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Sample records for flare unshearing motions

  1. Sheared and unsheared rotation of driven dust clusters

    SciTech Connect

    Schablinski, Jan; Block, Dietmar; Carstensen, Jan; Greiner, Franko; Piel, Alexander

    2014-07-15

    Finite size plasma crystals confined in an anisotropic potential well were studied under a rotating and radially unsheared drive in experiment and simulation at moderate rotational frequencies. A radially sheared rotation of these strongly coupled systems is observed for most cluster configurations with a low symmetry. The results show that a differential rotation can be effected by a non-sheared driving force.

  2. Serf studies of mass motions arising in flares

    SciTech Connect

    Wagner, W.J.

    1982-01-01

    It is believed that radio type IVs, co-spatial with dense hot plasmoids, may be the result of a plasma radiation emission mechanism. The injection of mass into the corona was recently observed in chromospheric and coronal lines with magnetic field changes and also at very high speeds into loops. The start time of coronal loop transients, if extrapolated to the chromosphere, in most cases precedes flare H-alpha or X-ray emission. Observational inferences from polarization and other studies are seen as favoring the three-dimensional bubble over the planar loop as a description of coronal mass motions.

  3. HINODE OBSERVATIONS OF COHERENT LATERAL MOTION OF PENUMBRAL FILAMENTS DURING AN X-CLASS FLARE

    SciTech Connect

    Gosain, S.; Venkatakrishnan, P.; Tiwari, Sanjiv Kumar

    2009-12-01

    The X-3.4 class flare of 2006 December 13 was observed with a high cadence of 2 minutes at 0.2 arcsec resolution by HINODE/SOT FG instrument. The flare ribbons could be seen in G-band images also. A careful analysis of these observations after proper registration of images shows flare-related changes in penumbral filaments of the associated sunspot for the first time. The observations of sunspot deformation, decay of penumbral area, and changes in magnetic flux during large flares have been reported earlier in the literature. In this Letter, we report lateral motion of the penumbral filaments in a sheared region of the delta-sunspot during the X-class flare. Such shifts have not been seen earlier. The lateral motion occurs in two phases: (1) motion before the flare ribbons move across the penumbral filaments and (2) motion afterward. The former motion is directed away from expanding flare ribbons and lasts for about 4 minutes. The latter motion is directed in the opposite direction and lasts for more than 40 minutes. Further, we locate a patch in adjacent opposite polarity spot moving in opposite direction to the penumbral filaments. Together these patches represent conjugate footpoints on either side of the polarity inversion line, moving toward each other. This converging motion could be interpreted as shrinkage of field lines.

  4. Coherent Lateral Motion of Penumbral Filaments during the X-class Flare of 13 December 2006

    NASA Astrophysics Data System (ADS)

    Gosain, S.; Venkatakrishnan, P.; Tiwari, S. K.

    2012-08-01

    The high-resolution pictures of the solar photosphere from space based 50 cm Solar Optical Telescope (SOT) onboard Hinode spacecraft, are now routinely observed. Such images of a δ-sunspot in NOAA 10930 were obtained by Hinode during 13 December 2006 while a X-class flare occurred in this active region. Two bright ribbons were visible even in white light and G-band images apart from chromospheric Ca II H images. We register the sunspot globally using cross-correlation technique and analyse local effects during flare interval. We find that during flare the penumbral filaments show lateral motion. Also, we locate two patches, one in either polarity, which show converging motion towards the polarity inversion line (PIL). In Ca II H images we find kernel with pre-flare brightening which lie along the PIL.

  5. EVIDENCE OF SOLAR FLARE TRIGGERING DUE TO LOOP-LOOP INTERACTION CAUSED BY FOOTPOINT SHEAR MOTION

    SciTech Connect

    Kumar, Pankaj; Srivastava, A. K.; Uddin, Wahab; Somov, B. V.; Manoharan, P. K.; Erdelyi, R. E-mail: aks@aries.res.i

    2010-11-10

    We analyze multi-wavelength data of an M7.9/1N class solar flare which occurred on 2006 April 27 in AR NOAA 10875. GOES soft X-ray images provide the most likely signature of two interacting loops and their reconnection, which triggers the solar flare. TRACE 195 A images also reveal the loop-loop interaction and the formation of 'X' points with converging motion ({approx}30 km s{sup -1}) at the reconnection site in between this interacting loop system. This provides evidence of progressive reconnection and flare maximization at the interaction site in the active region. The absence of type III radio bursts during this time period indicates no opening of magnetic field lines during the flare energy release, which implies that the change of field line connectivity/orientation occurred only during the loop-loop interaction and reconnection process. The Ondrejov dynamic radio spectrum shows an intense decimetric (DCIM) radio burst (2.5-4.5 GHz, duration {approx}3 minutes) during the flare initiation, which reveals the signature of particle acceleration from the reconnection site during loop-loop interaction. The double-peak structures at 4.9 and 8.8 GHz provide the most likely confirmatory signature of the loop-loop interaction at the flare site in the active region. RHESSI hard X-ray images also show the loop-top and footpoint sources of the corresponding two-loop system, which act like current-carrying flux tubes with resultant opposite magnetic fields and net force of attraction, and their coalescence during the flare maximum. We also suggest that the shear motion/rotation of the footpoint of the smaller loop, which is anchored in the opposite polarity spot, may be responsible for the flare energy buildup and its eventual release due to the loop-loop interaction.

  6. SUDDEN PHOTOSPHERIC MOTION AND SUNSPOT ROTATION ASSOCIATED WITH THE X2.2 FLARE ON 2011 FEBRUARY 15

    SciTech Connect

    Wang, Shuo; Liu, Chang; Deng, Na; Wang, Haimin

    2014-02-20

    The Helioseismic and Magnetic Imager provides 45 s cadence intensity images and 720 s cadence vector magnetograms. These unprecedented high-cadence and high-resolution data give us a unique opportunity to study the change of photospheric flows and sunspot rotations associated with flares. By using the differential affine velocity estimator method and the Fourier local correlation tracking method separately, we calculate velocity and vorticity of photospheric flows in the flaring NOAA AR 11158, and investigate their temporal evolution around the X2.2 flare on 2011 February 15. It is found that the shear flow around the flaring magnetic polarity inversion line exhibits a sudden decrease, and both of the two main sunspots undergo a sudden change in rotational motion during the impulsive phase of the flare. These results are discussed in the context of the Lorentz-force change that was proposed by Hudson et al. and Fisher et al. This mechanism can explain the connections between the rapid and irreversible photospheric vector magnetic field change and the observed short-term motions associated with the flare. In particular, the torque provided by the horizontal Lorentz force change agrees with what is required for the measured angular acceleration.

  7. Motion of 3-6 keV Nonthermal Sources Along the Legs of a Flare Loop

    NASA Technical Reports Server (NTRS)

    Sui, Linhui; Holman, Gordon D.; Dennis, Brian R.

    2007-01-01

    Observations of nonthermal X-ray sources me critical to studying electron acceleration and transport in solar flares. Strong thermal emission radiated from the preheated plasma before the flare impulsive phase often makes it difficult to detect low-energy X-ray sources that are produced by relatively low-energy nonthermal electrons. Knowledge of the distribution of these low-energy nonthermal electrons is particularly important in determining the total nonthermal electron energy in solar flares. We report on an 'early impulsive flare' in which impulsive hard X-ray emission was seen early in the flare before the soft X-ray emission had risen significantly, indicating limited plasma pre-heating. Early in the flare, RHESSI < 25 keV images show coronal sources that moved first downward and then upwards along the legs of a flare loop. In particular, the 3-6 keV source appeared as a single coronal source at the start of the flare, and then it involved into two coronal sources moving down along the two legs of the loop. After nearly reaching the two footpoints at the hard X-ray peak, the two sources moved back up to the looptop again. RHESSI images and light curves all indicate that nonthermal emission dominated at energies as low as 3-6 keV. We suggest that the evolution of both the spectral index and the low-energy cutoff of the injected electron distribution could result in the accelerated electrons reaching a lower altitude along the legs of the dense flare loop and hence result in the observed downward and upward motions of the nonthermal sources.

  8. First evidence of non-Gaussian solar flare EUV spectral line profiles and accelerated non-thermal ion motion

    NASA Astrophysics Data System (ADS)

    Jeffrey, Natasha L. S.; Fletcher, Lyndsay; Labrosse, Nicolas

    2016-05-01

    Context. The properties of solar flare plasma can be determined from the observation of optically thin lines. The emitting ion distribution determines the shape of the spectral line profile, with an isothermal Maxwellian ion distribution producing a Gaussian profile. Non-Gaussian line profiles may indicate more complex ion distributions. Aims: We investigate the possibility of determining flare-accelerated non-thermal ion and/or plasma velocity distributions. Methods: We study EUV spectral lines produced during a flare SOL2013-05-15T01:45 using the Hinode EUV Imaging Spectrometer (EIS). The flare is located close to the eastern solar limb with an extended loop structure, allowing the different flare features: ribbons, hard X-ray (HXR) footpoints and the loop-top source to be clearly observed in UV, EUV and X-rays. EUV line spectroscopy is performed in seven different regions covering the flare. We study the line profiles of the isolated and unblended Fe XVI lines (λ262.9760 Å ) mainly formed at temperatures of ~2 to 4 MK. Suitable Fe XVI line profiles at one time close to the peak soft X-ray emission and free of directed mass motions are examined using: 1. a higher moments analysis, 2. Gaussian fitting, and 3. by fitting a kappa distribution line profile convolved with a Gaussian to account for the EIS instrumental profile. Results: Fe XVI line profiles in the flaring loop-top, HXR footpoint and ribbon regions can be confidently fitted with a kappa line profile with an extra variable κ, giving low, non-thermal κ values between 2 and 3.3. An independent higher moments analysis also finds that many of the spectral line kurtosis values are higher than the Gaussian value of 3, even with the presence of a broad Gaussian instrumental profile. Conclusions: A flare-accelerated non-thermal ion population could account for both the observed non-Gaussian line profiles, and for the Fe XVI "excess" broadening found from Gaussian fitting, if the emitting ions are interacting

  9. ON THE INJECTION OF HELICITY BY THE SHEARING MOTION OF FLUXES IN RELATION TO FLARES AND CORONAL MASS EJECTIONS

    SciTech Connect

    Vemareddy, P.; Ambastha, A.; Maurya, R. A.; Chae, J. E-mail: ambastha@prl.res.in E-mail: jcchae@snu.ac.kr

    2012-12-20

    An investigation of helicity injection by photospheric shear motions is carried out for two active regions (ARs), NOAA 11158 and 11166, using line-of-sight magnetic field observations obtained from the Helioseismic and Magnetic Imager on board the Solar Dynamics Observatory. We derived the horizontal velocities in the ARs from the differential affine velocity estimator (DAVE) technique. Persistent strong shear motions at maximum velocities in the range of 0.6-0.9 km s{sup -1} along the magnetic polarity inversion line and outward flows from the peripheral regions of the sunspots were observed in the two ARs. The helicities injected in NOAA 11158 and 11166 during their six-day evolution period were estimated as 14.16 Multiplication-Sign 10{sup 42} Mx{sup 2} and 9.5 Multiplication-Sign 10{sup 42} Mx{sup 2}, respectively. The estimated injection rates decreased up to 13% by increasing the time interval between the magnetograms from 12 minutes to 36 minutes, and increased up to 9% by decreasing the DAVE window size from 21 Multiplication-Sign 18 to 9 Multiplication-Sign 6 pixel{sup 2}, resulting in 10% variation in the accumulated helicity. In both ARs, the flare-prone regions (R2) had inhomogeneous helicity flux distribution with mixed helicities of both signs and coronal mass ejection (CME) prone regions had almost homogeneous distribution of helicity flux dominated by a single sign. The temporal profiles of helicity injection showed impulsive variations during some flares/CMEs due to negative helicity injection into the dominant region of positive helicity flux. A quantitative analysis reveals a marginally significant association of helicity flux with CMEs but not flares in AR 11158, while for the AR 11166, we find a marginally significant association of helicity flux with flares but not CMEs, providing evidence of the role of helicity injection at localized sites of the events. These short-term variations of helicity flux are further discussed in view of possible

  10. Plasma motions and non-thermal line broadening in flaring twisted coronal loops

    NASA Astrophysics Data System (ADS)

    Gordovskyy, M.; Kontar, E. P.; Browning, P. K.

    2016-05-01

    Context. Observation of coronal extreme ultra-violet (EUV) spectral lines sensitive to different temperatures offers an opportunity to evaluate the thermal structure and flows in flaring atmospheres. This, in turn, can be used to estimate the partitioning between the thermal and kinetic energies released in flares. Aims: Our aim is to forward-model large-scale (50-10 000 km) velocity distributions to interpret non-thermal broadening of different spectral EUV lines observed in flares. The developed models allow us to understand the origin of the observed spectral line shifts and broadening, and link these features to particular physical phenomena in flaring atmospheres. Methods: We use ideal magnetohydrodynamics (MHD) to derive unstable twisted magnetic fluxtube configurations in a gravitationally stratified atmosphere. The evolution of these twisted fluxtubes is followed using resistive MHD with anomalous resistivity depending on the local density and temperature. The model also takes thermal conduction and radiative losses in the continuum into account. The model allows us to evaluate average velocities and velocity dispersions, which would be interpreted as non-thermal velocities in observations, at different temperatures for different parts of the models. Results: Our models show qualitative and quantitative agreement with observations. Thus, the line-of-sight (LOS) velocity dispersions demonstrate substantial correlation with the temperature, increasing from about 20-30 km s-1 around 1 MK to about 200-400 km s-1 near 10-20 MK. The average LOS velocities also correlate with velocity dispersions, although they demonstrate a very strong scattering compared to the observations. We also note that near footpoints the velocity dispersions across the magnetic field are systematically lower than those along the field. We conclude that the correlation between the flow velocities, velocity dispersions, and temperatures are likely to indicate that the same heating

  11. POSSIBLE DETECTION OF APPARENT SUPERLUMINAL INWARD MOTION IN MARKARIAN 421 AFTER THE GIANT X-RAY FLARE IN 2010 FEBRUARY

    SciTech Connect

    Niinuma, K.; Kino, M.; Oyama, T.; Nagai, H.; Isobe, N.; Gabanyi, K. E.; Hada, K.; Koyama, S.; Asada, K.; Fujisawa, K.

    2012-11-10

    We report on the very long baseline interferometry (VLBI) follow-up observations using the Japanese VLBI Network array at 22 GHz for the largest X-ray flare of TeV blazar Mrk 421 that occurred in 2010 mid-February. The total of five epochs of observations were performed at intervals of about 20 days between 2010 March 7 and May 31. No newborn component associated with the flare was seen directly in the total intensity images obtained by our multi-epoch VLBI observations. However, one jet component located at {approx}1 mas northwest from the core was able to be identified, and its proper motion can be measured as -1.66 {+-} 0.46 mas yr{sup -1}, which corresponds to an apparent velocity of -3.48 {+-} 0.97c. Here, this negative velocity indicates that the jet component was apparently moving toward the core. As the most plausible explanation, we discuss that the apparent negative velocity was possibly caused by the ejection of a new component, which could not be resolved with our observations. In this case, the obtained Doppler factor of the new component is around 10-20, which is consistent with the ones typically estimated by model fittings of spectral energy distribution for this source.

  12. The Growth, Polarization and Motion of the Radio Afterglow from the Giant Flare from SGR 1806-20

    NASA Technical Reports Server (NTRS)

    Taylor, G. B.; Gelfand, J. D.; Gaensler, B. M.; Granot, J.; Kouveliotou, C.; Fender, R. P.; Ramirez-Ruiz, E.; Eichler, D.; Lyubarsky, Y. E.; Garrett, M.

    2005-01-01

    The extraordinary giant flare (GF) of 2004 December 27 from the soft gamma repeater (SGR) 1806-20 was followed by a bright radio afterglow. We present an analysis of VLA observations of this radio afterglow from SGR 1806-20, consisting of previously reported 8.5 GHz data covering days 7 to 20 after the GF, plus new observations at 8.5 and 22 GHz from day 24 to 81. We find a deceleration in the expansion, from approximately 4.5 mas/day to less than 2.5 mas/day. The time of deceleration is roughly coincident with the rebrightening in the radio light curve, as expected to result when the ejecta from the GF sweeps up enough of the external medium, and transitions from a coasting phase to the Sedov-Taylor regime. The radio afterglow is elongated and maintains a 2:l axis ratio with an average position angle of -40 degrees (north through east), oriented perpendicular to the average intrinsic linear polarization angle. We also report on the discovery of motion in the flux centroid of the afterglow, at an average velocity of 0.26 plus or minus 0.03 c (assuming a distance of 15 kpc) at a position angle of -40 degrees. This motion, in combination with the growth and polarization measurements, suggests an initially asymmetric outflow, mainly from one side of the magnetar.

  13. Fast launch speeds in radio flares, from a new determination of the intrinsic motions of SS 433's jet bolides

    NASA Astrophysics Data System (ADS)

    Jeffrey, Robert M.; Blundell, Katherine M.; Trushkin, Sergei A.; Mioduszewski, Amy J.

    2016-09-01

    We present new high-resolution, multi-epoch, Very Long Baseline Array (VLBA) radio images of the Galactic microquasar SS 433. We are able to observe plasma knots in the milliarcsecond-scale jets more than 50 d after their launch. This unprecedented baseline in time allows us to determine the bulk launch speed of the radio-emitting plasma during a radio flare, using a new method which we present here, and which is completely independent of optical spectroscopy. We also apply this method to an earlier sequence of 39 short daily VLBA observations, which cover a period in which SS 433 moved from quiescence into a flare. In both data sets we find, for the first time at radio wavebands, clear evidence that the launch speeds of the milliarcsecond-scale jets rise as high as 0.32c during flaring episodes. By comparing these images of SS 433 with photometric radio monitoring from the RATAN-600 telescope, we explore further properties of these radio flares.

  14. Flare Hybrids

    NASA Astrophysics Data System (ADS)

    Tomczak, M.; Dubieniecki, P.

    2015-12-01

    On the basis of the Solar Maximum Mission observations, Švestka ( Solar Phys. 121, 399, 1989) introduced a new class of flares, the so-called flare hybrids. When they start, they look like typical compact flares (phase 1), but later on, they look like flares with arcades of magnetic loops (phase 2). We summarize the characteristic features of flare hybrids in soft and hard X-rays as well as in the extreme ultraviolet; these features allow us to distinguish flare hybrids from other flares. In this article, additional energy release or long plasma cooling timescales are suggested as possible causes of phase 2. We estimate the frequency of flare hybrids, and study the magnetic configurations favorable for flare hybrid occurrence. Flare hybrids appear to be quite frequent, and the difference between the lengths of magnetic loops in the two interacting loop systems seem to be a crucial parameter for determining their characteristics.

  15. Statistical aspects of solar flares

    NASA Technical Reports Server (NTRS)

    Wilson, Robert M.

    1987-01-01

    A survey of the statistical properties of 850 H alpha solar flares during 1975 is presented. Comparison of the results found here with those reported elsewhere for different epochs is accomplished. Distributions of rise time, decay time, and duration are given, as are the mean, mode, median, and 90th percentile values. Proportions by selected groupings are also determined. For flares in general, mean values for rise time, decay time, and duration are 5.2 + or - 0.4 min, and 18.1 + or 1.1 min, respectively. Subflares, accounting for nearly 90 percent of the flares, had mean values lower than those found for flares of H alpha importance greater than 1, and the differences are statistically significant. Likewise, flares of bright and normal relative brightness have mean values of decay time and duration that are significantly longer than those computed for faint flares, and mass-motion related flares are significantly longer than non-mass-motion related flares. Seventy-three percent of the mass-motion related flares are categorized as being a two-ribbon flare and/or being accompanied by a high-speed dark filament. Slow rise time flares (rise time greater than 5 min) have a mean value for duration that is significantly longer than that computed for fast rise time flares, and long-lived duration flares (duration greater than 18 min) have a mean value for rise time that is significantly longer than that computed for short-lived duration flares, suggesting a positive linear relationship between rise time and duration for flares. Monthly occurrence rates for flares in general and by group are found to be linearly related in a positive sense to monthly sunspot number. Statistical testing reveals the association between sunspot number and numbers of flares to be significant at the 95 percent level of confidence, and the t statistic for slope is significant at greater than 99 percent level of confidence. Dependent upon the specific fit, between 58 percent and 94 percent of

  16. Solar flares

    NASA Technical Reports Server (NTRS)

    Zirin, H.

    1974-01-01

    A review of the knowledge about solar flares which has been obtained through observations from the earth and from space by various methods. High-resolution cinematography is best carried out at H-alpha wavelengths to reveal the structure, time history, and location of flares. The classification flares in H alpha according to either physical or morphological criteria is discussed. The study of flare morphology, which shows where, when, and how flares occur, is important for evaluating theories of flares. Consideration is given to studies of flares by optical spectroscopy, radio emissions, and at X-ray and XUV wavelengths. Research has shown where and possibly why flares occur, but the physics of the instability involved, of the particle acceleration, and of the heating are still not understood.

  17. Solar Flares

    NASA Technical Reports Server (NTRS)

    Savage, Sabrina

    2013-01-01

    Because the Earth resides in the atmosphere of our nearest stellar neighbor, events occurring on the Sun's surface directly affect us by interfering with satellite operations and communications, astronaut safety, and, in extreme circumstances, power grid stability. Solar flares, the most energetic events in our solar system, are a substantial source of hazardous space weather affecting our increasingly technology-dependent society. While flares have been observed using ground-based telescopes for over 150 years, modern space-bourne observatories have provided nearly continuous multi-wavelength flare coverage that cannot be obtained from the ground. We can now probe the origins and evolution of flares by tracking particle acceleration, changes in ionized plasma, and the reorganization of magnetic fields. I will walk through our current understanding of why flares occur and how they affect the Earth and also show several examples of these fantastic explosions.

  18. Radiation hydrodynamics in solar flares

    SciTech Connect

    Fisher, G.H.

    1985-10-18

    Solar flares are rather violent and extremely complicated phenomena, and it should be made clear at the outset that a physically complete picture describing all aspects of flares does not exist. From the wealth of data which is available, it is apparent that many different types of physical processes are involved during flares: energetic particle acceleration, rapid magnetohydrodynamic motion of complex field structures, magnetic reconnection, violent mass motion along magnetic field lines, and the heating of plasma to tens of millions of degrees, to name a few. The goal of this paper is to explore just one aspect of solar flares, namely, the interaction of hydrodynamics and radiation processes in fluid being rapidly heated along closed magnetic field lines. The models discussed are therefore necessarily restrictive, and will address only a few of the observed or observable phenomena. 46 refs., 6 figs.

  19. Flare models: Chapter 9 of solar flares

    NASA Technical Reports Server (NTRS)

    Sturrock, P. A. (Editor)

    1979-01-01

    By reviewing the properties of solar flares analyzed by each of the seven teams of the Skylab workshop, a set of primary and secondary requirements of flare models are derived. A number of flare models are described briefly and their properties compared with the primary requirements. It appears that, at this time, each flare model has some strong points and some weak points. It has not yet been demonstrated that any one flare model meets all the proposed requirements.

  20. Motion.

    ERIC Educational Resources Information Center

    Brand, Judith, Ed.

    2002-01-01

    This issue of Exploratorium Magazine focuses on the topic of motion. Contents include: (1) "First Word" (Zach Tobias); (2) "Cosmic Collisions" (Robert Irion); (3) "The Mobile Cell" (Karen E. Kalumuck); (4) "The Paths of Paths" (Steven Vogel); (5) "Fragments" (Pearl Tesler); (6) "Moving Pictures" (Amy Snyder); (7) "Plants on the Go" (Katharine…

  1. OBSERVATIONS OF CHROMOSPHERIC FLARE RE-BRIGHTENINGS

    SciTech Connect

    Miklenic, C. H.; Veronig, A. M.; Vrsnak, B.; Barta, M.

    2010-08-20

    We investigate an active region that produced three C-class flares and one M-class flare within 2.5 hr. The morphology and location of the C-flares indicate that these events constitute a set of homologous flares. Radio observations indicate the occurrence of a downward-moving plasmoid during the impulsive phase of the M flare. We use TRACE 1700 A filtergrams and SOHO Michelson Doppler Imager magnetograms to examine the character of the UV brightenings; i.e., we search for re-brightenings of former flare areas both across the series of events and within one and the same event. We find that essentially the same footpoints re-brighten in each C flare. Based on the progression of both the derived magnetic flux change rate and the observed Radio Solar Telescope Network microwave emission, we speculate about a further re-brightening during the decay phase of the M flare as a further member of the series of homologous flares. We conclude that the 'postflare' field is driven to repeated eruption by continuous, shear-increasing, horizontal, photospheric flows, as one end of the involved magnetic arcade is anchored in the penumbra of a large sunspot. The observed motion pattern of the UV kernels indicates that the arcade evolves during the series of events from a both highly sheared and heavily entangled state to a still sheared but more organized state.

  2. CIRCULAR RIBBON FLARES AND HOMOLOGOUS JETS

    SciTech Connect

    Wang Haimin; Liu Chang

    2012-12-01

    Solar flare emissions in the chromosphere often appear as elongated ribbons on both sides of the magnetic polarity inversion line (PIL), which has been regarded as evidence of a typical configuration of magnetic reconnection. However, flares having a circular ribbon have rarely been reported, although it is expected in the fan-spine magnetic topology involving reconnection at a three-dimensional (3D) coronal null point. We present five circular ribbon flares with associated surges, using high-resolution and high-cadence H{alpha} blue wing observations obtained from the recently digitized films of Big Bear Solar Observatory. In all the events, a central parasitic magnetic field is encompassed by the opposite polarity, forming a circular PIL traced by filament material. Consequently, a flare kernel at the center is surrounded by a circular flare ribbon. The four homologous jet-related flares on 1991 March 17 and 18 are of particular interest, as (1) the circular ribbons brighten sequentially, with cospatial surges, rather than simultaneously, (2) the central flare kernels show an intriguing 'round-trip' motion and become elongated, and (3) remote brightenings occur at a region with the same magnetic polarity as the central parasitic field and are co-temporal with a separate phase of flare emissions. In another flare on 1991 February 25, the circular flare emission and surge activity occur successively, and the event could be associated with magnetic flux cancellation across the circular PIL. We discuss the implications of these observations combining circular flare ribbons, homologous jets, and remote brightenings for understanding the dynamics of 3D magnetic restructuring.

  3. Flares and Their Underlying Magnetic Complexity

    NASA Astrophysics Data System (ADS)

    Engell, Alexander J.; Siarkowski, Marek; Gryciuk, Magda; Sylwester, Janusz; Sylwester, Barbara; Golub, Leon; Korreck, Kelly; Cirtain, Jonathan

    2011-01-01

    SphinX (Solar PHotometer IN X-rays), a full-disk-integrated spectrometer, observed 137 flare-like/transient events with active region (AR) 11024 being the only AR on disk. The Hinode X-Ray Telescope (XRT) and Solar Optical Telescope observe 67 of these events and identified their location from 12:00 UT on July 3 through 24:00 UT 2009 July 7. We find that the predominant mechanisms for flares observed by XRT are (1) flux cancellation and (2) the shearing of underlying magnetic elements. Point- and cusp-like flare morphologies seen by XRT all occur in a magnetic environment where one polarity is impeded by the opposite polarity and vice versa, forcing the flux cancellation process. The shearing is either caused by flux emergence at the center of the AR and separation of polarities along a neutral line or by individual magnetic elements having a rotational motion. Both mechanisms are observed to contribute to single- and multiple-loop flares. We observe that most loop flares occur along a large portion of a polarity inversion line. Point- and cusp-like flares become more infrequent as the AR becomes organized with separation of the positive and negative polarities. SphinX, which allows us to identify when these flares occur, provides us with a statistically significant temperature and emission scaling law for A and B class flares: EM = 6.1 × 1033 T 1.9±0.1.

  4. FLARES AND THEIR UNDERLYING MAGNETIC COMPLEXITY

    SciTech Connect

    Engell, Alexander J.; Golub, Leon; Korreck, Kelly; Siarkowski, Marek; Gryciuk, Magda; Sylwester, Janusz; Sylwester, Barbara; Cirtain, Jonathan

    2011-01-01

    SphinX (Solar PHotometer IN X-rays), a full-disk-integrated spectrometer, observed 137 flare-like/transient events with active region (AR) 11024 being the only AR on disk. The Hinode X-Ray Telescope (XRT) and Solar Optical Telescope observe 67 of these events and identified their location from 12:00 UT on July 3 through 24:00 UT 2009 July 7. We find that the predominant mechanisms for flares observed by XRT are (1) flux cancellation and (2) the shearing of underlying magnetic elements. Point- and cusp-like flare morphologies seen by XRT all occur in a magnetic environment where one polarity is impeded by the opposite polarity and vice versa, forcing the flux cancellation process. The shearing is either caused by flux emergence at the center of the AR and separation of polarities along a neutral line or by individual magnetic elements having a rotational motion. Both mechanisms are observed to contribute to single- and multiple-loop flares. We observe that most loop flares occur along a large portion of a polarity inversion line. Point- and cusp-like flares become more infrequent as the AR becomes organized with separation of the positive and negative polarities. SphinX, which allows us to identify when these flares occur, provides us with a statistically significant temperature and emission scaling law for A and B class flares: EM = 6.1 x 10{sup 33} T{sup 1.9{+-}0.1}.

  5. A dynamic flare with anomalously dense flare loops

    NASA Technical Reports Server (NTRS)

    Svestka, Z.; Fontenla, J. M.; Machado, M. E.; Martin, S. F.; Neidig, D. F.

    1986-01-01

    The dynamic flare of November 6, 1980 developed a rich system of growing loops which could be followed in H-alpha for 1.5 hours. Throughout the flare, these loops, near the limb, were seen in emission against the disk. Theoretical computations of b-values for a hydrogen atom reveal that this requires electron densities in the loops to be close to 10 to the 12th per cu cm. From measured widths of higher Balmer lines the density at the tops of the loops was found to be 4 x 10 to the 12th per cu cm if no nonthermal motions were present. It is now general knowledge that flare loops are initially observed in X-rays and become visible in H-alpha only after cooling. For such a high density a loop would cool through radiation from 10 to the 7th K to 10 to the 4th K within a few minutes so that the dense H-alpha loops should have heights very close to the heights of the X-ray loops. This, however, contradicts the observations obtained by the HXIS and FCS instruments on board SMM which show the X-ray loops at much higher altitudes than the loops in H-alpha. Therefore, the density must have been significantly smaller when the loops were formed and the flare loops were apparently both shrinking and becoming denser while cooling.

  6. RE-FLARING OF A POST-FLARE LOOP SYSTEM DRIVEN BY FLUX ROPE EMERGENCE AND TWISTING

    SciTech Connect

    Cheng, X.; Ding, M. D.; Guo, Y.; Zhang, J.; Jing, J.; Wiegelmann, T.

    2010-06-10

    In this Letter, we study in detail the evolution of the post-flare loops on 2005 January 15 that occurred between two consecutive solar eruption events, both of which generated a fast halo coronal mass ejection (CME) and a major flare. The post-flare loop system, formed after the first CME/flare eruption, evolved rapidly, as manifested by the unusual accelerating rise motion of the loops. Through nonlinear force-free field models, we obtain the magnetic structure over the active region. It clearly shows that the flux rope below the loops also kept rising, accompanied with increasing twist and length. Finally, the post-flare magnetic configuration evolved to a state that resulted in the second CME/flare eruption. This is an event in which the post-flare loops can re-flare in a short period of {approx}16 hr following the first CME/flare eruption. The observed re-flaring at the same location is likely driven by the rapid evolution of the flux rope caused by the magnetic flux emergence and the rotation of the sunspot. This observation provides valuable information on CME/flare models and their prediction.

  7. Understanding Solar Flare Statistics

    NASA Astrophysics Data System (ADS)

    Wheatland, M. S.

    2005-12-01

    A review is presented of work aimed at understanding solar flare statistics, with emphasis on the well known flare power-law size distribution. Although avalanche models are perhaps the favoured model to describe flare statistics, their physical basis is unclear, and they are divorced from developing ideas in large-scale reconnection theory. An alternative model, aimed at reconciling large-scale reconnection models with solar flare statistics, is revisited. The solar flare waiting-time distribution has also attracted recent attention. Observed waiting-time distributions are described, together with what they might tell us about the flare phenomenon. Finally, a practical application of flare statistics to flare prediction is described in detail, including the results of a year of automated (web-based) predictions from the method.

  8. The cooling and condensation of flare coronal plasma

    NASA Technical Reports Server (NTRS)

    Antiochos, S. K.; Sturrock, P. A.

    1981-01-01

    A model is investigated for the decay of flare heated coronal loops in which rapid radiative cooling at the loop base creates strong pressure gradients which, in turn, generate large (supersonic) downward flows. The coronal material cools and 'condenses' onto the flare chromosphere. The features which distinguish this model from previous models of flare cooling are: (1) most of the thermal energy of the coronal plasma may be lost by mass motion rather than by conduction or coronal radiation; (2) flare loops are not isobaric during their decay phase, and large downward velocities are present near the footpoints; (3) the differential emission measure q has a strong temperature dependence.

  9. The EVE Doppler Sensitivity and Flare Observations

    NASA Technical Reports Server (NTRS)

    Hudson, H. S.; Woods, T. N.; Chamberlin, P. C.; Didkovsky, L.; Del Zanna, G.

    2011-01-01

    The Extreme-ultraviolet Variability Experiment (EVE) obtains continuous EUV spectra of the Sun viewed as a star. Its primary objective is the characterization of solar spectral irradiance, but its sensitivity and stability make it extremely interesting for observations of variability on time scales down to the limit imposed by its basic 10 s sample interval. In this paper we characterize the Doppler sensitivity of the EVE data. We find that the 30.4 nm line of He II has a random Doppler error below 0.001 nm (1 pm, better than 10 km/s as a redshift), with ample stability to detect the orbital motion of its satellite, the Solar Dynamics Observatory (SDO). Solar flares also displace the spectrum, both because of Doppler shifts and because of EVE's optical layout, which (as with a slitless spectrograph) confuses position and wavelength. As a flare develops, the centroid of the line displays variations that reflect Doppler shifts and therefore flare dynamics. For the impulsive phase of the flare SOL2010-06-12, we find the line centroid to have a redshift of 16.8 +/- 5.9 km/s relative to that of the flare gradual phase (statistical errors only). We find also that high-temperature lines, such as Fe XXIV 19.2 nm, have well-determined Doppler components for major flares, with decreasing apparent blueshifts as expected from chromospheric evaporation flows.

  10. SUNSPOT ROTATION, FLARE ENERGETICS, AND FLUX ROPE HELICITY: THE HALLOWEEN FLARE ON 2003 OCTOBER 28

    SciTech Connect

    Kazachenko, Maria D.; Canfield, Richard C.; Longcope, Dana W.; Qiu Jiong

    2010-10-20

    We study the X17 eruptive flare on 2003 October 28 using Michelson Doppler Imager observations of photospheric magnetic and velocity fields and TRACE 1600 A images of the flare in a three-dimensional model of energy buildup and release in NOAA 10486. The most dramatic feature of this active region is the 123{sup 0} rotation of a large positive sunspot over 46 hr prior to the event. We apply a method for including such rotation in the framework of the minimum current corona model of the buildup of energy and helicity due to the observed motions. We distinguish between helicity and energy stored in the whole active region and that released in the flare itself. We find that while the rotation of a sunspot contributes significantly to the energy and helicity budgets of the whole active region, it makes only a minor contribution to that part of the region that flares. We conclude that in spite of the fast rotation, shearing motions alone store sufficient energy and helicity to account for the flare energetics and interplanetary coronal mass ejection helicity content within their observational uncertainties. Our analysis demonstrates that the relative importance of shearing and rotation in this flare depends critically on their location within the parent active region topology.

  11. Solar Flares: Magnetohydrodynamic Processes

    NASA Astrophysics Data System (ADS)

    Shibata, Kazunari; Magara, Tetsuya

    2011-12-01

    This paper outlines the current understanding of solar flares, mainly focused on magnetohydrodynamic (MHD) processes responsible for producing a flare. Observations show that flares are one of the most explosive phenomena in the atmosphere of the Sun, releasing a huge amount of energy up to about 10^32 erg on the timescale of hours. Flares involve the heating of plasma, mass ejection, and particle acceleration that generates high-energy particles. The key physical processes for producing a flare are: the emergence of magnetic field from the solar interior to the solar atmosphere (flux emergence), local enhancement of electric current in the corona (formation of a current sheet), and rapid dissipation of electric current (magnetic reconnection) that causes shock heating, mass ejection, and particle acceleration. The evolution toward the onset of a flare is rather quasi-static when free energy is accumulated in the form of coronal electric current (field-aligned current, more precisely), while the dissipation of coronal current proceeds rapidly, producing various dynamic events that affect lower atmospheres such as the chromosphere and photosphere. Flares manifest such rapid dissipation of coronal current, and their theoretical modeling has been developed in accordance with observations, in which numerical simulations proved to be a strong tool reproducing the time-dependent, nonlinear evolution of a flare. We review the models proposed to explain the physical mechanism of flares, giving an comprehensive explanation of the key processes mentioned above. We start with basic properties of flares, then go into the details of energy build-up, release and transport in flares where magnetic reconnection works as the central engine to produce a flare.

  12. Emergency flare tip repair

    SciTech Connect

    Harrison, G.A.

    1982-07-01

    Two damaged propane storage tank flares serving a large LPG storage facility near the Arabian Gulf were given emergency service. A diagram of over-all layout and spatial relationships between tanks and piping, and tables with general information relevant to selecting an acceptable radiant heat load factor and flare line flow characteristics were presented. The general equation for predicting radiant heat flux from a point source was used. The ignition of the temporary flare was discussed.

  13. Particle acceleration in flares

    NASA Technical Reports Server (NTRS)

    Benz, Arnold O.; Kosugi, Takeo; Aschwanden, Markus J.; Benka, Steve G.; Chupp, Edward L.; Enome, Shinzo; Garcia, Howard; Holman, Gordon D.; Kurt, Victoria G.; Sakao, Taro

    1994-01-01

    Particle acceleration is intrinsic to the primary energy release in the impulsive phase of solar flares, and we cannot understand flares without understanding acceleration. New observations in soft and hard X-rays, gamma-rays and coherent radio emissions are presented, suggesting flare fragmentation in time and space. X-ray and radio measurements exhibit at least five different time scales in flares. In addition, some new observations of delayed acceleration signatures are also presented. The theory of acceleration by parallel electric fields is used to model the spectral shape and evolution of hard X-rays. The possibility of the appearance of double layers is further investigated.

  14. Solar flares. [plasma physics

    NASA Technical Reports Server (NTRS)

    Rust, D. M.

    1979-01-01

    The present paper deals with explosions in a magnetized solar plasma, known as flares, whose effects are seen throughout the electromagnetic spectrum, from gamma-rays through the visible and to the radio band. The diverse phenomena associated with flares are discussed, along with the physical mechanisms that have been advanced to explain them. The impact of solar flare research on the development of plasma physics and magnetohydrodynamics is noted. The rapid development of solar flare research during the past 20 years, owing to the availability of high-resolution images, detailed magnetic field measurements, and improved spectral data, is illustrated.

  15. Flared tube attachment fitting

    NASA Technical Reports Server (NTRS)

    Alkire, I. D.; King, J. P., Jr.

    1980-01-01

    Tubes can be flared first, then attached to valves and other flow line components, with new fitting that can be disassembled and reused. Installed fitting can be disassembled so parts can be inspected. It can be salvaged and reused without damaging flared tube; tube can be coated, tempered, or otherwise treated after it has been flared, rather than before, as was previously required. Fitting consists of threaded male portion with conical seating surface, hexagonal nut with hole larger than other diameter of flared end of tube, and split ferrule.

  16. A solar tornado triggered by flares?

    NASA Astrophysics Data System (ADS)

    Panesar, N. K.; Innes, D. E.; Tiwari, S. K.; Low, B. C.

    2013-01-01

    Context. Solar tornados are dynamical, conspicuously helical magnetic structures that are mainly observed as a prominence activity. Aims: We investigate and propose a triggering mechanism for the solar tornado observed in a prominence cavity by SDO/AIA on September 25, 2011. Methods: High-cadence EUV images from the SDO/AIA and the Ahead spacecraft of STEREO/EUVI are used to correlate three flares in the neighbouring active-region (NOAA 11303) and their EUV waves with the dynamical developments of the tornado. The timings of the flares and EUV waves observed on-disk in 195 Å are analysed in relation to the tornado activities observed at the limb in 171 Å. Results: Each of the three flares and its related EUV wave occurred within ten hours of the onset of the tornado. They have an observed causal relationship with the commencement of activity in the prominence where the tornado develops. Tornado-like rotations along the side of the prominence start after the second flare. The prominence cavity expands with the accelerating tornado motion after the third flare. Conclusions: Flares in the neighbouring active region may have affected the cavity prominence system and triggered the solar tornado. A plausible mechanism is that the active-region coronal field contracted by the "Hudson effect" through the loss of magnetic energy as flares. Subsequently, the cavity expanded by its magnetic pressure to fill the surrounding low corona. We suggest that the tornado is the dynamical response of the helical prominence field to the cavity expansion. Movies are available in electronic form at http://www.aanda.org

  17. Flare differentially rotates sunspot on Sun's surface

    NASA Astrophysics Data System (ADS)

    Liu, Chang; Xu, Yan; Cao, Wenda; Deng, Na; Lee, Jeongwoo; Hudson, Hugh S.; Gary, Dale E.; Wang, Jiasheng; Jing, Ju; Wang, Haimin

    2016-10-01

    Sunspots are concentrations of magnetic field visible on the solar surface (photosphere). It was considered implausible that solar flares, as resulted from magnetic reconnection in the tenuous corona, would cause a direct perturbation of the dense photosphere involving bulk motion. Here we report the sudden flare-induced rotation of a sunspot using the unprecedented spatiotemporal resolution of the 1.6 m New Solar Telescope, supplemented by magnetic data from the Solar Dynamics Observatory. It is clearly observed that the rotation is non-uniform over the sunspot: as the flare ribbon sweeps across, its different portions accelerate (up to ~50° h-1) at different times corresponding to peaks of flare hard X-ray emission. The rotation may be driven by the surface Lorentz-force change due to the back reaction of coronal magnetic restructuring and is accompanied by a downward Poynting flux. These results have direct consequences for our understanding of energy and momentum transportation in the flare-related phenomena.

  18. Flare differentially rotates sunspot on Sun's surface

    PubMed Central

    Liu, Chang; Xu, Yan; Cao, Wenda; Deng, Na; Lee, Jeongwoo; Hudson, Hugh S.; Gary, Dale E.; Wang, Jiasheng; Jing, Ju; Wang, Haimin

    2016-01-01

    Sunspots are concentrations of magnetic field visible on the solar surface (photosphere). It was considered implausible that solar flares, as resulted from magnetic reconnection in the tenuous corona, would cause a direct perturbation of the dense photosphere involving bulk motion. Here we report the sudden flare-induced rotation of a sunspot using the unprecedented spatiotemporal resolution of the 1.6 m New Solar Telescope, supplemented by magnetic data from the Solar Dynamics Observatory. It is clearly observed that the rotation is non-uniform over the sunspot: as the flare ribbon sweeps across, its different portions accelerate (up to ∼50° h−1) at different times corresponding to peaks of flare hard X-ray emission. The rotation may be driven by the surface Lorentz-force change due to the back reaction of coronal magnetic restructuring and is accompanied by a downward Poynting flux. These results have direct consequences for our understanding of energy and momentum transportation in the flare-related phenomena. PMID:27721463

  19. Flares in childhood eczema.

    PubMed

    Langan, S M

    2009-01-01

    Eczema is a major public health problem affecting children worldwide. Few studies have directly assessed triggers for disease flares. This paper presents evidence from a published systematic review and a prospective cohort study looking at flare factors in eczema. This systematic review suggested that foodstuffs in selected groups, dust exposure, unfamiliar pets, seasonal variation, stress, and irritants may be important in eczema flares. We performed a prospective cohort study that focused on environmental factors and identified associations between exposure to nylon clothing, dust, unfamiliar pets, sweating, shampoo, and eczema flares. Results from this study also demonstrated some new key findings. First, the effect of shampoo was found to increase in cold weather, and second, combinations of environmental factors were associated with disease exacerbation, supporting a multiple component disease model. This information is likely to be useful to families and may lead to the ability to reduce disease flares in the future. PMID:20054505

  20. Predictions of reconnected flux, energy and helicity in eruptive solar flares

    NASA Astrophysics Data System (ADS)

    Kazachenko, Maria Dmitiyevna

    2010-12-01

    In order to better understand the solar genesis of interplanetary magnetic clouds, I model the magnetic and topological properties of several large eruptive solar flares and relate them to observations. My main hypothesis is that the flux ropes ejected during eruptive solar flares are the result of a sequence of magnetic reconnections. To test this hypothesis, I use the three-dimensional Minimum Current Corona model of flare energy storage (Longcope, 1996) together with pre-flare photospheric magnetic field and flare ribbon observations to predict the basic flare properties: reconnected magnetic flux, free energy, and flux rope helicity. Initially, the MCC model was able to quantify the properties of the flares that occur in active regions with only photospheric shearing motions. Since rotating motions may also play a key role in the flare energetics, I develop a method for including both shearing and rotating motions into the MCC model. I use this modified method to predict the model flare properties and then compare them to the observed quantities. Firstly, for two flares in active regions with fast rotating sunspots, I find that the relative importance of shearing and rotation to those flares depends critically on their location within the parent active region topology. Secondly, for four flares analyzed with the MCC model (three flares described here and one flare described in Longcope et al. (2007)), I find that the modeled flare properties agree with the observed properties within the uncertainties of the methods used. This agreement compels me to believe that the magnetic clouds associated with these four solar flares are formed by low-corona magnetic reconnection during the eruption as modeled by the MCC model, rather than eruption of pre-existing structures in the corona or formation in the upper corona with participation of the global magnetic field. I note that since all four flares occurred in active regions without significant pre-flare flux emergence

  1. COMPTEL solar flare observations

    NASA Technical Reports Server (NTRS)

    Ryan, J. M.; Aarts, H.; Bennett, K.; Debrunner, H.; Devries, C.; Denherder, J. W.; Eymann, G.; Forrest, D. J.; Diehl, R.; Hermsen, W.

    1992-01-01

    COMPTEL as part of a solar target of opportunity campaign observed the sun during the period of high solar activity from 7-15 Jun. 1991. Major flares were observed on 9 and 11 Jun. Although both flares were large GOES events (greater than or = X10), they were not extraordinary in terms of gamma-ray emission. Only the decay phase of the 15 Jun. flare was observed by COMPTEL. We report the preliminary analysis of data from these flares, including the first spectroscopic measurement of solar flare neutrons. The deuterium formation line at 2.223 MeV was present in both events and for at least the 9 Jun. event, was comparable to the flux in the nuclear line region of 4-8 MeV, consistent with Solar-Maximum Mission (SSM) Observations. A clear neutron signal was present in the flare of 9 Jun. with the spectrum extending up to 80 MeV and consistent in time with the emission of gamma-rays, confirming the utility of COMPTEL in measuring the solar neutron flux at low energies. The neutron flux below 100 MeV appears to be lower than that of the 3 Jun. 1982 flare by more than an order of magnitude. The neutron signal of the 11 Jun. event is under study. Severe dead time effects resulting from the intense thermal x-rays require significant corrections to the measured flux which increase the magnitude of the associated systematic uncertainties.

  2. The Flare Genesis Experiment

    NASA Technical Reports Server (NTRS)

    Rust, D. M.

    2002-01-01

    Using the Flare Genesis Experiment (FGE), a balloon-borne observatory with an 80-cm solar telescope we observed the active region NOAA 8844 on January 25, 2000 for several hours. FGE was equipped with a vector polarimeter and a tunable Fabry-Perot narrow-band filter. It recorded time series of filtergrams, vector magnetograms, and Dopplergrams at the Ca(I) 6122.2 angstrom line, and H-alpha filtergrams with a cadence between 2.5 and 7.5 minutes. At the time of the observations, NOAA 8844 was located at approximately 5 N 30 W. The region was rapidly growing during the observations; new magnetic flux was constantly emerging in three supergranules near its center. We describe in detail how the FGE data were analyzed and report on the structure and behavior of peculiar moving dipolar features (MDFs) observed in the active region. In longitudinal magnetograms, the MDFs appeared to be small dipoles in the emerging fields. The east-west orientation of their polarities was opposite that of the sunspots. The dipoles were oriented parallel to their direction of motion, which was in most cases towards the sunspots. Previously, dipolar moving magnetic features have only been observed flowing out from sunspots. Vector magnetograms show that the magnetic field of each MDF negative part was less inclined to the local horizontal than the ones of the positive part. We identify the MDFs as undulations, or stitches, where the emerging flux ropes are still tied to the photosphere. We present a U-loop model that can account for their unusual structure and behavior, and it shows how emerging flux can shed its entrained mass.

  3. Tube flare inspection tool

    NASA Technical Reports Server (NTRS)

    Meunier, G. E.

    1980-01-01

    Flare angle and symmetry of tube ends can be checked by simple tool that consists of two stainless steel pins bonded to rubber plug. Primary function of tool is to inspect tubes before they are installed, thereby eliminating expense and inconvenience of repairing leaks caused by imperfect flares. Measuring hole tapers, countersink angles, and bearing race angles are other possible uses. Tool is used with optical comparator. Axis of tool is alined with centerline of tube. Shadow of seated pins on comparator screen allows operator to verify flare angle is within tolerance.

  4. What Causes Lupus Flares?

    PubMed

    Fernandez, David; Kirou, Kyriakos A

    2016-03-01

    Systemic lupus erythematosus (SLE), the prototypic systemic autoimmune disease, follows a chronic disease course, punctuated by flares. Disease flares often occur without apparent cause, perhaps from progressive inherent buildup of autoimmunity. However, there is evidence that certain environmental factors may trigger the disease. These include exposure to UV light, infections, certain hormones, and drugs which may activate the innate and adaptive immune system, resulting in inflammation, cytotoxic effects, and clinical symptoms. Uncontrolled disease flares, as well as their treatment, especially with glucocorticoids, can cause significant organ damage. Tight surveillance and timely control of lupus flares with judicial use of effective treatments to adequately suppress the excessive immune system activation are required to bring about long term remission of the disease. We hope that new clinical trials will soon offer additional effective and target-specific biologic treatments for SLE.

  5. The solar flare myth

    NASA Technical Reports Server (NTRS)

    Gosling, J. T.

    1993-01-01

    Many years of research have demonstrated that large, nonrecurrent geomagnetic storms, shock wave disturbances in the solar wind, and energetic particle events in interplanetary space often occur in close association with large solar flares. This result has led to a pradigm of cause and effect - that large solar flares are the fundamental cause of these events in the near-Earth space environmemt. This paradigm, which I call 'the solar flare myth,' dominates the popular perception of the relationship between solar activity and interplanetary and geomagnetic events and has provided much of the pragmatic rationale for the study of the solar flare phenomenon. Yet there is good evidence that this paradigm is wrong and that flares do not generally play a central role in producing major transient disturbances in the near-Earth space environment. In this paper I outline a different paradigm of cause and effect that removes solar flares from their central position in the chain of events leading from the Sun to near-Earth space. Instead, this central role is given to events known as coronal mass ejections.

  6. Explosive evaporation in solar flares

    NASA Technical Reports Server (NTRS)

    Fisher, George H.

    1987-01-01

    This paper develops a simple analytical model for the phenomenon of 'explosive evaporation' driven by nonthermal electron heating in solar flares. The model relates the electron energy flux and spectrum, plus details of the preflare atmosphere, to the time scale for explosive evaporation to occur, the maximum pressure and temperature to be reached, rough estimates for the UV pulse emission flux and duration, and the evolution of the blueshifted component of the soft X-ray lines. An expression is given for the time scale for buildup to maximum pressures and the onset of rapid motion of the explosively evaporating plasma. This evaporation can excite a rapid response of UV line and continuum emission. The emission lines formed in the plasma approach a given emissivity-weighted blueshift speed.

  7. Slipping Magnetic Reconnections with Multiple Flare Ribbons during an X-class Solar Flare

    NASA Astrophysics Data System (ADS)

    Zheng, Ruisheng; Chen, Yao; Wang, Bing

    2016-06-01

    With the observations of the Solar Dynamics Observatory, we present the slipping magnetic reconnections with multiple flare ribbons (FRs) during an X1.2 eruptive flare on 2014 January 7. A center negative polarity was surrounded by several positive ones, and three FRs appeared. The three FRs showed apparent slipping motions, and hook structures formed at their ends. Due to the moving footpoints of the erupting structures, one tight semi-circular hook disappeared after the slippage along its inner and outer edges, and coronal dimmings formed within the hook. The east hook also faded as a result of the magnetic reconnection between the arcades of a remote filament and a hot loop that was impulsively heated by the under flare loops. Our results are accordant with the slipping magnetic reconnection regime in three-dimensional standard model for eruptive flares. We suggest that the complex structures of the flare are likely a consequence of the more complex flux distribution in the photosphere, and the eruption involves at least two magnetic reconnections.

  8. Highlights of the study of energy release in flares

    NASA Technical Reports Server (NTRS)

    Rust, D. M.; Batchelor, D. A.

    1987-01-01

    From February 26 to March 1, 1979, 32 solar flare investigators attended a workshop at Cambridge, MA to define objectives and devise a scientific program for the study of energy release in flares (SERF) during the coming solar maximum. Herein, some major results of the ensuing five-year effort to observe and understand the flare energy release process and its effects (energetic particle production, coronal and chromospheric heating, electromagnetic radiations, and mass motions and ejections) are reviewed. The central issue - what processes store and release the energy liberated in flares - remains unresolved except in the most general terms (e.g., it is generally agreed that the energy is stored in sheared or stressed magnetic fields and released by field annihilation during some MHD instability). Resolving that issue is still one of the most important goals in solar physics, but the advances during the SERF program have brought it closer.

  9. Flares and habitability

    NASA Astrophysics Data System (ADS)

    Abrevaya, Ximena C.; Cortón, Eduardo; Mauas, Pablo J. D.

    2012-07-01

    At present, dwarf M stars are being considered as potential hosts for habitable planets. However, an important fraction of these stars are flare stars, which among other kind of radiation, emit large amounts of UV radiation during flares, and it is unknown how this events can affect life, since biological systems are particularly vulnerable to UV. In this work we evaluate a well known dMe star, EV Lacertae (GJ 873) as a potential host for the emergence and evolution of life, focusing on the effects of the UV emission associated with flare activity. Since UV-C is particularly harmful for living organisms, we studied the effect of UV-C radiation on halophile archaea cultures. The halophile archaea or haloarchaea are extremophile microorganisms, which inhabit in hypersaline environments and which show several mechanisms to cope with UV radiation since they are naturally exposed to intense solar UV radiation on Earth. To select the irradiance to be tested, we considered a moderate flare on this star. We obtained the mean value for the UV-C irradiance integrating the IUE spectrum in the impulsive phase, and considering a hypothetical planet in the center of the liquid water habitability zone. To select the irradiation times we took the most frequent duration of flares on this star which is from 9 to 27 minutes. Our results show that even after considerable UV damage, the haloarchaeal cells survive at the tested doses, showing that this kind of life could survive in a relatively hostile UV environment.

  10. FLARING PATTERNS IN BLAZARS

    SciTech Connect

    Paggi, A.; Cavaliere, A.; Tavani, M.; Vittorini, V.; D'Ammando, F.

    2011-08-01

    Blazars radiate from relativistic jets launched by a supermassive black hole along our line of sight; the subclass of flat spectrum radio quasars exhibits broad emission lines, a telltale sign of a gas-rich environment and high accretion rate, contrary to the other subclass of the BL Lacertae objects. We show that this dichotomy of the sources in physical properties is enhanced in their flaring activity. The BL Lac flares yielded spectral evidence of being driven by further acceleration of highly relativistic electrons in the jet. Here, we discuss spectral fits of multi-{lambda} data concerning strong flares of the two flat spectrum radio quasars 3C 454.3 and 3C 279 recently detected in {gamma}-rays by the AGILE and Fermi satellites. We find that optimal spectral fits are provided by external Compton radiation enhanced by increasing production of thermal seed photons by growing accretion. We find such flares to trace patterns on the jet-power-electron-energy plane that diverge from those followed by flaring BL Lac objects and discuss why these occur.

  11. Flare Plasma Iron Abundance

    NASA Technical Reports Server (NTRS)

    Dennis, Brian R.; Dan, Chau; Jain, Rajmal; Schwartz, Richard A.; Tolbert, Anne K.

    2008-01-01

    The equivalent width of the iron-line complex at 6.7 keV seen in flare X-ray spectra suggests that the iron abundance of the hottest plasma at temperatures >approx.10 MK may sometimes be significantly lower than the nominal coronal abundance of four times the photospheric value that is commonly assumed. This conclusion is based on X-ray spectral observations of several flares seen in common with the Ramaty High Energy Solar Spectroscopic Imager (RHESSI) and the Solar X-ray Spectrometer (SOXS) on the second Indian geostationary satellite, GSAT-2. The implications of this will be discussed as it relates to the origin of the hot flare plasma - either plasma already in the corona that is directly heated during the flare energy release process or chromospheric plasma that is heated by flare-accelerated particles and driven up into the corona. Other possible explanations of lower-than-expected equivalent widths of the iron-line complex will also be discussed.

  12. A swirling flare-related EUV jet

    NASA Astrophysics Data System (ADS)

    Zhang, Q. M.; Ji, H. S.

    2014-01-01

    Aims: We report our observations of a swirling flare-related extreme-ultraviolet (EUV) jet on 2011 October 15 at the edge of NOAA active region 11314. Methods: We used the multiwavelength observations in the EUV passbands from the Atmospheric Imaging Assembly (AIA) aboard the Solar Dynamics Observatory (SDO). We extracted a wide slit along the jet axis and 12 thin slits across its axis to investigate the longitudinal motion and transverse rotation. We also used data from the Extreme-Ultraviolet Imager (EUVI) aboard the Solar TErrestrial RElations Observatory (STEREO) spacecraft to investigate the three-dimensional (3D) structure of the jet. Ground-based Hα images from the El Teide Observatory, a member of the Global Oscillation Network Group (GONG), provide a good opportunity to explore the relationship between the cool surge and the hot jet. Line-of-sight magnetograms from the Helioseismic and Magnetic Imager (HMI) aboard SDO enable us to study the magnetic evolution of the flare/jet event. We carried out potential-field extrapolation to calculate the magnetic configuration associated with the jet. Results: The onset of jet eruption coincided with the start time of the C1.6 flare impulsive phase. The initial velocity and acceleration of the longitudinal motion were 254 ± 10 km s-1 and -97 ± 5 m s-2, respectively. The jet presented helical structure and transverse swirling motion at the beginning of its eruption. The counter-clockwise rotation slowed down from an average velocity of ~122 km s-1 to ~80 km s-1. The interwinding thick threads of the jet untwisted into multiple thin threads during the rotation that lasted for one cycle with a period of ~7 min and an amplitude that increases from ~3.2 Mm at the bottom to ~11 Mm at the upper part. Afterwards, the curtain-like leading edge of the jet continued rising without rotation, leaving a dimming region behind, before falling back to the solar surface. The appearance/disappearance of dimming corresponded to the

  13. Fields, Flares, And Forecasts

    NASA Astrophysics Data System (ADS)

    Boucheron, L.; Al-Ghraibah, Amani; McAteer, J.; Cao, H.; Jackiewicz, J.; McNamara, B.; Voelz, D.; Calabro, B.; DeGrave, K.; Kirk, M.; Madadi, A.; Petsov, A.; Taylor, G.

    2011-05-01

    Solar active regions are the source of many energetic and geo-effective events such as solar flares and coronal mass ejections (CMEs). Understanding how these complex source regions evolve and produce these events is of fundamental importance, not only to solar physics, but also to the demands of space weather forecasting. We propose to investigate the physical properties of active region magnetic fields using fractal-, gradient-, neutral line-, emerging flux-, wavelet- and general image-based techniques, and to correlate them to solar activity. The combination of these projects with solarmonitor.org and the international Max Millenium Campaign presents an opportunity for accurate and timely flare predictions for the first time. Many studies have attempted to relate solar flares to their concomitant magnetic field distributions. However, a consistent, causal relationship between the magnetic field on the photosphere and the production of solar flares is unknown. Often the local properties of the active region magnetic field - critical in many theories of activity - are lost in the global definition of their diagnostics, in effect smoothing out variations that occur on small spatial scales. Mindful of this, our overall goal is to create measures that are sensitive to both the global and the small-scale nature of energy storage and release in the solar atmosphere in order to study solar flare prediction. This set of active region characteristics will be automatically explored for discriminating features through the use of feature selection methods. Such methods search a feature space while optimizing a criterion - the prediction of a flare in this case. The large size of the datasets used in this project make it well suited for an exploration of a large feature space. This work is funded through a New Mexico State University Interdisciplinary Research Grant.

  14. Solar flare model atmospheres

    NASA Technical Reports Server (NTRS)

    Hawley, Suzanne L.; Fisher, George H.

    1993-01-01

    Solar flare model atmospheres computed under the assumption of energetic equilibrium in the chromosphere are presented. The models use a static, one-dimensional plane parallel geometry and are designed within a physically self-consistent coronal loop. Assumed flare heating mechanisms include collisions from a flux of non-thermal electrons and x-ray heating of the chromosphere by the corona. The heating by energetic electrons accounts explicitly for variations of the ionized fraction with depth in the atmosphere. X-ray heating of the chromosphere by the corona incorporates a flare loop geometry by approximating distant portions of the loop with a series of point sources, while treating the loop leg closest to the chromospheric footpoint in the plane-parallel approximation. Coronal flare heating leads to increased heat conduction, chromospheric evaporation and subsequent changes in coronal pressure; these effects are included self-consistently in the models. Cooling in the chromosphere is computed in detail for the important optically thick HI, CaII and MgII transitions using the non-LTE prescription in the program MULTI. Hydrogen ionization rates from x-ray photo-ionization and collisional ionization by non-thermal electrons are included explicitly in the rate equations. The models are computed in the 'impulsive' and 'equilibrium' limits, and in a set of intermediate 'evolving' states. The impulsive atmospheres have the density distribution frozen in pre-flare configuration, while the equilibrium models assume the entire atmosphere is in hydrostatic and energetic equilibrium. The evolving atmospheres represent intermediate stages where hydrostatic equilibrium has been established in the chromosphere and corona, but the corona is not yet in energetic equilibrium with the flare heating source. Thus, for example, chromospheric evaporation is still in the process of occurring.

  15. Valentines Day X2 Flare

    NASA Video Gallery

    Active region 1158 let loose with an X2.2 flare at 0153 UT or 8:50 pm ET on February 15, 2011, the largest flare since Dec. 2006 and the biggest flare so far in Solar Cycle 24. This video was taken...

  16. BATSE Solar Flare Spectroscopy

    NASA Technical Reports Server (NTRS)

    Schwartz, R. A.

    1998-01-01

    This final report describes the progress originally proposed: (1) the continued improvement of a software and database environment capable of supporting all users of BATSE solar data as well as providing scientific expertise and effort to the BATSE solar community; (2) the continued participation with the PI team and other guest investigators in the detailed analysis of the BATSE detectors' response at low energies; (3) using spectroscopic techniques to fully exploit the potential of electron time-of-flight studies; and, (4) a full search for flare gamma-ray line emission at 2.2 MeV from all GOES X-class flares observed with BATSE.

  17. GAMMA-RAY BURST FLARES: ULTRAVIOLET/OPTICAL FLARING. I

    SciTech Connect

    Swenson, C. A.; Roming, P. W. A.; De Pasquale, M.; Oates, S. R.

    2013-09-01

    We present a previously unused method for the detection of flares in gamma-ray burst (GRB) light curves and use this method to detect flares in the ultraviolet/optical. The algorithm makes use of the Bayesian Information Criterion to analyze the residuals of the fitted light curve, removing all major features, and to determine the statistically best fit to the data by iteratively adding additional ''breaks'' to the light curve. These additional breaks represent the individual components of the detected flares: T{sub start}, T{sub stop}, and T{sub peak}. We present the detection of 119 unique flaring periods detected by applying this algorithm to light curves taken from the Second Swift Ultraviolet/Optical Telescope (UVOT) GRB Afterglow Catalog. We analyzed 201 UVOT GRB light curves and found episodes of flaring in 68 of the light curves. For those light curves with flares, we find an average number of {approx}2 flares per GRB. Flaring is generally restricted to the first 1000 s of the afterglow, but can be observed and detected beyond 10{sup 5} s. More than 80% of the flares detected are short in duration with {Delta}t/t of <0.5. Flares were observed with flux ratios relative to the underlying light curve of between 0.04 and 55.42. Many of the strongest flares were also seen at greater than 1000 s after the burst.

  18. Electron beams in solar flares

    NASA Technical Reports Server (NTRS)

    Aschwanden, Markus J.; Dennis, Brian R.; Benz, Arnold O.

    1994-01-01

    A list of publications resulting from this program includes 'The Timing of Electron Beam Signatures in Hard X-Ray and Radio: Solar Flare Observations by BATSE/Compton Gamma-Ray Observatory and PHOENIX'; 'Coherent-Phase or Random-Phase Acceleration of Electron Beams in Solar Flares'; 'Particle Acceleration in Flares'; 'Chromospheric Evaporation and Decimetric Radio Emission in Solar Flares'; 'Sequences of Correlated Hard X-Ray and Type 3 Bursts During Solar Flares'; and 'Solar Electron Beams Detected in Hard X-Rays and Radiowaves.' Abstracts and reprints of each are attached to this report.

  19. Solar flares: an overview.

    PubMed

    Rust, D M

    1992-01-01

    This is a survey of solar phenomena and physical models that may be useful for improving forecasts of solar flares and proton storms in interplanetary space. Knowledge of the physical processes that accelerate protons has advanced because of gamma-ray and X-ray observations from the Solar Maximum Mission telescopes. Protons are accelerated at the onset of flares, but the duration of any subsequent proton storm at 1 AU depends on the structure of the interplanetary fields. X-ray images of the solar corona show possible fast proton escape paths. Magnetographs and high-resolution visible-band images show the magnetic field structure near the acceleration region and the heating effects of sunward-directed protons. Preflare magnetic field growth and shear may be the most important clues to the physical processes that generate high energy solar particles. Any dramatic improvement in flare forecasts will require high resolution solar telescopes in space. Several possibilities for improvements in the art of flare forecasting are presented, among them: the use of acoustic tomography to probe for subsurface magnetic fields; a satellite-borne solar magnetograph; and an X-ray telescope to monitor the corona for eruptions.

  20. Numerical modeling of the energy storage and release in solar flares

    NASA Technical Reports Server (NTRS)

    Wu, S. T.; Weng, F. S.

    1993-01-01

    This paper reports on investigation of the photospheric magnetic field-line footpoint motion (usually referred to as shear motion) and magnetic flux emerging from below the surface in relation to energy storage in a solar flare. These causality relationships are demonstrated by using numerical magnetohydrodynamic simulations. From these results, one may conclude that the energy stored in solar flares is in the form of currents. The dynamic process through which these currents reach a critical value is discussed as well as how these currents lead to energy release, such as the explosive events of solar flares.

  1. Gamma-ray burst flares: X-ray flaring. II

    SciTech Connect

    Swenson, C. A.; Roming, P. W. A.

    2014-06-10

    We present a catalog of 498 flaring periods found in gamma-ray burst (GRB) light curves taken from the online Swift X-Ray Telescope GRB Catalogue. We analyzed 680 individual light curves using a flare detection method developed and used on our UV/optical GRB Flare Catalog. This method makes use of the Bayesian Information Criterion to analyze the residuals of fitted GRB light curves and statistically determines the optimal fit to the light curve residuals in an attempt to identify any additional features. These features, which we classify as flares, are identified by iteratively adding additional 'breaks' to the light curve. We find evidence of flaring in 326 of the analyzed light curves. For those light curves with flares, we find an average number of ∼1.5 flares per GRB. As with the UV/optical, flaring in our sample is generally confined to the first 1000 s of the afterglow, but can be detected to beyond 10{sup 5} s. Only ∼50% of the detected flares follow the 'classical' definition of Δt/t ≤ 0.5, with many of the largest flares exceeding this value.

  2. Evolution and flare activity of a group in July 1978

    SciTech Connect

    Sattarov, I.

    1983-03-01

    The evolution of a sunspot group with a delta configuration which passed over the solar disk on July 8--21, 1978, is studied on the basis of original materials consisting of photoheliograms, H..cap alpha.. filtergrams, and wide-band photographs obtained in Tashkent. More than 160 H..cap alpha.. flares, including 22 flares of importance 1 and 10 flares of importance 2, were observed in the active region (AR) containing this group according to Solar-Geophysical Data. As a result of a comparison of the evolutionary changes of the group with the flare activity of the AR it was found that the flare activity is connected with the formation of a new sunspot group within an old one, with its maximum falling at the time of formation of the first nuclei, and new nuclei are formed along the zero line of the longitudinal field of the old group; the nodes of the majority of flares are located near new nuclei, symmetrical relative to the zero line; the area of the new nuclei increases impulsively; the total area of the entire group varies, fluctuating about its average value, and flares happen during the slowing and cessation of the increase in area; some nuclei show proper motion at a velocity of approx.0.5 km/sec while others show intermittent motion, like pulsation, directed outside the old group; as a result of the development of new nuclei near old ones the small nuclei break up, while the boundary of the large nucleus is deformed on the side of the new nuclei and bright points shine within it.

  3. Well-observed dynamics of flaring and peripheral coronal magnetic loops during an M-class limb flare

    SciTech Connect

    Shen, Jinhua; Zhou, Tuanhui; Ji, Haisheng; Feng, Li; Wiegelmann, Thomas; Inhester, Bernd

    2014-08-20

    In this paper, we present a variety of well-observed dynamic behaviors for the flaring and peripheral magnetic loops of the M6.6 class extreme limb flare that occurred on 2011 February 24 (SOL2011-02-24T07:20) from EUV observations by the Atmospheric Imaging Assembly on the Solar Dynamics Observatory and X-ray observations by RHESSI. The flaring loop motion confirms the earlier contraction-expansion picture. We find that the U-shaped trajectory delineated by the X-ray corona source of the flare roughly follows the direction of a filament eruption associated with the flare. Different temperature structures of the coronal source during the contraction and expansion phases strongly suggest different kinds of magnetic reconnection processes. For some peripheral loops, we discover that their dynamics are closely correlated with the filament eruption. During the slow rising to abrupt, fast rising of the filament, overlying peripheral magnetic loops display different responses. Two magnetic loops on the elbow of the active region had a slow descending motion followed by an abrupt successive fast contraction, while magnetic loops on the top of the filament were pushed outward, slowly being inflated for a while and then erupting as a moving front. We show that the filament activation and eruption play a dominant role in determining the dynamics of the overlying peripheral coronal magnetic loops.

  4. Flares as Avalanches?

    NASA Astrophysics Data System (ADS)

    Charbonneau, P.

    2003-05-01

    In 1991, E.T. Lu and R. Hamilton (ApJ 380, L89) suggested that flares could be interpreted as avalanches of reconnection events in coronal magnetic structures driven to a self-organized critical state. Physical underpinning for the simple cellular automaton model they used to illustrate their idea can be readily found in the nanoflare conjecture for coronal heating championed over the past two decades by E.N. Parker (e.g., ApJ 330, 474 [1988]). In this lecture I will give a brief overview of Lu & Hamilton's avalanche model, and describe how it can be physically interpreted in the context of Parker's nanoflare conjecture. After discussing some illustrative model results, I will focus on recent comparisons of the model's predictions with flare observations. Finally, I will discuss some recent attempts at quantitatively exploring the physical relationship between model components and the physics of magnetic reconnection.

  5. Solar Flare Physics

    NASA Technical Reports Server (NTRS)

    Schmahl, Edward J.; Kundu, Mukul R.

    2000-01-01

    During the past year we have been working with the HESSI (High Energy Solar Spectroscopic Imager) team in preparation for launch in early 2001. HESSI has as its primary scientific goal photometric imaging and spectroscopy of solar flares in hard X-rays and gamma-rays with an approx. 2 sec angular resolution, approx. keV energy resolution and approx. 2 s time resolution over the 6 keV to 15 MeV energy range. We have performed tests of the imager using a specially designed experiment which exploits the second-harmonic response of HESSI's sub-collimators to an artificial X-ray source at a distance of 1550 cm from its front grids. Figures show the response to X-rays at energies in the range where HESSI is expected to image solar flares. To prepare the team and the solar user community for imaging flares with HESSI, we have written a description of the major imaging concepts. This paper will be submitted for publication in a referred journal.

  6. PRECURSOR FLARES IN OJ 287

    SciTech Connect

    Pihajoki, P.; Berdyugin, A.; Lindfors, E.; Reinthal, R.; Sillanpaeae, A.; Takalo, L.; Valtonen, M.; Nilsson, K.; Zola, S.; Koziel-Wierzbowska, D.; Liakos, A.; Drozdz, M.; Winiarski, M.; Ogloza, W.; Provencal, J.; Santangelo, M. M. M.; Salo, H.; Chandra, S.; Ganesh, S.; Baliyan, K. S.; and others

    2013-02-10

    We have studied three most recent precursor flares in the light curve of the blazar OJ 287 while invoking the presence of a precessing binary black hole in the system to explain the nature of these flares. Precursor flare timings from the historical light curves are compared with theoretical predictions from our model that incorporate effects of an accretion disk and post-Newtonian description for the binary black hole orbit. We find that the precursor flares coincide with the secondary black hole descending toward the accretion disk of the primary black hole from the observed side, with a mean z-component of approximately z{sub c} = 4000 AU. We use this model of precursor flares to predict that precursor flare of similar nature should happen around 2020.96 before the next major outburst in 2022.

  7. Energy release in solar flares

    NASA Technical Reports Server (NTRS)

    Brown, John C.; Correia, Emilia; Farnik, Frantisek; Garcia, Howard; Henoux, Jean-Claude; La Rosa, Ted N.; Machado, Marcos E. (Compiler); Nakajima, Hiroshi; Priest, Eric R.

    1994-01-01

    Team 2 of the Ottawa Flares 22 Workshop dealt with observational and theoretical aspects of the characteristics and processes of energy release in flares. Main results summarized in this article stress the global character of the flaring phenomenon in active regions, the importance of discontinuities in magnetic connectivity, the role of field-aligned currents in free energy storage, and the fragmentation of energy release in time and space.

  8. Confined Flares in Solar Active Region 12192 from 2014 October 18 to 29

    NASA Astrophysics Data System (ADS)

    Chen, Huadong; Zhang, Jun; Ma, Suli; Yang, Shuhong; Li, Leping; Huang, Xin; Xiao, Junmin

    2015-07-01

    Using the observations from the Atmospheric Imaging Assembly and Helioseismic and Magnetic Imager (HMI) on board the Solar Dynamics Observatory, we investigate 6 X-class and 29 M-class flares occurring in solar active region (AR) 12192 from October 18 to 29. Among them, 30 (including 6 X- and 24 M-class) flares originated from the AR core, and the other 5 M-flares appeared at the AR periphery. Four of the X-flares exhibited similar flaring structures, indicating they were homologous flares with an analogous triggering mechanism. The possible scenario is that photospheric motions of emerged magnetic fluxes lead to shearing of the associated coronal magnetic field, which then yields a tether-cutting favorable configuration. Among the five periphery M-flares, four were associated with jet activities. The HMI vertical magnetic field data show that the photospheric fluxes of opposite magnetic polarities emerged, converged, and canceled with each other at the footpoints of the jets before the flares. Only one M-flare from the AR periphery was followed by a coronal mass ejection (CME). From October 20 to 26, the mean decay index of the horizontal background field within the height range of 40-105 Mm is below the typical threshold for torus instability onset. This suggests that a strong confinement from the overlying magnetic field might be responsible for the poor CME production of AR 12192.

  9. CONFINED FLARES IN SOLAR ACTIVE REGION 12192 FROM 2014 OCTOBER 18 TO 29

    SciTech Connect

    Chen, Huadong; Zhang, Jun; Yang, Shuhong; Li, Leping; Huang, Xin; Xiao, Junmin; Ma, Suli

    2015-07-20

    Using the observations from the Atmospheric Imaging Assembly and Helioseismic and Magnetic Imager (HMI) on board the Solar Dynamics Observatory, we investigate 6 X-class and 29 M-class flares occurring in solar active region (AR) 12192 from October 18 to 29. Among them, 30 (including 6 X- and 24 M-class) flares originated from the AR core, and the other 5 M-flares appeared at the AR periphery. Four of the X-flares exhibited similar flaring structures, indicating they were homologous flares with an analogous triggering mechanism. The possible scenario is that photospheric motions of emerged magnetic fluxes lead to shearing of the associated coronal magnetic field, which then yields a tether-cutting favorable configuration. Among the five periphery M-flares, four were associated with jet activities. The HMI vertical magnetic field data show that the photospheric fluxes of opposite magnetic polarities emerged, converged, and canceled with each other at the footpoints of the jets before the flares. Only one M-flare from the AR periphery was followed by a coronal mass ejection (CME). From October 20 to 26, the mean decay index of the horizontal background field within the height range of 40–105 Mm is below the typical threshold for torus instability onset. This suggests that a strong confinement from the overlying magnetic field might be responsible for the poor CME production of AR 12192.

  10. Optical flares in SS433

    NASA Astrophysics Data System (ADS)

    Irsmambetova, T. R.

    2014-03-01

    An analysis of the precessional and orbital variability separately in active and quiescent states was carried out by using the photometric database in V-band of the SAI. The main orbital light curves in the active and quiet states in different precessional phases are approximately the same - primary and secondary eclipses are also observed. There are 30 most bright flares that have been studied on phase diagrams. The phase diagrams show the dependence of the flares' appearance on combination between the nodding phases and the precession phases. An analysis of the above results suggests that the flares originate in jets. Perhaps variations in jet speed cause flares activity in SS433.

  11. A model solar flares and their homologous behavior

    SciTech Connect

    Choe, G.S.; Cheng, C.Z.

    2000-01-27

    A model describing physical processes of solar flares and their homologous behavior is presented based on resistive MHD simulations of magnetic arcade evolution subject to continuous shear-increasing footpoint motions. It is proposed in the model that the individual flaring process encompasses magnetic reconnection of arcade field lines, generation of magnetic islands in the magnetic arcade, and coalescence of magnetic islands. When a magnetic arcade is sheared, a current sheet is formed and magnetic reconnection can take place to form a magnetic island. A continuing increase of magnetic shear can trigger a new reconnection process and create another island in the underlying arcade below the magnetic island. The newborn island rises faster than the preceding island and merges with it to form one island. Before merging with the upper island is completed, the newborn island exhibits two different phases of rising motion: the first phase with a slower rising speed and the second phase wit h a faster rising speed. This is consistent with the Yohkoh observation by Ohyama and Shibata (1998) of X-ray plasma ejecta motion. The first phase, in which reconnection of line-tied field in the underlying arcade is important, can be regarded to be related with the preflare phase. In the second phase, the island coalescence takes place, which creates an elongated current sheet below and enhances the reconnection rate of the line-tied arcade field. This phase is interpreted as the impulsive phase or the flash phase of flares. The obtained reconnection electric field is large enough to accelerate electrons to an energy level higher than 10 keV, which is necessary for observed X-ray emissions. After merging of the islands is completed, magnetic reconnection continues in the current sheet under the integrated island for rather a long period, which can be considered as the main phase of flares. The sequence of all these processes is repeated with some time interval while a shear

  12. Slipping magnetic reconnection during an X-class solar flare observed by SDO/AIA

    SciTech Connect

    Dudík, J.; Del Zanna, G.; Mason, H. E.; Janvier, M.; Aulanier, G.; Schmieder, B.; Karlický, M. E-mail: mjanvier@maths.dundee.ac.uk

    2014-04-01

    We present SDO/AIA observations of an eruptive X-class flare of 2012 July 12, and compare its evolution with the predictions of a three-dimensional (3D) numerical simulation. We focus on the dynamics of flare loops that are seen to undergo slipping reconnection during the flare. In the Atmospheric Imaging Assembly (AIA) 131 Å observations, lower parts of 10 MK flare loops exhibit an apparent motion with velocities of several tens of km s{sup –1} along the developing flare ribbons. In the early stages of the flare, flare ribbons consist of compact, localized bright transition-region emission from the footpoints of the flare loops. A differential emission measure analysis shows that the flare loops have temperatures up to the formation of Fe XXIV. A series of very long, S-shaped loops erupt, leading to a coronal mass ejection observed by STEREO. The observed dynamics are compared with the evolution of magnetic structures in the 'standard solar flare model in 3D.' This model matches the observations well, reproducing the apparently slipping flare loops, S-shaped erupting loops, and the evolution of flare ribbons. All of these processes are explained via 3D reconnection mechanisms resulting from the expansion of a torus-unstable flux rope. The AIA observations and the numerical model are complemented by radio observations showing a noise storm in the metric range. Dm-drifting pulsation structures occurring during the eruption indicate plasmoid ejection and enhancement of the reconnection rate. The bursty nature of radio emission shows that the slipping reconnection is still intermittent, although it is observed to persist for more than an hour.

  13. DRAFTS: A DEEP, RAPID ARCHIVAL FLARE TRANSIENT SEARCH IN THE GALACTIC BULGE

    SciTech Connect

    Osten, Rachel A.; Sahu, Kailash; Kowalski, Adam; Hawley, Suzanne L.

    2012-07-20

    We utilize the Sagittarius Window Eclipsing Extrasolar Planet Search Hubble Space Telescope/Advanced Camera for Surveys data set for a Deep Rapid Archival Flare Transient Search to constrain the flare rate toward the older stellar population in the Galactic bulge. During seven days of monitoring 229,293 stars brighter than V = 29.5, we find evidence for flaring activity in 105 stars between V = 20 and V = 28. We divided the sample into non-variable stars and variable stars whose light curves contain large-scale variability. The flare rate on variable stars is {approx}700 times that of non-variable stars, with a significant correlation between the amount of underlying stellar variability and peak flare amplitude. The flare energy loss rates are generally higher than those of nearby well-studied single dMe flare stars. The distribution of proper motions is consistent with the flaring stars being at the distance and age of the Galactic bulge. If they are single dwarfs, then they span a range of Almost-Equal-To 1.0-0.25 M{sub Sun }. A majority of the flaring stars exhibit periodic photometric modulations with P < 3 days. If these are tidally locked magnetically active binary systems, then their fraction in the bulge is enhanced by a factor of {approx}20 compared to the local value. These stars may be useful for placing constraints on the angular momentum evolution of cool close binary stars. Our results expand the type of stars studied for flares in the optical band, and suggest that future sensitive optical time-domain studies will have to contend with a larger sample of flaring stars than the M dwarf flare stars usually considered.

  14. Spatio-temporal Dynamics of Sources of Hard X-Ray Pulsations in Solar Flares

    NASA Astrophysics Data System (ADS)

    Kuznetsov, S. A.; Zimovets, I. V.; Morgachev, A. S.; Struminsky, A. B.

    2016-09-01

    flares we studied are eruptive events. This gives a strong indication that eruptive processes play an important role in the generation of HXR pulsations in flares. We suggest that an erupting flux rope can act as a trigger of the flare energy release. Its successive interaction with different loops of a parent active region can lead to apparent motion of HXR sources and to a series of HXR pulsations. However, the exact mechanism responsible for generating the pulsations remains unclear and requires a more detailed investigation.

  15. The flares of August 1972. [solar flare characteristics and spectra

    NASA Technical Reports Server (NTRS)

    Zirin, H.; Tanaka, K.

    1973-01-01

    Observations of the August, 1972 flares at Big Bear and Tel Aviv, involving monochromatic movies, magnetograms, and spectra, are analyzed. The region (McMath 11976) showed inverted polarity from its inception on July 11; the great activity was due to extremely high shear and gradients in the magnetic field, as well as a constant invasion of one polarity into the opposite; observations in lambda 3835 show remarkable fast flashes in the impulsive flare of 18:38 UT on Aug. 2 with lifetimes of 5 sec, which may be due to dumping of particles in the lower chromosphere. Flare loops show evolutionary increases of their tilts to the neutral line in the flares of Aug. 4 and 7. Spectroscopic observations show red asymmetry and red shift of the H alpha emission in the flash phase of the Aug. 7 flare, as well as substantial velocity shear in the photosphere during the flare, somewhat like earthquake movement along a fault. Finally the total H alpha emission of the Aug. 7 flare could be measured accurately as about 2.5 x 10 to the 30th power erg, considerably less than coarser previous estimates for great flares.

  16. Observational evidence for thermal wave fronts in solar flares

    NASA Technical Reports Server (NTRS)

    Rust, D. M.; Simnett, G. M.; Smith, D. F.

    1985-01-01

    Images in 3.5-30 keV X-rays obtained during the first few minutes of seven solar flares show rapid motions. In each case X-ray emission first appeared at one end of a magnetic field structure, and then propagated along the field at a velocity between 800 and 1700 km/s. The observed X-ray structures were 45,000-230,000 km long. Simultaneous H-alpha images were available in three cases; they showed brightenings when the fast-moving fronts arrived at the chromosphere. The fast-moving fronts are interpreted as electron thermal conduction fronts since their velocities are consistent with conduction at the observed temperatures of 1-3 x 10 to the 7th K. The inferred conductive heat flux of up to 10-billion ergs/s sq cm accounts for most of the energy released in the flares, implying that the flares were primarily thermal phenomena.

  17. Modelling the influence of photospheric turbulence on solar flare statistics.

    PubMed

    Mendoza, M; Kaydul, A; de Arcangelis, L; Andrade, J S; Herrmann, H J

    2014-09-23

    Solar flares stem from the reconnection of twisted magnetic field lines in the solar photosphere. The energy and waiting time distributions of these events follow complex patterns that have been carefully considered in the past and that bear some resemblance with earthquakes and stockmarkets. Here we explore in detail the tangling motion of interacting flux tubes anchored in the plasma and the energy ejections resulting when they recombine. The mechanism for energy accumulation and release in the flow is reminiscent of self-organized criticality. From this model, we suggest the origin for two important and widely studied properties of solar flare statistics, including the time-energy correlations. We first propose that the scale-free energy distribution of solar flares is largely due to the twist exerted by the vorticity of the turbulent photosphere. Second, the long-range temporal and time-energy correlations appear to arise from the tube-tube interactions. The agreement with satellite measurements is encouraging.

  18. Solar flare discovery

    NASA Technical Reports Server (NTRS)

    Hudson, Hugh S.

    1987-01-01

    This paper considers the discoveries that have appreciably changed our understanding of the physics of solar flares. A total of 42 discoveries from all disciplines, ranging from Galileo's initial observation of faculae to the recent discovery of strong limb brightening in 10-MeV gamma-radiation, are identified. The rate of discovery increased dramatically over the past four decades as new observational tools became available. The assessment of significance suggests that recent discoveries -though more numerous - are individually less significant; perhaps this is because the minor early discoveries tend to be taken for granted.

  19. Flares produced by tides due to a black hole

    NASA Astrophysics Data System (ADS)

    Cadez, Andrej; Cadez, Andrej; Kostic, Uros; Calvani, Massimo; Gomboc, Andreja

    Time scales of flares from the center of our Galaxy strongly suggest motion only a few Schwarzschild radii away from the black hole. If flares are uncorrelated single events of accretion onto the black hole, the strongest candidate for their energy source is the tidal part of the gravitational potential energy. We show that this energy source may yield up to a few percent of mc2 , but it can be effectively and rapidly tapped only if the accretion event occurs from a sufficientlly eccentric orbit. This line of reasonig suggests that Galactic center flares might be produced by the final accretion of single dense objects with the mass of the order of 1020 g. We show that in this case the light curve of a flare can be deduced from dynamical properties of geodesic orbits around black holes and it only weakly depends on physical properties of the source. We discuss scenarios and limitations to such processes that can describe observed flares from the Galactic center.

  20. Parameterization of solar flare dose

    SciTech Connect

    Lamarche, A.H.; Poston, J.W.

    1996-12-31

    A critical aspect of missions to the moon or Mars will be the safety and health of the crew. Radiation in space is a hazard for astronauts, especially high-energy radiation following certain types of solar flares. A solar flare event can be very dangerous if astronauts are not adequately shielded because flares can deliver a very high dose in a short period of time. The goal of this research was to parameterize solar flare dose as a function of time to see if it was possible to predict solar flare occurrence, thus providing a warning time. This would allow astronauts to take corrective action and avoid receiving a dose greater than the recommended limit set by the National Council on Radiation Protection and Measurements (NCRP).

  1. Fine Structure in Solar Flares.

    PubMed

    Warren

    2000-06-20

    We present observations of several large two-ribbon flares observed with both the Transition Region and Coronal Explorer (TRACE) and the soft X-ray telescope on Yohkoh. The high spatial resolution TRACE observations show that solar flare plasma is generally not confined to a single loop or even a few isolated loops but to a multitude of fine coronal structures. These observations also suggest that the high-temperature flare plasma generally appears diffuse while the cooler ( less, similar2 MK) postflare plasma is looplike. We conjecture that the diffuse appearance of the high-temperature flare emission seen with TRACE is due to a combination of the emission measure structure of these flares and the instrumental temperature response and does not reflect fundamental differences in plasma morphology at the different temperatures.

  2. Solar Flares and the Chromosphere

    NASA Astrophysics Data System (ADS)

    Fletcher, Lyndsay

    2015-08-01

    During a solar flare, the chromosphere emits across a large fraction of the electromagnetic spectrum, providing diagnostic information on heating, dynamics and flare energy transport by both thermal and non-thermal means. The evolution of chromospheric ribbons and footpoints also traces the progress of coronal reconnection, and links radiation output with magnetic evolution. Since the chromosphere emits the majority of a flare's radiation, the current emphasis on chromospheric observations by missions such as IRIS, and future large facilities such as the DKIST, is very beneficial to flare research. In this talk I will overview recent developments in observations and theory of flaring chromospheres and make some suggestions about profitable future avenues for research.

  3. Gage tests tube flares quickly and accurately

    NASA Technical Reports Server (NTRS)

    Griffin, F. D.

    1966-01-01

    Flared tube gage with a test cone that is precisely made with a tapering surface to complement the tube flare is capable of determining the accuracy of a tube flare efficiently and economically. This device should improve the speed, efficiency, and accuracy of tube flare inspections.

  4. Horizontal flows concurrent with an X2.2 flare in the active region NOAA 11158

    NASA Astrophysics Data System (ADS)

    Beauregard, L.; Verma, M.; Denker, C.

    2012-02-01

    Horizontal proper motions were measured with local correlation tracking (LCT) techniques in active region NOAA 11158 on 2011 February 15 at a time when a major (X2.2) solar flare occurred. The measurements are based on continuum images and magnetograms of the Helioseismic and Magnetic Imager on board the Solar Dynamics Observatory. The observed shear flows along the polarity inversion line were rather weak (a few 100 m s-1). The counter-streaming region shifted toward the north after the flare. A small circular area with flow speeds of up to 1.2 km s-1 appeared after the flare near a region of rapid penumbral decay. The LCT signal in this region was provided by small-scale photospheric brigthenings, which were associated with fast traveling moving magnetic features. Umbral strengthening and rapid penumbral decay was observed after the flare. Both phenomena were closely tied to kernels of white-light flare emission. The white-light flare only lasted for about 15 min and peaked 4 min earlier than the X-ray flux. In comparison to other major flares, the X2.2 flare in active region NOAA 11158 only produced diminutive photospheric signatures.

  5. MAGNETIC RECONNECTION DURING THE TWO-PHASE EVOLUTION OF A SOLAR ERUPTIVE FLARE

    SciTech Connect

    Joshi, Bhuwan; Cho, K.-S.; Bong, S.-C.; Kim, Y.-H.; Veronig, Astrid; Moon, Y.-J.; Lee, Jeongwoo; Manoharan, P. K.

    2009-12-01

    We present a detailed multi-wavelength analysis and interpretation of the evolution of an M7.6 flare that occurred near the southeast limb on 2003 October 24. Pre-flare images at TRACE 195 A show that the bright and complex system of coronal loops already existed at the flaring site. The X-ray observations of the flare taken from the Reuven Ramaty High Energy Solar Spectroscopic Imager (RHESSI) spacecraft reveal two phases of the flare evolution. The first phase is characterized by the altitude decrease of the X-ray looptop (LT) source for approx11 minutes. Such a long duration of the descending LT source motion is reported for the first time. The EUV loops, located below the X-ray LT source, also undergo contraction with similar speed (approx15 km s{sup -1}) in this interval. During the second phase the two distinct hard X-ray footpoint (FP) sources are observed which correlate well with UV and Halpha flare ribbons. The X-ray LT source now exhibits upward motion as anticipated from the standard flare model. The RHESSI spectra during the first phase are soft and indicative of hot thermal emission from flaring loops with temperatures T > 25 MK at the early stage. On the other hand, the spectra at high energies (epsilon approx> 25 keV) follow hard power laws during the second phase (gamma = 2.6-2.8). We show that the observed motion of the LT and FP sources can be understood as a consequence of three-dimensional magnetic reconnection at a separator in the corona. During the first phase of the flare, the reconnection releases an excess of magnetic energy related to the magnetic tensions generated before a flare by the shear flows in the photosphere. The relaxation of the associated magnetic shear in the corona by the reconnection process explains the descending motion of the LT source. During the second phase, the ordinary reconnection process dominates describing the energy release in terms of the standard model of large eruptive flares with increasing FP separation

  6. Solar flare predictions and warnings

    NASA Technical Reports Server (NTRS)

    White, K. P., III

    1972-01-01

    The real-time solar monitoring information supplied to support SPARCS equipped rocket launches, the routine collection and analysis of 3.3-mm solar radio maps, short-term flare forecasts based on these maps, longer-term forecasts based on the recurrence of active regions, and an extension of the flare forecasting technique are summarized. Forecasts for expectation of a solar flare of class or = 2F are given and compared with observed flares. A total of 52 plage regions produced all the flares of class or = 1N during the study period. The following results are indicated: of the total of 21 positive forecasts, 3 were correct and 18 were incorrect; of the total of 31 negative forecasts, 3 were incorrect and 28 were correct; of a total of 6 plage regions producing large flares, 3 were correctly forecast and 3 were missed; and of 46 regions not producing any large flares, 18 were incorrectly forecast and 28 were correctly forecast.

  7. SCATTERING POLARIZATION IN SOLAR FLARES

    SciTech Connect

    Štěpán, Jiří; Heinzel, Petr

    2013-11-20

    There is ongoing debate about the origin and even the very existence of a high degree of linear polarization of some chromospheric spectral lines observed in solar flares. The standard explanation of these measurements is in terms of the impact polarization caused by non-thermal proton and/or electron beams. In this work, we study the possible role of resonance line polarization due to radiation anisotropy in the inhomogeneous medium of the flare ribbons. We consider a simple two-dimensional model of the flaring chromosphere and we self-consistently solve the non-LTE problem taking into account the role of resonant scattering polarization and of the Hanle effect. Our calculations show that the horizontal plasma inhomogeneities at the boundary of the flare ribbons can lead to a significant radiation anisotropy in the line formation region and, consequently, to a fractional linear polarization of the emergent radiation of the order of several percent. Neglecting the effects of impact polarization, our model can provide a clue for resolving some of the common observational findings, namely: (1) why a high degree of polarization appears mainly at the edges of the flare ribbons; (2) why polarization can also be observed during the gradual phase of a flare; and (3) why polarization is mostly radial or tangential. We conclude that radiation transfer in realistic multi-dimensional models of solar flares needs to be considered as an essential ingredient for understanding the observed spectral line polarization.

  8. OBSERVATIONS OF THE MAGNETIC RECONNECTION SIGNATURE OF AN M2 FLARE ON 2000 MARCH 23

    SciTech Connect

    Li Leping; Zhang Jun E-mail: zjun@ourstar.bao.ac.c

    2009-09-20

    Multiwavelength observations of an M 2.0 flare event on 2000 March 23 in the NOAA active region 8910 provide us a good chance to study the detailed structure and dynamics of the magnetic reconnection region. In the process of the flare, extreme-ultraviolet (EUV) loops displayed two types of sideward motions upon a loop-top hard X-ray source with average velocities of 75 and 25.6 km s{sup -1}, respectively. Meanwhile, a part of the loops disappeared and new post-flare loops formed. We consider these two motions to be the observational evidence of reconnection inflow, and find an X-shaped structure upon the post-flare loops during the period of the second motion. Two separations of the flare ribbons are associated with these two sideward motions, with average velocities of 3.3 and 1.3 km s{sup -1}, respectively. The sideward motions of the EUV loops and the separations of the flare ribbons are temporally consistent with two peaks of the X-ray flux. This indicates that there are two types of magnetic reconnection in the process of the flare. Using the observation of photospheric magnetic field, the velocities of the sideward motions, and the separations, we deduce the corresponding coronal magnetic field strength to be about 13.2-15.2 G, and estimate the reconnection rates to be 0.05 and 0.02 for these two magnetic reconnection processes, respectively. Besides the sideward motions of EUV loops and the separations of flare ribbons, we also observe motions of bright points upward and downward along the EUV loops with velocities ranging from 45.4 to 556.7 km s{sup -1}, which are thought to be the plasmoids accelerated in the current sheet and ejected upward and downward when magnetic reconnection occurs and energy releases. A cloud of bright material flowing outward from the loop-top hard X-ray source with an average velocity of 51 km s{sup -1} in the process of the flare may be accelerated by the tension force of the newly reconnected magnetic field lines. All the

  9. The sun's spots and flares

    NASA Technical Reports Server (NTRS)

    Rust, David M.

    1987-01-01

    The Solar Maximum Mission (SMM), designed to study the solar activity, was launched on February 14, 1980, just before the 1980 peak of sunspot and flare activity. The seven instruments aboard the SMM, information received by each of the instruments, and the performance of these instruments are described, together with the repair mission carried out to replace the attitude control module and the defective electronics in the satellite's observatory. The highlights of the scientific results obtained by the SMM mission and the new discoveries made are discussed, with special attention given to the flare loops, flare loop interactions, and the mass ejection events recorded.

  10. Solar Flare Physics

    NASA Technical Reports Server (NTRS)

    Schmahl, Edward J.; Kundu, Mukul R.

    1998-01-01

    We have continued our previous efforts in studies of fourier imaging methods applied to hard X-ray flares. We have performed physical and theoretical analysis of rotating collimator grids submitted to GSFC(Goddard Space Flight Center) for the High Energy Solar Spectroscopic Imager (HESSI). We have produced simulation algorithms which are currently being used to test imaging software and hardware for HESSI. We have developed Maximum-Entropy, Maximum-Likelihood, and "CLEAN" methods for reconstructing HESSI images from count-rate profiles. This work is expected to continue through the launch of HESSI in July, 2000. Section 1 shows a poster presentation "Image Reconstruction from HESSI Photon Lists" at the Solar Physics Division Meeting, June 1998; Section 2 shows the text and viewgraphs prepared for "Imaging Simulations" at HESSI's Preliminary Design Review on July 30, 1998.

  11. Building Big Flares: Constraining Generating Processes of Solar Flare Distributions

    NASA Astrophysics Data System (ADS)

    Wyse Jackson, T.; Kashyap, V.; McKillop, S.

    2015-12-01

    We address mechanisms which seek to explain the observed solar flare distribution, dN/dE ~ E1.8. We have compiled a comprehensive database, from GOES, NOAA, XRT, and AIA data, of solar flares and their characteristics, covering the year 2013. These datasets allow us to probe how stored magnetic energy is released over the course of an active region's evolution. We fit power-laws to flare distributions over various attribute groupings. For instance, we compare flares that occur before and after an active region reaches its maximum area, and show that the corresponding flare distributions are indistinguishable; thus, the processes that lead to magnetic reconnection are similar in both cases. A turnover in the distribution is not detectable at the energies accessible to our study, suggesting that a self-organized critical (SOC) process is a valid mechanism. However, we find changes in the distributions that suggest that the simple picture of an SOC where flares draw energy from an inexhaustible reservoir of stored magnetic energy is incomplete. Following the evolution of the flare distribution over the lifetimes of active regions, we find that the distribution flattens with time, and for larger active regions, and that a single power-law model is insufficient. This implies that flares that occur later in the lifetime of the active region tend towards higher energies. We conclude that the SOC process must have an upper bound. Increasing the scope of the study to include data from other years and more instruments will increase the robustness of these results. This work was supported by the NSF-REU Solar Physics Program at SAO, grant number AGS 1263241, NASA Contract NAS8-03060 to the Chandra X-ray Center and by NASA Hinode/XRT contract NNM07AB07C to SAO

  12. Mechanical energy output of the 5 September 1973 flare

    NASA Technical Reports Server (NTRS)

    Webb, D. F.; Cheng, C.-C.; Dulk, G. A.; Martin, S. F.; Mckenna-Lawlor, S.; Mclean, D. J.; Edberg, S. J.

    1980-01-01

    The mechanical energy flux of observed macroscopic mass plasma motions in the solar flare of Sept. 5, 1973, is estimated. Consideration is given to the cool eruptive material in the eruptive filament and large surge as revealed by H alpha observations, the moving emission front seen in Ca II as well as H alpha, the piston-driven shock and mass ejection coronal transient observed in radio spectra and flare core motions, and mechanical energy estimates of 5.6 x 10 to the 29th to 8.9 x 10 to the 30th, 9.0 x 10 to the 29th, 2 x 10 to the 30th (thermal) and 10 to the 31st (magnetic), and 9 x 10 to the 24th erg are obtained, respectively, in agreement with previous estimates. It is concluded that the mechanical energy of large-scale mass motions dominates the radiative output of the flare by more than two orders of magnitude, and that a significant portion of the mechanical energy is in the form of magnetic flux delivered to interplanetary space.

  13. Energetic electrons and photospheric electric currents during solar flares

    NASA Astrophysics Data System (ADS)

    Musset, S.; Vilmer, N.; Bommier, V.

    2015-12-01

    Solar flares are among the most energetic events in the solar system. Magnetic energy previously stored in the coronal magnetic field is transferred to particle acceleration, plasma motion and plasma heating. Magnetic energy release is likely to occur in coronal currents sheets associated with regions of strong gradient of magnetic connectivity. Coronal current sheets can be traced by their footprints at the surface on the Sun, in e.g. photospheric current ribbons. We aim to study the relationship between the current ribbons observed at the photospheric level which trace coronal current sheets, and the flare energetic electrons traced by their X-ray emissions. The photospheric magnetic field and vertical current density are calculated from SDO/HMI spectropolarimetric data using the UNNOFIT inversion and Metcalf disambiguation codes, while the X-ray images and spectra are reconstructed from RHESSI data. In a first case (the GOES X2.2 flare of February 15, 2011), a spatial correlation is observed between the photospheric current ribbons and the coronal X-ray emissions from energetic electrons (Musset et al., 2015). Moreover, a conjoint evolution of both the photospheric currents and the X-ray emission is observed during the course of the flare. Both results are interpreted as consequences of the magnetic reconnection in coronal current sheets. Propagation of the reconnection sites to new structures during the flare results in new X-ray emission sites and local increase of the photospheric currents We will examine in this contribution whether similar results are obtained for other X-class flares.

  14. Energetic electrons and photospheric electric currents during solar flares

    NASA Astrophysics Data System (ADS)

    Musset, Sophie; Vilmer, Nicole; Bommier, Veronique

    2016-07-01

    It is currently admitted that solar flares are powered by magnetic energy previously stored in the coronal magnetic field. During magnetic reconnection processes, this energy is transferred to particle acceleration, plasma motion and plasma heating. Magnetic energy release is likely to occur on coronal currents sheets along regions of strong gradient of magnetic connectivity. These coronal current sheets can be traced by their footprints at the surface on the Sun, i.e. by photospheric current ribbons. We aim to study the relation between these current ribbons observed at the photospheric level, tracing the coronal current sheets, and the flare energetic electrons traced by their X-ray emissions. The photospheric magnetic field and vertical current density have been calculated from SDO/HMI spectropolarimetric data with the UNNOFIT inversion and Metcalf disambiguation codes, while the X-ray images and spectra have been reconstructed from RHESSI data. In a first case, the GOES X2.2 flare of February 15, 2011, a spatial correlation is observed between the photospheric current ribbons and the coronal X-ray emissions from energetic electrons. Moreover, a conjoint evolution of both the photospheric currents and the X-ray emission is observed during the course of the flare. Both results are interpreted as consequences of the magnetic reconnection in coronal current sheets, and propagation of the reconnection sites to new structures during the flare, leading to new X-ray emission and local increase of the photospheric currents (Musset et al., 2015). We shall discuss here similar results obtained for other X-class flares.

  15. Current Fragmentation and Particle Acceleration in Solar Flares

    NASA Astrophysics Data System (ADS)

    Cargill, P. J.; Vlahos, L.; Baumann, G.; Drake, J. F.; Nordlund, Å.

    2012-11-01

    Particle acceleration in solar flares remains an outstanding problem in plasma physics and space science. While the observed particle energies and timescales can perhaps be understood in terms of acceleration at a simple current sheet or turbulence site, the vast number of accelerated particles, and the fraction of flare energy in them, defies any simple explanation. The nature of energy storage and dissipation in the global coronal magnetic field is essential for understanding flare acceleration. Scenarios where the coronal field is stressed by complex photospheric motions lead to the formation of multiple current sheets, rather than the single monolithic current sheet proposed by some. The currents sheets in turn can fragment into multiple, smaller dissipation sites. MHD, kinetic and cellular automata models are used to demonstrate this feature. Particle acceleration in this environment thus involves interaction with many distributed accelerators. A series of examples demonstrate how acceleration works in such an environment. As required, acceleration is fast, and relativistic energies are readily attained. It is also shown that accelerated particles do indeed interact with multiple acceleration sites. Test particle models also demonstrate that a large number of particles can be accelerated, with a significant fraction of the flare energy associated with them. However, in the absence of feedback, and with limited numerical resolution, these results need to be viewed with caution. Particle in cell models can incorporate feedback and in one scenario suggest that acceleration can be limited by the energetic particles reaching the condition for firehose marginal stability. Contemporary issues such as footpoint particle acceleration are also discussed. It is also noted that the idea of a "standard flare model" is ill-conceived when the entire distribution of flare energies is considered.

  16. Chandra Monitors the Flaring Crab

    NASA Video Gallery

    Scientists hoped that NASA's Chandra X-ray Observatory would locate X-ray sources correlated to the gamma-ray flares seen by Fermi and Italy's AGILE satellites. Two observations were made during th...

  17. Mass ejections. [during solar flares

    NASA Technical Reports Server (NTRS)

    Rust, D. M.; Hildner, E.; Hansen, R. T.; Dryer, M.; Mcclymont, A. N.; Mckenna-Lawlor, S. M. P.; Mclean, D. J.; Schmahl, E. J.; Steinolfson, R. S.; Tandberg-Hanssen, E.

    1980-01-01

    Observations and model simulations of solar mass ejection phenomena are examined in an investigation of flare processes. Consideration is given to Skylab and other observations of flare-associated sprays, eruptive prominences, surges and coronal transients, and to MHD, gas dynamic and magnetic loop models developed to account for them. Magnetic forces are found to confine spray material, which originates in preexisting active-region filaments, within steadily expanding loops, while surges follow unmoving, preexisting magnetic field lines. Simulations of effects of a sudden pressure pulse at the bottom of the corona are found to exhibit many characteristics of coronal transients associated with flares, and impulsive heating low in the chromosphere is found to be able to account for surges. The importance of the magnetic field as the ultimate source of energy which drives eruptive phenomena as well as flares is pointed out.

  18. Testing Solar Flare Models with BATSE

    NASA Technical Reports Server (NTRS)

    Zarro, Dominic M.

    1995-01-01

    We propose to use high-sensitivity Burst and Transient Source Experiment (BATSE) hard X-ray observations to test the thick-target and electric field acceleration models of solar flares. We will compare the predictions made by these models with hard X-ray spectral observations obtained with BATSE and simultaneous soft X-ray Ca XIX emission observed with the Yohkoh Bragg Crystal Spectrometer (BCS). The increased sensitivities of the BATSE and BCS (relative to previous detectors) permits a renewed study of the relationship between heating and dynamical motions during the crucial rise phase of flares. With these observations, we will: (1) investigate the ability of the thick-target model to explain the temporal evolution of hard X-ray emission relative to the soft X-ray blueshift during the earliest stages of the impulsive phase; and (2) search for evidence of electric-field acceleration as implied by temporal correlations between hard X-ray spectral breaks and the Ca XIX blueshift. The proposed study will utilize hard X-ray lightcurve and spectral measurements in the 10-100 keV energy range obtained with the BATSE Large Area Detectors (LAD). The DISCLA and CONT data will be the primary data products used in this analysis.

  19. Particle acceleration in solar flares

    NASA Technical Reports Server (NTRS)

    Ramaty, R.; Forman, M. A.

    1987-01-01

    The most direct signatures of particle acceleration in flares are energetic particles detected in interplanetary space and in the Earth atmosphere, and gamma rays, neutrons, hard X-rays, and radio emissions produced by the energetic particles in the solar atmosphere. The stochastic and shock acceleration theories in flares are reviewed and the implications of observations on particle energy spectra, particle confinement and escape, multiple acceleration phases, particle anistropies, and solar atmospheric abundances are discussed.

  20. Simulating VIIRS Observed Gas Flare

    NASA Astrophysics Data System (ADS)

    Hsu, F. C.

    2015-12-01

    VIIRS Nightfire (VNF) had been proved being able to effectively detect gas flares at night, and characterize their temperature and source size. [1] However, limited access to generally confidential gas flare operation measurements made it difficult to verify the output. Although flared gas volume is occasionally available, it is not common to log the temperature and flames size which directly links to VNF output. To understand the mechanism of gas flare and how VIIRS perceives the event, a platform is proposed to simulate the gas flare being observed by VIIRS. The methodology can be described in three steps. (1) Use CFD simulation software ISIS-3D to simulate a simple gas flare. [2] Scalar fields of temperature and species concentration related to combustion are extracted from the simulation. The instantaneous scalar can be determined from time-averaging or guess by stochastic time and space series (TASS) from single-point statistics [3]. (2) Model spectral radiance intensity of simulated gas flare using RADCAL. [4] RADCAL developed by NIST can accurately model the spectral radiance emitted on the direction of lineof-sight given the spatial profile of temperature and concentration of species. (3) Use radiative transfer modeling to calculate the energy propagated to VIIRS. The modeled radiation will then be weighted by the MODTRAN [5] modeled transmissivity over predefined atmosphere to the satellite, with geometrical effects considered. Such platform can help understanding how exactly VNF is measuring gas flares, and thus lead to more precise characterization of combustion events. [1] C. D. Elvidge et al, Remote Sensing, 2013[2] IRSN ISIS-3D[3] M. E. Kounalakis et al, ASME J. Heat Transfer, 1991 [4] W. L. Grosshandler, NIST Technical Note 1402, 1993 [5] A. Berk et al, MODTRAN 5.2.0.0 User's Manual

  1. Rapid fluctuations in solar flares

    NASA Technical Reports Server (NTRS)

    Sturrock, Peter A.

    1986-01-01

    Study of rapid fluctuations in the emission of radiation from solar flares provides a promising approach for probing the magneto-plasma structure and plasma processes that are responsible for a flare. It is proposed that elementary flare bursts in X-ray and microwave emission may be attributed to fine structure of the coronal magnetic field, related to the aggregation of photospheric magnetic field into magnetic knots. Fluctuations that occur on a subsecond time-scale may be due to magnetic islands that develop in current sheets during magnetic reconnection. The impulsive phase may sometimes represent the superposition of a large number of the elementary energy-release processes responsible for elementary flare bursts. If so, the challenge of trying to explain the properties of the impulsive phase in terms of the properties of the elementary processes must be faced. Magnetic field configurations that might produce solar flares are divided into a number of categories, depending on: whether or not there is a filament; whether there is no current sheet, a closed current sheet, or an open current sheet; and whether the filament erupts into the corona, or is ejected completely from the Sun's atmosphere. Analysis of the properties of these possible configurations is compared with different types of flares, and to Bai's subdivision of gamma-ray/proton events.

  2. Thermal instability in post-flare plasmas

    NASA Technical Reports Server (NTRS)

    Antiochos, S. K.

    1976-01-01

    The cooling of post-flare plasmas is discussed and the formation of loop prominences is explained as due to a thermal instability. A one-dimensional model was developed for active loop prominences. Only the motion and heat fluxes parallel to the existing magnetic fields are considered. The relevant size scales and time scales are such that single-fluid MHD equations are valid. The effects of gravity, the geometry of the field and conduction losses to the chromosphere are included. A computer code was constructed to solve the model equations. Basically, the system is treated as an initial value problem (with certain boundary conditions at the chromosphere-corona transition region), and a two-step time differencing scheme is used.

  3. SIMULATING THE EFFECTS OF INITIAL PITCH-ANGLE DISTRIBUTIONS ON SOLAR FLARES

    SciTech Connect

    Winter, Henry D.; Reeves, Katharine K.; Martens, Petrus

    2011-07-10

    In this work, we model both the thermal and non-thermal components of solar flares. The model we use, HYLOOP, combines a hydrodynamic equation solver with a non-thermal particle tracking code to simulate the thermal and non-thermal dynamics and emission of solar flares. In order to test the effects of pitch-angle distribution on flare dynamics and emission, a series of flares is simulated with non-thermal electron beams injected at the loop apex. The pitch-angle distribution of each beam is described by a single parameter and allowed to vary from flare to flare. We use the results of these simulations to generate synthetic hard and soft X-ray emissions (HXR and SXR). The light curves of the flares in Hinode's X-ray Telescope passbands show a distinct signal that is highly dependent on pitch-angle distribution. The simulated HXR emission in the 3-6 keV bandpass shows the formation and evolution of emission sources that correspond well to the observations of pre-impulsive flares. This ability to test theoretical models of thermal and non-thermal flare dynamics directly with observations allows for the investigation of a wide range of physical processes governing the evolution of solar flares. We find that the initial pitch-angle distribution of non-thermal particle populations has a profound effect on loop top HXR and SXR emission and that apparent motion of HXR is a natural consequence of non-thermal particle evolution in a magnetic trap.

  4. A comparative study between clinical grading of anterior chamber flare and flare reading using the Kowa laser flare meter.

    PubMed

    Konstantopoulou, Kallirroi; Del'Omo, Roberto; Morley, Anne M; Karagiannis, Dimitris; Bunce, Catey; Pavesio, Carlos

    2015-10-01

    To assess the accuracy of standard clinical grading of aqueous flare in uveitis according to the Standardization of Uveitis Nomenclature consensus, and compare the results with the readings of the laser flare meter, Kowa 500. Two examiners clinically graded the flare in 110 eyes. The flare was then measured using the Kowa laser flare meter. Twenty-nine eyes were graded as anterior chamber flare +2; for 18 of these, the clinicians were in agreement, the rest differed by the order of one grade. The range of the laser flare meter for these eyes was 5.2-899.1 photons/ms. The median value was 41.4. Seventy-four eyes were graded with flare +1. Agreement was established in 51 of these eyes. Disagreement for the rest was again by the order of 1, and the flare meter range was 1.1-169.9 photons/ms, median value 18.4. For the clinical measure of flare 0, the clinicians disagreed on three out of five eyes. The flare meter readings ranged from 2.5 to 14.1 photons/ms, median value 9.9. Only two eyes were graded with flare +3 and there was one step disagreement on both of them. We found little evidence of association between the flare readings and intraocular pressure or age. Our findings suggest that clinical evaluation of aqueous flare is subjective. Compared with the Kowa laser flare meter's numeric readings, the discrepancies observed indicate that clinical grading is an approximate science. The laser flare meter provides an accurate, reproducible, non-invasive assessment of aqueous flare that can prove valuable in research and clinical decisions.

  5. Modeling solar flare hard X-ray images and spectra observed with RHESSI

    NASA Astrophysics Data System (ADS)

    Sui, Linhui

    2004-12-01

    predictions of the standard flare models: the downward motion of flare loops in the early impulsive phase of each flare, and an initially stationary coronal source above the loops. These features are believed to be related to the formation and development of a current sheet. In particular, the downward loop motion seems to be a common phenomenon in flares, suggesting the necessity for modifications to the existing standard flare models. Finally, thanks to the broad energy coverage of the RHESSI spectra, a low- energy cutoff of 28(+/-2) keV in the nonthermal electron distribution was determined for the April 15, 2002, flare. As a result, the energy carried by the nonthermal electrons is found to be comparable to the thermal energy of the flare, but one order of magnitude larger than the kinetic energy of the associated coronal mass ejection. The method used to deduce the electron low- energy cutoff will be useful in the analyses of similar events.

  6. Starspots on flare stars

    NASA Technical Reports Server (NTRS)

    Mullan, D. J.

    1974-01-01

    Sizes of starspots on flare stars can be derived from the author's convection-cell hypothesis. The sizes are in fair agreement with those observed on YY Gem, CC Eri, and BY Dra by Bopp and Evans (1973). The hypothesis predicts that periodic brightness variations due to starspots are restricted to stars brighter than a critical absolute visual magnitude. A convective model of a starspot on YY Gem has been computed, assuming that the missing flux is in the form of Alfven waves. It is found that the surface field must exceed 10,000 G, and is probably less than about 30,000 G. With a surface field of 20,000 G, the effective temperature of the spot is in the range from 1590 to 1890 K, depending on the field gradient. These figures are to be compared with an effective temperature of 2000 K estimated from observations by Bopp and Evans. Efficient dynamo action is shown to be a possible mechanism for generating such large surface fields. There is a possibility that tidal effects may influence starspot formation.

  7. Trigger of a Blowout Jet in a Solar Coronal Mass Ejection Associated with a Flare

    NASA Astrophysics Data System (ADS)

    Li, Xiaohong; Yang, Shuhong; Chen, Huadong; Li, Ting; Zhang, Jun

    2015-11-01

    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 the 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.

  8. TRIGGER OF A BLOWOUT JET IN A SOLAR CORONAL MASS EJECTION ASSOCIATED WITH A FLARE

    SciTech Connect

    Li, Xiaohong; Yang, Shuhong; Chen, Huadong; Li, Ting; Zhang, Jun

    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 the 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.

  9. Photospheric, Chromospheric and Helioseismic Signatures of a Large Flare in Super-active Region NOAA 10486

    NASA Astrophysics Data System (ADS)

    Ambastha, Ashok

    2006-09-01

    NOAA 10486 produced several powerful flares, including the 4B/X17.2 superflare of October 28, 2003/11:10 UT. This flare was extensively covered by the Hα and GONG instruments operated at the Udaipur Solar Observatory (USO). The central location of the active region on October 28, 2003 was well-suited for the ring diagram analysis to obtain the 3-D power spectra and search for helioseismic response of this large flare on the amplitude, frequency and width of the p-modes. Further, using USO observations, we have identified the sites of new flux emergences, large proper motions and line-of-sight velocity flows in the active region and their relationship with the flare.

  10. THE SOLAR FLARE IRON ABUNDANCE

    SciTech Connect

    Phillips, K. J. H.; Dennis, B. R. E-mail: Brian.R.Dennis@nasa.gov

    2012-03-20

    The abundance of iron is measured from emission line complexes at 6.65 keV (Fe line) and 8 keV (Fe/Ni line) in RHESSI X-ray spectra during solar flares. Spectra during long-duration flares with steady declines were selected, with an isothermal assumption and improved data analysis methods over previous work. Two spectral fitting models give comparable results, viz., an iron abundance that is lower than previous coronal values but higher than photospheric values. In the preferred method, the estimated Fe abundance is A(Fe) = 7.91 {+-} 0.10 (on a logarithmic scale, with A(H) = 12) or 2.6 {+-} 0.6 times the photospheric Fe abundance. Our estimate is based on a detailed analysis of 1898 spectra taken during 20 flares. No variation from flare to flare is indicated. This argues for a fractionation mechanism similar to quiet-Sun plasma. The new value of A(Fe) has important implications for radiation loss curves, which are estimated.

  11. Largest Solar Flare on Record

    NASA Technical Reports Server (NTRS)

    2001-01-01

    The largest solar flare ever recorded occurred at 4:51 p.m. EDT, on Monday, April 2, 2001. as Observed by the Solar and Heliospheric Observatory (SOHO) satellite. Solar flares, among the solar systems mightiest eruptions, are tremendous explosions in the atmosphere of the Sun capable of releasing as much energy as a billion megatons of TNT. Caused by the sudden release of magnetic energy, in just a few seconds, solar flares can accelerate solar particles to very high velocities, almost to the speed of light, and heat solar material to tens of millions of degrees. The recent explosion from the active region near the sun's northwest limb hurled a coronal mass ejection into space at a whopping speed of roughly 7.2 million kilometers per hour. Luckily, the flare was not aimed directly towards Earth. Second to the most severe R5 classification of radio blackout, this flare produced an R4 blackout as rated by the NOAA SEC. This classification measures the disruption in radio communications. Launched December 2, 1995 atop an ATLAS-IIAS expendable launch vehicle, the SOHO is a cooperative effort involving NASA and the European Space Agency (ESA). (Image courtesy NASA Goddard SOHO Project office)

  12. A unified view of coronal loop contraction and oscillation in flares

    NASA Astrophysics Data System (ADS)

    Russell, A. J. B.; Simões, P. J. A.; Fletcher, L.

    2015-09-01

    Context. Transverse loop oscillations and loop contractions are commonly associated with solar flares, but the two types of motion have traditionally been regarded as separate phenomena. Aims: We present an observation of coronal loops that contract and oscillate following the onset of a flare. We aim to explain why both behaviours are seen together and why only some of the loops oscillate. Methods: A time sequence of SDO/AIA 171 Å images is analysed to identify the positions of coronal loops following the onset of the M6.4 flare SOL2012-03-09T03:53. We focus on five loops in particular, all of which contract during the flare, with three of them oscillating as well. A simple model is then developed for the contraction and oscillation of a coronal loop. Results: We propose that coronal loop contractions and oscillations can occur in a single response to removal of magnetic energy from the corona. Our model reproduces the various types of loop motion observed and explains why the highest loops oscillate during their contraction, while no oscillation is detected for the shortest contracting loops. The proposed framework suggests that loop motions can be used as a diagnostic for the removal of coronal magnetic energy by flares, while rapid decrease in coronal magnetic energy is a newly identified excitation mechanism for transverse loop oscillations. Appendices are available in electronic form at http://www.aanda.org Warning, no authors found for 2015A&A...581A..14.

  13. Astrophysics: Unexpected X-ray flares

    NASA Astrophysics Data System (ADS)

    Campana, Sergio

    2016-10-01

    Two sources of highly energetic flares have been discovered in archival X-ray data of 70 nearby galaxies. These flares have an undetermined origin and might represent previously unknown astrophysical phenomena. See Letter p.356

  14. What's an Asthma Flare-Up?

    MedlinePlus

    ... Things to Know About Zika & Pregnancy What's an Asthma Flare-Up? KidsHealth > For Parents > What's an Asthma ... of a straw that's being pinched. Causes of Asthma Flare-Ups People with asthma have airways that ...

  15. IMPLOSION OF CORONAL LOOPS DURING THE IMPULSIVE PHASE OF A SOLAR FLARE

    SciTech Connect

    Simões, P. J. A.; Fletcher, L.; Hudson, H. S.; Russell, A. J. B. E-mail: lyndsay.fletcher@glasgow.ac.uk E-mail: hhudson@ssl.berkeley.edu

    2013-11-10

    We study the relationship between implosive motions in a solar flare, and the energy redistribution in the form of oscillatory structures and particle acceleration. The flare SOL2012-03-09T03:53 (M6.4) shows clear evidence for an irreversible (stepwise) coronal implosion. Extreme-ultraviolet (EUV) images show at least four groups of coronal loops at different heights overlying the flaring core undergoing fast contraction during the impulsive phase of the flare. These contractions start around a minute after the flare onset, and the rate of contraction is closely associated with the intensity of the hard X-ray and microwave emissions. They also seem to have a close relationship with the dimming associated with the formation of the coronal mass ejection and a global EUV wave. Several studies now have detected contracting motions in the corona during solar flares that can be interpreted as the implosion necessary to release energy. Our results confirm this, and tighten the association with the flare impulsive phase. We add to the phenomenology by noting the presence of oscillatory variations revealed by Geostationary Operational Environmental Satellite soft X-rays (SXR) and spatially integrated EUV emission at 94 and 335 Å. We identify pulsations of ≈60 s in SXR and EUV data, which we interpret as persistent, semi-regular compressions of the flaring core region which modulate the plasma temperature and emission measure. The loop oscillations, observed over a large region, also allow us to provide rough estimates of the energy temporarily stored in the eigenmodes of the active-region structure as it approaches its new equilibrium.

  16. Chasing White-Light Flares

    NASA Astrophysics Data System (ADS)

    Hudson, H. S.

    2016-05-01

    In this memoir I describe my life in research, mostly in the area of solar physics. The recurring theme is "white-light flares," and several sections of this paper deal with this and related phenomena; I wind up describing how I see the state of the art in this still-interesting and crucially important (as it has been since 1859) area of flare research. I also describe my participation in two long-lived satellite programs dedicated to solar observations ( Yohkoh and RHESSI) and elaborate on their discoveries. These have both helped with white-light flares both directly and also with closely related X-ray and γ-ray emissions), with the result that this article leans heavily in that direction.

  17. 6Li from Solar Flares.

    PubMed

    Ramaty; Tatischeff; Thibaud; Kozlovsky; Mandzhavidze

    2000-05-10

    By introducing a hitherto ignored 6Li producing process, due to accelerated 3He reactions with 4He, we show that accelerated particle interactions in solar flares produce much more 6Li than 7Li. By normalizing our calculations to gamma-ray data, we demonstrate that the 6Li produced in solar flares, combined with photospheric 7Li, can account for the recently determined solar wind lithium isotopic ratio, obtained from measurements in lunar soil, provided that the bulk of the flare-produced lithium is evacuated by the solar wind. Further research in this area could provide unique information on a variety of problems, including solar atmospheric transport and mixing, solar convection and the lithium depletion issue, and solar wind and solar particle acceleration.

  18. Effects of camera location on the reconstruction of 3D flare trajectory with two cameras

    NASA Astrophysics Data System (ADS)

    Özsaraç, Seçkin; Yeşilkaya, Muhammed

    2015-05-01

    Flares are used as valuable electronic warfare assets for the battle against infrared guided missiles. The trajectory of the flare is one of the most important factors that determine the effectiveness of the counter measure. Reconstruction of the three dimensional (3D) position of a point, which is seen by multiple cameras, is a common problem. Camera placement, camera calibration, corresponding pixel determination in between the images of different cameras and also the triangulation algorithm affect the performance of 3D position estimation. In this paper, we specifically investigate the effects of camera placement on the flare trajectory estimation performance by simulations. Firstly, 3D trajectory of a flare and also the aircraft, which dispenses the flare, are generated with simple motion models. Then, we place two virtual ideal pinhole camera models on different locations. Assuming the cameras are tracking the aircraft perfectly, the view vectors of the cameras are computed. Afterwards, using the view vector of each camera and also the 3D position of the flare, image plane coordinates of the flare on both cameras are computed using the field of view (FOV) values. To increase the fidelity of the simulation, we have used two sources of error. One is used to model the uncertainties in the determination of the camera view vectors, i.e. the orientations of the cameras are measured noisy. Second noise source is used to model the imperfections of the corresponding pixel determination of the flare in between the two cameras. Finally, 3D position of the flare is estimated using the corresponding pixel indices, view vector and also the FOV of the cameras by triangulation. All the processes mentioned so far are repeated for different relative camera placements so that the optimum estimation error performance is found for the given aircraft and are trajectories.

  19. The smallest hard X-ray flare?

    NASA Astrophysics Data System (ADS)

    Glesener, Lindsay; Krucker, Sam; Hannah, Iain; Smith, David M.; Grefenstette, Brian; Marsh, Andrew; Hudson, Hugh S.; White, Stephen M.; Chen, Bin

    2016-05-01

    We report a NuSTAR observation of a small solar flare on 2015 September 1, estimated to be on the order of a GOES class A.05 flare in brightness. This flare is fainter than any hard X-ray (HXR) flares in the existing literature, and with a peak rate of only ˜5 counts s-1 detector-1 observed by RHESSI, is effectively the smallest that can just barely be detected by the current standard (indirectly imaging) solar HXR instrumentation, though we expect that smaller flares will continue to be discovered as instrumental and observational techniques progress. The flare occurred during a solar observation by the highly sensitive NuSTAR astrophysical HXR spacecraft, which used its direct focusing optics to produce detailed flare spectra and images. The flare exhibits properties commonly observed in larger flares, including a fast rise and more gradual decay, and similar spatial dimensions to the RHESSI microflares. We will discuss the presence of non-thermal (flare-accelerated) electrons during the impulsive phase. The flare is small in emission measure, temperature, and energy, though not in physical dimensions. Its presence is an indication that flares do indeed scale down to smaller energies and retain what we customarily think of as “flarelike” properties.

  20. Forming tool improves quality of tubing flares

    NASA Technical Reports Server (NTRS)

    1966-01-01

    Punch and die set improves the quality of tubing flares for use with standard flared-tube fittings in high-pressure systems. It forges a dimensionally accurate flare in the tubing and forces more tubing material into the high-stress areas to improve the strength and tightness of the tubing connection.

  1. FAST CONTRACTION OF CORONAL LOOPS AT THE FLARE PEAK

    SciTech Connect

    Liu Rui; Wang Haimin

    2010-05-01

    On 2005 September 8, a coronal loop overlying the active region NOAA 10808 was observed in TRACE 171 A to contract at {approx}100 km s{sup -1} at the peak of an X5.4-2B flare at 21:05 UT. Prior to the fast contraction, the loop underwent a much slower contraction at {approx}6 km s{sup -1} for about 8 minutes, initiating during the flare preheating phase. The sudden switch to fast contraction is presumably corresponding to the onset of the impulsive phase. The contraction resulted in the oscillation of a group of loops located below, with the period of about 10 minutes. Meanwhile, the contracting loop exhibited a similar oscillatory pattern superimposed on the dominant downward motion. We suggest that the fast contraction reflects a suddenly reduced magnetic pressure underneath due either to (1) the eruption of magnetic structures located at lower altitudes or to (2) the rapid conversion of magnetic free energy in the flare core region. Electrons accelerated in the shrinking trap formed by the contracting loop can theoretically contribute to a late-phase hard X-ray burst, which is associated with Type IV radio emission. To complement the X5.4 flare which was probably confined, a similar event observed in SOHO/EIT 195 A on 2004 July 20 in an eruptive, M8.6 flare is briefly described, in which the contraction was followed by the expansion of the same loop leading up to a halo coronal mass ejection. These observations further substantiate the conjecture of coronal implosion and suggest coronal implosion as a new exciter mechanism for coronal loop oscillations.

  2. Complex Dynamic Flows in Solar Flare Sheet Structures

    NASA Technical Reports Server (NTRS)

    McKenzie, David E.; Reeves, Katharine K.; Savage, Sabrina

    2012-01-01

    Observations of high-energy emission from solar flares often reveal the presence of large sheet-like structures, sometimes extending over a space comparable to the Sun's radius. Given that these structures are found between a departing coronal mass ejection and the post-eruption flare arcade, it is natural to associate the structure with a current sheet; though the relationship is unclear. Moreover, recent high-resolution observations have begun to reveal that the motions in this region are highly complex, including reconnection outflows, oscillations, and apparent wakes and eddies. We present a detailed first look at the complicated dynamics within this supra-arcade plasma, and consider implications for the interrelationship between the plasma and its embedded magnetic field.

  3. Arches showing UV flaring activity

    NASA Technical Reports Server (NTRS)

    Fontenla, J. M.

    1988-01-01

    The UVSP data obtained in the previous maximum activity cycle show the frequent appearance of flaring events in the UV. In many cases these flaring events are characterized by at least two footpoints which show compact impulsive non-simultaneous brightenings and a fainter but clearly observed arch developes between the footpoints. These arches and footpoints are observed in line corresponding to different temperatures, as Lyman alpha, N V, and C IV, and when observed above the limb display large Doppler shifts at some stages. The size of the arches can be larger than 20 arcsec.

  4. CHROMOSPHERIC EVAPORATION IN AN X1.0 FLARE ON 2014 MARCH 29 OBSERVED WITH IRIS AND EIS

    SciTech Connect

    Li, Y.; Ding, M. D.; Qiu, J.; Cheng, J. X.

    2015-09-20

    Chromospheric evaporation refers to dynamic mass motions in flare loops as a result of rapid energy deposition in the chromosphere. These motions have been observed as blueshifts in X-ray and extreme-ultraviolet (EUV) spectral lines corresponding to upward motions at a few tens to a few hundreds of km s{sup −1}. Past spectroscopic observations have also revealed a dominant stationary component, in addition to the blueshifted component, in emission lines formed at high temperatures (∼10 MK). This is contradictory to evaporation models predicting predominant blueshifts in hot lines. The recently launched Interface Region Imaging Spectrograph (IRIS) provides high-resolution imaging and spectroscopic observations that focus on the chromosphere and transition region in the UV passband. Using the new IRIS observations, combined with coordinated observations from the EUV Imaging Spectrometer, we study the chromospheric evaporation process from the upper chromosphere to the corona during an X1.0 flare on 2014 March 29. We find evident evaporation signatures, characterized by Doppler shifts and line broadening, at two flare ribbons that are separating from each other, suggesting that chromospheric evaporation takes place in successively formed flaring loops throughout the flare. More importantly, we detect dominant blueshifts in the high-temperature Fe xxi line (∼10 MK), in agreement with theoretical predictions. We also find that, in this flare, gentle evaporation occurs at some locations in the rise phase of the flare, while explosive evaporation is detected at some other locations near the peak of the flare. There is a conversion from gentle to explosive evaporation as the flare evolves.

  5. PREDICTION OF SOLAR FLARE SIZE AND TIME-TO-FLARE USING SUPPORT VECTOR MACHINE REGRESSION

    SciTech Connect

    Boucheron, Laura E.; Al-Ghraibah, Amani; McAteer, R. T. James

    2015-10-10

    We study the prediction of solar flare size and time-to-flare using 38 features describing magnetic complexity of the photospheric magnetic field. This work uses support vector regression to formulate a mapping from the 38-dimensional feature space to a continuous-valued label vector representing flare size or time-to-flare. When we consider flaring regions only, we find an average error in estimating flare size of approximately half a geostationary operational environmental satellite (GOES) class. When we additionally consider non-flaring regions, we find an increased average error of approximately three-fourths a GOES class. We also consider thresholding the regressed flare size for the experiment containing both flaring and non-flaring regions and find a true positive rate of 0.69 and a true negative rate of 0.86 for flare prediction. The results for both of these size regression experiments are consistent across a wide range of predictive time windows, indicating that the magnetic complexity features may be persistent in appearance long before flare activity. This is supported by our larger error rates of some 40 hr in the time-to-flare regression problem. The 38 magnetic complexity features considered here appear to have discriminative potential for flare size, but their persistence in time makes them less discriminative for the time-to-flare problem.

  6. Biggest Solar Flare on Record

    NASA Technical Reports Server (NTRS)

    2002-01-01

    View an animation from the Extreme ultraviolet Imaging Telescope (EIT). At 4:51 p.m. EDT, on Monday, April 2, 2001, the sun unleashed the biggest solar flare ever recorded, as observed by the Solar and Heliospheric Observatory (SOHO) satellite. The flare was definitely more powerful than the famous solar flare on March 6, 1989, which was related to the disruption of power grids in Canada. This recent explosion from the active region near the sun's northwest limb hurled a coronal mass ejection into space at a whopping speed of roughly 7.2 million kilometers per hour. Luckily, the flare was not aimed directly towards Earth. Solar flares, among the solar system's mightiest eruptions, are tremendous explosions in the atmosphere of the Sun capable of releasing as much energy as a billion megatons of TNT. Caused by the sudden release of magnetic energy, in just a few seconds flares can accelerate solar particles to very high velocities, almost to the speed of light, and heat solar material to tens of millions of degrees. Solar ejections are often associated with flares and sometimes occur shortly after the flare explosion. Coronal mass ejections are clouds of electrified, magnetic gas weighing billions of tons ejected from the Sun and hurled into space with speeds ranging from 12 to 1,250 miles per second. Depending on the orientation of the magnetic fields carried by the ejection cloud, Earth-directed coronal mass ejections cause magnetic storms by interacting with the Earth's magnetic field, distorting its shape, and accelerating electrically charged particles (electrons and atomic nuclei) trapped within. Severe solar weather is often heralded by dramatic auroral displays, northern and southern lights, and magnetic storms that occasionally affect satellites, radio communications and power systems. The flare and solar ejection has also generated a storm of high-velocity particles, and the number of particles with ten million electron-volts of energy in the space near

  7. Evolution of Magnetic and Velocity Fields in Super-active Region NOAA10486 and the Large 4B/X17.2 Flare of October 28, 2003

    NASA Astrophysics Data System (ADS)

    Ambastha, A.

    2007-08-01

    We have used high cadence GONG + photospheric magnetograms, dopplergrams and Udaipur Solar Observatory (USO) chromospheric Hα-filtergrams to study the spatial and temporal evolution of the active region NOAA 10486 in relation to the X17.2/4B flare of October 28, 2003. New flux emergences, large proper motions and development of steady velocity flows have been identified around the flare site. In addition, filament activation and eruption leading to fast CMEs were noticed. During the flare, NOAA 10486 was located near the disk-center; well suited for the ring diagram analysis. Therefore, we have obtained the 3-D power spectra to search for helioseismic response of the large flare on the amplitude, frequency and width of the p-modes. Power enhancement was found during the post-flare phase, and NOAA 10486 possessed steep gradient in the meridional velocity as compared to the less flare-productive active regions.

  8. High-cadence and High-resolution Hα Imaging Spectroscopy of a Circular Flare's Remote Ribbon with IBIS

    NASA Astrophysics Data System (ADS)

    Deng, Na; Tritschler, Alexandra; Jing, Ju; Chen, Xin; Liu, Chang; Reardon, Kevin; Denker, Carsten; Xu, Yan; Wang, Haimin

    2013-06-01

    We present an unprecedented high-resolution Hα imaging spectroscopic observation of a C4.1 flare taken with the Interferometric Bidimensional Spectrometer (IBIS) in conjunction with the adaptive optics system at the 76 cm Dunn Solar Telescope on 2011 October 22 in the active region NOAA 11324. Such a two-dimensional spectroscopic observation covering the entire evolution of a flare ribbon with high spatial (0.''1 pixel-1 image scale), cadence (4.8 s), and spectral (0.1 Å step size) resolution is rarely reported. The flare consists of a main circular ribbon that occurred in a parasitic magnetic configuration and a remote ribbon that was observed by the IBIS. Such a circular-ribbon flare with a remote brightening is predicted in three-dimensional fan-spine reconnection but so far has been rarely studied. During the flare impulsive phase, we define "core" and "halo" structures in the observed ribbon based on IBIS narrowband images in the Hα line wing and line center. Examining the Hα emission spectra averaged in the flare core and halo areas, we find that only those from the flare cores show typical nonthermal electron beam heating characteristics that have been revealed by previous theoretical simulations and observations of flaring Hα line profiles. These characteristics include broad and centrally reversed emission spectra, excess emission in the red wing with regard to the blue wing (i.e., red asymmetry), and redshifted bisectors of the emission spectra. We also observe rather quick timescales for the heating (~30 s) and cooling (~14-33 s) in the flare core locations. Therefore, we suggest that the flare cores revealed by IBIS track the sites of electron beam precipitation with exceptional spatial and temporal resolution. The flare cores show two-stage motion (a parallel motion along the ribbon followed by an expansion motion perpendicular to the ribbon) during the two impulsive phases of the flare. Some cores jump quickly (30 km s-1) between discrete

  9. High-cadence and high-resolution Hα imaging spectroscopy of a circular flare's remote ribbon with IBIS

    SciTech Connect

    Deng, Na; Jing, Ju; Chen, Xin; Liu, Chang; Xu, Yan; Wang, Haimin; Tritschler, Alexandra; Reardon, Kevin; Denker, Carsten

    2013-06-01

    We present an unprecedented high-resolution Hα imaging spectroscopic observation of a C4.1 flare taken with the Interferometric Bidimensional Spectrometer (IBIS) in conjunction with the adaptive optics system at the 76 cm Dunn Solar Telescope on 2011 October 22 in the active region NOAA 11324. Such a two-dimensional spectroscopic observation covering the entire evolution of a flare ribbon with high spatial (0.''1 pixel{sup –1} image scale), cadence (4.8 s), and spectral (0.1 Å step size) resolution is rarely reported. The flare consists of a main circular ribbon that occurred in a parasitic magnetic configuration and a remote ribbon that was observed by the IBIS. Such a circular-ribbon flare with a remote brightening is predicted in three-dimensional fan-spine reconnection but so far has been rarely studied. During the flare impulsive phase, we define 'core' and 'halo' structures in the observed ribbon based on IBIS narrowband images in the Hα line wing and line center. Examining the Hα emission spectra averaged in the flare core and halo areas, we find that only those from the flare cores show typical nonthermal electron beam heating characteristics that have been revealed by previous theoretical simulations and observations of flaring Hα line profiles. These characteristics include broad and centrally reversed emission spectra, excess emission in the red wing with regard to the blue wing (i.e., red asymmetry), and redshifted bisectors of the emission spectra. We also observe rather quick timescales for the heating (∼30 s) and cooling (∼14-33 s) in the flare core locations. Therefore, we suggest that the flare cores revealed by IBIS track the sites of electron beam precipitation with exceptional spatial and temporal resolution. The flare cores show two-stage motion (a parallel motion along the ribbon followed by an expansion motion perpendicular to the ribbon) during the two impulsive phases of the flare. Some cores jump quickly (30 km s{sup –1

  10. Large-scale brightenings associated with flares

    NASA Technical Reports Server (NTRS)

    Mandrini, Cristina H.; Machado, Marcos E.

    1992-01-01

    It is shown that large-scale brightenings (LSBs) associated with solar flares, similar to the 'giant arches' discovered by Svestka et al. (1982) in images obtained by the SSM HXIS hours after the onset of two-ribbon flares, can also occur in association with confined flares in complex active regions. For these events, a clear link between the LSB and the underlying flare is clearly evident from the active-region magnetic field topology. The implications of these findings are discussed within the framework of the interacting loops of flares and the giant arch phenomenology.

  11. The Magnetic Evolution of AR 6555 which led to Two Impulsive, Relatively Compact, X-Type Flares

    NASA Technical Reports Server (NTRS)

    Fontenla, J. M.; Ambastha, A.; Kalman, B.; Csepura, Gy.

    1995-01-01

    We study the evolution of the vector magnetic field and the sunspot motions observed in AR 6555 during 1991 March 23-26. This region displays two locations of large magnetic shear that were also sites of flare activity. The first location produced two large (X-class) flares during the period covered by our observations. The second location had larger magnetic shear than the first but produced only small (M- and C-class) flares during our observations. We study the evolution of the photospheric magnetic field in relation to the large flares in the first location. These flares occurred around the same included polarity and have very similar characteristics (soft X-ray light curves, energies, etc,). However, the whole active region has changed substantially in the period between them. We found several characteristics of the region that appear related to the occurrence of these flares: (1) The flares occurred near regions of large magnetic 'shear' but not at the locations of maximum shear or maximum field. (2) Potential field extrapolations of the observed field suggest that the topology changed, prior to the first of the two flares, in such a way that a null appeared in the coarse magnetic field. (3) This null was located close to both X-class flares and remained in that location for a few days while the two flares were observed. (4) The flaring region has a pattern of vector field and sunspot motions in which material is 'squeezed' along the polarity inversion line. This pattern is very different from that usually associated with shearing arcades, but it is similar to that suggested previously by Fontenia and Davis. The vertical electric currents, inferred from the transverse field, are consistent with this pattern. (5) A major reconfiguration of the longitudinal field and the vertical electric currents occurred just prior to the first of the two flares. Both changes imply substantial variations of the magnetic structure of the region. On the basis of the available

  12. The magnetic evolution of AR 6555 which lead to two impulsive, readily compact, X-type flares

    NASA Technical Reports Server (NTRS)

    Ambastha, A.; Fontenla, J. M.; Kalman, B.; Csepura, GY.

    1995-01-01

    We study the evolution of the vector magnetic field and the sunspot motions observed in AR 6555 during 23-26 Mar. 1991. This region displays two locations of large magnetic shear that were also sites of flare activity. The first location produced two large (X-class) flares during the period covered by our observations. The second location had larger magnetic shear than the first, but produced only small (M- and C-class) flares during our observations. We study the evolution of the photospheric magnetic field in relation to the large flares in the first location. These flares occurred around the same included polarity, and have very similar characteristics (soft X-ray light curves, energies, etc.). However, the whole active region has changed substantially in the period between them. We found several characteristics of the region that appear related to the occurrence of these flares. (1) The flares occurred near regions of large magnetic 'shear,' but not at the locations of maximum shear or maximum field. (2) Potential field extrapolations of the observed field suggest that the topology changed, prior to the first of the two flares, in such a way that a null appeared in the coarse magnetic field. (3) This null was located close to both X-class flares, and remained in that location for a few days while the two flares were observed. (4) The flaring region has a pattern of vector field and sunspot motions in which material is 'squeezed' along the polarity inversion line. This pattern is very different from that usually associated with shearing arcades, but it is similar to that suggested previously by Fontenla and Davis. The vertical electric currents, inferred from the transverse field, are consistent with this pattern. (5) A major reconfiguration of the longitudinal field and the vertical electric currents occurred just prior to the first of the two flares. Both changes imply substantial variations of the magnetic structure of the region. On the basis of the

  13. Slipping Magnetic Reconnection, Chromospheric Evaporation, Implosion, and Precursors in the 2014 September 10 X1.6-Class Solar Flare

    NASA Astrophysics Data System (ADS)

    Dudík, Jaroslav; Polito, Vanessa; Janvier, Miho; Mulay, Sargam M.; Karlický, Marian; Aulanier, Guillaume; Del Zanna, Giulio; Dzifčáková, Elena; Mason, Helen E.; Schmieder, Brigitte

    2016-05-01

    We investigate the occurrence of slipping magnetic reconnection, chromospheric evaporation, and coronal loop dynamics in the 2014 September 10 X-class flare. Slipping reconnection is found to be present throughout the flare from its early phase. Flare loops are seen to slip in opposite directions toward both ends of the ribbons. Velocities of 20–40 km s‑1 are found within time windows where the slipping is well resolved. The warm coronal loops exhibit expanding and contracting motions that are interpreted as displacements due to the growing flux rope that subsequently erupts. This flux rope existed and erupted before the onset of apparent coronal implosion. This indicates that the energy release proceeds by slipping reconnection and not via coronal implosion. The slipping reconnection leads to changes in the geometry of the observed structures at the Interface Region Imaging Spectrograph slit position, from flare loop top to the footpoints in the ribbons. This results in variations of the observed velocities of chromospheric evaporation in the early flare phase. Finally, it is found that the precursor signatures, including localized EUV brightenings as well as nonthermal X-ray emission, are signatures of the flare itself, progressing from the early phase toward the impulsive phase, with the tether-cutting being provided by the slipping reconnection. The dynamics of both the flare and outlying coronal loops is found to be consistent with the predictions of the standard solar flare model in three dimensions.

  14. Magnetic Reconnection in Solar Flares

    NASA Astrophysics Data System (ADS)

    Forbes, Terry G.

    2016-05-01

    Reconnection has at least three possible roles in solar flares: First, it may contribute to the build-up of magnetic energy in the solar corona prior to flare onset; second, it may directly trigger the onset of the flare; and third, it may allow the release of magnetic energy by relaxing the magnetic field configuration to a lower energy state. Although observational support for the first two roles is somewhat limited, there is now ample support for the third. Within the last few years EUV and X-ray instruments have directly observed the kind of plasma flows and heating indicative of reconnection. Continued improvements in instrumentation will greatly help to determine the detailed physics of the reconnection process in the solar atmosphere. Careful measurement of the reconnection outflows will be especially helpful in this regard. Current observations suggest that in some flares the jet outflows are accelerated within a short diffusion region that is more characteristic of Petschek-type reconnection than Sweet-Parker reconnection. Recent resistive MHD theoretical and numerical analyses predict that the length of the diffusion region should be just within the resolution range of current X-ray and EUV telescopes if the resistivity is uniform. On the other hand, if the resistivity is not uniform, the length of the diffusion region could be too short for the outflow acceleration region to be observable.

  15. Solar Flare Aimed at Earth

    NASA Technical Reports Server (NTRS)

    2002-01-01

    At the height of the solar cycle, the Sun is finally displaying some fireworks. This image from the Solar and Heliospheric Observatory (SOHO) shows a large solar flare from June 6, 2000 at 1424 Universal Time (10:24 AM Eastern Daylight Savings Time). Associated with the flare was a coronal mass ejection that sent a wave of fast moving charged particles straight towards Earth. (The image was acquired by the Extreme ultaviolet Imaging Telescope (EIT), one of 12 instruments aboard SOHO) Solar activity affects the Earth in several ways. The particles generated by flares can disrupt satellite communications and interfere with power transmission on the Earth's surface. Earth's climate is tied to the total energy emitted by the sun, cooling when the sun radiates less energy and warming when solar output increases. Solar radiation also produces ozone in the stratosphere, so total ozone levels tend to increase during the solar maximum. For more information about these solar flares and the SOHO mission, see NASA Science News or the SOHO home page. For more about the links between the sun and climate change, see Sunspots and the Solar Max. Image courtesy SOHO Extreme ultaviolet Imaging Telescope, ESA/NASA

  16. Sunspot 1504 is Spitting Flares

    NASA Video Gallery

    This movie from the Solar Dynamics Observatory (SDO) shows the M class flare on June 14, 2012 from 9:15 AM to 2:00 PM EDT. The sun is shown here in teal as this is the color typically used to repre...

  17. A FLARE for the Arts.

    ERIC Educational Resources Information Center

    Aschbacher, Pamela

    1996-01-01

    Although arts programs have been cut from many school budgets, an innovative program in Pasadena, California, is keeping art and artists in classrooms. Project FLARE (Fun with Language, Arts, and Reading) pairs classroom teachers with local artists, who together develop an integrated language and visual arts curriculum. Students also take field…

  18. Chaotic ion motion in magnetosonic plasma waves

    NASA Technical Reports Server (NTRS)

    Varvoglis, H.

    1984-01-01

    The motion of test ions in a magnetosonic plasma wave is considered, and the 'stochasticity threshold' of the wave's amplitude for the onset of chaotic motion is estimated. It is shown that for wave amplitudes above the stochasticity threshold, the evolution of an ion distribution can be described by a diffusion equation with a diffusion coefficient D approximately equal to 1/v. Possible applications of this process to ion acceleration in flares and ion beam thermalization are discussed.

  19. Slipping Magnetic Reconnection of Flux-rope Structures as a Precursor to an Eruptive X-class Solar Flare

    NASA Astrophysics Data System (ADS)

    Li, Ting; Yang, Kai; Hou, Yijun; Zhang, Jun

    2016-10-01

    We present the quasi-periodic slipping motion of flux-rope structures prior to the onset of an eruptive X-class flare on 2015 March 11, obtained by the Interface Region Imaging Spectrograph and the Solar Dynamics Observatory. The slipping motion occurred at the north part of the flux rope and seemed to successively peel off the flux rope. The speed of the slippage was 30‑40 km s‑1, with an average period of 130 ± 30 s. The Si iv λ1402.77 line showed a redshift of 10‑30 km s‑1 and a line width of 50‑120 km s‑1 at the west legs of slipping structures, indicative of reconnection downflow. The slipping motion lasted about 40 minutes, and the flux rope started to rise up slowly at the late stage of the slippage. Then an X2.1 flare was initiated, and the flux rope was impulsively accelerated. One of the flare ribbons swept across a negative-polarity sunspot, and the penumbral segments of the sunspot decayed rapidly after the flare. We studied the magnetic topology at the flaring region, and the results showed the existence of a twisted flux rope, together with quasi-separatrix layer (QSL) structures binding the flux rope. Our observations imply that quasi-periodic slipping magnetic reconnection occurs along the flux-rope-related QSLs in the preflare stage, which drives the later eruption of the flux rope and the associated flare.

  20. KEPLER FLARES. II. THE TEMPORAL MORPHOLOGY OF WHITE-LIGHT FLARES ON GJ 1243

    SciTech Connect

    Davenport, James R. A.; Hawley, Suzanne L.; Johnson, Emily C.; Peraza, Jesus; Jansen, Tiffany C.; Larsen, Daniel M.; Hebb, Leslie; Wisniewski, John P.; Malatesta, Michael; Keil, Marcus; Silverberg, Steven M.; Scheffler, Matthew S.; Berdis, Jodi R.; Kowalski, Adam F.; Hilton, Eric J.

    2014-12-20

    We present the largest sample of flares ever compiled for a single M dwarf, the active M4 star GJ 1243. Over 6100 individual flare events, with energies ranging from 10{sup 29} to 10{sup 33} erg, are found in 11 months of 1 minute cadence data from Kepler. This sample is unique for its completeness and dynamic range. We have developed automated tools for finding flares in short-cadence Kepler light curves, and performed extensive validation and classification of the sample by eye. From this pristine sample of flares we generate a median flare template. This template shows that two exponential cooling phases are present during the white-light flare decay, providing fundamental constraints for models of flare physics. The template is also used as a basis function to decompose complex multi-peaked flares, allowing us to study the energy distribution of these events. Only a small number of flare events are not well fit by our template. We find that complex, multi-peaked flares occur in over 80% of flares with a duration of 50 minutes or greater. The underlying distribution of flare durations for events 10 minutes and longer appears to follow a broken power law. Our results support the idea that sympathetic flaring may be responsible for some complex flare events.

  1. Statistical study of spatio-temporal distribution of precursor solar flares associated with major flares

    NASA Astrophysics Data System (ADS)

    Gyenge, N.; Ballai, I.; Baranyi, T.

    2016-07-01

    The aim of the present investigation is to study the spatio-temporal distribution of precursor flares during the 24 h interval preceding M- and X-class major flares and the evolution of follower flares. Information on associated (precursor and follower) flares is provided by Reuven Ramaty High Energy Solar Spectroscopic Imager (RHESSI). Flare list, while the major flares are observed by the Geostationary Operational Environmental Satellite (GOES) system satellites between 2002 and 2014. There are distinct evolutionary differences between the spatio-temporal distributions of associated flares in about one-day period depending on the type of the main flare. The spatial distribution was characterized by the normalized frequency distribution of the quantity δ (the distance between the major flare and its precursor flare normalized by the sunspot group diameter) in four 6 h time intervals before the major event. The precursors of X-class flares have a double-peaked spatial distribution for more than half a day prior to the major flare, but it changes to a lognormal-like distribution roughly 6 h prior to the event. The precursors of M-class flares show lognormal-like distribution in each 6 h subinterval. The most frequent sites of the precursors in the active region are within a distance of about 0.1 diameter of sunspot group from the site of the major flare in each case. Our investigation shows that the build-up of energy is more effective than the release of energy because of precursors.

  2. Acceleration of solar cosmic rays in a flare current sheet and their propagation in interplanetary space

    NASA Astrophysics Data System (ADS)

    Podgorny, A. I.; Podgorny, I. M.

    2015-09-01

    Analyses of GOES spacecraft data show that the prompt component of high-energy protons arrive at the Earth after a time corresponding to their generation in flares in the western part of the solar disk, while the delayed component is detected several hours later. All protons in flares are accelerated by a single mechanism. The particles of the prompt component propagate along magnetic lines of the Archimedean spiral connectng the flare with the Earth. The prompt component generated by flares in the eastern part of the solar disk is not observed at the Earth, since particles accelerated by these flares do not intersect magnetic-field lines connecting the flare with the Earth. These particles arrive at the Earth via their motion across the interplanetary magnetic field. These particles are trapped by the magnetic field and transported by the solar wind, since the interplanetary magnetic field is frozen in the wind plasma, and these particles also diffuse across the field. The duration of the delay reaches several days.

  3. Rotating eruption of an untwisting filament triggered by the 3B flare of 25 April, 1984

    NASA Astrophysics Data System (ADS)

    Kurokawa, Hiroki; Hanaoka, Yoichiro; Shibata, Kazunari; Uchida, Yutaka

    1987-09-01

    A great 3B flare, whose X-ray class was X13, occurred over a delta-sunspot at 00:01 UT on April 25, 1984. Before the flare, a strong magnetic shear was found to be formed along the neutral line in the delta-sunspot with shear motions of umbrae. The shear motions of the umbrae were caused by the successive emergence of a magnetic flux rope. Before the flare, several groups of sheared H-alpha threads and filaments were found to merge into an elongated filament along the neutral line through the delta-sunspot. In the merging process the helical twists were formed in the filament by the reconnection as in Pneuman's (1983) model. At the post-maximum phase of the flare, the helically twisted filament spouted out with an untwisting rotation. Examining the morphological and dynamical features of the filament eruption, it is concluded that it has some typical features of the flare spray, and that it seems to be accelerated by the sweeping-magnetic-twist mechanism proposed by Shibata and Uchida (1986).

  4. Flare-antenna unit for system in which flare is remotely activated by radio

    NASA Astrophysics Data System (ADS)

    Hiltz, Frederick F.; Wilson, Charles E.

    1995-06-01

    A flare-antenna assembly has flare material enclosed in a cylindrical antenna and forms part of a marker beacon. The flare aids in the search for the marker beacon by providing means for both visual and infrared detection. The flare is actuated in response to a specific remote radio signal being received by the antenna. The received signal is decoded by the electronic system within the marker beacon. If the received signal meets the necessary criteria the electronic system generates an electrical signal that detonates a squib embedded in the flare material. The detonation of the squib activates the flare.

  5. Magnetic Evolution of Super-Active Region NOAA AR 10486 and the Large 4B/X17.2 Class Flare Observed During Octbober 28, 2003

    NASA Astrophysics Data System (ADS)

    Ambastha, Ashok

    2005-09-01

    Extensive flare activity was observed in super-active region NOAA10486 during its disk passage of October 22-November 04, 2003. An extremely energetic 4B/X17.2 flare on October 28, 2003/11:10 UT was observed from USO when the active region was located at S16E08, i.e., close to the disk-centre. This flare was rated the third largest X-ray flare recorded by GOES satellite, and the largest in the optical class (4B) observed so far from USO. Chromospheric H-alpha filtergrams were obtained before, during and in the decay phase of the two-ribbon flare at a cadence of 3-4 seconds. The temporal and spatial structure evolution was analyzed with the help of a movie constructed using more than 4000 images. Magnetograms from NASA-MSFC showed large magnetic shear around the flare site which was delineated by a large active filament. The filament erupted as the flare progressed. In the decay phase of the flare, a system of post-flare loops developed at the site of the erupted filament. Observation from TRACE also exhibited these loop structures. Associated with this flare, a fast Earthward moving halo CME was also detected by SOHO, which initiated a major geomagnetic storm on October 29, 2003 at 06:13 UT, i.e., within a record time of 19 hours after the flare. This large flare was followed by another 2B/X11 event on October 29, 2003/20:49 UT, not observed from USO as it occurred in our night-time. We have used white light full disk images and line-of-sight magnetograms obtained from SOHO-MDI for determination of proper motion of the main sunspots and corresponding magnetic fluxes in order to understand rapid magnetic energy build-up in the active region, giving rise to the two large flares within such a short time.

  6. MAGNETIC STRUCTURE PRODUCING X- AND M-CLASS SOLAR FLARES IN SOLAR ACTIVE REGION 11158

    SciTech Connect

    Inoue, S.; Magara, T.; Choe, G. S.; Hayashi, K.; Shiota, D.

    2013-06-10

    We study the three-dimensional magnetic structure of the solar active region 11158, which produced one X-class and several M-class flares on 2011 February 13-16. We focus on the magnetic twist in four flare events, M6.6, X2.2, M1.0, and M1.1. The magnetic twist is estimated from the nonlinear force-free field extrapolated from the vector fields obtained from the Helioseismic and Magnetic Imager on board the Solar Dynamic Observatory using the magnetohydrodynamic relaxation method developed by Inoue et al. We found that strongly twisted lines ranging from half-turn to one-turn twists were built up just before the M6.6 and X2.2 flares and disappeared after that. Because most of the twists remaining after these flares were less than a half-turn twist, this result suggests that the buildup of magnetic twist over the half-turn twist is a key process in the production of large flares. On the other hand, even though these strong twists were also built up just before the M1.0 and M1.1 flares, most of them remained afterward. Careful topological analysis before the M1.0 and M1.1 flares shows that the strongly twisted lines were surrounded mostly by the weakly twisted lines formed in accordance with the clockwise motion of the positive sunspot, whose footpoints are rooted in strong magnetic flux regions. These results imply that these weakly twisted lines might suppress the activity of the strongly twisted lines in the last two M-class flares.

  7. The Kepler Catalog of Stellar Flares

    NASA Astrophysics Data System (ADS)

    Davenport, James R. A.

    2016-09-01

    A homogeneous search for stellar flares has been performed using every available Kepler light curve. An iterative light curve de-trending approach was used to filter out both astrophysical and systematic variability to detect flares. The flare recovery completeness has also been computed throughout each light curve using artificial flare injection tests, and the tools for this work have been made publicly available. The final sample contains 851,168 candidate flare events recovered above the 68% completeness threshold, which were detected from 4041 stars, or 1.9% of the stars in the Kepler database. The average flare energy detected is ˜1035 erg. The net fraction of flare stars increases with g - i color, or decreasing stellar mass. For stars in this sample with previously measured rotation periods, the total relative flare luminosity is compared to the Rossby number. A tentative detection of flare activity saturation for low-mass stars with rapid rotation below a Rossby number of ˜0.03 is found. A power-law decay in flare activity with Rossby number is found with a slope of -1, shallower than typical measurements for X-ray activity decay with Rossby number.

  8. The Effects of Flare Definitions on the Statistics of Derived Flare Distrubtions

    NASA Astrophysics Data System (ADS)

    Ryan, Daniel; Dominique, Marie; Seaton, Daniel B.; Stegen, Koen; White, Arthur

    2016-05-01

    The statistical examination of solar flares is crucial to revealing their global characteristics and behaviour. However, statistical flare studies are often performed using standard but basic flare detection algorithms relying on arbitrary thresholds which may affect the derived flare distributions. We explore the effect of the arbitrary thresholds used in the GOES event list and LYRA Flare Finder algorithms. We find that there is a small but significant relationship between the power law exponent of the GOES flare peak flux frequency distribution and the algorithms’ flare start thresholds. We also find that the power law exponents of these distributions are not stable but appear to steepen with increasing peak flux. This implies that the observed flare size distribution may not be a power law at all. We show that depending on the true value of the exponent of the flare size distribution, this deviation from a power law may be due to flares missed by the flare detection algorithms. However, it is not possible determine the true exponent from GOES/XRS observations. Additionally we find that the PROBA2/LYRA flare size distributions are clearly non-power law. We show that this is consistent with an insufficient degradation correction which causes LYRA absolute irradiance values to be unreliable. This means that they should not be used for flare statistics or energetics unless degradation is adequately accounted for. However they can be used to study time variations over shorter timescales and for space weather monitoring.

  9. Modelling the influence of photospheric turbulence on solar flare statistics.

    PubMed

    Mendoza, M; Kaydul, A; de Arcangelis, L; Andrade, J S; Herrmann, H J

    2014-01-01

    Solar flares stem from the reconnection of twisted magnetic field lines in the solar photosphere. The energy and waiting time distributions of these events follow complex patterns that have been carefully considered in the past and that bear some resemblance with earthquakes and stockmarkets. Here we explore in detail the tangling motion of interacting flux tubes anchored in the plasma and the energy ejections resulting when they recombine. The mechanism for energy accumulation and release in the flow is reminiscent of self-organized criticality. From this model, we suggest the origin for two important and widely studied properties of solar flare statistics, including the time-energy correlations. We first propose that the scale-free energy distribution of solar flares is largely due to the twist exerted by the vorticity of the turbulent photosphere. Second, the long-range temporal and time-energy correlations appear to arise from the tube-tube interactions. The agreement with satellite measurements is encouraging. PMID:25247788

  10. Helium (3) Rich Solar Flares

    DOE R&D Accomplishments Database

    Colgate, S. A.; Audouze, J.; Fowler, W. A.

    1977-05-03

    The extreme enrichment of {sup 3} He {sup 4} He greater than or equal to 1 in some solar flares as due to spallation and the subsequent confinement of the products in a high temperature, kT approx. = 200 keV, high density, n{sub e} approx. = 3 x 10{sup 15} cm {sup -3} plasma associated with the magnetic instability producing the flare is interpreted. The pinch or filament is a current of high energy protons that creates the spallation and maintains the temperature that produces the high energy x-ray spectrum and depletes other isotopes D, Li, Be, and B as observed. Finally the high temperature plasma is a uniquely efficient spallation target that is powered by the interaction of stellar convection and self generated magnetic field.

  11. Particle Acceleration in Solar Flares

    NASA Astrophysics Data System (ADS)

    Petrosian, V.

    Several new observations notably high spatial and spectral X-ray observations of impulsive phase of solar flares by YOHKOH and RHESSI, and Solar Energetic Particle (SEP) spectra by ACE have provided strong evidence in favor of stochastic acceleration of electrons, protons and other ions by plasma waves or turbulence. Theoretical arguments also favor such a model if the seed particles come from the background thermal plasma. I will describe these evidences and the theoretical framework for evaluation of the accelerated particle spectra, their transport and radiation. The predictions of the models will be compared with several features of the observations with specific emphasize on heating vs acceleration by turbulence, thermal vs nonthermal electron spectra, looptop vs footpoint emission fro flaring loops, electron vs proton acceleration rates and 3He vs 4He (and other ion) abundances in SEPs.

  12. Millimeter to X-ray flares from Sagittarius A*

    NASA Astrophysics Data System (ADS)

    Eckart, A.; García-Marín, M.; Vogel, S. N.; Teuben, P.; Morris, M. R.; Baganoff, F.; Dexter, J.; Schödel, R.; Witzel, G.; Valencia-S., M.; Karas, V.; Kunneriath, D.; Straubmeier, C.; Moser, L.; Sabha, N.; Buchholz, R.; Zamaninasab, M.; Mužić, K.; Moultaka, J.; Zensus, J. A.

    2012-01-01

    Context. We report on new simultaneous observations and modeling of the millimeter, near-infrared, and X-ray flare emission of the source Sagittarius A* (SgrA*) associated with the super-massive (4 × 106 M⊙) black hole at the Galactic center. Aims: We study the applicability of the adiabatic synchrotron source expansion model and study physical processes giving rise to the variable emission of SgrA* from the radio to the X-ray domain. Methods: Our observations were carried out on 18 May 2009 using the NACO adaptive optics (AO) instrument at the European Southern Observatory's Very Large Telescope, the ACIS-I instrument aboard the Chandra X-ray Observatory, the LABOCA bolometer at the Atacama Pathfinder EXperiment (APEX), and the CARMA mm telescope array at Cedar Flat, California. Results: The X-ray flare had an excess 2 - 8 keV luminosity between 6 and 12 × 1033 erg s-1. The observations reveal flaring activity in all wavelength bands that can be modeled as the signal from an adiabatically expanding synchrotron self-Compton (SSC) component. Modeling of the light curves shows that the sub-mm follows the NIR emission with a delay of about three-quarters of an hour with an expansion velocity of about vexp ~ 0.009c. We find source component sizes of around one Schwarzschild radius, flux densities of a few Janskys, and spectral indices α of about +1 (S(ν) ∝ ν-α). At the start of the flare, the spectra of the two main components peak just short of 1 THz. To statistically explain the observed variability of the (sub-)mm spectrum of SgrA*, we use a sample of simultaneous NIR/X-ray flare peaks and model the flares using a synchrotron and SSC mechanism. Conclusions: These parameters suggest that either the adiabatically expanding source components have a bulk motion larger than vexp or the expanding material contributes to a corona or disk, confined to the immediate surroundings of SgrA*. For the bulk of the synchrotron and SSC models, we find synchrotron turnover

  13. FlareLab: early results

    NASA Astrophysics Data System (ADS)

    Soltwisch, H.; Kempkes, P.; Mackel, F.; Stein, H.; Tenfelde, J.; Arnold, L.; Dreher, J.; Grauer, R.

    2010-12-01

    The FlareLab experiment at Bochum University has been constructed to generate and investigate plasma-filled magnetic flux tubes similar to arch-shaped solar prominences, which often result in coronal mass ejections (CMEs). In its first version, the device has been used to reproduce and extend previous studies of Bellan et al (1998 Phys. Plasmas 5 1991). Here the plasma source consists of two electrodes, which can be connected to a 1.0 kJ capacitor bank, and of a horseshoe magnet, which provides an arch-shaped guiding field. The discharge is ignited in a cloud of hydrogen gas that has been puffed into the space above the electrodes. In the first few microseconds the plasma current rises at a rate of several kA µs-1, causing the plasma column to pinch along the guiding B-field and to form an expanding loop structure. The observed dynamics of the magnetic flux tubes is analysed by means of three-dimensional MHD simulations in order to determine the influence of parameters like the initial magnetic field geometry on magnetic stability. At present, FlareLab is redesigned to mimic a model that was proposed by Titov and Démoulin (1999 Astron. Astrophys. 351 707) to investigate twisted magnetic configurations in solar flares.

  14. Electron acceleration in solar flares

    NASA Technical Reports Server (NTRS)

    Droge, Wolfgang; Meyer, Peter; Evenson, Paul; Moses, Dan

    1989-01-01

    For the period Spetember 1978 to December 1982, 55 solar flare particle events for which the instruments on board the ISEE-3 spacecraft detected electrons above 10 MeV. Combining data with those from the ULEWAT spectrometer electron spectra in the range from 0.1 to 100 MeV were obtained. The observed spectral shapes can be divided into two classes. The spectra of the one class can be fit by a single power law in rigidity over the entire observed range. The spectra of the other class deviate from a power law, instead exhibiting a steepening at low rigidities and a flattening at high rigidities. Events with power-law spectra are associated with impulsive (less than 1 hr duration) soft X-ray emission, whereas events with hardening spectra are associated with long-duration (more than 1 hr) soft X-ray emission. The characteristics of long-duration events are consistent with diffusive shock acceleration taking place high in the corona. Electron spectra of short-duration flares are well reproduced by the distribution functions derived from a model assuming simultaneous second-order Fermi acceleration and Coulomb losses operating in closed flare loops.

  15. Modeling Repeatedly Flaring δ Sunspots.

    PubMed

    Chatterjee, Piyali; Hansteen, Viggo; Carlsson, Mats

    2016-03-11

    Active regions (ARs) appearing on the surface of the Sun are classified into α, β, γ, and δ by the rules of the Mount Wilson Observatory, California on the basis of their topological complexity. Amongst these, the δ sunspots are known to be superactive and produce the most x-ray flares. Here, we present results from a simulation of the Sun by mimicking the upper layers and the corona, but starting at a more primitive stage than any earlier treatment. We find that this initial state consisting of only a thin subphotospheric magnetic sheet breaks into multiple flux tubes which evolve into a colliding-merging system of spots of opposite polarity upon surface emergence, similar to those often seen on the Sun. The simulation goes on to produce many exotic δ sunspot associated phenomena: repeated flaring in the range of typical solar flare energy release and ejective helical flux ropes with embedded cool-dense plasma filaments resembling solar coronal mass ejections.

  16. Solar flares and energetic particles.

    PubMed

    Vilmer, Nicole

    2012-07-13

    Solar flares are now observed at all wavelengths from γ-rays to decametre radio waves. They are commonly associated with efficient production of energetic particles at all energies. These particles play a major role in the active Sun because they contain a large amount of the energy released during flares. Energetic electrons and ions interact with the solar atmosphere and produce high-energy X-rays and γ-rays. Energetic particles can also escape to the corona and interplanetary medium, produce radio emissions (electrons) and may eventually reach the Earth's orbit. I shall review here the available information on energetic particles provided by X-ray/γ-ray observations, with particular emphasis on the results obtained recently by the mission Reuven Ramaty High-Energy Solar Spectroscopic Imager. I shall also illustrate how radio observations contribute to our understanding of the electron acceleration sites and to our knowledge on the origin and propagation of energetic particles in the interplanetary medium. I shall finally briefly review some recent progress in the theories of particle acceleration in solar flares and comment on the still challenging issue of connecting particle acceleration processes to the topology of the complex magnetic structures present in the corona.

  17. Characteristics of gamma-ray line flares

    NASA Technical Reports Server (NTRS)

    Bai, T.; Dennis, B.

    1983-01-01

    Observations of solar gamma rays by the Solar Maximum Mission (SMM) demonstrate that energetic protons and ions are rapidly accelerated during the impulsive phase. To understand the acceleration mechanisms for these particles, the characteristics of the gamma ray line flares observed by SMM were studied. Some very intense hard X-ray flares without detectable gamma ray lines were also investigated. Gamma ray line flares are distinguished from other flares by: (1) intense hard X-ray and microwave emissions; (2) delay of high energy hard X-rays; (3) emission of type 2 and/or type 4 radio bursts; and (4) flat hard X-ray spectra (average power law index: 3.1). The majority of the gamma ray line flares shared all these characteristics, and the remainder shared at least three of them. Positive correlations were found between durations of spike bursts and spatial sizes of flare loops as well as between delay times and durations of spike bursts.

  18. Pre-flare dynamics of sunspot groups

    SciTech Connect

    Korsós, M. B.; Baranyi, T.; Ludmány, A. E-mail: baranyi.tunde@csfk.mta.hu

    2014-07-10

    Several papers provide evidence that the most probable sites of flare onset are the regions of high horizontal magnetic field gradients in solar active regions. Besides the localization of flare-producing areas, this work intends to reveal the characteristic temporal variations in these regions prior to flares. This study uses sunspot data instead of magnetograms and follows the behavior of a suitable defined proxy measure representing the horizontal magnetic field gradient. The source of the data is the SDD (SOHO/MDI-Debrecen Data) sunspot catalog. The most promising pre-flare signatures are the following properties of gradient variation: (1) steep increase, (2) high maximum, (3) significant fluctuation, and (4) a gradual decrease between the maximum and the flare onset that can be related to the 'pull mode' of the current layer. These properties may yield a tool for the assessment of flare probability and intensity within the following 8-10 hr.

  19. Motion Sickness

    MedlinePlus

    ... people traveling by car, train, airplanes and especially boats. Motion sickness can start suddenly, with a queasy ... motion sickness. For example, down below on a boat, your inner ear senses motion, but your eyes ...

  20. Properties of the 15 February 2011 Flare Seismic Sources

    NASA Astrophysics Data System (ADS)

    Zharkov, S.; Green, L. M.; Matthews, S. A.; Zharkova, V. V.

    2013-06-01

    The first near-side X-class flare of Solar Cycle 24 occurred in February 2011 (SOL2011-02-05T01:55) and produced a very strong seismic response in the photosphere. One sunquake was reported by Kosovichev ( Astrophys. J. Lett. 734, L15, 2011), followed by the discovery of a second sunquake by Zharkov, Green, Matthews et al. ( Astrophys. J. Lett. 741, L35, 2011). The flare had a two-ribbon structure and was associated with a flux-rope eruption and a halo coronal mass ejection (CME) as reported in the CACTus catalogue. Following the discovery of the second sunquake and the spatial association of both sources with the locations of the feet of the erupting flux rope (Zharkov, Green, Matthews et al., Astrophys. J. Lett. 741, L35, 2011), we present here a more detailed analysis of the observed photospheric changes in and around the seismic sources. These sunquakes are quite unusual, taking place early in the impulsive stage of the flare, with the seismic sources showing little hard X-ray (HXR) emission, and strongest X-ray emission sources located in the flare ribbons. We present a directional time-distance diagram computed for the second source, which clearly shows a ridge corresponding to the travelling acoustic-wave packet and find that the sunquake at the second source happened about 45 seconds to one minute earlier than the first source. Using acoustic holography we report different frequency responses of the two sources. We find strong downflows at both seismic locations and a supersonic horizontal motion at the second site of acoustic-wave excitation.

  1. Interplanetary shock waves associated with solar flares

    NASA Technical Reports Server (NTRS)

    Chao, J. K.; Sakurai, K.

    1974-01-01

    The interaction of the earth's magnetic field with the solar wind is discussed with emphasis on the influence of solar flares. The geomagnetic storms are considerered to be the result of the arrival of shock wave generated by solar flares in interplanetary space. Basic processes in the solar atmosphere and interplanetary space, and hydromagnetic disturbances associated with the solar flares are discussed along with observational and theoretical problems of interplanetary shock waves. The origin of interplanetary shock waves is also discussed.

  2. Densities of Stellar Flares from Spectral Lines

    NASA Astrophysics Data System (ADS)

    Mitra-Kraev, U.

    2006-08-01

    We present detailed analyses of spectral changes during X-ray flares. During flares the plasma is known to become hotter, but also changes in density are anticipated, as flares will rather be compact and dense than large and tenuous. We search for indications of changes in density in the spectra of Chandra High Energy Transmission Grating Spectrometer (HETGS) data. However, as flares usually last for at most up to one hour, only very bright flares will produce enough photons for a sufficiently well exposed spectrum. We chose long Chandra observations of flare stars which covered periods of time with flare activity that can be combined to compile one quiescent-only spectrum to be compared with a spectrum that is affected by flare activity. We show that with careful data analysis it is possible with the presently available instruments to detect spectral line changes between quiescent and flaring states, notably in the density- and temperature-sensitive lines of the He-like OVII triplet (21.6/21.8/22.1 A). Using cumulative distribution functions, we are also able to give solid statistical confidence limits. We also briefly discuss the diagnostic capabilities of other He-like line triplets and of observations carried out with the XMM-Newton Reflection Grating Spectrometer (RGS).

  3. Determining the flare dispensing program effectiveness against conical-scan and spin-scan reticle systems via Gaussian mixture models

    NASA Astrophysics Data System (ADS)

    Şahingil, Mehmet C.; Aslan, Murat Ş.

    2013-05-01

    The reticle systems which are considered as the classical approach for determining the angular position of radiating targets in infrared band are widely used in early generation surface-to-air and air-to-air infrared guided missile seekers. One of the cost-effective ways of protecting aircrafts against these missiles is to dispense flare decoys from the countermeasure dispensing system (CMDS) integrated into the aircraft platform. Although this counter-measuring technique seems very simple, if not optimized carefully, it may not be effective for protecting the aircraft. Flares should be dispensed in accordance with a specific dispensing program which determines the number of flares to be dispensed from each dispenser of the CMDS and timing sequence of dispensing. Optimizing the parameters of the dispensing program is not trivial. It requires a good understanding of the operating principle of the threat seeker, operational capabilities of own platform and engagement scenario between them. In the present paper, we propose a complete simulation-based procedure to form an effectiveness boundary of flare dispensing programs against the spin-scan and conical-scan reticle seekers. The region of effectiveness is determined via Gaussian mixture models. The raw data is collected via extensive number of simulations using a MATLAB-coded simulator which models reticle-based seeker, aircraft radiation, aircraft motion, aircraft CMDS system, flare motion and flare radiation.

  4. Dynamics of intrinsic axial flows in unsheared, uniform magnetic fields

    NASA Astrophysics Data System (ADS)

    Li, J. C.; Diamond, P. H.; Xu, X. Q.; Tynan, G. R.

    2016-05-01

    A simple model for the generation and amplification of intrinsic axial flow in a linear device, controlled shear decorrelation experiment, is proposed. This model proposes and builds upon a novel dynamical symmetry breaking mechanism, using a simple theory of drift wave turbulence in the presence of axial flow shear. This mechanism does not require complex magnetic field structure, such as shear, and thus is also applicable to intrinsic rotation generation in tokamaks at weak or zero magnetic shear, as well as to linear devices. This mechanism is essentially the self-amplification of the mean axial flow profile, i.e., a modulational instability. Hence, the flow development is a form of negative viscosity phenomenon. Unlike conventional mechanisms where the residual stress produces an intrinsic torque, in this dynamical symmetry breaking scheme, the residual stress induces a negative increment to the ambient turbulent viscosity. The axial flow shear is then amplified by this negative viscosity increment. The resulting mean axial flow profile is calculated and discussed by analogy with the problem of turbulent pipe flow. For tokamaks, the negative viscosity is not needed to generate intrinsic rotation. However, toroidal rotation profile gradient is enhanced by the negative increment in turbulent viscosity.

  5. GAMMA-RAY ACTIVITY IN THE CRAB NEBULA: THE EXCEPTIONAL FLARE OF 2011 APRIL

    SciTech Connect

    Buehler, R.; Blandford, R. D.; Charles, E.; Chiang, J.; Funk, S.; Kerr, M.; Massaro, F.; Romani, R. W.; Scargle, J. D.; Baldini, L.; Baring, M. G.; Belfiore, A.; Saz Parkinson, P. M.; D'Ammando, F.; Dermer, C. D.; Grove, J. E.; Harding, A. K.; Hays, E.; Mazziotta, M. N.; Tennant, A. F. E-mail: rdb3@stanford.edu; and others

    2012-04-10

    The Large Area Telescope on board the Fermi satellite observed a gamma-ray flare in the Crab Nebula lasting for approximately nine days in April of 2011. The source, which at optical wavelengths has a size of Almost-Equal-To 11 lt-yr across, doubled its gamma-ray flux within eight hours. The peak photon flux was (186 {+-} 6) Multiplication-Sign 10{sup -7} cm{sup -2} s{sup -1} above 100 MeV, which corresponds to a 30-fold increase compared to the average value. During the flare, a new component emerged in the spectral energy distribution, which peaked at an energy of (375 {+-} 26) MeV at flare maximum. The observations imply that the emission region was likely relativistically beamed toward us and that variations in its motion are responsible for the observed spectral variability.

  6. Observation of the Evolution of a Current Sheet in a Solar Flare

    NASA Astrophysics Data System (ADS)

    Zhu, Chunming; Liu, Rui; Alexander, David; McAteer, R. T. James

    2016-04-01

    We report multi-wavelength and multi-viewpoint observations of a solar eruptive event that involves loop–loop interactions. During a C2.0 flare, motions associated with inflowing and outflowing plasma provide evidence for ongoing magnetic reconnection. The flare loop top and a rising “concave-up” feature are connected by a current-sheet-like structure (CSLS). The physical properties (thickness, length, temperature, and density) of the CSLS are evaluated. In regions adjacent to the CSLS, the EUV emission (characteristic temperature at 1.6 MK) begins to increase more than 10 minutes prior to the onset of the flare, and steeply decreases during the decay phase. The reduction of the emission resembles that expected from coronal dimming. The dynamics of this event imply a magnetic reconnection rate in the range 0.01–0.05.

  7. Observation of the Evolution of a Current Sheet in a Solar Flare

    NASA Astrophysics Data System (ADS)

    Zhu, Chunming; Liu, Rui; Alexander, David; McAteer, James

    2016-05-01

    We report multi-wavelength and multi-viewpoint observations of a solar eruptive event which involves loop-loop interactions. During a C2.0 flare, motions associated with inflowing and outflowing plasma provide evidence for ongoing magnetic reconnection. The flare loop top and a rising "concave-up" feature are connected by a current-sheet-like structure (CSLS). The physical properties (thickness, length, temperature, and density) of the CSLS are evaluated. In regions adjacent to the CSLS, the EUV emission (characteristic temperature at 1.6 MK) begins to increase more than ten minutes prior to the onset of the flare, and steeply decreases during the decay phase. The reduction of the emission resembles that expected from coronal dimming. The dynamics of this event imply a magnetic reconnection rate in the range 0.01--0.05.

  8. Gamma-Ray Activity in the Crab Nebula: The Exceptional Flare of April 2011

    NASA Technical Reports Server (NTRS)

    Buehler, R.; Scargle, J. D.; Blandford, R. D.; Baldini, L; Baring, M. G.; Belfiore, A.; Charles, E.; Chiang, J.; DAmmando, F.; Dermer, C. D.; Funk, S,; Grove, J. E.; Harding, A. K.; Hays, E.; Kerr, M.; Massaro, F.; Mazziotta, M. N.; Romani, R. W.; SazParkinson, P, M.; Tennant, A. F.; Weisskopf, M. C.

    2012-01-01

    The Large Area Telescope on board the Fermi satellite observed a gamma-ray flare in the Crab nebula lasting for approximately nine days in April of 2011. The source, which at optical wavelengths has a size of approximately 11 ly across, doubled its gamma-ray flux within eight hours. The peak photon flux was (186 +/- 6) x 10(exp -7) /square cm/s above 100 MeV, which corresponds to a 30-fold increase compared to the average value. During the flare, a new component emerged in the spectral energy distribution, which peaked at an energy of (375 +/- 26) MeV at flare maximum. The observations imply that the emission region was relativistically beamed toward us and that variations in its motion are responsible for the observed spectral variability.

  9. Exceptions to the rule: the X-flares of AR 2192 Lacking Coronal Mass Ejections

    NASA Astrophysics Data System (ADS)

    Thalmann, J. K.; Su, Y.; Temmer, M.; Veronig, A. M.

    2016-04-01

    NOAA Active region (AR) 2192, that was present on the Sun in October 2014, was the largest region which occurred since November 1990 (see Figure 1). The huge size accompanied by a very high activity level, was quite unexpected as it appeared during the unusually weak solar cycle 24. Nevertheless, the AR turned out to be one of the most prolific flaring ARs of cycle 24. It produced in total 6 X, 29 M, 79 C flares during its disk passage from October 18-29, 2014 (see Figure 2). Surprisingly, all flares greater than GOES class M5 and X were confined, i.e. had no coronal mass ejections (CME) associated. All the flare events had some obvious similarity in morphology, as they were located in the core of the AR and revealed only minor separation motion away from the neutral line but a large initial separation of the conjugate flare ribbons. In the paper by Thalmann et al. (2015) we describe the series of flares and give details about the confined X1.6 flare event from October 22, 2014 as well as the single eruptive M4.0 flare event from October 24, 2014. The study of the X1.6 flare revealed a large initial separation of flare ribbons together with recurrent flare brightenings, which were related to two episodes of enhanced hard X-ray emission as derived from RHESSI observations. This suggests that magnetic field structures connected to specific regions were repeatedly involved in the process of reconnection and energy release. Opposite to the central location of the sequence of confined events within the AR, a single eruptive (M4.0) event occurred on the outskirt of the AR in the vicinity of open magnetic fields. Our investigations revealed a predominantly north-south oriented magnetic system of arcade fields overlying the AR that could have preserved the magnetic arcade to erupt, and consequently kept the energy release trapped in a localized volume of magnetic field high up in the corona (as supported by the absence of a lateral motion of the flare ribbons and the

  10. HARD X-RAY AND ULTRAVIOLET EMISSION DURING THE 2011 JUNE 7 SOLAR FLARE

    SciTech Connect

    Inglis, A. R.; Gilbert, H. R.

    2013-11-01

    The relationship between X-ray and UV emission during flares, particularly in the context of quasi-periodic pulsations, remains unclear. To address this, we study the impulsive X-ray and UV emission during an eruptive flare on 2011 June 7 utilizing X-ray imaging from RHESSI and UV 1700 Å imaging from SDO/AIA. This event is associated with quasi-periodic pulsations in X-ray and possibly UV emission, as well as substantial parallel and perpendicular motion in the hard X-ray footpoints. The motion of the footpoints parallel to the flare ribbons is unusual; it reverses direction on at least two occasions. However, there is no associated short timescale motion of the UV bright regions. Over the same time interval, the footpoints also gradually move apart at v ≈ 12 km s{sup –1}, consistent with the gradual outward expansion of the UV ribbons and the standard flare model. Additionally, we find that the locations of the brightest X-ray and UV regions are different, particularly during the early portion of the flare impulsive phase, despite their integrated emission being strongly correlated in time. Correlation analysis of measured flare properties, such as the footpoint separation, flare shear, photospheric magnetic field, and coronal reconnection rate, reveals that—in the impulsive phase—the 25-50 keV hard X-ray flux is only weakly correlated with these properties, in contrast with previous studies. We characterize this event in terms of long-term behavior, where the X-ray non-thermal, thermal, and UV emission sources appear temporally and spatially consistent, and short-term behavior, where the emission sources are inconsistent and quasi-periodic pulsations are a dominant feature requiring explanation. We suggest that the short timescale behavior of hard X-ray footpoints and the nature of the observed quasi-periodic pulsations are determined by fundamental, as yet unobserved properties of the reconnection region and particle acceleration sites. This presents a

  11. Perimenstrual Flare of Adult Acne

    PubMed Central

    Geller, Lauren; Rosen, Jamie; Frankel, Amylynne; Goldenberg, Gary

    2014-01-01

    Background: Acne is typically regarded as an adolescent disease. A significant body of literature suggests a post-adolescent or adult form of acne. Female patients are known to experience perimenstrual acne flares, the exact prevalence of which is unknown. Objective: To establish a pattern of perimenstrual acne flare in adult women in order to better characterize the disorder. Methods: Subjects aged 18 and over were recruited during previously scheduled visits with their dermatologist at Mount Sinai Hospital in New York. An anonymous survey was distributed to women who reported their first menses at least six months earlier and had a complaint of acne within the last 30 days. Women <18 years of age and postmenopausal women were excluded from the study population. Results: Participants included women 18- to 29-years old (67%) and women 30- to 49-years old (33%). The ethnicity of respondents was Caucasian (50%), African American (20%), Latino (19%), Asian (5%), and Other (6%). The majority of participants with perimenstrual acne reported the onset of acne between the ages of 12 and 18 years. Sixty-five percent of participants reported that their acne symptoms were worse with their menses. Of those who reported perimenstrual acne symptoms, 56 percent reported worsening symptoms in the week preceding their menses, 17 percent reported worsening symptoms during their menses, three percent reported worsening symptoms after their menses, and 24 percent reported worsening symptoms throughout their cycle. Thirty-five percent of patients with perimenstrual acne reported oral contraceptive pill use. Conclusion: A significant number of adult women have perimenstrual acne symptoms. This study has proven to be useful in characterizing perimenstrual acne flare and is one of the first qualitative documentations of the presence and degree of this disorder. PMID:25161758

  12. Combining hydrodynamic modeling with nonthermal test particle tracking to improve flare simulations

    NASA Astrophysics Data System (ADS)

    Winter, Henry Degraffenried, III

    Solar flares remain a subject of intense study in the solar physics community. These huge releases of energy on the Sun have direct consequences for humans on Earth and in space. The processes that impart tremendous amounts of energy are not well understood. In order to test theoretical models of flare formation and evolution, state of the art, numerical codes must be created that can accurately simulate the wide range of electromagnetic radiation emitted by flares. A direct comparison of simulated radiation to increasingly detailed observations will allow scientists to test the validity of theoretical models. To accomplish this task, numerical codes were developed that can simulate both the thermal and nonthermal components of a flaring plasma, their interactions, and their emissions. The HYLOOP code combines a hydrodynamic equation solver with a nonthermal particle tracking code in order to simulate the thermal and nonthermal aspects of a flare. A solar flare was simulated using this new code with a static atmosphere and with a dynamic atmosphere, to illustrate the importance of considering hydrodynamic effects on nonthermal beam evolution. The importance of density gradients in the evolution of nonthermal electron beams was investigated by studying their effects in isolation. The importance of the initial pitch-angle cosine distribution to flare dynamics was investigated. Emission in XRT filters were calculated and analyzed to see if there were soft X-ray signatures that could give clues to the nonthermal particle distributions. Finally the HXR source motions that appeared in the simulations were compared to real observations of this phenomena.

  13. Coordinated NIR/mm observations of flare emission from Sagittarius A*

    NASA Astrophysics Data System (ADS)

    Kunneriath, D.; Witzel, G.; Eckart, A.; Zamaninasab, M.; Gießübel, R.; Schödel, R.; Baganoff, F. K.; Morris, M. R.; Dovčiak, M.; Duschl, W. J.; García-Marín, M.; Karas, V.; König, S.; Krichbaum, T. P.; Krips, M.; Lu, R.-S.; Mauerhan, J.; Moultaka, J.; Mužić, K.; Sabha, N.; Najarro, F.; Pott, J.-U.; Schuster, K. F.; Sjouwerman, L. O.; Straubmeier, C.; Thum, C.; Vogel, S. N.; Teuben, P.; Weiss, A.; Wiesemeyer, H.; Zensus, J. A.

    2010-07-01

    that either the adiabatically expanding source components have a bulk motion greater than vexp or the expanding material contributes to a corona or disk, confined to the immediate surroundings of Sgr A*. Applying the flux density values or limits in the mm- and X-ray domain to the observed flare events constrains the turnover frequency of the synchrotron components that are on average not lower than about 1 THz, such that the optically thick peak flux densities at or below these turnover frequencies do not exceed, on average, about ~1 Jy.

  14. Particle acceleration in solar flares

    NASA Astrophysics Data System (ADS)

    Klecker, Berndt; Cliver, Ed; Kahler, Steve; Cane, Hilary

    Particle acceleration in solar flares was the topic of a workshop held at the University of Tasmania in Hobart, Australia, January 24-26, 1990. The workshop was held in conjunction with the 21st International Cosmic Ray Conference in Adelaide, South Australia, January 6-19, 1990. Forty-six scientists participated in the workshop, which was organized by Hilary Cane and John Humble of the University of Tasmania; Marc Duldig, Australian Antarctic Division, University of Tasmania; Ed Cliver, Geophysics Laboratory, U.S. Air Force Systems Command; and Steve Kahler, Boston College, Mass.

  15. Sun Releases X-class Solar Flare

    NASA Video Gallery

    This movie shows the July 6, 2012 X1.1 flare in the 171 Angstrom wavelength as captured by NASA’s Solar Dynamics Observatory (SDO). AR1515 was the source for this flare. AR1515 has been active ...

  16. AR 1121 Unleases X-ray Flare

    NASA Video Gallery

    Increasingly active sunspot 1121 has unleashed one of the brightest x-ray solar flares in years, an M5.4-class eruption at 15:36 UT on Nov. 6th. This close-up video shows the detail of the flare an...

  17. ASASSN-16ae: A Powerful White-light Flare on an Early-L Dwarf

    NASA Astrophysics Data System (ADS)

    Schmidt, Sarah J.; Shappee, Benjamin J.; Gagné, Jonathan; Stanek, K. Z.; Prieto, José L.; Holoien, Thomas W.-S.; Kochanek, C. S.; Chomiuk, Laura; Dong, Subo; Seibert, Mark; Strader, Jay

    2016-09-01

    We report the discovery and classification of SDSS J053341.43+001434.1 (SDSS0533), an early-L dwarf first discovered during a powerful ΔV < ‑11 magnitude flare observed as part of the ASAS-SN survey. Optical and infrared spectroscopy indicate a spectral type of L0 with strong Hα emission and a blue NIR spectral slope. Combining the photometric distance, proper motion, and radial velocity of SDSS0533 yields three-dimensional velocities of (U, V, W) = (14 ± 13, ‑35 ± 14, ‑94 ± 22) km s‑1, indicating that it is most likely part of the thick disk population and probably old. The three detections of SDSS0533 obtained during the flare are consistent with a total V-band flare energy of at least 4.9 × 1033 erg (corresponding to a total thermal energy of at least E tot > 3.7 × 1034 erg), placing it among the strongest detected M dwarf flares. The presence of this powerful flare on an old L0 dwarf may indicate that stellar-type magnetic activity persists down to the end of the main sequence and on older ML transition dwarfs.

  18. ASASSN-16ae: A Powerful White-light Flare on an Early-L Dwarf

    NASA Astrophysics Data System (ADS)

    Schmidt, Sarah J.; Shappee, Benjamin J.; Gagné, Jonathan; Stanek, K. Z.; Prieto, José L.; Holoien, Thomas W.-S.; Kochanek, C. S.; Chomiuk, Laura; Dong, Subo; Seibert, Mark; Strader, Jay

    2016-09-01

    We report the discovery and classification of SDSS J053341.43+001434.1 (SDSS0533), an early-L dwarf first discovered during a powerful ΔV < -11 magnitude flare observed as part of the ASAS-SN survey. Optical and infrared spectroscopy indicate a spectral type of L0 with strong Hα emission and a blue NIR spectral slope. Combining the photometric distance, proper motion, and radial velocity of SDSS0533 yields three-dimensional velocities of (U, V, W) = (14 ± 13, -35 ± 14, -94 ± 22) km s-1, indicating that it is most likely part of the thick disk population and probably old. The three detections of SDSS0533 obtained during the flare are consistent with a total V-band flare energy of at least 4.9 × 1033 erg (corresponding to a total thermal energy of at least E tot > 3.7 × 1034 erg), placing it among the strongest detected M dwarf flares. The presence of this powerful flare on an old L0 dwarf may indicate that stellar-type magnetic activity persists down to the end of the main sequence and on older ML transition dwarfs.

  19. Solar flare mechanism based on magnetic arcade reconnection and island merging

    SciTech Connect

    C.Z. Chen; G.S. Choe

    2000-06-15

    The authors propose a model describing physical processes of solar flares based on resistive reconnection of magnetic field subject to continuous increase of magnetic shear in the arcade. The individual flaring process consists of magnetic reconnection of arcade field lines, generation of magnetic islands in the magnetic arcade, and coalescence of magnetic islands. When a magnetic arcade is sheared (either by foot point motion or by flux emergence), a current sheet is formed and magnetic reconnection can take place to form a magnetic island. A continuing increase of magnetic shear can trigger a new reconnection process and create a new island in the under lying arcade below the magnetic island. The new born island rises faster than the preceding island and merges with it to form one island. Before completing the island merging process, the new born island exhibits two phases of rising motion: a first phase with a slower rising speed and a second phase with a faster rising speed. The flare plasma heating occurs mainly due to magnetic reconnection in the current sheet under the new born island. The new born island represents the X-ray plasma ejecta which shows two phases of rising motion observed by Yohkoh [Ohyama and Shibata (1997)]. The first phase with slower new born island rising speed corresponds to the early phase of reconnection of line-tied field in the underlying current sheet and is considered as the preflare phase. In the second phase, the island coalescence takes place, and the underlying current sheet is elongated so that the line-tied arcade field reconnection rate is enhanced. This phase is interpreted as the impulsive phase or the flash phase of flares. The obtained reconnection electric field is large enough to accelerate electrons to an energy level higher than 10 keV, which is necessary for observed hard X-ray emissions. After merging of the islands is completed, magnetic reconnection continues in the current sheet under the integrated island for

  20. THE MAGNETIC SYSTEMS TRIGGERING THE M6.6 CLASS SOLAR FLARE IN NOAA ACTIVE REGION 11158

    SciTech Connect

    Toriumi, Shin; Iida, Yusuke; Bamba, Yumi; Kusano, Kanya; Imada, Shinsuke; Inoue, Satoshi

    2013-08-20

    We report a detailed event analysis of the M6.6 class flare in the active region (AR) NOAA 11158 on 2011 February 13. AR 11158, which consisted of two major emerging bipoles, showed prominent activity including one X- and several M-class flares. In order to investigate the magnetic structures related to the M6.6 event, particularly the formation process of a flare-triggering magnetic region, we analyzed multiple spacecraft observations and numerical results of a flare simulation. We observed that, in the center of this quadrupolar AR, a highly sheared polarity inversion line (PIL) was formed through proper motions of the major magnetic elements, which built a sheared coronal arcade lying over the PIL. The observations lend support to the interpretation that the target flare was triggered by a localized magnetic region that had an intrusive structure, namely, a positive polarity penetrating into a negative counterpart. The geometrical relationship between the sheared coronal arcade and the triggering region is consistent with the theoretical flare model based on the previous numerical study. We found that the formation of the trigger region was due to the continuous accumulation of small-scale magnetic patches. A few hours before the flare occurred, the series of emerged/advected patches reconnected with a pre-existing field. Finally, the abrupt flare eruption of the M6.6 event started around 17:30 UT. Our analysis suggests that in the process of triggering flare activity, all magnetic systems on multiple scales are included, not only the entire AR evolution but also the fine magnetic elements.

  1. THERMAL FRONTS IN SOLAR FLARES

    SciTech Connect

    Karlický, Marian

    2015-12-01

    We studied the formation of a thermal front during the expansion of hot plasma into colder plasma. We used a three-dimensional electromagnetic particle-in-cell model that includes inductive effects. In early phases, in the area of the expanding hot plasma, we found several thermal fronts, which are defined as a sudden decrease of the local electron kinetic energy. The fronts formed a cascade. Thermal fronts with higher temperature contrast were located near plasma density depressions, generated during the hot plasma expansion. The formation of the main thermal front was associated with the return-current process induced by hot electron expansion and electrons backscattered at the front. A part of the hot plasma was trapped by the thermal front while another part, mainly with the most energetic electrons, escaped and generated Langmuir and electromagnetic waves in front of the thermal front, as shown by the dispersion diagrams. Considering all of these processes and those described in the literature, we show that anomalous electric resistivity is produced at the location of the thermal front. Thus, the thermal front can contribute to energy dissipation in the current-carrying loops of solar flares. We estimated the values of such anomalous resistivity in the solar atmosphere together with collisional resistivity and electric fields. We propose that the slowly drifting reverse drift bursts, observed at the beginning of some solar flares, could be signatures of the thermal front.

  2. Thermal Fronts in Solar Flares

    NASA Astrophysics Data System (ADS)

    Karlický, Marian

    2015-12-01

    We studied the formation of a thermal front during the expansion of hot plasma into colder plasma. We used a three-dimensional electromagnetic particle-in-cell model that includes inductive effects. In early phases, in the area of the expanding hot plasma, we found several thermal fronts, which are defined as a sudden decrease of the local electron kinetic energy. The fronts formed a cascade. Thermal fronts with higher temperature contrast were located near plasma density depressions, generated during the hot plasma expansion. The formation of the main thermal front was associated with the return-current process induced by hot electron expansion and electrons backscattered at the front. A part of the hot plasma was trapped by the thermal front while another part, mainly with the most energetic electrons, escaped and generated Langmuir and electromagnetic waves in front of the thermal front, as shown by the dispersion diagrams. Considering all of these processes and those described in the literature, we show that anomalous electric resistivity is produced at the location of the thermal front. Thus, the thermal front can contribute to energy dissipation in the current-carrying loops of solar flares. We estimated the values of such anomalous resistivity in the solar atmosphere together with collisional resistivity and electric fields. We propose that the slowly drifting reverse drift bursts, observed at the beginning of some solar flares, could be signatures of the thermal front.

  3. Millimeter emission of solar flares

    NASA Astrophysics Data System (ADS)

    Nagnibeda, V. G.; Smirnova, V. V.; Ryzhov, V. S.; Zhiltsov, A. V.

    2013-06-01

    We analyzed two unique radio observations of millimeter solar flares at 93 and 140 GHz with the THz component in these spectra. Data were obtained from ground-based radio-telescope RT-7.5 operated by Bauman Moscow State Technical University (BMSTU) with the spacial resolution of 2.5 and 1.5 arc-minutes. We analyzed temporal structure of observed radio-bursts and their dynamics in comparison with soft and hard X-ray light-curves obtained from GOES and RHESSI space-based observations. It was found the 140 GHz emission enhancement at the spectra that is new independent confirmation of the THz component existance. Also, we analyzed data of microwave solar flares with the emission enhanced at 35 GHz obtained from Nobeyama radioheliograph (NoRH) and radiopolarimeter (NoRP). It was found that the maximum of the flux density spectra was shifted toward high frequencies that didn't agree with the model spectrum obtained from microwave observations. We assumed, that such kind of spectra are associated with the gyro-synchrotron radiation of the significant number of high-energetic electrons emission with energies of about 500 keV. The emission mechanism at millimeter waves is the gyro-synchrotron radiation. However, if the energetic electrons are not enough the thermal emission mechanism could be dominant factor at millimeter radiation that could also explain the spectral maximum shift to high frequencies.

  4. Heating and Cooling of Flare Loops in a C5.7 Two-ribbon Flare

    NASA Astrophysics Data System (ADS)

    Pearce, Sarah; Qiu, Jiong

    2016-05-01

    Heating and cooling of flare plasmas can be studied using models constrained by observations. In this work, we analyze and model thermal evolution of a C5.7 two-ribbon flare that occurred on December 26, 2011. The flare was observed by AIA. Two hundred flare loops are identified, which formed sequentially during one hour. Light curves of these flare loops in multiple EUV bands are analyzed to derive the duration and timing of flare emission in each bandpass. These timescales usually reflect cooling of flare plasmas from 10~MK to successively lower temperatures. We then use a zero-dimensional enthalpy-based thermal evolution of loops (EBTEL) model to study flare heating and cooling. Several variations on the EBTEL model are assessed. The first model uses an impulsive heating function inferred from the rapid rise of the foot-point UV emission. Synthetic emission from this model evolves and decays more quickly than the observations, as many models do. Two other variations on the model are analyzed, in an attempt to counter this. In one variation the heating function is a combination of an impulsive pulse followed by an extended tail (i.e., continuous heating). The other model uses reduced thermal conduction to slow the flares evolution. These models are compared with one another and the observations, to evaluate effects of different mechanisms governing the thermal evolution of flare plasmas.

  5. High-resolution X-ray spectra of solar flares. III - General spectral properties of X1-X5 type flares

    NASA Technical Reports Server (NTRS)

    Doschek, G. A.; Feldman, U.; Kreplin, R. W.; Cohen, L.

    1980-01-01

    High-resolution X-ray spectra of six class X1-X5 solar flares are discussed. The spectra were recorded by spaceborne Bragg crystal spectrometers in the ranges 1.82-1.97, 2.98-3.07 and 3.14-3.24 A. Electron temperatures derived from dielectronic satellite line to resonance line ratios for Fe XXV and Ca XIX are found to remain fairly constant around 22,000,000 and 16,000,000 K respectively during the rise phase of the flares, then decrease by approximately 6,000,000 K during the decay phase. Nonthermal motions derived from line widths for the April 27, 1979 event are found to be greatest during the rise phase (approximately 130 km/sec) and decrease to about 60 km/sec during decay. Volume emission measures for Fe XXV, Ca XIX and Ca XX are derived from photon fluxes as a function of temperature, and examination of the intensity behavior of the Fe K alpha emission as a function of time indicates that it is a result of fluorescence. Differences between the present and previous observations of temperature variation are discussed, and it is concluded that the flare plasmas are close to ionization equilibrium for the flares investigated.

  6. Solar flare leaves sun quaking

    NASA Astrophysics Data System (ADS)

    1998-05-01

    Dr. Alexander G. Kosovichev, a senior research scientist from Stanford University, and Dr. Valentina V. Zharkova from Glasgow (United Kingdom) University found the tell-tale seismic signature in data on the Sun's surface collected by the Michelson Doppler Imager onboard the Solar and Heliospheric Observatory (SOHO) spacecraft immediately following a moderate-sized flare on July 9, 1996. "Although the flare was a moderate one, it still released an immense amount of energy," said Dr. Craig Deforest, a researcher with the SOHO project. "The energy released is equal to completely covering the Earth's continents with a yard of dynamite and detonating it all at once." SOHO is a joint project of the European Space Agency and NASA. The finding is reported in the May 28 issue of the journal Nature, and is the subject of a press conference at the spring meeting of the American Geophysical Union in Boston, Mass., May 27. The solar quake that the science team recorded looks much like ripples spreading from a rock dropped into a pool of water. But over the course of an hour, the solar waves traveled for a distance equal to 10 Earth diameters before fading into the fiery background of the Sun's photosphere. Unlike water ripples that travel outward at a constant velocity, the solar waves accelerated from an initial speed of 22,000 miles per hour to a maximum of 250,000 miles per hour before disappearing. "People have looked for evidence of seismic waves from flares before, but they didn't have a theory so they didn't know where to look," says Kosovichev. Several years ago Kosovichev and Zharkova developed a theory that can explain how a flare, which explodes in space above the Sun's surface, can generate a major seismic wave in the Sun's interior. According to the currently accepted model of solar flares, the primary explosion creates high-energy electrons (electrically charged subatomic particles). These are funneled down into a magnetic flux tube, an invisible tube of magnetic

  7. Measurements of Continuum Flux in Solar Flares

    NASA Astrophysics Data System (ADS)

    Kotrč, P.; Heinzel, P.; Procházka, O.

    2016-04-01

    A broad-band diagnostics of chromospheric flare plasma needs to analyze spectra covering many spectral lines and various continuum features. The flare spectra are well detected on the background of the solar disk, but the detection of flare line emission from the Sun-as-a-star in optical is much more difficult due to a strong background radiation. When the flare/background radiation contrast is strong enough to be detected, we need a device for measuring the flux from a selected part of the flaring region. Here we present technical demands for such an instrument and its brief description. This device denoted as Image Selector is a post-focus instrument installed at the horizontal solar telescope HSFA2 of the Ondřejov observatory, described by Kotrč (2009). Its core consists of a system of diaphragms, imaging Hα telescope and a fast spectrometer with dispersion of 3 px per Å but with cadency reaching up to 50 frames per second. The first solar flares observed recently by this novel technique provide quite interesting results. Our analysis of the data proves that the described device is sufficiently sensitive to detect variations in the Balmer continuum during solar flares.

  8. Solar Flares and their Effects on Planets

    NASA Astrophysics Data System (ADS)

    Guinan, Edward Francis; Engle, Scott G.

    2015-08-01

    The effects of flares from the Sun on Earth and other solar-system planets are discussed. The strong X-ray - UV radiation and high plasma fluxes from flares can strongly effect solar system planets even as far out as the Jovian planets and their moons. Data from our "Sun in Time" program are used to study the flare properties of the Sun and solar-type stars from youth to old age. These data imply that the young Sun had numerous, very powerful flares that may have played major roles in the development and evolution of the early atmospheres of Earth and other terrestiral planets. These strong X-UV fluxes from flares can greatly effect the photochemistry of planetary atmospheres as well as ionizing and possibly eroding their atmospheres. Some examples are given. Also briefly discussed are effects of large flares from the present Sun on the Earth. Even though strong solar flares are rarer and less powerful than from the youthful Sun, they can cause significant damage to our communication and satellite systems, electrical networks, and threaten the lives of astronauts in space.This research is supported by grants from NASA (HST and Chandra) and NSF. We gratefully acknowledge this support

  9. How big was the Carrington 1859 Flare?

    NASA Astrophysics Data System (ADS)

    Cliver, E. W.; Svalgaard, L.; Neidig, D. F.

    2004-05-01

    The 1859 space weather event was distinguished by its great geomagnetic storm, widespread low-latitude aurora, and intense solar energetic particle event (inferred from the NO3 concentration in polar ice cores). Arguably each of these three effects was the largest ever observed. What can we say about the size of the associated solar flare? We have two observations with which to make such an assessment: (1) Carrington's and Hodgson's report of the white-light flare and (2) the solar flare effect or magnetic crochet observed in the Kew and Greenwich magnetograms. Estimates of the area, duration, spectrum, and intensity of the white-light emission indicate a large (~2 x 1030 erg) but not unequalled event (the white-light emission of the 24 April 1984 >X13 flare contained ~6 x 1030 erg). The magnetic crochet of 130 nT in the horizontal force, however, exceeds that for all >X10 soft X-ray flares observed from 1984-2002 (we are presently compiling magnetic data for the recent October-November 2003 activity for comparison with the 1859 event). Thus at this point, we can conservatively say that Carrington's flare likely had a soft X-ray classification >X10 and was at least comparable to the largest flares recorded during the spacecraft era.

  10. Avalanches and the distribution of solar flares

    NASA Technical Reports Server (NTRS)

    Lu, Edward T.; Hamilton, Russell J.

    1991-01-01

    The solar coronal magnetic field is proposed to be in a self-organized critical state, thus explaining the observed power-law dependence of solar-flare-occurrence rate on flare size which extends over more than five orders of magnitude in peak flux. The physical picture that arises is that solar flares are avalanches of many small reconnection events, analogous to avalanches of sand in the models published by Bak and colleagues in 1987 and 1988. Flares of all sizes are manifestations of the same physical processes, where the size of a given flare is determined by the number of elementary reconnection events. The relation between small-scale processes and the statistics of global-flare properties which follows from the self-organized magnetic-field configuration provides a way to learn about the physics of the unobservable small-scale reconnection processes. A simple lattice-reconnection model is presented which is consistent with the observed flare statistics. The implications for coronal heating are discussed and some observational tests of this picture are given.

  11. Identification of Candidate Predictors of Lupus Flare.

    PubMed

    Crow, Mary K; Olferiev, Mikhail; Kirou, Kyriakos A

    2015-01-01

    Systemic lupus erythematosus, the prototype systemic autoimmune disease, is characterized by extensive self-reactivity, inflammation, and organ system damage. Sustained production of type I interferon is seen in many patients and contributes to immune dysregulation. Disease activity fluctuates with periods of relative quiescence or effective management by immunosuppressive drugs, followed by disease flares. Tissue damage accumulates over time, with kidneys and cardiovascular system particularly affected. Identification of the underlying molecular mechanisms that precede clinical exacerbations, allowing prediction of future flare, could lead to therapeutic interventions that prevent severe disease. We generated gene expression data from a longitudinal cohort of lupus patients, some showing at least one period of severe flare and others with relatively stable disease over the period of study. Candidate predictors of future clinical flare were identified based on analysis of differentially expressed gene transcripts between the flare and non-flare groups at a time when all patients had relatively quiescent clinical disease activity. Our results suggest the hypothesis that altered regulation of genome stability and nucleic acid fidelity may be important molecular precursors of future clinical flare, generating endogenous nucleic acid triggers that engage intracellular mechanisms that mimic a chronic host response to viral infection.

  12. Observational characteristics of the white-light flare of August 9, 2011

    NASA Astrophysics Data System (ADS)

    Babin, A. N.; Koval', A. N.

    2014-06-01

    We analyzed the monochromatic Hα and spectral (within a range of 6549-6579 Å) observational data for the 2B/X6.9 flare of August 9, 2011, that produced emission in the optical continuum. The morphology and evolution of the Hα flare and the position, time evolution, spectrum, and energetics of the white-light flare (WLF) kernels were studied. The following results were obtained: the flare erupted in the region of collision of a new and rapidly growing and propagating magnetic flux and a preexisting one. This collision led to a merger of two active bipolar regions. The white-light flare had a complex structure: no less than five kernels of continuum emission were detected prior to and in the course of the impulsive flare phase. Preimpulsive and impulsive white-light emission kernels belonged to different types (types II and I, respectively) of white-light flares. A close temporal agreement between the white-light emission maxima and the microwave emission peak was observed for the impulsive white-light emission kernels. The maximum flux, luminosity, and total energy emitted by the brightest impulsive WLF kernel equaled 1.4 × 1010 ergs cm-2 s-1, 1.5 × 1027 ergs/s, and 5 × 1029 ergs, respectively. The Hα profiles within the impulsive WLF kernels had broad wings (with a total extent of up to 26 Å and a half-width of up to 9 Å) and self-reversed cores. The profiles were symmetrical, but were shifted towards the red side of the spectrum. This is indicative of a downward motion of the entire emitting volume with a radial velocity of several tens of km/s. The intensity pattern in the wings did not correspond to the Stark one. The profiles were broadened by nonthermal turbulent motions with velocities of 150-300 km/s. The observed Hα profiles were analyzed and compared in their features to the profiles calculated for an intense heating of the chromosphere by nonthermal electrons accompanied by the development of a chromospheric condensation propagating downward. We

  13. Planetary Protection: X-ray Super-Flares Aid Formation of "Solar Systems"

    NASA Astrophysics Data System (ADS)

    2005-05-01

    form. Specifically, this turbulence can help prevent planets from rapidly migrating towards the young star. "Although these flares may be creating havoc in the disks, they ultimately could do more good than harm," said Feigelson. "These flares may be acting like a planetary protection program." About half of the young suns in Orion show evidence for disks, likely sites for current planet formation, including four lying at the center of proplyds (proto-planetary disks) imaged by Hubble Space Telescope. X-ray flares bombard these planet-forming disks, likely giving them an electric charge. This charge, combined with motion of the disk and the effects of magnetic fields should create turbulence in the disk. handra X-ray Image of Orion Nebula, Full-Field Chandra X-ray Image of Orion Nebula, Full-Field The numerous results from the Chandra Orion Ultradeep Project will appear in a dedicated issue of The Astrophysical Journal Supplement in October, 2005. The team contains 37 scientists from institutions across the world including the US, Italy, France, Germany, Taiwan, Japan and the Netherlands. NASA's Marshall Space Flight Center, Huntsville, Ala., manages the Chandra program for NASA's Science Mission Directorate, Washington. Northrop Grumman of Redondo Beach, Calif., was the prime development contractor for the observatory. The Smithsonian Astrophysical Observatory controls science and flight operations from the Chandra X-ray Center in Cambridge, Mass. Additional information and images are available at: http://chandra.harvard.edu and http://chandra.nasa.gov

  14. The flare kernel in the impulsive phase

    NASA Technical Reports Server (NTRS)

    Dejager, C.

    1986-01-01

    The impulsive phase of a flare is characterized by impulsive bursts of X-ray and microwave radiation, related to impulsive footpoint heating up to 50 or 60 MK, by upward gas velocities (150 to 400 km/sec) and by a gradual increase of the flare's thermal energy content. These phenomena, as well as non-thermal effects, are all related to the impulsive energy injection into the flare. The available observations are also quantitatively consistent with a model in which energy is injected into the flare by beams of energetic electrons, causing ablation of chromospheric gas, followed by convective rise of gas. Thus, a hole is burned into the chromosphere; at the end of impulsive phase of an average flare the lower part of that hole is situated about 1800 km above the photosphere. H alpha and other optical and UV line emission is radiated by a thin layer (approx. 20 km) at the bottom of the flare kernel. The upward rising and outward streaming gas cools down by conduction in about 45 s. The non-thermal effects in the initial phase are due to curtailing of the energy distribution function by escape of energetic electrons. The single flux tube model of a flare does not fit with these observations; instead we propose the spaghetti-bundle model. Microwave and gamma-ray observations suggest the occurrence of dense flare knots of approx. 800 km diameter, and of high temperature. Future observations should concentrate on locating the microwave/gamma-ray sources, and on determining the kernel's fine structure and the related multi-loop structure of the flaring area.

  15. Bayesian model comparison of solar flare spectra

    NASA Astrophysics Data System (ADS)

    Ireland, J.; Holman, G.

    2012-12-01

    The detailed understanding of solar flares requires an understanding of the physics of accelerated electrons, since electrons carry a large fraction of the total energy released in a flare. Hard X-ray energy flux spectral observations of solar flares can be fit with different parameterized models of the interaction of the flare-accelerated electrons with the solar plasma. Each model describes different possible physical effects that may occur in solar flares. Bayesian model comparison provides a technique for assessing which model best describes the data. The advantage of this technique over others is that it can fully account for the different number and type of parameters in each model. We demonstrate this using Ramaty High Energy Solar Spectroscopic Imager (RHESSI) spectral data from the GOES (Geostationary Operational Environmental Satellite) X4.8 flare of 23-July-2002. We suggest that the observed spectrum can be reproduced using two different parameterized models of the flare electron content. The first model assumes that the flare-accelerated electron spectrum consisting of a single power law with a fixed low energy cutoff assumed to be below the range of fitted X-ray energies, interacting with a non-uniformly ionized target. The second model assumes that the flare-accelerated electron spectrum has a broken power law and a low energy cutoff, which interacts with a fully ionized target plasma. The low energy cutoff in this model is a parameter used in fitting the data. We will introduce and use Bayesian model comparison techniques to decide which model best explains the observed data. This work is funded by the NASA Solar and Heliospheric Physics program.

  16. Plasma dynamics above solar flare soft x-ray loop tops

    SciTech Connect

    Doschek, G. A.; Warren, H. P.; McKenzie, D. E.

    2014-06-10

    We measure non-thermal motions in flare loop tops and above the loop tops using profiles of highly ionized spectral lines of Fe XXIV and Fe XXIII formed at multimillion-degree temperatures. Non-thermal motions that may be due to turbulence or multiple flow regions along the line of sight are extracted from the line profiles. The non-thermal motions are measured for four flares seen at or close to the solar limb. The profile data are obtained using the Extreme-ultraviolet Imaging Spectrometer on the Hinode spacecraft. The multimillion-degree non-thermal motions are between 20 and 60 km s{sup –1} and appear to increase with height above the loop tops. Motions determined from coronal lines (i.e., lines formed at about 1.5 MK) tend to be smaller. The multimillion-degree temperatures in the loop tops and above range from about 11 MK to 15 MK and also tend to increase with height above the bright X-ray-emitting loop tops. The non-thermal motions measured along the line of sight, as well as their apparent increase with height, are supported by Solar Dynamics Observatory Atmospheric Imaging Assembly measurements of turbulent velocities in the plane of the sky.

  17. New flare diagnostics from loop modeling of a stellar flare observedwith XMM-Newton

    NASA Astrophysics Data System (ADS)

    Reale, F.

    XMM-Newton data of an X-ray flare observed on Proxima Centauri provide detailed and challenging constraints for flare modeling. The comparison of the data with the results of time-dependent hydrodynamic loop modeling of this flare allows us to constrain not only the loop morphology, but also the details of the heating function. The results show that even a complex flare event like this can be described with a relatively few - though constrained - components: two loop systems, i.e. a single loop and an arcade, and two heat components, an intense pulse probably located at the loop footpoints followed by a low gradual decay distributed in the coronal part of the loop. The similarity to at least one solar event (the Bastille Day flare in 2000) indicate that this pattern may be common to solar and stellar flares.

  18. Flare diagnostics from loop modeling of a stellar flare observed with XMM-Newton

    NASA Astrophysics Data System (ADS)

    Reale, Fabio

    2006-01-01

    XMM-Newton data of an X-ray flare observed on Proxima Centauri provide detailed and challenging constraints for flare modeling. The comparison of the data with the results of time-dependent hydrodynamic loop modeling of this flare allows us to constrain not only the loop morphology, but also the details of the heating function. The results show that even a complex flare event like this can be described with a relatively few though constrained components: two loop systems, i.e., a single loop and an arcade, and two heat components, an intense pulse probably located at the loop footpoints followed by a low gradual decay distributed in the coronal part of the loop. The similarity to at least one solar event (the Bastille Day flare in 2000) indicates that this pattern may be common to solar and stellar flares.

  19. He-3-rich flares - A possible explanation

    NASA Technical Reports Server (NTRS)

    Fisk, L. A.

    1978-01-01

    A plasma mechanism is proposed to explain the dramatic enhancements in He-3 observed in He-3-rich flares. It is shown that a common current instability in the corona may heat ambient He-3(2+) over any other ion and thus may preferentially inject He-3 into the flare acceleration process. This mechanism operates when the abundance of He-4 and heavier elements is larger than normal in the coronal plasma. It may also preferentially heat and thus inject certain ions of iron. The mechanism thus provides a possible explanation for the observed correlation between He-3 and heavy enhancements in He-3-rich flares.

  20. Neutrons and Gamma Rays from Solar Flares

    NASA Technical Reports Server (NTRS)

    Ramaty, R.; Murphy, R. J.

    1983-01-01

    The theory of neutron and gamma-ray production in flares is reviewed and comparisons of the calculations with data are made. The principal conclusions pertain to the accelerated proton and electron numbers and spectra in flares and to the interaction site of these particles in the solar atmosphere. For the June 21, 1980 flare, from which high-energy neutrons and high-energy ( MeV) photons were seen, the electron-to-proton ratio is energy dependent and much smaller than unity at energies greater than 1 MeV. The interaction site of these particles appears to be the solar chromosphere.

  1. Quasi-static evolution of sheared force-free fields and the solar flare problem

    NASA Technical Reports Server (NTRS)

    Aly, J. J.

    1985-01-01

    Some new results are given showing the possible evolution of a two-dimensional force-free field in the half-space z greater than 0 toward an open field. This evolution is driven by shearing motions applied to the feet of the field lines on the boundary z = 0. The consequences of these results for a model of the two-ribbon solar flare are discussed.

  2. The landing flare: An analysis and flight-test investigation

    NASA Technical Reports Server (NTRS)

    Seckel, E.

    1975-01-01

    Results are given of an extensive investigation of conventional landing flares in general aviation type airplanes. A wide range of parameters influencing flare behavior are simulated in experimental landings in a variable-stability Navion. The most important feature of the flare is found to be the airplane's deceleration in the flare. Various effects on this are correlated in terms of the average flare load factor. Piloting technique is extensively discussed. Design criteria are presented.

  3. Positron annihilation in solar flares

    NASA Technical Reports Server (NTRS)

    Crannell, C. J.; Ramaty, R.; Werntz, C.

    1975-01-01

    The gamma ray line at 0.51 MeV originates from the annihilation of positrons. When a fraction of the positrons annihilate from bound states of positronium, the 0.51-MeV line is accompanied by a continuum of 3-gamma annihilation radiation at energies up to 0.51 MeV. Accurate calculations of the rates of free annihilation and positronium formation in a solar flare plasma are presented and positronium formation by charge exchange is discussed. The observability of the 3-gamma annihilation is increased by the inherent delay in the production and slowing down time of the positrons. It was concluded that such radiation could be detected at times late in solar gamma ray events when the continuum and prompt line emissions have essentially disappeared.

  4. Development of Daily Solar Maximum Flare Flux Forecast Models for Strong Flares

    NASA Astrophysics Data System (ADS)

    Shin, Seulki; Chu, Hyoungseok

    2015-08-01

    We have developed a set of daily solar maximum flare flux forecast models for strong flares using Multiple Linear Regression (MLR) and Artificial Neural Network (ANN) methods. We consider input parameters as solar activity data from January 1996 to December 2013 such as sunspot area, X-ray maximum flare flux and weighted total flux of the previous day, and mean flare rates of McIntosh sunspot group (Zpc) and Mount Wilson magnetic classification. For a training data set, we use the same number of 61 events for each C-, M-, and X-class from Jan. 1996 to Dec. 2004, while other previous models use all flares. For a testing data set, we use all flares from Jan. 2005 to Nov. 2013. The statistical parameters from contingency tables show that the ANN models are better for maximum flare flux forecasting than the MLR models. A comparison between our maximum flare flux models and the previous ones based on Heidke Skill Score (HSS) shows that our all models for X-class flare are much better than the other models. According to the Hitting Fraction (HF), which is defined as a fraction of events satisfying that the absolute differences of predicted and observed flare flux in logarithm scale are less than equal to 0.5, our models successfully forecast the maximum flare flux of about two-third events for strong flares. Since all input parameters for our models are easily available, the models can be operated steadily and automatically on daily basis for space weather service.

  5. Solar flare count periodicities in different X-ray flare classes

    NASA Astrophysics Data System (ADS)

    Gao, Peng-Xin; Xu, Jing-Chen

    2016-04-01

    Using the Morlet wavelet transform and the Hilbert-Huang transform (HHT), we investigate the periodic behaviours of C, M and X-class flare counts, respectively, recorded by the Geostationary Operational Environmental Satellites (GOES) from 1983 May to 2014 December, which cover the two complete solar cycles (SCs) 22 and 23 as well as the part of declining phase of SC 21 and rise and maximum phases of SC 24. Analyses show that the periodic behaviours of various class flare counts are different. (1) Not all periods of various class flare counts appear dominant during the cycle maxima. For C-class flares, during SC 23, periods appear dominant during the maximum phase, however, compared to those during SC 23, there are more periods during the declining phase of SC 22; for M-class flares, during SCs 22 and 23, periods appear dominant during the cycle maxima; for X-class flares, during SC 22, almost all periods appear during the maximum phase; however, during SC 23, there are more periods during the declining phase compared to those during SC 22. (2) For C-class flares, the appearance of periods do not follow the amplitude of C-class flare cycles; while, for M and X-class flares, the appearance of periods follows the amplitude of the investigated corresponding class flare cycles. (3) From the overall trends, the 10 yr and longer time-scale trends of the monthly numbers of M and X-class flares, we can infer that the maximum values of the monthly M and X-class flare numbers would increase during SC 25.

  6. Plate motion

    SciTech Connect

    Gordon, R.G. )

    1991-01-01

    The motion of tectonic plates on the earth is characterized in a critical review of U.S. research from the period 1987-1990. Topics addressed include the NUVEL-1 global model of current plate motions, diffuse plate boundaries and the oceanic lithosphere, the relation between plate motions and distributed deformations, accelerations and the steadiness of plate motions, the distribution of current Pacific-North America motion across western North America and its margin, plate reconstructions and their uncertainties, hotspots, and plate dynamics. A comprehensive bibliography is provided. 126 refs.

  7. Development of Daily Maximum Flare-Flux Forecast Models for Strong Solar Flares

    NASA Astrophysics Data System (ADS)

    Shin, Seulki; Lee, Jin-Yi; Moon, Yong-Jae; Chu, Hyoungseok; Park, Jongyeob

    2016-03-01

    We have developed a set of daily maximum flare-flux forecast models for strong flares (M- and X-class) using multiple linear regression (MLR) and artificial neural network (ANN) methods. Our input parameters are solar-activity data from January 1996 to December 2013 such as sunspot area, X-ray maximum, and weighted total flare flux of the previous day, as well as mean flare rates of McIntosh sunspot group (Zpc) and Mount Wilson magnetic classifications. For a training dataset, we used 61 events each of C-, M-, and X-class from January 1996 to December 2004. For a testing dataset, we used all events from January 2005 to November 2013. A comparison between our maximum flare-flux models and NOAA model based on true skill statistics (TSS) shows that the MLR model for X-class and the average of all flares (M{+}X-class) are much better than the NOAA model. According to the hitting fraction (HF), which is defined as a fraction of events satisfying the condition that the absolute differences of predicted and observed flare flux on a logarithm scale are smaller than or equal to 0.5, our models successfully forecast the maximum flare flux of about two-thirds of the events for strong flares. Since all input parameters for our models are easily available, the models can be operated steadily and automatically on a daily basis for space-weather services.

  8. Xrt And Shinx Joint Flare Study: Ar 11024

    NASA Astrophysics Data System (ADS)

    Engell, Alexander; Sylwester, J.; Siarkowski, M.

    2010-05-01

    From 12:00 UT on July 3 through July 7, 2009 SphinX (Solar Photometer IN X-rays) observes 130 flares with active region (AR) 11024 being the only AR on disk. XRT (X-Ray Telescope) is able to observe 64 of these flare events. The combination of both instruments results in a flare study revealing (1) a relationship between flux emergence and flare rate, (2) that the presence of active region loops typically results in different flare morphologies (single and multiple loop flares) then when there is a lack of an active region loop environment where more cusp and point-like flares are observed, (3) cusp and point-like flares often originate from the same location, and (4) a distribution of flare temperatures corresponding to the different flare morphologies. The differences between the observed flare morphologies may occur as the result of the heated plasma through the flaring process being confined by the proximity of loop structures as for the single and multiple loop flares, while for cusp and point-like flares they occur in an early-phase environment that lack loop presence. The continuing flux emergence of AR 11024 likely provides different magnetic interactions and may be the source responsible for all of the flares.

  9. Temporal and Spatial Relationship of Flare Signatures and the Force-free Coronal Magnetic Field

    NASA Astrophysics Data System (ADS)

    Thalmann, J. K.; Veronig, A.; Su, Y.

    2016-08-01

    We investigate the plasma and magnetic environment of active region NOAA 11261 on 2011 August 2 around a GOES M1.4 flare/CME (SOL2011-08-02T06:19). We compare coronal emission at the (extreme) ultraviolet and X-ray wavelengths, using SDO AIA and RHESSI images, in order to identify the relative timing and locations of reconnection-related sources. We trace flare ribbon signatures at ultraviolet wavelengths in order to pin down the intersection of previously reconnected flaring loops in the lower solar atmosphere. These locations are used to calculate field lines from three-dimensional (3D) nonlinear force-free magnetic field models, established on the basis of SDO HMI photospheric vector magnetic field maps. Using this procedure, we analyze the quasi-static time evolution of the coronal model magnetic field previously involved in magnetic reconnection. This allows us, for the first time, to estimate the elevation speed of the current sheet’s lower tip during an on-disk observed flare as a few kilometers per second. A comparison to post-flare loops observed later above the limb in STEREO EUVI images supports this velocity estimate. Furthermore, we provide evidence for an implosion of parts of the flaring coronal model magnetic field, and identify the corresponding coronal sub-volumes associated with the loss of magnetic energy. Finally, we spatially relate the build up of magnetic energy in the 3D models to highly sheared fields, established due to the dynamic relative motions of polarity patches within the active region.

  10. AR1429 Releases X1 Class Flare

    NASA Video Gallery

    The Solar Dynamics Observatory captured the X1 flare, shown here in the 171 Angstrom wavelength, a wavelength typically shown in the color gold. This movie runs from 10 PM ET March 4 to 3 AM March ...

  11. Solar Eruptions: Coronal Mass Ejections and Flares

    NASA Technical Reports Server (NTRS)

    Gopalswamy, Nat

    2012-01-01

    This lecture introduces the topic of Coronal mass ejections (CMEs) and solar flares, collectively known as solar eruptions. During solar eruptions, the released energy flows out from the Sun in the form of magnetized plasma and electromagnetic radiation. The electromagnetic radiation suddenly increases the ionization content of the ionosphere, thus impacting communication and navigation systems. Flares can be eruptive or confined. Eruptive flares accompany CMEs, while confined flares hav only electromagnetic signature. CMEs can drive MHD shocks that accelerate charged particles to very high energies in the interplanetary space, which pose radiation hazard to astronauts and space systems. CMEs heading in the direction of Earth arrive in about two days and impact Earth's magnetosphere, producing geomagnetic storms. The magnetic storms result in a number of effects including induced currnts that can disrupt power grids, railroads, and underground pipelines

  12. 2011 Valentines Day X-Class Flare

    NASA Video Gallery

    The video clip of the large X2 flare seen by Solar Dynamics Observatory (SDO) in extreme ultraviolet light on February 15, 2011, has been enlarged and superimposed on a video of SOHO's C2 coronagra...

  13. Neutral pion production in solar flares

    NASA Technical Reports Server (NTRS)

    Forrest, D. J.; Vestrand, W. T.; Chupp, E. L.; Rieger, E.; Cooper, J. F.; Share, G. H.

    1985-01-01

    The Gamma-Ray Spectrometer (GRS) on SMM has detected more than 130 flares with emission approx 300 keV. More than 10 of these flares were detected at photon energies 10 MeV. Although the majority of the emission at 10 MeV must be from electron bremsstrahlung, at least two of the flares have spectral properties 40 MeV that require gamma rays from the decay of neutral pions. It is found that pion production can occur early in the impulsive phase as defined by hard X-rays near 100 keV. It is also found in one of these flares that a significant portion of this high-energy emission is produced well after the impulsive phase. This extended production phase, most clearly observed at high energies, may be a signature of the acceleration process which produces solar energetic particles (SEP's) in space.

  14. SDO Sees Late Phase in Solar Flares

    NASA Video Gallery

    On May 5, 2010, shortly after the Solar Dynamics Observatory (SDO) began normal operation, the sun erupted with numerous coronal loops and flares. Many of these showed a previously unseen "late pha...

  15. C3-class Solar Flare Eruption

    NASA Video Gallery

    Just as sunspot 1105 was turning away from Earth on Sept. 8, the active region erupted, producing a C3-class solar flare (peak @ 2330 UT) and a fantastic prominence. This is a three color closeup o...

  16. Magnetic Variations Associated With Solar Flares

    NASA Technical Reports Server (NTRS)

    Petrosian, Vahe

    2005-01-01

    A report summarizes an investigation of helioseismic waves and magnetic variations associated with solar flares, involving analysis of data acquired by the Michelson Doppler Imager (MDI) aboard the Solar and Heliocentric Observatory (SOHO) spacecraft, the Yohkoh spacecraft, and the Ramaty High Energy Solar Spectroscopic Imager (RHESSI) spacecraft. Reconstruction of x-ray flare images from RHESSI data and comparison of them with MDI magnetic maps were performed in an attempt to infer the changes in the geometry of the magnetic field. It was established that in most flares observed with MDI, downward propagating shocks were much weaker than was one observed in the July 9, 1996 flare, which caused a strong helioseismic response. It was concluded that most of the observed impulsive variations result from direct impact of high-energy particles. Computer codes were developed for further study of these phenomena.

  17. Magnetic Fields in Limb Solar Flares

    NASA Astrophysics Data System (ADS)

    Lozitsky, V. G.; Lozitska, N. I.; Botygina, O. A.

    2013-02-01

    Two limb solar flares, of 14 July 2005 and 19 July 2012, of importance X1.2 and M7.7, are analyzed at present work. Magnetic field strength in named flares are investigated by Stokes I±V profiles of Hα and D3 HeI lines. There are direct evidences to the magnetic field inhomogeneity in flares, in particular, non-paralelism of bisectors in I+V and I-V profiles. In some flare places, the local maximums of bisectors splitting were found in both lines. If these bisector splittings are interpreted as Zeeman effect manifestation, the following magnetic field strengths reach up to 2200 G in Hα and 1300 G in D3. According to calculations, the observed peculiarities of line profiles may indicate the existence of optically thick emissive small-scale elements with strong magnetic fields and lowered temperature.

  18. Evidence for a relationship between emerging magnetic fields, electric currents, and solar flares observed on May 10, 2012

    NASA Astrophysics Data System (ADS)

    Livshits, M. A.; Grigoryeva, I. Yu.; Myshyakov, I. I.; Rudenko, G. V.

    2016-10-01

    Multi-wavelength observations and magnetic-field data for the solar flare of May 10, 2012 (04: 18 UT) are analyzed. A sign change in the line-of-sight magnetic field in the umbra of a small spot has been detected. This is at least partly associated with the emergence of a new magnetic field. A hard X-ray flare was recorded at almost the same time, and a "sunquake" was generated by the impact of the disturbance in the range of energy release on the photosphere. A sigmoid flare was recorded at the beginning of the event, but did not spread, as it usually does, along the polarity inversion (neutral) line. SDO/HMI full vectormagnetic-fieldmeasurements are used to extrapolate the magnetic field of AR 11476 into the corona, and to derive the distribution of vertical currents jz in the photosphere. The relationship between the distribution of currents in the active region and the occurrence of flares is quite complex. The expected "ideal" behavior of the current system before and after the flare (e.g., described by Sharykin and Kosovichev) is observed only in the sigmoid region. The results obtained are compared with observations of two other flares recorded in this active region on the same day, one similar to the discussed flare and the other different. The results confirm that the formation and eruption of large-scale magnetic flux ropes in sigmoid flares is associated with shear motions in the photosphere, the emergence of twisted magnetic tubes, and the subsequent development of the torus instability.

  19. Observations of an X-shaped Ribbon Flare and Its Three-dimensional Magnetic Reconnection with IRIS and SDO

    NASA Astrophysics Data System (ADS)

    Li, Ying; Qiu, Jiong; Longcope, Dana; Ding, Mingde

    2016-05-01

    We report evolution of an atypical X-shaped flare ribbon which provides novel observational evidence of three-dimensional (3D) magnetic reconnection at a separator. The flare occurred on 2014 November 9, and high-resolution slit-jaw 1330 images from IRIS reveal four chromospheric flare ribbons that converge and form an X-shape. These four ribbons are located in a quadrupolar magnetic field. Reconstruction of magnetic topology in the active region suggests the presence of a separator connecting to the X-point outlined by the ribbons. The inward motion of flare ribbons, as well as coronal loops observed by the SDO/AIA, indicates 3D magnetic reconnection between two sets of non-coplanar loops that approach laterally, and the reconnection proceeds downward to a very low height. We also study spectra of Si IV, C II, and Mg II observed with the IRIS slit, which cuts across the flare ribbons near the X-point. We have found two distinct types of line profiles. At the flare ribbon, all the lines show evident redshifts with a velocity up to 50 km/s, and the redshifts are well correlated with the line intensity and width. These redshifts suggest chromospheric condensation caused by impulsive energy deposition from the separator reconnection. While right outside the flare ribbon, the lines exhibit unshifted, symmetric, yet broadened profiles; in particular, the Si IV line is significantly broadened at the far wing. The line broadening persists for 20 minutes till after the end of the flare. The distinct spectral features near the X-point indicate different dynamics associated with the separator reconnection.

  20. Reconnection in substorms and solar flares: analogies and differences

    SciTech Connect

    Birn, Joachim

    2008-01-01

    Magnetic reconnection is the crucial process in the release of magnetic energy associated with magnetospheric substorms and with solar flares. On the basis of three-dimensional resistive MHD simulations we investigate similarities and differences between the two scenarios. We address in particular mechanisms that lead to the onset of reconnection and on energy release, transport, and conversion mechanisms. Analogous processes might exist in the motion of field line footpoints on the sun and in magnetic flux addition to the magnetotail. In both cases such processes might lead to a loss of neighboring equilibrium, characterized by the formation of very thin embedded current sheet, which acts as trigger for reconnection. We find that Joule (or ohmic) dissipation plays only a minor role in the overall energy transfer associated with reconnection. The dominant transfer of released magnetic energy occurs to electromagnetic energy (Poynting) flux and to thermal energy transport as enthalpy flux. The former dominates in low-beta, specifically initially force-free current sheets expected for the solar corona, while the latter dominates in high-beta current sheets, such as the magnetotail. In both cases the outflow from the reconnection site becomes bursty, i.e. spatially and temporally localized, yet carrying most of the outflow energy. Hence an analogy might exist between bursty bulk flows (BBFs) in the magnetotail and pulses of Poynting flux in solar flares.

  1. Can we explain atypical solar flares?

    NASA Astrophysics Data System (ADS)

    Dalmasse, K.; Chandra, R.; Schmieder, B.; Aulanier, G.

    2015-02-01

    Context. We used multiwavelength high-resolution data from ARIES, THEMIS, and SDO instruments to analyze a non-standard, C3.3 class flare produced within the active region NOAA 11589 on 2012 October 16. Magnetic flux emergence and cancellation were continuously detected within the active region, the latter leading to the formation of two filaments. Aims: Our aim is to identify the origins of the flare taking the complex dynamics of its close surroundings into account. Methods: We analyzed the magnetic topology of the active region using a linear force-free field extrapolation to derive its 3D magnetic configuration and the location of quasi-separatrix layers (QSLs), which are preferred sites for flaring activity. Because the active region's magnetic field was nonlinear force-free, we completed a parametric study using different linear force-free field extrapolations to demonstrate the robustness of the derived QSLs. Results: The topological analysis shows that the active region presented a complex magnetic configuration comprising several QSLs. The considered data set suggests that an emerging flux episode played a key role in triggering the flare. The emerging flux probably activated the complex system of QSLs, leading to multiple coronal magnetic reconnections within the QSLs. This scenario accounts for the observed signatures: the two extended flare ribbons developed at locations matched by the photospheric footprints of the QSLs and were accompanied with flare loops that formed above the two filaments, which played no important role in the flare dynamics. Conclusions: This is a typical example of a complex flare that can a priori show standard flare signatures that are nevertheless impossible to interpret with any standard model of eruptive or confined flare. We find that a topological analysis, however, permitted us to unveil the development of such complex sets of flare signatures. Movies associated to Figs. 1, 3, and 9 are only available at the CDS via

  2. INITIATION OF CORONAL MASS EJECTION AND ASSOCIATED FLARE CAUSED BY HELICAL KINK INSTABILITY OBSERVED BY SDO/AIA

    SciTech Connect

    Kumar, Pankaj; Cho, K.-S.; Bong, S.-C.; Park, Sung-Hong; Kim, Y. H.

    2012-02-10

    In this paper, we present multiwavelength observations of helical kink instability as a trigger of a coronal mass ejection (CME) which occurred in active region NOAA 11163 on 2011 February 24. The CME was associated with an M3.5 limb flare. High-resolution observations from the Solar Dynamics Observatory/Atmospheric Imaging Assembly suggest the development of helical kink instability in the erupting prominence, which implies a flux rope structure of the magnetic field. A brightening starts below the apex of the prominence with its slow rising motion ({approx}100 km s{sup -1}) during the activation phase. A bright structure, indicative of a helix with {approx}3-4 turns, was transiently formed at this position. The corresponding twist of {approx}6{pi}-8{pi} is sufficient to generate the helical kink instability in a flux rope according to recently developed models. A slowly rising blob structure was subsequently formed at the apex of the prominence, and a flaring loop was observed near the footpoints. Within 2 minutes, a second blob was formed in the northern prominence leg. The second blob erupts (like a plasmoid ejection) with the detachment of the northern prominence leg, and flare intensity maximizes. The first blob at the prominence apex shows rotational motion in the counterclockwise direction in the plane of sky, interpreted as the unwinding motion of a helix, and it also erupts to give the CME. RHESSI hard X-ray (HXR) sources show the two footpoint sources and a loop-top source during the flare. We found RHESSI HXR flux, soft X-ray flux derivative, and CME acceleration in the low corona correlate well, which is in agreement with the standard flare model (CSHKP). We also discuss the possible role of ballooning as well as torus instabilities in driving the CME. We conclude that the CME and flare were triggered by the helical kink instability in a flux rope and accelerated mainly by the torus instability.

  3. Optically thick line widths in pyrotechnic flares

    NASA Technical Reports Server (NTRS)

    Douda, B. E.; Exton, R. J.

    1975-01-01

    Experimentally determined sodium line widths for pyrotechnic flares are compared with simple analytical, optically-thick-line-shape calculations. Three ambient pressure levels are considered (760, 150 and 30 torr) for three different flare compositions. The measured line widths range from 1.3 to 481 A. The analytic procedure emphasizes the Lorentz line shape as observed under optically-thick conditions. Calculated widths are in good agreement with the measured values over the entire range.

  4. Composition of energetic particles from solar flares.

    PubMed

    Garrard, T L; Stone, E C

    1994-10-01

    We present a model for composition of heavy ions in the solar energetic particles (SEP). The SEP composition in a typical large solar particle event reflects the composition of the Sun, with adjustments due to fractionation effects which depend on the first ionization potential (FIP) of the ion and on the ratio of ionic charge to mass (Q/M). Flare-to-flare variations in composition are represented by parameters describing these fractionation effects and the distributions of these parameters are presented.

  5. Global ionospheric flare detection system (GIFDS)

    NASA Astrophysics Data System (ADS)

    Wenzel, Daniela; Jakowski, Norbert; Berdermann, Jens; Mayer, Christoph; Valladares, Cesar; Heber, Bernd

    2016-02-01

    The Global Ionospheric Flare Detection System (GIFDS) is currently under development at the German Aerospace Center as a ground based detector for continuous monitoring of the solar flare activity in order to provide real time warnings on solar X-ray events. GIFDS is using Very Low Frequency (VLF) radio transmissions in the northern hemisphere which respond to enhanced ionization in the bottomside ionosphere caused by X-ray flares. Since solar flares can only be detected during daytime, VLF receivers have to be installed around the globe to guarantee continuous records at the dayside sector. GIFDS consists of a network of Perseus SDR (Software Defined Radio) receivers equipped with a MiniWhip antenna each. Reliable detection of solar flares is ensured by recording multiple frequency channels ranging from 0 to 500 kHz. The applicability of the system is demonstrated in a first analysis by comparing VLF measurements with GOES's (Geostationary Operational Environmental Satellite) X-ray flux data. The high potential of GIFDS for a permanent monitoring of solar flares in near real time is discussed.

  6. The energy spectra of solar flare electrons

    NASA Technical Reports Server (NTRS)

    Evenson, P. A.; Hovestadt, D.; Meyer, P.; Moses, D.

    1985-01-01

    A survey of 50 electron energy spectra from .1 to 100 MeV originating from solar flares was made by the combination of data from two spectrometers onboard the International Sun Earth Explorer-3 spacecraft. The observed spectral shapes of flare events can be divided into two classes through the criteria of fit to an acceleration model. This standard two step acceleration model, which fits the spectral shape of the first class of flares, involves an impulsive step that accelerates particles up to 100 keV and a second step that further accelerates these particles up to 100 MeV by a single shock. This fit fails for the second class of flares that can be characterized as having excessively hard spectra above 1 MeV relative to the predictions of the model. Correlations with soft X-ray and meter radio observations imply that the acceleration of the high energy particles in the second class of flares is dominated by the impulsive phase of the flares.

  7. Observational Evidence of Particle Acceleration Associated with Plasmoid Motions

    NASA Astrophysics Data System (ADS)

    Takasao, Shinsuke; Asai, Ayumi; Isobe, Hiroaki; Shibata, Kazunari

    2016-09-01

    We report a strong association between the particle acceleration and plasma motions found in the 2010 August 18 solar flare. The plasma motions are tracked in the extreme ultraviolet (EUV) images taken by the Atmospheric Imaging Assembly (AIA) on board the Solar Dynamics Observatory and the Extreme UltraViolet Imager (EUVI) on the Solar Terrestrial Relations Observatory spacecraft Ahead, and the signature of particle acceleration was investigated by using Nobeyama Radioheliograph data. In our previous paper, we reported that in EUV images many plasma blobs appeared in the current sheet above the flare arcade. They were ejected bidirectionally along the current sheet, and the blobs that were ejected sunward collided with the flare arcade. Some of them collided or merged with each other before they were ejected from the current sheet. We discovered impulsive radio bursts associated with such plasma motions (ejection, coalescence, and collision with the post flare loops). The radio bursts are considered to be the gyrosynchrotron radiation by nonthermal high energy electrons. In addition, the stereoscopic observation by AIA and EUVI suggests that plasma blobs had a three-dimensionally elongated structure. We consider that the plasma blobs were three-dimensional plasmoids (i.e., flux ropes) moving in a current sheet. We believe that our observation provides clear evidence of particle acceleration associated with the plasmoid motions. We discuss possible acceleration mechanisms on the basis of our results.

  8. Using Two-Ribbon Flare Observations and MHD Simulations to Constrain Flare Properties

    NASA Astrophysics Data System (ADS)

    Kazachenko, Maria D.; Lynch, Benjamin J.; Welsch, Brian

    2016-05-01

    Flare ribbons are emission structures that are frequently observed during flares in transition-region and chromospheric radiation. These typically straddle a polarity inversion line (PIL) of the radial magnetic field at the photosphere, and move apart as the flare progresses. The ribbon flux - the amount of unsigned photospheric magnetic flux swept out by flare ribbons - is thought to be related to the amount coronal magnetic reconnection, and hence provides a key diagnostic tool for understanding the physical processes at work in flares and CMEs. Previous measurements of the magnetic flux swept out by flare ribbons required time-consuming co-alignment between magnetograph and intensity data from different instruments, explaining why those studies only analyzed, at most, a few events. The launch of the Helioseismic and Magnetic Imager (HMI) and the Atmospheric Imaging Assembly (AIA), both aboard the Solar Dynamics Observatory (SDO), presented a rare opportunity to compile a much larger sample of flare-ribbon events than could readily be assembled before. We created a dataset of 363 events of both flare ribbon positions and fluxes, as a function of time, for all C9.-class and greater flares within 45 degrees of disk center observed by SDO from June 2010 till April 2015. For this purpose, we used vector magnetograms (2D magnetic field maps) from HMI and UV images from AIA. A critical problem with using unprocessed AIA data is the existence of spurious intensities in AIA data associated with strong flare emission, most notably "blooming" (spurious smearing of saturated signal into neighboring pixels, often in streaks). To overcome this difficulty, we have developed an algorithmic procedure that effectively excludes artifacts like blooming. We present our database and compare statistical properties of flare ribbons, e.g. evolutions of ribbon reconnection fluxes, reconnection flux rates and vertical currents with the properties from MHD simulations.

  9. Effects of flare definitions on the statistics of derived flare distributions

    NASA Astrophysics Data System (ADS)

    Ryan, D. F.; Dominique, M.; Seaton, D.; Stegen, K.; White, A.

    2016-08-01

    The statistical examination of solar flares is crucial to revealing their global characteristics and behaviour. Such examinations can tackle large-scale science questions or give context to detailed single-event studies. However, they are often performed using standard but basic flare detection algorithms relying on arbitrary thresholds. This arbitrariness may lead to important scientific conclusions being drawn from results caused by subjective choices in algorithms rather than the true nature of the Sun. In this paper, we explore the effect of the arbitrary thresholds used in the Geostationary Operational Environmental Satellite (GOES) event list and Large Yield RAdiometer (LYRA) Flare Finder algorithms. We find that there is a small but significant relationship between the power law exponent of the GOES flare peak flux frequency distribution and the flare start thresholds of the algorithms. We also find that the power law exponents of these distributions are not stable, but appear to steepen with increasing peak flux. This implies that the observed flare size distribution may not be a power law at all. We show that depending on the true value of the exponent of the flare size distribution, this deviation from a power law may be due to flares missed by the flare detection algorithms. However, it is not possible determine the true exponent from GOES/XRS observations. Additionally we find that the PROBA2/LYRA flare size distributions are artificially steep and clearly non-power law. We show that this is consistent with an insufficient degradation correction. This means that PROBA2/LYRA should not be used for flare statistics or energetics unless degradation is adequately accounted for. However, it can be used to study variations over shorter timescales and for space weather monitoring.

  10. Motion sickness.

    PubMed

    Golding, J F

    2016-01-01

    Over 2000 years ago the Greek physician Hippocrates wrote, "sailing on the sea proves that motion disorders the body." Indeed, the word "nausea" derives from the Greek root word naus, hence "nautical," meaning a ship. The primary signs and symptoms of motion sickness are nausea and vomiting. Motion sickness can be provoked by a wide variety of transport environments, including land, sea, air, and space. The recent introduction of new visual technologies may expose more of the population to visually induced motion sickness. This chapter describes the signs and symptoms of motion sickness and different types of provocative stimuli. The "how" of motion sickness (i.e., the mechanism) is generally accepted to involve sensory conflict, for which the evidence is reviewed. New observations concern the identification of putative "sensory conflict" neurons and the underlying brain mechanisms. But what reason or purpose does motion sickness serve, if any? This is the "why" of motion sickness, which is analyzed from both evolutionary and nonfunctional maladaptive theoretic perspectives. Individual differences in susceptibility are great in the normal population and predictors are reviewed. Motion sickness susceptibility also varies dramatically between special groups of patients, including those with different types of vestibular disease and in migraineurs. Finally, the efficacy and relative advantages and disadvantages of various behavioral and pharmacologic countermeasures are evaluated. PMID:27638085

  11. Brownian motion

    NASA Astrophysics Data System (ADS)

    Lavenda, B. H.

    1985-02-01

    Brownian motion, the doubly random motion of small particles suspended in a liquid due to molecular collisions, and its implications and applications in the history of modern science are discussed. Topics examined include probabilistic phenomena, the kinetic theory of gases, Einstein's atomic theory of Brownian motion, particle displacement, diffusion measurements, the determination of the mass of the atom and of Avogadro's number, the statistical mechanics of thermodynamics, nonequilibrium systems, Langevin's equation of motion, time-reversed evolution, mathematical analogies, and applications in economics and radio navigation. Diagrams and drawings are provided.

  12. Feasibility of flare gas reformation to practical energy in Farashband gas refinery: no gas flaring.

    PubMed

    Rahimpour, Mohammad Reaza; Jokar, Seyyed Mohammad

    2012-03-30

    A suggested method for controlling the level of hazardous materials in the atmosphere is prevention of combustion in flare. In this work, three methods are proposed to recover flare gas instead of conventional gas-burning in flare at the Farashband gas refinery. These methods aim to minimize environmental and economical disadvantages of burning flare gas. The proposed methods are: (1) gas to liquid (GTL) production, (2) electricity generation with a gas turbine and, (3) compression and injection into the refinery pipelines. To find the most suitable method, the refinery units that send gas to the flare as well as the required equipment for the three aforementioned methods are simulated. These simulations determine the amount of flare gas, the number of GTL barrels, the power generated by the gas turbine and the required compression horsepower. The results of simulation show that 563 barrels/day of valuable GTL products is produced by the first method. The second method provides 25 MW electricity and the third method provides a compressed natural gas with 129 bar pressure for injection to the refinery pipelines. In addition, the economics of flare gas recovery methods are studied and compared. The results show that for the 4.176MMSCFD of gas flared from the Farashband gas refinery, the electricity production gives the highest rate of return (ROR), the lowest payback period, the highest annual profit and mild capital investment. Therefore, the electricity production is the superior method economically.

  13. Flare energetics: analysis of a large flare on YZ Canis Minoris observed simultaneously in the ultraviolet, optical and radio.

    NASA Astrophysics Data System (ADS)

    van den Oord, G. H. J.; Doyle, J. G.; Rodono, M.; Gary, D. E.; Henry, G. W.; Byrne, P. B.; Linsky, J. L.; Haisch, B. M.; Pagano, I.; Leto, G.

    1996-06-01

    The results of coordinated observations of the dMe star YZ CMi at optical, UV and radio wavelengths during 3-7 February 1983 are presented. YZ CMi showed repeated optical flaring with the largest flare having a magnitude of 3.8 in the U-band. This flare coincided with an IUE exposure which permits a comparison of the emission measure curves of YZ CMi in its flaring and quiescent state. During the flare a downward shift of the transition zone is observed while the radiative losses in the range 10^4^-10^7^K strongly increase. The optical flare is accompanied with a radio flare at 6cm, while at 20cm no emission is detected. The flare is interpreted in terms of optically thick synchrotron emission. We present a combined interpretation of the optical/radio flare and show that the flare can be interpreted within the context of solar two-ribbon/white-light flares. Special attention is paid to the bombardment of dMe atmospheres by particle beams. We show that the characteristic temperature of the heated atmosphere is almost independent of the beam flux and lies within the range of solar white-light flare temperatures. We also show that it is unlikely that stellar flares emit black-body spectra. The fraction of accelerated particles, as follows from our combined optical/radio interpretation is in good agreement with the fraction determined by two-ribbon flare reconnection models.

  14. TURBULENT DYNAMICS IN SOLAR FLARE SHEET STRUCTURES MEASURED WITH LOCAL CORRELATION TRACKING

    SciTech Connect

    McKenzie, D. E.

    2013-03-20

    High-resolution observations of the Sun's corona in extreme ultraviolet and soft X-rays have revealed a new world of complexity in the sheet-like structures connecting coronal mass ejections (CMEs) to the post-eruption flare arcades. This article presents initial findings from an exploration of dynamic flows in two flares observed with Hinode/XRT and SDO/AIA. The flows are observed in the hot ({approx}> 10 MK) plasma above the post-eruption arcades and measured with local correlation tracking. The observations demonstrate significant shears in velocity, giving the appearance of vortices and stagnations. Plasma diagnostics indicate that the plasma {beta} exceeds unity in at least one of the studied events, suggesting that the coronal magnetic fields may be significantly affected by the turbulent flows. Although reconnection models of eruptive flares tend to predict a macroscopic current sheet in the region between the CME and the flare arcade, it is not yet clear whether the observed sheet-like structures are identifiable as the current sheets or 'thermal halos' surrounding the current sheets. Regardless, the relationship between the turbulent motions and the embedded magnetic field is likely to be complicated, involving dynamic fluid processes that produce small length scales in the current sheet. Such processes may be crucial for triggering, accelerating, and/or prolonging reconnection in the corona.

  15. Reverse Current in Solar Flares

    NASA Technical Reports Server (NTRS)

    Knight, J. W., III

    1978-01-01

    An idealized steady state model of a stream of energetic electrons neutralized by a reverse current in the pre-flare solar plasma was developed. These calculations indicate that, in some cases, a significant fraction of the beam energy may be dissipated by the reverse current. Joule heating by the reverse current is a more effective mechanism for heating the plasma than collisional losses from the energetic electrons because the Ohmic losses are caused by thermal electrons in the reverse current which have much shorter mean free paths than the energetic electrons. The heating due to reverse currents is calculated for two injected energetic electron fluxes. For the smaller injected flux, the temperature of the coronal plasma is raised by about a factor of two. The larger flux causes the reverse current drift velocity to exceed the critical velocity for the onset of ion cyclotron turbulence, producing anomalous resistivity and an order of magnitude increase in the temperature. The heating is so rapid that the lack of ionization equilibrium may produce a soft X-ray and EUV pulse from the corona.

  16. An auroral flare at Jupiter.

    PubMed

    Waite, J H; Gladstone, G R; Lewis, W S; Goldstein, R; McComas, D J; Riley, P; Walker, R J; Robertson, P; Desai, S; Clarke, J T; Young, D T

    2001-04-12

    Jupiter's aurora is the most powerful in the Solar System. It is powered largely by energy extracted from planetary rotation, although there seems also to be a contribution from the solar wind. This contrasts with Earth's aurora, which is generated through the interaction of the solar wind with the magnetosphere. The major features of Jupiter's aurora (based on far-ultraviolet, near-infrared and visible-wavelength observations) include a main oval that generally corotates with the planet and a region of patchy, diffuse emission inside the oval on Jupiter's dusk side. Here we report the discovery of a rapidly evolving, very bright and localized emission poleward of the northern main oval, in a region connected magnetically to Jupiter's outer magnetosphere. The intensity of the emission increased by a factor of 30 within 70 s, and then decreased on a similar timescale, all captured during a single four-minute exposure. This type of flaring emission has not previously been reported for Jupiter (similar, but smaller, transient events have been observed at Earth), and it may be related directly to changes in the solar wind.

  17. Enclosed ground-flare incinerator

    DOEpatents

    Wiseman, Thomas R.

    2000-01-01

    An improved ground flare is provided comprising a stack, two or more burner assemblies, and a servicing port so that some of the burner assemblies can be serviced while others remain in operation. The burner assemblies comprise a burner conduit and nozzles which are individually fitted to the stack's burner chamber and are each removably supported in the chamber. Each burner conduit is sealed to and sandwiched between a waste gas inlet port and a matching a closure port on the other side of the stack. The closure port can be opened for physically releasing the burner conduit and supplying sufficient axial movement room for extracting the conduit from the socket, thereby releasing the conduit for hand removal through a servicing port. Preferably, the lower end of the stack is formed of one or more axially displaced lower tubular shells which are concentrically spaced for forming annular inlets for admitting combustion air. An upper tubular exhaust stack, similarly formed, admits additional combustion air for increasing the efficiency of combustion, increasing the flow of exhausted for improved atmospheric dispersion and for cooling the upper stack.

  18. Identifying flares in rheumatoid arthritis: reliability and construct validation of the OMERACT RA Flare Core Domain Set

    PubMed Central

    Bykerk, Vivian P; Bingham, Clifton O; Choy, Ernest H; Lin, Daming; Alten, Rieke; Christensen, Robin; Furst, Daniel E; Hewlett, Sarah; Leong, Amye; March, Lyn; Woodworth, Thasia; Boire, Gilles; Haraoui, Boulos; Hitchon, Carol; Jamal, Shahin; Keystone, Edward C; Pope, Janet; Tin, Diane; Thorne, J Carter

    2016-01-01

    Objective To evaluate the reliability of concurrent flare identification using 3 methods (patient, rheumatologist and Disease Activity Score (DAS)28 criteria), and construct validity of candidate items representing the Outcome Measures in Rheumatology Clinical Trials (OMERACT) RA Flare Core Domain Set. Methods Candidate flare questions and legacy measures were administered at consecutive visits to Canadian Early Arthritis Cohort (CATCH) patients between November 2011 and November 2014. The American College of Rheumatology (ACR) core set indicators were recorded. Concordance to identify flares was assessed using the agreement coefficient. Construct validity of flare questions was examined: convergent (Spearman's r); discriminant (mean differences between flaring/non-flaring patients); and consequential (proportions with prior treatment reductions and intended therapeutic change postflare). Results The 849 patients were 75% female, 81% white, 42% were in remission/low disease activity (R/LDA), and 16–32% were flaring at the second visit. Agreement of flare status was low–strong (κ's 0.17–0.88) and inversely related to RA disease activity level. Flare domains correlated highly (r's≥0.70) with each other, patient global (r's≥0.66) and corresponding measures (r's 0.49–0.92); and moderately highly with MD and patient-reported joint counts (r's 0.29–0.62). When MD/patients agreed the patient was flaring, mean flare domain between-group differences were 2.1–3.0; 36% had treatment reductions prior to flare, with escalation planned in 61%. Conclusions Flares are common in rheumatoid arthritis (RA) and are often preceded by treatment reductions. Patient/MD/DAS agreement of flare status is highest in patients worsening from R/LDA. OMERACT RA flare questions can discriminate between patients with/without flare and have strong evidence of construct and consequential validity. Ongoing work will identify optimal scoring and cut points to identify RA flares. PMID

  19. Detecting Solar Neutrino Flares and Flavors

    NASA Astrophysics Data System (ADS)

    Fargion, D.

    2004-06-01

    Most power-full solar flare as the ones occurred on 23th February 1956, September 29th 1989 and recent ones occurred on 28th October, on 2nd-4th and 13th November 2003 have been respectively recorded by Radio-X- and Cosmic Rays detectors. These flares took place most in the open or in the edge and in the hidden solar disk (as for the September 29th, 1989 beyond 105Wo and for last November 2003 flare events). The 4th November event was the most powerful X event in the highest known rank category X28. The observed and estimated total flare energy E = 1031-1033 erg should be a source also of a prompt secondary neutrino burst originated, by proton-proton-pion production on the sun itself; a more delayed and spread neutrino flux signal arise later on the terrestrial atmosphere. These first earliest prompt solar neutrino burst might be already recorde, in a few neutrino clustered events, in largest neutrino underground detectors as Super-Kamiokande one, in time correlation with the sharp X-Radio flare onset. Our first estimate at the Super-Kamiokande II Laboratory is found to be a few (1-5) events. Their discover (or absence) should constrains the solar flare acceleration, energetic and its inner environment. Any large neutrino flare event might even verify the expected neutrino flavour mixing leading to comparable electron- muon event as well as a comparable energy fluence and spectra. Rare Tau appearence by neutrino muon into tau conversion might also arise.

  20. SPECTROPOLARIMETRY OF C-CLASS FLARE FOOTPOINTS

    SciTech Connect

    Kleint, L.

    2012-04-01

    We investigate the decay phase of a C-class flare in full-Stokes imaging spectropolarimetry with quasi-simultaneous measurements in the photosphere (6302.5 A line) and in the chromosphere (8542 A line) with the IBIS instrument. We analyze data from two fields of view, each spanning about 40'' Multiplication-Sign 80'' and targeting the two footpoints of the flare. A region of interest is identified from V/I images: a patch of opposite polarity in the smaller sunspot's penumbra. We find unusual flows in this patch at photospheric levels: a Doppler shift of -4 km s{sup -1}, but also a possible radial inflow into the sunspot of 4 km s{sup -1}. Such patches seem to be common during flares, but only high-resolution observations allowed us to see the inflow, which may be related to future flares observed in this region. Chromospheric images show variable overlying emission and flows and unusual Stokes profiles. We also investigate the irregular penumbra, whose formation may be blocked by the opposite polarity patch and flux emergence. The 40 minute temporal evolution depicts the larger of the flare ribbons becoming fainter and changing its shape. Measurable photospheric magnetic fields remain constant and we do not detect flare energy transport down from the chromosphere. We find no clear indications of impact polarization in the 8542 A line. We cannot exclude the possibility of impact polarization, because weaker signals may be buried in the prominent Zeeman signatures or it may have been present earlier during the flare.

  1. FLARES PRODUCING WELL-ORGANIZED POST-FLARE ARCADES (SLINKIES) HAVE EARLY PRECURSORS

    SciTech Connect

    Ryutova, M. P.

    2011-06-01

    Exploding loop systems producing X-ray flares often, but not always, bifurcate into a long-living, well-organized system of multi-threaded loop arcades resembling solenoidal slinkies. The physical conditions that cause or prevent this process are not known. To address this problem, we examined most of the major (X-class) flares that occurred during the last decade and found that the flares that bifurcate into long-living slinky arcades have different signatures than those that do not 'produce' such structures. The most striking difference is that, in all cases of slinky formation, GOES high energy proton flux becomes significantly enhanced 10-24 hr before the flare occurs. No such effect was found prior to the 'non-slinky' flares. This fact may be associated with the difference between energy production by a given active region and the amount of energy required to bring the entire system into the form of well-organized, self-similar loop arcades. As an example illustrating the process of post-flare slinky formation, we present observations taken with the Hinode satellite, in several wavelengths, showing a time sequence of pre-flare and flare activity, followed by the formation of dynamically stable, well-organized structures. One of the important features revealed is that post-flare coronal slinky formation is preceded by scale invariant structure formation in the underlying chromosphere/transition region. We suggest that the observed regularities can be understood within the framework of self-organized critical dynamics characterized by scale invariant structure formation with critical parameters largely determined by energy saturation level. The observed regularities per se may serve as a long-term precursor of strong flares and may help to study predictability of system behavior.

  2. Short-term predictions of solar flares.

    NASA Astrophysics Data System (ADS)

    Burov, V. A.

    1990-02-01

    A review of present-day theoretical investigations of the problem of the accumulation and release of energy in solar flares permits advancing the opinion that only individual flare events are described by a concrete model and that a single model alone does not describe the entire diversity of flares. Consideration of the observational data does not permit claiming the existence of a single universal mechanism known today of flare events. It appears possible to treat the problem of prediction in terms of the algebra of logic (Boolean logic) and to compare the truth table with the often-used contingency table. The introduction of a number of very general assumptions permits forming a general approach to the development of predictive schemes and selection of the individual elements of the models and informative criteria. Experimental results are given on the testing of some prediction procedures. The author's procedure of routine short-term prediction of flares on the basis of the methods of instruction on pattern recognition implemented in the form of a set of programs is outlined. The results of the application of this procedure in 1986 - 1988 are presented.

  3. Characteristics of energetic solar flare electron spectra

    NASA Technical Reports Server (NTRS)

    Moses, Dan; Droege, Wolfgang; Meyer, Peter; Evenson, Paul

    1989-01-01

    A 55 event survey of energy spectra of 0.1-100 MeV interplanetary electrons originating from solar flares as measured by two spectrometers onboard the ISEE 3 (ICE) spacecraft for the years 1978-1982 has been completed. Spectra generated using the maximum flux of a given event in each energy channel were restricted to events with a well-defined flux rise time. Two broad groups of electron spectra are considered. In one group, the spectra are well represented by a single power law in rigidity with spectral index in the range 3-4.5. The spectra in the other group deviate from a power law in rigidity systematically in that they harden with increasing rigidity. Events with near power-law spectra are found to be correlated with long-duration soft X-ray events, whereas those with hardening spectra are correlated with short-duration events. The possible variation of acceleration and propagation processes with the properties of the flare site is discussed, using the duration of the soft X-ray flare emission as an indicator of the physical parameters of the flare site (flare volume, density, coronal height, and magnetic field geometry).

  4. Radiative transfer simulations of magnetar flare beaming

    NASA Astrophysics Data System (ADS)

    van Putten, T.; Watts, A. L.; Baring, M. G.; Wijers, R. A. M. J.

    2016-09-01

    Magnetar giant flares show oscillatory modulations in the tails of their light curves, which can only be explained via some form of beaming. The fireball model for magnetar bursts has been used successfully to fit the phase-averaged light curves of the tails of giant flares, but so far no attempts have been made to fit the pulsations. We present a relatively simple numerical model to simulate beaming of magnetar flare emission. In our simulations, radiation escapes from the base of a fireball trapped in a dipolar magnetic field, and is scattered through the optically thick magnetosphere of the magnetar until it escapes. Beaming is provided by the presence of a relativistic outflow, as well as by the geometry of the system. We find that a simple picture for the relativistic outflow is enough to create the pulse fraction and sharp peaks observed in pulse profiles of magnetar flares, while without a relativistic outflow the beaming is insufficient to explain giant flare rotational modulations.

  5. An MHD model for magnetar giant flares

    SciTech Connect

    Meng, Y.; Lin, J.; Zhang, Q. S.; Zhang, L.; Reeves, K. K.; Yuan, F. E-mail: jlin@ynao.ac.cn

    2014-04-10

    Giant flares on soft gamma-ray repeaters that are thought to take place on magnetars release enormous energy in a short time interval. Their power can be explained by catastrophic instabilities occurring in the magnetic field configuration and the subsequent magnetic reconnection. By analogy with the coronal mass ejection events on the Sun, we develop a theoretical model via an analytic approach for magnetar giant flares. In this model, the rotation and/or displacement of the crust causes the field to twist and deform, leading to flux rope formation in the magnetosphere and energy accumulation in the related configuration. When the energy and helicity stored in the configuration reach a threshold, the system loses its equilibrium, the flux rope is ejected outward in a catastrophic way, and magnetic reconnection helps the catastrophe develop to a plausible eruption. By taking SGR 1806–20 as an example, we calculate the free magnetic energy released in such an eruptive process and find that it is more than 10{sup 47} erg, which is enough to power a giant flare. The released free magnetic energy is converted into radiative energy, kinetic energy, and gravitational energy of the flux rope. We calculated the light curves of the eruptive processes for the giant flares of SGR 1806–20, SGR 0526–66, and SGR 1900+14, and compared them with the observational data. The calculated light curves are in good agreement with the observed light curves of giant flares.

  6. 46 CFR 117.68 - Distress flares and smoke signals.

    Code of Federal Regulations, 2012 CFR

    2012-10-01

    .... (1) A rocket parachute flare approved in accordance with § 160.036 in subchapter Q of this chapter... section: (i) A rocket parachute flare approved in accordance with § 160.036 in subchapter Q of...

  7. 46 CFR 117.68 - Distress flares and smoke signals.

    Code of Federal Regulations, 2014 CFR

    2014-10-01

    .... (1) A rocket parachute flare approved in accordance with § 160.036 in subchapter Q of this chapter... section: (i) A rocket parachute flare approved in accordance with § 160.036 in subchapter Q of...

  8. 46 CFR 180.68 - Distress flares and smoke signals.

    Code of Federal Regulations, 2014 CFR

    2014-10-01

    ...) Substitutions. (1) A rocket parachute flare approved in accordance with § 160.036 in subchapter Q of this... section: (i) A rocket parachute flare approved in accordance with § 160.036 in subchapter Q of...

  9. 46 CFR 180.68 - Distress flares and smoke signals.

    Code of Federal Regulations, 2010 CFR

    2010-10-01

    ...) Substitutions. (1) A rocket parachute flare approved in accordance with § 160.036 in subchapter Q of this... section: (i) A rocket parachute flare approved in accordance with § 160.036 in subchapter Q of...

  10. 46 CFR 180.68 - Distress flares and smoke signals.

    Code of Federal Regulations, 2013 CFR

    2013-10-01

    ...) Substitutions. (1) A rocket parachute flare approved in accordance with § 160.036 in subchapter Q of this... section: (i) A rocket parachute flare approved in accordance with § 160.036 in subchapter Q of...

  11. 46 CFR 117.68 - Distress flares and smoke signals.

    Code of Federal Regulations, 2011 CFR

    2011-10-01

    .... (1) A rocket parachute flare approved in accordance with § 160.036 in subchapter Q of this chapter... section: (i) A rocket parachute flare approved in accordance with § 160.036 in subchapter Q of...

  12. X-Class: A Guide to Solar Flares

    NASA Video Gallery

    Solar flares are classified according to their strength. The smallest ones are B-class, followed by C, M and X, the largest. A powerful X-class flare can create long lasting radiation storms, which...

  13. The Origin of the Solar Flare Waiting-Time Distribution.

    PubMed

    Wheatland

    2000-06-20

    It was recently pointed out that the distribution of times between solar flares (the flare waiting-time distribution) follows a power law for long waiting times. Based on 25 years of soft X-ray flares observed by Geostationary Operational Environmental Satellite instruments, it is shown that (1) the waiting-time distribution of flares is consistent with a time-dependent Poisson process and (2) the fraction of time the Sun spends with different flaring rates approximately follows an exponential distribution. The second result is a new phenomenological law for flares. It is shown analytically how the observed power-law behavior of the waiting times originates in the exponential distribution of flaring rates. These results are argued to be consistent with a nonstationary avalanche model for flares.

  14. Core and Large-Scale Structure of the 2000 November 24 X-Class Flare and Coronal Mass Ejection

    NASA Technical Reports Server (NTRS)

    Wang, Haimin; Gallagher, Peter; Yurchyshyn, Vasyl; Yang, Guo; Godde, Philip R.

    2002-01-01

    In this paper, we present three important aspects of the XI .8 flare and the associated coronal mass ejection (CME) that occurred on 2000 November 24: (1) The source of the flare is clearly associated with a magnetic channel structure, as was noted in a study by Zirin & Wang , which is due to a combination of flux emergence inside the leading edge of the penumbra of the major leading sunspot and proper motion of the sunspot group. The channel structure provides evidence for twisted flux ropes that can erupt, forming the core of a CME, and may be a common property of several superactive regions that have produced multiple X-class flares in the past. (2) There are actually three flare ribbons visible. The first can be seen moving away from the flare site, while the second and third make up a stationary ribbon near the leader spot. The moving ribbons could be due to a shock associated with the erupting flux rope or due to the interaction of erupting rope and the surrounding magnetic fields. In either case, the ribbon motion does not fit the classical Kopp-Pneuman model, in which the separation of ribbons is due to magnetic reconnection at successively higher and higher coronal altitudes. (3) From the coronal dimming observed with the EUV Imaging Telescope (EIT), the CME involved a much larger region than the initial X-class flare. By comparing high-resolution full-disk Ha and EIT observations, we found that a remote dimming area is cospatial with the enhanced Ha emission. This result is consistent with the recent model of Yokoyama & Shibata that some dimming areas near footpoints may be due to chromospheric evaporation.

  15. THE RELATIONSHIP BETWEEN HARD X-RAY PULSE TIMINGS AND THE LOCATIONS OF FOOTPOINT SOURCES DURING SOLAR FLARES

    SciTech Connect

    Inglis, A. R.; Dennis, B. R.

    2012-04-01

    The cause of quasi-periodic pulsations in solar flares remains the subject of debate. Recently, Nakariakov and Zimovets proposed a new model suggesting that, in two-ribbon flares, such pulsations could be explained by propagating slow waves. These waves may travel obliquely to the magnetic field, reflect in the chromosphere, and constructively interfere at a spatially separate site in the corona, leading to quasi-periodic reconnection events progressing along the flaring arcade. Such a slow wave regime would have certain observational characteristics. We search for evidence of this phenomenon during a selection of two-ribbon flares observed by the Reuven Ramaty High Energy Solar Spectroscopic Imager, Solar and Heliospheric Observatory, and Transition Region and Coronal Explorer; the flares of 2002 November 9, 2005 January 19, and 2005 August 22. We were not able to observe a clear correlation between hard X-ray footpoint separations and pulse timings during these events. Also, the motion of hard X-ray footpoints is shown to be continuous within the observational error, whereas a discontinuous motion might be anticipated in the slow wave model. Finally, we find that for a preferential slow wave propagation angle of 25 Degree-Sign -28 Degree-Sign that is expected for the fastest waves, the velocities of the hard X-ray footpoints lead to estimated pulse periods and ribbon lengths significantly larger than the measured values. Hence, for the three events studied, we conclude that the observational characteristics cannot be easily explained via the Nakariakov and Zimovets propagating slow wave model when only angles of 25 Degree-Sign -28 Degree-Sign are considered. We provide suggested flare parameters to optimize future studies of this kind.

  16. QUASI-PERIODIC SLIPPING MAGNETIC RECONNECTION DURING AN X-CLASS SOLAR FLARE OBSERVED BY THE SOLAR DYNAMICS OBSERVATORY AND INTERFACE REGION IMAGING SPECTROGRAPH

    SciTech Connect

    Li, Ting; Zhang, Jun E-mail: zjun@nao.cas.cn

    2015-05-01

    We first report the quasi-periodic slipping motion of flare loops during an eruptive X-class flare on 2014 September 10. The slipping motion was investigated at a specific location along one of the two ribbons and can be observed throughout the impulsive phase of the flare. The apparent slipping velocity was 20–110 km s{sup −1}, and the associated period was 3–6 minutes. The footpoints of flare loops appeared as small-scale bright knots observed in 1400 Å, corresponding to fine structures of the flare ribbon. These bright knots were observed to move along the southern part of the longer ribbon and also exhibited a quasi-periodic pattern. The Si iv 1402.77 Å line was redshifted by 30–50 km s{sup −1} at the locations of moving knots with a ∼40–60 km s{sup −1} line width, larger than other sites of the flare ribbon. We suggest that the quasi-periodic slipping reconnection is involved in this process and the redshift at the bright knots is probably indicative of reconnection downflow. The emission line of Si iv at the northern part of the longer ribbon also exhibited obvious redshifts of about 10–70 km s{sup −1} in the impulsive phase of the flare, with the redshifts at the outer edges of the ribbon larger than those in the middle. The redshift velocities at post-flare loops reached about 80–100 km s{sup −1} in the transition region.

  17. Influence of solar flares on the X-ray corona

    NASA Technical Reports Server (NTRS)

    Rust, D. M.; Batchelor, D. A.

    1986-01-01

    Sequences of X-ray images of solar flares, obtained with the Hard X-ray Imaging Spectrometer on the SMM spacecraft, reveal many dynamical phenomena. Movies of 20 flares recorded with 6-sec time resolution were examined. A preliminary analysis of the events as a group are presented, and some new aspects of the well-studied May 21, 1980 flare and a November 6, 1980 flare are discussed.

  18. KEPLER FLARES. I. ACTIVE AND INACTIVE M DWARFS

    SciTech Connect

    Hawley, Suzanne L.; Davenport, James R. A.; Kowalski, Adam F.; Wisniewski, John P.; Deitrick, Russell; Hilton, Eric J.; Hebb, Leslie

    2014-12-20

    We analyzed Kepler short-cadence M dwarf observations. Spectra from the Astrophysical Research Consortium 3.5 m telescope identify magnetically active (Hα in emission) stars. The active stars are of mid-M spectral type, have numerous flares, and have well-defined rotational modulation due to starspots. The inactive stars are of early M type, exhibit less starspot signature, and have fewer flares. A Kepler to U-band energy scaling allows comparison of the Kepler flare frequency distributions with previous ground-based data. M dwarfs span a large range of flare frequency and energy, blurring the distinction between active and inactive stars designated solely by the presence of Hα. We analyzed classical and complex (multiple peak) flares on GJ 1243, finding strong correlations between flare energy, amplitude, duration, and decay time, with only a weak dependence on rise time. Complex flares last longer and have higher energy at the same amplitude, and higher energy flares are more likely to be complex. A power law fits the energy distribution for flares with log E{sub K{sub p}}> 31 erg, but the predicted number of low-energy flares far exceeds the number observed, at energies where flares are still easily detectable, indicating that the power-law distribution may flatten at low energy. There is no correlation of flare occurrence or energy with starspot phase, the flare waiting time distribution is consistent with flares occurring randomly in time, and the energies of consecutive flares are uncorrelated. These observations support a scenario where many independent active regions on the stellar surface are contributing to the observed flare rate.

  19. A solar tornado caused by flares

    NASA Astrophysics Data System (ADS)

    Panesar, N. K.; Innes, D. E.; Tiwari, S. K.; Low, B. C.

    2014-01-01

    An enormous solar tornado was observed by SDO/AIA on 25 September 2011. It was mainly associated with a quiescent prominence with an overlying coronal cavity. We investigate the triggering mechanism of the solar tornado by using the data from two instruments: SDO/AIA and STEREO-A/EUVI, covering the Sun from two directions. The tornado appeared near to the active region NOAA 11303 that produced three flares. The flares directly influenced the prominence-cavity system. The release of free magnetic energy from the active region by flares resulted in the contraction of the active region field. The cavity, owing to its superior magnetic pressure, expanded to fill this vacated space in the corona. We propose that the tornado developed on the top of the prominence due to the expansion of the prominence-cavity system.

  20. Observations of particle acceleration in solar flares

    NASA Technical Reports Server (NTRS)

    Hudson, H. S.

    1979-01-01

    Solar flares provide several examples of nonthermal particle acceleration. The paper reviews the information gained about these processes via X-ray and gamma-ray astronomy, which can presently distinguish among three separate particle-acceleration processes at the sun: an impulsive accelerator of more than 20 keV electrons, a gradual accelerator of more than 20 keV electrons, and a gradual accelerator of more than 10 MeV ions. The acceleration energy efficiency (total particle energy divided by total flare energy) of any of these mechanisms cannot be less than about 0.1%, although the gradual acceleration does not occur in every flare. The observational material suggests that both the impulsive and gradual accelerations take place preferentially in closed magnetic-field structures, but that the electrons decay in these traps before they can escape. The ions escape very efficiently.

  1. Microsecond flares in gamma-ray bursts

    NASA Technical Reports Server (NTRS)

    Schaefer, Bradley E.; Cohen, Justin; Teegarden, Bonnard J.; Cline, Thomas L.; Fishman, Gerald J.; Meegan, Charles A.; Wilson, Robert B.; Paciesas, William S.; Pendleton, Geoffrey N.; Matteson, James L.

    1993-01-01

    It has been suggested that gamma-ray burst light curves may consist of many superposed flares with a duration shorter than 30/microsec. If true, the implications for the interpretation of burst data are enormous. With the launch of the Compton Gamma-Ray Observatory, four predictions of Mitrofanov's (1989) suggestion can be tested. Our results which contradict this suggestion are (1) the photon arrival times are not correlated between independent detectors, (2) the spectral hardness and intensity does not depend on the detector area, (3) the bursts seen by detectors which measure photon positions do not see microsecond flares, and (4) burst positions deduced from detectors with different projected areas are close to the positions deduced from time-of-flight differences between separated spacecraft. We conclude, therefore, that gamma-ray bursts are not composed of microsecond flares.

  2. Observations of an X-shaped Ribbon Flare in the Sun and Its Three-dimensional Magnetic Reconnection

    NASA Astrophysics Data System (ADS)

    Li, Y.; Qiu, J.; Longcope, D. W.; Ding, M. D.; Yang, K.

    2016-05-01

    We report evolution of an atypical X-shaped flare ribbon that provides novel observational evidence of three-dimensional (3D) magnetic reconnection at a separator. The flare occurred on 2014 November 9. High-resolution slit-jaw 1330 Å images from the Interface Region Imaging Spectrograph reveal four chromospheric flare ribbons that converge and form an X-shape. Flare brightening in the upper chromosphere spreads along the ribbons toward the center of the “X” (the X-point), and then spreads outward in a direction more perpendicular to the ribbons. These four ribbons are located in a quadrupolar magnetic field. Reconstruction of magnetic topology in the active region suggests the presence of a separator connecting to the X-point outlined by the ribbons. The inward motion of flare ribbons in the early stage therefore indicates 3D magnetic reconnection between two sets of non-coplanar loops that approach laterally, and reconnection proceeds downward along a section of vertical current sheet. Coronal loops are also observed by the Atmospheric Imaging Assembly on board the Solar Dynamics Observatory confirming the reconnection morphology illustrated by ribbon evolution.

  3. Flare-associated Fast-mode Coronal Wave Trains Discovered by SDO/AIA: Physical Properties and Implications

    NASA Astrophysics Data System (ADS)

    Liu, W.; Ofman, L.; Downs, C.; Cheung, C. M. M.; Broder, B.; De Pontieu, B.

    2015-12-01

    Quasi-periodic Fast Propagating wave trains (QFPs) are a new observational phenomenon discovered in extreme ultraviolet (EUV) by the Atmospheric Imaging Assembly (AIA) onboard the Solar Dynamics Observatory (SDO). They are fast-mode magnetosonic waves, closely related to quasi-periodic pulsations in solar flare emission ranging from radio to X-ray wavelengths. The significance of QFPs lies in their diagnostic potential, because they can provide critical clues to flare energy release and serve as new tools for coronal seismology. In this presentation, we report recent advances in observing and modeling QFPs. For example, using differential emission measure (DEM) inversion, we found clear evidence of heating and cooling cycles that are consistent with alternating compression and rarefaction expected for magnetosonic wave pulses. Moreover, recent IRIS observations of QFP source regions revealed sawtooth-like flare ribbon motions, indicative of pulsed magnetic reconnection, that are correlated with QFP excitation. More interestingly, from a survey of over 100 QFP events, we found a preferential association with eruptive flares rather than confined flares. We will discuss the implications of these results and the potential roles of QFPs in coronal heating, energy transport, and solar eruptions.

  4. Active Region Emergence and Remote Flares

    NASA Astrophysics Data System (ADS)

    Fu, Yixing; Welsch, Brian T.

    2016-02-01

    We study the effect of new emerging solar active regions on the large-scale magnetic environment of existing regions. We first present a theoretical approach to quantify the "interaction energy" between new and pre-existing regions as the difference between i) the summed magnetic energies of their individual potential fields and ii) the energy of their superposed potential fields. We expect that this interaction energy can, depending upon the relative arrangements of newly emerged and pre-existing magnetic flux, indicate the existence of "topological" free magnetic energy in the global coronal field that is independent of any "internal" free magnetic energy due to coronal electric currents flowing within the newly emerged and pre-existing flux systems. We then examine the interaction energy in two well-studied cases of flux emergence, but find that the predicted energetic perturbation is relatively small compared to energies released in large solar flares. Next, we present an observational study of the influence of the emergence of new active regions on flare statistics in pre-existing active regions, using NOAA's Solar Region Summary and GOES flare databases. As part of an effort to precisely determine the emergence time of active regions in a large event sample, we find that emergence in about half of these regions exhibits a two-stage behavior, with an initial gradual phase followed by a more rapid phase. Regarding flaring, we find that the emergence of new regions is associated with a significant increase in the occurrence rate of X- and M-class flares in pre-existing regions. This effect tends to be more significant when pre-existing and new emerging active regions are closer. Given the relative weakness of the interaction energy, this effect suggests that perturbations in the large-scale magnetic field, such as topology changes invoked in the "breakout" model of coronal mass ejections, might play a significant role in the occurrence of some flares.

  5. Predicting large solar flares with data assimilation

    NASA Astrophysics Data System (ADS)

    Strugarek, Antoine; Charbonneau, Paul

    2015-08-01

    Solar and stellar flares are magnetically-driven, scale-invariant energy release events spanning over 8 orders of magnitude in energy. The prediction of the largest solar flares, of class X, is a particularly hard task due the scarcity of such events. The detailed 3D modelling of flaring active regions still requires today too much numerical resources to be routinely used for near real-time predictions. Alternative, empirical models hence have to be designed to perform such predictions. Among the models that adequately reproduce the power-law distribution in flare sizes, avalanche models have the advantage of being numerically cheap to operate. However, they usually rely on a stochastic driver, which can be expected to degrade their predictive capabilities. Building on the pioneering work of Lu and Hamilton, we develop a class of avalanche models which succeed in minimizing the built-in stochastic ingredients while retaining the solar flares power-law distribution. We show that the largest avalanches occurring in these models are robust with respect to the stochastic realization, which opens new perspectives for the prediction of the largest (and most dangerous) solar flares.We further combine data assimilation of the GOES X-ray flux with our avalanche models to carry out actual predictions. The GOES X-ray flux is transformed into a series of peaks that is fed to the model, which automatically finds an initial condition that is compatible with the observed series of events. We then test our prediction model against past GOES large events and discuss the possibility to use our data assimilation package in near real-time applications.

  6. Diagnostics of Solar Flare Energetic Particles

    NASA Astrophysics Data System (ADS)

    Mallik, Procheta; Brown, J. C.; MacKinnon, A. L.

    2009-05-01

    For work on my thesis dissertation, we have been studying some energetic processes in solar flares. On our work on Hard X-ray (HXR) emission from flares, we have shown that recombination emission can exceed the bremsstrahlung HXR flux for certain flare conditions. We will show some spectral features characteristic of non-thermal recombination HXR emission and will suggest how it plays a significant role in the flare HXR continuum, something that has been ignored in the past. It is important to note that these results could demand a reconsideration of the numbers of accelerated electrons since recombination can be much more efficient in producing HXR photons than bremsstrahlung. In related work on diagnosing particle acceleration in flares, we also have an interest in studying solar neutrons. To this end, we will present our work done with new-age neutron detectors developed by our colleagues at the University of New Hampshire. Using laboratory and simulated data from the detector to produce its response matrix, we then employ regularisation and deconvolution techniques to produce encouraging results for data inversion. As a corollary, we have also been reconsidering the role of inverse Compton (IC) scattering of photospheric photons. Gamma-ray observations clearly show the presence of 100 MeV electrons and positrons in the solar corona, by-products of GeV energy ions. Here we will present results of IC scattering of such photons taking proper account of radiation field geometry near the solar surface. If observed, such radiation would let us determine the number of secondary positrons produced in large flares, contributing to a full picture of ion acceleration and to predicting neutron fluxes to be encountered by future inner heliosphere space missions. This work is supported by a UK STFC Rolling Grant and a Dorothy Hodgkin's Scholarship (PM).

  7. On the relationship between sunspots number and the flare index

    NASA Technical Reports Server (NTRS)

    Wilson, Robert M.

    1994-01-01

    During the years 1976-1991, sunspot number and the Kleczek flare index have displayed a strong linear correlation (r = 0.94), one that can be described by the equation y = -0.15 + 0.10 x, where x denotes annual sunspot number. While true, the temporal behaviors of the two parameters have differed, with sunspot number peaking first in 1979 and the flare index peaking much later in 1982 during cycle 21 and with more contemporaneous behavior in cycle 22 (both peaking in 1989, with a secondary peak in 1991). The difference appears to be directly attributable to the way in which the Kleczek flare index has been defined; namely, the annual flare index is the sum of the product of each flare's intensity (importance) times its duration (in minutes) divided by the total number of flares during the year. Because the number of 'major' flares (those of importance greater than or equal to 2) and flares of very long duration (duration greater than or equal to 100 min) both peaked after sunspot maximum (1982/81, respectively) in cycle 21, one should have expected the flare index to also peak (which it did). Likewise, because the number of major flares and flares of very long duration peaked simultaneously with sunspot number (1989) in cycle 22, one should have expected the flare index to also peak (which it did).

  8. SECONDARY FLARE RIBBONS OBSERVED BY THE SOLAR DYNAMICS OBSERVATORY

    SciTech Connect

    Zhang, Jun; Li, Ting; Yang, Shuhong E-mail: liting@nao.cas.cn

    2014-02-20

    Using the observations from the Atmospheric Imaging Assembly (AIA) and the Helioseismic and Magnetic Imager on board the Solar Dynamics Observatory, we statistically investigate the flare ribbons (FRs) of 19 X-class flares of the 24th solar cycle from 2010 June to 2013 August. Of these 19 flares, the source regions of 16 can be observed by AIA and the FRs of each flare are well detected, and 11 of the 16 display multiple ribbons. Based on the ribbon brightness and the relationship between the ribbons and post-flare loops, we divide the multiple ribbons into two types: normal FRs, which are connected by post-flare loops and have been extensively investigated, and secondary flare ribbons (SFRs), which are weaker than the FRs, not connected by post-flare loops, and always have a short lifetime. Of the 11 SFRs, 10 appear simultaneously with the FRs, and none of them have post-flare loops. The last one, on the other hand, appears 80 minutes later than the FR, lasts almost two hours, and also has no post-flare loops detected. We suggest that the magnetic reconnection associated with this SFR is triggered by the blast wave that results from the main flare. These observations imply that in some flare processes, more than two sets of magnetic loops or more than twice the number of magnetic reconnections are involved.

  9. A CIRCULAR-RIBBON SOLAR FLARE FOLLOWING AN ASYMMETRIC FILAMENT ERUPTION

    SciTech Connect

    Liu, Chang; Deng, Na; Lee, Jeongwoo; Wang, Haimin; Liu, Rui; Pariat, Étienne; Wiegelmann, Thomas; Liu, Yang; Kleint, Lucia

    2015-10-20

    The dynamic properties of flare ribbons and the often associated filament eruptions can provide crucial information on the flaring coronal magnetic field. This Letter analyzes the GOES-class X1.0 flare on 2014 March 29 (SOL2014-03-29T17:48), in which we found an asymmetric eruption of a sigmoidal filament and an ensuing circular flare ribbon. Initially both EUV images and a preflare nonlinear force-free field model show that the filament is embedded in magnetic fields with a fan-spine-like structure. In the first phase, which is defined by a weak but still increasing X-ray emission, the western portion of the sigmoidal filament arches upward and then remains quasi-static for about five minutes. The western fan-like and the outer spine-like fields display an ascending motion, and several associated ribbons begin to brighten. Also found is a bright EUV flow that streams down along the eastern fan-like field. In the second phase that includes the main peak of hard X-ray (HXR) emission, the filament erupts, leaving behind two major HXR sources formed around its central dip portion and a circular ribbon brightened sequentially. The expanding western fan-like field interacts intensively with the outer spine-like field, as clearly seen in running difference EUV images. We discuss these observations in favor of a scenario where the asymmetric eruption of the sigmoidal filament is initiated due to an MHD instability and further facilitated by reconnection at a quasi-null in corona; the latter is in turn enhanced by the filament eruption and subsequently produces the circular flare ribbon.

  10. Universality in Solar Flare and Earthquake Occurrence

    SciTech Connect

    De Arcangelis, L.; Godano, C.; Lippiello, E.; Nicodemi, M.

    2006-02-10

    Earthquakes and solar flares are phenomena involving huge and rapid releases of energy characterized by complex temporal occurrence. By analyzing available experimental catalogs, we show that the stochastic processes underlying these apparently different phenomena have universal properties. Namely, both problems exhibit the same distributions of sizes, interoccurrence times, and the same temporal clustering: We find after flare sequences with power law temporal correlations as the Omori law for seismic sequences. The observed universality suggests a common approach to the interpretation of both phenomena in terms of the same driving physical mechanism.

  11. The solar-flare induced earth's environment

    NASA Technical Reports Server (NTRS)

    Wu, S. T.; Dryer, M.; Han, S. M.

    1985-01-01

    A composite numerical simulation model developed from a series of MHD models was used to compute the solar-flare-generated disturbances of physical parameters, such as density, temperature, velocity, and magnetic field from the solar surface (i.e., the photospheric level) to the earth's environment. It is shown that the disturbed earth's environment at high latitudes can be approximated by starting with the knowledge of the occurrence and the strength of a solar flare, then simulating the evolutionary consequences of the solar disturbance through interplanetary space up to and through the magnetosphere.

  12. Carbon-poor solar flare events

    NASA Technical Reports Server (NTRS)

    Mason, G. M.; Gloeckler, G.; Hovestadt, D.

    1979-01-01

    Energetic particle flux enhancements over the period October 1973 - December 1977 were surveyed using ULET sensor on the IMP-8 spacecraft. During the four year period the most extreme periods of Fe enrichment compared to oxygen were during solar flare events in February 1974 and May 1974. In these same events, the carbon abundance with respect to oxygen was significantly depleted when compared with a value C:0 is approximately 0.45:1 for typical solar flares. These observations, taken together with previously reported He-3 enrichment in these events, give strong evidence for the importance of a wave-particle interaction in the pre-injection heating of the ambient matter.

  13. Universality in solar flare and earthquake occurrence.

    PubMed

    de Arcangelis, L; Godano, C; Lippiello, E; Nicodemi, M

    2006-02-10

    Earthquakes and solar flares are phenomena involving huge and rapid releases of energy characterized by complex temporal occurrence. By analyzing available experimental catalogs, we show that the stochastic processes underlying these apparently different phenomena have universal properties. Namely, both problems exhibit the same distributions of sizes, interoccurrence times, and the same temporal clustering: We find after flare sequences with power law temporal correlations as the Omori law for seismic sequences. The observed universality suggests a common approach to the interpretation of both phenomena in terms of the same driving physical mechanism.

  14. On Solar Flares and Cycle 23

    NASA Astrophysics Data System (ADS)

    Kossobokov, Vladimir; Le Mouël, Jean-Louis; Courtillot, Vincent

    2012-02-01

    The anomalous character of Solar Cycle 23, which ended in the Summer of 2009, has been pointed out by many authors. It has even been proposed that the solar dynamo is undergoing a transition from a state of “grand maximum” to one of “regular oscillations”. We analyze the temporal distribution of the number and energy of solar flares, and the duration of intervals between them, over Cycles 21 to 23. We consider 32 355 flares of class C2 and larger (C2+) from the GOES catalogue. Daily values of X-ray flux (wavelengths 1 to 8 Å) have been computed by summing the energy proxies of the events. The series of daily numbers of C2+ solar flares are strongly correlated with their daily energy flux. The long duration of Cycle 23 (12.8 years based on sunspots, 13.2 years based on flares) and the long interval with no C2+ flare between the end of Cycle 23, and the start of Cycle 24 (466 days) are remarkable compared to the two earlier cycles. The amplitudes of extreme flares increase when the mean flux decreases. We have calculated running averages of energy flux over intervals going from 7 to 365 days. The singular shape of Cycle 23 is increasingly striking with increasing interval: in the first ≈ 70% of the cycle (displayed on a logarithmic scale) we see linearly rising maxima, whereas minima are aligned along a descending slope for the latter part of the cycle. The energy flux oscillates between these and takes the shape of a bifurcation, starting near 2002 (a time when it is suggested that photospheric fields were abruptly reduced). Inter-event intervals between successive C2+ flares undergo quasi-periodic (≈ 11 years) oscillations between two distinct states, which we call “active” and “quiet”, with extremely sharp onset and termination. The ratio of time spent in the active vs. quiet states ranges from 1.8 to 1.4 for Cycles 21 to 23, Cycle 23 having the longest quiet period. It has been proposed that anomalous Cycle 23 resembles Cycle 4, which was

  15. The Physical Processes of Eruptive Flares Revealed By An Extremely-Long-Duration Event

    NASA Astrophysics Data System (ADS)

    Zhang, Jie; Zhou, Zhenjun

    2016-05-01

    In this work, we report the physical processes of eruptive flares inferred from an extremely- long-duration event occurred on June 21, 2011. The flare, peaked at C7.7 level, had a two-hour-long rise time in soft X-rays emission; this rise time is much longer than the typical rise time of solar flares that last for only about ten minutes. Combining the fact that the flare occurred near the disk center as seen by SDO, but near the limbs as seen by STEREO A and B, we are able to track the evolution of the eruption in 3-D as well as in a rare slow-motion manner. The time sequence of temperature maps, constructed from six corona-temperature passbands of AIA, clearly shows process of how the highly-twisted sigmoid structure prior to the eruption is transformed into a near-potential post-eruption loop arcade. The observed sigmoid is likely to be the structure of a twisted magnetic flux rope, which reached a height of about 60 Mm at the onset of the eruption. The onset is likely triggered by the torus instability (or loss of equilibrium) of the flux rope as indicated by the slow rise motion prior to the impulsive phase. We also find that the complex evolution of footprints of the eruption as seen from AIA transition region images is consistent with the magnetic evolution in the corona, which is the consequence of the combined effects of the expansion of the magnetic flux rope and the magnetic reconnection of surrounding magnetic fields.

  16. FLARE FOOTPOINT REGIONS AND A SURGE OBSERVED BY HINODE/EIS, RHESSI, AND SDO/AIA

    SciTech Connect

    Doschek, G. A.; Warren, H. P.; Dennis, B. R.; Reep, J. W.; Caspi, A.

    2015-11-01

    The Extreme-ultraviolet Imaging Spectrometer (EIS) on the Hinode spacecraft observed flare footpoint regions coincident with a surge for an M3.7 flare observed on 2011 September 25 at N12 E33 in active region 11302. The flare was observed in spectral lines of O vi, Fe x, Fe xii, Fe xiv, Fe xv, Fe xvi, Fe xvii, Fe xxiii, and Fe xxiv. The EIS observations were made coincident with hard X-ray bursts observed by RHESSI. Overlays of the RHESSI images on the EIS raster images at different wavelengths show a spatial coincidence of features in the RHESSI images with the EIS upflow and downflow regions, as well as loop-top or near-loop-top regions. A complex array of phenomena were observed, including multiple evaporation regions and the surge, which was also observed by the Solar Dynamics Observatory/Atmospheric Imaging Assembly telescopes. The slit of the EIS spectrometer covered several flare footpoint regions from which evaporative upflows in Fe xxiii and Fe xxiv lines were observed with Doppler speeds greater than 500 km s{sup −1}. For ions such as Fe xv both evaporative outflows (∼200 km s{sup −1}) and downflows (∼30–50 km s{sup −1}) were observed. Nonthermal motions from 120 to 300 km s{sup −1} were measured in flare lines. In the surge, Doppler speeds are found from about 0 to over 250 km s{sup −1} in lines from ions such as Fe xiv. The nonthermal motions could be due to multiple sources slightly Doppler-shifted from each other or turbulence in the evaporating plasma. We estimate the energetics of the hard X-ray burst and obtain a total flare energy in accelerated electrons of ≥7 × 10{sup 28} erg. This is a lower limit because only an upper limit can be determined for the low-energy cutoff to the electron spectrum. We find that detailed modeling of this event would require a multithreaded model owing to its complexity.

  17. Temporal relationship between high-energy proton acceleration and magnetic field changes during solar flares

    NASA Astrophysics Data System (ADS)

    Kurt, Victoria; Yushkov, Boris

    Understanding of the association of the magnetic field evolution in the corona and the temporal evolution of electromagnetic emissions produced by the accelerated particles during a solar flare can provide information about the nature of the energy-release process and its location. Recent high-spatial-resolution observations in HXR, UV and radio emissions allow one to study in detail a structure of two-ribbon flare site. According to these observations, the flare process can be divided into two different intervals with different temporal evolution of morphological structure: loop contraction during impulsive phase and subsequent loop expansion. Оn the other hand, the appearance of high-energy protons (with energy >300 MeV - an energy threshold of the pion production) in the solar atmosphere can be revealed from an emerging pion-decay component of high-energy gamma-ray emission. The present work is based on comparison of measurements of high-energy gamma-rays performed with the SONG detector onboard the CORONAS-F mission and reported observations of magnetic field evolution, such as HXR foot points (FP) separation and flare shear temporal behavior, or motion of UV/radio loops. We reliably identified the pion-decay component of gamma-ray emission in the course of five events attended with suitable spatial observations, namely, 2001 August 25, 2002 August 24, 2003 October 28, 2003 October 29, and 2005 January 20, and determined its onset time. We found that in these events the pion-decay emission occurred when the distance between conjugated foot-points of flare loops ceased to decrease and began to increase, i.e. changed from shrinkage to expansion. This result leads to the conclusion that the most efficient proton acceleration up to >300 MeV coincided in time with the radical reconfiguration of the magnetic field in the flare site. Earlier we found that the pion-decay emission onset in the 2003 October 28 flare was close to the time of maximum change rate of the

  18. Photospheric Magnetic Field Properties of Flaring versus Flare-quiet Active Regions. II. Discriminant Analysis

    NASA Astrophysics Data System (ADS)

    Leka, K. D.; Barnes, G.

    2003-10-01

    We apply statistical tests based on discriminant analysis to the wide range of photospheric magnetic parameters described in a companion paper by Leka & Barnes, with the goal of identifying those properties that are important for the production of energetic events such as solar flares. The photospheric vector magnetic field data from the University of Hawai'i Imaging Vector Magnetograph are well sampled both temporally and spatially, and we include here data covering 24 flare-event and flare-quiet epochs taken from seven active regions. The mean value and rate of change of each magnetic parameter are treated as separate variables, thus evaluating both the parameter's state and its evolution, to determine which properties are associated with flaring. Considering single variables first, Hotelling's T2-tests show small statistical differences between flare-producing and flare-quiet epochs. Even pairs of variables considered simultaneously, which do show a statistical difference for a number of properties, have high error rates, implying a large degree of overlap of the samples. To better distinguish between flare-producing and flare-quiet populations, larger numbers of variables are simultaneously considered; lower error rates result, but no unique combination of variables is clearly the best discriminator. The sample size is too small to directly compare the predictive power of large numbers of variables simultaneously. Instead, we rank all possible four-variable permutations based on Hotelling's T2-test and look for the most frequently appearing variables in the best permutations, with the interpretation that they are most likely to be associated with flaring. These variables include an increasing kurtosis of the twist parameter and a larger standard deviation of the twist parameter, but a smaller standard deviation of the distribution of the horizontal shear angle and a horizontal field that has a smaller standard deviation but a larger kurtosis. To support the

  19. Transport and containment of plasma, particles and energy within flares

    NASA Technical Reports Server (NTRS)

    Acton, L. W.; Brown, W. A.; Bruner, M. E. C.; Haisch, B. M.; Strong, K. T.

    1983-01-01

    Results from the analysis of flares observed by the Solar Maximum Mission (SMM) and a recent rocket experiment are discussed. Evidence for primary energy release in the corona through the interaction of magnetic structures, particle and plasma transport into more than a single magnetic structure at the time of a flare and a complex and changing magnetic topology during the course of a flare is found. The rocket data are examined for constraints on flare cooling, within the context of simple loop models. These results form a basis for comments on the limitations of simple loop models for flares.

  20. Outer Atmospheres of Low Mass Stars — Flare Characteristics.

    NASA Astrophysics Data System (ADS)

    Lalitha, S.; Schmitt, J. H. M. M.

    2013-04-01

    We compare the coronal properties during flares on active low mass stars CN Leonis, AB Doradus A and Proxima Centauri observed with XMM-Newton. From the X-ray data we analyze the temporal evolution of temperature, emission measure and coronal abundance. The nature of these flares are with secondary events following the first flare peak in the light curve, raising the question regarding the involved magnetic structure. We infer from the plasma properties and the geometry of the flaring structure that the flare originates from a compact arcade rather than in a single loop.

  1. The H-alpha/H-beta ratio in solar flares

    NASA Technical Reports Server (NTRS)

    Zirin, H.; Liggett, M.; Patterson, A.

    1982-01-01

    The present investigation involves the study of an extensive body of data accumulated of simultaneous H-alpha and H-beta cinematography of flares. The data were obtained with two telescopes simultaneously photographing flares in H-alpha and H-beta. The results of measurements in a number of flares are presented in a table. The flares were selected purely by optical quality of the data. That the measured ratios are not too different from those in stellar flares is suggested by the last two columns of the table. These columns show that a variety of possible line width ratios could give an integrated intensity ratio of less than unity.

  2. Magnetic helicity injection in NOAA 11261 associated with flares

    NASA Astrophysics Data System (ADS)

    Xu, Haiqing; Zhang, Hongqi; Su, Jiangtao; Ruan, Guiping; liu, Jihong

    2013-07-01

    Magnetic helicity was found important in understanding solar activities such as flares and coronal mass ejections (CME). Berger and field (1984) derived an expression for helicity flux dHm/dt, that can be applied to an individual solar active region (AR) occupying an area S of the photosphere, (1) \\begin{linenomath}dHm/dt=-2\\ints[(\\mathbf{Ap}\\cdot \\mathbf{V})\\mathbf{B}-(\\mathbf{Ap} \\cdot \\mathbf{B})\\mathbf{V}] dS, \\eqno{(1)}\\end{linenomath} where Ap is the vector potential of potential field, and V is the plasma velocity at the surface S. The first term describes the effect of magnetic footpoint motions on the surface S. The second term describes the flux of helicity advected through the surface when already twisted and/or writhed flux ropes emerge. Chae (2001) proposed a method of self-consistently determining magnetic helicity injection rate, dH/dt, using a time series of longitudinal magnetograms only: (2) \\begin{linenomath}dH/dt=-\\int2(\\textbf{A}p\\cdot \\textbf{V}LCT)BndS, \\eqno{(2)}\\end{linenomath} where n is the normal component of magnetic field. Ap is the vector potential computed from Bn by Fourier transform method. V LCT is the horizontal component of velocity determined by the technique of local correlation tracking (LCT). This technique was applied by some scientists (e.g., Chae et al., 2001; Nindos and Zhang, 2002; Romano et al., 2003). Magnetic helicity injection was found to be strongly correlated with the occurrence of major flares (Moon et al. 2002a, 2002b; Park et al., 2008; Labonte et al., 2007; Maeshiro et al., 2009).

  3. IUE spectra of a flare in HR 5110: A flaring RS CVn or Algol system?

    NASA Technical Reports Server (NTRS)

    Simon, T.; Linsky, J. L.; Schiffer, F. H., III

    1981-01-01

    Ultraviolet spectra of the RS CVn type binary system HR 5110 were obtained with IUE on May 31, 1979 during a period of intense radio flaring of this star. High temperature transition region lines are present, but are not enhanced above observed quiescent strengths. The similarities of HR 5110 to the Algol system, As Eri, suggest that the 1979 May to June flare may involve mass exchange rather than annihilation of coronal magnetic fields.

  4. Flare evolution and magnetic configuration study

    NASA Astrophysics Data System (ADS)

    Berlicki, A.; Schmieder, B.; Aulanier, G.; Vilmer, N.; Yan, Y. H.

    We will present the analysis of M1.0 confined flare emission and evolution in the context of the topology of the coronal magnetic field. This flare was observed in NOAA 0162 on 22 October 2002. The multiwavelength data were taken during a coordinated observational campaign between ground based instruments and space observatories. The photospheric line-of-sight magnetic field observations were obtained with THEMIS and SOHO/MDI. We used these data to perform linear force-free field extrapolation of magnetic field into the corona. Our extrapolation provides an explanation of the appearance of H-alpha flare ribbons. An elongated shape of X-ray emission observed by Reuven Ramaty High Energy Solar Spectroscopic Imager (RHESSI) also follow the predicted shape of extrapolated field lines. Moreover, the X-ray emission observed by RHESSI permit to see thermal emission of coronal loops heated probably by non-thermal electrons, accelerated during the reconnection processes. The presence of non-thermal particles can be deduced from RHESSI X-ray spectra reconstructed during the gradual phase of the flare. On Huairou vector magnetograms of the AR we see that there was strong shear between one of main negative spot and the north small positive spot. The extrapolation with non-constant alpha force-free field model did not obtain any loop to connect these two spots.

  5. 40 CFR 65.147 - Flares.

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ...) Flares shall be used only when the net heating value of the gas being combusted is 11.2 megajoules per...-assisted or air-assisted, or when the net heating value of the gas being combusted is 7.45 megajoules per... nonassisted. The net heating value of the gas being combusted shall be determined by the methods specified...

  6. 40 CFR 63.987 - Flare requirements.

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ... additional cycles. (ii) The net heating value of the gas being combusted in a flare shall be calculated using Equation 1: ER29JN99.000 Where: HT = Net heating value of the sample, megajoules per standard cubic meter... subject to this subpart shall meet the performance requirements in 40 CFR 63.11(b) (General...

  7. 40 CFR 65.147 - Flares.

    Code of Federal Regulations, 2013 CFR

    2013-07-01

    ...) Flares shall be used only when the net heating value of the gas being combusted is 11.2 megajoules per...-assisted or air-assisted, or when the net heating value of the gas being combusted is 7.45 megajoules per... nonassisted. The net heating value of the gas being combusted shall be determined by the methods specified...

  8. 40 CFR 63.987 - Flare requirements.

    Code of Federal Regulations, 2013 CFR

    2013-07-01

    ... additional cycles. (ii) The net heating value of the gas being combusted in a flare shall be calculated using Equation 1: ER29JN99.000 Where: HT = Net heating value of the sample, megajoules per standard cubic meter... subject to this subpart shall meet the performance requirements in 40 CFR 63.11(b) (General...

  9. 40 CFR 63.987 - Flare requirements.

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... additional cycles. (ii) The net heating value of the gas being combusted in a flare shall be calculated using Equation 1: ER29JN99.000 Where: HT = Net heating value of the sample, megajoules per standard cubic meter... subject to this subpart shall meet the performance requirements in 40 CFR 63.11(b) (General...

  10. Energetic electrons generated during solar flares

    NASA Astrophysics Data System (ADS)

    Mann, Gottfried

    2015-12-01

    > electrons are accelerated up to energies beyond 30 keV is one of the open questions in solar physics. A flare is considered as the manifestation of magnetic reconnection in the solar corona. Which mechanisms lead to the production of energetic electrons in the magnetic reconnection region is discussed in this paper. Two of them are described in more detail.

  11. What's an Asthma Flare-Up?

    MedlinePlus

    ... Quizzes Kids' Dictionary of Medical Words En Español What Other Kids Are Reading Back-to-School Butterflies? ... Got Homework? Here's Help White House Lunch Recipes What's an Asthma Flare-Up? KidsHealth > For Kids > What's ...

  12. Transient particle acceleration associated with solar flares.

    PubMed

    Chupp, E L

    1990-10-12

    Understanding how individual charged particles can be accelerated to extreme energies (10(20) electron volts), remains a foremost problem in astrophysics. Within our solar system, the active sun is capable of producing, on a short time scale, ions with energies higher than 25 gigaelectron volts. Satellite and ground-based observation over the past 30 years have greatly increased our knowledge of the properties of transient bursts of energetic particles emitted from the sun in association with solar flares, but a real understanding of the solar flare particle acceleration process requires greatly refined experimental data. On the practical side, it is also imperative that this problem be solved if man is to venture, for long periods of time, beyond the protective umbrella of Earth's magnetic field, which excludes much of the biologically damaging solar energetic particles. It is only through an understanding of the basic acceleration problem that we can expect to be able to predict the occurrence of a solar flare with lethal solar radiations. For our knowledge of these effects to advance, a new space mission dedicated to studying the high-energy aspects of solar flares at high spatial and energy resolution will be required.

  13. MEASUREMENTS OF ABSOLUTE ABUNDANCES IN SOLAR FLARES

    SciTech Connect

    Warren, Harry P.

    2014-05-01

    We present measurements of elemental abundances in solar flares with the EUV Variability Experiment (EVE) on the Solar Dynamics Observatory. EVE observes both high temperature Fe emission lines (Fe XV-Fe XXIV) and continuum emission from thermal bremsstrahlung that is proportional to the abundance of H. By comparing the relative intensities of line and continuum emission it is possible to determine the enrichment of the flare plasma relative to the composition of the photosphere. This is the first ionization potential or FIP bias (f). Since thermal bremsstrahlung at EUV wavelengths is relatively insensitive to the electron temperature, it is important to account for the distribution of electron temperatures in the emitting plasma. We accomplish this by using the observed spectra to infer the differential emission measure distribution and FIP bias simultaneously. In each of the 21 flares that we analyze we find that the observed composition is close to photospheric. The mean FIP bias in our sample is f = 1.17 ± 0.22. This analysis suggests that the bulk of the plasma evaporated during a flare comes from deep in the chromosphere, below the region where elemental fractionation occurs.

  14. Dust Reprocessing of Stellar Tidal Disruption Flares

    NASA Astrophysics Data System (ADS)

    van Velzen, Sjoert; Gorjian, Varoujan; Krolik, Julian; Mendez, Alexander

    2015-10-01

    A stellar tidal disruption flare (TDF) occurs when a star gets too close to a supermassive black hole and is shredded into streams that are accreted. Traditionally, TDFs are observed at optical to soft X-ray wavelengths. We have recently made a discovery that opens a new (and unexpected) wavelength regime for the study of these flares: transient emission at 3.4 micron in WISE multi-epoch imaging. This dust reprocessing signal was not previously predicted, but will likely be of great importance to further our (limited) understanding the TDF emission mechanism. Since the radius of the IR-emitting shell is determined by the dust sublimation temperature, the break in the IR light curve can be used to measure the bolometric luminosity of the tidal flare. With the low-cadence WISE observations as a proof-of-concept, the time is ripe to use warm Spitzer observations to make a major breakthrough: we wish to obtain the first well-sampled light curve of dust reverberation by a stellar tidal flare. If successful, these observations will have lasting impact; near-future synoptic surveys (ZTF, LSST) will find thousands of TDFs per year, which can be followed-up by IR missions (JWST, WFIRST) to obtain a census of dust within the sphere of influence of quiescent supermassive black holes.

  15. 40 CFR 65.147 - Flares.

    Code of Federal Regulations, 2012 CFR

    2012-07-01

    ... basis, as measured for organics by Method 18 of appendix A of 40 CFR part 60 and measured for hydrogen... and pressure), as determined by Method 2, 2A, 2C, or 2D of appendix A of 40 CFR part 60 as appropriate... 40 Protection of Environment 16 2012-07-01 2012-07-01 false Flares. 65.147 Section...

  16. 40 CFR 65.147 - Flares.

    Code of Federal Regulations, 2014 CFR

    2014-07-01

    ... basis, as measured for organics by Method 18 of appendix A of 40 CFR part 60 and measured for hydrogen... and pressure), as determined by Method 2, 2A, 2C, or 2D of appendix A of 40 CFR part 60 as appropriate... 40 Protection of Environment 16 2014-07-01 2014-07-01 false Flares. 65.147 Section...

  17. Solar gamma rays. [in solar flares

    NASA Technical Reports Server (NTRS)

    Ramaty, R.; Kozlovsky, B.; Lingenfelter, R. E.

    1974-01-01

    The theory of gamma ray production in solar flares is treated in detail. Both lines and continuum are produced. Results show that the strongest line predicted at 2.225 MeV with a width of less than 100 eV and detected at 2.24 + or - 2.02 MeV, is due to neutron capture by protons in the photosphere. Its intensity is dependent on the photospheric He-3 abundance. The neutrons are produced in nuclear reactions of flare accelerated particles which also produce positrons and prompt nuclear deexcitation lines. The strongest prompt lines are at 4.43 MeV from c-12 and at approximately 6.2 from 0-16 and N-15. The gamma ray continuum, produced by electron bremsstrahlung, allows the determination of the spectrum and number of accelerated electrons in the MeV region. From the comparison of the line and continuum intensities a proton-to-electron ratio of about 10 to 100 at the same energy for the 1972, August 4 flare. For the same flare the protons above 2.5 MeV which are responsible for the gamma ray emission produce a few percent of the heat generated by the electrons which make the hard X rays above 20 keV.

  18. Dependence of Sunspot Properties on Flare Occurrence and Flare-CME Association

    NASA Astrophysics Data System (ADS)

    Yang, Ya-Hui

    2015-04-01

    Previous studies showed that the intense flares tend to erupt from the large sunspot region with complex magnetic configuration and strong magnetic field. However, note that not all the active regions (ARs) classified as βγδ would produce X-class flares. To clarify the significance of sunspot properties on solar explosive events, we reexamine the dependence of flare magnitude on sunspot size and magnetic type during 1996-2014 based on the report of NOAA Solar Region Summary and the measurements of GOES soft X-ray flux. In particular, we focus on the βγδ-type ARs to relate the flare productivity to the sunspot area and magnetic field strength by means of the line-of-sight magnetograms from SOHO/MDI and SDO/HMI. Two flare-productive ARs, 10486 and 12192, with βγδ magnetic configuration during most periods of their disk passages are further investigated to characterize the sunspots and flare-CME association.

  19. MOST Observations of Our Nearest Neighbor: Flares on Proxima Centauri

    NASA Astrophysics Data System (ADS)

    Davenport, James R. A.; Kipping, David M.; Sasselov, Dimitar; Matthews, Jaymie M.; Cameron, Chris

    2016-10-01

    We present a study of white-light flares from the active M5.5 dwarf Proxima Centauri using the Canadian microsatellite Microvariability and Oscillations of STars. Using 37.6 days of monitoring data from 2014 to 2015, we have detected 66 individual flare events, the largest number of white-light flares observed to date on Proxima Cen. Flare energies in our sample range from 1029 to 1031.5 erg. The flare rate is lower than that of other classic flare stars of a similar spectral type, such as UV Ceti, which may indicate Proxima Cen had a higher flare rate in its youth. Proxima Cen does have an unusually high flare rate given its slow rotation period, however. Extending the observed power-law occurrence distribution down to 1028 erg, we show that flares with flux amplitudes of 0.5% occur 63 times per day, while superflares with energies of 1033 erg occur ∼8 times per year. Small flares may therefore pose a great difficulty in searches for transits from the recently announced 1.27 M ⊕ Proxima b, while frequent large flares could have significant impact on the planetary atmosphere.

  20. White-light Flares on Close Binaries Observed with Kepler

    NASA Astrophysics Data System (ADS)

    Gao, Qing; Xin, Yu; Liu, Ji-Feng; Zhang, Xiao-Bin; Gao, Shuang

    2016-06-01

    Based on Kepler data, we present the results of a search for white light flares on 1049 close binaries. We identify 234 flare binaries, of which 6818 flares are detected. We compare the flare-binary fraction in different binary morphologies (“detachedness”). The result shows that the fractions in over-contact and ellipsoidal binaries are approximately 10%-20% lower than those in detached and semi-detached systems. We calculate the binary flare activity level (AL) of all the flare binaries, and discuss its variations along the orbital period (P orb) and rotation period (P rot, calculated for only detached binaries). We find that the AL increases with decreasing P orb or P rot, up to the critical values at P orb ˜ 3 days or P rot ˜ 1.5 days, and thereafter the AL starts decreasing no matter how fast the stars rotate. We examine the flaring rate as a function of orbital phase in two eclipsing binaries on which a large number of flares are detected. It appears that there is no correlation between flaring rate and orbital phase in these two binaries. In contrast, when we examine the function with 203 flares on 20 non-eclipse ellipsoidal binaries, bimodal distribution of amplitude-weighted flare numbers shows up at orbital phases 0.25 and 0.75. Such variation could be larger than what is expected from the cross section modification.

  1. On Flare and CME Predictability Based on Sunspot Group Evolution

    NASA Astrophysics Data System (ADS)

    Korsós, M. B.; Ruderman, M. S.

    2016-04-01

    We propose to apply the weighted horizontal magnetic gradient (WGM), introduced in Korsós et al. (2015), for analysing the pre-flare and pre-CME behaviour and evolution of Active Regions (ARs) using the SDO/HMI-Debrecen Data catalogue. To demonstrate the power of investigative capabilities of the WGM method in terms of flare/CME eruptions, we show the results of studying three typical active regions, namely, AR11818, AR12017 and AR11495. The choice of ARs represent typical cases of flaring with a fast CME, flare eruption without a CME and non-flaring cases, respectively. AR11818 produced an M1.4 energetic flare with a fast "halo" CME (vlinear=1202 km/s) while in AR12017 occurred an X1.0 flare without a CME. The AR11495 is a good example for non-flaring ARs. The value and temporal variation of WGM is found to possess potentially important diagnostic information about the intensity of expected flares. However, this test turns out not only to provide information about the intensity of expected flares but may also show whether a flare will occur with/without a fast CME.

  2. On Solar Flares and Cycle 23

    NASA Astrophysics Data System (ADS)

    Kossobokov, V. G.; Le Mouel, J.; Courtillot, V.

    2011-12-01

    The anomalous character of solar cycle 23 has been pointed out. It is proposed that the solar dynamo is undergoing a transition from a state of "grand maximum" to one of "regular oscillations". In this study, we analyze the time distribution of the number and energy of solar flares, and the duration of intervals between them, from cycle 21 to 23. We consider 32355 flares of class C2 and larger (C2+) from the GOES catalogue. Daily values of X-ray flux (wavelengths 1-8Å) have been computed by summing the energy proxies of the events. The series of daily numbers of C2+ solar flares are strongly correlated to their daily energy flux. The long duration of cycle 23 (~13 years), the long interval with no C2+ flare between the end of cycle 23 and the start of cycle 24 (466 days) are remarkable compared to the two earlier cycles. Amplitudes of extreme flares increase when mean flux decreases. We have calculated running averages of energy flux over intervals going from 7 to 365 days: the singular shape of cycle 23 is increasingly striking with increasing interval: the first ~70% of the cycle display (in logarithmic scale) linearly rising maxima, whereas minima are aligned along a descending slope for the latter part of the cycle. Energy flux oscillates between these and takes the shape of a bifurcation, starting near 2002. Durations of inter-event intervals between successive C2+ flares undergo quasi-periodic (~11yr) oscillations between two distinct states, which we call "active" and "quiet", with sharp onset and termination. The ratio of time spent in the active vs quiet states ranges from 1.8 to 1.4 for cycles 21 to 23, cycle 23 having the longest quiet period. It has been proposed that anomalous cycle 23 resembles cycle 4, which was followed by reduced cycles 5 and 6 at the time of the Dalton-minimum in solar activity, often associated with a cooler global climate. It will be interesting to monitor the evolution of solar flares in cycle 24, in order to further our

  3. Compensation of flare-induced CD changes EUVL

    DOEpatents

    Bjorkholm, John E.; Stearns, Daniel G.; Gullikson, Eric M.; Tichenor, Daniel A.; Hector, Scott D.

    2004-11-09

    A method for compensating for flare-induced critical dimensions (CD) changes in photolithography. Changes in the flare level results in undesirable CD changes. The method when used in extreme ultraviolet (EUV) lithography essentially eliminates the unwanted CD changes. The method is based on the recognition that the intrinsic level of flare for an EUV camera (the flare level for an isolated sub-resolution opaque dot in a bright field mask) is essentially constant over the image field. The method involves calculating the flare and its variation over the area of a patterned mask that will be imaged and then using mask biasing to largely eliminate the CD variations that the flare and its variations would otherwise cause. This method would be difficult to apply to optical or DUV lithography since the intrinsic flare for those lithographies is not constant over the image field.

  4. Ultraviolet and radio flares from UX Arietis and HR 1099

    SciTech Connect

    Lang, K.R.; Willson, R.F.

    1988-05-01

    Simultaneous observations of the RS CVn systems UX Ari and HR 1099 with the IUE satellite and the VLA are presented. Flaring activity is observed at ultraviolet wavelengths with the IUE when none is detected at radio wavelengths with the VLA. Radio flares with no detectable ultraviolet activity have also been observed. Thus, flares in the two spectral regions are either uncorrelated or weakly correlated. The flaring emission probably originates in different regions at the two wavelengths. Radio flares from RS CVn stars may originate in sources that are larger than, or comparable to, a star in size. This is in sharp contrast to compact, coherent radio flares from dwarf M stars. The ultraviolet flares from RS CVn stars probably originate in sources that are smaller than a component star. 18 references.

  5. In-progress X-ray Flare Forecasting

    NASA Astrophysics Data System (ADS)

    Balasubramaniam, K. S.; Winter, L. M.

    2015-12-01

    Solar X-ray flares release intense amounts of radiation and can be associated with subsequent changes in the geomagnetic field as well as a large influx of solar energetic particles. From analyses of 50,000 flares detected with the NOAA GOES satellites over the past 40 years, Winter & Balasubramaniam (2015) introduced a flare phase diagram where X-ray observables indicating flare temperature and background solar activity levels can be used to separate flares of different peak flux. We present results from adapting this method into a real-time forecast tool. Real-time GOES X-ray observations are used to predict expected flare class, with updates made every 1-minute. KSB, in part by the Air Force Office of Scientific Research on "the Physics of Coupled Flares and CME Systems". LM was supported by AER, and in part by a contract supported by AFRL/RV

  6. COMPARISON OF PHOTOMETRIC VARIABILITY BEFORE AND AFTER STELLAR FLARES

    SciTech Connect

    Karoff, C.

    2014-01-20

    The energy in the solar acoustic spectrum is known to be correlated with flares, but it is not known if the same is true for stellar flares. In order to answer this question, we have analyzed 73 flares in 39 solar-like stars. These flares were identified in the 854 solar-like stars observed by the Kepler spacecraft that have stellar parameters measured with asteroseismology. Though we were not able to identify a statistically significant enhancement of the energy in the high-frequency part of the post-flare acoustic spectra compared to the pre-flare spectra of these stars, we did identify a larger variability between the energy in the high-frequency part of the post- and pre-flare acoustic spectra compared to spectra taken at random times.

  7. HARD X-RAY AND ULTRAVIOLET OBSERVATIONS OF THE 2005 JANUARY 15 TWO-RIBBON FLARE

    SciTech Connect

    Cheng, J. X.; Qiu, J.; Kerr, G.

    2012-01-01

    It is well known that two-ribbon flares observed in H{alpha} and ultraviolet (UV) wavelengths mostly exhibit compact and localized hard X-ray (HXR) sources. In this paper, we present comprehensive analysis of a two-ribbon flare observed in UV 1600 A by Transition Region and Coronal Explorer and in HXRs by Reuven Ramaty High Energy Solar Spectroscopic Imager. HXR (25-100 keV) imaging observations show two kernels of size (FWHM) 15'' moving along the two UV ribbons. We find the following results. (1) UV brightening is substantially enhanced wherever and whenever the compact HXR kernel is passing, and during the HXR transit across a certain region, the UV count light curve in that region is temporally correlated with the HXR total flux light curve. After the passage of the HXR kernel, the UV light curve exhibits smooth monotonical decay. (2) We measure the apparent motion speed of the HXR sources and UV ribbon fronts, and decompose the motion into parallel and perpendicular motions with respect to the magnetic polarity inversion line (PIL). It is found that HXR kernels and UV fronts exhibit similar apparent motion patterns and speeds. The parallel motion dominates during the rise of the HXR emission, and the perpendicular motion starts and dominates at the HXR peak, the apparent motion speed being 10-40 km s{sup -1}. (3) We also find that UV emission is characterized by a rapid rise correlated with HXRs, followed by a long decay on timescales of 15-30 minutes. The above analysis provides evidence that UV brightening is primarily caused by beam heating, which also produces thick-target HXR emission. The thermal origin of UV emission cannot be excluded, but would produce weaker heating by one order of magnitude. The extended UV ribbons in this event are most likely a result of sequential reconnection along the PIL, which produces individual flux tubes (post-flare loops), subsequent non-thermal energy release and heating in these flux tubes, and then the very long

  8. Origin of the Universal Correlation between the Flare Temperature and the Emission Measure for Solar and Stellar Flares.

    PubMed

    Shibata; Yokoyama

    1999-11-20

    We present a theory to explain the observed universal correlation between flare temperature T and emission measure EM=n2V for solar and stellar flares (including solar microflares observed by Yohkoh as well as protostellar flares observed by ASCA), where n is the electron density and V is the volume. The theory is based on a magnetic reconnection model with heat conduction and chromospheric evaporation, assuming that the gas pressure of a flare loop is comparable to the magnetic pressure. This theory predicts the relation EM~B-5T17/2, which explains well the observed correlation between EM and T in the range of 6x106 K < T<108 K and 1044flares, if the magnetic field strength B of a flare loop is nearly constant for solar and stellar flares.

  9. What's Motion Sickness?

    MedlinePlus

    ... Homework? Here's Help White House Lunch Recipes What's Motion Sickness? KidsHealth > For Kids > What's Motion Sickness? Print ... motion sickness might get even worse. continue Avoiding Motion Sickness To avoid motion sickness: Put your best ...

  10. Brownian Motion.

    ERIC Educational Resources Information Center

    Lavenda, Bernard H.

    1985-01-01

    Explains the phenomenon of Brownian motion, which serves as a mathematical model for random processes. Topics addressed include kinetic theory, Einstein's theory, particle displacement, and others. Points out that observations of the random course of a particle suspended in fluid led to the first accurate measurement of atomic mass. (DH)

  11. Feasibility and Domain Validation of RA Flare Core Domain Set: A Report of the OMERACT 2014 RA Flare Group Plenary

    PubMed Central

    Bartlett, Susan J.; Bykerk, Vivian P.; Cooksey, Roxanne; Choy, Ernest H.; Alten, Rieke; Christensen, Robin; Furst, Daniel E.; Guillemin, Francis; Halls, Serena; Hewlett, Sarah; Leong, Amye L.; Lyddiatt, Anne; March, Lyn; Montie, Pamela; Orbai, Ana Maria; Pohl, Christoph; Voshaar, Marieke Scholte; Woodworth, Thasia G.; Bingham, Clifton O.

    2015-01-01

    Objective The OMERACT RA Flare Group was established to develop an approach to identify and measure rheumatoid arthritis (RA) flares. Here, we provide an overview of our OMERACT 2014 plenary. Methods Feasibility and validity of flare domains endorsed at OMERACT 11 (2012) were described based on initial data from three international studies collected using a common set of questions specific to RA flare. Mean flare frequency, severity, and duration data were presented, and domain scores were compared by flare status to examine known-groups validity. Breakout groups provided input for stiffness, self-management, contextual factors, and measurement considerations. Results Flare data from 501 patients in a observational study indicated 39% were in a flare, with mean (SD) severity of 6.0 (2.6) and 55% lasting > 14 days. Pain, physical function, fatigue, participation and stiffness scores averaged ≥ 2 times higher (2 of 11 points) in flaring individuals. Correlations between flare domains and corresponding legacy instruments were r’s from 0.46 to 0.93. A combined definition (patient-report of flare and DAS28 increase) was evaluated in two other trials with similar results. Breakout groups debated specific measurement issues. Conclusion These data contribute initial evidence of feasibility and content validation of the OMERACT RA Flare Core Domain Set. Our research agenda for OMERACT 2016 includes establishing duration/intensity criteria and developing criteria to identify RA flares using existing disease activity measures. Ongoing work will also address discordance between patients and physician ratings, facilitate applications to clinical care, elucidate the role of self-management and help finalize recommendations for RA flare measurement. PMID:25684764

  12. THE FLARE-ONA OF EK DRACONIS

    SciTech Connect

    Ayres, Thomas R.

    2015-07-15

    EK Draconis (HD 129333: G1.5 V) is a well-known young (50 Myr) solar analog. In 2012, Hubble Space Telescope returned to EK Dra to follow up a far-ultraviolet (FUV) SNAPshot visit by Cosmic Origins Spectrograph (COS) two years earlier. The brief SNAP pointing had found surprisingly redshifted, impulsively variable subcoronal “hot-line” emission of Si iv 1400 Å (T ∼ 8 × 10{sup 4} K). Serendipitously, the 2012 follow-on program witnessed one of the largest FUV flares ever recorded on a sunlike star, which again displayed strong redshifts (downflows) of 30–40 km s{sup −1}, even after compensating for small systematics in the COS velocity scales, uncovered through a cross-calibration by Space Telescope Imaging Spectrograph (STIS). The (now reduced, but still substantial) ∼10 km s{sup −1} hot-line redshifts outside the flaring interval did not vary with rotational phase, so cannot be caused by “Doppler imaging” (bright surface patches near a receding limb). Density diagnostic O iv] 1400 Å multiplet line ratios of EK Dra suggest n{sub e} ∼ 10{sup 11} cm{sup −3}, an order of magnitude larger than in low-activity solar twin α Centauri A, but typical of densities inferred in large stellar soft X-ray events. The self-similar FUV hot-line profiles between the flare decay and the subsequent more quiet periods, and the unchanging but high densities, reinforce a long-standing idea that the coronae of hyperactive dwarfs are flaring all the time, in a scale-free way; a flare-ona if you will. In this picture, the subsonic hot-line downflows probably are a byproduct of the post-flare cooling process, something like “coronal rain” on the Sun. All in all, the new STIS/COS program documents a complex, energetic, dynamic outer atmosphere of the young sunlike star.

  13. The 26 December 2001 Solar Event Responsible for GLE63. I. Observations of a Major Long-Duration Flare with the Siberian Solar Radio Telescope

    NASA Astrophysics Data System (ADS)

    Grechnev, V. V.; Kochanov, A. A.

    2016-10-01

    Ground level enhancements (GLEs) of cosmic-ray intensity occur, on average, once a year. Because they are rare, studying the solar sources of GLEs is especially important to approach understanding their origin. The SOL2001-12-26 eruptive-flare event responsible for GLE63 seems to be challenging in some aspects. Deficient observations limited our understanding of it. Analysis of additional observations found for this event provided new results that shed light on the flare configuration and evolution. This article addresses the observations of this flare with the Siberian Solar Radio Telescope (SSRT). Taking advantage of its instrumental characteristics, we analyze the detailed SSRT observations of a major long-duration flare at 5.7 GHz without cleaning the images. The analysis confirms that the source of GLE63 was associated with an event in active region 9742 that comprised two flares. The first flare (04:30 - 05:03 UT) reached a GOES importance of about M1.6. Two microwave sources were observed, whose brightness temperatures at 5.7 GHz exceeded 10 MK. The main flare, up to an importance of M7.1, started at 05:04 UT and occurred in strong magnetic fields. The observed microwave sources reached a brightness temperature of about 250 MK. They were not static. After appearing on the weaker-field periphery of the active region, the microwave sources moved toward each other nearly along the magnetic neutral line, approaching the stronger-field core of the active region, and then moved away from the neutral line like expanding ribbons. These motions rule out an association of the non-thermal microwave sources with a single flaring loop.

  14. A TRIO OF CONFINED FLARES IN AR 11087

    SciTech Connect

    Joshi, Anand D.; Park, Sung-Hong; Cho, Kyung-Suk; Forbes, Terry G. E-mail: freemler@kasi.re.kr E-mail: terry.forbes@unh.edu

    2015-01-10

    We investigate three flares that occurred in active region, AR 11087, observed by the Dutch Open Telescope (DOT) on 2010 July 13, in a span of three hours. The first two flares have soft X-ray class B3, whereas the third flare has class C3. The third flare not only was the largest in terms of area and brightness but also showed a very faint coronal mass ejection (CME) associated with it, while the earlier two flares had no associated CME. The active region, located at 27° N, 26° E, has a small U-shaped active region filament to the south of the sunspot, and a quiescent filament is located to its west. Hα observations from DOT, as well as extreme-ultraviolet images and magnetograms from the STEREO spacecraft and Solar Dynamics Observatory, are used to study the dynamics of the active region during the three flares. Our observations imply that the first two flares are confined and that some filament material drains to the surface during these flares. At the onset of the third flare downflows are again observed within the active region, but a strong upflow is also observed at the northern end of the adjacent quiescent filament to the west. It is at the latter location that the CME originates. The temporal evolution of the flare ribbons and the dynamics of the filaments are both consistent with the idea that reconnection in a pre-existing current sheet leads to a loss of equilibrium.

  15. FINE STRUCTURES AND OVERLYING LOOPS OF CONFINED SOLAR FLARES

    SciTech Connect

    Yang, Shuhong; Zhang, Jun; Xiang, Yongyuan

    2014-10-01

    Using the Hα observations from the New Vacuum Solar Telescope at the Fuxian Solar Observatory, we focus on the fine structures of three confined flares and the issue why all the three flares are confined instead of eruptive. All the three confined flares take place successively at the same location and have similar morphologies, so can be termed homologous confined flares. In the simultaneous images obtained by the Solar Dynamics Observatory, many large-scale coronal loops above the confined flares are clearly observed in multi-wavelengths. At the pre-flare stage, two dipoles emerge near the negative sunspot, and the dipolar patches are connected by small loops appearing as arch-shaped Hα fibrils. There exists a reconnection between the small loops, and thus the Hα fibrils change their configuration. The reconnection also occurs between a set of emerging Hα fibrils and a set of pre-existing large loops, which are rooted in the negative sunspot, a nearby positive patch, and some remote positive faculae, forming a typical three-legged structure. During the flare processes, the overlying loops, some of which are tracked by activated dark materials, do not break out. These direct observations may illustrate the physical mechanism of confined flares, i.e., magnetic reconnection between the emerging loops and the pre-existing loops triggers flares and the overlying loops prevent the flares from being eruptive.

  16. Diagnosis and treatment of lupus nephritis flares--an update.

    PubMed

    Sprangers, Ben; Monahan, Marianne; Appel, Gerald B

    2012-12-01

    Relapses or flares of systemic lupus erythematosus (SLE) are frequent and observed in 27-66% of patients. SLE flares are defined as an increase in disease activity, in general, requiring alternative treatment or intensification of therapy. A renal flare is indicated by an increase in proteinuria and/or serum creatinine concentration, abnormal urine sediment or a reduction in creatinine clearance rate as a result of active disease. The morbidity associated with renal flares is derived from both the kidney damage due to lupus nephritis and treatment-related toxic effects. Current induction treatment protocols achieve remission in the majority of patients with lupus nephritis; however, few studies focus on treatment interventions for renal flares in these patients. The available data, however, suggest that remission can be induced again in a substantial percentage of patients experiencing a lupus nephritis flare. Lupus nephritis flares are independently associated with an increased risk of deterioration in renal function; prevention of renal flares might, therefore, also decrease long-term morbidity and mortality. Appropriate immunosuppressive maintenance therapy might lead to a decrease in the occurrence of renal and extrarenal flares in patients with SLE, and monitoring for the early detection and treatment of renal flares could improve their outcomes.

  17. Magnetic Reconnection of Solar Flare Detected by Solar Radio Burst Type III

    NASA Astrophysics Data System (ADS)

    Hamidi, Z. S.; Shariff, N. N. M.; Ibrahim, Z. A.; Monstein, C.; Zulkifli, W. N. A. Wan; Ibrahim, M. B.; Arifin, N. S.; Amran, N. A.

    2014-10-01

    The Sun is an ideal object of a blackbody with a large and complex magnetic field. In solar activity specifically solar flare phenomenon, the magnetic reconnection is one of the most significant factors of the Sun that can simplify a better understanding of our nearest star. This factor is due to the motion of the plasma and other particles through the convection mechanism inside the Sun. In our work, we will highlight one of the solar burst events that associated with solar flares. This event occurred on 13th November 2012 from 2:00:03 UT till 2:00:06 UT. It peaked with M2.0 solar flare at 2.04 UT. Within short time intervals of about l02 ~ 103s, large quantities of energy of 1022 ~ 1026J are emancipated. The changing magnetic field converts magnetic potential energy into kinetic energy by accelerating plasmas in the solar corona. It is believed that the plasma is channelled by the magnetic field up and away from the Sun. It is also accelerated back down along the magnetic field into the chromosphere. In conclusion, we showed that the structure of the solar radio burst type III is an indicator of a starting point of magnetic reconnection.

  18. Chromospheric-coronal coupling during solar flares: Current systems and particle acceleration

    NASA Technical Reports Server (NTRS)

    Winglee, Robert M.; Mckean, M. E.; Dulk, G. A.

    1989-01-01

    Two-dimensional (three velocity) electrostatic particle simulations are used to investigate the particle heating and acceleration associated with the impulsive phase of a solar flare. A crossfield current in the high corona (which is presumably driven by reconnection processes) is used to initiate the flare. Due to the differential motion of the electrons and ions, currents, and associated quasi-static electric fields are generated with the primary current and balancing return current being on adjacent field lines. These currents extend from the corona down into the chromosphere. Electrons can be accelerated to energies exceeding 100 keV on short time scales via the quasi-static fields and wave-particle interactions. The spectra of these electrons has a broken power-law distribution which hardens in time. The spatially separate primary and return currents are closed by the cross-field acceleration of the ambient ions into the primary current regions. These ions are then accelerated upwards into the corona by the same quasi-static electric field accelerating the electrons downwards. This acceleration can account for the broadened stationary and weak blue shifted component seen in soft x ray line emissions and enhancements in heavy ion abundances seen in the solar wind in associations with solar flares.

  19. Flare stars in the TW Hydrae association: the HIP 57269 syste

    NASA Astrophysics Data System (ADS)

    König, B.; Neuhäuser, R.; Guenther, E. W.; Hambaryan, V.

    2003-11-01

    We discuss a new member candidate of the TW Hydrae association (TWA) among the stars of the Gershberg et al. ( te{gershberg}) flare star catalog. TWA is one of the closest known associations of young stars at about 60 pc. Three supposedly young flare stars are located in the same region of the sky as TWA. One of them (HIP 57269) shows strong lithium absorption with spectral type K1/K2V and a high level of chromospheric and coronal activity. It is located at a distance of 48.7±6.3 pc in common with the five TWA members observed with Hipparcos (46.7 to 103.9 pc). HIP 57268 A has a wide companion C which also shows lithium absorption at 6707 Å and which has common proper motion with HIP 57269, as well as a close companion resolved visually by Tycho. HIP 57269 A&C lie above the main sequence and are clearly pre-main-sequence stars. The UVW-space velocity is more consistent with the star system being a Pleiades super cluster member. The two other flare stars in the TWA sky region do not show lithium at all and are, hence, unrelated. Data obtained at ESO La Silla and ESO Paranal with programs: 66.C-0138(B), 67.C-0073(A), 68.C-0009(A), 68.C-0018(A)

  20. Reconnection-Powered Extreme Particle Acceleration and Gamma-Ray Flares in Crab Nebula

    NASA Astrophysics Data System (ADS)

    Uzdensky, Dmitri; Cerutti, Benoit; Begelman, Mitchell

    2011-11-01

    Recent discovery of gamma-ray flares in the Crab Nebula challenges traditional relativistic particle acceleration models. These flares are presumably produced by PeV electrons radiating >100 MeV synchrotron photons in a milli-gauss magnetic field. In traditional models, where the accelerating electric field is smaller than the magnetic field, synchrotron radiation cannot exceed 100 MeV because radiative losses balance the acceleration rate. We propose that linear electric acceleration in a magnetic reconnection layer can resolve this difficulty. The gyroradii of PeV electrons are so large that their motion is insensitive to small-scale turbulent structures and is controlled only by large-scale fields. As these particles are accelerated by the reconnection electric field, their relativistic Speiser-like orbits collapse deep into the layer and get focused into a tight beam. Furthermore, since perpendicular magnetic field is small inside the layer, the radiation reaction there is suppressed, so the particles can reach higher energies and emit synchrotron radiation in excess of the 100 MeV limit, resolving the Crab gamma-ray flare paradox.

  1. A phenomenological model of solar flares

    NASA Technical Reports Server (NTRS)

    Colgate, S. A.

    1978-01-01

    The energy of solar flares is derived from the magnetic energy of fields convected to the sun's surface and subsequently converted to heat and energetic particles within the chromosphere. The circumstances of this conversion in most current models is magnetic flux annihilation at a neutral sheet. An analysis is conducted of the constraints of flux annihilation. It is shown that the present evidence of solar cosmic rays, X-rays, gamma-rays, and total energy suggests a choice of annihilation not at a neutral point, but by an enhanced dissipation of a field-aligned current. The field configuration is related both to its origin and to the extensive theory and laboratory experiments concerned with this configuration in magnetic fusion. The magnetic field model is applied to the August 4 flare. It is shown how the plasma heating in the annihilation region balanced by thermal conduction leads to a plasma temperature of about 20 million deg K.

  2. Millimeter Observation of Solar Flares with Polarization

    NASA Astrophysics Data System (ADS)

    Silva, D. F.; Valio, A. B. M.

    2016-04-01

    We present the investigation of two solar flares on February 17 and May 13, 2013, studied in radio from 5 to 405 GHz (RSTN, POEMAS, SST), and in X-rays up to 300 keV (FERMI and RHESSI). The objective of this work is to study the evolution and energy distribution of the population of accelerated electrons and the magnetic field configuration. For this we constructed and fit the radio spectrum by a gyro synchrotron model. The optically thin spectral indices from radio observations were compared to that of the hard X-rays, showing that the radio spectral index is harder than the latter by 2. These flares also presented 10-15 % circular polarized emission at 45 and 90 GHz that suggests that the sources are located at different legs of an asymmetric loop.

  3. A slingshot model for solar flares

    NASA Technical Reports Server (NTRS)

    Benford, Gregory

    1991-01-01

    Recent observations of intense, impulsive gamma-ray and X-ray-emitting solar flares underline the suddenness of these events. The simultaneous emission of X-rays greater than 40 keV from electron bremsstrahlung and gamma-rays requiring several MeV protons shows that all particles must be accelerated in less than 5 s. This paper proposes a simple model to explain such events, using the energy stored in the stretched field lines of a coronal arch. When reconnection occurs at the top of the arch, field lines retract like stretched rubber bands, sweeping up plasma and acting like a piston or slingshot. When the slug of plasma caught in the magnetic fields strikes the photosphere, it deposits its considerable kinetic energy, heating and compressing the intruding slug. Ten slugs of 100 km radius striking the photosphere may account for the 10 to the 29th ergs radiation from loop flares.

  4. High energy flare physics group summary

    NASA Technical Reports Server (NTRS)

    Ryan, J. M.; Kurfess, J. D.

    1989-01-01

    The contributions of the High Energy Flare Physics Special Session in the American Astronomical Society Solar Physics Division Meeting are reviewed. Oral and poster papers were presented on observatories and instruments available for the upcoming solar maximum. Among these are the space-based Gamma Ray Observatory, the Solar Flare and Cosmic Burst Gamma Ray Experiment on the Ulysses spacecraft, the Soft X Ray Telescope on the spacecraft Solar-A, and the balloon-based Gamma Ray Imaging Device. Ground based observatories with new capabilities include the BIMA mm-wave interferometer (Univ. of California, Berkeley; Univ. of Illinois; Univ. of Maryland), Owens Valley Radio Observatory and the Very Large Array. The highlights of the various instrument performances are reported and potential data correlations and collaborations are suggested.

  5. Solar flare irradiation records in Antarctic meteorites

    NASA Technical Reports Server (NTRS)

    Goswami, J. N.

    1981-01-01

    The observation of tracks from solar flare heavy nuclei in Antarctic meteorite samples is reported. In an analysis of nuclear track densities in eight L and H chondrites of low metamorphic grade, it was found that two interior specimens of sample 77216, an L-3 chondrite, contain olivine grains with track densities much higher than the average track densities, indicating precompaction irradiation by solar flares in different shielding conditions. Preliminary data from mass spectroscopic analyses show a large excess of noble gases, with a Ne-20/Ne-22 ratio of greater than or equal to 10, indicating the presence of solar-type noble gas. Results of track density measurements in the other Antarctic meteorites range from 10,000 to 4,000,000/sq cm, which is within the range observed in non-Antarctic L-group meteorites

  6. Carbon-poor solar flare events

    NASA Technical Reports Server (NTRS)

    Mason, G. M.; Gloeckler, G.; Hovestadt, D.

    1979-01-01

    A survey of energetic particle flux enhancements over the period from October 1973 to December 1977 has been performed by using the University of Maryland/Max-Planck-Institut ULET sensor on the IMP 8 spacecraft. During the four-year period of the study, it is found that the most extreme periods of Fe enrichment compared with oxygen were during solar flare events in February 1974 and May 1974. In these same events, the carbon abundance with respect to oxygen was significantly depleted when compared with a value C:O of about 0.45:1 for typical solar flares. These observations, taken together with previously reported He-3 enrichment in these events, give strong evidence for the importance of a wave-particle interaction in the preinjection heating of the ambient matter.

  7. Observational Constraints on Stellar Flares and Prominences

    NASA Astrophysics Data System (ADS)

    Aarnio, Alicia

    2016-07-01

    Multi-wavelength surveys have catalogued a wealth of stellar flare data for stars representing a broad range of masses and ages. Young solar analogs inform our understanding of the Sun's evolution and the influence of its activity on early solar system formation, while field star observations allow us to place its current activity into context within a statistical ensemble of main-sequence G-type stars. At the same time, stellar observations probe a variety of interior and coronal conditions, providing constraints on models of equilibrium (and loss thereof!) for magnetic structures. In this review, I will focus on our current understanding of stellar flares, prominences, and coronal mass ejections as a function of stellar parameters. As our interpretation of stellar data relies heavily on solar-stellar analogy, I will explore how far into extreme stellar parameter spaces this comparison can be invoked.

  8. Dynamics of flare sprays. [in sun

    NASA Technical Reports Server (NTRS)

    Tandberg-Hanssen, E.; Martin, S. F.; Hansen, R. T.

    1980-01-01

    During solar cycle No. 20 new insight into the flare-spray phenomenon has been attained due to several innovations in solar optical-observing techniques (higher spatial resolution cinema-photography, tunable passband filters, multislit spectroscopy and extended angular field coronagraphs). From combined analysis of 13 well-observed sprays which occurred between 1969-1974 it is concluded that (1) the spray material originates from a preexisting active region filament which undergoes increased absorption some tens of minutes prior to the abrupt chromospheric brightening at the 'flare-start', and (2) the spray material is confined within a steadily expanding, loop-shaped (presumable magnetically controlled) envelope with part of the materials draining back down along one or both legs of the loop.

  9. A NEW METHOD FOR CLASSIFYING FLARES OF UV Ceti TYPE STARS: DIFFERENCES BETWEEN SLOW AND FAST FLARES

    SciTech Connect

    Dal, H. A.; Evren, S.

    2010-08-15

    In this study, a new method is presented to classify flares derived from the photoelectric photometry of UV Ceti type stars. This method is based on statistical analyses using an independent samples t-test. The data used in analyses were obtained from four flare stars observed between 2004 and 2007. The total number of flares obtained in the observations of AD Leo, EV Lac, EQ Peg, and V1054 Oph is 321 in the standard Johnson U band. As a result flares can be separated into two types, slow and fast, depending on the ratio of flare decay time to flare rise time. The ratio is below 3.5 for all slow flares, while it is above 3.5 for all fast flares. Also, according to the independent samples t-test, there is a difference of about 157 s between equivalent durations of slow and fast flares. In addition, there are significant differences between amplitudes and rise times of slow and fast flares.

  10. [Motion sickness].

    PubMed

    Taillemite, J P; Devaulx, P; Bousquet, F

    1997-01-01

    Motion sickness is a general term covering sea-sickness, car-sickness, air-sickness, and space-sickness. Symptoms can occur when a person is exposed to unfamiliar movement whether real or simulated. Despite progress in the technology and comfort of modern transportation (planes, boats, and overland vehicles), a great number of travelers still experience motion sickness. Bouts are characterized by an initial phase of mild discomfort followed by neurologic and gastro-intestinal manifestations. The delay in onset depends on specific circumstances and individual susceptibility. Attacks are precipitated by conflicting sensory, visual, and vestibular signals but the underlying mechanism is unclear. Most medications used for prevention and treatment (e.g. anticholinergics and antihistamines) induce unwanted sedation. Furthermore no one drug is completely effective or preventive under all conditions.

  11. RHESSI and Trace Observations of the 21 April 2002 X1.5 Flare

    NASA Technical Reports Server (NTRS)

    Gallagher, Peter T.; Dennis, Brian R.; Krucker, Saem; Schwartz, Richard A.; Tolbert, A. Kimberly

    2002-01-01

    system. This "fan of spines" becomes visible well into the decay phase of the flare and shows evidence for both lateral and downward motions.

  12. Characteristics of Solar Flare Hard X-ray Emissions: Observations and Models

    NASA Astrophysics Data System (ADS)

    Liu, Wei

    2007-05-01

    The main theme of this dissertation is the investigation of the physics of acceleration and transport of particles in solar flares and their radiative signatures. The observational studies, using hard X-rays (HXRs) observed by RHESSI, concentrate on four flares, which support the classical magnetic reconnection model of flares in various ways. In the 11/03/2003 X3.9 flare, there is an upward motion of the loop-top source, accompanied by a systematic increase in the separation of the foot-point sources at a comparable speed. This is consistent with the reconnection model with an inverted-Y geometry. The 04/30/2002 M1.3 event exhibits rarely observed two coronal sources, with very similar spectra and their higher-energy emission being close together. This suggests that reconnection occurs between the two sources. In the 10/29/2003 X10 flare, the logarithmic total HXR flux of the two foot-points correlates with their mean magnetic field. The foot-points show asymmetric HXR fluxes, qualitatively consistent with the magnetic mirroring effect. The 11/13/2003 M1.7 flare reveals evidence of chromospheric evaporation directly imaged by RHESSI for the first time. The emission centroids move toward the loop-top, indicating a density increase in the loop. The theoretical modeling of this work combines the Stanford stochastic acceleration model with the NRL hydrodynamic model to study the interplay of the particle acceleration, transport, and radiation effects and the atmospheric response to the energy deposition by electrons. I find that low-energy electrons in the quasi-thermal portion of the spectrum affects the hydrodynamics by producing more heating in the corona than the previous models that used a power-law spectrum with a low-energy cutoff. The Neupert effect is found to be present and effects of suppression of thermal conduction are tested in the presence of hydrodynamic flows. I gratefully thank my adviser, Prof. Vahe' Petrosian, my collaborators, and funding support

  13. A Cold Flare with Delayed Heating

    NASA Astrophysics Data System (ADS)

    Fleishman, Gregory D.; Pal'shin, Valentin D.; Meshalkina, Natalia; Lysenko, Alexandra L.; Kashapova, Larisa K.; Altyntsev, Alexander T.

    2016-05-01

    Recently, a number of peculiar flares have been reported that demonstrate significant nonthermal particle signatures with low, if any, thermal emission, which implies a close association of the observed emission with the primary energy release/electron acceleration region. This paper presents a flare that appears “cold” at the impulsive phase, while displaying delayed heating later on. Using hard X-ray data from Konus-Wind, microwave observations by SSRT, RSTN, NoRH, and NoRP, context observations, and three-dimensional modeling, we study the energy release, particle acceleration, and transport, and the relationships between the nonthermal and thermal signatures. The flaring process is found to involve the interaction between a small loop and a big loop with the accelerated particles divided roughly equally between them. Precipitation of the electrons from the small loop produced only a weak thermal response because the loop volume was small, while the electrons trapped in the big loop lost most of their energy in the coronal part of the loop, which resulted in coronal plasma heating but no or only weak chromospheric evaporation, and thus unusually weak soft X-ray emission. The energy losses of the fast electrons in the big tenuous loop were slow, which resulted in the observed delay of the plasma heating. We determined that the impulsively accelerated electron population had a beamed angular distribution in the direction of the electric force along the magnetic field of the small loop. The accelerated particle transport in the big loop was primarily mediated by turbulent waves, which is similar to other reported cold flares.

  14. The Discriminant Analysis Flare Forecasting System (DAFFS)

    NASA Astrophysics Data System (ADS)

    Leka, K. D.; Barnes, Graham; Wagner, Eric; Hill, Frank; Marble, Andrew R.

    2016-05-01

    The Discriminant Analysis Flare Forecasting System (DAFFS) has been developed under NOAA/Small Business Innovative Research funds to quantitatively improve upon the NOAA/SWPC flare prediction. In the Phase-I of this project, it was demonstrated that DAFFS could indeed improve by the requested 25% most of the standard flare prediction data products from NOAA/SWPC. In the Phase-II of this project, a prototype has been developed and is presently running autonomously at NWRA.DAFFS uses near-real-time data from NOAA/GOES, SDO/HMI, and the NSO/GONG network to issue both region- and full-disk forecasts of solar flares, based on multi-variable non-parametric Discriminant Analysis. Presently, DAFFS provides forecasts which match those provided by NOAA/SWPC in terms of thresholds and validity periods (including 1-, 2-, and 3- day forecasts), although issued twice daily. Of particular note regarding DAFFS capabilities are the redundant system design, automatically-generated validation statistics and the large range of customizable options available. As part of this poster, a description of the data used, algorithm, performance and customizable options will be presented, as well as a demonstration of the DAFFS prototype.DAFFS development at NWRA is supported by NOAA/SBIR contracts WC-133R-13-CN-0079 and WC-133R-14-CN-0103, with additional support from NASA contract NNH12CG10C, plus acknowledgment to the SDO/HMI and NSO/GONG facilities and NOAA/SWPC personnel for data products, support, and feedback. DAFFS is presently ready for Phase-III development.

  15. X-rays Flares and Protoplanetary Disks

    NASA Astrophysics Data System (ADS)

    Feigelson, Eric D.

    2011-04-01

    X-ray observations of star forming regions show that magnetic reconnection flares are powerful and frequent in pre-main sequence solar-type stars. Well-defined samples in the Orion Nebula Cluster and Taurus clouds exhibit flares with peak X- ray luminosities Lx˜10^29 - 10^32 erg/s, orders of magnitude stronger and more frequent than contemporary solar flares. X-rays are emitted in magnetic loops extending 0.1-10 R * above the stellar surface and thus have a favorable geometry to irradiate the protoplanetary disk. Several lines of evidence - fluorescent iron X-ray emission line, forbidden [NeII] infrared line, and excited molecular bands - support X-ray irradiation of cold material in some young systems. Several astrophysical consequences of X-ray irradiation are outlined. As ionization fractions need only reach 10-12 to induce the magnetorotational instability and associated turbulence, X-rays may be the principal determinant of the extent of the viscous "active zone" and laminar "dead zone" in the layered accretion disk. X-ray irradiation may thus play a major role in planet formation processes: particle settling; meter-size inspiral; protoplanetary migration; and dissipation of the gaseous disk.

  16. Explosive plasma flows in a solar flare

    NASA Technical Reports Server (NTRS)

    Zarro, Dominic M.; Canfield, Richard C.; Metcalf, Thomas R.; Strong, Keith T.

    1988-01-01

    Solar Maximum Mission soft X-ray data and Sacramento Peak Observatory H-alpha observations are combined in a study of the impulsive phase of a solar flare. A blue asymmetry, indicative of upflows, was observed in the coronal Ca XIX line during the soft X-ray rise phase. A red asymmetry, indicative of downflows, was observed simultaneously in chromospheric H-alpha emitted from bright flare kernels during the period of hard X-ray emission. Combining the velocity data with a measurement of coronal electron density, it is shown that the impulsive phase momentum of upflowing soft X-ray-emitting plasma equalled that of the downflowing H-alpha-emitting plasma to within one order of magnitude. In particular, the momentum of the upflowing plasma was 2 x 10 to the 21st g cm/s while that of the downflowing plasma was 7 x 10 to the 21st g cm/s, with a factor of 2 uncertainty on each value. This equality supports the explosive chromospheric evaporation model of solar flares, in which a sudden pressure increase at the footprint of a coronal loop produces oppositely directed flows in the heated plasma.

  17. Solar Aurora and a White Light Flare

    NASA Astrophysics Data System (ADS)

    Haerendel, Gerhard

    2016-07-01

    A white light flare analyzed by Krucker et al. (2011) poses a severe challenge to the solar physicist because of the high energy fluxes implied by a hitherto not achieved spatial resolution of simultaneous observations with Hinode and RHESSI. A scenario based on the auroral acceleration mechanism applied to flare conditions, 'Solar Aurora', is able to reproduce the observations, but implies several far-reaching assumptions on the mechanism as well as on the environmental parameters. Unavoidable consequences exist with regard to the spatial and temporal scales. They are extremely short because of the high density of the corona and the need for an energy conversion process involving some kind of anomalous resistivity, i.e. extremely high electric current densities. A further postulate is that of spontaneous propagation of an energy conversion front (ENF), once established, in three dimensions. It is assumed that about one half of the converted energy appears in form of runaway electrons. Obliqueness of the ENFs prevents the existence of a return current problem for the emerging runaway electrons. The key flare parameters are formulated quantitatively in terms of the environmental properties. Transverse length scales turn out to be in the ten centimeter range, time-scales in the range of one millisecond. The energy conversion occurs in 10E3 -10E4 ENFs just above the transition region in a background field of the order of 2000 G. Observational consequences are being discussed.

  18. Structures in the Algol Corona: Searching for Flare Eclipses

    NASA Astrophysics Data System (ADS)

    Favata, Fabio

    Our recent successful observation of a total eclipse of a large flare on Algol (with BeppoSAX) has demonstrated the diagnostic power of flare eclipses, allowing for the first time to derive the size of the coronal structure responsible for a stellar flare (and thus by inference the size of coronal structures in general) on purely geometrical grounds. The loop is compact, much smaller than deduced by the analysis of the flare decay, and located on the pole of the active star. We propose to observe Algol for two binary orbits searching for similar flare eclipses. Further detections of flare eclipses (for which RXTE, with its large effective area is ideally suited) will allow to directly constrain the characteristic sized of structures in the Algol corona.

  19. Nonpotential magnetic fields at sites of gamma-ray flares

    NASA Technical Reports Server (NTRS)

    Hagyard, M. J.; Venkatakrishnan, P.; Smith, J. B., Jr.

    1990-01-01

    The relation between the degree of nonpotentiality of photospheric magnetic fields and the occurrence of gama-ray flares is examined to determine whether there are special signatures of the stressed fields for this type of flare. Observations of the flares in the active region of April 1984 (AR 4474) are analyzed, showing that the big flare initiated at the location on the magnetic neutral line where the field deviated the most from a potential field. The nonpotential signatures of AR 4474 are compared with those of four other regions. The results suggest that gamma-ray flares are associated with strongly nonpotential fields that extend over relatively larger lengths of the magnetic neutral line that the fields associated with flares that do not produce gamma-ray events.

  20. Nonpotential magnetic fields at sites of gamma-ray flares

    SciTech Connect

    Hagyard, M.J.; Venkatakrishnan, P.; Smith, J.B. Jr.

    1990-06-01

    The relation between the degree of nonpotentiality of photospheric magnetic fields and the occurrence of gama-ray flares is examined to determine whether there are special signatures of the stressed fields for this type of flare. Observations of the flares in the active region of April 1984 (AR 4474) are analyzed, showing that the big flare initiated at the location on the magnetic neutral line where the field deviated the most from a potential field. The nonpotential signatures of AR 4474 are compared with those of four other regions. The results suggest that gamma-ray flares are associated with strongly nonpotential fields that extend over relatively larger lengths of the magnetic neutral line that the fields associated with flares that do not produce gamma-ray events. 9 refs.

  1. Multi-thermal observations of newly formed loops in a dynamic flare

    NASA Technical Reports Server (NTRS)

    Svestka, Zdenek F.; Fontenla, Juan M.; Machado, Marcos E.; Martin, Sara F.; Neidig, Donald F.

    1987-01-01

    The dynamic flare of November 6, 1980 (max at about 15:26 UT) developed a rich system of growing loops which could be followed in H-alpha for 1.5 hr. Throughout the flare, these loops, near the limb, were seen in emission against the disk. Theoretical computations of deviations from LTE populations for a hydrogen atom reveal that this requires electron densities in the loops close to, or in excess of 10 to the 12th/cu cm. From measured widths of higher Balmer lines the density at the tops of the loops was found to be 4 x 10 to the 12th/cu cm if no nonthermal motions were present, or 5 x 10 to the 11th/cu cm for a turbulent velocity of about 12 km/s. It is now general knowledge that flare loops are initially observed in X-rays and become visible in H-alpha only after cooling. For such a high density, a loop would cool through radiation from 10 to the 7th to 10 to the 4th K within a few minutes so that the dense H-alpha loops should have heights very close to the heights of the X-ray loops. This, however, contradicts the observations obtained by the HXIS and FCS instruments on board SMM which show the X-ray loops at much higher altitudes than the loops in H-alpha. Therefore, it is suggested that the density must have been significantly lower when the loops were formed, and that the flare loops were apparently both shrinking and increasing in density while cooling.

  2. MULTIWAVELENGTH IMAGING AND SPECTROSCOPY OF CHROMOSPHERIC EVAPORATION IN AN M-CLASS SOLAR FLARE

    SciTech Connect

    Veronig, A. M.; Berkebile-Stoiser, S.; Temmer, M.; Rybak, J.; Goemoery, P.; Otruba, W.; Poetzi, W.; Baumgartner, D.

    2010-08-10

    We study spectroscopic observations of chromospheric evaporation mass flows in comparison with the energy input by electron beams derived from hard X-ray (HXR) data for the white-light M2.5 flare of 2006 July 6. The event was captured in high-cadence spectroscopic observing mode by SOHO/CDS combined with high-cadence imaging at various wavelengths in the visible, extreme ultraviolet, and X-ray domain during the joint observing campaign JOP171. During the flare peak, we observe downflows in the He I and O V lines formed in the chromosphere and transition region, respectively, and simultaneous upflows in the hot coronal Si XII line. The energy deposition rate by electron beams derived from RHESSI HXR observations is suggestive of explosive chromospheric evaporation, consistent with the observed plasma motions. However, for a later distinct X-ray burst, where the site of the strongest energy deposition is exactly located on the Coronal Diagnostics Spectrometer (CDS) slit, the situation is intriguing. The O V transition region line spectra show the evolution of double components, indicative of the superposition of a stationary plasma volume and upflowing plasma elements with high velocities (up to 280 km s{sup -1}) in single CDS pixels on the flare ribbon. However, the energy input by electrons during this period is too small to drive explosive chromospheric evaporation. These unexpected findings indicate that the flaring transition region is much more dynamic, complex, and fine structured than is captured in single-loop hydrodynamic simulations.

  3. The nature of the γ-ray flare associated with blazar 3C 454.3

    NASA Astrophysics Data System (ADS)

    Hu, Wen; Fan, Zhong-Hui; Dai, Ben-Zhong

    2015-09-01

    We have studied the simultaneous spectral energy distributions (SEDs) of the 2009 December flare and those of the quiescent state of blazar 3C 454.3 by constructing a multi-component model. We find that all six SEDs can be explained by a one-zone leptonic model involving synchrotron self-Compton (SSC) plus external Compton emission from an accretion disk (ECD) and that from a broad-line region (ECC). X-ray emission is dominated by the SSC mechanism, and the γ-ray spectrum is well represented by a combination of ECD and ECC processes. Our results indicate that the energy density of the magnetic field and electrons decrease with distance from the central engine, and the Doppler factor increases with the blob moving outward in the development of the 2009 December flare. The increase in the observed flux density is possibly due to the increase in the Doppler factor of the blob. The relation between the Doppler factor δb and the distance from the central black hole suggests the magnetically driven jets span a sub-pc scale, and the relation between the magnetic field B' and the dimension of the emission region R'b is in good agreement with what is required by conservation of magnetic flux. The weak “harder-when-brighter” behavior of the γ-ray spectrum could be a result of the increase in Doppler factor during the outward motion of the blob. The parameters during the quiescent state obviously deviate from those during the flare state. We propose that the flare was likely caused by the ejection of a new blob. The gamma-ray emissions in different states are associated with the evolution of the blob.

  4. Extreme-Ultraviolet Spectroscopic Observation of Direct Coronal Heating During a C-Class Solar Flare

    NASA Technical Reports Server (NTRS)

    Brosius, Jeffrey W.

    2012-01-01

    With the Coronal Diagnostic Spectrometer operating in rapid cadence (9.8 s) stare mode during a C6.6 flare on the solar disk, we observed a sudden brightening of Fe xix line emission (formed at temperature T ˜ 8 MK) above the pre-flare noise without a corresponding brightening of emission from ions formed at lower temperatures, including He i (0.01 MK), Ov (0.25 MK), and Si xii (2 MK). The sudden brightening persisted as a plateau of Fe xix intensity that endured more than 11 minutes. The Fe xix emission at the rise and during the life of the plateau showed no evidence of significant bulk velocity flows, and hence cannot be attributed to chromospheric evaporation. However, the line width showed a significant broadening at the rise of the plateau, corresponding to nonthermal velocities of at least 89 km s-1 due to reconnection outflows or turbulence. During the plateau He i, Ov, and Si xii brightened at successively later times starting about 3.5 minutes after Fe xix, which suggests that these brightenings were produced by thermal conduction from the plasma that produced the Fe xix line emission; however, we cannot rule out the possibility that they were produced by a weak beam of nonthermal particles. We interpret an observed shortening of the Ov wavelength for about 1.5 minutes toward the middle of the plateau to indicate new upward motions driven by the flare, as occurs during gentle chromospheric evaporation; relative to a quiescent interval shortly before the flare, the Ov upward velocity was around -10 km s-1.

  5. Black Carbon Emissions from Associated Natural Gas Flaring

    NASA Astrophysics Data System (ADS)

    Weyant, C.; Shepson, P. B.; Subramanian, R.; Cambaliza, M. O. L.; Mccabe, D. C.; Baum, E. K.; Caulton, D.; Heimburger, A. M. F.; Bond, T. C.

    2014-12-01

    Approximately 150 billion cubic meters (BCM) of associated natural gas is flared and vented in the world, annually, emitting greenhouse gases and other pollutants with no energy benefit. Based on estimates from satellite observations, the United States flares about 7 BCM of gas, annually (the 5th highest flaring volume worldwide). The volume of gas flared in the US is growing, largely due to flaring in the Bakken formation in North Dakota. Black carbon (BC), a combustion by-product from gas flaring, is a short-term climate pollutant that absorbs shortwave radiation both in the atmosphere and on snow and ice surfaces. Flaring may be a significant source of global BC climate effects. For example, modeling estimates suggest that associated gas flares are the source of a significant percentage of BC surface concentrations in the Arctic, where BC-induced ice melting occurs. However, there are no direct field measurements of BC emission factors from associated gas flares. Emission measurements of BC that include a range of flaring conditions are needed to ascertain the magnitude of BC emissions from this source. Over one hundred flare plumes were sampled in the Bakken formation using a small aircraft. Methane, carbon dioxide, and BC were measured simultaneously, allowing the calculation of BC mass emission factors using the carbon balance method. BC was measured using two methods; optical absorption was measured using a Particle Soot Absorption Photometer (PSAP) and BC particle number and mass concentrations were measured with a Single Particle Soot Photometer (SP2). Simultaneous sampling of BC absorption and mass allows for the calculation of the BC mass absorption cross-section. Results indicate that emission factor variability between flares in the region is significant; there are two orders of magnitude variation in the BC emission factors.

  6. Astro-D observations of flares: Detecting the impulsive phase

    NASA Technical Reports Server (NTRS)

    Haisch, Bernhard

    1995-01-01

    The flare star Proxima Centauri was observed by the satellite for approximately 50 ks and a number of flares were successfully detected. The scientific results were presented at several meetings and were discussed in articles, primarily in 'Solar-like M-Class X-ray Flares on Proxima Centauri Observed by the ASCA Satellite' by Haisch, Antunes and Schmitt, Science, Vol. 268, pp. 1327-1329, attached to the report.

  7. Sun Unleashes an X-Class Flare on March 11, 2015

    NASA Video Gallery

    The sun released an X-class flare, an X2.2, on March 11, 2015. In this video, the flare itself is not very impressive. However, solar material can be seen blasting away from the flare location. Cre...

  8. Analysis of coordinated observations of a giant stellar flare

    NASA Technical Reports Server (NTRS)

    Lambert, David L.

    1989-01-01

    Multi-wavelength observations of a giant flare on the star AD Leo were obtained with the 2.1 m and 0.9 m telescopes at McDonald Observatory and the International Ultraviolet Explorer satellite. The quality, spectral coverage, and time resolution of the data represented a major improvement over any published stellar flare data. Two theoretical, quantitative flare models were developed. Combining the models, the chromospheric emission model predictions in the hydrogen Balmer lines, Da II K, Mg II h + k and the optical continuum were compared to the observations, with the result that much of the gradual phase flare emission could be produced by the x ray and conductive heated atmospheres. The models lend insight into the impulsive phase flare emission, but do not reproduce it. Soft x ray and conductive heating of the chromosphere is a natural consequence of the coronal temperatures that have been observed during the gradual phase of flares on the sun and on M dwarf stars. The improved flare observations and quantitative flare models presented here show that these heating mechanisms can produce atmospheres whose emission matches many of the observed stellar flare features.

  9. Investigation of physical parameters in stellar flares observed by GINGA

    NASA Technical Reports Server (NTRS)

    Stern, Robert A.

    1994-01-01

    This program involves analysis and interpretation of results from GINGA Large Area Counter (LAC) observations from a group of large stellar X-ray flares. All LAC data are re-extracted using the standard Hayashida method of LAC background subtraction and analyzed using various models available with the XSPEC spectral fitting program.Temperature-emission measure histories are available for a total of 5 flares observed by GINGA. These will be used to compare physical parameters of these flares with solar and stellar flare models.

  10. Investigation of physical parameters in stellar flares observed by GINGA

    NASA Technical Reports Server (NTRS)

    Stern, Robert A.

    1994-01-01

    This program involves analysis and interpretation of results from GINGA Large Area Counter (LAC) observations from a group of large stellar x-ray flares. All LAC data are re-extracted using the standard Hayashida method of LAC background subtraction and analyzed using various models available with the XSPEC spectral fitting program. Temperature-emission measure histories are available for a total of 5 flares observed by GINGA. These will be used to compare physical parameters of these flares with solar and stellar flare models.

  11. Nucleosynthesis of Li-7 in flares on UV Ceti stars

    NASA Technical Reports Server (NTRS)

    Karpen, J. T.; Worden, S. P.

    1979-01-01

    The possible production of Li-7 by nuclear reactions in UV Ceti flares has been considered. By utilizing solar observations and theory, a relationship is derived between flare energy and production rates for Li-7; approximately 100 erg of total flare energy is found to denote the formation of a Li-7 atom. Based on this value and best estimates of UV Ceti-type flare rates, it is concluded that less than 10% of the Li-7 observed in the intestellar medium may have been produced by this mechanism. Formation of significant amounts of interstellar deuterium by this method is ruled out.

  12. Some properties of flare-not-associated Forbush decreases

    NASA Astrophysics Data System (ADS)

    Iucci, N.; Parisi, M.; Signorini, C.; Storini, M.; Villoresi, G.

    1984-07-01

    All non flare-associated Forbush decreases (N Ass Fds) over the period 1957 to 1979 are investigated. The connection between N Ass Fds occurrence and the central meridian passage of strong active regions producing great flare associated Fds shows the flare origin of the N Ass Fds. The interplanetary perturbations at the eastern and western boundaries of the modulated region are found to be long living corotating structures. These structures mark the boundaries of the region in which the (1 to 4 Mev) protons accelerated by interplanetary flare generated shocks are confined.

  13. Comment on 'The solar flare myth' by J. T. Gosling

    NASA Technical Reports Server (NTRS)

    Hudson, Hugh; Haisch, Bernhard; Strong, Keith T.

    1995-01-01

    In a recent paper Gosling (1993) claims that solar flares are relatively unimportant for understanding the terrestrial consequences of solar activity, and argues that coronal mass ejections (CMEs) produce the most powerful terrestrial disturbances. This opinion conflicts with observation, as it is well known that CMEs and flares are closely associated, and we disagree with Gosling's insistence on a simplistic cause-and-effect description of the interrelated phenomena of a solar flare. In this brief response we present new Yohkoh data and review older results that demonstrate the close relationships among CMEs, flares, filament eruptions, and other forms of energy release such as particle acceleration.

  14. Nuclear processes and neutrino production in solar flares

    NASA Technical Reports Server (NTRS)

    Lingenfelter, R. E.; Ramaty, R.; Murphy, R. J.; Kozlovsky, S.

    1985-01-01

    The determination of flare neutrino flux is approached from the standpoint of recent observations and theoretical results on the nuclear processes in solar flares. Attention is given to the energy spectra and total numbers of accelerated particles in flares, as well as their resulting production of beta(+)-emitting radionuclei and pions; these should be the primary sources of neutrinos. The observed 0.511 MeV line flux for the June 21, 1980 flare is compared with the expected from the number and spectrum of accelerated particles.

  15. TOWARD RELIABLE BENCHMARKING OF SOLAR FLARE FORECASTING METHODS

    SciTech Connect

    Bloomfield, D. Shaun; Higgins, Paul A.; Gallagher, Peter T.; McAteer, R. T. James

    2012-03-10

    Solar flares occur in complex sunspot groups, but it remains unclear how the probability of producing a flare of a given magnitude relates to the characteristics of the sunspot group. Here, we use Geostationary Operational Environmental Satellite X-ray flares and McIntosh group classifications from solar cycles 21 and 22 to calculate average flare rates for each McIntosh class and use these to determine Poisson probabilities for different flare magnitudes. Forecast verification measures are studied to find optimum thresholds to convert Poisson flare probabilities into yes/no predictions of cycle 23 flares. A case is presented to adopt the true skill statistic (TSS) as a standard for forecast comparison over the commonly used Heidke skill score (HSS). In predicting flares over 24 hr, the maximum values of TSS achieved are 0.44 (C-class), 0.53 (M-class), 0.74 (X-class), 0.54 ({>=}M1.0), and 0.46 ({>=}C1.0). The maximum values of HSS are 0.38 (C-class), 0.27 (M-class), 0.14 (X-class), 0.28 ({>=}M1.0), and 0.41 ({>=}C1.0). These show that Poisson probabilities perform comparably to some more complex prediction systems, but the overall inaccuracy highlights the problem with using average values to represent flaring rate distributions.

  16. A CLASSIFICATION SCHEME FOR TURBULENT ACCELERATION PROCESSES IN SOLAR FLARES

    SciTech Connect

    Bian, Nicolas; Kontar, Eduard P.; Emslie, A. Gordon E-mail: eduard@astro.gla.ac.uk

    2012-08-01

    We establish a classification scheme for stochastic acceleration models involving low-frequency plasma turbulence in a strongly magnetized plasma. This classification takes into account both the properties of the accelerating electromagnetic field, and the nature of the transport of charged particles in the acceleration region. We group the acceleration processes as either resonant, non-resonant, or resonant-broadened, depending on whether the particle motion is free-streaming along the magnetic field, diffusive, or a combination of the two. Stochastic acceleration by moving magnetic mirrors and adiabatic compressions are addressed as illustrative examples. We obtain expressions for the momentum-dependent diffusion coefficient D(p), both for general forms of the accelerating force and for the situation when the electromagnetic force is wave-like, with a specified dispersion relation {omega} = {omega}(k). Finally, for models considered, we calculate the energy-dependent acceleration time, a quantity that can be directly compared with observations of the time profile of the radiation field produced by the accelerated particles, such as those occuring during solar flares.

  17. Ultraviolet Events Observed in Active Regions. 2; An Interpretation of Flaring Arches and Associated Small Flares

    NASA Technical Reports Server (NTRS)

    Fontenla, J.; Rovira, M.; Tandberg-Hanssen, E.

    1997-01-01

    We analyze Hz, UV, and X-ray emissions in and around the spectacular arch system seen in the corona on 1980 March 27 during the Solar Maximum Mission. The flaring of the arch plasma is studied, and its dependence on triggering mechanisms related to the observed small limb flare in the arch footpoint is analyzed. To drive these events, we propose a mechanism in which small electric current circuits and the localized magnetic free energy are continuously generated at a magnetic null by a pressure gradient, which then compress or expand the plasma. This free energy dissipates by Joule effect and upward transport.

  18. Nonpotential magnetic fields at sites of gamma ray flares

    NASA Technical Reports Server (NTRS)

    Hagyard, M. J.; Venkatakrishnan, P.; Smith, J. B., Jr.

    1988-01-01

    The relation between the degree of nonpotentiality of photospheric magnetic fields and the occurrence of gamma ray flares is examined. The parameter delta phi (magnetic shear) and the strength of the magnetic field intensity are used as measures of the degree of nonpotentiality, where delta phi is defined as the angular difference between the observed direction of the transverse component of the photospheric field and the direction of the potential field prescribed by the distribution of measured photospheric flux. An analysis of the great flare of April 24 to 25, 1984 is presented as an example of this technique to quantify the nonpotential characteristics of the pre-flare magnetic field. For this flare, which produced a large gamma ray event, strong shear and high field strengths prevailed over an extended length of the magnetic neutral line where the flare occurred. Moreover, the flare began near the area of strongest measured shear (89 to 90 deg). Four other flaring regions were analyzed; one of these produced a moderate gamma ray event while the other three did not produce detectable gamma rays. For all four regions the flares were located in the area where the field was not nonpotential, regardless of the class of flare. The fields of the gamma ray flares were compared with those associated with the flares without gamma rays, and little distinction was found in the degree of magnetic shear. The major difference is seen in the extent of the sheared field: for gamma ray events, the field is sheared over a longer length of the neutral line.

  19. Flare heating and ionization of the low solar chromosphere. II - Observations of five solar flares

    NASA Technical Reports Server (NTRS)

    Metcalf, Thomas R.; Canfield, Richard C.; Saba, Julia L. R.

    1990-01-01

    Two neutral Mg spectral lines formed in the temperature-minimum region and the low chromosphere, at 4571 and 5173 A, are used to quantify the changes in the atmospheric structure as a function of time during five solar flares. Eight proposed flare heating and ionization mechanisms and predictions of the effects of each on the temperature minimum region are discussed. Two Mg spectral observations made at the National Solar Observatory (Sacramento Peak), along with observations of hard and soft X-rays from the SMM and GOES satellites, are compared to the predictions of the eight proposed mechanisms. The initial effects in all five flares are consistent with backwarming by enhanced Balmer- and Paschen-continuum radiation originating in the upper chromosphere. Extended heating observed in two of the flares is most likely due to UV irradiation. In all cases heating by the dissipation of nonreversed electric currents, collisions with an electron or proton beam, irradiation by soft X-rays, and dissipation of Alfven waves are eliminated.

  20. EGRET High Energy Capability and Multiwavelength Flare Studies and Solar Flare Proton Spectra

    NASA Technical Reports Server (NTRS)

    Chupp, Edward L.

    1998-01-01

    The accomplishments of the participation in the Compton Gamma Ray Observatory Guest investigator program is summarized in this report. The work involved the study of Energetic Gamma Ray Experiment Telescope (EGRET)/Total Absorption Shower Counter(TASC) flare data. The specific accomplishments were the use of the accelerator neutron measurements obtained at the University of New Hampshire to verify the TASC response function and to modify the TASC fitting program to include a high energy neutron contribution, and to determine a high energy neutron contribution to the emissions from the 1991 June 11, solar flare. The next step in the analysis of this event was doing fits to the TASC energy-loss spectra as a function of time. A significant hardening of the solar proton spectrum over time was found for the flare. Further data was obtained from the Yohkoh HXT time histories and images for the 1991 October 27 flare. The results to date demonstrate that the TASC spectral analysis contributes crucial information on the particle spectrum interacting at the Sun. The report includes a paper accepted for publication, a draft of a paper to be delivered at the 26th International Cosmic Ray Conference and an abstract of a paper to be presented at the Meeting of the American Physical Society.

  1. EGRET High Energy Capability and Multiwavelength Flare Studies and Solar Flare Proton Spectra

    NASA Technical Reports Server (NTRS)

    Chupp, Edward L.

    1997-01-01

    UNH was assigned the responsibility to use their accelerator neutron measurements to verify the TASC response function and to modify the TASC fitting program to include a high energy neutron contribution. Direct accelerator-based measurements by UNH of the energy-dependent efficiencies for detecting neutrons with energies from 36 to 720 MeV in NaI were compared with Monte Carlo TASC calculations. The calculated TASC efficiencies are somewhat lower (by about 20%) than the accelerator results in the energy range 70-300 MeV. The measured energy-loss spectrum for 207 MeV neutron interactions in NaI were compared with the Monte Carlo response for 200 MeV neutrons in the TASC indicating good agreement. Based on this agreement, the simulation was considered to be sufficiently accurate to generate a neutron response library to be used by UNH in modifying the TASC fitting program to include a neutron component in the flare spectrum modeling. TASC energy-loss data on the 1991 June 11 flare was transferred to UNH. Also included appendix: Gamma-rays and neutrons as a probe of flare proton spectra: the solar flare of 11 June 1991.

  2. Flare Comparisons of the Flare Irradiance Spectral Model (FISM) to Preliminary SDO EVE Data

    NASA Technical Reports Server (NTRS)

    Chamberlon, Phillip C.

    2010-01-01

    The Solar Dynamics Observatory (SDO) launched February 11, 2010 from Kennedy Space Center and started normal science operations in April 2010. One of the instruments onboard SDO, the EUV Variability- Experiment (EVE), will measure the solar EUV irradiance from 0.1-105 nm with 0.1 nm spectral resolution as well as a measure of the broad-band Lyman-Alpha emission (121.0 rim), all with less than 10 percent uncertainties. One of the biggest improvements of EVE over its predecessors is its ability to continuously measure the complete spectrum ever y 10 seconds, 24 hours a day, 7 days a week. This temporal coverage and cadence will greatly enhance the knowledge of the solar EUV variations during solar flares. This paper will present a comparison of the Flare Irradiance Spectral Model (FISM), which can produce an estimated EUV spectrum at 10 seconds temporal resolution, to the preliminary flare observation results from SDO EVE. The discussion will focus on the short-term EUV flare variations and evolution.

  3. Motion Simulator

    NASA Technical Reports Server (NTRS)

    1993-01-01

    MOOG, Inc. supplies hydraulic actuators for the Space Shuttle. When MOOG learned NASA was interested in electric actuators for possible future use, the company designed them with assistance from Marshall Space Flight Center. They also decided to pursue the system's commercial potential. This led to partnership with InterActive Simulation, Inc. for production of cabin flight simulators for museums, expositions, etc. The resulting products, the Magic Motion Simulator 30 Series, are the first electric powered simulators. Movements are computer-guided, including free fall to heighten the sense of moving through space. A projection system provides visual effects, and the 11 speakers of a digital laser based sound system add to the realism. The electric actuators are easier to install, have lower operating costs, noise, heat and staff requirements. The U.S. Space & Rocket Center and several other organizations have purchased the simulators.

  4. Data Set of Flare-Ribbon Reconnected Magnetic Fluxes: A Critical Tool for Understanding Solar Flares and Eruptions

    NASA Astrophysics Data System (ADS)

    Kazachenko, M.; Lynch, B. J.; Welsch, B. T.

    2015-12-01

    Flare ribbons are emission structures that are frequently observed during flares in transition-region and chromospheric radiation. These typically straddle a polarity inversion line (PIL) of the radial magnetic field at the photosphere, and move apart as the flare progresses. The ribbon flux - the amount of unsigned photospheric magnetic flux swept out by flare ribbons - is thought to be related to the amount coronal magnetic reconnection, and hence provides a key diagnostic tool for understanding the physical processes at work in flares and CMEs. Previous measurements of the magnetic flux swept out by flare ribbons required time-consuming co-alignment between magnetograph and intensity data from different instruments, explaining why those studies only analyzed, at most, a few events. The launch of the Helioseismic and Magnetic Imager (HMI) and the Atmospheric Imaging Assembly (AIA), both aboard the Solar Dynamics Observatory (SDO), presented a rare opportunity to compile a much larger sample of flare-ribbon events than could readily be assembled before. We created a dataset of 141 events of both flare ribbon positions and fluxes, as a function of time, for all C9.-class and greater flares within 45 degrees of disk center observed by SDO from January 2013 till April 2015. For this purpose, we used vector magnetograms (2D magnetic field maps) from HMI and UV images from AIA. A critical problem with using unprocessed AIA data is the existence of spurious intensities in AIA data associated with strong flare emission, most notably "blooming" (spurious smearing of saturated signal into neighboring pixels, often in streaks). To overcome this difficulty, we have developed an algorithmic procedure that effectively excludes artifacts like blooming. We present our database and compare statistical properties of flare ribbons, e.g. evolutions of ribbon reconnection fluxes and reconnection flux rates, with the properties from theoretical models.

  5. NIR Flare of PKS2032+107

    NASA Astrophysics Data System (ADS)

    Carrasco, L.; Miramon, J.; Recillas, E.; Porras, A.; Chabushyan, V.; Carraminana, A.; Mayya, D.

    2013-11-01

    We have observed a recent NIR flare of the intermediate redshift quasar PKS2032+107. This radio source is cross identified with the gamma ray source 2FGLJ2035.4+1058 and the optical source BZQJ2035+1056. From observations carried out on November 12th, 2013 (JD 2456608.603380), we determined the following photometric values H = 13.452 +/- 0.03, J = 14.628 +/- 0.03 and Ks = 12.777 +/- 0.05. Our previous NIR photometry of the object (JD2456595.644780) yielded the value: H = 15.012 =/- 0.05.

  6. Spectrometers for fast neutrons from solar flares.

    PubMed

    Slobodrian, R J; Potvin, L; Rioux, C

    1994-10-01

    Neutrons with energies exceeding 1 GeV are emitted in the course of solar flares. Suitable dedicated neutron spectrometers with directional characteristics are necessary for a systematic spectroscopy of solar neutrons. We report here a study of instruments based on the detection of proton recoils from hydrogenous media, with double scattering in order to provide directional information, and also a novel scheme based on the detection of radiation from the neutron magnetic dipole moment, permitting also directional detection of neutrons. Specific designs and detection systems are discussed.

  7. Proxima Centauri: Rotation, Chromosperic Activity, and Flares

    NASA Astrophysics Data System (ADS)

    Guinan, E. F.; Morgan, N. D.

    1996-05-01

    At a distance of 4.3 LY, Proxima Centauri (= Alpha Cen C; V645 Cen) is the nearest known star to the Sun. This M5 V flare star is the faintest member of the Alpha Cen triple star system (or moving group) and lies about 1400 AU nearer to the Earth than its brighter G2 V and K2 V companions. Because of its proximity and its membership in the triple system, Proxima has well determined physical properties that includes an age of 5-6 Gyr. In spite of its old age, Proxima is a chromospherically active star with strong Mg II h+k (280nm) emission as well as being a flare star. This star is of great importance to magnetic dynamo theory because it is expected to have a fully convective envelope. One quantity, not well determined yet vital to understanding Proxima's magnetic behavior, is its rotation period. During May-August 1995, Proxima was observed about twice a week with the IUE Satellite. Low resolution LWP (200-320nm) spectra were obtained chiefly to observe the chromospheric Mg II emission and use it to measure Proxima's rotation period as active plage regions on the star's surface rotate in and out of view. The IUE data have been analyzed and the Mg II emission shows 20-25% variations with a period of 31.5+/-1.5 days. This period is assumed to be the star's rotation period. In addition, several flare events were observed and evidence was found for rather fast changes (on a time-scale of weeks) in the plage activity and distribution. Also, comparison of the 1995 data with earlier IUE archival data shows that Proxima probably has an activity cycle and that during 1995 it was near a minimum of activity. Nonetheless, 4 flares were detected. We will present the results of the IUE study and also compare the rotation determination with previous attempts such as that of Benedict et al. (1994). This study is supported from NASA grant NAG 5-2160 and NSF grant AST-9315365, which we gratefully acknowledge.

  8. Acceleration of electrons during the flash phase of solar flares

    NASA Technical Reports Server (NTRS)

    Kane, S. R.

    1974-01-01

    The characteristics of the electron acceleration process operating during the flash phase of solar flares are deduced from the high time resolution observations of impulsive solar X rays greater than or equal to 10 keV and other flash phase emissions from small solar flares, and the implications of these findings are discussed.

  9. 46 CFR 117.68 - Distress flares and smoke signals.

    Code of Federal Regulations, 2013 CFR

    2013-10-01

    ... 46 Shipping 4 2013-10-01 2013-10-01 false Distress flares and smoke signals. 117.68 Section 117.68... AND ARRANGEMENTS Emergency Communications § 117.68 Distress flares and smoke signals. (a) Oceans... hand orange smoke distress signals approved in accordance with § 160.037 in subchapter Q of...

  10. 46 CFR 180.68 - Distress flares and smoke signals.

    Code of Federal Regulations, 2011 CFR

    2011-10-01

    ... 46 Shipping 7 2011-10-01 2011-10-01 false Distress flares and smoke signals. 180.68 Section 180.68... TONS) LIFESAVING EQUIPMENT AND ARRANGEMENTS Emergency Communications § 180.68 Distress flares and smoke... Commandant; and (2) Six hand orange smoke distress signals approved in accordance with § 160.037...

  11. 46 CFR 117.68 - Distress flares and smoke signals.

    Code of Federal Regulations, 2010 CFR

    2010-10-01

    ... 46 Shipping 4 2010-10-01 2010-10-01 false Distress flares and smoke signals. 117.68 Section 117.68... AND ARRANGEMENTS Emergency Communications § 117.68 Distress flares and smoke signals. (a) Oceans... hand orange smoke distress signals approved in accordance with § 160.037 in subchapter Q of...

  12. 46 CFR 180.68 - Distress flares and smoke signals.

    Code of Federal Regulations, 2012 CFR

    2012-10-01

    ... 46 Shipping 7 2012-10-01 2012-10-01 false Distress flares and smoke signals. 180.68 Section 180.68... TONS) LIFESAVING EQUIPMENT AND ARRANGEMENTS Emergency Communications § 180.68 Distress flares and smoke... Commandant; and (2) Six hand orange smoke distress signals approved in accordance with § 160.037...

  13. A common stochastic process in solar and stellar flares

    NASA Astrophysics Data System (ADS)

    Li, Chuan; Fang, Cheng

    2015-08-01

    Solar flares, with energies of 1027 - 1032 ergs, are believed to be powered by sudden release of magnetic energy stored in the corona. Stellar flares, observationally 102 - 106 more intense than solar flares, are generally assumed to release energy through the same underlying mechanism: magnetic reconnection. It is thus expected similar statistical properties between two groups of flares. The selected candidates are 23400 solar flares observed over one solar cycle by GOES spacecraft and 3140 stellar flares from Kepler data adapted from the catalog of Balona (MNRAS, 447, 2714, 2015). We examine the flare frequency as a function of duration, energy, and waiting time. The distributions of flare duration and energy can be well understood in the context of the avalanche model of a self-organized criticality (SOC) system (Aschwanden, A&A, 539, 2, 2012). The waiting time distribution of the SOC system can be explained by a non-stationary Poisson process (Li et al. ApJ Letters, 792, 26, 2014).

  14. Searching for Missing Pieces for Solar Flare Forecasting

    NASA Astrophysics Data System (ADS)

    Leka, K. D.

    2015-12-01

    Knowledge of the state of the solar photospheric magnetic field at a single instant in time does not appear sufficient to uniquely predict the size and timing of impending solar flares. Such knowledge may provide necessary conditions, such as estimates of the magnetic energy needed for a flare to occur. Given the necessary conditions, it is often assumed that the evolution of the field, possibly by only a small amount, may trigger the onset of a flare. We present the results of a study using time series of photospheric vector field data from the Helioseismic and Magnetic Imager (HMI) on NASA's Solar Dynamics Observatory (SDO) to quantitatively parameterize both the state and evolution of solar active regions - their complexity, magnetic topology and energy - as related to solar flare events. We examine both extensive and intensive parameters and their short-term temporal behavior, in the context of predicting flares at various thresholds. Statistical tests based on nonparametric Discriminant Analysis are used to compare pre-flare epochs to a control group of flare-quiet epochs and active regions. Results regarding the type of photospheric signature examined and the efficacy of using the present state vs. temporal evolution to predict solar flares is quantified by standard skill scores. This work is made possible by contracts NASA NNH12CG10C and NOAA/SBIR WC-133R-13-CN-0079.

  15. The Conundrum of the Solar Pre-Flare Photospheric State.

    NASA Astrophysics Data System (ADS)

    Leka, KD; Barnes, Graham; Wagner, Eric

    2015-08-01

    Knowledge of the state of the solar photospheric magnetic field at a single instant in time does not appear sufficient to predict the size and timing of impending solar flares. Such knowledge may provide necessary conditions, such as the free magnetic energy needed for a flare to occur. Given the necessary conditions, it is often assumed that the evolution of the field, possibly by only a small amount, may trigger the onset of a flare. We present the results of a study using time series of photospheric vector field data from the Helioseismic and Magnetic Imager (HMI) on NASA's Solar Dynamics Observatory (SDO) to quantitatively parameterize both the state and evolution of solar active regions - their complexity, magnetic topology and energy - as related to solar flare events. We examine both extensive and intensive parameters and their temporal behavior, in the context of both large and small flaring episodes. Statistical tests based on nonparametric Discriminant Analysis are used to compare pre-flare epochs to a control group of flare-quiet epochs and active regions. Results regarding the type of photospheric signature examined and the efficacy of using the present state vs. temporal evolution to predict solar flares is quantified by standard skill scores.This work is made possible by contracts NASA NNH12CG10C and NOAA/SBIR WC-133R-13-CN-0079.

  16. STATISTICAL ANALYSES ON THERMAL ASPECTS OF SOLAR FLARES

    SciTech Connect

    Li, Y. P.; Gan, W. Q.; Feng, L.

    2012-03-10

    The frequency distribution of flare energies provides a crucial diagnostic to calculate the overall energy residing in flares and to estimate the role of flares in coronal heating. It often takes a power law as its functional form. We have analyzed various variables, including the thermal energies E{sub th} of 1843 flares at their peak time. They were recorded by both Geostationary Operational Environmental Satellites and Reuven Ramaty High-Energy Solar Spectroscopic Imager during the time period from 2002 to 2009 and are classified as flares greater than C 1.0. The relationship between different flare parameters is investigated. It is found that fitting the frequency distribution of E{sub th} to a power law results in an index of -2.38. We also investigate the corrected thermal energy E{sub cth}, which represents the flare total thermal energy including the energy loss in the rising phase. Its corresponding power-law slope is -2.35. Compilation of the frequency distributions of the thermal energies from nanoflares, microflares, and flares in the present work and from other authors shows that power-law indices below -2.0 have covered the range from 10{sup 24} to 10{sup 32} erg. Whether this frequency distribution can provide sufficient energy to coronal heatings in active regions and the quiet Sun is discussed.

  17. The predicted giant flare of Cyg X-3 occurs

    NASA Astrophysics Data System (ADS)

    Trushkin, S. A.; Nizhelskij, N. A.; Tsybulev, P. G.; Zhekanis, G. V.

    2016-09-01

    Three weeks ago we predicted (ATel #9416) that Cyg X-3 entered in the ''ultra-soft'' X-ray state and a giant flare are very probable. Later Cyg X-3 has indeed shown the relatively bright flare (ATel #9444), maximal fluxes were lower 700 mJy at 4-22 GHz and then the microquasar had again quenched.

  18. Large X-class Flare Erupting on Jan. 27

    NASA Video Gallery

    On Jan. 27, 2012 a large X-class flare erupted from an active region near the solar west limb. Seen here is a time series of the flare captured by the X-ray telescope on Hinode. These images repres...

  19. 6. View, flare and oxygen burner pad near southwest side ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    6. View, flare and oxygen burner pad near southwest side of Components Test Laboratory (T-27), looking northeast. Uphill and to the left of the flare is the Oxidizer Conditioning Structure (T-28D) and the Long-Term Oxidizer Silo (T-28B). - Air Force Plant PJKS, Systems Integration Laboratory, Waterton Canyon Road & Colorado Highway 121, Lakewood, Jefferson County, CO

  20. Hα LINE PROFILE ASYMMETRIES AND THE CHROMOSPHERIC FLARE VELOCITY FIELD

    SciTech Connect

    Kuridze, D.; Mathioudakis, M.; Kennedy, M.; Keenan, F. P.; Simões, P. J. A.; Voort, L. Rouppe van der; Fletcher, L.; Carlsson, M.; Jafarzadeh, S.; Allred, J. C.; Kowalski, A. F.; Graham, D.

    2015-11-10

    The asymmetries observed in the line profiles of solar flares can provide important diagnostics of the properties and dynamics of the flaring atmosphere. In this paper the evolution of the Hα and Ca ii λ8542 lines are studied using high spatial, temporal, and spectral resolution ground-based observations of an M1.1 flare obtained with the Swedish 1 m Solar Telescope. The temporal evolution of the Hα line profiles from the flare kernel shows excess emission in the red wing (red asymmetry) before flare maximum and excess in the blue wing (blue asymmetry) after maximum. However, the Ca ii λ8542 line does not follow the same pattern, showing only a weak red asymmetry during the flare. RADYN simulations are used to synthesize spectral line profiles for the flaring atmosphere, and good agreement is found with the observations. We show that the red asymmetry observed in Hα is not necessarily associated with plasma downflows, and the blue asymmetry may not be related to plasma upflows. Indeed, we conclude that the steep velocity gradients in the flaring chromosphere modify the wavelength of the central reversal in the Hα line profile. The shift in the wavelength of maximum opacity to shorter and longer wavelengths generates the red and blue asymmetries, respectively.

  1. Multi-wavelength flare study and magnetic configuration

    NASA Astrophysics Data System (ADS)

    Schmieder, Brigitte; Berlicki, A.; Vilmer, N.; Aulanier, G.; Démoulin, P.; Mein, P.; Mandrini, C.; Deluca, E.

    Recent results of two observation campaigns (October 2002 and October 2003) are presented with the objective of understanding the onset of flares and CMEs. The magnetic field was observed with THEMIS and MDI, the chromosphere with the MSDP operating on the German telescope VTT and on THEMIS, the EUV images with SOHO/CDS and TRACE, the X-ray with RHESSI. We show how important is the magnetic configuration of the active region to produce CMEs using two examples: the October 28 2003 X 17 flare and the October 22 2002 M 1.1 flare. The X 17 flare gave a halo CME while the M 1.1 flare has no corresponding CME. The magnetic topology analysis of the active regions is processed with a linear-force-free field configuration.

  2. Flare asymmetry as seen in offband H-alpha filtergrams

    NASA Technical Reports Server (NTRS)

    Tang, F.

    1983-01-01

    Narrow-band H-alpha filtergrams at + or - 1 A and + or - 2 A from the line center were used to study the asymmetry of flares. Of the 60 flares studied, 92% show red asymmetry while 5% show blue asymmetry. Typically, the filtergrams show a striking dominance of the red wing over the blue wing from onset until late in the decay phase. The difference in intensity of the flare emissions is further augmented by the extensiveness of the emission area in the brighter wing. New kernel-like emissions were often found many minutes after the flare maximum. Spatially, they are displaced from the previous kernels. The late emissions show the same asymmetry as that of the earlier part of the flare.

  3. EVIDENCE FOR HOT FAST FLOW ABOVE A SOLAR FLARE ARCADE

    SciTech Connect

    Imada, S.; Aoki, K.; Hara, H.; Watanabe, T.; Harra, L. K.; Shimizu, T.

    2013-10-10

    Solar flares are one of the main forces behind space weather events. However, the mechanism that drives such energetic phenomena is not fully understood. The standard eruptive flare model predicts that magnetic reconnection occurs high in the corona where hot fast flows are created. Some imaging or spectroscopic observations have indicated the presence of these hot fast flows, but there have been no spectroscopic scanning observations to date to measure the two-dimensional structure quantitatively. We analyzed a flare that occurred on the west solar limb on 2012 January 27 observed by the Hinode EUV Imaging Spectrometer (EIS) and found that the hot (∼30MK) fast (>500 km s{sup –1}) component was located above the flare loop. This is consistent with magnetic reconnection taking place above the flare loop.

  4. A BLAZAR-LIKE RADIO FLARE IN MRK 231

    SciTech Connect

    Reynolds, Cormac; Hurley-Walker, Natasha; Punsly, Brian; O'Dea, Christopher P. E-mail: brian.punsly@comdev-usa.com

    2013-10-20

    Radio monitoring of the broad absorption line quasar (BALQSO) Mrk 231 from 13.9 GHz to 17.6 GHz detected a strong flat spectrum flare. Even though BALQSOs are typically weak radio sources, the 17.6 GHz flux density doubled in ≈150 days, from ≈135 mJy to ≈270 mJy. It is demonstrated that the elapsed rise time in the quasar rest frame and the relative magnitude of the flare is typical of some of the stronger flares in blazars that are usually associated with the ejection of discrete components on parsec scales. The decay of a similar flare was found in a previous monitoring campaign at 22 GHz. We conclude that these flares are not rare. The implication is that Mrk 231 seems to be a quasar in which the physical mechanism that produces the broad absorption line wind is in tension with the emergence of a fledgling blazar.

  5. Solar Flares and the High Energy Solar Spectroscopic Imager (HESSI)

    NASA Technical Reports Server (NTRS)

    Holman, Gordon D.; Fisher, Richard R. (Technical Monitor)

    2001-01-01

    Solar flares are the biggest explosions in the solar system. They are important both for understanding explosive events in the Universe and for their impact on human technology and communications. The satellite-based HESSI is designed to study the explosive release of energy and the acceleration of electrons, protons, and other charged particles to high energies in solar flares. HESSI produces "color" movies of the Sun in high-energy X rays and gamma rays radiated by these energetic particles. HESSI's X-ray and gamma-ray images of flares are obtained using techniques similar to those used in radio interferometry. Ground-based radio observations of the Sun provide an important complement to the HESSI observations of solar flares. I will describe the HESSI Project and the high-energy aspects of solar flares, and how these relate to radio astronomy techniques and observations.

  6. COMPLEX FLARE DYNAMICS INITIATED BY A FILAMENT–FILAMENT INTERACTION

    SciTech Connect

    Zhu, Chunming; McAteer, R. T. James; Liu, Rui; Alexander, David; Sun, Xudong

    2015-11-01

    We report on an eruption involving a relatively rare filament–filament interaction on 2013 June 21, observed by SDO and STEREO-B. The two filaments were separated in height with a “double-decker” configuration. The eruption of the lower filament began simultaneously with a descent of the upper filament, resulting in a convergence and direct interaction of the two filaments. The interaction was accompanied by the heating of surrounding plasma and an apparent crossing of a loop-like structure through the upper filament. The subsequent coalescence of the filaments drove a bright front ahead of the erupting structures. The whole process was associated with a C3.0 flare followed immediately by an M2.9 flare. Shrinking loops and descending dark voids were observed during the M2.9 flare at different locations above a C-shaped flare arcade as part of the energy release, giving us unique insight into the flare dynamics.

  7. A COLD, TENUOUS SOLAR FLARE: ACCELERATION WITHOUT HEATING

    SciTech Connect

    Fleishman, Gregory D.; Nita, Gelu M.; Gary, Dale E.; Kontar, Eduard P.

    2011-04-10

    We report the observation of an unusual cold, tenuous solar flare, which reveals itself via numerous and prominent non-thermal manifestations, while lacking any noticeable thermal emission signature. RHESSI hard X-rays and 0.1-18 GHz radio data from OVSA and Phoenix-2 show copious electron acceleration (10{sup 35} electrons s{sup -1} above 10 keV) typical for GOES M-class flares with electrons energies up to 100 keV, but GOES temperatures not exceeding 6.1 MK. The imaging, temporal, and spectral characteristics of the flare have led us to a firm conclusion that the bulk of the microwave continuum emission from this flare was produced directly in the acceleration region. The implications of this finding for the flaring energy release and particle acceleration are discussed.

  8. IMPULSIVE PHASE CORONAL HARD X-RAY SOURCES IN AN X3.9 CLASS SOLAR FLARE

    SciTech Connect

    Chen Qingrong; Petrosian, Vahe E-mail: vahep@stanford.edu

    2012-03-20

    We present the analysis of a pair of unusually energetic coronal hard X-ray (HXR) sources detected by the Reuven Ramaty High Energy Solar Spectroscopic Imager during the impulsive phase of an X3.9 class solar flare on 2003 November 3, which simultaneously shows two intense footpoint (FP) sources. A distinct loop top (LT) coronal source is detected up to {approx}150 keV and a second (upper) coronal source up to {approx}80 keV. These photon energies, which were not fully investigated in earlier analysis of this flare, are much higher than commonly observed in coronal sources and pose grave modeling challenges. The LT source in general appears higher in altitude with increasing energy and exhibits a more limited motion compared to the expansion of the thermal loop. The high-energy LT source shows an impulsive time profile and its nonthermal power-law spectrum exhibits soft-hard-soft evolution during the impulsive phase, similar to the FP sources. The upper coronal source exhibits an opposite spatial gradient and a similar spectral slope compared to the LT source. These properties are consistent with the model of stochastic acceleration of electrons by plasma waves or turbulence. However, the LT and FP spectral index difference (varying from {approx}0 to 1) is much smaller than commonly measured and than that expected from a simple stochastic acceleration model. Additional confinement or trapping mechanisms of high-energy electrons in the corona are required. Comprehensive modeling including both kinetic effects and the macroscopic flare structure may shed light on this behavior. These results highlight the importance of imaging spectroscopic observations of the LT and FP sources up to high energies in understanding electron acceleration in solar flares. Finally, we show that the electrons producing the upper coronal HXR source may very likely be responsible for the type III radio bursts at the decimetric/metric wavelength observed during the impulsive phase of this

  9. A statistic study of ionospheric solar flare activity indicator

    NASA Astrophysics Data System (ADS)

    Xiong, Bo; Ding, Feng; Ning, Baiqi; Wan, Weixing; Yu, You; Hu, Lianhuan

    According to the Chapman ionization theory, an ionospheric solar flare activity indicator (ISFAI) is given by the solar zenith angle and the variation rate of ionospheric vertical total electron content, which is measured from a global network of dual-frequency GPS receivers. The ISFAI is utilized to statistically analyze the ionospheric responses to 1439 M-class and 126 X-class solar flares during solar cycle 23 (1996-2008). The statistical results show that the occurrence of ISFAI peak increases obviously at 3.2 total electron content unit (TECU)/h (1 TECU = 1016 elm-2) and reaches the maximum at 10 TECU/h during M-class flares and 10 TECU/h and 40 TECU/h for X-class flares. ISFAI is closely correlated with the 26-34 nm extreme ultraviolet flux but poorly related to the 0.1-0.8 nm X-ray flux. The central meridian distance (CMD) of flare location is an important reason for depressing relationship between ISFAI and X-ray Flux. Through the CMD effect modification, the ISFAI has a significant dependence on the X-ray flux with a correlation coefficient of 0.76. The ISFAI sensitivity enables to detect the extreme X-class flares, as well as the variations of one order of magnitude or even smaller (such as for C-class flares). Meanwhile, ISFAI is helpful to the calibration of the X-ray flux at 0.1-0.8 nm observed by GOES during some flares. In addition, statistical results demonstrate that ISFAI can detect 80% of all M-class flares and 92% for all X-class ones during 1996-2008. Owing to the high sensitivity and temporal resolution, ISFAI can be utilized as a solar flare detection parameter to monitor space weather.

  10. Large solar flares and their ionospheric D region enhancements

    NASA Astrophysics Data System (ADS)

    Thomson, Neil R.; Rodger, Craig J.; Clilverd, Mark A.

    2005-06-01

    On 4 November 2003, the largest solar flare ever recorded saturated the GOES satellite X-ray detectors, making an assessment of its size difficult. However, VLF radio phase advances effectively recorded the lowering of the VLF reflection height and hence the lowest edge of the Earth's ionosphere. Previously, these phase advances were used to extrapolate the GOES 0.1-0.8 nm ("XL") fluxes from saturation at X17 to give a peak magnitude of X45 ± 5 for this great flare. Here it is shown that a similar extrapolation, but using the other GOES X-ray band, 0.05-0.4 nm ("XS"), is also consistent with a magnitude of X45. Also reported here are VLF phase measurements from two paths near dawn: "Omega Australia" to Dunedin, New Zealand (only just all sunlit) and NPM, Hawaii, to Ny Alesund, Svalbard (only partly sunlit), which also give remarkably good extrapolations of the flare flux, suggesting that VLF paths monitoring flares do not necessarily need to be in full daylight. D region electron densities are modeled as functions of X-ray flux up to the level of the great X45 flare by using flare-induced VLF amplitudes together with the VLF phase changes. During this great flare, the "Wait" reflection height, H', was found to have been lowered to ˜53 km or ˜17 km below the normal midday value of ˜70 km. Finally, XL/XS ratios are examined during some large flares, including the great flare. Plots of such ratios against XL can give quite good estimates of the great flare's size (X45) but without use of VLF measurements.

  11. ABRUPT LONGITUDINAL MAGNETIC FIELD CHANGES IN FLARING ACTIVE REGIONS

    SciTech Connect

    Petrie, G. J. D.; Sudol, J. J.

    2010-12-01

    We characterize the changes in the longitudinal photospheric magnetic field during 38 X-class and 39 M-class flares within 65{sup 0} of disk center using 1 minute GONG magnetograms. In all 77 cases, we identify at least one site in the flaring active region where clear, permanent, stepwise field changes occurred. The median duration of the field changes was about 15 minutes and was approximately equal for X-class and for M-class flares. The absolute values of the field changes ranged from the detection limit of {approx}10 G to as high as {approx}450 G in two exceptional cases. The median value was 69 G. Field changes were significantly stronger for X-class than for M-class flares and for limb flares than for disk-center flares. Longitudinal field changes less than 100 G tended to decrease longitudinal field strengths, both close to disk center and close to the limb, while field changes greater than 100 G showed no such pattern. Likewise, longitudinal flux strengths tended to decrease during flares. Flux changes, particularly net flux changes near disk center, correlated better than local field changes with GOES peak X-ray flux. The strongest longitudinal field and flux changes occurred in flares observed close to the limb. We estimate the change of Lorentz force associated with each flare and find that this is large enough in some cases to power seismic waves. We find that longitudinal field decreases would likely outnumber increases at all parts of the solar disk within 65{sup 0} of disk center, as in our observations, if photospheric field tilts increase during flares as predicted by Hudson et al.

  12. Stochastic particle acceleration in solar flares

    NASA Technical Reports Server (NTRS)

    Droege, W.; Schlickeiser, R.

    1985-01-01

    It is proposed that particles during the second phase of solar flares are accelerated by stochastic resonant scattering off hydromagnetic waves and first order Fermi acceleration in shock waves generated in the impulsive phase of the flare. Solutions allow arbitrary power law momentum dependences of the momentum diffusion coefficient as well as the momentum diffusion coefficient as well as the momentum loss time. The acceleration time scale to a characteristic energy approximately 100 keV for protons can be as short as 5s. The resulting electron spectra show a characteristic double power law with a transition around 200 keV and are correlated to the proton spectra evaluated under equal boundary conditions, indicating that electrons and protons are accelerated by the same mechanism. The correlation between the different spectral indices in the electron double power law and between electron and proton spectra are governed by the ratio of first to second order acceleration and therefore allow a determination of the Alfven Mach number of the shock wave.

  13. Space observations of comets during solar flares

    NASA Astrophysics Data System (ADS)

    Ibadov, Subhon; Ibodov, Firuz S.

    Problems connected with mechanisms for comet outbursts as well as for gamma-ray bursts remain open. Meantime, calculations show that an irradiation of a certain class of cometary nuclei, having high specific electric resistance, by intense fluxes of energetic protons and posi-tively charged ions with kinetic energies more than 1 MeV/nucleon, ejected from the Sun during strong solar flares, can produce a macroscopic high-voltage electric double layer with positive charge in the subsurface region of the nucleus, during irradiation time of the order of 10-100 hours at heliocentric distances around 1-10 AU. The maximum electric energy accumulated in such layer will be restricted by discharge potential of the layer material. For the comet nuclei with the typical radius of the order of 1-10 km the accumulated energy of such natural electric capacitor is comparable to the energy of large comet outbursts that are estimated on the basis of ground-based optical observations of comets. The impulse X-ray radiation anticipated from the high-voltage electric discharge of the capacitor may serve as an indicator of realization of the processes above considered. Therefore, space observations of comets and pseudo-asteroids of cometary origin, having brightness correlation with solar activity, using space X-ray obser-vatories during strong solar flares are very interesting for the physics of comets as well as for high energy astrophysics.

  14. Reverse-current effect in present-day models of solar flares: Theory and high-accuracy observations

    NASA Astrophysics Data System (ADS)

    Gritsyk, P. A.; Somov, B. V.

    2014-08-01

    We propose an accurate analytical model for the source of hard X-ray emission from a flare in the form of a "thick target" with a reverse current to explain the results of present-day observations of solar flares onboard the GOES, Hinode, RHESSI, and TRACE satellites. The model, one-dimensional in coordinate space and two-dimensional in velocity space, self-consistently takes into account the fact that the beam electrons lose the kinetic energy of their motion along the magnetic field almost without any collisions under the action of the reverse-current electric field. Some of the electrons return from the emission source to the acceleration region without losing the kinetic energy of their transverse motion. Based on the observed hard X-ray bremsstrahlung spectrum, the model allows the injection spectrum of accelerated electrons to be reconstructed with a high accuracy. As an example, we consider the white-light flare of December 6, 2006, which was observed with a high spatial resolution in the optical wavelength range at the main maximum of hard X-ray emission. Within the framework of our model, we show that to explain the hard X-ray spectrum, the flux density of the energy transferred by electrons with energies above 18 keV was ˜3 × 1013 erg cm-2 s-1. This exceeds the habitual values typical of the classical model of a thick target without a reverse current by two orders of magnitude. The electron density in the beam is also very high: ˜1011 cm-3. A more careful consideration of plasma processes in such dense electron beams is needed when the physical parameters of a flare are calculated.

  15. THE NATURE OF FLARE RIBBONS IN CORONAL NULL-POINT TOPOLOGY

    SciTech Connect

    Masson, S.; Aulanier, G.; Pariat, E.; Schrijver, C. J.

    2009-07-20

    Flare ribbons are commonly attributed to the low-altitude impact, along the footprints of separatrices or quasi-separatrix layers (QSLs), of particle beams accelerated through magnetic reconnection. If reconnection occurs at a three-dimensional coronal magnetic null point, the footprint of the dome-shaped fan surface would map a closed circular ribbon. This paper addresses the following issues: does the entire circular ribbon brighten simultaneously, as expected because all fan field lines pass through the null point? And since the spine separatrices are singular field lines, do spine-related ribbons look like compact kernels? What can we learn from these observations about current sheet formation and magnetic reconnection in a null-point topology? The present study addresses these questions by analyzing Transition Region and Coronal Explorer and Solar and Heliospheric Observatory/Michelson Doppler Imager observations of a confined flare presenting a circular ribbon. Using a potential field extrapolation, we linked the circular shape of the ribbon with the photospheric mapping of the fan field lines originating from a coronal null point. Observations show that the flare ribbon outlining the fan lines brightens sequentially along the counterclockwise direction and that the spine-related ribbons are elongated. Using the potential field extrapolation as initial condition, we conduct a low-{beta} resistive magnetohydrodynamics simulation of this observed event. We drive the coronal evolution by line-tied diverging boundary motions, so as to emulate the observed photospheric flow pattern associated with some magnetic flux emergence. The numerical analysis allows us to explain several observed features of the confined flare. The vorticity induced in the fan by the prescribed motions causes the spines to tear apart along the fan. This leads to formation of a thin current sheet and induces null-point reconnection. We also find that the null point and its associated

  16. Particle kinematics in solar flares: observations and theory

    NASA Astrophysics Data System (ADS)

    Battaglia, Marina

    2008-12-01

    This thesis is devoted to the study of particle acceleration and propagation processes in solar flares. Solar flares are amongst the most powerful and energetic activity phenomena our Sun exhibits. They release energy of the order of 10(32) erg in seconds to minutes. In the process, electrons and protons are accelerated to relativistic energies, making flares very efficient particle accelerators. The most compelling observational signatures of flares can be found in X-rays and extreme ultra-violet wavelengths. Due to atmospheric absorption, those wavelengths can only be studied from space. Since the beginning of the space age, countless flares have been observed by satellites. The present work is largely based on observations by the Ramaty High Energy Solar Spectroscopic Imager (RHESSI), an X-ray satellite which has been observing the Sun since February 2002. It is a NASA mission with substantial Swiss hardware and software contribution. Using RHESSI observations of flares of different intensity, a deeper understanding of the particle transport and energy transport processes in flare loops, as well as the acceleration site and acceleration mechanism is sought. The time evolution of images and spectra is studied along with the quantitative relations between X-ray sources observed in the corona (coronal sources) and from the chromosphere (footpoints). The spectral relations found between coronal sources and footpoints are compared to the so-called ``intermediate thin-thick target model'', which was based on observations by the satellite Yohkoh. We show that the spectral relations between coronal sources and footpoints observed with RHESSI cannot be explained by the intermediate thin-thick target model. In a next step, return currents in the flare loop were considered. With this extension to the existing model, the spectra of the coronal source and the footpoints, as well as the relations between them can be explained, indicating the importance of return currents in

  17. Solar and Stellar Flares and Their Effects on Planets

    NASA Astrophysics Data System (ADS)

    Shibata, Kazunari

    2015-08-01

    Recent space observations of the Sun revealed that the solar atmosphere is full of explosions, such as flares and flare-like phenomena. These flares generate not only strong electromagnetic emissions but also nonthermal particles and bulk plasma ejections, which sometimes lead to geomagnetic storms and affect terrestrial environment and our civilization, damaging satellite, power-grids, radio communication etc. Solar flares are prototype of various explosions in our universe, and hence are important not only for geophysics and environmental science but also for astrophysics. The energy source of solar flares is now established to be magnetic energy stored near sunspots. There is now increasing observational evidence that solar flares are caused by magnetic reconnection, merging of anti-parallel magnetic field lines and associated magneto-plasma dynamics (Shibata and Magara 2011, Living Review). It has also been known that many stars show flares similar to solar flares, and often such stellar flares are much more energetic than solar flares. The total energy of a solar flare is typically 10^29 - 10^32 erg. On the other hand, there are much more energetic flares (10^33 - 10^38 erg) in stars, especially in young stars. These are called superflares. We argue that these superflares on stars can also be understood in a unified way based on the reconnection mechanism. Finally we show evidence of occurrence of superflares on Sun-like stars according to recent stellar observations (Maehara et al. 2012, Nature, Shibayama et al. 2013), which revealed that superflares with energy of 10^34 - 10^35 erg (100 - 1000 times of the largest solar flares) occur with frequency of once in 800 - 5000 years on Sun-like stars which are very similar to our Sun. Against the previous belief, these new observations as well as theory (Shibata et al. 2013) suggest that we cannot deny the possibility of superflares on the present Sun. Finally, we shall discuss possible impacts of these superflares

  18. Auditory motion affects visual biological motion processing.

    PubMed

    Brooks, A; van der Zwan, R; Billard, A; Petreska, B; Clarke, S; Blanke, O

    2007-02-01

    The processing of biological motion is a critical, everyday task performed with remarkable efficiency by human sensory systems. Interest in this ability has focused to a large extent on biological motion processing in the visual modality (see, for example, Cutting, J. E., Moore, C., & Morrison, R. (1988). Masking the motions of human gait. Perception and Psychophysics, 44(4), 339-347). In naturalistic settings, however, it is often the case that biological motion is defined by input to more than one sensory modality. For this reason, here in a series of experiments we investigate behavioural correlates of multisensory, in particular audiovisual, integration in the processing of biological motion cues. More specifically, using a new psychophysical paradigm we investigate the effect of suprathreshold auditory motion on perceptions of visually defined biological motion. Unlike data from previous studies investigating audiovisual integration in linear motion processing [Meyer, G. F. & Wuerger, S. M. (2001). Cross-modal integration of auditory and visual motion signals. Neuroreport, 12(11), 2557-2560; Wuerger, S. M., Hofbauer, M., & Meyer, G. F. (2003). The integration of auditory and motion signals at threshold. Perception and Psychophysics, 65(8), 1188-1196; Alais, D. & Burr, D. (2004). No direction-specific bimodal facilitation for audiovisual motion detection. Cognitive Brain Research, 19, 185-194], we report the existence of direction-selective effects: relative to control (stationary) auditory conditions, auditory motion in the same direction as the visually defined biological motion target increased its detectability, whereas auditory motion in the opposite direction had the inverse effect. Our data suggest these effects do not arise through general shifts in visuo-spatial attention, but instead are a consequence of motion-sensitive, direction-tuned integration mechanisms that are, if not unique to biological visual motion, at least not common to all types of

  19. Size Distributions of Solar Flares and Solar Energetic Particle Events

    NASA Technical Reports Server (NTRS)

    Cliver, E. W.; Ling, A. G.; Belov, A.; Yashiro, S.

    2012-01-01

    We suggest that the flatter size distribution of solar energetic proton (SEP) events relative to that of flare soft X-ray (SXR) events is primarily due to the fact that SEP flares are an energetic subset of all flares. Flares associated with gradual SEP events are characteristically accompanied by fast (much > 1000 km/s) coronal mass ejections (CMEs) that drive coronal/interplanetary shock waves. For the 1996-2005 interval, the slopes (alpha values) of power-law size distributions of the peak 1-8 Angs fluxes of SXR flares associated with (a) >10 MeV SEP events (with peak fluxes much > 1 pr/sq cm/s/sr) and (b) fast CMEs were approx 1.3-1.4 compared to approx 1.2 for the peak proton fluxes of >10 MeV SEP events and approx 2 for the peak 1-8 Angs fluxes of all SXR flares. The difference of approx 0.15 between the slopes of the distributions of SEP events and SEP SXR flares is consistent with the observed variation of SEP event peak flux with SXR peak flux.

  20. Gas Flaring Volume Estimates with Multiple Satellite Observations

    NASA Astrophysics Data System (ADS)

    Ziskin, D. C.; Elvidge, C.; Baugh, K.; Ghosh, T.; Hsu, F. C.

    2010-12-01

    Flammable gases (primarily methane) are a common bi-product associated with oil wells. Where there is no infrastructure to use the gas or bring it to market, the gases are typically flared off. This practice is more common at remote sites, such as an offshore drilling platform. The Defense Meteorological Satellite Program (DMSP) is a series of satellites with a low-light imager called the Operational Linescan System (OLS). The OLS, which detects the flares at night, has been a valuable tool in the estimation of flared gas volume [Elvidge et al, 2009]. The use of the Moderate Resolution Imaging Spectroradiometer (MODIS) fire product has been processed to create products suitable for an independent estimate of gas flaring on land. We are presenting the MODIS flare product, the results of our MODIS gas flare volume analysis, and independent validation of the published DMSP estimates. Elvidge, C. D., Ziskin, D., Baugh, K. E., Tuttle, B. T., Ghosh, T., Pack, D. W., Erwin, E. H., Zhizhin, M., 2009, "A Fifteen Year Record of Global Natural Gas Flaring Derived from Satellite Data", Energies, 2 (3), 595-622

  1. OBSERVATIONS OF THERMAL FLARE PLASMA WITH THE EUV VARIABILITY EXPERIMENT

    SciTech Connect

    Warren, Harry P.; Doschek, George A.; Mariska, John T.

    2013-06-20

    One of the defining characteristics of a solar flare is the impulsive formation of very high temperature plasma. The properties of the thermal emission are not well understood, however, and the analysis of solar flare observations is often predicated on the assumption that the flare plasma is isothermal. The EUV Variability Experiment (EVE) on the Solar Dynamics Observatory provides spectrally resolved observations of emission lines that span a wide range of temperatures (e.g., Fe XV-Fe XXIV) and allow for thermal flare plasma to be studied in detail. In this paper we describe a method for computing the differential emission measure distribution in a flare using EVE observations and apply it to several representative events. We find that in all phases of the flare the differential emission measure distribution is broad. Comparisons of EVE spectra with calculations based on parameters derived from the Geostationary Operational Environmental Satellites soft X-ray fluxes indicate that the isothermal approximation is generally a poor representation of the thermal structure of a flare.

  2. CONSTRAINING SOLAR FLARE DIFFERENTIAL EMISSION MEASURES WITH EVE AND RHESSI

    SciTech Connect

    Caspi, Amir; McTiernan, James M.; Warren, Harry P.

    2014-06-20

    Deriving a well-constrained differential emission measure (DEM) distribution for solar flares has historically been difficult, primarily because no single instrument is sensitive to the full range of coronal temperatures observed in flares, from ≲2 to ≳50 MK. We present a new technique, combining extreme ultraviolet (EUV) spectra from the EUV Variability Experiment (EVE) onboard the Solar Dynamics Observatory with X-ray spectra from the Reuven Ramaty High Energy Solar Spectroscopic Imager (RHESSI), to derive, for the first time, a self-consistent, well-constrained DEM for jointly observed solar flares. EVE is sensitive to ∼2-25 MK thermal plasma emission, and RHESSI to ≳10 MK; together, the two instruments cover the full range of flare coronal plasma temperatures. We have validated the new technique on artificial test data, and apply it to two X-class flares from solar cycle 24 to determine the flare DEM and its temporal evolution; the constraints on the thermal emission derived from the EVE data also constrain the low energy cutoff of the non-thermal electrons, a crucial parameter for flare energetics. The DEM analysis can also be used to predict the soft X-ray flux in the poorly observed ∼0.4-5 nm range, with important applications for geospace science.

  3. Differential rotation, flares and coronae in A to M stars

    NASA Astrophysics Data System (ADS)

    Balona, L. A.; Švanda, M.; Karlický, M.

    2016-08-01

    Kepler data are used to investigate flares in stars of all spectral types. There is a strong tendency across all spectral types for the most energetic flares to occur among the most rapidly rotating stars. Differential rotation could conceivably play an important role in enhancing flare energies. This idea was investigated, but no correlation could be found between rotational shear and the incidence of flares. Inspection of Kepler light curves shows that rotational modulation is very common over the whole spectral type range. Using the rotational light amplitude, the size distribution of starspots was investigated. Our analysis suggests that stars with detectable flares have spots significantly larger than non-flare stars, indicating that flare energies are correlated with the size of the active region. Further evidence of the existence of spots on A stars is shown by the correlation between the photometric period and the projected rotational velocity. The existence of spots indicates the presence of magnetic fields, but the fact that A stars lack coronae implies that surface convection is a necessary condition for the formation of the corona.

  4. Temperature Dependence of the Flare Fluence Scaling Exponent

    NASA Astrophysics Data System (ADS)

    Kretzschmar, M.

    2015-12-01

    Solar flares result in an increase of the solar irradiance at all wavelengths. While the distribution of the flare fluence observed in coronal emission has been widely studied and found to scale as f(E)˜ E^{-α}, with α slightly below 2, the distribution of the flare fluence in chromospheric lines is poorly known. We used the solar irradiance measurements observed by the SDO/EVE instrument at a 10 s cadence to investigate the dependency of the scaling exponent on the formation region of the lines (or temperature). We analyzed all flares above the C1 level since the start of the EVE observations (May 2010) to determine the flare fluence distribution in 16 lines covering a wide range of temperatures, several of which were not studied before. Our results show a weak downward trend with temperature of the scaling exponent of the PDF that reaches from above 2 at lower temperature (a few 104 K) to {˜ }1.8 for hot coronal emission (several 106 K). However, because colder lines also have fainter contrast, we cannot exclude that this behavior is caused by including more noise for smaller flares for these lines. We discuss the method and its limitations and tentatively associate this possible trend with the different mechanisms responsible for the heating of the chromosphere and corona during flares.

  5. An X-ray flare from 47 Cas

    SciTech Connect

    Pandey, Jeewan C.; Karmakar, Subhajeet

    2015-02-01

    Using XMM-Newton observations, we investigate properties of a flare from the very active but poorly known stellar system 47 Cas. The luminosity at the peak of the flare is found to be 3.54 × 10{sup 30} erg s{sup −1}, which is ∼2 times higher than that at a quiescent state. The quiescent state corona of 47 Cas can be represented by two temperature plasma: 3.7 and 11.0 MK. The time-resolved X-ray spectroscopy of the flare show the variable nature of the temperature, the emission measure, and the abundance. The maximum temperature during the flare is derived as 72.8 MK. We infer the length of a flaring loop to be 3.3 × 10{sup 10} cm using a hydrodynamic loop model. Using the RGS spectra, the density during the flare is estimated as 4.0 × 10{sup 10} cm{sup −3}. The loop scaling laws are also applied when deriving physical parameters of the flaring plasma.

  6. SIZE DISTRIBUTIONS OF SOLAR FLARES AND SOLAR ENERGETIC PARTICLE EVENTS

    SciTech Connect

    Cliver, E. W.; Ling, A. G.; Belov, A.; Yashiro, S.

    2012-09-10

    We suggest that the flatter size distribution of solar energetic proton (SEP) events relative to that of flare soft X-ray (SXR) events is primarily due to the fact that SEP flares are an energetic subset of all flares. Flares associated with gradual SEP events are characteristically accompanied by fast ({>=}1000 km s{sup -1}) coronal mass ejections (CMEs) that drive coronal/interplanetary shock waves. For the 1996-2005 interval, the slopes ({alpha} values) of power-law size distributions of the peak 1-8 A fluxes of SXR flares associated with (a) >10 MeV SEP events (with peak fluxes {>=}1 pr cm{sup -2} s{sup -1} sr{sup -1}) and (b) fast CMEs were {approx}1.3-1.4 compared to {approx}1.2 for the peak proton fluxes of >10 MeV SEP events and {approx}2 for the peak 1-8 A fluxes of all SXR flares. The difference of {approx}0.15 between the slopes of the distributions of SEP events and SEP SXR flares is consistent with the observed variation of SEP event peak flux with SXR peak flux.

  7. RAPID TRANSITION OF UNCOMBED PENUMBRAE TO FACULAE DURING LARGE FLARES

    SciTech Connect

    Wang Haimin; Deng Na; Liu Chang

    2012-04-01

    In the past two decades, the complex nature of sunspots has been disclosed with high-resolution observations. One of the most important findings is the 'uncombed' penumbral structure, where a more horizontal magnetic component carrying most of Evershed flows is embedded in a more vertical magnetic background. The penumbral bright grains are locations of hot upflows and dark fibrils are locations of horizontal flows that are guided by a nearly horizontal magnetic field. On the other hand, it was found that flares may change the topology of sunspots in {delta} configuration: the structure at the flaring polarity inversion line becomes darkened while sections of peripheral penumbrae may disappear quickly and permanently associated with flares. The high spatial and temporal resolution observations obtained with the Hinode/Solar Optical Telescope provide an excellent opportunity to study the evolution of penumbral fine structures associated with major flares. Taking advantage of two near-limb events, we found that in sections of peripheral penumbrae swept by flare ribbons the dark fibrils completely disappear, while the bright grains evolve into faculae that are signatures of vertical magnetic flux tubes. The corresponding magnetic fluxes measured in the decaying penumbrae show stepwise changes temporally correlated with the flares. These observations suggest that the horizontal magnetic field component of the penumbra could be straightened upward (i.e., turning from horizontal to vertical) due to magnetic field restructuring associated with flares, which results in the transition of penumbrae to faculae.

  8. Near-source air quality impacts of large olefin flares.

    PubMed

    Olaguer, Eduardo P

    2012-08-01

    Large petrochemicalflares, common in the Houston Ship Channel (the Ship Channel) and other industrialized areas in the Gulfof Mexico region, emit hundreds to thousands of pounds per hour of highly reactive volatile organic compounds (HRVOCs). We employedfine horizontal resolution (200 mx200 m) in a three-dimensional (3D) Eulerian chemical transport model to simulate two historical Ship Channel flares. The model reasonably reproduced the observed ozone rise at the nearest monitoring stations downwind of the flares. The larger of the two flares had an olefin emission rate exceeding 1400 lb/hr. In this case, the model simulated a rate of increase in peak ozone greater than 40 ppb/hr over a 12 kmx12 km horizontal domain without any unusual meteorological conditions. In this larger flare, formaldehyde emissions typically neglected in official inventories enhanced peak ozone by as much as 16 ppb and contributed over 10 ppb to ambient formaldehyde up to approximately 8 km downwind of the flare. The intense horizontal gradients in large flare plumes cannot be simulated by coarse models typically used to demonstrate ozone attainment. Moreover even the relatively dense monitoring network in the Ship Channel may not be able to detect many transient high ozone events (THOEs) caused by industrial flare emissions in the absence of stagnant air recirculation or stalled sea breeze fronts, even though such conditions are unnecessary for the occurrence of THOEs.

  9. HEATING OF FLARE LOOPS WITH OBSERVATIONALLY CONSTRAINED HEATING FUNCTIONS

    SciTech Connect

    Qiu Jiong; Liu Wenjuan; Longcope, Dana W.

    2012-06-20

    We analyze high-cadence high-resolution observations of a C3.2 flare obtained by AIA/SDO on 2010 August 1. The flare is a long-duration event with soft X-ray and EUV radiation lasting for over 4 hr. Analysis suggests that magnetic reconnection and formation of new loops continue for more than 2 hr. Furthermore, the UV 1600 Angstrom-Sign observations show that each of the individual pixels at the feet of flare loops is brightened instantaneously with a timescale of a few minutes, and decays over a much longer timescale of more than 30 minutes. We use these spatially resolved UV light curves during the rise phase to construct empirical heating functions for individual flare loops, and model heating of coronal plasmas in these loops. The total coronal radiation of these flare loops are compared with soft X-ray and EUV radiation fluxes measured by GOES and AIA. This study presents a method to observationally infer heating functions in numerous flare loops that are formed and heated sequentially by reconnection throughout the flare, and provides a very useful constraint to coronal heating models.

  10. Risk factors of systemic lupus erythematosus flares during pregnancy.

    PubMed

    Jara, Luis J; Medina, Gabriela; Cruz-Dominguez, Pilar; Navarro, Carmen; Vera-Lastra, Olga; Saavedra, Miguel A

    2014-12-01

    This review examines the risk factors for the development of systemic lupus erythematosus (SLE) flares during pregnancy. In preconception, anti-DNA, hypocomplementemia, previous thrombosis, triple antiphospholipid (aPL) antibody positivity, active lupus nephritis and discontinuation of medications such as hydroxychloroquine and azathioprine are factors associated with pregnancy failure. During pregnancy, SLE flares are associated with aPL antibodies, synergic changes of pregnancy on Th1 and TH2 cytokines, other cytokines and chemokines that interact with hormones such as estrogen and prolactin that amplify the inflammatory effect. From the clinical point of view, SLE activity at pregnancy onset, thrombocytopenia, lupus nephritis, arterial hypertension, aPL syndromes, preeclampsia is associated with lupus flares and fetal complications. In puerperium, the risk factors of flares are similar to pregnancy. Hyperactivity of immune system, autoantibodies, hyperprolactinemia, active lupus nephritis, decrease in TH2 cytokines with increase in TH1 cytokines probably participate in SLE flare. The SLE flares during pregnancy make the difference between an uncomplicated pregnancy and pregnancy with maternal and fetal complications. Therefore, the knowledge of risk factors leads the best treatment strategies to reduce flares and fetal complications in SLE patients.

  11. Implications of RHESSI Observations for Solar Flare Models and Energetics

    NASA Technical Reports Server (NTRS)

    Holman, Gordon D.

    2006-01-01

    Observations of solar flares in X-rays and gamma-rays provide the most direct information about the hottest plasma and energetic electrons and ions accelerated in flares. The Ramaty High Energy Solar Spectroscopic Imager (RHESSI) has observed over 18000 solar flares in X-rays and gamma-rays since its launch in February of 2002. RHESSI observes the full Sun at photon energies from as low as 3 keV to as high as 17 MeV with a spectral resolution on the order of 1 keV. It also provides images in arbitrary bands within this energy range with spatial resolution as good as 3 seconds of arc. Full images are typically produced every 4 seconds, although higher time resolution is possible. This unprecedented combination of spatial, spectral, and temporal resolution, spectral range and flexibility has led to fundamental advances in our understanding of flares. I will show RHESSI and coordinated observations that confirm coronal magnetic reconnection models for eruptive flares and coronal mass ejections, but also present new puzzles for these models. I will demonstrate how the analysis of RHESSI spectra has led to a better determination of the energy flux and total energy in accelerated electrons, and of the energy in the hot, thermal flare plasma. I will discuss how these energies compare with each other and with the energy contained in other flare-related phenomena such as interplanetary particles and coronal mass ejections.

  12. Dual frequency observations of flares with the VLA

    NASA Technical Reports Server (NTRS)

    Dulk, G. A.; Bastian, T. S.; Hurford, G. J.

    1983-01-01

    Observations are presented of two subflares near the limb on 21 and 22 November 1981 and an M7.7 flare on 8 May 1981 made at 5 and 15 GHz using the VLA. One of the November flares produced no 5 GHz radiation, while the 15 GHz radiation in the other flare emanated from a source which was smaller, lower, and displaced from the 5 GHz source. The flare occurring on 8 May was intense and complex, and contained two or more sources at both 5 and 15 GHz. Prior to the peak of the flare, the sources were found to grow in size, after which time only weak subsources were visible to the VLA. These subsources were found to be located between or at the edge of the H-alpha ribbons and the two hard X-ray sources imaged by the Hinotori satellite. Highly polarized, bursty radiation was observed at 1 and 2 GHz, which indicated that an electron-cyclotron maser operated during the flare. The maximum field strength in flaring loops is estimated to be 360-600 gauss.

  13. The relationship between energetic particles and flare properties for impulsive solar flares

    SciTech Connect

    Cane, H.V.; Reames, D.V.

    1990-06-01

    The impulsive mode of particle acceleration is studied by searching for 0.2-2 MeV electron increases associated with intense type III/V bursts. It is found that the presence of a type III/V burst in association with a relatively intense flare event indicates the acceleration and escape of greater than 100 KeV electrons. A list of type III/V electron events is compiled, showing that the majority included greater than 10 MeV proton increases, although they were not followed by a type II burst. The results suggest that there are two different modes of proton acceleration with the second mode becoming significant only for larger, gradual flares. 19 refs.

  14. Evolution of flare ribbons, electric currents, and quasi-separatrix layers during an X-class flare

    NASA Astrophysics Data System (ADS)

    Janvier, M.; Savcheva, A.; Pariat, E.; Tassev, S.; Millholland, S.; Bommier, V.; McCauley, P.; McKillop, S.; Dougan, F.

    2016-07-01

    Context. The standard model for eruptive flares has been extended to three dimensions (3D) in the past few years. This model predicts typical J-shaped photospheric footprints of the coronal current layer, forming at similar locations as the quasi-separatrix layers (QSLs). Such a morphology is also found for flare ribbons observed in the extreme ultraviolet (EUV) band, and in nonlinear force-free field (NLFFF) magnetic field extrapolations and models. Aims: We study the evolution of the photospheric traces of the current density and flare ribbons, both obtained with the Solar Dynamics Observatory instruments. We aim to compare their morphology and their time evolution, before and during the flare, with the topological features found in a NLFFF model. Methods: We investigated the photospheric current evolution during the 06 September 2011 X-class flare (SOL2011-09-06T22:20) occurring in NOAA AR 11283 from observational data of the magnetic field obtained with the Helioseismic and Magnetic Imager aboard the Solar Dynamics Observatory. We compared this evolution with that of the flare ribbons observed in the EUV filters of the Atmospheric Imager Assembly. We also compared the observed electric current density and the flare ribbon morphology with that of the QSLs computed from the flux rope insertion method-NLFFF model. Results: The NLFFF model shows the presence of a fan-spine configuration of overlying field lines, due to the presence of a parasitic polarity, embedding an elongated flux rope that appears in the observations as two parts of a filament. The QSL signatures of the fan configuration appear as a circular flare ribbon that encircles the J-shaped ribbons related to the filament ejection. The QSLs, evolved via a magnetofrictional method, also show similar morphology and evolution as both the current ribbons and the EUV flare ribbons obtained several times during the flare. Conclusions: For the first time, we propose a combined analysis of the photospheric

  15. Stochastic Particle Acceleration in Impulsive Solar Flares

    NASA Technical Reports Server (NTRS)

    Miller, James A.

    2001-01-01

    The acceleration of a huge number of electrons and ions to relativistic energies over timescales ranging from several seconds to several tens of seconds is the fundamental problem in high-energy solar physics. The cascading turbulence model we have developed has been shown previously (e.g., Miller 2000; Miller & Roberts 1995; Miner, LaRosa, & Moore 1996) to account for all the bulk features (such as acceleration timescales, fluxes, total number of energetic particles, and maximum energies) of electron and proton acceleration in impulsive solar flares. While the simulation of this acceleration process is involved, the essential idea of the model is quite simple, and consists of just a few parts: 1. During the primary flare energy release phase, we assume that low-amplitude MHD Alfven and fast mode waves are excited at long wavelengths, say comparable to the size of the event (although the results are actually insensitive to this initial wavelength). While an assumption, this appears reasonable in light of the likely highly turbulent nature of the flare. 2. These waves then cascade in a Kolmogorov-like fashion to smaller wavelengths (e.g., Verma et al. 1996), forming a power-law spectral density in wavenumber space through the inertial range. 3. When the mean wavenumber of the fast mode waves has increased sufficiently, the transit-time acceleration rate (Miller 1997) for superAlfvenic electrons can overcome Coulomb energy losses, and these electrons are accelerated out of the thermal distribution and to relativistic energies (Miller et al. 1996). As the Alfven waves cascade to higher wavenumbers, they can cyclotron resonate with progressively lower energy protons. Eventually, they will resonate with protons in the tail of the thermal distribution, which will then be accelerated to relativistic energies as well (Miller & Roberts 1995). Hence, both ions and electrons are stochastically accelerated, albeit by different mechanisms and different waves. 4. When the

  16. 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.

  17. A statistic study of ionospheric solar flare activity indicator

    NASA Astrophysics Data System (ADS)

    Xiong, Bo; Wan, Weixing; Ning, Baiqi; Ding, Feng; Hu, Lianhuan; Yu, You

    2014-01-01

    According to the Chapman ionization theory, an ionospheric solar flare activity indicator (ISFAI) is given by the solar zenith angle and the variation rate of ionospheric vertical total electron content, which is measured from a global network of dual-frequency GPS receivers. The ISFAI is utilized to statistically analyze the ionospheric responses to 1439 M-class and 126 X-class solar flares during solar cycle 23 (1996-2008). The statistical results show that the occurrence of ISFAI peak increases obviously at 3.2 total electron content unit (TECU)/h (1 TECU = 1016 el m-2) and reaches the maximum at 10 TECU/h during M-class flares and 10 TECU/h and 40 TECU/h for X-class flares. ISFAI is closely correlated with the 26-34 nm extreme ultraviolet flux but poorly related to the 0.1-0.8 nm X-ray flux. The central meridian distance (CMD) of flare location is an important reason for depressing relationship between ISFAI and X-ray Flux. Through the CMD effect modification, the ISFAI has a significant dependence on the X-ray flux with a correlation coefficient of 0.76. The ISFAI sensitivity enables to detect the extreme X-class flares, as well as the variations of one order of magnitude or even smaller (such as for C-class flares). Meanwhile, ISFAI is helpful to the calibration of the X-ray flux at 0.1-0.8 nm observed by GOES during some flares. In addition, the statistical results demonstrate that ISFAI can detect 80% of all M-class flares and 92% for all X-class ones during 1996-2008.

  18. Blazar flares powered by plasmoids in relativistic reconnection

    NASA Astrophysics Data System (ADS)

    Petropoulou, Maria; Giannios, Dimitrios; Sironi, Lorenzo

    2016-11-01

    Powerful flares from blazars with short (˜min) variability time-scales are challenging for current models of blazar emission. Here, we present a physically motivated ab initio model for blazar flares based on the results of recent particle-in-cell (PIC) simulations of relativistic magnetic reconnection. PIC simulations demonstrate that quasi-spherical plasmoids filled with high-energy particles and magnetic fields are a self-consistent by-product of the reconnection process. By coupling our PIC-based results (i.e. plasmoid growth, acceleration profile, particle and magnetic content) with a kinetic equation for the evolution of the electron distribution function we demonstrate that relativistic reconnection in blazar jets can produce powerful flares whose temporal and spectral properties are consistent with the observations. In particular, our model predicts correlated synchrotron and synchrotron self-Compton flares of duration of several hours-days powered by the largest and slowest moving plasmoids that form in the reconnection layer. Smaller and faster plasmoids produce flares of sub-hour duration with higher peak luminosities than those powered by the largest plasmoids. Yet, the observed fluence in both types of flares is similar. Multiple flares with a range of flux-doubling time-scales (minutes to several hours) observed over a longer period of flaring activity (days or longer) may be used as a probe of the reconnection layer's orientation and the jet's magnetization. Our model shows that blazar flares are naturally expected as a result of magnetic reconnection in a magnetically dominated jet.

  19. TIME-DEPENDENT MODELS OF FLARES FROM SAGITTARIUS A*

    SciTech Connect

    Dodds-Eden, Katie; Genzel, Reinhard; Gillessen, Stefan; Eisenhauer, Frank; Sharma, Prateek; Quataert, Eliot; Porquet, Delphine

    2010-12-10

    The emission from Sgr A*, the supermassive black hole in the Galactic Center, shows order of magnitude variability ('flares') a few times a day that is particularly prominent in the near-infrared (NIR) and X-rays. We present a time-dependent model for these flares motivated by the hypothesis that dissipation of magnetic energy powers the flares. We show that episodic magnetic reconnection can occur near the last stable circular orbit in time-dependent magnetohydrodynamic simulations of black hole accretion-the timescales and energetics of these events are broadly consistent with the flares from Sgr A*. Motivated by these results, we present a spatially one-zone time-dependent model for the electron distribution function in flares, including energy loss due to synchrotron cooling and adiabatic expansion. Synchrotron emission from transiently accelerated particles can explain the NIR/X-ray light curves and spectra of a luminous flare observed on 2007 April 4. A significant decrease in the magnetic field strength during the flare (coincident with the electron acceleration) is required to explain the simultaneity and symmetry of the simultaneous light curves. Our models predict that the NIR and X-ray spectral indices are related by {Delta}{alpha} {approx_equal} 0.5 (where {nu}F{sub {nu}} {proportional_to} {nu}{sup {alpha}}) and that there is only modest variation in the spectral index during flares. We also explore implications of this model for longer wavelength (radio-submillimeter) emission seemingly associated with X-ray and NIR flares; we argue that a few hour decrease in the submillimeter emission is a more generic consequence of large-scale magnetic reconnection than delayed radio emission from adiabatic expansion.

  20. Solar flare protection for manned lunar missions - Analysis of the October 1989 proton flare event

    SciTech Connect

    Simonsen, L.C.; Nealy, J.E.; Townsend, L.W.; Sauer, H.H. NOAA, Space Environment Laboratory, Boulder, CL )

    1991-07-01

    Several large solar proton events occurred in the latter half of 1989. For a moderately shielded spacecraft in free space, the potential exposure would have been greatest for the flare which occurred between October 19 to 27, 1989. The temporal variations of the proton energy spectra at approximately 1 AU were monitored by the GOES-7 satellite. These data, recorded and processed at the NOAA-Boulder Space Environment Laboratory, provide the opportunity to analyze dose rates and cumulative doses which might be incurred by astronauts in transit to, or on, the moon. Of particular importance in such an event is the time development of exposure in the early phases of the flare, for which dose rates may range over many orders of magnitude in the first few hours. The cumulative dose as a function of time for the entire event is also predicted. In addition to basic shield calculations, dose rate contours are constructed for flare shelters in free-space and on the lunar surface. 14 refs.

  1. SUNSPOT ROTATION, FLARE ENERGETICS, AND FLUX ROPE HELICITY: THE ERUPTIVE FLARE ON 2005 MAY 13

    SciTech Connect

    Kazachenko, Maria D.; Canfield, Richard C.; Longcope, Dana W.; Qiu, Jiong; DesJardins, Angela; Nightingale, Richard W.

    2009-10-20

    We use the Michelson Doppler Imager and TRACE observations of photospheric magnetic and velocity fields in NOAA 10759 to build a three-dimensional coronal magnetic field model. The most dramatic feature of this active region is the 34{sup 0} rotation of its leading polarity sunspot over 40 hr. We describe a method for including such rotation in the framework of the Minimum Current Corona model. We apply this method to the buildup of energy and helicity associated with the eruptive flare of 2005 May 13. We find that including the sunspot rotation almost triples the modeled flare energy (1.0 x 10{sup 31} erg) and flux rope self-helicity (-7.1 x 10{sup 42} Mx{sup 2}). This makes the results consistent with observations: the energy derived from GOES is 1.0 x 10{sup 31} erg, the magnetic cloud helicity from WIND is -5 x 10{sup 42} Mx{sup 2}. Our combined analysis yields the first quantitative picture of the helicity and energy content processed through a flare in an active region with an obviously rotating sunspot and shows that rotation dominates the energy and helicity budget of this event.

  2. Flare fragmentation and type III productivity in the 1980 June 27 flare

    NASA Technical Reports Server (NTRS)

    Aschwanden, M. J.; Schwartz, R. A.; Benz, A. O.; Lin, R. P.; Pelling, R. M.

    1990-01-01

    Observations of the solar flare on June 27, 1980 were presented, 16:14-16:33 UT, which was observed by a balloon-borne 300 sq cm phoswich hard X-ray detector and by the IKARUS radio spectrometer. This flare shows intense hard X-ray (HXR) emission and an extreme productivity of (at least 754) type III bursts at 200-400 MHz. A linear correlation was found between the type III burst rate and the HXR fluence. The occurrence of about 10 type III bursts/second, and also the even higher rate of millisecond spikes, suggests a high degree of fragmentation in the acceleration region. This high quantization of injected beams, assuming the thick-target model, shows up in a linear relationship between hard X-ray fluence and the type III rate, but not as fine structures in the HXR time profile. The generation of a superhot isothermal HXR component in the decay phase of the flare coincides with the fade-out of type III production.

  3. Self Motion Perception and Motion Sickness

    NASA Technical Reports Server (NTRS)

    Fox, Robert A. (Principal Investigator)

    1991-01-01

    The studies conducted in this research project examined several aspects of motion sickness in animal models. A principle objective of these studies was to investigate the neuroanatomy that is important in motion sickness with the objectives of examining both the utility of putative models and defining neural mechanisms that are important in motion sickness.

  4. Efficiency of Natural Gas Flares Associated with Shale Formation Wells

    NASA Astrophysics Data System (ADS)

    Stirm, B.; Caulton, D.; Shepson, P.; Cambaliza, M. L.; Mccabe, D. C.; Baum, E.

    2012-12-01

    Hydraulic fracturing has increased access and economic viability of shale oil reserves. Currently the Bakken Oil field in North Dakota is experiencing a rapid increase in the drilling of shale oil wells. However, this process typically results in the simultaneous release of natural gas. Low natural gas prices and the lack of local gas pipeline infrastructure have decreased the incentive for companies to capture this natural gas, with many opting to vent or flare the natural gas instead. The impact of these operations on greenhouse gas emissions has not been well characterized. An undocumented variable of interest is the destruction efficiency of methane in active oil field flares. In situ measurements of flare efficiency are difficult to obtain because of the inaccessibility of the flares. In June of 2012 we conducted flights over shale oil wells and flares in the Bakken Formation near Williston, ND using Purdue University's Airborne Laboratory for Atmospheric Research (ALAR) which is equipped with a 0.5 Hz Picarro CO2/CH4/H2O analyzer and a Best Air Turbulence (BAT) probe that measures the wind vectors. In addition, one flare in the Marcellus Formation near Washington, PA was also sampled. Flare signals were identified based on the enhancements of CO2 above the ambient background signal and the corresponding colocated CH4 concentration. Enhancements were isolated by subtracting the background concentrations of CO2 and CH4 to obtain delta CO2 and delta CH4 values. Emission factors to be reported are obtained as the ratio delta CH4 divided by delta CO2. We will report first in situ measurements of natural gas flare efficiency. We observed a variety of meteorological conditions with winds ranging from 4 to 15 m/s and will report on the relationship between wind speed and flare efficiency. We observed very high flare efficiency even under strong winds (at least 99.8% CO2 for all flares). During flare sampling, we observed a number of CH4 enhancements that were

  5. Observations of solar flare gamma-rays and protons

    NASA Technical Reports Server (NTRS)

    Yoshimori, M.; Watanabe, H.

    1985-01-01

    Solar flare gamma-rays (4 to 7 MeV) and protons (8 to 500 MeV) were simultaneously observed from six flares on 1 Apr., 4 Apr., 27, Apr. 13, May 1981, 1 Feb. and 6 June 1982 by the Hinotori and GMS satellites. The relationship between 4 to 7 MeV gamma-ray fluences and peak 16 to 34 MeV proton fluxes for these flares are analyzed. It does not reveal an apparent correlation between these two parameters. The present result implies that the protons producing gamma-rays and the protons observed near the Earth do not always belong to the same population.

  6. Studying the thermal/non-thermal crossover in solar flares

    NASA Technical Reports Server (NTRS)

    Schwartz, R. A.

    1994-01-01

    This report describes work performed under contract NAS5-32584 for Phase 3 of the Compton Gamma Ray Observatory (CGRO) from 1 November 1993 through 1 November 1994. We have made spectral observations of the hard x-ray and gamma-ray bremsstrahlung emissions from solar flares using the Burst and Transit Source Experiment (BASTE) on CGRO. These measurements of their spectrum and time profile provided valuable information on the fundamental flare processes of energy release, particle acceleration, and energy transport. Our scientific objective was to study both the thermal and non-thermal sources of solar flare hard x-ray and gamma-ray emission.

  7. Solar flares, proton showers, and the space shuttle.

    PubMed

    Rust, D M

    1982-05-28

    The space shuttle era will focus renewed attention on the hazards of the space environment to human habitation. The chief unpredictable hazard for astronauts is energetic proton radiation from solar flares. In some orbits, there is no reasonable level of shielding material that will protect shuttle occupants from potentially lethal doses of radiation. The effects of a solar flare that occurred druing the first flight of the Columbia are discussed and current flare research reviewed. The emphasis is on progress made during the recent international Solar Maximum Year toward understanding the origins of proton showers.

  8. The Carrington solar flares of 1859: consequences on life.

    PubMed

    Muller, C

    2014-09-01

    The beginning of September 1859 was the occasion of the first and unique observation of a giant solar white light flare, auroral displays were observed at low latitudes and geomagnetic observatories recorded exceptional storms. This paper reviews the impact of the event on the earth system with a special emphasis on living processes using the historical record and current scientific analysis. The data used includes reports from the telegraph operators, mortality and morbidity records, proxies as agricultural production. Comparisons with later solar flare events will be attempted on the basis of the record and the consequences of an event of comparable magnitude to the 1859 set of flares will be discussed.

  9. The Carrington Solar Flares of 1859: Consequences on Life

    NASA Astrophysics Data System (ADS)

    Muller, C.

    2014-09-01

    The beginning of September 1859 was the occasion of the first and unique observation of a giant solar white light flare, auroral displays were observed at low latitudes and geomagnetic observatories recorded exceptional storms. This paper reviews the impact of the event on the earth system with a special emphasis on living processes using the historical record and current scientific analysis. The data used includes reports from the telegraph operators, mortality and morbidity records, proxies as agricultural production. Comparisons with later solar flare events will be attempted on the basis of the record and the consequences of an event of comparable magnitude to the 1859 set of flares will be discussed.

  10. Energetics and dynamics of simple impulsive solar flares

    NASA Technical Reports Server (NTRS)

    Starr, R.; Heindl, W. A.; Crannell, C. J.; Thomas, R. J.; Batchelor, D. A.; Magun, A.

    1987-01-01

    Flare energetics and dynamics were studied using observations of simple impulsive spike bursts. A large, homogeneous set of events was selected to enable the most definite tests possible of competing flare models, in the absence of spatially resolved observations. The emission mechanisms and specific flare models that were considered in this investigation are described, and the derivations of the parameters that were tested are presented. Results of the correlation analysis between soft and hard X-ray energetics are also presented. The ion conduction front model and tests of that model with the well-observed spike bursts are described. Finally, conclusions drawn from this investigation and suggestions for future studies are discussed.

  11. Excitation of Resonant Helioseimic Modes by Solar Flares.

    NASA Astrophysics Data System (ADS)

    Leibacher, John W.; Baudin, Frédéric; Rabello Soares,, Maria Cristina

    2015-08-01

    Flares are known to excite propagating sound waves in the solar atmosphere, and Maurya et al. (2009), using a local analysis (ring diagrams) of the 2003 Halloween flare, showed that they excite resonant p-modes as well. We confirm and extend here these results by:-applying the same analysis to other locations on the Sun at the time of the Halloween flare-analyzing other events also showing a signature of p-mode excitation-looking in detail at the results of the ring diagrams analysis in terms of noise fitting and the center-to-limb variation of ring-diagram power.

  12. Excitation of Resonant Helioseimic Modes by Solar Flares

    NASA Astrophysics Data System (ADS)

    Leibacher, John William; Baudin, Frédéric; Rabello Soares, Maria Cristina

    2015-04-01

    Flares are known to excite propagating sound waves in the solar atmosphere, and Maurya et al. (2009), using a local analysis (ring diagrams) of the 2003 Halloween flare, showed that they excite resonant p-modes as well. We confirm and extend here these results by: applying the same analysis to other locations on the Sun at the time of the Halloween flare, analyzing other events also showing a signature of p-mode excitation, looking in detail at the results of the ring diagrams analysis in terms of noise fitting and the center-to-limb variation of ring-diagram power.

  13. The Carrington solar flares of 1859: consequences on life.

    PubMed

    Muller, C

    2014-09-01

    The beginning of September 1859 was the occasion of the first and unique observation of a giant solar white light flare, auroral displays were observed at low latitudes and geomagnetic observatories recorded exceptional storms. This paper reviews the impact of the event on the earth system with a special emphasis on living processes using the historical record and current scientific analysis. The data used includes reports from the telegraph operators, mortality and morbidity records, proxies as agricultural production. Comparisons with later solar flare events will be attempted on the basis of the record and the consequences of an event of comparable magnitude to the 1859 set of flares will be discussed. PMID:25351684

  14. SUCCESSIVE SOLAR ERUPTIONS TRIGGERED BY THE COLLISION OF TWO SMALL SUNSPOTS WITH OPPOSITE POLARITIES AND MOTIONAL DIRECTIONS

    SciTech Connect

    Yan, X. L.; Qu, Z. Q.; Kong, D. F.

    2012-03-15

    We present a study of the two successive M-class flares associated with two coronal mass ejections (CMEs) triggered by the collision of two small sunspots with opposite magnetic polarities and motional directions in NOAA active region (AR) 10484 on 2003 October 22. From the evolution of this AR in the TRACE white-light images and 96 minute line-of-sight magnetograms observed by the Michelson Doppler Imager on board SOHO, a large sunspot and a small sunspot with negative polarity rotated clockwise about 33 Degree-Sign and 18 Degree-Sign , respectively, from the northeast of a quiescent sunspot with negative polarity to the southeast from 15:00 UT on October 21 to 16:24 UT on October 23. During the process of their motion, the small sunspot with negative polarity collided with the small sunspot with positive polarity and opposite motional direction. In the collision, this AR produced two successive M-class flares and CMEs according to the observations of GOES and the Large Angle and Spectrometric Coronagraph. By analyzing the magnetic fields at polarity inversion lines (PILs) between the two small sunspot, it is found that a sudden squeeze occurred near the onset of the two M-class flares and then recovered itself after the flares. We ruled out the emergence of the magnetic fields near the PIL. According to the brightenings in TRACE 1600 A and the hard X-ray sources of the RHESSI of two M-class flares, we found that the locations of the two flares are almost situated in the same location at the PIL between the two small sunspots. We suggest that the sudden squeeze between the opposite magnetic polarities is caused by the pressure of the collision of the two small sunspots and resulted in the magnetic reconnection. These results could contribute to understanding the mechanism of flares and CMEs.

  15. Electron precipitation in solar flares - Collisionless effects

    NASA Technical Reports Server (NTRS)

    Vlahos, L.; Rowland, H. L.

    1984-01-01

    A large fraction of the electrons which are accelerated during the impulsive phase of solar flares stream towards the chromosphere and are unstable to the growth of plasma waves. The linear and nonlinear evolution of plasma waves as a function of time is analyzed with a set of rate equations that follows, in time, the nonlinearly coupled system of plasma waves-ion fluctuations. As an outcome of the fast transfer of wave energy from the beam to the ambient plasma, nonthermal electron tails are formed which can stabilize the anomalous Doppler resonance instability responsible for the pitch angle scattering of the beam electrons. The non-collisional losses of the precipitating electrons are estimated, and the observational implication of these results are discussed.

  16. BLAZAR FLARES FROM COMPTON DRAGGED SHELLS

    SciTech Connect

    Golan, Omri; Levinson, Amir

    2015-08-10

    We compute the dynamics and emission of dissipative shells that are subject to a strong Compton drag, under simplifying assumptions about the dissipation mechanism. We show that under conditions prevailing in blazars, substantial deceleration is anticipated on sub-parsec and parsec scales in cases of rapid dissipation. Such episodes may be the origin of some of the flaring activity occasionally observed in gamma-ray blazars. The shape of the light curves thereby produced reflects the geometry of the emitting surface if the deceleration is very rapid, or the dynamics of the shell if the deceleration is delayed, or initially more gradual, owing, e.g., to continuous injection of energy and momentum.

  17. Ultraheavy element enrichment in impulsive solar flares

    SciTech Connect

    Eichler, David

    2014-10-10

    Particle acceleration by cascading Alfvén wave turbulence was suggested as being responsible for energetic particle populations in {sup 3}He-rich solar flares. In particular, it was noted that the damping of the turbulence by the tail of the particle distribution in rigidity naturally leads to the dramatic enhancement of a pre-accelerated species—as {sup 3}He is posited to be—and superheavy elements. The subsequent detection of large enrichment of ultraheavies, relative to iron, has apparently confirmed this prediction, lending support to the original idea. It is shown here that this picture could be somewhat sharpened by progress in understanding the three-dimensional geometrical details of cascading Alfvén turbulence. The mechanism may be relevant in other astrophysical environments where the source of turbulence is nonmagnetic, such as clusters of galaxies.

  18. Stochastic acceleration of solar flare protons

    NASA Technical Reports Server (NTRS)

    Barbosa, D. D.

    1978-01-01

    The acceleration of solar flare protons is considered by cyclotron damping of intense Alfven wave turbulence in a magnetic trap. The energy diffusion coefficient is computed for a near-isotropic distribution of super-Alfvenic protons and a steady-state solution for the particle spectrum is found for both transit-time and diffusive losses out of the ends of the trap. The acceleration time to a characteristic energy approximately 20 Mev/nucl can be as short as 10 sec. On the basis of phenomenological arguments an omega/2 frequency dependence for the Alfven wave spectrum is inferred. The correlation time of the turbulence lies in the range .0005 less than tau/corr less than .05s.

  19. Comparative study of flare control laws

    NASA Technical Reports Server (NTRS)

    Nadkarni, A. A.

    1981-01-01

    The development of a digital, three dimensional, automatic control law designed to achieve an optimal transition of a B-737 aircraft between glide slope conditions and the desired final touchdown condition is presented. The digital control law is a time invariant, state estimate feedback law, and the design is capable of using the microwave landing system. Major emphasis is placed on the reduction of aircraft noise in communities surroundings airports, the reduction of fuel consumption, the reduction of the effects of adverse weather conditions on aircraft operations, and the efficient use of airspace in congested terminal areas. Attention is also given to the development of the capability to perform automatic flares from steep glide slopes to precise touchdown locations.

  20. Modern observations and models of Solar flares

    NASA Astrophysics Data System (ADS)

    Gritsyk, Pavel; Somov, Boris

    As well known, that fast particles propagating along flare loop generate bremsstrahlung hard x-ray emission and gyro-synchrotron microwave emission. We present the self-consistent kinetic description of propagation accelerated particles. The key point of this approach is taking into account the effect of reverse current. In our two-dimensional model the electric field of reverse current has the strong influence to the beam of accelerated particles. It decelerates part of the electrons in the beam and turns back other part of them without significant energy loss. The exact analytical solution for the appropriate kinetic equation with Landau collision integral was found. Using derived distribution function of electrons we’ve calculated evolution of their energy spectrum and plasma heating, coronal microwave emission and characteristics of hard x-ray emission in the corona and in the chromosphere. All results were compared with modern high precision space observations.

  1. Solar Dynamics Observatory Sees Solar Flare

    NASA Video Gallery

    A movie of the March 30, 2010 prominence eruption, starting with a zoomed in view. The twisting motion of the material is the most noticeable feature. The viewpoint then pulls out to show the entir...

  2. The first observed stellar X-ray flare oscillation: Constraints on the flare loop length and the magnetic field

    NASA Astrophysics Data System (ADS)

    Mitra-Kraev, U.; Harra, L. K.; Williams, D. R.; Kraev, E.

    2005-06-01

    We present the first X-ray observation of an oscillation during a stellar flare. The flare occurred on the active M-type dwarf AT Mic and was observed with XMM-Newton. The soft X-ray light curve (0.2-12 keV) is investigated with wavelet analysis. The flare's extended, flat peak shows clear evidence for a damped oscillation with a period of around 750 s, an exponential damping time of around 2000 s, and an initial, relative peak-to-peak amplitude of around 15%. We suggest that the oscillation is a standing magneto-acoustic wave tied to the flare loop, and find that the most likely interpretation is a longitudinal, slow-mode wave, with a resulting loop length of (2.5 ± 0.2)×1010 cm. The local magnetic field strength is found to be 105 ± 50 G. These values are consistent with (oscillation-independent) flare cooling time models and pressure balance scaling laws. Such a flare oscillation provides an excellent opportunity to obtain coronal properties like the size of a flare loop or the local magnetic field strength for the otherwise spatially-unresolved star.

  3. ASYMMETRIC MAGNETIC RECONNECTION IN SOLAR FLARE AND CORONAL MASS EJECTION CURRENT SHEETS

    SciTech Connect

    Murphy, N. A.; Miralles, M. P.; Pope, C. L.; Raymond, J. C.; Winter, H. D.; Reeves, K. K.; Van Ballegooijen, A. A.; Lin, J.; Seaton, D. B.

    2012-05-20

    We present two-dimensional resistive magnetohydrodynamic simulations of line-tied asymmetric magnetic reconnection in the context of solar flare and coronal mass ejection current sheets. The reconnection process is made asymmetric along the inflow direction by allowing the initial upstream magnetic field strengths and densities to differ, and along the outflow direction by placing the initial perturbation near a conducting wall boundary that represents the photosphere. When the upstream magnetic fields are asymmetric, the post-flare loop structure is distorted into a characteristic skewed candle flame shape. The simulations can thus be used to provide constraints on the reconnection asymmetry in post-flare loops. More hard X-ray emission is expected to occur at the footpoint on the weak magnetic field side because energetic particles are more likely to escape the magnetic mirror there than at the strong magnetic field footpoint. The footpoint on the weak magnetic field side is predicted to move more quickly because of the requirement in two dimensions that equal amounts of flux must be reconnected from each upstream region. The X-line drifts away from the conducting wall in all simulations with asymmetric outflow and into the strong magnetic field region during most of the simulations with asymmetric inflow. There is net plasma flow across the X-line for both the inflow and outflow directions. The reconnection exhaust directed away from the obstructing wall is significantly faster than the exhaust directed toward it. The asymmetric inflow condition allows net vorticity in the rising outflow plasmoid which would appear as rolling motions about the flux rope axis.

  4. Energetic electrons in impulsive solar flares

    NASA Technical Reports Server (NTRS)

    Batchelor, D. A.

    1984-01-01

    A new analysis was made of a thermal flare model proposed by Brown, Melrose, and Spicer (1979) and Smith and Lilliequist (1979). They assumed the source of impulsive hard X-rays to be a plasma at a temperature of order 10 to the 8th power K, initially located at the apex of a coronal arch, and confined by ion-acoustic turbulence in a collisionless conduction front. Such a source would expand at approximately the ion-sound speed, C sub S = square root of (k T sub e/m sub i), until it filled the arch. Brown, Melrose, and Spicer and Smith and Brown (1980) argued that the source assumed in this model would not explain the simultaneous impulsive microwave emission. In contrast, the new results presented herein suggest that this model leads to the development of a quasi-Maxwellian distribution of electrons that explains both the hard X-ray and microwave emissions. This implies that the source sizes can be determined from observations of the optically-thick portions of microwave spectra and the temperatures obtained from associated hard X-ray observations. In this model, the burst emission would rise to a maximum in a time, t sub r, approximately equal to L/c sub s, where L is the half-length of the arch. New observations of these impulsive flare emissions were analyzed herein to test this prediction of the model. Observations made with the Solar Maximum Mission spacecraft and the Bern Radio Observatory are in good agreement with the model.

  5. Electron acceleration in impulsive solar flares

    SciTech Connect

    Kane, S.R.; Benz, A.O.; Treumann, R.A.

    1982-12-01

    Simultaneous observations of the hard X-ray, microwave, and type III and DCIM (decimetric)radio bursts associated with the 1978 December 4 solar flare have been used to study the physical parameters relevant to the acceleration and propagation of energetic electrons during the impulsive phase of a solar flare. The hard X-ray observations were made with the X-ray spectrometer aboard the ISEE 3 spacecraft. The radio spectra in metric and decimetric bands were recorded with the radiospectrograph located at Durnten, near Zurich, Switzerland. The microwave observations were made at the Sagamore Hill and Bern observatories. The three metric type III bursts coincided with the three most prominent hard X-ray peaks. This is the fist time a clear one-to-one association between single type III bursts and hard X-ray peaks has been established. The average delay of the type III bursts with respect to the X-ray peaks was 0.5 s. The harder the X-ray spectrum, the higher was the drift rate of the associated type III burst. The characteristic electron energies inferred from the drift rate are of the order of 70 keV. The observed increase in the high-frequency cutoff of the metric type III bursts during the impulsive phase has been examined in terms of the decreasing altitude of the electron acceleration/injection region, the increasing hardness of the electron spectrum, and the decreasing acceleration time. A pulsating decimetric continuum (DCIM) was also found to be present during and before the impulsive phase. The DCIM source seems to coincide spatially with the electron acceleration region and the (projected) origin of the associated type II shock.ction region.

  6. Pre-flare Activity and Magnetic Reconnection during the Evolutionary Stages of Energy Release in a Solar Eruptive Flare

    NASA Astrophysics Data System (ADS)

    Joshi, Bhuwan; Veronig, Astrid M.; Lee, Jeongwoo; Bong, Su-Chan; Tiwari, Sanjiv Kumar; Cho, Kyung-Suk

    2011-12-01

    In this paper, we present a multi-wavelength analysis of an eruptive white-light M3.2 flare that occurred in active region NOAA 10486 on 2003 November 1. The excellent set of high-resolution observations made by RHESSI and the TRACE provides clear evidence of significant pre-flare activities for ~9 minutes in the form of an initiation phase observed at EUV/UV wavelengths followed by an X-ray precursor phase. During the initiation phase, we observed localized brightenings in the highly sheared core region close to the filament and interactions among short EUV loops overlying the filament, which led to the opening of magnetic field lines. The X-ray precursor phase is manifested in RHESSI measurements below ~30 keV and coincided with the beginning of flux emergence at the flaring location along with early signatures of the eruption. The RHESSI observations reveal that both plasma heating and electron acceleration occurred during the precursor phase. The main flare is consistent with the standard flare model. However, after the impulsive phase, an intense hard X-ray (HXR) looptop source was observed without significant footpoint emission. More intriguingly, for a brief period, the looptop source exhibited strong HXR emission with energies up to ~50-100 keV and significant non-thermal characteristics. The present study indicates a causal relation between the activities in the pre-flare and the main flare. We also conclude that pre-flare activities, occurring in the form of subtle magnetic reorganization along with localized magnetic reconnection, played a crucial role in destabilizing the active region filament, leading to a solar eruptive flare and associated large-scale phenomena.

  7. Self-Motion Perception and Motion Sickness

    NASA Technical Reports Server (NTRS)

    Fox, Robert A.

    1991-01-01

    Motion sickness typically is considered a bothersome artifact of exposure to passive motion in vehicles of conveyance. This condition seldom has significant impact on the health of individuals because it is of brief duration, it usually can be prevented by simply avoiding the eliciting condition and, when the conditions that produce it are unavoidable, sickness dissipates with continued exposure. The studies conducted examined several aspects of motion sickness in animal models. A principle objective of these studies was to investigate the neuroanatomy that is important in motion sickness with the objectives of examining both the utility of putative models and defining neural mechanisms that are important in motion sickness.

  8. EVIDENCE FOR COLLAPSING FIELDS IN THE CORONA AND PHOTOSPHERE DURING THE 2011 FEBRUARY 15 X2.2 FLARE: SDO/AIA AND HMI OBSERVATIONS

    SciTech Connect

    Gosain, S.

    2012-04-10

    We use high-resolution Solar Dynamics Observatory (SDO)/Atmospheric Imaging Assembly observations to study the evolution of the coronal loops in a flaring solar active region, NOAA 11158. We identify three distinct phases of the coronal loop dynamics during this event: (1) slow-rise phase: slow rising motion of the loop-tops prior to the flare in response to the slow rise of the underlying flux rope; (2) collapse phase: sudden contraction of the loop-tops, with the lower loops collapsing earlier than the higher loops; and (3) oscillation phase: the loops exhibit global kink oscillations after the collapse phase at different periods, with the period decreasing with the decreasing height of the loops. The period of these loop oscillations is used to estimate the field strength in the coronal loops. Furthermore, we also use SDO/Helioseismic and Magnetic Imager (HMI) observations to study the photospheric changes close to the polarity inversion line (PIL). The longitudinal magnetograms show a stepwise permanent decrease in the magnetic flux after the flare over a coherent patch along the PIL. Furthermore, we examine the HMI Stokes I, Q, U, V profiles over this patch and find that the Stokes-V signal systematically decreases while the Stokes-Q and U signals increase after the flare. These observations suggest that close to the PIL the field configuration became more horizontal after the flare. We also use HMI vector magnetic field observations to quantify the changes in the field inclination angle and find an inward collapse of the field lines toward the PIL by {approx}10 Degree-Sign . These observations are consistent with the 'coronal implosion' scenario and its predictions about flare-related photospheric field changes.

  9. Interferometric at-wavelength flare characterization of EUV optical systems

    DOEpatents

    Naulleau, Patrick P.; Goldberg, Kenneth Alan

    2001-01-01

    The extreme ultraviolet (EUV) phase-shifting point diffraction interferometer (PS/PDI) provides the high-accuracy wavefront characterization critical to the development of EUV lithography systems. Enhancing the implementation of the PS/PDI can significantly extend its spatial-frequency measurement bandwidth. The enhanced PS/PDI is capable of simultaneously characterizing both wavefront and flare. The enhanced technique employs a hybrid spatial/temporal-domain point diffraction interferometer (referred to as the dual-domain PS/PDI) that is capable of suppressing the scattered-reference-light noise that hinders the conventional PS/PDI. Using the dual-domain technique in combination with a flare-measurement-optimized mask and an iterative calculation process for removing flare contribution caused by higher order grating diffraction terms, the enhanced PS/PDI can be used to simultaneously measure both figure and flare in optical systems.

  10. SDO's View of May 5, 2010 Solar Flare - With Timeline

    NASA Video Gallery

    This video shows a composite view of the solar flare on May 5, 2010, taken by the Solar Dynamics Observatory's (SDO) Atmospheric Imaging Assembly (AIA) cameras in multiple wavelengths (211, 193, 17...

  11. The Solar Flare Myth in solar-terrestrial physics

    SciTech Connect

    Gosling, J.T.

    1993-07-01

    Early observations of associations between solar flares and large non- recurrent geomagnetic storms, large {open_quote}solar{close_quote} energetic particle events, and transient shock wave disturbances in the solar wind led to a paradigm of cause and effect that gave flares a central position in the chain of events leading from solar activity to major transient disturbances in the near-earth space environment. However, research in the last two decades shows that this emphasis on flares is misplaced. In this paper the author outlines briefly the rationale for a different paradigm of cause and effect in solar- terrestrial physics that removes solar flares from their central position as the {open_quote}cause{close_quote} of major disturbances in the near-earth space environment. Instead, this central role of {open_quote}cause{close_quote} is played by events now known as coronal mass ejections, or CMEs.

  12. 213. 'SAFTEY FLARED INTERSECTION' NEAR COLLINGWOOD, 1932. ORIGINAL CAPTION READ ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    213. 'SAFTEY FLARED INTERSECTION' NEAR COLLINGWOOD, 1932. ORIGINAL CAPTION READ ''STREAMLINING' THE MOVEMENT OF HIGH SPEED MODERN TRAFFIC. - George Washington Memorial Parkway, Along Potomac River from McLean to Mount Vernon, VA, Mount Vernon, Fairfax County, VA

  13. Solar flares, proton showers, and the Space Shuttle

    NASA Technical Reports Server (NTRS)

    Rust, D. M.

    1982-01-01

    Attention is given the hazards posed to Space Shuttle crews by energetic proton radiation from inherently unpredictable solar flares, such as that of April 10-13, 1981, which was experienced by the Space Shuttle Columbia. The most energetic protons from this flare reached the earth's atmosphere an hour after flare onset, and would have posed a potentially lethal threat to astronauts engaged in extravehicular activity in a polar or geosynchronous orbit rather than the low-latitude, low-altitude orbit of this mission. It is shown that proton-producing flares are associated with energization in shocks, many of which are driven by coronal mass ejections. Insights gained from the Solar Maximum Year programs allow reconsideration of proton shower forecasting, which will be essential in the prediction of the weather that Space Shuttle astronauts will encounter during extravehicular activities.

  14. Optical microflaring on the nearby flare star binary UV Ceti

    NASA Astrophysics Data System (ADS)

    Schmitt, J. H. M. M.; Kanbach, G.; Rau, A.; Steinle, H.

    2016-05-01

    We present extremely high time resolution observations of the visual flare star binary UV Cet obtained with the Optical Pulsar Timing Analyzer (OPTIMA) at the 1.3 m telescope at Skinakas Observatory (SKO) in Crete, Greece. OPTIMA is a fiber-fed optical instrument that uses Single Photon Avalanche Diodes to measure the arrival times of individual optical photons. The time resolution of the observations presented here was 4 μs, allowing to resolve the typical millisecond variability time scales associated with stellar flares. We report the detection of very short impulsive bursts in the blue band with well resolved rise and decay time scales of about 2 s. The overall energetics put these flares at the lower end of the known flare distribution of UV Cet.

  15. Particle acceleration by a solar flare termination shock.

    PubMed

    Chen, Bin; Bastian, Timothy S; Shen, Chengcai; Gary, Dale E; Krucker, Säm; Glesener, Lindsay

    2015-12-01

    Solar flares--the most powerful explosions in the solar system--are also efficient particle accelerators, capable of energizing a large number of charged particles to relativistic speeds. A termination shock is often invoked in the standard model of solar flares as a possible driver for particle acceleration, yet its existence and role have remained controversial. We present observations of a solar flare termination shock and trace its morphology and dynamics using high-cadence radio imaging spectroscopy. We show that a disruption of the shock coincides with an abrupt reduction of the energetic electron population. The observed properties of the shock are well reproduced by simulations. These results strongly suggest that a termination shock is responsible, at least in part, for accelerating energetic electrons in solar flares.

  16. Do Large-Scale Topological Features Correlate with Flare Properties?

    NASA Astrophysics Data System (ADS)

    DeRosa, Marc L.; Barnes, Graham

    2016-05-01

    In this study, we aim to identify whether the presence or absence of particular topological features in the large-scale coronal magnetic field are correlated with whether a flare is confined or eruptive. To this end, we first determine the locations of null points, spine lines, and separatrix surfaces within the potential fields associated with the locations of several strong flares from the current and previous sunspot cycles. We then validate the topological skeletons against large-scale features in observations, such as the locations of streamers and pseudostreamers in coronagraph images. Finally, we characterize the topological environment in the vicinity of the flaring active regions and identify the trends involving their large-scale topologies and the properties of the associated flares.

  17. Fast X-ray Oscillations During Magnetar Flares

    NASA Technical Reports Server (NTRS)

    Strohmayer, T.

    2006-01-01

    "We report on recent studies of high frequency variability during magnetar giant flares. These oscillations may represent the first observations of global shear oscillations in neutron star crusts, and can provide a new tools to study neutron star structure.

  18. 8. VAL CAMERA CAR, CLOSEUP VIEW OF 'FLARE' OR TRAJECTORY ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    8. VAL CAMERA CAR, CLOSE-UP VIEW OF 'FLARE' OR TRAJECTORY CAMERA ON SLIDING MOUNT. - Variable Angle Launcher Complex, Camera Car & Track, CA State Highway 39 at Morris Reservior, Azusa, Los Angeles County, CA

  19. 7. VAL CAMERA CAR, DETAIL OF 'FLARE' OR TRAJECTORY CAMERA ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    7. VAL CAMERA CAR, DETAIL OF 'FLARE' OR TRAJECTORY CAMERA INSIDE CAMERA CAR. - Variable Angle Launcher Complex, Camera Car & Track, CA State Highway 39 at Morris Reservior, Azusa, Los Angeles County, CA

  20. SOHO Captures CME From X5.4 Solar Flare

    NASA Video Gallery

    The Solar Heliospheric Observatory (SOHO) captured this movie of the sun's coronal mass ejection (CME) associated with an X5.4 solar flare on the evening of March 6, 2012. The extremely fast and en...

  1. Gamma-ray lines and neutrons from solar flares

    NASA Technical Reports Server (NTRS)

    Ramaty, R.; Murphy, R. J.; Kozlovsky, B.; Lingenfelter, R. E.

    1983-01-01

    The energy spectrum of accelerated protons and nuclei at the site of a limb flare was derived by a technique, using observations of the time dependent flux of high energy neutrons at the earth. This energy spectrum is very similar to the energy spectra of 7 disk flares for which the accelerated particle spectra was previously derived using observations of 4 to 7 MeV to 2.223 MeV fluence ratios. The implied spectra for all of these flares are too steep to produce any significant amount of radiation from pi meson decay. It is suggested that the observed 10 MeV gamma rays from the flare are bremsstrahlung of relativistic electrons. Previously announced in STAR as N83-19695

  2. Gamma-ray lines and neutrons from solar flares

    NASA Technical Reports Server (NTRS)

    Ramaty, R.; Murphy, R. J.; Kozlovsky, B.; Lingenfelter, R. E.

    1983-01-01

    The energy spectrum of accelerated protons and nuclei at the site of a limb flare was derived by a technique, using observations of the time dependent flux of high energy neutrons at the Earth. This energy spectrum is very similar to the energy spectra of 7 disk flares for which the accelerated particle spectra was previously derived using observations of 4 to 7 MeV to 2.223 MeV fluence ratios. The implied spectra for all of these flares are too steep to produce any significant amount of radiation from pi meson decay. It is suggested that the observed 10 MeV gamma rays from the flare are bremsstrahlung of relativistic electrons.

  3. Imaging X-Ray Polarimeter for Solar Flares (IXPS)

    NASA Technical Reports Server (NTRS)

    Hosack, Michael; Black, J. Kevin; Deines-Jones, Philip; Dennis, Brian R.; Hill, Joanne E.; Jahoda, Keith; Shih, Albert Y.; Urba, Christian E.; Emslie, A. Gordon

    2011-01-01

    We describe the design of a balloon-borne Imaging X-ray Polarimeter for Solar flares (IX PS). This novel instrument, a Time Projection Chamber (TPC) for photoelectric polarimetry, will be capable of measuring polarization at the few percent level in the 20-50 keV energy range during an M- or X class flare, and will provide imaging information at the approx.10 arcsec level. The primary objective of such observations is to determine the directivity of nonthermal high-energy electrons producing solar hard X-rays, and hence to learn about the particle acceleration and energy release processes in solar flares. Secondary objectives include the separation of the thermal and nonthermal components of the flare X-ray emissions and the separation of photospheric albedo fluxes from direct emissions.

  4. Olopatadine hydrochloride inhibits capsaicin-induced flare response in humans.

    PubMed

    Shindo, Masahisa; Yoshida, Yuichi; Yamamoto, Osamu

    2011-01-01

    Capsaicin, a vanilloid, has the potential for releasing substance P (SP) from sensory nerves. Topical application of capsaicin induces a flare response in the skin. However, it has not been clarified whether the release of SP is involved in the process of flare response or not. A potent antihistamine drug, olopatadine hydrochloride, is known to have inhibitory action against the release of SP. We examined the effects of olopatadine (at a dose of 5 mg) on skin reaction induced by topical application of capsaicin in 10 healthy subjects. The scores of capsaicin-induced flare responses after olopatadine administration were significantly lower at 30 min than at baseline. Our findings suggest that olopatadine hydrochloride could inhibit capsaicin-induced flare responses.

  5. Stellar flares and the dark energy of CMEs

    NASA Astrophysics Data System (ADS)

    Drake, Jeremy J.; Cohen, Ofer; Garraffo, Cecilia

    2015-08-01

    Flares we observe on stars in white light, UV or soft X-rays are probably harbingers of coronal mass ejections (CMEs). If we use the Sun as a guide, large stellar flares will dissipate much more particle kinetic energy in CMEs than flare radiative energy. Such monster CMEs pose a quandary for understanding the fraction of the energy budget stars can spend on magnetic activity. They could also be the dominant mechanism of angular momentum loss on active stars, and have the potential to ravage planetary atmospheres. We will discuss flare activity, how it might relate to coronal mass ejections, and efforts to understand stellar spin-down and the impact of CMEs on planetary atmospheres using detailed magnetohydrodynamic modelling.

  6. Particle acceleration by a solar flare termination shock.

    PubMed

    Chen, Bin; Bastian, Timothy S; Shen, Chengcai; Gary, Dale E; Krucker, Säm; Glesener, Lindsay

    2015-12-01

    Solar flares--the most powerful explosions in the solar system--are also efficient particle accelerators, capable of energizing a large number of charged particles to relativistic speeds. A termination shock is often invoked in the standard model of solar flares as a possible driver for particle acceleration, yet its existence and role have remained controversial. We present observations of a solar flare termination shock and trace its morphology and dynamics using high-cadence radio imaging spectroscopy. We show that a disruption of the shock coincides with an abrupt reduction of the energetic electron population. The observed properties of the shock are well reproduced by simulations. These results strongly suggest that a termination shock is responsible, at least in part, for accelerating energetic electrons in solar flares. PMID:26785486

  7. Relativistic electron transport and bremsstrahlung production in solar flares

    NASA Astrophysics Data System (ADS)

    Miller, James A.; Ramaty, Reuven

    1989-09-01

    A Monte Carlo simulation of ultrarelativistic electron transport in solar flare magnetic loops has been developed. It includes Coulomb, synchrotron, and bremsstrahlung energy losses; pitch-angle scattering by Alfven and whistler turbulence in the coronal region of the loop; and magnetic mirroring in the converging magnetic flux tubes beneath the transition region. Depth distributions, time profiles, energy spectra, and angular distributions of the resulting bremsstrahlung emission are calculated. It is found that both the preferential detection of solar flares with greater than 10 MeV emission near the limb of the sun and the observation of ultrarelativistic electron bremsstrahlung from flares on the disk are consequences of the loop transport model. The declining portions of the observed time profiles of greater than 10 MeV emission from solar flares can also be accounted for, and it is proposed that these portions are determined by transport and not acceleration.

  8. RECONNECTION-POWERED LINEAR ACCELERATOR AND GAMMA-RAY FLARES IN THE CRAB NEBULA

    SciTech Connect

    Uzdensky, Dmitri A.; Cerutti, BenoIt; Begelman, Mitchell C. E-mail: benoit.cerutti@colorado.edu

    2011-08-20

    The recent discovery of day-long gamma-ray flares in the Crab Nebula, presumed to be synchrotron emission by PeV (10{sup 15} eV) electrons in milligauss magnetic fields, presents a strong challenge to particle acceleration models. The observed photon energies exceed the upper limit ({approx}100 MeV) obtained by balancing the acceleration rate and synchrotron radiation losses under standard conditions where the electric field is smaller than the magnetic field. We argue that a linear electric accelerator, operating at magnetic reconnection sites, is able to circumvent this difficulty. Sufficiently energetic electrons have gyroradii so large that their motion is insensitive to small-scale turbulent structures in the reconnection layer and is controlled only by large-scale fields. We show that such particles are guided into the reconnection layer by the reversing magnetic field as they are accelerated by the reconnection electric field. As these electrons become confined within the current sheet, they experience a decreasing perpendicular magnetic field that may drop below the accelerating electric field. This enables them to reach higher energies before suffering radiation losses and hence to emit synchrotron radiation in excess of the 100 MeV limit, providing a natural resolution to the Crab gamma-ray flare paradox.

  9. Urologic Chronic Pelvic Pain Syndrome Symptom Flares: Characterization of the Full Spectrum of Flares at Two Sites of the Mapp Research Network

    PubMed Central

    Sutcliffe, Siobhan; Colditz, Graham A.; Goodman, Melody S.; Pakpahan, Ratna; Vetter, Joel; Ness, Timothy J.; Andriole, Gerald L.; Lai, H. Henry

    2014-01-01

    Objectives To describe the full spectrum of symptom exacerbations defined by interstitial cystitis/bladder pain syndrome and chronic prostatitis/chronic pelvic pain syndrome patients as flares, and to investigate their associated health-care utilization and bother at two sites of the Trans-Multidisciplinary Approaches to the Study of Chronic Pelvic Pain (Trans-MAPP) Epidemiology and Phenotyping study. Patients and methods Participants completed a flare survey that asked them: 1) whether they had ever had flares (“symptoms that are much worse than usual”) that lasted <1 hr, >1 hr and <1 day, and >1 day; and 2) for each duration of flare, to report their: a) average length and frequency; b) typical levels of urologic and pelvic pain symptoms; and c) levels of health-care utilization and bother. We compared participants' responses to their non-flare Trans-MAPP values and across flares using generalized linear mixed models. Results Seventy six of 85 participants (89.4%) completed the flare survey, 72 of whom reported having flares (94.7%). Flares varied widely in terms of their duration (seconds to months), frequency (several times per day to once per year or less), and intensity and type of symptoms (e.g., pelvic pain versus urologic symptoms). Flares of all duration were associated with greater pelvic pain, urologic symptoms, disruption to participants' activities, and bother, with increasing severity of each of these factors as the duration of flares increased. Days-long flares were also associated with greater health-care utilization. In addition to duration, symptoms (pelvic pain, in particular) were also significant determinants of flare-related bother. Conclusions Our findings suggest that flares are common and associated with greater symptoms, health-care utilization, disruption, and bother. Our findings also inform the characteristics of flares most bothersome to patients (i.e., increased pelvic pain and duration), and thus of greatest importance to

  10. Fast spectrophotometry of the flare star EV lacertae

    NASA Astrophysics Data System (ADS)

    Zhilyaev, B. E.; Andreev, M. V.; Sergeev, A. V.; Reshetnik, V. N.; Parakhin, N. A.

    2012-12-01

    We present the results of fast spectrophotometry for two flares on EV Lac with a time resolution of 8 s and a spectroscopic resolution R ˜ 100. The observations were performed in May and August 2010 with a slitless spectrograph on the Zeiss-600 telescope at Peak Terskol. We have estimated the UBVR magnitudes from spectrograms through a mathematical convolution of the spectra with the filter transmission curves. The UBV R amplitudes of the August 10, 2010 flare are 2\\underset{raise0.3emsmashriptscriptstyle\\cdot}{m} 83, 1\\underset{raise0.3emsmashriptscriptstyle\\cdot}{m} 94, 0\\underset{raise0.3emsmashriptscriptstyle\\cdot}{m} 82, and 0\\underset{raise0.3emsmashriptscriptstyle\\cdot}{m} 28, respectively. The UBV R amplitudes of the May 30, 2010 flare are 0\\underset{raise0.3emsmashriptscriptstyle\\cdot}{m} 65, 0\\underset{raise0.3emsmashriptscriptstyle\\cdot}{m} 25, 0\\underset{raise0.3emsmashriptscriptstyle\\cdot}{m} 15, and 0\\underset{raise0.3emsmashriptscriptstyle\\cdot}{m} 10, respectively. A detailed colorimetric analysis has allowed important parameters of the flares on EV Lac to be estimated: the temperatures at maximum light and their sizes. The color-color ( U - B)-( B - V ) diagrams confirm that both flares at maximum light radiate as a blackbody. The temperatures at maximum light was 13 400 ± 500 K for the August flare and 5700 ± 100 K for the May flare. During the May flare, an additional hydrogen emission appeared in the Balmer H α, H β, H γ, H δ, H ɛ, H ζ lines and the Balmer continuum (3647 Å) in the spectrum of EV Lac. The excess of emission in the Balmer lines was approximately from two to thirty percent. Based on our colorimetric analysis, we have estimated the linear sizes of the flares at maximum light. The size of the May 30, 2010 flare is approximately 7% of the stellar radius. The size of the August 10, 2010 flare is 3.9% of the stellar radius.

  11. Signatures of Accelerated Electrons in Solar and Stellar Flares

    NASA Astrophysics Data System (ADS)

    Benz, Arnold O.

    2015-08-01

    Flares energize electrons (and ions) to supra-thermal energies. In most cases the final distribution in momentum or energy space is non-Maxwellian. The non-thermal part of the energy can be the source for various emissions, including hard X-rays, synchrotron radiation and coherent radio emission. Such non-thermal emissions may contain information on the acceleration process. Several acceleration scenarios have been proposed: electric DC field, stochastic, and shock acceleration. There is observational evidence for all three scenarios. The new data come from SDO, X-ray (RHESSI), radio observations (Nobeyama, VLA and e-Callisto). Solar energetic particles are an additional channel of information.Tiny solar microflares and huge stellar flares in binary systems (RS CVns) and dMe dwarfs differ by more than 10 orders of magnitude in released energy. Yet the relation between peak luminosity in thermal (soft) X-ray and non-thermal synchrotron (radio) emission is surprisingly constant. This observational fact indicates that flare acceleration scales with energy release over a large range. Electron acceleration in flares seems to be a universal process. The constraint on simultaneous thermal X-rays and non-thermal (radio) synchrotron emission seems to select on particular kind of flare. In this subset, there seems to be only one type of acceleration.Yet, small deviations are noted: Small solar flares are softer in hard X-rays. Solar nanoflares are relatively weak in synchrotron emission. The recently noted case of radio-poor preflares will also be presented. The deviations suggest that the acceleration is less efficient in small flares and in the early phase of flares. Larger deviations are reported occasionally for solar flares and more often from stellar flares, where either thermal or non-thermal emission seems to be missing completely.The location of the acceleration in solar flares remains disputed. Observations suggesting acceleration in the soft X-ray top-tops, above

  12. Laser flare-cell photometry: methodology and clinical applications.

    PubMed

    Ladas, John G; Wheeler, Noel C; Morhun, Patrick J; Rimmer, Steven O; Holland, Gary N

    2005-01-01

    Diagnosis and management of intraocular inflammation involves the assessment of cells and protein levels ("flare") in the aqueous humor. These factors are difficult to quantify precisely on clinical examination alone. Laser flare-cell photometry provides an automated technique to quantify these factors objectively, and it has been used in a variety of research and clinical situations to assess anterior segment inflammation. Any new technique requires evaluation to determine accuracy and reproducibility of measured values, and initial applications require critical appraisal to assess the value of the technique. Both in vitro and in vivo studies of laser flare-cell photometry have been performed to determine its validity and utility as a research and clinical tool. This article reviews published studies that describe the technique of laser flare-cell photometry; it provides new in vitro data that supplements information on the capabilities of this technique and factors that influence photometry results, and it reviews representative publications that have used laser flare-cell photometry for study of specific disease entities. This information can help clinicians and researchers to become familiar with the strengths and limitations of laser flare-cell photometry, to identify appropriate future uses for this technique, and to use it and interpret its results appropriately. Laser flare-cell photometry offers an opportunity to improve upon current techniques of inflammation assessment and should not be considered simply an objective surrogate for clinical grading of cells and flare at the slit-lamp biomicroscope. Its research applications and utility for monitoring patients with uveitis have not yet been fully explored.

  13. Observations and modeling of plasma flows driven by solar flares

    NASA Astrophysics Data System (ADS)

    Brannon, Sean Robert

    One of the fundamental statements that can be made about the solar atmosphere is that it is structured. This structuring is generally believed to be the result of both the arrangement of the magnetic field in the corona and the distribution of plasma along magnetic loops. The standard model of solar flares involves plasma transported into coronal loops via a process known as chromospheric evaporation, and the resulting evolution of the flare loops is believed to be sensitive to the physical mechanism of energy input into the chromosphere by the flare. We present here the results of three investigations into chromospheric plasma flows driven by solar flare energy release and transport. First, we develop a 1-D hydrodynamic code to simulate the response of a simplified model chromosphere to energy input via thermal conduction from reconnection-driven shocks. We use the results from a set of simulations spanning a parameter space in both shock speed and chromospheric-to-coronal temperature ratio to infer power-law relationships between these quantities and observable evaporation properties. Second, we use imaging and spectral observations of a quasi-periodic oscillation of a flare ribbon to determine the phase relationship between Doppler shifts of the ribbon plasma and the oscillation. The phase difference we find leads us to suggest an origin in a current sheet instability. Finally, we use imaging and spectral data of an on-disk flare event and resulting flare loop plasma flows to generally validate the standard picture of flare loop evolution, including evaporation, cooling time, and draining downflows, and we use a simple free-fall model to produce the first direct comparison between observed and synthetic downflow spectra.

  14. Ultrarelativistic electrons and solar flare gamma-radiation

    NASA Technical Reports Server (NTRS)

    Semukhin, P. E.; Kovaltsov, G. A.

    1985-01-01

    Ten solar flares with gamma radiation in excess of 10 MeV were observed. Almost all took place within a heliolatitude greater than 60 deg, close to the solar limb, an indication of the essential anisotropy of high-energy gamma radiation. This high-energy solar flare gamma radiation can be explained by the specific features of the bremsstrahlung of ultrarelativistic electrons trapped within the magnetic arc of the solar atmosphere, even if the acceleration of the electrons is anisotropic.

  15. Effect of a solar flare on a traveling atmospheric disturbance

    NASA Astrophysics Data System (ADS)

    Qian, Liying; Burns, Alan G.; Liu, Hanli; Chamberlin, Phillip C.

    2012-10-01

    It is known that the sudden injection of energy during geomagnetic storms can excite atmospheric gravity waves (AGWs) or traveling atmospheric disturbances (TADs). Together with large-scale circulation, these AGWs/TADs transport energy and momentum away from their sources. In this paper, we investigate possible involvement of AGWs/TADs during solar flares. Model simulations of an X17 flare that occurred on October 28, 2003 shows that AGWs/TADS contributed to flare energy transport from the sunlit South-Pole region to the nightside equatorial region in 3-4 h, resulting in ˜10% nightside equatorial neutral density enhancement in the upper thermosphere. These nightside AGWs/TADs have a phase speed on the order of ˜750 m/s and a horizontal wavelength on the order of 4000 km. Enhanced solar heating to the thermosphere through enhanced ionization during flares occurs on the entire dayside, with the spatial scale of the increased solar heating being too large to excite AGWs/TADs. Further analysis revealed that strong localized enhancement of Joule heating was produced during the October 28, 2003 flare. This sudden injection of the localized heating, together with preexisting AGWs/TADs excited by moderate geomagnetic activity prior to the flare, produced intensified AGWs/TADs, which propagated energy and momentum to the equatorial region. On the other hand, model simulations showed that, under assumed geomagnetically quiet conditions, strong localized enhancement of Joule heating and AGWs/TADs were not produced during the flare. This interplay between geomagnetic activity and solar flares can be a challenge to space weather monitoring, specification, and forecasting.

  16. Fast X-Ray Oscillations during Magnetar Flares

    NASA Technical Reports Server (NTRS)

    Strohmayer Tod E.

    2009-01-01

    The giant flares produced by highly magnetized neutron stars, "magnetars," are the brightest sources of high energy radiation outside our solar system. High frequency oscillations have been discovered during portions of the two most recently observed giant flares which may represent the first detection of global oscillation modes of neutron stars. I will give an observational and theoretical overview of these oscillations and describe how they might allow us to probe neutron star interiors and dense matter physics.

  17. "Magnetar Hyper-Flares: Whole Lotta Shakin' Goin' on"

    NASA Technical Reports Server (NTRS)

    Strohmayer, Tod

    2008-01-01

    The giant flares produced by highly magnetized neutron stars, "magnetars," are the brightest sources of high energy radiation outside our solar system. High frequency oscillations have been discovered during portions of the two most recently observed giant flares which may represent the first detection of global oscillation modes of neutron stars. I will give an observational and theoretical overview of these oscillations and describe how they might allow us to probe neutron star interiors and dense matter physics.

  18. Are Resonant Helioseimic Modes Excited by Solar Flares?

    NASA Astrophysics Data System (ADS)

    Leibacher, John W.; Baudin, Frédéric; Rabello Soares, Maria Cristina

    2016-05-01

    We critically examine reports that flares have been observed to excite resonant p-modes by:-looking in detail at the results of the ring-diagram analysis in terms of duty cycle and center-to-limb variation of ring-diagram power.-applying the same analysis to the Halloween flare using GONG and MDI data.-assessing the stability in terms of oscillation power of both instruments.

  19. On the 'fast electron hypothesis' for stellar flares

    NASA Technical Reports Server (NTRS)

    Mullan, D. J.

    1990-01-01

    It is pointed out that Gurzadyan's (1988) fast-electron hypothesis for stellar flares encounters certain difficulties. The origin of the fast electrons is obscure. Negative flares and predicted ratios of X-ray to optical fluxes are not necessarily a proof of the fast-electron hypothesis. When the electrons thermalize, they will yield X-ray fluxes which are orders of magnitude too large to be consistent with observations.

  20. SHATTERING FLARES DURING CLOSE ENCOUNTERS OF NEUTRON STARS

    SciTech Connect

    Tsang, David

    2013-11-10

    We demonstrate that resonant shattering flares can occur during close passages of neutron stars in eccentric or hyperbolic encounters. We provide updated estimates for the rate of close encounters of compact objects in dense stellar environments, which we find are substantially lower than given in previous works. While such occurrences are rare, we show that shattering flares can provide a strong electromagnetic counterpart to the gravitational wave bursts expected from such encounters, allowing triggered searches for these events to occur.

  1. Solar He-3: Information from nuclear reactions in flares

    NASA Technical Reports Server (NTRS)

    Ramaty, R.; Kozlovsky, B.

    1974-01-01

    Information on solar He-3 from nuclear reactions in flares was considered. Consideration was also given to the development of models for these reactions as well as the abundance of He-3 in the photosphere. Data show that abundances may be explained by nuclear reactions of flare acceleration protons and alpha particles with the ambient atmosphere, provided that various assumptions are made on the directionality of the interacting beams and acceleration of the particles after production.

  2. AD Leonis: Flares observed by XMM-Newton and Chandra

    NASA Astrophysics Data System (ADS)

    van den Besselaar, E. J. M.; Raassen, A. J. J.; Mewe, R.; van der Meer, R. L. J.; Güdel, M.; Audard, M.

    2003-12-01

    The M-dwarf AD Leonis has been observed with the Reflection Grating Spectrometers and the European Photon Imaging Camera aboard XMM-Newton and also with the Low Energy Transmission Grating Spectrometer aboard the Chandra X-ray Observatory. In the observation taken with XMM-Newton five large flares produced by AD Leo were identified and only one in the observation taken with Chandra. A quiescent level to the lightcurves is difficult to define, since several smaller flares mutually overlap each other. However, we defined a quasi-steady state outside of obvious flares or flare decays. The spectra from the flare state and the quasi-steady state are analysed separately. From these spectra the temperature structure was derived with a multi-temperature model and with a differential emission measure model. The multi-temperature model was also used to determine the relative abundances of \\element{C}, \\element{N}, \\element{O}, \\element{Ne}, \\element{Mg}, \\element{Si}, \\element{S}, and \\element{Fe}. \\element{He}-like ions, such as O Vii and Ne Ix, produce line triplets which are used to determine or constrain the electron temperature and electron density of the corresponding ion. During the flare state a higher emission measure at the hottest temperature is found for both XMM-Newton and Chandra observations. The derived abundances suggest the presence of an inverse First Ionization Potential effect in the corona of AD Leo.

  3. JITTER RADIATION MODEL OF THE CRAB GAMMA-RAY FLARES

    SciTech Connect

    Teraki, Yuto; Takahara, Fumio

    2013-02-15

    The gamma-ray flares of the Crab nebula detected by the Fermi and AGILE satellites challenge our understanding of the physics of pulsars and their nebulae. The central problem is that the peak energy of the flares exceeds the maximum energy E {sub c} determined by synchrotron radiation loss. However, when turbulent magnetic fields exist with scales {lambda}{sub B} smaller than 2{pi}mc {sup 2}/eB, jitter radiation can emit photons with energies higher than E {sub c}. The scale required for the Crab flares is about two orders of magnitude less than the wavelength of the striped wind. We discuss a model in which the flares are triggered by plunging the high-density blobs into the termination shock. The observed hard spectral shape may be explained by the jitter mechanism. We make three observational predictions: first, the polarization degree will become lower in flares; second, no counterpart will be seen in TeV-PeV range; and third, the flare spectrum will not be harder than {nu}F {sub {nu}}{proportional_to}{nu}{sup 1}.

  4. Explosive Chromospheric Evaporation in a Circular-ribbon Flare

    NASA Astrophysics Data System (ADS)

    Zhang, Q. M.; Li, D.; Ning, Z. J.; Su, Y. N.; Ji, H. S.; Guo, Y.

    2016-08-01

    In this paper, we report our multiwavelength observations of the C4.2 circular-ribbon flare in active region (AR) 12434 on 2015 October 16. The short-lived flare was associated with positive magnetic polarities and a negative polarity inside, as revealed by the photospheric line-of-sight magnetograms. Such a magnetic pattern is strongly indicative of a magnetic null point and spine-fan configuration in the corona. The flare was triggered by the eruption of a mini-filament residing in the AR, which produced the inner flare ribbon (IFR) and the southern part of a closed circular flare ribbon (CFR). When the eruptive filament reached the null point, it triggered null point magnetic reconnection with the ambient open field and generated the bright CFR and a blowout jet. Raster observations of the Interface Region Imaging Spectrograph show plasma upflow at speeds of 35-120 km s-1 in the Fe xxi λ1354.09 line ({log}T≈ 7.05) and downflow at speeds of 10-60 km s-1 in the Si iv λ1393.77 line ({log}T≈ 4.8) at certain locations of the CFR and IFR during the impulsive phase of the flare, indicating explosive chromospheric evaporation. Coincidence of the single hard X-ray source at 12-25 keV with the IFR and calculation based on the thick-target model suggest that the explosive evaporation was most probably driven by nonthermal electrons.

  5. Statistics of Multi-Wavelength Solar Flare Observations

    NASA Astrophysics Data System (ADS)

    Milligan, Ryan O.

    2016-05-01

    Our current fleet of space-based solar observatories offer us a wealth of opportunities to study solar flares over a range of wavelengths, and the greatest advances in our understanding of flare physics often come from coordinated observations between different instruments. However, despite considerable effort to try and coordinate this armada of instruments over the years (e.g. through the Max Millennium Program of Solar Flare Research), there are frustratingly few solar flares that have been well and truly observed by most or all instruments simultaneously. This is due to a range of factors such as instruments having a limited field of view, satellites in low-Earth orbit going into eclipse, and observing schedules being uploaded days in advance. I shall describe a new technique to retrospectively search archival databases for flares jointly observed by RHESSI, SDO/EVE, Hinode/EIS+SOT, and IRIS. I shall also present a summary of how many flares have been observed by different configurations of these instruments since the launch of SDO.

  6. Microwave Type III Pair Bursts in Solar Flares

    NASA Astrophysics Data System (ADS)

    Tan, Baolin; Mészárosová, Hana; Karlický, Marian; Huang, Guangli; Tan, Chengming

    2016-03-01

    A solar microwave type III pair burst is composed of normal and reverse-sloped (RS) burst branches with oppositely fast frequency drifts. It is the most sensitive signature of the primary energy release and electron accelerations in flares. This work reports 11 microwave type III pair events in 9 flares observed by radio spectrometers in China and the Czech Republic at a frequency of 0.80-7.60 GHz during 1994-2014. These type III pairs occurred in flare impulsive and postflare phases with separate frequencies in the range of 1.08-3.42 GHz and a frequency gap of 10-1700 MHz. The frequency drift increases with the separate frequency (fx), the lifetime of each burst is anti-correlated to fx, while the frequency gap is independent of fx. In most events, the normal branches are drifting obviously faster than the RS branches. The type III pairs occurring in flare impulsive phase have lower separate frequencies, longer lifetimes, wider frequency gaps, and slower frequency drifts than that occurring in postflare phase. Also, the latter always has strong circular polarization. Further analysis indicates that near the flare energy release sites the plasma density is about {10}10{--}{10}11 cm-3 and the temperature is higher than 107 K. These results provide new constraints to the acceleration mechanism in solar flares.

  7. Solar flares and avalanches in driven dissipative systems

    NASA Technical Reports Server (NTRS)

    Lu, Edward T.; Hamilton, Russell J.; Mctiernan, J. M.; Bromund, Kenneth R.

    1993-01-01

    The contention of Lu and Hamilton (1991) that the energy release process in solar flares can be understood as avalanches of many small reconnection events is further developed. The dynamics of the complex magnetized plasma of solar active regions is modeled with a simple driven dissipative system, consisting of a vector field with local instabilities that cause rapid diffusion of the field. It is argued that the avalanches in this model are analogous to solar flares. The distributions of avalanches in this model are compared with the solar flare frequency distributions obtained from ISEE 3/ICE satellite observations. Quantitative agreement is found with the energy, peak luminosity, and duration distributions over four orders of magnitude in flare energy, from the largest flares down to the completeness limit of the observations. It is predicted that the power-law solar flare frequency distributions will be found to continue downward with the same logarithmic slopes to an energy of about 3 x 10 exp 25 ergs and duration of about 0.3 s, with deviations from power-law behavior below these values.

  8. Observations of a Two Ribbon White Light Flare

    NASA Astrophysics Data System (ADS)

    Li, J.; Mickey, D.; LaBonte, B.

    2003-05-01

    On July 15 2002, an X3 flare occured within AR10030 and it was accompanied with a white light flare (WLF). The Imaging Vector Magnetograph (IVM) at Mees Solar Observatory recorded the entire event including several hours of data before and after the flare. The IVM continuum images are taken at time cadence as high as 1 seconds per image. Such observations enabled us to resolve the WLF patches in time and space. We will present (1). the initial WLF patch fell on a small sunspot located at an area surrounded with single relatively weak magnetic polarity between proceeding and following sunspot groups; (2) the energy deposited during the WLF flare; (3) the light curves of the optical continuum, the UV continuum (TRACE/1600) and microwaves (1.2 - 18 GHz from Oven's Valley Solar Array). They demonstrate the same profiles during flare impulsive phase. The observations suggest that the origin of the WLF flare was caused by accelerated particles precipitate into lower atmosphere along magnetic field lines. This work is supported by NASA grant to Mess Solar Observatory and MURI program.

  9. Comparing Dynamics in Eruptive and Non-Eruptive Flares

    NASA Astrophysics Data System (ADS)

    Nitta, Nariaki; Tarbell, Theodore D.; Slater, Gregory L.; Frank, Zoe Anne

    2016-05-01

    Close comparison of EUV and coronagraph data suggests that there may not be clear distinction between eruptive and non-eruptive flares as far as the coronal and chromospheric signatures are concerned. Here we define eruptive and non-eruptive flares in terms of the presence and absence of the associated coronal mass ejection (CME). We have studied several flares in both categories using Hinode/SOT and IRIS data. The pointing of the Hinode/SOT data has been updated by correlating them with AIA 1700 A images. We show our initial results about how the flare development compares in eruptive and non-eruptive flares, including the reconnection rate as derived from the magnetic field swept over by flare ribbons (in SOT Ca images), and the line-of-sight velocities at different locations and temperatures (in IRIS spectral data). We also discuss large-scale disturbances and related CMEs in SDO/AIA and SOHO/LASCO data as context information.

  10. TRANSITION REGION EMISSION FROM SOLAR FLARES DURING THE IMPULSIVE PHASE

    SciTech Connect

    Johnson, H.; Raymond, J. C.; Murphy, N. A.; Suleiman, R.; Giordano, S.; Ko, Y.-K.; Ciaravella, A.

    2011-07-10

    There are relatively few observations of UV emission during the impulsive phases of solar flares, so the nature of that emission is poorly known. Photons produced by solar flares can resonantly scatter off atoms and ions in the corona. Based on off-limb measurements by the Solar and Heliospheric Observatory/Ultraviolet Coronagraph Spectrometer, we derive the O VI {lambda}1032 luminosities for 29 flares during the impulsive phase and the Ly{alpha} luminosities of 5 flares, and we compare them with X-ray luminosities from GOES measurements. The upper transition region and lower transition region luminosities of the events observed are comparable. They are also comparable to the luminosity of the X-ray emitting gas at the beginning of the flare, but after 10-15 minutes the X-ray luminosity usually dominates. In some cases, we can use Doppler dimming to estimate flow speeds of the O VI emitting gas, and five events show speeds in the 40-80 km s{sup -1} range. The O VI emission could originate in gas evaporating to fill the X-ray flare loops, in heated chromospheric gas at the footpoints, or in heated prominence material in the coronal mass ejection. All three sources may contribute in different events or even in a single event, and the relative timing of UV and X-ray brightness peaks, the flow speeds, and the total O VI luminosity favor each source in one or more events.

  11. FINE STRUCTURE OF FLARE RIBBONS AND EVOLUTION OF ELECTRIC CURRENTS

    SciTech Connect

    Sharykin, I. N.; Kosovichev, A. G.

    2014-06-10

    Emission of solar flares across the electromagnetic spectrum is often observed in the form of two expanding ribbons. The standard flare model explains flare ribbons as footpoints of magnetic arcades, emitting due to interaction of energetic particles with the chromospheric plasma. However, the physics of this interaction and properties of the accelerated particles are still unknown. We present results of multiwavelength observations of the C2.1 flare of 2013 August 15, observed with the New Solar Telescope of the Big Bear Solar Observatory, and the Solar Dynamics Observatory, GOES, and Fermi spacecraft. The observations reveal previously unresolved sub-arcsecond structure of flare ribbons in regions of strong magnetic field consisting from numerous small-scale bright knots. We observe a red-blue asymmetry of H{sub α} flare ribbons with a width as small as ∼100 km. We discuss the relationship between the ribbons and vertical electric currents estimated from vector magnetograms, and show that Joule heating can be responsible for energization of H{sub α} knots in the ribbons.

  12. Epidermal injury promotes nephritis flare in lupus-prone mice.

    PubMed

    Clark, Kaitlyn L; Reed, Tamra J; Wolf, Sonya J; Lowe, Lori; Hodgin, Jeffrey B; Kahlenberg, J Michelle

    2015-12-01

    Systemic lupus erythematosus is clinically characterized by episodes of flare and remission. In patients, cutaneous exposure to ultraviolet light has been proposed as a flare trigger. However, induction of flare secondary to cutaneous exposure has been difficult to emulate in many murine lupus models. Here, we describe a system in which epidermal injury is able to trigger the development of a lupus nephritis flare in New Zealand Mixed (NZM) 2328 mice. 20-week old NZM2328 female mice underwent removal of the stratum corneum via duct tape, which resulted in rapid onset of proteinuria and death when compared to sham-stripped littermate control NZM2328 mice. This was coupled with a drop in serum C3 concentrations and dsDNA antibody levels and enhanced immune complex deposition in the glomeruli. Recruitment of CD11b(+)CD11c(+)F4/80(high) macrophages and CD11b(+)CD11c(+)F4/80(low) dendritic cells was noted prior to the onset of proteinuria in injured mice. Transcriptional changes within the kidney suggest a burst of type I IFN-mediated and inflammatory signaling which is followed by upregulation of CXCL13 following epidermal injury. Thus, we propose that tape stripping of lupus-prone NZM2328 mice is a novel model of lupus flare induction that will allow for the study of the role of cutaneous inflammation in lupus development and how crosstalk between dermal and systemic immune systems can lead to lupus flare.

  13. Stress as a trigger of disease flares in SLE.

    PubMed

    Roussou, E; Iacovou, C; Weerakoon, A; Ahmed, K

    2013-05-01

    Patients with systemic lupus erythematosus were asked to report their perceptions as to whether stress can trigger disease flares. A total of 54 patients treated at two District General Hospitals in Essex were included in the analysis. They were 4 males and 50 females and were 20 Caucasians, 22 Asians, and 12 Africans/Afro-Caribbean. Thirty-three of 54 patients (61.1%) reported stress to be a trigger for disease flares. Although most (85%) of the Caucasian patients reported that stress triggered their disease flares, only 50% of the African/Afro-Caribbean patients and 45.4% of the Asian patients reported stress as a trigger for disease flares. No correlation was found between reported number of flares per year and characteristics such as age (P = 0.4), age at diagnosis (P = 0.8), age at disease onset (P = 0.6), or disease duration (P = 0.2). A trend towards a significant correlation was observed between the number of reported flares per year and the number of children a patient has (P = 0.07).

  14. ANATOMY OF A SOLAR FLARE: MEASUREMENTS OF THE 2006 DECEMBER 14 X-CLASS FLARE WITH GONG, HINODE, AND RHESSI

    SciTech Connect

    Matthews, S. A.; Zharkov, S.; Zharkova, V. V.

    2011-10-01

    Some of the most challenging observations to explain in the context of existing flare models are those related to the lower atmosphere and below the solar surface. Such observations, including changes in the photospheric magnetic field and seismic emission, indicate the poorly understood connections between energy release in the corona and its impact in the photosphere and the solar interior. Using data from Hinode, TRACE, RHESSI, and GONG we study the temporal and spatial evolution of the 2006 December 14 X-class flare in the chromosphere, photosphere, and the solar interior. We investigate the connections between the emission at various atmospheric depths, including acoustic signatures obtained by time-distance and holography methods from the GONG data. We report the horizontal displacements observed in the photosphere linked to the timing and locations of the acoustic signatures we believe to be associated with this flare, their vertical and horizontal displacement velocities, and their potential implications for current models of flare dynamics.

  15. THE 2014 MARCH 29 X-FLARE: SUBARCSECOND RESOLUTION OBSERVATIONS OF Fe XXI λ1354.1

    SciTech Connect

    Young, Peter R.; Tian, Hui; Jaeggli, Sarah

    2015-02-01

    The Interface Region Imaging Spectrometer (IRIS) is the first solar instrument to observe ∼10 MK plasma at subarcsecond spatial resolution through imaging spectroscopy of the Fe XXI λ1354.1 forbidden line. IRIS observations of the X1 class flare that occurred on 2014 March 29 at 17:48 UT reveal Fe XXI emission from both the flare ribbons and the post-flare loop arcade. Fe XXI appears at all of the chromospheric ribbon sites, although typically with a delay of one raster (75 s) and sometimes offset by up to 1''. 100-200 km s{sup –1} blue-shifts are found at the brightest ribbons, suggesting hot plasma upflow into the corona. The Fe XXI ribbon emission is compact with a spatial extent of <2'', and can extend beyond the chromospheric ribbon locations. Examples are found of both decreasing and increasing blue-shift in the direction away from the ribbon locations, and blue-shifts were present for at least six minutes after the flare peak. The post-flare loop arcade, seen in Atmospheric Imaging Assembly 131 Å filtergram images that are dominated by Fe XXI, exhibited bright loop-tops with an asymmetric intensity distribution. The sizes of the loop-tops are resolved by IRIS at ≥1'', and line widths in the loop-tops are not broader than in the loop-legs suggesting the loop-tops are not sites of enhanced turbulence. Line-of-sight speeds in the loop arcade are typically <10 km s{sup –1}, and mean non-thermal motions fall from 43 km s{sup –1} at the flare peak to 26 km s{sup –1} six minutes later. If the average velocity in the loop arcade is assumed to be at rest, then it implies a new reference wavelength for the Fe XXI line of 1354.106 ± 0.023 Å.

  16. DETERMINING HEATING RATES IN RECONNECTION FORMED FLARE LOOPS OF THE M8.0 FLARE ON 2005 MAY 13

    SciTech Connect

    Liu Wenjuan; Qiu Jiong; Longcope, Dana W.; Caspi, Amir

    2013-06-20

    We analyze and model an M8.0 flare on 2005 May 13 observed by the Transition Region and Coronal Explorer and the Reuven Ramaty High Energy Solar Spectroscopic Imager (RHESSI) to determine the energy release rate from magnetic reconnection that forms and heats numerous flare loops. The flare exhibits two ribbons in UV 1600 A emission. Analysis shows that the UV light curve at each flaring pixel rises impulsively within a few minutes, and decays slowly with a timescale longer than 10 minutes. Since the lower atmosphere (the transition region and chromosphere) responds to energy deposit nearly instantaneously, the rapid UV brightening is thought to reflect the energy release process in the newly formed flare loop rooted at the footpoint. In this paper, we utilize the spatially resolved (down to 1'') UV light curves and the thick-target hard X-ray emission to construct heating functions of a few thousand flare loops anchored at the UV footpoints, and compute plasma evolution in these loops using the enthalpy-based thermal evolution of loops model. The modeled coronal temperatures and densities of these flare loops are then used to calculate coronal radiation. The computed soft X-ray spectra and light curves compare favorably with those observed by RHESSI and by the Geostationary Operational Environmental Satellite X-ray Sensor. The time-dependent transition region differential emission measure for each loop during its decay phase is also computed with a simplified model and used to calculate the optically thin C IV line emission, which dominates the UV 1600 A bandpass during the flare. The computed C IV line emission decays at the same rate as observed. This study presents a method to constrain heating of reconnection-formed flare loops using all available observables independently, and provides insight into the physics of energy release and plasma heating during the flare. With this method, the lower limit of the total energy used to heat the flare loops in this event

  17. Spontaneous formation of electric current sheets and the origin of solar flares

    NASA Technical Reports Server (NTRS)

    Low, B. C.; Wolfson, R.

    1988-01-01

    It is demonstrated that the continuous boundary motion of a sheared magnetic field in a tenuous plasma with an infinite electrical conductivity can induce the formation of multiple electric current sheets in the interior plasma. In response to specific footpoint displacements, the quadrupolar magnetic field considered is shown to require the formation of multiple electric current sheets as it achieves a force-free state. Some of the current sheets are found to be of finite length, running along separatrix lines of force which separate lobes of magnetic flux. It is suggested that current sheets in the form of infinitely thin magnetic shear layers may be unstable to resistive tearing, a process which may have application to solar flares.

  18. A complete spectral analysis of the flare of the quasar 3C 273

    NASA Technical Reports Server (NTRS)

    Sadun, Alberto C.

    1992-01-01

    The 1983 quasar outburst of the source 3C 273 is investigated by studying several months of radio-frequency and UV data that represent about six decades of frequency. The data are analyzed to account for the differences inherent in various photometric systems, and adjustments are made for reddening and line emission. Individual wavelengths are delineated in light curves which indicate distinct periods of burst activity for specific wavelengths. The spectrum of the flare is characterized by a trend in which the critical wavelength evolves toward longer wavelengths as the outburst progresses. It is suggested that the data are consistent with a model of an expanding gas cloud that emits Doppler-boosted synchrotron radiation. The spectral curves, light curves, and the spectral index are of use in the analysis of similar phenomena when VLBI data of superluminal motion are incorporated.

  19. Oilfield Flare Gas Electricity Systems (OFFGASES Project)

    SciTech Connect

    Rachel Henderson; Robert Fickes

    2007-12-31

    The Oilfield Flare Gas Electricity Systems (OFFGASES) project was developed in response to a cooperative agreement offering by the U.S. Department of Energy (DOE) and the National Energy Technology Laboratory (NETL) under Preferred Upstream Management Projects (PUMP III). Project partners included the Interstate Oil and Gas Compact Commission (IOGCC) as lead agency working with the California Energy Commission (CEC) and the California Oil Producers Electric Cooperative (COPE). The project was designed to demonstrate that the entire range of oilfield 'stranded gases' (gas production that can not be delivered to a commercial market because it is poor quality, or the quantity is too small to be economically sold, or there are no pipeline facilities to transport it to market) can be cost-effectively harnessed to make electricity. The utilization of existing, proven distribution generation (DG) technologies to generate electricity was field-tested successfully at four marginal well sites, selected to cover a variety of potential scenarios: high Btu, medium Btu, ultra-low Btu gas, as well as a 'harsh', or high contaminant, gas. Two of the four sites for the OFFGASES project were idle wells that were shut in because of a lack of viable solutions for the stranded noncommercial gas that they produced. Converting stranded gas to useable electrical energy eliminates a waste stream that has potential negative environmental impacts to the oil production operation. The electricity produced will offset that which normally would be purchased from an electric utility, potentially lowering operating costs and extending the economic life of the oil wells. Of the piloted sites, the most promising technologies to handle the range were microturbines that have very low emissions. One recently developed product, the Flex-Microturbine, has the potential to handle the entire range of oilfield gases. It is deployed at an oilfield near Santa Barbara to run on waste gas that is only 4% the

  20. M DWARFS IN SLOAN DIGITAL SKY SURVEY STRIPE 82: PHOTOMETRIC LIGHT CURVES AND FLARE RATE ANALYSIS

    SciTech Connect

    Kowalski, Adam F.; Hawley, Suzanne L.; Hilton, Eric J.; Becker, Andrew C.; Sesar, Branimir; West, Andrew A.; Bochanski, John J.

    2009-08-15

    We present a flare rate analysis of 50,130 M dwarf light curves in Sloan Digital Sky Survey Stripe 82. We identified 271 flares using a customized variability index to search {approx}2.5 million photometric observations for flux increases in the u and g bands. Every image of a flaring observation was examined by eye and with a point-spread function-matching and image subtraction tool to guard against false positives. Flaring is found to be strongly correlated with the appearance of H{alpha} in emission in the quiet spectrum. Of the 99 flare stars that have spectra, we classify eight as relatively inactive. The flaring fraction is found to increase strongly in stars with redder colors during quiescence, which can be attributed to the increasing flare visibility and increasing active fraction for redder stars. The flaring fraction is strongly correlated with |Z| distance such that most stars that flare are within 300 pc of the Galactic plane. We derive flare u-band luminosities and find that the most luminous flares occur on the earlier-type m dwarfs. Our best estimate of the lower limit on the flaring rate (averaged over Stripe 82) for flares with {delta}u {>=} 0.7 mag on stars with u < 22 is 1.3 flares hr{sup -1} deg{sup -2} but can vary significantly with the line of sight.