surface event. In the latter subset, deprojected speeds, accelerations, and launch angles were determined to study CME kinematics. Our analysis of this subset of events reconfirms some important trends, notably that previously uncovered solar cycle variation of CME properties are preserved, CMEs with greater width have higher speeds, and slower CMEs tend to accelerate while faster CMEs tend to decelerate. This points out that statistical trends in CME properties, recovered from plane-of-sky measurements, may be preserved even in the face of more sophisticated 3-D measurements from spacecrafts such as STEREO, if CME trajectories are predominantly radial. However, our results also show that the magnitude of corrected measurements can differ significantly from the projected plane-of-sky measurements on a case-by-case basis and that acceleration is more sensitive to the deprojection process than speed. Average corrected speed and acceleration tend to be a factor of 1.7 and 4.4 higher than their projected values, with mean corrected speed and acceleration magnitudes being on the order of 1000 km/s and 50 m/s2, respectively. We conclude that while using the plane-of-sky measurements may be suitable for studies of general trends in a large sample of events, correcting for projection effects is mandatory for those investigations which rely on a numerically precise determination of the properties of individual CMEs.

Prediction of Active-Region CME Productivity from Magnetograms

NASA Technical Reports Server (NTRS)

Falconer, D. A.; Moore, R. L.; Gary, G. A.

2004-01-01

We report results of an expanded evaluation of whole-active-region magnetic measures as predictors of active-region coronal mass ejection (CME) productivity. Previously, in a sample of 17 vector magnetograms of 12 bipolar active regions observed by the Marshall Space Flight Center (MSFC) vector magnetograph, from each magnetogram we extracted a measure of the size of the active region (the active region s total magnetic flux a) and four measures of the nonpotentiality of the active region: the strong-shear length L(sub SS), the strong-gradient length L(sub SG), the net vertical electric current I(sub N), and the net-current magnetic twist parameter alpha (sub IN). This sample size allowed us to show that each of the four nonpotentiality measures was statistically significantly correlated with active-region CME productivity in time windows of a few days centered on the day of the magnetogram. We have now added a fifth measure of active-region nonpotentiality (the best-constant-alpha magnetic twist parameter (alpha sub BC)), and have expanded the sample to 36 MSFC vector magnetograms of 31 bipolar active regions. This larger sample allows us to demonstrate statistically significant correlations of each of the five nonpotentiality measures with future CME productivity, in time windows of a few days starting from the day of the magnetogram. The two magnetic twist parameters (alpha (sub 1N) and alpha (sub BC)) are normalized measures of an active region s nonpotentially in that they do not depend directly on the size of the active region, while the other three nonpotentiality measures (L(sub SS), L(sub SG), and I(sub N)) are non-normalized measures in that they do depend directly on active-region size. We find (1) Each of the five nonpotentiality measures is statistically significantly correlated (correlation confidence level greater than 95%) with future CME productivity and has a CME prediction success rate of approximately 80%. (2) None of the nonpotentiality measures is a significantly better CME predictor than the others. (3) The active-region phi shows some correlation with CME productivity, but well below a statistically significant level (correlation confidence level less than approximately 80%; CME prediction success rate less than approximately 65%). (4) In addition to depending on magnetic twist, CME productivity appears to have some direct dependence on active-region size (rather than only an indirect dependence through a correlation of magnetic twist with active-region size), but it will take a still larger sample of active regions (50 or more) to certify this. (5) Of the five nonpotentiality measures, L(sub SG) appears to be the best for operational CME forecasting because it is as good or better a CME predictor than the others and it alone does not require a vector magnetogram; L(sub SG) can be measured from a line-of-sight magnetogram such as from the Michelson Doppler Imager (MDI) on the Solar and Heliospheric Observatory (SOHO).

Demonstration of a viable quantitative theory for interplanetary type II radio bursts

DOE Office of Scientific and Technical Information (OSTI.GOV)

Schmidt, J. M., E-mail: jschmidt@physics.usyd.edu.au; Cairns, Iver H.

Between 29 November and 1 December 2013 the two widely separated spacecraft STEREO A and B observed a long lasting, intermittent, type II radio burst for the extended frequency range ≈ 4 MHz to 30 kHz, including an intensification when the shock wave of the associated coronal mass ejection (CME) reached STEREO A. We demonstrate for the first time our ability to quantitatively and accurately simulate the fundamental (F) and harmonic (H) emission of type II bursts from the higher corona (near 11 solar radii) to 1 AU. Our modeling requires the combination of data-driven three-dimensional magnetohydrodynamic simulations for the CME andmore » plasma background, carried out with the BATS-R-US code, with an analytic quantitative kinetic model for both F and H radio emission, including the electron reflection at the shock, growth of Langmuir waves and radio waves, and the radiations propagation to an arbitrary observer. The intensities and frequencies of the observed radio emissions vary hugely by factors ≈ 10{sup 6} and ≈ 10{sup 3}, respectively; the theoretical predictions are impressively accurate, being typically in error by less than a factor of 10 and 20 %, for both STEREO A and B. We also obtain accurate predictions for the timing and characteristics of the shock and local radio onsets at STEREO A, the lack of such onsets at STEREO B, and the z-component of the magnetic field at STEREO A ahead of the shock, and in the sheath. Very strong support is provided by these multiple agreements for the theory, the efficacy of the BATS-R-US code, and the vision of using type IIs and associated data-theory iterations to predict whether a CME will impact Earth’s magnetosphere and drive space weather events.« less

AVERAGE SPATIAL DISTRIBUTION OF COSMIC RAYS BEHIND THE INTERPLANETARY SHOCK—GLOBAL MUON DETECTOR NETWORK OBSERVATIONS

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kozai, M.; Munakata, K.; Kato, C.

2016-07-10

We analyze the galactic cosmic ray (GCR) density and its spatial gradient in Forbush Decreases (FDs) observed with the Global Muon Detector Network (GMDN) and neutron monitors (NMs). By superposing the GCR density and density gradient observed in FDs following 45 interplanetary shocks (IP-shocks), each associated with an identified eruption on the Sun, we infer the average spatial distribution of GCRs behind IP-shocks. We find two distinct modulations of GCR density in FDs, one in the magnetic sheath and the other in the coronal mass ejection (CME) behind the sheath. The density modulation in the sheath is dominant in themore » western flank of the shock, while the modulation in the CME ejecta stands out in the eastern flank. This east–west asymmetry is more prominent in GMDN data responding to ∼60 GV GCRs than in NM data responding to ∼10 GV GCRs, because of the softer rigidity spectrum of the modulation in the CME ejecta than in the sheath. The geocentric solar ecliptic- y component of the density gradient, G {sub y}, shows a negative (positive) enhancement in FDs caused by the eastern (western) eruptions, while G {sub z} shows a negative (positive) enhancement in FDs caused by the northern (southern) eruptions. This implies that the GCR density minimum is located behind the central flank of IP-shocks and propagating radially outward from the location of the solar eruption. We also confirmed that the average G {sub z} changes its sign above and below the heliospheric current sheet, in accord with the prediction of the drift model for the large-scale GCR transport in the heliosphere.« less

Demonstration of a viable quantitative theory for interplanetary type II radio bursts

NASA Astrophysics Data System (ADS)

Schmidt, J. M.; Cairns, Iver H.

2016-03-01

Between 29 November and 1 December 2013 the two widely separated spacecraft STEREO A and B observed a long lasting, intermittent, type II radio burst for the extended frequency range ≈ 4 MHz to 30 kHz, including an intensification when the shock wave of the associated coronal mass ejection (CME) reached STEREO A. We demonstrate for the first time our ability to quantitatively and accurately simulate the fundamental (F) and harmonic (H) emission of type II bursts from the higher corona (near 11 solar radii) to 1 AU. Our modeling requires the combination of data-driven three-dimensional magnetohydrodynamic simulations for the CME and plasma background, carried out with the BATS-R-US code, with an analytic quantitative kinetic model for both F and H radio emission, including the electron reflection at the shock, growth of Langmuir waves and radio waves, and the radiations propagation to an arbitrary observer. The intensities and frequencies of the observed radio emissions vary hugely by factors ≈ 106 and ≈ 103, respectively; the theoretical predictions are impressively accurate, being typically in error by less than a factor of 10 and 20 %, for both STEREO A and B. We also obtain accurate predictions for the timing and characteristics of the shock and local radio onsets at STEREO A, the lack of such onsets at STEREO B, and the z-component of the magnetic field at STEREO A ahead of the shock, and in the sheath. Very strong support is provided by these multiple agreements for the theory, the efficacy of the BATS-R-US code, and the vision of using type IIs and associated data-theory iterations to predict whether a CME will impact Earth's magnetosphere and drive space weather events.

A Study of the Interplanetary Signatures of Earth-Arriving CMEs

NASA Astrophysics Data System (ADS)

Akiyama, S.; Yashiro, S.; Gopalswamy, N.; Xie, H.; Makela, P. A.; Kay, C.

2017-12-01

We studied interplanetary (IP) signatures associated with coronal mass ejections (CMEs) that are likely to reach Earth. In order to find Earth- arriving CMEs, we started with disk-center CMEs originating within 30 degrees from the central meridian and the equator. Using the side-view images from the STEREO mission, we excluded CMEs that faded out before reaching the Earth orbit, or were captured by other CMEs, or erupted away from the ecliptic plane. We found 61 Earth- arriving CMEs during 2009/10/01 - 2012/07/31 (inclusive). Though all events were observed to reach Earth in the STEREO/HI2 field of view, only 34 out of 61 events (56%) were associated with magnetic cloud (MC) or ejecta (EJ) observed by ACE or Wind. We compared the CME characteristics associated with 9 MCs, 25 EJs, and 27 no- clear- signature (NCS) events to find out what might cause the difference in the IP signatures. To avoid projection effects, we used coronagraph images obtained by the STEREO mission. The average speed (width) of CMEs associated with MCs, EJs, and NCSs are 484 km/s (104°), 663 km/s (135°), and 595 km/s (144°), respectively. CMEs associated with MCs tend to be less energetic than other types in our dataset. We also checked the coronal holes (CHs) near the CME source to examine the effect of the CME deflection. In the case of MCs and EJs, only 22% (2/9) and 28% (7/25) events have CHs near the source, while 48% (13/27) NCS events have nearby CHs. We discuss what factors near the Sun cause the observed differences at Earth.

An extreme ultraviolet wave associated with a failed eruption observed by the Solar Dynamics Observatory

NASA Astrophysics Data System (ADS)

Zheng, R.; Jiang, Y.; Yang, J.; Bi, Y.; Hong, J.; Yang, B.; Yang, D.

2012-05-01

Aims: Taking advantage of the high temporal and spatial resolution of the Solar Dynamics Observatory (SDO) observations, we present an extreme ultraviolet (EUV) wave associated with a failed filament eruption that generated no coronal mass ejection (CME) on 2011 March 1. We aim at understanding the nature and origin of this EUV wave. Methods: Combining the high-quality observations in the photosphere, the chromosphere, and the corona, we studied the characteristics of the wave and its relations to the associated eruption. Results: The event occurred at an ephemeral region near a small active region. The continuous magnetic flux cancelation in the ephemeral region produced pre-eruption brightenings and two EUV jets, and excited the filament eruption, accompanying it with a microflare. After the eruption, the filament material appeared far from the eruption center, and the ambient loops seemed to be intact. It was evident that the filament eruption had failed and was not associated with a CME. The wave happened just after the north jet arrived, and apparently emanated ahead of the north jet, far from the eruption center. The wave propagated at nearly constant velocities in the range of 260-350 km s-1, with a slight negative acceleration in the last phase. Remarkably, the wave continued to propagate, and a loop in its passage was intact when wave and loop met. Conclusions: Our analysis confirms that the EUV wave is a true wave, which we interpret as a fast-mode wave. In addition, the close temporal and spatial relationship between the wave and the jet provides evidence that the wave was likely triggered by the jet when the CME failed to happen. Three movies are available in electronic form at http://www.aanda.org

Solar Terrestrial Relations Observatory (STEREO)

NASA Technical Reports Server (NTRS)

Davila, Joseph M.; SaintCyr, O. C.

2003-01-01

The solar magnetic field is constantly generated beneath the surface of the Sun by the solar dynamo. To balance this flux generation, there is constant dissipation of magnetic flux at and above the solar surface. The largest phenomenon associated with this dissipation is the Coronal Mass Ejection (CME). The Solar and Heliospheric Observatory (SOHO) has provided remarkable views of the corona and CMEs, and served to highlight how these large interplanetary disturbances can have terrestrial consequences. STEREO is the next logical step to study the physics of CME origin, propagation, and terrestrial effects. Two spacecraft with identical instrument complements will be launched on a single launch vehicle in November 2007. One spacecraft will drift ahead and the second behind the Earth at a separation rate of 22 degrees per year. Observation from these two vantage points will for the first time allow the observation of the three-dimensional structure of CMEs and the coronal structures where they originate. Each STEREO spacecraft carries a complement of 10 instruments, which include (for the first time) an extensive set of both remote sensing and in-situ instruments. The remote sensing suite is capable of imaging CMEs from the solar surface out to beyond Earth's orbit (1 AU), and in-situ instruments are able to measure distribution functions for electrons, protons, and ions over a broad energy range, from the normal thermal solar wind plasma to the most energetic solar particles. It is anticipated that these studies will ultimately lead to an increased understanding of the CME process and provide unique observations of the flow of energy from the corona to the near-Earth environment. An international research program, the International Heliophysical Year (IHY) will provide a framework for interpreting STEREO data in the context of global processes in the Sun-Earth system.

NEW OBSERVATION OF FAILED FILAMENT ERUPTIONS: THE INFLUENCE OF ASYMMETRIC CORONAL BACKGROUND FIELDS ON SOLAR ERUPTIONS

DOE Office of Scientific and Technical Information (OSTI.GOV)

Liu, Y.; Xu, Z.; Su, J.

2009-05-01

Failed filament eruptions not associated with a coronal mass ejection (CME) have been observed and reported as evidence for solar coronal field confinement on erupting flux ropes. In those events, each filament eventually returns to its origin on the solar surface. In this Letter, a new observation of two failed filament eruptions is reported which indicates that the mass of a confined filament can be ejected to places far from the original filament channel. The jetlike mass motions in the two failed filament eruptions are thought to be due to the asymmetry of the background coronal magnetic fields with respectmore » to the locations of the filament channels. The asymmetry of the coronal fields is confirmed by an extrapolation based on a potential field model. The obvious imbalance between the positive and negative magnetic flux (with a ratio of 1:3) in the bipolar active region is thought to be the direct cause of the formation of the asymmetric coronal fields. We think that the asymmetry of the background fields can not only influence the trajectories of ejecta, but also provide a relatively stronger confinement for flux rope eruptions than the symmetric background fields do.« less

Neutralized solar energetic particles in the inner heliosphere: a parameter study

NASA Astrophysics Data System (ADS)

Wang, Xiao-Dong; Klecker, Berndt; Futaana, Yoshifumi; Cipriani, Fabrice; Barabash, Stas; Wieser, Martin

2016-04-01

The large fluxes of solar energetic particles (SEPs) in Gradual Events, dominated by protons, are believed to be produced by the acceleration of shocks driven by coronal mass ejections (CMEs). As SEPs propagate in the lower corona, there is a chance for them to be neutralized via the charge exchange and/or recombination processes and become energetic neutral atoms (ENAs). These ENAs retain the velocity of their parent SEPs and propagate in straight lines without the influence of the interplanetary magnetic field, and therefore might potentially serve as a new window to observe the particle acceleration processes in the solar corona. STEREO/Low Energy Telescope reported the first probable observation of hydrogen ENAs between 1.6 MeV - 5 MeV from the Sun prior to an X-class flare/CME [Mewaldt et al., 2009]. While such observations were somehow controversial, Wang et al. [2014] simulated the neutralization of solar energetic protons in the corona lower than 40 RS, and the result agreed with the STEREO observation. In this work, we further developed a production model of the ENA near the sun together with a transport model toward the inner planets, and explore the dependences of the ENA characteristics against the model parameters. These parameters include the angular width of the CME, its propagation direction with respect to the Sun-observer line, the propagation speed, the particle density in the corona, the abundances of O6+ and C4+, and the reaction rate of electron impact ionization in the loss of ENAs, and the heliospheric distance of the observer. The calculated ENA flux shows that at lower energy the expected ENA flux depends most sensitively on the CME apex angle and the CME propagation direction. At higher energy the dependence on the coronal density is more prominent. References Mewaldt, R. A., R. A. Leske, E. C. Stone, A. F. Barghouty, A. W. Labrador, C. M. S. Cohen, A. C. Cummings, A. J. Davis, T. T. von Rosenvinge, and M. E. Wiedenbeck (2009), STEREO Observations of Energetic Neutral Hydrogen Atoms During the 2006 December 5 Solar Flare, Astrophys. J. Lett., 693(1), L11. Wang, L., G. Li, A. Y. Shih, R. P. Lin, and R. F. Wimmer-Schweingruber (2014), Simulation of Energetic Neutral Atoms from Solar Energetic Particles, Astrophys. J. Lett., 793(2), L37.

ElEvoHI: A Novel CME Prediction Tool for Heliospheric Imaging Combining an Elliptical Front with Drag-based Model Fitting

NASA Astrophysics Data System (ADS)

Rollett, T.; Möstl, C.; Isavnin, A.; Davies, J. A.; Kubicka, M.; Amerstorfer, U. V.; Harrison, R. A.

2016-06-01

In this study, we present a new method for forecasting arrival times and speeds of coronal mass ejections (CMEs) at any location in the inner heliosphere. This new approach enables the adoption of a highly flexible geometrical shape for the CME front with an adjustable CME angular width and an adjustable radius of curvature of its leading edge, I.e., the assumed geometry is elliptical. Using, as input, Solar TErrestrial RElations Observatory (STEREO) heliospheric imager (HI) observations, a new elliptic conversion (ElCon) method is introduced and combined with the use of drag-based model (DBM) fitting to quantify the deceleration or acceleration experienced by CMEs during propagation. The result is then used as input for the Ellipse Evolution Model (ElEvo). Together, ElCon, DBM fitting, and ElEvo form the novel ElEvoHI forecasting utility. To demonstrate the applicability of ElEvoHI, we forecast the arrival times and speeds of 21 CMEs remotely observed from STEREO/HI and compare them to in situ arrival times and speeds at 1 AU. Compared to the commonly used STEREO/HI fitting techniques (Fixed-ϕ, Harmonic Mean, and Self-similar Expansion fitting), ElEvoHI improves the arrival time forecast by about 2 to ±6.5 hr and the arrival speed forecast by ≈ 250 to ±53 km s-1, depending on the ellipse aspect ratio assumed. In particular, the remarkable improvement of the arrival speed prediction is potentially beneficial for predicting geomagnetic storm strength at Earth.

Space weather: Why are magnetospheric physicists interested in solar explosive phenomena

NASA Astrophysics Data System (ADS)

Koskinen, H. E. J.; Pulkkinen, T. I.

That solar activity drives magnetospheric dynamics has for a long time been the basis of solar-terrestrial physics. Numerous statistical studies correlating sunspots, 10.7 cm radiation, solar flares, etc., with various magnetospheric and geomagnetic parameters have been performed. However, in studies of magnetospheric dynamics the role of the Sun has often remained in the background and only the actual solar wind impinging the magnetosphere has gained most of the attention. During the last few years a new applied field of solar-terrestrial physics, space weather, has emerged. The term refers to variable particle and field conditions in our space environment, which may be hazardous to space-borne or ground-based technological systems and can endanger human life and health. When the modern society is becoming increasingly dependent on space technology, the need for better modelling and also forecasting of space weather becomes urgent. While for post analysis of magnetospheric phenomena it is quite sufficient to include observations from the magnetospheric boundaries out to L1 where SOHO is located, these observations do not provide enough lead-time to run space weather forecasting models and to distribute the forecasts to potential customers. For such purposes we need improved physical understanding and models to predict which active processes on the Sun will impact the magnetosphere and what their expected consequences are. An important change of view on the role of the Sun as the origin of magnetospheric disturbances has taken place during last 10--20 years. For a long time, the solar flares were thought to be the most geoeffective solar phenomena. Now the attention has shifted much more towards coronal mass ejections and the SOHO coronal observations seem to have turned the epoch irreversibly. However, we are not yet ready to make reliable perdictions of the terrestrial environment based on CME observations. From the space weather viewpoint, the key questions are when a CME will be ejected, will it hit the Earth, what will its density and speed be, and how the magnetic field will be wrapped around the plasma cloud. This is clearly an enormous modelling task, but very forthwhile to carry further. Also forecasting of the solar energetic particle events would be very usefule as they form the most hazardous single effect on spaceflight, be that on the Space Station, on the Moon, or even further. We illustrate the chain of effects from the solar atmosphere to near-Earth space using some of the CME-associated magnetic storm events from the SOHO era.

Determining the Evolution and Propagation of CME Flux Ropes from the Sun to Earth

NASA Astrophysics Data System (ADS)

Palmerio, E.; Kilpua, E.; Mierla, M.; Rodriguez, L.; Isavnin, A.; Zhukov, A.

2017-12-01

Coronal mass ejections (CMEs) are the main drivers of space weather phenomena at the Earth. They form in the solar atmosphere as helical magnetic field structures known as flux ropes. The key parameter that defines the ability of a CME to drive geomagnetic storms is the North-South magnetic field component. One of the most significant problems in current long-term space weather forecasts is that there is no practical method to measure the magnetic structure of CMEs routinely in the corona. The magnetic structure of erupting flux ropes can however be inferred based on the properties of the CME's source region characteristics, e.g.filament details, coronal EUV arcades, X-ray/EUV sigmoids, taking into account nearby coronal and photospheric features. These proxies are useful for reconstructing the "instrinsic flux rope type" at the time of the eruption. However, the knowledge of the flux rope's magnetic structure at the Sun does not always imply a successful prediction of the magnetic structure at the Earth. This is because CMEs can change their orientation due to deflections, rotations, and deformations. We present here examples of CMEs for which we have determined their magnetic structure when launched from the Sun by using a synthesis of indirect proxies based on multiwavelength remote-sensing observations. When compared to their in situ counterparts, these CMEs present a different magnetic configuration, implying a high amount of rotation of their central axis during their propagation. We study the early evolution of these CMEs both on the solar disk and in coronagraph images though different techniques, e.g. forward modelling and tie-pointing technique. When possible, we study the CME structure in situ at other planets. We aim at determining where the rotation occurs and the rate of rotation during the CME evolution from the Sun to Earth, and possibly estimating the causes of such a high amount of rotation.

An Observational Approach toward Understanding and Prediction of CME Magnetic Ejecta

NASA Astrophysics Data System (ADS)

Pizzo, V. J.; de Koning, C. A.; Riley, P.

2017-12-01

Quantitative knowledge of the magnetic field inside a coronal mass ejection (CME) is an important contributor to an actionable space weather forecast of geomagnetic storms. However, at present it is not possible to predict the magnetic cloud component of a CME with any accuracy. This has led to the development of increasingly sophisticated physics-based models, each promising a path toward more accurate space weather forecasts. Unfortunately, none of these models can provide meaningful output if they lack for reliable quantitative input. Until we can measure magnetic fields at solar distances where CMEs are launched and over their early-stage evolution, this will remain a fundamental obstacle to successful modeling. Instead of continuing to focus primarily on the modeling approach, we suggest an active investigation of direct, up-stream measurement of the CME internal magnetic field. For current forecasting purposes, or even as a science concept mission, the measurements do not need to be of high accuracy or high cadence. Since previous magnetic cloud analyses have demonstrated that a single spacecraft provides insufficient data to robustly reconstruct the CME internal magnetic field, we suggest deploying a swarm of cube-sats in "quasi-satellite" orbits that are known to be horizontally and vertically stable, even at large (several tenths of an AU) distances from Earth. In this presentation, we describe how simulations of CMEs incorporating magnetic clouds can be used to develop and support this mission concept. By taking simulated cuts through model CMEs with a range of magnetic morphologies and field strengths, we aim to determine the minimum number of spacecraft needed for such a mission and their optimum orbital characteristics. Although a host of challenges remain, especially related to communications and cube-sat telemetry in interplanetary space, we believe that these technological issues can be surmounted once it has been demonstrated that a major leap in understanding and forecasting magnetic ejecta is possible via a cube-sat swarm.

Lifetime Evolution of UV Jets

NASA Technical Reports Server (NTRS)

Corti, G.; Poletto, G.; Suess, S. T.; Moore, R.; Sterling, A.

2006-01-01

We report on observations acquired in May 2003 during a SOHO-Ulysses quadrature campaign. From May 25 to May 28, the SoHO LASCO Coronal Mass Ejection (CME) catalog lists a number of events which might have been observed by SOHO/UVCS, whose slit was centered along the Ulysses direction. However, because of time gaps in the observing schedule, or because of the unfavorable position of some CMEs, the most interesting events recorded by UVCS were a few short-lived ejections that represent the extension at higher altitudes of recursive EIT jets. We focus on jets occurring on May 26/27, visible also in EIT and LASCO images, which seem to propagate along the radial to Ulysses. UVCS spectra at 1.7 Rsun showed an unusually high emission in cool lines, lasting for about 10 to 25 minutes, with no evidence of hot plasma. Analysis of the cool line emission allowed us to infer the evolution of physical parameters during the jets lifetime and derive a crude estimate of the energy needed to account for their properties. We also looked for any evidence of the event in in situ data. Whether UVCS is observing jets or narrow CMEs is discussed in the contest of previous works on these classes of events and, in the last Section, we propose a scenario that accounts for our observations.

An Analytical Diffusion–Expansion Model for Forbush Decreases Caused by Flux Ropes

NASA Astrophysics Data System (ADS)

Dumbović, Mateja; Heber, Bernd; Vršnak, Bojan; Temmer, Manuela; Kirin, Anamarija

2018-06-01

We present an analytical diffusion–expansion Forbush decrease (FD) model ForbMod, which is based on the widely used approach of an initially empty, closed magnetic structure (i.e., flux rope) that fills up slowly with particles by perpendicular diffusion. The model is restricted to explaining only the depression caused by the magnetic structure of the interplanetary coronal mass ejection (ICME). We use remote CME observations and a 3D reconstruction method (the graduated cylindrical shell method) to constrain initial boundary conditions of the FD model and take into account CME evolutionary properties by incorporating flux rope expansion. Several flux rope expansion modes are considered, which can lead to different FD characteristics. In general, the model is qualitatively in agreement with observations, whereas quantitative agreement depends on the diffusion coefficient and the expansion properties (interplay of the diffusion and expansion). A case study was performed to explain the FD observed on 2014 May 30. The observed FD was fitted quite well by ForbMod for all expansion modes using only the diffusion coefficient as a free parameter, where the diffusion parameter was found to correspond to an expected range of values. Our study shows that, in general, the model is able to explain the global properties of an FD caused by a flux rope and can thus be used to help understand the underlying physics in case studies.

CONSTRAINING THE SOLAR CORONAL MAGNETIC FIELD STRENGTH USING SPLIT-BAND TYPE II RADIO BURST OBSERVATIONS

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kishore, P.; Ramesh, R.; Hariharan, K.

2016-11-20

We report on low-frequency radio (85–35 MHz) spectral observations of four different type II radio bursts, which exhibited fundamental-harmonic emission and split-band structure. Each of the bursts was found to be closely associated with a whitelight coronal mass ejection (CME) close to the Sun. We estimated the coronal magnetic field strength from the split-band characteristics of the bursts, by assuming a model for the coronal electron density distribution. The choice of the model was constrained, based on the following criteria: (1) when the radio burst is observed simultaneously in the upper and lower bands of the fundamental component, the locationmore » of the plasma level corresponding to the frequency of the burst in the lower band should be consistent with the deprojected location of the leading edge (LE) of the associated CME; (2) the drift speed of the type II bursts derived from such a model should agree closely with the deprojected speed of the LE of the corresponding CMEs. With the above conditions, we find that: (1) the estimated field strengths are unique to each type II burst, and (2) the radial variation of the field strength in the different events indicate a pattern. It is steepest for the case where the heliocentric distance range over which the associated burst is observed is closest to the Sun, and vice versa.« less

Oscillations in the wake of a flare blast wave

NASA Astrophysics Data System (ADS)

Tothova, D.; Innes, D. E.; Stenborg, G.

2011-04-01

Context. Oscillations of coronal loops in the Sun have been reported in both imaging and spectral observations at the onset of flares. Images reveal transverse oscillations, whereas spectra detect line-of-sight velocity or Doppler-shift oscillations. The Doppler-shift oscillations are commonly interpreted as longitudinal modes. Aims: Our aim is to investigate the relationship between loop dynamics and flows seen in TRACE 195 Å images and Doppler shifts observed by SUMER in Si iii 1113.2 Å and FeXIX 1118.1 Å at the time of a C.8-class limb flare and an associated CME. Methods: We carefully co-aligned the sequence of TRACE 195 Å images to structures seen in the SUMER Si iii, CaX, and FeXIX emission lines. Additionally, Hα observations of a lifting prominence associated with the flare and the coronal mass ejection (CME) are available in three bands around 6563.3 Å. They give constraints on the timing and geometry. Results: Large-scale Doppler-shift oscillations in FeXIX and transverse oscillations in intensity images were observed over a large region of the corona after the passage of a wide bright extreme-ultraviolet (EUV) disturbance, which suggests ionization, heating, and acceleration of hot plasma in the wake of a blast wave. The online movie associated to Fig. 2 is available at http://www.aanda.org and at http://www.mps.mpg.de/data/outgoing/tothova/movie.gif

Probing SEP Acceleration Processes With Near-relativistic Electrons

NASA Astrophysics Data System (ADS)

Haggerty, Dennis K.; Roelof, Edmond C.

2009-11-01

Processes in the solar corona are prodigious accelerators of near-relativistic electrons. Only a small fraction of these electrons escape the low corona, yet they are by far the most abundant species observed in Solar Energetic Particle events. These beam-like energetic electron events are sometimes time-associated with coronal mass ejections from the western solar hemisphere. However, a significant number of events are observed without any apparent association with a transient event. The relationship between solar energetic particle events, coronal mass ejections, and near-relativistic electron events are better ordered when we classify the intensity time profiles during the duration of the beam-like anisotropies into three broad categories: 1) Spikes (rapid and equal rise and decay) 2) Pulses (rapid rise, slower decay) and 3) Ramps (rapid rise followed by a plateau). We report on the results of a study that is based on our catalog (covering nearly the complete Solar Cycle 23) of 216 near-relativistic electron events and their association with: solar electromagnetic emissions, shocks driven by coronal mass ejections, models of the coronal magnetic fields and energetic protons. We conclude that electron events with time-intensity profiles of Spikes and Pulses are associated with explosive events in the low corona while events with time-intensity profiles of Ramps are associated with the injection/acceleration process of the CME driven shock.

Thermosphere Global Time Response to Geomagnetic Storms Caused by Coronal Mass Ejections

NASA Astrophysics Data System (ADS)

Oliveira, D. M.; Zesta, E.; Schuck, P. W.; Sutton, E. K.

2017-10-01

We investigate, for the first time with a spatial superposed epoch analysis study, the thermosphere global time response to 159 geomagnetic storms caused by coronal mass ejections (CMEs) observed in the solar wind at Earth's orbit during the period of September 2001 to September 2011. The thermosphere neutral mass density is obtained from the CHAMP (CHAllenge Mini-Satellite Payload) and GRACE (Gravity Recovery Climate Experiment) spacecraft. All density measurements are intercalibrated against densities computed by the Jacchia-Bowman 2008 empirical model under the regime of very low geomagnetic activity. We explore both the effects of the pre-CME shock impact on the thermosphere and of the storm main phase onset by taking their times of occurrence as zero epoch times (CME impact and interplanetary magnetic field Bz southward turning) for each storm. We find that the shock impact produces quick and transient responses at the two high-latitude regions with minimal propagation toward lower latitudes. In both cases, thermosphere is heated in very high latitude regions within several minutes. The Bz southward turning of the storm onset has a fast heating manifestation at the two high-latitude regions, and it takes approximately 3 h for that heating to propagate down to equatorial latitudes and to globalize in the thermosphere. This heating propagation is presumably accomplished, at least in part, with traveling atmospheric disturbances and complex meridional wind structures. Current models use longer lag times in computing thermosphere density dynamics during storms. Our results suggest that the thermosphere response time scales are shorter and should be accordingly adjusted in thermospheric empirical models.

THE BLOB CONNECTION: SEARCHING FOR LOW CORONAL SIGNATURES OF SOLAR POST-CME BLOBS

DOE Office of Scientific and Technical Information (OSTI.GOV)

Schanche, Nicole E; Reeves, Katharine K; Webb, David F., E-mail: nschanche@cfa.harvard.edu

2016-11-01

Bright linear structures, thought to be indicators of a current sheet (CS), are often seen in Large Angle and Spectrometric Coronagraph (LASCO) on the Solar and Heliospheric Observatory (SOHO) white-light data in the wake of coronal mass ejections (CMEs). In a subset of these post-CME structures, relatively bright blobs are seen moving outward along the rays. These blobs have been interpreted as consequences of the plasmoid instability in the CS, and can help us to understand the dynamics of the reconnection. We examine several instances, taken largely from the SOHO /LASCO CME-rays Catalog, where these blobs are clearly visible inmore » white-light data. Using radially filtered, difference, wavelet enhanced, and multiscale Gaussian normalized images to visually inspect Solar Dynamics Observatory /Atmospheric Imaging Assembly (AIA) data in multiple wavelengths, we look for signatures of material that correspond both temporally and spatially to the later appearance of the blobs in LASCO/C2. Constraints from measurements of the blobs allow us to predict the expected count rates in DN pixel{sup −1} s{sup −1} for each AIA channel. The resulting values would make the blobs bright enough to be detectable at 1.2 R {sub ⊙}. However, we do not see conclusive evidence for corresponding blobs in the AIA data in any of the events. We do the same calculation for the “cartwheel CME,” an event in which blobs were seen in X-rays, and find that our estimated count rates are close to those observed. We suggest several possibilities for the absence of the EUV blobs including the formation of the blob higher than the AIA field of view, blob coalescence, and overestimation of blob densities.« less

Radial dependence of solar energetic particles derived from the 15 March 2013 solar energetic particle event and global MHD simulation

DOE Office of Scientific and Technical Information (OSTI.GOV)

Wu, Chin-Chun, E-mail: chin-chun.wu@nrl.navy.mil; Plunkett, Simon, E-mail: simon.plunkett@nrl.navy.mil; Liou, Kan, E-mail: kan.liou@jhuapl.edu

2016-03-25

We study an unusual solar energetic particle (SEP) event that was associated with the coronal mass ejection (CME) on March 15, 2013. Enhancements of the SEP fluxes were first detected by the ACE spacecraft at 14:00 UT, ∼7 hours after the onset of the CME (07:00 UT), and the SEP’s peak intensities were recorded ∼36 hours after the onset of the CME. Our recent study showed that the CME-driven shock Mach number, based on a global three-dimensional (3-D) magnetohydrodynamic (MHD) simulation, is well correlated with the time-intensity of 10-30 MeV and 30-80 MeV protons. Here we focus on the radial dependence (r{supmore » −α}) of {sup 4}He (3.43-41.2 MeV/n) and O (7.30-89.8 MeV/n) energetic particles from ACE/SIS. It is found that the scaling factor (α) ranges between 2 and 4 for most of the energy channels. We also found that the correlation coefficients tend to increase with SEP energies.« less

Are We Observing Coronal Mass Ejections in OH/IR AGB Stars?

NASA Astrophysics Data System (ADS)

Heiles, Carl

2017-05-01

Solar Coronal Mass Ejections (CMEs) are magnetic electron clouds that are violently ejected by the same magnetic reconnection events that produce Solar flares. CMEs are the major driving source of the hazardous space weather environments near the Earth. In exoplanet systems, the equivalent of Solar wind and CMEs can affect a planet's atmosphere, and in extreme cases can erode it, as probably happened with Mars, or disrupt the cosmic-ray shielding aspect of the planet's magnetic field.We (Jensen et al. 2013SoPh..285...83J, 2016SoPh..291..465J) have developed a new way to observe the electron column density and magnetic field of CMEs, namely to measure the frequency change and Faraday rotation of a spacecraft downlink carrier produced by propagation effects in the plasma. Surprisingly, this can work on other stars if they have the equivalent of the spacecraft carrier, as do OH/IR stars.OH/IR stars are Asymptotic Giant Branch (AGB) stars, which are red giant stars burning He in their final stages of stellar evolution. They have highly convective surfaces and large mass-ejection rates in the form of expanding dense shells of molecular gas and obscuring dust, which were ejected from the star by chaotic turbulent motions and then accelerated by radiation pressure. OH masers reside in these shells, pumped by the IR emission from the dust. The OH masers on the far side of the star (i.e., the positive-velocity masers) are the surrogate for the Solar-case spacecraft signal.The big question: Can we see CMEs in OH/IR stars? We have observed six OH/IR stars with the Arecibo Observatory for a total of about 150 hours over the past 1.5 years. We see changes in OH maser frequency and in the position angle of linear polarization. Both can be produced by electron clouds moving across the line of sight. We will present statistical summaries of the variability and interpret them in terms of CME models.

SPE in Solar Cycle 24 : Flare and CME characteristic

NASA Astrophysics Data System (ADS)

Neflia, Neflia

SPE is one of the most severe hazards in the space environment. Such events, tend to occur during periods of intense solar activity, and can lead to high radiation doses in short time intervals. The proton enhancements produced by these solar events may last several days and are very hard to predict in advance and they also can cause harm to both satellite and human in space. The most significant sources of proton in the interplanetary medium are both solar flares and interplanetary shocks driven by coronal mass ejections (CMEs). In this study, I try to find the characteristic of Flare and CME that can cause the proton events in interplanetary medium. For my preliminary study, I will search flare characteristic such as class and position as an SPE causes. I also did the research with CME characteristic such as Angular Width (AW) and linier velocity. During solar cycle 24, the solar activity remain very low with several large flare and Halo CME. This low activity also occur on solar proton events in interplanetary medium. From January 2009 to May 2013, there are 25 SPEs with flux range from 12 - 6530 sfu (10 MeV). The solar flare during these events varies from C to X- class flare. From 27 X-class flare that occur during 2009 - May 2013, only 7 flares cause the SPE. Most of active region location are at solar Western Hemisphere (16/25). only 24 from 139 halo CME (AW=360) cause SPE. Although the probability of SPE from all flare and CME during this range of time is small but they have 3 common characteristics, ie, most of the SPE have active region position at Solar Western Hemisphere, the CME have AW=360 and they have a high linier velocity.

Factors Affecting the Occurrence of Large Solar Energetic Particle Events

NASA Astrophysics Data System (ADS)

Gopalswamy, N.; Yashiro, S.; Akiyama, S.; Xie, H.; Makela, P. A.; Thakur, N.

2014-12-01

In order to understand the paucity of high-energy solar energetic particle (SEP) events in solar cycle 24, we examined all major eruptions (soft X-ray flare size ≥M5.0) on the front side of the Sun during the period from December 1, 2008 to January 31, 2014. There were 59 such eruptions that were associated with CMEs. When a flux rope was fitted to the white-light CMEs observed by SOHO and STEREO it was found that the CME sources were on the disk only for 55 eruptions. There were 16 large SEP events (proton intensity ≥10 pfu in the >10 MeV channel) detected by GOES and 4 by STEREO-B in association with these eruptions. When the CMEs were grouped according to their speeds (<1500 km/s and ≥ 1500 km/s) it was found that only three of the <1500 km/s CMEs (or 11%) were associated with large SEP events compared to 17 or (61%) of the ≥ 1500 km/s CMEs. This result confirms the importance of CME speed for SEP association. In fact there were ten other large SEP events with flare size

A Study of the Initiation Process of Coronal Mass Ejections and the Tool for Their Auto-Detection

NASA Astrophysics Data System (ADS)

Olmedo, Oscar

Coronal mass ejections (CMEs) are the most energetic and important solar activity. They are often associated with other solar phenomena such as flares and filament/prominence eruptions. Despite the significant improvement of CME study in the past decade, our understanding of the initiation process of CMEs remains elusive. In order to solve this issue, an approach that combines theoretical modelling and empirical analysis is needed. This thesis is a combination of three studies, two of which investigate the initiation process of CMEs, and the other is the development of a tool to automatically detect CMEs. First, I investigate the stability of the well-known eruptive flux rope model in the context of the torus instability. In the flux rope model, the pre-eruptive CME structure is a helical flux rope with two footpoints anchored to the solar surface. The torus instability is dependent on the balance between two opposing magnetic forces, the outward Lorentz self-force (also called curvature hoop force) and the restoring Lorentz force of the ambient magnetic fields. Previously, the condition of stability derived for the torus instability assumed that the pre-eruptive structure was a semicircular loop above the photosphere without anchored footpoints. I extend these results to partial torus flux ropes of any circularity with anchored footpoints and discovered that there is a dependence of the critical index on the fractional number of the partial torus, defined by the ratio between the arc length of the partial torus above the photosphere and the circumference of a circular torus of equal radius. I coin this result the partial torus instability (PTI). The result is more general than has been previously derived and extends to loops of any arc above the photosphere. It will be demonstrated that these results can help us understand the confinement, growth, and eventual eruption of a flux rope CME. Second, I use observations of eruptive prominences associated with CMEs to examine the behaviour of their initiation and compare these observations to theoretical models. Since theoretical models specify the pre-existence of a flux rope, the observational challenge is the interpretation of the flux rope in solar images. A good proxy for flux ropes is prominences, because of its obvious elongated helical structure above the magnetic polarity line. I compare the prominence kinematics and the associated extrapolated magnetic fields. This observational study yields two key conclusions. The first is that there is a dependence of the ejecta's kinematics on how the ambient magnetic field decay's. The second is that the critical decay index, theorized to be where the flux rope transitions from a stable to unstable configuration, is dependent on the geometry of the loop. This second result is in qualitative agreement with the theorized PTI. Finally, I develop a tool to automatically detect CME events in coronagraph images. Because of the large amount of data collected over the years, searching for candidate events to study can be daunting. In order to facilitate the search of CME event candidates, an algorithm was developed to automatically detect and characterize CMEs seen in coronagraph images. With this tool, one need not scroll through the large number of images, and only focus on particular subsets. The auto-detection reduces human bias of CME characterization. Such automated detection algorithms can have other applications, such as space weather alerts in near-real time. In summary, this thesis has improved our understanding of the initiation process of CMEs by taking both theoretical and observational studies. Future work includes investigating a larger number of events to give a better statistical characterization of the results found in the observational study. Furthermore, modification to the theoretical model of the PTI, for example by ncluding a repulsive force due to induced photospheric currents, can improve the quantitative agreement with observations. The complete knowledge of the initiation of CMEs is important because it can help us to predict when such an event may occur. Such a prediction can aid in mitigating severe space weather effects at the Earth.

Spatial Offsets in Flare-CME Current Sheets

DOE Office of Scientific and Technical Information (OSTI.GOV)

Raymond, John C.; Giordano, Silvio; Ciaravella, Angela, E-mail: jraymond@cfa.harvard.edu

Magnetic reconnection plays an integral part in nearly all models of solar flares and coronal mass ejections (CMEs). The reconnection heats and accelerates the plasma, produces energetic electrons and ions, and changes the magnetic topology to form magnetic flux ropes and to allow CMEs to escape. Structures that appear between flare loops and CME cores in optical, UV, EUV, and X-ray observations have been identified as current sheets and have been interpreted in terms of the nature of the reconnection process and the energetics of the events. Many of these studies have used UV spectral observations of high temperature emissionmore » features in the [Fe xviii] and Si xii lines. In this paper, we discuss several surprising cases in which the [Fe xviii] and Si xii emission peaks are spatially offset from each other. We discuss interpretations based on asymmetric reconnection, on a thin reconnection region within a broader streamer-like structure, and on projection effects. Some events seem to be easily interpreted as the projection of a sheet that is extended along the line of sight that is viewed an angle, but a physical interpretation in terms of asymmetric reconnection is also plausible. Other events favor an interpretation as a thin current sheet embedded in a streamer-like structure.« less

GROWING TRANSVERSE OSCILLATIONS OF A MULTISTRANDED LOOP OBSERVED BY SDO/AIA

DOE Office of Scientific and Technical Information (OSTI.GOV)

Wang, Tongjiang; Ofman, Leon; Su, Yang

The first evidence of transverse oscillations of a multistranded loop with growing amplitudes and internal coupling observed by the Atmospheric Imaging Assembly on board the Solar Dynamics Observatory is presented. The loop oscillation event occurred on 2011 March 8, triggered by a coronal mass ejection (CME). The multiwavelength analysis reveals the presence of multithermal strands in the oscillating loop, whose dynamic behaviors are temperature-dependent, showing differences in their oscillation amplitudes, phases, and emission evolution. The physical parameters of growing oscillations of two strands in 171 A are measured and the three-dimensional loop geometry is determined using STEREO-A/EUVI data. These strandsmore » have very similar frequencies, and between two 193 A strands a quarter-period phase delay sets up. These features suggest the coupling between kink oscillations of neighboring strands and the interpretation by the collective kink mode as predicted by some models. However, the temperature dependence of the multistranded loop oscillations was not studied previously and needs further investigation. The transverse loop oscillations are associated with intensity and loop width variations. We suggest that the amplitude-growing kink oscillations may be a result of continuous non-periodic driving by magnetic deformation of the CME, which deposits energy into the loop system at a rate faster than its loss.« less

Models for determining the geometrical properties of halo coronal mass ejections

NASA Astrophysics Data System (ADS)

Zhao, X.; Liu, Y.

2005-12-01

To this day, the prediction of space weather effects near the Earth suffer from a fundamental problem: the necessary condition for determining whether or not and when a part of the huge interplanetary counterpart (ICME) of frontside halo coronal mass ejections (CMEs) is able to hit the Earth and generate goemagnetic storms, i.e., the real angular width, the propagation direction and speed of the CMEs, cannot be measured directly because of the unfavorable geometry. To inverse these geometrical and kinematical properties we have recently developed a few geometrical models, such as the cone model, the ice cream cone model, and the spherical cone model. The inversing solution of the cone model for the 12 may 1997 halo CME has been used as an input to the ENLIL model (a 3D MHD solar wind code) and successfully predicted the ICME near the Earth (Zhao, Plukett & Liu, 2002; Odstrcil, Riley & Zhao, 2004). After briefly describing the geometrical models this presentation will discuss: 1. What kind of halo CMEs can be inversed? 2. How to select the geometrical models given a specific halo CME? 3. Whether or not the inversing solution is unique?

Radial distributions of magnetic field strength in the solar corona as derived from data on fast halo CMEs

NASA Astrophysics Data System (ADS)

Fainshtein, Victor; Egorov, Yaroslav

2018-03-01

In recent years, information about the distance between the body of rapid coronal mass ejection (CME) and the associated shock wave has been used to measure the magnetic field in the solar corona. In all cases, this technique allows us to find coronal magnetic field radial profiles B(R) applied to the directions almost perpendicular to the line of sight. We have determined radial distributions of magnetic field strength along the directions close to the Sun-Earth axis. For this purpose, using the "ice-cream cone" model and SOHO/LASCO data, we found 3D characteristics for fast halo coronal mass ejections (HCMEs) and for HCME-related shocks. With these data, we managed to obtain the B(R) distributions as far as ≈43 solar radii from the Sun's center, which is approximately twice as far as those in other studies based on LASCO data. We have concluded that to improve the accuracy of this method for finding the coronal magnetic field we should develop a technique for detecting CME sites moving in the slow and fast solar wind. We propose a technique for selecting CMEs whose central (paraxial) part actually moves in the slow wind.

Sun Emits a Solstice CME

NASA Image and Video Library

2017-12-08

Caption: This image from June 20, 2013, at 11:15 p.m. EDT shows the bright light of a solar flare on the left side of the sun and an eruption of solar material shooting through the sun’s atmosphere, called a prominence eruption. Shortly thereafter, this same region of the sun sent a coronal mass ejection out into space. --- On June 20, 2013, at 11:24 p.m., the sun erupted with an Earth-directed coronal mass ejection or CME, a solar phenomenon that can send billions of tons of particles into space that can reach Earth one to three days later. These particles cannot travel through the atmosphere to harm humans on Earth, but they can affect electronic systems in satellites and on the ground. Experimental NASA research models, based on observations from NASA’s Solar Terrestrial Relations Observatory and ESA/NASA’s Solar and Heliospheric Observatory show that the CME left the sun at speeds of around 1350 miles per second, which is a fast speed for CMEs. Earth-directed CMEs can cause a space weather phenomenon called a geomagnetic storm, which occurs when they funnel energy into Earth's magnetic envelope, the magnetosphere, for an extended period of time. The CME’s magnetic fields peel back the outermost layers of Earth's fields changing their very shape. Magnetic storms can degrade communication signals and cause unexpected electrical surges in power grids. They also can cause aurora. Storms are rare during solar minimum, but as the sun’s activity ramps up every 11 years toward solar maximum – currently expected in late 2013 -- large storms occur several times per year. In the past, geomagnetic storms caused by CMEs of this strength and direction have usually been mild. Read more: 1.usa.gov/14OxuEe Credit: NASA/Goddard/SDO NASA image use policy. NASA Goddard Space Flight Center enables NASA’s mission through four scientific endeavors: Earth Science, Heliophysics, Solar System Exploration, and Astrophysics. Goddard plays a leading role in NASA’s accomplishments by contributing compelling scientific knowledge to advance the Agency’s mission. Follow us on Twitter Like us on Facebook Find us on Instagram

Sun Emits a Solstice CME

NASA Image and Video Library

2017-12-08

Caption: This image from June 20, 2013, at 11:15 p.m. EDT shows the bright light of a solar flare on the left side of the sun and an eruption of solar material shooting through the sun’s atmosphere, called a prominence eruption. Shortly thereafter, this same region of the sun sent a coronal mass ejection out into space. --- On June 20, 2013, at 11:24 p.m., the sun erupted with an Earth-directed coronal mass ejection or CME, a solar phenomenon that can send billions of tons of particles into space that can reach Earth one to three days later. These particles cannot travel through the atmosphere to harm humans on Earth, but they can affect electronic systems in satellites and on the ground. Experimental NASA research models, based on observations from NASA’s Solar Terrestrial Relations Observatory and ESA/NASA’s Solar and Heliospheric Observatory show that the CME left the sun at speeds of around 1350 miles per second, which is a fast speed for CMEs. Earth-directed CMEs can cause a space weather phenomenon called a geomagnetic storm, which occurs when they funnel energy into Earth's magnetic envelope, the magnetosphere, for an extended period of time. The CME’s magnetic fields peel back the outermost layers of Earth's fields changing their very shape. Magnetic storms can degrade communication signals and cause unexpected electrical surges in power grids. They also can cause aurora. Storms are rare during solar minimum, but as the sun’s activity ramps up every 11 years toward solar maximum – currently expected in late 2013 -- large storms occur several times per year. In the past, geomagnetic storms caused by CMEs of this strength and direction have usually been mild. Credit: NASA/Goddard/SDO NASA image use policy. NASA Goddard Space Flight Center enables NASA’s mission through four scientific endeavors: Earth Science, Heliophysics, Solar System Exploration, and Astrophysics. Goddard plays a leading role in NASA’s accomplishments by contributing compelling scientific knowledge to advance the Agency’s mission. Follow us on Twitter Like us on Facebook Find us on Instagram

The acceleration of particles at propagating interplanetary shocks

NASA Astrophysics Data System (ADS)

Prinsloo, P. L.; Strauss, R. D. T.

2017-12-01

Enhancements of charged energetic particles are often observed at Earth following the eruption of coronal mass ejections (CMEs) on the Sun. These enhancements are thought to arise from the acceleration of those particles at interplanetary shocks forming ahead of CMEs, propagating into the heliosphere. In this study, we model the acceleration of these energetic particles by solving a set of stochastic differential equations formulated to describe their transport and including the effects of diffusive shock acceleration. The study focuses on how acceleration at halo-CME-driven shocks alter the energy spectra of non-thermal particles, while illustrating how this acceleration process depends on various shock and transport parameters. We finally attempt to establish the relative contributions of different seed populations of energetic particles in the inner heliosphere to observed intensities during selected acceleration events.

Halo Coronal Mass Ejections: Comparing Observations and Models

NASA Technical Reports Server (NTRS)

Gilbert, Holly; Orlove, Matthew; SaintCyr, O.; Mays, L.; Gopalswamy, N.

2011-01-01

Since 1996, the SOHO LASCO coronagraphs have detected "halo" CMEs that appear to be directed toward Earth, but information about the size and speed of these events seen face-on has been limited. From a single vantage point along the Sun-Earth line, the primary limitation has been ambiguity in fitting the cone model (or other forward-modeling techniques, e.g., Thernisian et al., 2006). But in the past few years, the STEREO mission has provided a view of Earth-directed events from the side. These events offer the opportunity to compare measurements (width and speed) of halo CMEs observed by STEREO with models that derive halo CME properties. We report here results of such a comparison on a large sample of LASCO CMEs in the STEREO era.

ESTIMATING THE HEIGHT OF CMEs ASSOCIATED WITH A MAJOR SEP EVENT AT THE ONSET OF THE METRIC TYPE II RADIO BURST DURING SOLAR CYCLES 23 AND 24

DOE Office of Scientific and Technical Information (OSTI.GOV)

Mäkelä, P.; Akiyama, S.; Xie, H.

2015-06-10

We studied the coronal mass ejection (CME) height at the onset of 59 metric type II radio bursts associated with major solar energetic particle (SEP) events, excluding ground level enhancements (GLEs), during solar cycles 23 and 24. We calculated CME heights using a simple flare-onset method used by Gopalswamy et al. to estimate CME heights at the metric type II onset for cycle 23 GLEs. We found the mean CME height for non-GLE events (1.72 R{sub ☉}) to be ∼12% greater than that (1.53 R{sub ☉}) for cycle 23 GLEs. The difference could be caused by more impulsive acceleration ofmore » the GLE-associated CMEs. For cycle 24 non-GLE events, we compared the CME heights obtained using the flare-onset method and the three-dimensional spherical-shock fitting method and found the correlation to be good (CC = 0.68). We found the mean CME height for cycle 23 non-GLE events (1.79 R{sub ☉}) to be greater than that for cycle 24 non-GLE events (1.58 R{sub ☉}), but statistical tests do not definitely reject the possibility of coincidence. We suggest that the lower formation height of the shocks during cycle 24 indicates a change in the Alfvén speed profile because solar magnetic fields are weaker and plasma density levels are closer to the surface than usual during cycle 24. We also found that complex type III bursts showing diminution of type III emission in the 7–14 MHz frequency range are more likely associated with events with a CME height at the type II onset above 2 R{sub ☉}, supporting suggestions that the CME/shock structure causes the feature.« less

Geomagnetic response of interplanetary coronal mass ejections in the Earth's magnetosphere

NASA Astrophysics Data System (ADS)

Badruddin; Mustajab, F.; Derouich, M.

2018-05-01

A coronal mass ejections (CME) is the huge mass of plasma with embedded magnetic field ejected abruptly from the Sun. These CMEs propagate into interplanetary space with different speed. Some of them hit the Earth's magnetosphere and create many types of disturbances; one of them is the disturbance in the geomagnetic field. Individual geomagnetic disturbances differ not only in their magnitudes, but the nature of disturbance is also different. It is, therefore, desirable to understand these differences not only to understand the physics of geomagnetic disturbances but also to understand the properties of solar/interplanetary structures producing these disturbances of different magnitude and nature. In this work, we use the spacecraft measurements of CMEs with distinct magnetic properties propagating in the interplanetary space and generating disturbances of different levels and nature. We utilize their distinct plasma and field properties to search for the interplanetary parameter(s) playing important role in influencing the geomagnetic response of different coronal mass ejections.

Sun-to-Earth Analysis of a Major Solar Eruption

NASA Astrophysics Data System (ADS)

Patsourakos, Spiros

During the interval of 7-10 March 2012, Earth's space environment experienced a barrage of space weather phenomena. Early during 7 March 2012, the biggest proton event of 2012 took place, while on 8 March 2012, an interplanetary shock and coronal mass ejection (CME) arrived at 1 AU. This sequence trigerred the biggest geomagnetic storm of cycle 24 so far. The solar source of these activities was a pair of homologous, eruptive X-class flares associated with two ultra-fast CMEs. The two eruptions originated from NOAA active region 11429 during the early hours of 7 March 2012 and within an hour from each other. Using satellite data from a flotilla of solar, heliospheric and magnetospheric missions and monitors, we perform a synergistic Sun-to-Earth study of various observational aspects of the event sequences. We will present an attempt to formulate a cohesive scenario which couples the eruption initiation, interplanetary propagation, and geospace consequences. Our main focus is on building a framework that starting from solar and near-Sun estimates of the magnetic and dynamic content and properties of the Earth-directed CME assess in advance the subsequent geomagnetic response expected, once the associated interplanetary CME reaches 1 AU. This research has been co-financed by the European Union (European Social Fund - ESF) and Greek national funds through the Operational Program "Education and Lifelong Learning" of the National Strategic Reference Framework (NSRF) - Research Funding Program: Thales. Investing in knowledge society through the European Social Fund.

High resolution solar observations in the context of space weather prediction

NASA Astrophysics Data System (ADS)

Yang, Guo

Space weather has a great impact on the Earth and human life. It is important to study and monitor active regions on the solar surface and ultimately to predict space weather based on the Sun's activity. In this study, a system that uses the full power of speckle masking imaging by parallel processing to obtain high-spatial resolution images of the solar surface in near real-time has been developed and built. The application of this system greatly improves the ability to monitor the evolution of solar active regions and to predict the adverse effects of space weather. The data obtained by this system have also been used to study fine structures on the solar surface and their effects on the upper solar atmosphere. A solar active region has been studied using high resolution data obtained by speckle masking imaging. Evolution of a pore in an active region presented. Formation of a rudimentary penumbra is studied. The effects of the change of the magnetic fields on the upper level atmosphere is discussed. Coronal Mass Ejections (CMEs) have a great impact on space weather. To study the relationship between CMEs and filament disappearance, a list of 431 filament and prominence disappearance events has been compiled. Comparison of this list with CME data obtained by satellite has shown that most filament disappearances seem to have no corresponding CME events. Even for the limb events, only thirty percent of filament disappearances are associated with CMEs. A CME event that was observed on March 20, 2000 has been studied in detail. This event did not show the three-parts structure of typical CMEs. The kinematical and morphological properties of this event were examined.

INTERPRETING ERUPTIVE BEHAVIOR IN NOAA AR 11158 VIA THE REGION'S MAGNETIC ENERGY AND RELATIVE-HELICITY BUDGETS

DOE Office of Scientific and Technical Information (OSTI.GOV)

Tziotziou, Kostas; Georgoulis, Manolis K.; Liu Yang

In previous works, we introduced a nonlinear force-free method that self-consistently calculates the instantaneous budgets of free magnetic energy and relative magnetic helicity in solar active regions (ARs). Calculation is expedient and practical, using only a single vector magnetogram per computation. We apply this method to a time series of 600 high-cadence vector magnetograms of the eruptive NOAA AR 11158 acquired by the Helioseismic and Magnetic Imager on board the Solar Dynamics Observatory over a five-day observing interval. Besides testing our method extensively, we use it to interpret the dynamical evolution in the AR, including eruptions. We find that themore » AR builds large budgets of both free magnetic energy and relative magnetic helicity, sufficient to power many more eruptions than the ones it gave within the interval of interest. For each of these major eruptions, we find eruption-related decreases and subsequent free-energy and helicity budgets that are consistent with the observed eruption (flare and coronal mass ejection (CME)) sizes. In addition, we find that (1) evolution in the AR is consistent with the recently proposed (free) energy-(relative) helicity diagram of solar ARs, (2) eruption-related decreases occur before the flare and the projected CME-launch times, suggesting that CME progenitors precede flares, and (3) self terms of free energy and relative helicity most likely originate from respective mutual terms, following a progressive mutual-to-self conversion pattern that most likely stems from magnetic reconnection. This results in the non-ideal formation of increasingly helical pre-eruption structures and instigates further research on the triggering of solar eruptions with magnetic helicity firmly placed in the eruption cadre.« less

The Driving Magnetic Field and Reconnection in CME/Flare Eruptions and Coronal Jets

NASA Technical Reports Server (NTRS)

Moore, Ronald L.

2010-01-01

Signatures of reconnection in major CME (coronal mass ejection)/flare eruptions and in coronal X-ray jets are illustrated and interpreted. The signatures are magnetic field lines and their feet that brighten in flare emission. CME/flare eruptions are magnetic explosions in which: 1. The field that erupts is initially a closed arcade. 2. At eruption onset, most of the free magnetic energy to be released is not stored in field bracketing a current sheet, but in sheared field in the core of the arcade. 3. The sheared core field erupts by a process that from its start or soon after involves fast "tether-cutting" reconnection at an initially small current sheet low in the sheared core field. If the arcade has oppositely-directed field over it, the eruption process from its start or soon after also involves fast "breakout" reconnection at an initially small current sheet between the arcade and the overarching field. These aspects are shown by the small area of the bright field lines and foot-point flare ribbons in the onset of the eruption. 4. At either small current sheet, the fast reconnection progressively unleashes the erupting core field to erupt with progressively greater force. In turn, the erupting core field drives the current sheet to become progressively larger and to undergo progressively greater fast reconnection in the explosive phase of the eruption, and the flare arcade and ribbons grow to become comparable to the pre-eruption arcade in lateral extent. In coronal X-ray jets: 1. The magnetic energy released in the jet is built up by the emergence of a magnetic arcade into surrounding unipolar "open" field. 2. A simple jet is produced when a burst of reconnection occurs at the current sheet between the arcade and the open field. This produces a bright reconnection jet and a bright reconnection arcade that are both much smaller in diameter that the driving arcade. 3. A more complex jet is produced when the arcade has a sheared core field and undergoes an ejective eruption in the manner of a miniature CME/flare eruption. The jet is then a combination of a miniature CME and the products of more widely distributed reconnection of the erupting arcade with the open field than in simple jets.

Thermal Evolution of a Failed Flux Rope Eruption Revealed by Temperature Maps

NASA Astrophysics Data System (ADS)

Song, H.; Zhang, J.; CHEN, Y.

2013-12-01

Flux rope is generally considered to be the fundamental magnetic configuration of a coronal mass ejection (CME). Recent observations suggest that hot channel or blob structures during the eruptions be the direct observational manifestation of flux ropes. In this study, we report our analysis of thermal evolution of a failed solar eruption with an apparent flux rope embedded. The thermal structure of the eruption is revealed through differential emission measure (DEM) analysis technique, which shows detailed temperature maps in both high spatial resolution and high temperature resolution based on SDO/AIA observations. Our results show that the flux rope exists in the corona before the eruption, and its temperature can quickly rise to over 10 MK within one minute of the eruption. The correlation study between the flux rope temperature and the soft x-ray flux suggests that the flux rope should be heated through the direct thermal energy release of magnetic reconnection. Further, we study the kinematic evolution process of the flux rope, in an effort to find the physical mechanism that prevents the magnetic rope eruption to become a full coronal mass ejection. This kind of study using temperature maps might reveal where and when magnetic reconnection takes place during solar eruptions.