Sample records for solar flare occurrence

  1. 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. PMID:16486917

  2. Accepted by ApJ. Periodicities in Solar Flare Occurrence

    E-print Network

    Bai, Taeil

    Accepted by ApJ. Periodicities in Solar Flare Occurrence: Analysis of Cycles 19­23 T. Bai Stanford University, Stanford, CA 94305 bai@quake.stanford.edu ABSTRACT Mid-range periodicities in solar flare spectra of major flare occurrence times for the time intervals analyzed by Ozguc & Atac and Bai, strongest

  3. What flare and CME parameters control the occurrence of solar proton events?

    NASA Astrophysics Data System (ADS)

    Park, Jinhye; Moon, Y.-J.

    2014-12-01

    In this study we examine the occurrence probabilities of solar proton events (SPEs) and their peak fluxes depending on both flare and coronal mass ejection (CME) parameters: flare peak flux, longitude, impulsive time, CME linear speed, and angular width. For this we use the NOAA SPEs, their associated X-ray flares, and CME from 1997 to 2011. We divide the data into 16 subgroups according to the flare and CME parameters and estimate the SPE probabilities for the subgroups. The three highest probabilities are found for the following subgroups: (1) fast full halo (55.3%) and fast partial halo (42.9%) CMEs associated with strong flares from the western region and (2) slow full halo CMEs associated with strong flares from the western region (31.6%). It is noted that the events whose SPE probabilities are nearly 0% belong to the following subgroups: (1) slow and fast partial halo CMEs from the eastern region, (2) slow partial halo CMEs from the western region, and (3) slow full halo CMEs from the eastern region. These results show that important parameters to control SPE occurrences are CME linear speed, angular width, and source longitude, which can be understood by the piston-driven shock formation of fast CMEs and magnetic field connectivity from the source site to the Earth. It is also shown that when the subgroups are separately considered by flare impulsive time and source longitude, the correlation coefficients between the observed and the predicted SPE peak fluxes are greatly improved.

  4. 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.

  5. Solar Flares

    NASA Technical Reports Server (NTRS)

    Shih, Albert

    2011-01-01

    Solar flares accelerate both ions and electrons to high energies, and their X-ray and gamma-ray signatures not only probe the relationship between their respective acceleration, but also allow for the measurement of accelerated and ambient abundances. RHESSI observations have shown a striking close linear correlation of gamma-ray line fluence from accelerated ions > approx.20 MeV and bremsstrahlung emission from relativistic accelerated electrons >300 keV, when integrated over complete flares, suggesting a common acceleration mechanism. SMM/GRS observations, however, show a weaker correlation, and this discrepancy might be associated with previously observed electron-rich episodes within flares and/or temporal variability of gamma-ray line fluxes over the course of flares. We use the latest RHESSI gamma-ray analysis techniques to study the temporal behavior of the RHESSI flares, and determine what changes can be attributed to an evolving acceleration mechanism or to evolving abundances.

  6. Solar Flares

    NASA Astrophysics Data System (ADS)

    Rust, David

    1998-01-01

    The Sun is constantly changing. Not an hour goes by without a rise or fall in solar x-radiation or radio emission. Not a day goes by without a solar flare. Our active star, this inconsistent Sun, this gaseous cloud that blows in all directions, warms the air we breathe and nourishes the food we eat. From Earth, it seems the very model of stability, but in space it often creates havoc. Over the past century, solar physicists have learned how to detect even the weakest of solar outbursts or flares. We know that flares must surely trace their origins to the magnetic strands stretched and tangled by the rolling plasma of the solar interior. Although a century of astrophysical research has produced widely accepted, fundamental understanding about the Sun, we have yet to predict successfully the emergence of any magnetic fields from inside the Sun or the ignition of any flare. As in any physical experiment, the ability to predict events not only validates the scientific ideas, it also has practical value. In astrophysics, a demonstrated understanding of sunspots, flares, and ejections of plasma would allow us to approach many other mysteries, such as stellar X-ray bursters, with tested theories.

  7. Asymmetric Statistical Properties of the Solar Cycle 23 Deduced from Sunspots, Plages and Flare Occurrences

    Microsoft Academic Search

    Valentina Zharkova; S. Zharkov

    2006-01-01

    The statistical properties of sunspot, active regions (plages) and filament distributions obtained from the automated Solar Feature Catalogues (SFC, http:\\/\\/solar.inf.brad.ac.uk) and their relation to flare distributions are presented for 1996-2005. We present distributions of sunspot numbers with given areas for different phases and the whole solar cycle 23. Statistical sunspot and plage area distributions revealed a strong North-South asymmetry of

  8. Intensity thresholds and the statistics of the temporal occurrence of solar flares.

    PubMed

    Baiesi, Marco; Paczuski, Maya; Stella, Attilio L

    2006-02-10

    Introducing thresholds to analyze time series of emission from the Sun enables a new and simple definition of solar flare events and their interoccurrence times. Rescaling time by the rate of events, the waiting and quiet time distributions both conform to scaling functions that are independent of the intensity threshold over a wide range. The scaling functions are well-described by a two-parameter function, with parameters that depend on the phase of the solar cycle. For flares identified according to the current, standard definition, similar behavior is found. PMID:16486918

  9. Occurrence of solar flares viewed with GPS: Statistics and fractal nature

    NASA Astrophysics Data System (ADS)

    Monte-Moreno, Enrique; Hernández-Pajares, Manuel

    2014-11-01

    In this paper we describe the statistical properties of the EUV solar flux sudden variation. The solar flux variation is modeled as a time series characterized by the subsolar Vertical Total Electron Content double difference in time, computed with dual-frequency GNSS (Global Navigation Satellite Systems) measurements in the daylight hemisphere (GNSS solar flare indicator rate parameter). We propose a model that explains its characteristics and the forecasting limitations. The sudden overionization pattern is assumed to be of solar origin, and the data used in this study was collected during the last solar cycle. The two defining characteristics of this time series are an extreme variability (i.e., in a solar cycle one can find events at 400? from the mean value) and a temporal correlation that is independent of the timescale. We give a characterization of a model that explains the empirical results and properties such as (a) the persistence and presence of bursts of solar flares and (b) their long tail peak values of the solar flux variation. We show that the solar flux variation time series can be characterized by a fractional Brownian model for the long-term dependence, and a power law distribution for the extreme values that appear in the time series.

  10. How Solar Flares Work

    Microsoft Academic Search

    Hugh S. Hudson

    2008-01-01

    Geophysics, radio astronomy, Japan, the ionosphere, X and gamma rays: all have contributed to my view of how solar flares and their partner coronal mass ejections (CMEs) work. A solar flare (and a CME, it turns out) has an \\

  11. Solar Flare Theory

    NSDL National Science Digital Library

    Holman, Gordon D.

    This site from NASA's Goddard Space Flight Center offers information related to solar flares. It discusses what a solar flare is, why they are important, and the study of solar flares in hard x-ray. There are many pictures, animations and links to other sites. Activities that may be used in the classroom are also included.

  12. 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.

  13. The solar flare myth

    Microsoft Academic Search

    J. T. Gosling

    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 paradigm of cause and effect - that large solar flares are the fundamental cause of these events in the near-Earth

  14. 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.

  15. 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.

  16. 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.

  17. The physics of solar flares

    NASA Technical Reports Server (NTRS)

    Tandberg-Hanssen, Einar; Emslie, A. Gordon

    1988-01-01

    Solar flare phenomena are examined in an introduction for advanced undergraduate and graduate physics students. Chapters are devoted to the history of observations, flare spectroscopy, flare magnetohydrodynamics, flare plasma physics, radiative processes in the solar plasma, preflare conditions, the impulsive phase, the gradual phase, and coronal mass ejections. Diagrams, graphs, and photographs are provided.

  18. Parameterization of solar flare dose 

    E-print Network

    Lamarche, Anne Helene

    1995-01-01

    A critical aspect of missions to the Moon or Mars is 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 ...

  19. Solar Flares and particle acceleration

    E-print Network

    Solar Flares and particle acceleration Eduard Kontar School of Physics and Astronomy University and accelerated particles #12;Solar flares and accelerated particles From Emslie et al., 2004, 2005 Free magnetic Spectroscopic Imager RHESSI is designed to investigate particle acceleration and energy release in solar flares

  20. 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.

  1. Lithium-6 from Solar Flares

    E-print Network

    R. Ramaty; V. Tatischeff; J. P. Thibaud; B. Kozlovsky; N. Mandzhavidze

    2000-03-23

    By introducing a hitherto ignored Li-6 producing process, due to accelerated He-3 reactions with He-4, we show that accelerated particle interactions in solar flares produce much more Li-6 than Li-7. By normalizing our calculations to gamma-ray data we demonstrate that the Li-6 produced in solar flares, combined with photospheric Li-7, 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.

  2. 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. PMID:10813684

  3. Nuclear processes in solar flares

    NASA Technical Reports Server (NTRS)

    Ramaty, R.

    1982-01-01

    The theory of solar gamma-ray line production is reviewed and new calculations of line production yields are presented. Observations, carried out with gamma-ray spectrometers on OSO-7, HEAO-1, HEAO-3 and SMM are reviewed and compared with theory. These observations provide direct evidence for nuclear reactions in flares and furnish unique information on particle acceleration and flare mechanisms.

  4. RT-2 observations of Solar flares

    NASA Astrophysics Data System (ADS)

    Chakrabarti, Sandip Kumar; Rao, A. R.; Agrawal, V. K.; Nandi, Anuj; Debnath, D.; Kotoch, T. B.; Sreekumar, S.; Kotov, Yury; Arkhangelsky, Andrey; Buslov, A. S.; Oreshnikov, E. M.; Yurov, Vitaly; Tyshkevich, V.; Manoharan, P. K.; Shaheda Begum, S.

    The RT-2 detectors onboard the Coronas-Photon satellite have detected several solar flares from February to November 2009. RT-2 includes a pair of low background Phoswich scientillation detectors of good sensitivity and provides a good opportunity to study faint solar hard X-ray flares during the solar minimum. We present the detection of Quasi-Periodic Pulsations in a solar flare and also provide an estimate of the number distribution of solar flares during the solar minimum.

  5. Seismic Emission From Solar Flares

    NASA Astrophysics Data System (ADS)

    Lindsey, C. A.; Donea, A.

    2005-05-01

    Local helioseismic diagnostics applied to helioseismic observations from the Michelson Doppler Imager (MDI) on the Solar Heliospheric Observatory (SOHO) have shown the clear signature of seismic emission from three flares during the advent of SOHO. All three of these flares showed the signatures of ?-ray emission indicating the involvement of accelerated protons. Two of the acoustically active flares were recent, October 28 and 29 of 2003, and were observed by RHESSI. In both of these instances, the sources of the acoustic emission acoustic source, determined by computational seismic holography, coincided closely with compact ? -ray signatures of protons. Elementary considerations ofenergy and momentum transfer appear to make chromospheric and photospheric heating by protons favorable for seismic emission from flares. If this is actually the case, proton diagnostics of flares from RHESSI would be useful for identifying acoustically active flares for the Helioseismic Magnetic Imager (HMI) on the Solar Dynamics Observatory (SDO), and possibly for the SOHO/MDI. Given a clear understanding of the effects of flares on Doppler signatures in active regions, acoustic emission from flares can give us a powerful control utility for seismic diagnostics of active regions subphotospheres. This research has benefitted greatly from the keen insights of Valentina Zharkova, Gerald Share, Hugh Hudson, and Sam Krucker. It has been supported by grants from the Living with a Star and Supporting Research and Technology programs of the National Aeronautics and Space Administration and the Stellar Astronomy and Astrophysics branch of the National Science Foundation.

  6. 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. PMID:10859129

  7. Flares and dynamic aspects. [solar physics

    NASA Technical Reports Server (NTRS)

    Hanssen, E. T.

    1981-01-01

    Theory of the dynamic nature of solar flares, eruptive prominences, and coronal transients is surveyed. Two types of flare are considered: compact eruptions (small flares) which are probably loops, and large eruptions of double filament flares. The physical sense of this classification is justified, using solar observations. Even leaving the question unanswered of whether a coronal transient is a loop of ejected matter or a shock wave, the important, perhaps fundamental, role of mass motion in flare physics is evidenced.

  8. Parameterization of solar flare dose

    E-print Network

    Lamarche, Anne Helene

    1995-01-01

    of the proton transport through a given shield to obtain the dose to astronauts, the Baryon transport code, BRYNTRN, will be used. This code, developed at NASA Langley Research Center, can be used to solve the fundamental Boltzmann transport equation... at another part of the solar system. NASA's Solar Maximum Mission (SMM) answered many questions about proton acceleration sites (Chupp, 1987). Since proton storms generally outlast flares by many hours, it seems unclear whether they originate in similarly...

  9. Detecting Solar Neutrino Flares and Flavors

    E-print Network

    D. Fargion

    2004-04-16

    Intense solar flares originated in sun spots produce high energy particles (protons, $\\alpha$) well observable by satellites and ground-based detectors. The flare onset produces signals in different energy bands (radio, X, gamma and neutrons). The most powerful solar flares as the ones occurred on 23 February 1956, 29 September 1989 and the more recent on October 28th, and the 2nd, 4th, 13th of November 2003 released in sharp times the largest flare energies (${E}_{FL} \\simeq {10}^{31}\\div {10}^{32} erg). The high energy solar flare protons scatter within the solar corona and they must be source of a prompt neutrino burst through the production of charged pions. Later on, solar flare particles hitting the atmosphere may marginally increase the atmospheric neutrino flux. The prompt solar neutrino flare may be detected in the largest underground $\

  10. Solar flares and energetic particles.

    PubMed

    Vilmer, Nicole

    2012-07-13

    Solar flares are now observed at all wavelengths from ?-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 ?-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/?-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. PMID:22665901

  11. Solar flares at submillimeter wavelengths

    NASA Astrophysics Data System (ADS)

    Trottet, Gérard; Kaufmann, Pierre; Lüthi, Thomas; Guillermo Guiménez de Castro, C.; Raulin, Jean-Pierre; Marun, Adolfo; Klein, Karl-Ludwig

    2010-05-01

    The presence of a new solar burst spectral component with flux density increasing with frequency above 200 GHz, spectrally different from the well-known microwave component, has been recently revealed by observations made at 212 and 405 GHz by the Solar Submillimeter Telescope and at 210, 230 and 345 GHz with the telescope of the Köln Observatory for Submillimeter and Millimeter Astronomy. Such unprecedented observations bring new possibilities to explore particle acceleration and energy transport processes during a flare, both observationally and theoretically. In this presentation we give a brief overview of submillimeter and joint microwave and X-ray-gamma-ray observations obtained so far. Possible mechanisms to explain the double spectral components at microwaves and in the submillimeter domain are discussed. We finally emphasize the need of observations at shorter wavelengths, in particular in the far infrared domain, to fully benefit from these new diagnostics of the flaring processes.

  12. FNAS/solar flare energetics

    NASA Technical Reports Server (NTRS)

    Machado, M. E.

    1992-01-01

    We have performed an extensive study of solar flare energy buildup and release, concentrating in two aspects: (1) relationship with 3D field topology and measured electric currents; and (2) flare onset characteristics as determined from combined x ray and ultraviolet observations. We extended our previous studies on the characteristic topology of flaring regions, by following the evolution of an active region over three consecutive days. From comparison with flare observations in x rays and h alpha, we found further support for the hypothesis that flares were triggered by taking place at the separators (3D generalization of and x-type neutral point). Furthermore, we found that emerging in flux at a site within the active regions where no (or little) activity was previously observed, caused the appearance of a secondary separator and thereon continuous triggering of activity at such site. Our topology arguments were then applied to a study of sympathetic activity between two regions within an active complex. Here again we found that interacting field structures along separators and separatrices, which act as pathways for recurrent flaring to spread between the regions, could be used to understand how activity spread to potentially explosive sites with the complex. We also finished our study of flare onset characteristics as determined from combined x ray and ultraviolet observations. Using a quasi-static modeling approach, we find that this phase is characterized by a relatively low level of energy release, 10 exp 26-27 erg/s, which is sufficient to produce 'gentle' evaporation, a shift in the location of the transition zone as compared to pre-flare conditions, and an increase in the temperature and density of coronal loops. All these changes have profound implications on the observed signatures of impulsive phase phenomena, which had been neglected in the past. As a follow-up of this investigation, we now plan to apply our results to the interpretation of high-sensitivity spectroscopic and hard x-ray data currently being gathered by the Yohkoh and Compton Gamma Ray Observatory satellites.

  13. Solar flares induced D-region ionospheric and geomagnetic perturbations

    NASA Astrophysics Data System (ADS)

    Selvakumaran, R.; Maurya, Ajeet K.; Gokani, Sneha A.; Veenadhari, B.; Kumar, Sushil; Venkatesham, K.; Phanikumar, D. V.; Singh, Abhay K.; Siingh, Devendraa; Singh, Rajesh

    2015-02-01

    The D-region ionospheric perturbations caused by solar flares which occurred during January 2010-February 2011, a low solar activity period of current solar cycle 24, have been examined on NWC transmitter signal (19.8 kHz) recorded at an Indian low latitude station, Allahabad (Geographic lat. 25.75°N, long. 81.85°E). A total of 41 solar flares, including 21 C-class, 19 M-class and 01 X-class, occurred during the daylight part of the NWC-Allahabad transmitter receiver great circle path. The local time dependence of solar flare effects on the change in the VLF amplitude, time delay between VLF peak amplitude and X-ray flux peak have been studied during morning, noon and evening periods of local daytime. Using the Long Wave Propagation Capability code V 2.1 the D-region reference height (H/) and sharpness factor (?) for each class of solar flare (C, M and X) have been estimated. It is found that D-region ionospheric parameters (H/, ?) strongly depend on the local time of flare's occurrence and their classes. The flare time electron density estimated by using H/ and ? shows maximum increase in the electron density of the order of ~80 times as compared to the normal day values. The electron density was found to increase exponentially with increase in the solar flux intensity. The solar flare effect on horizontal component (H) of the Earth's magnetic field over an equatorial station, Tirunelveli (Geographic lat., 8.7°N, long., 77.8°E, dip lat., 0.4°N), shows a maximum increase in H of ~8.5% for M class solar flares. The increase in H is due to the additional magnetic field produced by the ionospheric electrojet over the equatorial station.

  14. Flaring Solar Hale Sector Boundaries

    NASA Astrophysics Data System (ADS)

    Svalgaard, L.; Hannah, I. G.; Hudson, H. S.

    2011-05-01

    The sector structure that organizes the magnetic field of the solar wind into large-scale domains has a clear pattern in the photospheric magnetic field as well. The rotation rate, 27-28.5 days, implies an effectively rigid rotation originating deeper in the solar interior than the sunspots. The photospheric magnetic field is known to be concentrated near that portion (the Hale boundary) in each solar hemisphere, where the change in magnetic sector polarity matches that between the leading and following sunspot polarities in active regions in the respective hemispheres. We report here that flares and microflares also concentrate at the Hale boundaries, implying that flux emergence and the creation of free magnetic energy in the corona also have a direct cause in the deep interior.

  15. 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 energy, and produce X-rays, microwaves and a shock wave that heats the solar surface. Kosovichev and Zharkova developed a theory that predicts the nature and magnitude of the shock waves that this beam of energetic electrons should create when they slam down into the solar atmosphere. Although their theory directed them to the right area to search for the seismic waves, the waves that they found were 10 times stronger than they had predicted. "They were so strong that you can see them in the raw data," Kosovichev says. The solar seismic waves appear to be compression waves like the "P" waves generated by an earthquake. They travel throughout the Sun's interior. In fact, the waves should recombine on the opposite side of the Sun from the location of the flare to create a faint duplicate of the original ripple pattern, Kosovichev predicts. Now that they know how to find them, the SOHO scientists say that the seismic waves generated by solar flares should allow them to verify independently some of the conditions in the solar interior that they have inferred from studying the pattern of waves that are continually ruffling the Sun's surface. SOHO is part of the International Solar-Terrestrial Physics (ISTP) program, a global effort to observe and understand our star and its effects on our environment. The ISTP mission includes more than 20 satellites, coupled with with ground-based observatories and modeling centers, that allow scientists to study the Sun, the Earth, and the space between them in unprecedented detail. ISTP is a joint program of NASA, ESA, Japan's Institute for Astronautical Science, and Russia's Space Research Institute. Still images of the solar quake can be found at the following internet address: FTP://PAO.GSFC.NASA.GOV/newsmedia/QUAKE/ For further information, please contact : ESA Public Relations Division Tel:+33(0)1.53.69.71.55 Fax: +33(0)1.53.69.76.90 3

  16. Impulsive phase of solar flares

    NASA Technical Reports Server (NTRS)

    Kane, S. R.; Crannell, C. J.; Datlowe, D.; Feldman, U.; Gabriel, A.; Hudson, H. S.; Kundu, M. R.; Maetzler, C.; Neidig, D.; Petrosian, V.

    1980-01-01

    The present understanding of the impulsive phase of a solar flare, characterized by short-duration bursts of impulsive hard X-ray, EUV, optical and radio emission indicating the release of energetic electrons is reviewed. Observations of the spectral distribution of impulsive hard X-ray bursts and of Type III and radio continuum bursts are presented and interpreted in terms of energetic electron distributions, and impulsive EUV, XUV, soft X-ray and optical observations, which provide a lower limit to total energy release during the impulsive phase, are discussed. The role of energetic electrons in exciting the hard X-ray, EUV and microwave emissions is considered, and thin-target, thick-target, partial-precipitation and thermal models of impulsive phase electron acceleration are evaluated in light of the observations. It is noted that available data do not allow discrimination between a thermal or a nonthermal electron distribution, on which depends the proportion of flare energy supplied by the energetic electrons, and that data favors models which permit at least partial electron precipitation. Future observational and theoretical work is indicated.

  17. MAGNETIC FIELD STRUCTURES TRIGGERING SOLAR FLARES AND CORONAL MASS EJECTIONS

    SciTech Connect

    Kusano, K.; Bamba, Y.; Yamamoto, T. T. [Solar-Terrestrial Environment Laboratory, Nagoya University, Furo-cho, Chikusa-ku, Nagoya, Aichi 464-8601 (Japan); Iida, Y.; Toriumi, S. [Department of Earth and Planetary Science, University of Tokyo, Hongo, Bunkyo-ku, Tokyo 113-0033 (Japan); Asai, A., E-mail: kusano@nagoya-u.jp [Unit of Synergetic Studies for Space, Kyoto University, 17 Kitakazan Ohmine-cho, Yamashina-ku, Kyoto 607-8471 (Japan)

    2012-11-20

    Solar flares and coronal mass ejections, the most catastrophic eruptions in our solar system, have been known to affect terrestrial environments and infrastructure. However, because their triggering mechanism is still not sufficiently understood, our capacity to predict the occurrence of solar eruptions and to forecast space weather is substantially hindered. Even though various models have been proposed to determine the onset of solar eruptions, the types of magnetic structures capable of triggering these eruptions are still unclear. In this study, we solved this problem by systematically surveying the nonlinear dynamics caused by a wide variety of magnetic structures in terms of three-dimensional magnetohydrodynamic simulations. As a result, we determined that two different types of small magnetic structures favor the onset of solar eruptions. These structures, which should appear near the magnetic polarity inversion line (PIL), include magnetic fluxes reversed to the potential component or the nonpotential component of major field on the PIL. In addition, we analyzed two large flares, the X-class flare on 2006 December 13 and the M-class flare on 2011 February 13, using imaging data provided by the Hinode satellite, and we demonstrated that they conform to the simulation predictions. These results suggest that forecasting of solar eruptions is possible with sophisticated observation of a solar magnetic field, although the lead time must be limited by the timescale of changes in the small magnetic structures.

  18. Transient particle acceleration associated with solar flares

    NASA Technical Reports Server (NTRS)

    Chupp, E. L.

    1990-01-01

    Mechanisms that apply to solar flares are discussed, and their applicability to other astrophysical sites, where transient X-ray and gamma-ray bursts occur, is tested. Two different approaches are used to determine the characteristics of the charged particles, accelerated in association with solar flares: (1) measurement of the energy spectra and composition of charged particles observed in space and believed to be associated with a specific solar flare; and (2) recording of electromagnetic emissions in the visible, ultraviolet, soft X-ray, hard X-ray, and gamma-ray spectral regions, and also high-energy neutrons produced in the solar atmosphere by the particles accelerated in association with the solar flare. It is suggested that, at the present level of knowledge, regions where particle acceleration and interactions occur are unlikely to be specified.

  19. Solar flares and magnetic topology

    NASA Technical Reports Server (NTRS)

    Sturrock, P. A.

    1987-01-01

    This article is a very brief review and comparison of the observational properties of flares and theoretical concepts of models of flares, especially the concepts of magnetic topology and its evolution. We examine the environmental aspects of flare behavior. Some of these aspects must be consequences of unknown processes occurring below the photosphere. Other aspects involve structures - such as filaments - that are closely related to flares. We then examine properties of flares to try to distinguish the different phases of energy release that can occur in the course of a flare. Finally a schematic scenario is offered to interpret these phases in terms of this scenario.

  20. 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.

  1. Excitation of XUV radiation in solar flares

    NASA Technical Reports Server (NTRS)

    Emslie, A. Gordon

    1992-01-01

    The goal of the proposed research was to understand the means by which XUV radiation in solar flares is excited, and to use this radiation as diagnostics of the energy release and transport processes occurring in the flare. Significant progress in both of these areas, as described, was made.

  2. Future optical observations of solar flares

    Microsoft Academic Search

    R. Falciani

    1988-01-01

    Trends in optical observations of solar flares are reviewed, including recently developed instruments and facilities which could contribute to future studies. It is suggested that the physical significance of the visible spectral range data should be improved and that coherent and self-consistent analyses of different spectral signatures of the same physical phenomena in various layers of the flare atmosphere should

  3. Ensemble Forecast of Major Solar Flares

    NASA Astrophysics Data System (ADS)

    Guerra, J. A.; Pulkkinen, A. A.; Uritsky, V. M.

    2014-12-01

    We present the results from the first ensemble prediction model for solar flares of M and X classes. Using the forecasts from 4 flare-predictor methods hosted at the Community Coordinated Modeling Center (NASA-GSFC), this model provides an ensemble forecast by combining flaring probabilities from individual methods. Performance-based combination weights are calculated using a procedure that applies a threshold to the probability time series and then minimizes the chi squared parameter between the model and observed flare time series. We used a sample of 13 recent active regions that produced several M- and X-class flares. We will discuss the results of the new ensemble approach and show how the method can be used in a real-time environment for flare predictions.

  4. Distant Suns: Solar Flares as Proxies for Stellar Flares

    NASA Astrophysics Data System (ADS)

    Kashyap, Vinay; Reeves, Kathy; Wargelin, Brad

    2009-09-01

    The solar corona has been a Rosetta stone directing our knowledge and understanding of stellar coronae. Because of its proximity, the Sun can be observed in great detail, and detailed physical models derived from such observations are often used to explain stellar phenomena. Large stellar flares are traditionally modeled as a single coronal loop evolving hydrodynamically. However, such a picture has no counterpart on the Sun, where flares are observed to be complex events, generally affecting large areas of an active region and resulting in post-flare loop arcades that have a different magnetic topology compared to the pre-flare region. Here we discuss a large flare on a dM3.5Ve dwarf, Ross 154, that was observed with Chandra. The flare shows a pronounced dual-decay structure. We model the event as a set of cascading loops in an arcade that are sequentially energized, leading to predicted light curves that also exhibit similar behavior. This work was supported by CXC NASA contract NAS8-39073 (VLK, BW) and XRT NASA contract NNM07AB07C (KR).

  5. Solar flares: an extremum of reconnection

    SciTech Connect

    Colgate, S.A.

    1983-12-22

    Three points are emphasized: that the solar flare is that particular astrophysical phenomenon that is the extremum of reconnection, no other phenomenon demands as rapid magnetic flux annihilation as is seen in the solar flare; that plasma physics experiments can and should be performed in the laboratory that model reconnection as we observe it in astrophysics; and that stochastic field lines derived from something similar to Alfven wave turbulence are a necessary part of reconnection.

  6. 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

  7. 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.

  8. 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.

  9. 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.

  10. 2 Solar flare signatures of the ionospheric GPS total electron content 3 J. Y. Liu,1,2

    E-print Network

    Chen, Yuh-Ing

    2 Solar flare signatures of the ionospheric GPS total electron content 3 J. Y. Liu,1,2 C. H. Lin,1, ionospheric solar flare effects on the total electron content (TEC) and 7 associated time rate of change (r. The occurrence times and 9 locations of 11 solar flares are isolated from the 1­8 A° X-ray radiations of the 10

  11. An overview of solar and stellar flare research

    NASA Technical Reports Server (NTRS)

    Haisch, Bernhard M.

    1989-01-01

    A overview of the topics concerning solar and stellar flares at the IAU Colloquium No. 104 is presented. Work being done on the location of flares, the characteristics of solar flares, the optical or white-light flare, and the question of microflaring is reviewed. Theoretical questions and hydrodynamic models are examined, and suggested areas for future investigations are addressed.

  12. Outstanding problems of solar flare research

    NASA Technical Reports Server (NTRS)

    Hudson, H. S.

    1988-01-01

    This paper describes in very broad terms the current status of problems in understanding solar flares, from the personal perspective of an observer. It goes on to summarize new observational directions to help solve the problems, including support for the suggestion for stereoscopic imaging of the solar atmosphere.

  13. RADIO EMISSION OF SOLAR FLARE PARTICLE ACCELERATION

    E-print Network

    RADIO EMISSION OF SOLAR FLARE PARTICLE ACCELERATION A. O. Benz Abstract The solar corona is a very be considered as a particle accelerator. The free mobility of charged particles in a dilute plasma to accelerate particles in resonance. From a plasma physics point of view, acceleration is not surprising

  14. Velocity structure of solar flare plasmas

    NASA Astrophysics Data System (ADS)

    Watanabe, Tetsuya; Watanabe, Kyoko; Hara, Hirohisa; Imada, Shinsuke

    Thanks to its increased sensitivity and spectral resolution, EIS enabled emission line profile analysis for the first time in solar EUV spectroscopy, and it found detailed structures in velocity and temperature in solar flares. A widely accepted model for solar flares incorporates magnetic reconnection in the corona which results in local heating as well as acceleration of nonthermal particle beams. The standard model of solar flares is called the CSHKP model, arranging the initials of model proposers. We find loop-top hot source, fast outflows nearby, inflow structure flowing to the hot source that appeared in the impulsive phase of long-duration eruptive flares. From the geometrical relationships of these phenomena, we conclude that they provide evidence for magnetic reconnection that occurs near the loop-top region. The reconnection rate is estimated to 0.05 - 0.1, which supports the Petschek-type magnetic reconnection. The nonthermal particle beams will travel unimpeded until they reach the cold, dense chromosphere, where the energy of the beam is predominantly used to heat the chromosphere at the foot points of flaring loops. Explosive chromospheric evaporation happens when the beam energy is high enough that the chromosphere cannot radiate away energy fast enough and hence expands at high velocities into the corona. Spatially resolved observations of chromopheric evaporation during the initial phases of impulsive flares, a few bright points of Fexxiii and Fexxiv emission lines at the footpoints of flaring loops present dominated blue-shifted components of 300 - 400 kms (-1) , while Fexv/xvi lines are nearly stationary, and Feviii and Sivii lines present +50 kms (-1) red shifts. We will review these new views on dynamical structure in flares.

  15. 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.

  16. Temporal aspects and frequency distributions of solar soft X-ray flares

    E-print Network

    A. Veronig; M. Temmer; A. Hanslmeier; W. Otruba; M. Messerotti

    2002-07-11

    A statistical analysis of almost 50000 soft X-ray (SXR) flares observed by GOES during the period 1976-2000 is presented. On the basis of this extensive data set, statistics on temporal properties of soft X-ray flares, such as duration, rise and decay times with regard to the SXR flare classes is presented. Correlations among distinct flare parameters, i.e. SXR peak flux, fluence and characteristic times, and frequency distributions of flare occurrence as function of the peak flux, the fluence and the duration are derived. We discuss the results of the analysis with respect to statistical flare models, the idea of coronal heating by nanoflares, and elaborate on implications of the obtained results on the Neupert effect in solar flares.

  17. Flare Hybrids

    NASA Astrophysics Data System (ADS)

    Tomczak, M.; Dubieniecki, P.

    2015-04-01

    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.

  18. Periodicity in the most violent solar eruptions: recent observations of coronal mass ejections and flares revisited

    NASA Astrophysics Data System (ADS)

    Gao, Peng-Xin; Xie, Jing-Lan; Liang, Hong-Fei

    2012-03-01

    Using the Hilbert-Huang Transform method, we investigate the periodicity in the monthly occurrence numbers and monthly mean energy of coronal mass ejections (CMEs) observed by the Large Angle and Spectrometric Coronagraph Experiment on board the Solar and Heliographic Observatory from 1999 March to 2009 December. We also investigate the periodicity in the monthly occurrence numbers of H? flares and monthly mean flare indices from 1996 January to 2008 December. The results show the following. (1) The period of 5.66 yr is found to be statistically significant in the monthly occurrence numbers of CMEs; the period of 10.5 yr is found to be statistically significant in the monthly mean energy of CMEs. (2) The periods of 3.05 and 8.70yr are found to be statistically significant in the monthly occurrence numbers of H? flares; the period of 9.14yr is found to be statistically significant in the monthly mean flare indices.

  19. Deterministically Driven Avalanche Models of Solar Flares

    NASA Astrophysics Data System (ADS)

    Strugarek, Antoine; Charbonneau, Paul; Joseph, Richard; Pirot, Dorian

    2014-08-01

    We develop and discuss the properties of a new class of lattice-based avalanche models of solar flares. These models are readily amenable to a relatively unambiguous physical interpretation in terms of slow twisting of a coronal loop. They share similarities with other avalanche models, such as the classical stick-slip self-organized critical model of earthquakes, in that they are driven globally by a fully deterministic energy-loading process. The model design leads to a systematic deficit of small-scale avalanches. In some portions of model space, mid-size and large avalanching behavior is scale-free, being characterized by event size distributions that have the form of power-laws with index values, which, in some parameter regimes, compare favorably to those inferred from solar EUV and X-ray flare data. For models using conservative or near-conservative redistribution rules, a population of large, quasiperiodic avalanches can also appear. Although without direct counterparts in the observational global statistics of flare energy release, this latter behavior may be relevant to recurrent flaring in individual coronal loops. This class of models could provide a basis for the prediction of large solar flares.

  20. 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

  1. High energy component of solar flares

    NASA Astrophysics Data System (ADS)

    Makhmutov, Vladimir; Kurt, Victoria; Bazilevskaya, Galina; Kaufmann, Pierre; Raulin, Jean-Pierre; Stozhkov, Yuri; Yushkov, Boris; Grechnev, Victor

    We have analysed experimental data from the satellites CORONAS-F, YOHKOH, TRACE, GOES and data recorded by the ground based Solar Submillimeter Telescope (SST) during the solar flares on August 25, 2001 and November 4, 2003. Almost simultaneous changes in the > 10-50 MeV gamma-ray spectra and in the > 200 GHz radio flux time profile were found at the very beginning of the impulsive phase of these events. We discuss possible reasons for these observed effects.

  2. Solar Flare Prediction Using Advanced Feature Extraction, Machine Learning, and Feature Selection

    NASA Astrophysics Data System (ADS)

    Ahmed, Omar W.; Qahwaji, Rami; Colak, Tufan; Higgins, Paul A.; Gallagher, Peter T.; Bloomfield, D. Shaun

    2013-03-01

    Novel machine-learning and feature-selection algorithms have been developed to study: i) the flare-prediction-capability of magnetic feature (MF) properties generated by the recently developed Solar Monitor Active Region Tracker ( SMART); ii) SMART's MF properties that are most significantly related to flare occurrence. Spatiotemporal association algorithms are developed to associate MFs with flares from April 1996 to December 2010 in order to differentiate flaring and non-flaring MFs and enable the application of machine-learning and feature-selection algorithms. A machine-learning algorithm is applied to the associated datasets to determine the flare-prediction-capability of all 21 SMART MF properties. The prediction performance is assessed using standard forecast-verification measures and compared with the prediction measures of one of the standard technologies for flare-prediction that is also based on machine-learning: Automated Solar Activity Prediction ( ASAP). The comparison shows that the combination of SMART MFs with machine-learning has the potential to achieve more accurate flare-prediction than ASAP. Feature-selection algorithms are then applied to determine the MF properties that are most related to flare occurrence. It is found that a reduced set of six MF properties can achieve a similar degree of prediction accuracy as the full set of 21 SMART MF properties.

  3. The probability of SWF occurrence in relation to solar activity

    Microsoft Academic Search

    L. P. Morozova

    1989-01-01

    Solar terrestrial researches have revealed substantial meaning of nonsteady events on the Sun, mainly solar flares, for the processes taking place in ionosphere. Solar flares result in the numerous consequences, account and prediction of which become necessary in our days. It is well known, that ionospheric disturbances following solar flares cause strong disturbances in the ionosphere, which severely violate radio

  4. A kinematic model of a solar flare.

    NASA Technical Reports Server (NTRS)

    Nakagawa, Y.; Wu, S. T.; Han, S. M.

    1973-01-01

    Hyder advocated the idea that the optical (H-alpha) flares can be identified with the response of the solar chromosphere to an infalling material stream resulting from the 'disparition brusque' of a prominence. Since some flares are observed without any apparent association with infalling streams, in this paper we examine the possibility of identifying the optical flare with the response of the chromosphere to a supersonic disturbance, i.e., a shock, propagating downward. The undisturbed chromosphere is represented by the Harvard-Smithsonian Reference Atmosphere and the evolution of the shock is evaluated with the use of the CCW (Chisnell, Chester, Whitham) approximation based on the theory of characteristics. It is shown that the chromosphere is heated by the shock, that radiation is enhanced, and that the enhanced radiation terminates the shock around the height of the temperature minimum.

  5. 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.

  6. Sawtooth oscillations in solar flare radio emission

    NASA Astrophysics Data System (ADS)

    Klassen, A.; Aurass, H.; Mann, G.

    2001-04-01

    For the first time, we found a spectral fine structure of solar meter wave radio burst emission which can be due to sawtooth oscillations in the hot flare plasma. This finding newly underlines an analogy between coronal and laboratory plasma processes. The sawteeth occur during the impulsive flare phase hard X-ray emission and consist of a sequence of almost identical narrow band (delta f/f =~ 1%) drift bursts. All cases of our sample were associated with a radio emitting coronal shock wave (type II burst). Similar oscillations are familiar in tokamak plasmas and understood as signature of the kink instability of the toroidal current. We argue that the radio sawteeth are nonthermal plasma emission due to 2-4% density fluctuations of the flare plasma. The fluctuations can be excited by a current instability in a coronal flare loop or in a vertical flaring current sheet e.g. occuring behind a rising magnetic flux rope. This is in analogy to kink instability effects observed in laboratory plasmas.

  7. Testing Automated Solar Flare Forecasting with 13 Years of Michelson Doppler Imager Magnetograms

    NASA Astrophysics Data System (ADS)

    Mason, J. P.; Hoeksema, J. T.

    2010-11-01

    Flare occurrence is statistically associated with changes in several characteristics of the line-of-sight magnetic field in solar active regions (ARs). We calculated magnetic measures throughout the disk passage of 1075 ARs spanning solar cycle 23 to find a statistical relationship between the solar magnetic field and flares. This expansive study of over 71,000 magnetograms and 6000 flares uses superposed epoch (SPE) analysis to investigate changes in several magnetic measures surrounding flares and ARs completely lacking associated flares. The results were used to seek any flare associated signatures with the capability to recover weak systematic signals with SPE analysis. SPE analysis is a method of combining large sets of data series in a manner that yields concise information. This is achieved by aligning the temporal location of a specified flare in each time series, then calculating the statistical moments of the "overlapping" data. The best-calculated parameter, the gradient-weighted inversion-line length (GWILL), combines the primary polarity inversion line (PIL) length and the gradient across it. Therefore, GWILL is sensitive to complex field structures via the length of the PIL and shearing via the gradient. GWILL shows an average 35% increase during the 40 hr prior to X-class flares, a 16% increase before M-class flares, and 17% increase prior to B-C-class flares. ARs not associated with flares tend to decrease in GWILL during their disk passage. Gilbert and Heidke skill scores are also calculated and show that even GWILL is not a reliable parameter for predicting solar flares in real time.

  8. A solar tornado triggered by flares?

    E-print Network

    Panesar, N K; Tiwari, S K; Low, B C

    2012-01-01

    Solar tornados are dynamical, conspicuously helical magnetic structures mainly observed as a prominence activity. We investigate and propose a triggering mechanism for the solar tornado observed in a prominence cavity by SDO/AIA on September 25, 2011. 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\\AA\\ are analyzed in relation to the tornado activities observed at the limb in 171\\AA. Each of the three flares and its related EUV wave occurred within 10 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 acceleration of tornado motion after the ...

  9. Soft X-Ray Pulsations in Solar Flares

    NASA Astrophysics Data System (ADS)

    Simões, P. J. A.; Hudson, H. S.; Fletcher, L.

    2015-05-01

    The soft X-ray emissions (h?>1.5 keV) of solar flares mainly come from the bright coronal loops at the highest temperatures normally achieved in the flare process. Their ubiquity has led to their use as a standard measure of flare occurrence and energy, although the overwhelming bulk of the total flare energy goes elsewhere. Recently Dolla et al. (Astrophys. J. Lett. 749, L16, 2012) noted quasi-periodic pulsations (QPP) in the soft X-ray signature of the X-class flare SOL2011-02-15, as observed by the standard photometric data from the GOES (Geostationary Operational Environmental Satellite) spacecraft. In this article we analyse the suitability of the GOES data for this type of analysis and find them to be generally valuable after September, 2010 (GOES-15). We then extend the result of Dolla et al. to a complete list of X-class flares from Cycle 24 and show that most of them (80 %) display QPPs in the impulsive phase. The pulsations show up cleanly in both channels of the GOES data, making use of time-series of irradiance differences (the digital time derivative on the 2-s sampling). We deploy different techniques to characterise the periodicity of GOES pulsations, considering the red-noise properties of the flare signals, finding a range of characteristic time scales of the QPPs for each event, but usually with no strong signature of a single period dominating in the power spectrum. The QPP may also appear on somewhat longer time scales during the later gradual phase, possibly with a greater tendency towards coherence, but the sampling noise in GOES difference data for high irradiance values (X-class flares) makes these more uncertain. We show that there is minimal phase difference between the differenced GOES energy channels, or between them and the hard X-ray variations on short time scales. During the impulsive phase, the footpoints of the newly forming flare loops may also contribute to the observed soft X-ray variations.

  10. Prediction of solar flare through sunspot digital optical observation

    NASA Astrophysics Data System (ADS)

    Said, N. M. M.; Aziz, A. H. A.; Kamaruddin, F.

    2015-04-01

    In this paper, we discuss about the prediction of solar flare through sunspot digital optical observation, based on 4 sets of H alpha archive data from the Big Bear Solar Observatory. The brightness and pattern of 3D surface plot of the sunspot areas are analyzed for a few hours before and after the eruption of solar flare. Results show that the sunspot areas are gradually merged and at its peak brightness before the eruption of solar flare. The possible cause of these two precursors of solar flare will then be discussed.

  11. 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.

  12. 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.

  13. Impulsive phase explosive dynamics. [of solar flares

    NASA Technical Reports Server (NTRS)

    Canfield, Richard C.

    1986-01-01

    Observational evidence and theoretical models for explosive mass motion in the impulsive phase of solar flares are reviewed. Data showing X-ray blueshifts and H-alpha redshifts are presented in graphs and diagrams and interpreted in terms of upward-moving material at 10 million K and downward-moving material at 10,000 K. This motion is found to be most simply explained in terms of explosive chromospheric evaporation.

  14. 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.

  15. 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.

  16. Automatic Solar Flare Tracking Using Image-Processing Techniques

    Microsoft Academic Search

    Ming Qu; Frank Shih; Ju Jing; Haimin Wang

    2004-01-01

    Measurement of the evolution properties of solar flares through their complete cyclic development is crucial in the studies of Solar Physics. From the analysis of solar Ha images, we used Support Vector Machines (SVMs) to automatically detect flares and applied image segmentation techniques to compute their properties. We also present a solution for automatically tracking the apparent separation motion of

  17. Quasi-Periodic Pulsations in Solar Flares

    NASA Astrophysics Data System (ADS)

    Nakariakov, V. M.; Melnikov, V. F.

    2009-12-01

    Quasi-periodic pulsations (QPP) are a common feature of flaring energy releases in the solar atmosphere, observed in all bands, from radio to hard X-ray. In this review we concentrate on QPP with the periods longer than one second. Physical mechanisms responsible for the generation of long QPP split into two groups: “load/unload” mechanisms and MHD oscillations. Load/unload mechanisms are repetitive regimes of flaring energy releases by magnetic reconnection or by other means. MHD oscillations can affect all elements of the flaring emission generation: triggering of reconnection and modulation of its rate, acceleration and dynamics of non-thermal electrons, and physical conditions in the emitting plasmas. In the case of MHD oscillations, the periodicity of QPP is determined either by the presence of some resonances, e.g. standing modes of plasma structures, or by wave dispersion. Periods and other parameters of QPP are linked with properties of flaring plasmas and their morphology. Observational investigation of the QPP generation mechanisms based upon the use of spatial information, broadband spectral coverage and multi-periodicity is discussed.

  18. Flare models. [solar physics current status review

    NASA Technical Reports Server (NTRS)

    Sturrock, P. A.

    1980-01-01

    The current status of solar flare modeling is reviewed. Primary and secondary observational features that a proposed flare model should be capable of explaining are discussed, including energy storage and release, particle acceleration, mass ejection, heating of the temperature minimum region, X-ray, EUV, UV, visible and radio emission and mass flow. Consideration is then given to the twisted flux tube paramagnetic recombination model of Gold and Hoyle (1960), the current model of Alfven and Carlqvist (1967), closed current-sheet models such as those of Syrovatskii (1966, 1969, 1977) and Uchida and Sakurai (1977), open-field models such as those of Carmichael (1964) and Barnes and Sturrock (1972), the emerging flux model of Heyvaerts and Priest (1974, 1977, 1978) and the loop-flare models of Spicer (1977) and Colgate (1978). It is noted that no one model can yet account for all the observational features, and that there may turn out to be several types of flare, each requiring its own explanation.

  19. Searches for comet-induced solar flares

    NASA Astrophysics Data System (ADS)

    Ibadov, Subhon; Ibodov, Firuz

    During the last decade we have carried out analytical consideration of the impacts of comets with the Sun: the study of passage of cometary nuclei through the solar chromosphere and photosphere was carried out taking into account aerodynamic crushing of the nucleus, transversal expansion of the crushed mass and aerodynamic deceleration of the flattening structure. The results indicate that the stopping of the hypervelocity, more than 600 km/s, comet matter near the photosphere has essentially "explosive" character and will be accompanied by generation of a strong "blast" shock wave as well as ejection of a hot plasma from a relatively very thin,"exploding", near-photosphere layer. Observational manifestations of these processes, comet-induced solar flares, CISF, will be anomalous line emission of metal atoms/ions like Fe, Si, etc. from chromosphere/corona regions and continuum emission of a high-temperature, around 10^6-10^7 K, plasma cloud near the solar surface. Space observations of the phenomena by solar telescopes, including future out-of-ecliptic ones, are of interest for the physics/prognosis of solar flares as well as physics of comets.

  20. Observational Evidences of Ballooning Instability in Solar Flares

    Microsoft Academic Search

    K. Shibasaki

    1998-01-01

    Radio imaging observation of the solar flare on January 2, 1993 showed a formation process of radio sources over the flare loop (Shibasaki, 1996). In the present paper, we interpret this overtopping radio sources as magnetic islands (or balloons) produced by a ballooning instability due to high pressure (or high beta value) in the flare loop. The overtopping radio sources

  1. Dependence of the aurora borealis occurrences on the solar-terrestrial parameters

    Microsoft Academic Search

    Y. Liritzis; B. Petropoulos

    1986-01-01

    The recent measurements made by satellites of the aurorae in connection with solar phenomena have increased interest in auroral research. In the present investigation, we establish that, for the 20th solar cycle, the occurrence of visual discrete aurorae A, deduced from a complete set of data, is significantly related to the sunspot numbers Rz, the number of flares F (of

  2. Acceleration of runaway electrons in solar flares

    NASA Technical Reports Server (NTRS)

    Moghaddam-Taaheri, E.; Goertz, C. K.

    1990-01-01

    The dc electric field acceleration of electrons out of a thermal plasma and the evolution of the runaway tail are studied numerically, using a relativistic quasi-linear code based on the Ritz-Galerkin method and finite elements. A small field-aligned electric field is turned on at a certain time. The resulting distribution function from the runaway process is used to calculate the synchrotron emission during the evolution of the runaway tail. It is found that, during the runaway tail formation, which lasts a few tens of seconds for typical solar flare conditions, the synchrotron emission level is low, almost ot the same order as the emission from the thermal plasma, at the high-frequency end of the spectrum. However, the emission is enhanced explosively in a few microseconds by several orders of magnitude at the time the runaway tail stops growing along the magnetic field and tends toward isotropy due to the pitch-angle scattering of the fast particles. Results indicate that, in order to account for the observed synchrotron emission spectrum of a typical solar flare, the electric field acceleration phase must be accompanied or preceded by a heating phase which yields an enhanced electron temperature of about 2-15 keV in the flare region if the electric field is 0.1-0.2 times the Dreicer field and cyclotron-to-plasma frequency ratios are of order 1-2.

  3. 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.

  4. Nonlocal thermal transport in solar flares

    NASA Technical Reports Server (NTRS)

    Karpen, Judith T.; Devore, C. Richard

    1987-01-01

    A flaring solar atmosphere is modeled assuming classical thermal transport, locally limited thermal transport, and nonlocal thermal transport. The classical, local, and nonlocal expressions for the heat flux yield significantly different temperature, density, and velocity profiles throughout the rise phase of the flare. Evaporation of chromospheric material begins earlier in the nonlocal case than in the classical or local calculations, but reaches much lower upward velocities. Much higher coronal temperatures are achieved in the nonlocal calculations owing to the combined effects of delocalization and flux limiting. The peak velocity and momentum are roughly the same in all three cases. A more impulsive energy release influences the evolution of the nonlocal model more than the classical and locally limited cases.

  5. The impulsive flux transfer solar flare model

    NASA Astrophysics Data System (ADS)

    Baum, P. J.; Bratenahl, A.

    A revised impulsive-flux-transfer solar-flare model is proposed in which magnetic reconnection and an electric double layer are combined and interact. The model requires a single stage of acceleration and several stages of deceleration and thermalization. The time development of flare parameters is calculated using a circuit analog that treats the double layer as an effective resistance, which is computed from the ultrarelativistic Child-Langmuir law. The model indicates that: (1) accelerated particles are quasi-thermalized at the ends of the double layer; (2) the electrons generate thermal X-rays, and the protons produce neutrons by spallation reactions with heavy nuclei; and (3) the neutrons travel to the photosphere, capturing protons to produce nuclear gamma-ray emission.

  6. 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.

  7. The Variability of Solar X-Ray Flux and Flare Frequency through a Solar Cycle

    NASA Astrophysics Data System (ADS)

    O'Connell, M.; Marchese, A.; Hirschberger, M.; Mezzafonte, D.; Chen, K.

    2013-12-01

    Solar flares are eruptions on the Sun's surface that emit ultraviolet radiation, x-rays, visible light and coronal mass ejections (CMEs). The intensity and frequency of solar flares have been observed to vary over time. To better understand fluctuations in solar flare intensity and frequency, data for various solar flare properties were obtained from satellites, including Geostationary Operational Environmental Satellite (GOES) and Solar TErrestrial RElations Observatory (STEREO) for 2000-2012. Solar flare statistics were analyzed and found to closely follow the 11-year solar cycle, with some deviations. Total daily x-ray flux, comprised of the background radiation and deviations caused by solar flare activity, was also examined for 2000-2012. The magnitude and frequency of the x-ray flux were observed in relation to annual sunspot count. A correlation to other solar activity parameters was observed. These results may help in the understanding and forecasting of solar flare variability.

  8. PRODUCTIVITY OF SOLAR FLARES AND MAGNETIC HELICITY INJECTION IN ACTIVE REGIONS

    SciTech Connect

    Park, Sung-hong; Wang Haimin [Space Weather Research Laboratory, New Jersey Institute of Technology, 323 Martin Luther King Boulevard, 101 Tiernan Hall, Newark, NJ 07102 (United States); Chae, Jongchul, E-mail: sp295@njit.ed [Astronomy Program and FPRD, Department of Physics and Astronomy, Seoul National University, Seoul 151-742 (Korea, Republic of)

    2010-07-20

    The main objective of this study is to better understand how magnetic helicity injection in an active region (AR) is related to the occurrence and intensity of solar flares. We therefore investigate the magnetic helicity injection rate and unsigned magnetic flux, as a reference. In total, 378 ARs are analyzed using SOHO/MDI magnetograms. The 24 hr averaged helicity injection rate and unsigned magnetic flux are compared with the flare index and the flare-productive probability in the next 24 hr following a measurement. In addition, we study the variation of helicity over a span of several days around the times of the 19 flares above M5.0 which occurred in selected strong flare-productive ARs. The major findings of this study are as follows: (1) for a sub-sample of 91 large ARs with unsigned magnetic fluxes in the range from (3-5) x 10{sup 22} Mx, there is a difference in the magnetic helicity injection rate between flaring ARs and non-flaring ARs by a factor of 2; (2) the GOES C-flare-productive probability as a function of helicity injection displays a sharp boundary between flare-productive ARs and flare-quiet ones; (3) the history of helicity injection before all the 19 major flares displayed a common characteristic: a significant helicity accumulation of (3-45) x 10{sup 42} Mx{sup 2} during a phase of monotonically increasing helicity over 0.5-2 days. Our results support the notion that helicity injection is important in flares, but it is not effective to use it alone for the purpose of flare forecast. It is necessary to find a way to better characterize the time history of helicity injection as well as its spatial distribution inside ARs.

  9. Determination of the time of occurrence of gamma flares at different points in space

    NASA Technical Reports Server (NTRS)

    Novak, B. L.

    1980-01-01

    The problem of determining the time of occurrence of gamma flares at different points in space is considered. This problem arises in the localization of sources of gamma flares by the triangulation method using several spacecraft. A study is made of different methods for determining the time at which the flare reaches the spacecraft and algorithms are given for estimating their accuracy. Results of processing the model information are also given.

  10. A Statistical Solar Flare Forecast Method

    E-print Network

    M. S. Wheatland

    2005-05-14

    A Bayesian approach to solar flare prediction has been developed, which uses only the event statistics of flares already observed. The method is simple, objective, and makes few ad hoc assumptions. It is argued that this approach should be used to provide a baseline prediction for certain space weather purposes, upon which other methods, incorporating additional information, can improve. A practical implementation of the method for whole-Sun prediction of Geostationary Observational Environment Satellite (GOES) events is described in detail, and is demonstrated for 4 November 2003, the day of the largest recorded GOES flare. A test of the method is described based on the historical record of GOES events (1975-2003), and a detailed comparison is made with US National Oceanic and Atmospheric Administration (NOAA) predictions for 1987-2003. Although the NOAA forecasts incorporate a variety of other information, the present method out-performs the NOAA method in predicting mean numbers of event days, for both M-X and X events. Skill scores and other measures show that the present method is slightly less accurate at predicting M-X events than the NOAA method, but substantially more accurate at predicting X events, which are important contributors to space weather.

  11. Ionic charge distributions of energetic particles from solar flares

    NASA Technical Reports Server (NTRS)

    Mullan, D. J.; Waldron, W. L.

    1986-01-01

    The effects which solar flare X-rays have on the charge states of solar cosmic rays is determined quantitatively. Rather than to characterize the charge distribution by temperature alone, it is proposed that the X-ray flux at the acceleration site also is used. The effects of flare X-rays are modeled mathematically.

  12. Observations of the Effects of Solar Flares on Earth

    E-print Network

    Withers, Paul

    - enhanced profiles (c) X-ray fluxes at Earth on this day between 0.5-3 A (solid, XS) and 1-8 A (dashed, XLObservations of the Effects of Solar Flares on Earth and Mars Paul Withers, Michael Mendillo, Joei and their environments. Solar flares cause sudden ionospheric disturbances at Earth and coronal mass ejections cause

  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. PMID:10859130

  14. The probability of SWF occurrence in relation to solar activity

    NASA Technical Reports Server (NTRS)

    Morozova, L. P.

    1989-01-01

    Solar terrestrial researches have revealed substantial meaning of nonsteady events on the Sun, mainly solar flares, for the processes taking place in ionosphere. Solar flares result in the numerous consequences, account and prediction of which become necessary in our days. It is well known, that ionospheric disturbances following solar flares cause strong disturbances in the ionosphere, which severely violate radio systems (communication, navigation, etc.). Possibilities of sudden short wave fadeouts (SWF) prediction are considered.

  15. The probability of SWF occurrence in relation to solar activity

    NASA Astrophysics Data System (ADS)

    Morozova, L. P.

    1989-09-01

    Solar terrestrial researches have revealed substantial meaning of nonsteady events on the Sun, mainly solar flares, for the processes taking place in ionosphere. Solar flares result in the numerous consequences, account and prediction of which become necessary in our days. It is well known, that ionospheric disturbances following solar flares cause strong disturbances in the ionosphere, which severely violate radio systems (communication, navigation, etc.). Possibilities of sudden short wave fadeouts (SWF) prediction are considered.

  16. Stochastic Fermi acceleration in solar flares

    NASA Technical Reports Server (NTRS)

    Miller, James A.; Guessoum, Nidhal; Ramaty, Reuven

    1990-01-01

    Proton spectra, valid from non- to ultra-relativistic energies, resulting from stochastic Fermi acceleration in solar flares are calculated. These spectra were obtained by numerically solving the Fokker-Planck equation, in which the escape of the particles from the acceleration region is characterized by an energy-independent escape time. In addition to equilibrium spectra, time-dependent energy spectra showing the approach to equilibrium are also presented. These numerical equilibrium spectra are compared with previous results which were obtained either by Monte Carlo simulations or approximate analytical treatments. There are no analytic solutions valid in the transrelativistic regime, which is very important for the production of pions and neutrons in solar flares. The acceleration efficiency is related to physical parameters, in particular the energy density in either magnetosonic or Alfven waves, and a lower limit is placed on either of these energy densities from acceleration times implied by gamma-ray observations. Also discussed is the physical interpretation of the escape time.

  17. An interacting loop model of solar flare bursts

    NASA Technical Reports Server (NTRS)

    Emslie, A. G.

    1981-01-01

    As a result of the strong heating produced at chromospheric levels during a solar flare burst, the local gas pressure can transiently attain very large values in certain regions. The effectiveness of the surrounding magnetic field at confining this high pressure plasma is therefore reduced and the flaring loop becomes free to expand laterally. In so doing it may drive magnetic field lines into neighboring, nonflaring, loops in the same active region, causing magnetic reconnection to take place and triggering another flare burst. The features of this interacting loop model are found to be in good agreement with the energetics and time structure of flare associated solar hard X-ray bursts.

  18. Energetics of Three Solar Flares Observed by RHESSI

    NASA Technical Reports Server (NTRS)

    Holman, G. D.; Dennis, B. R.; Sui, Linhui

    2004-01-01

    We compare the energy content of the thermal plasma and suprathermal electrons in three solar flares observed by the Ramaty High Energy Solar Spectroscopic Imager (RHESSI). Fits of computed isothermal and thick-target bremsstrahlung spectra to RHESSI X-ray spectra are used to deduce the instantaneous energy content of the X-ray-emitting plasma and the accumulated energy in suprathermal electrons throughout the three flares. We minimize the energy in the suprathermal electrons by assuming that the electron distributions have a low-energy cutoff that is no lower than the highest cutoff energy that provides a good fit to the X-ray spectra. The energetics of the 2002 April 15 M1 flare and the 2002 April 21 X2 flare are computed and compared with results for the 2002 July 23 X5 flare. We find that for all three. flares the energy in nonthermal electrons is comparable to the energy contained in the thermal plasma.

  19. THE 22-YEAR SOLAR MAGNETIC CYCLE. II. FLARE ACTIVITY

    E-print Network

    , inside the solar active regions. It is worth studying this 22-year cycle because of its deep physical of the Regional Meeting on Solar Physics "Solar Researches in the South-Eastern European Countries: Present Magnetic Cycle. II. Flare Activity 49 monitoring is very important not only for solar physics but also

  20. Stochastic acceleration of electrons in solar flares

    NASA Technical Reports Server (NTRS)

    Benz, A. O.; Smith, D. F.

    1987-01-01

    The generation of lower-hybrid waves by cross-field currents is applied to reconnection processes proposed for solar flares. Recent observations on fragmentation of energy release and acceleration, and on hard X-ray (HXR) spectra are taken into account to develop a model for electron acceleration by resonant stochastic interactions with lower-hybrid turbulence. The continuity of the velocity distribution is solved including collisions and escape from the turbulence region. It describes acceleration as a diffusion process in velocity space. The result indicates two regimes that are determined by the energy of the accelerating electrons which may explain the double power-law often observed in HXR spectra. The model further predicts an anticorrelation between HXR flux and spectral index in agreement with observations.

  1. 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.

  2. Flares as fingerprints of inner solar darkness

    E-print Network

    K. Zioutas; M. Tsagri; Y. Semertzidis; T. Papaevangelou

    2008-10-20

    X-ray flares and other solar brightenings have been discarded as potential axion signatures. An axion X-ray signal must appear exclusively near the disk centre, and its spectrum must peak at ~4.2keV, contrary to observation. We argue here that due to Compton scattering off the (plasma) electrons the outward propagation of X-rays from axions converted near the Sun's surface can explain energy distribution and non direcivity. Simulation points at the photosphere as the birth place of the presumed axion conversion, implying an axion rest mass of ~0.01eV. At present, even optimistic parameter values can not reproduce the measured intensities. The simulated photon spectrum peaks at low energies. Quiet Sun hard X-rays are in favour of massive and/or light axion involvement.

  3. 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 protons become superAlfvenic (above about 1 MeV/nucleon), they too can suffer transit-time acceleration by the fast mode waves and will receive an extra acceleration "kick." The basic overall objective of this 1 year effort was to construct a spatially-dependent version of this acceleration model and this has been realized.

  4. Magnetic Energies in Solar Active Regions and Flares Calculated from Automated Coronal Loop Tracing

    NASA Astrophysics Data System (ADS)

    Aschwanden, M. J.

    2014-12-01

    Magnetic energies contained in solar active regions or dissipated in flares can now be calculated from coronal images (such as from AIA/SDO) and line-of-sight magnetograms (such as from HM I/SDO). The magnetogram provides a potential field solution, while automated tracing of coronal loops in different EUV wavelengths provide the misalignment angles between potential field lines and non-potential field lines. We present an automated code that uses data from AIA and HMI to calculate the free energy and dissipated energy in solar flares, based on a nonlinear force-free field approximation in terms of vertical currents that produce helical twists of coronal loops. We study the time evolution of free energy and energy dissipation during some 200 solar flares and compare it with the global energetics of flare and CME energies. The occurrence frequency distributions of dissipated magnetic energies follow closely the predicted powerlaw distribution functions of self-organized criticality models. The presented results provide for the first time statistics on magnetic energies dissipated in solar flares.

  5. Toward Reliable Benchmarking of Solar Flare Forecasting Methods

    NASA Astrophysics Data System (ADS)

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

    2012-03-01

    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.

  6. The chromosphere and transition region. [during solar flare

    NASA Technical Reports Server (NTRS)

    Canfield, R. C.; Brown, J. C.; Craig, I. J. D.; Brueckner, G. E.; Cook, J. W.; Doschek, G. A.; Emslie, A. G.; Machado, M. E.; Henoux, J.-C.; Lites, B. W.

    1980-01-01

    The physical processes occurring as a result of the transfer of energy and momentum from the primary solar flare energy release site in the corona to the underlying chromosphere and transition region during the course of the flare are investigated through a comparison of theoretical models and observational data. Static, dynamic and hydrodynamic models of the lower-temperature chromospheric flare are reviewed. The roles of thermal conduction, radiation, fast particles and mass motion in chromosphere-corona interactions are analyzed on the basis of Skylab UV, EUV and X-ray data, and empirical and synthetic models of the chromospheric and upper photospheric responses to flares are developed. The canonical model of chromospheric heating during flares as a result of primary energy release elsewhere is found to be justified in the chromosphere as a whole, although not entirely as the temperature minimum, and a simplified model of horizontal chromospheric flare structure based on results obtained is presented.

  7. Solar flares in the EUV observed from OSO-5.

    NASA Technical Reports Server (NTRS)

    Kelly, P. T.; Rense, W. A.

    1972-01-01

    Solar flares in three broad EUV spectral bands have been observed from OSO-5 with a grating spectrophotometer. Results are given for three large flares of Mar. 12, Mar. 21 and Apr. 21, 1969. In general, the time dependence of the flare intensity in each band is characterized by a slowly varying component with impulsive bursts superimposed. Bands 2 (465 to 630 A) and 3 (760 to 1030 A) are quite similar in their time variations, but band 1 (280 to 370 A) shows less impulsive structure, and declines more slowly. Absolute EUV intensities for the flares are estimated, and a comparison is made with the 2800 mc/sec radio emission. A flare model is proposed to account for the EUV time variations during a large flare.

  8. Statistical characterization of Strong and Mid Solar Flares and Sun EUV rate monitoring with GNSS

    NASA Astrophysics Data System (ADS)

    Monte-Moreno, Enric; Hernandez-Pajares, Manuel; Garcia-Rigo, Alberto; Beniguel, Yannick; Orus-Perez, Raul; Prieto-Cerdeira, Roberto; Schlueter, Stefan

    2015-04-01

    The global network of permanent Global Navigation Satellite Systems (GNSS) receivers has become an useful and affordable way of monitoring the Solar EUV flux rate, especially -for the time being- in the context of Major and Mid geoeffective intensity Solar Flares (M. Hernandez-Pajares et al., Space Weather, doi:10.1029/2012SW000826, 2012). In fact the maturity of this technique (GNSS Solar FLAre Indicator, GSFLAI) has allowed to incorporate it in operational real-time (RT) conditions, thanks to the availability of global GNSS datastreams from the RT International GNSS Network (M. Caissy et al, GPS World, June 1, 2012), and performed in the context of the MONITOR and MONITOR2 ESA-funded projects (Y. Beniguel et al., NAVITEC Proc., 978-1-4673-2011-5 IEEE, 2012). The main goal of this presentation is to summarize a detailed recent study of the statistical properties of Solar Flares (E. Monte and M. Hernandez-Pajares, J. Geophys. Res., doi:10.1002/2014JA020206, 2014) by considering the GNSS proxy of EUV rate (GSFLAI parameter) computed independently each 30 seconds during the whole last solar cycle. An statistical model has been characterized that explains the empirical results such as (a) the persistence and presence of bursts of solar flares and (b) their long tail peak values of the solar flux variation, which can be characterized by: (1) A fractional Brownian model for the long-term dependence, and (2), a power law distribution for the time series extreme values. Finally, an update of the Solar Flares' occurrence during the recent months of Solar Activity, gathered in RT within MONITOR2 project, will close the paper.

  9. Magnetic Energy and the Cause of Solar Flares

    NSDL National Science Digital Library

    This is a lesson about how magnetism causes solar flares. Learners will set up an electrical circuit with magnets to examine magnetic fields and their similarities to magnetic fields seen on the Sun. Learners should have a conceptual understanding of magnetism prior to exploring this lesson. This activity requires special materials including a galvanometer, copper wire, and sandpaper. This is Activity 2 in the Exploring Magnetism in Solar Flares teachers guide.

  10. Models of the Solar Atmospheric Response to Flare Heating

    NASA Technical Reports Server (NTRS)

    Allred, Joel

    2011-01-01

    I will present models of the solar atmospheric response to flare heating. The models solve the equations of non-LTE radiation hydrodynamics with an electron beam added as a flare energy source term. Radiative transfer is solved in detail for many important optically thick hydrogen and helium transitions and numerous optically thin EUV lines making the models ideally suited to study the emission that is produced during flares. I will pay special attention to understanding key EUV lines as well the mechanism for white light production. I will also present preliminary results of how the model solar atmosphere responds to Fletcher & Hudson type flare heating. I will compare this with the results from flare simulations using the standard thick target model.

  11. 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.

  12. An operational integrated short-term warning solution for solar radiation storms: introducing the Forecasting Solar Particle Events and Flares (FORSPEF) system

    NASA Astrophysics Data System (ADS)

    Anastasiadis, Anastasios; Sandberg, Ingmar; Papaioannou, Athanasios; Georgoulis, Manolis; Tziotziou, Kostas; Jiggens, Piers; Hilgers, Alain

    2015-04-01

    We present a novel integrated prediction system, of both solar flares and solar energetic particle (SEP) events, which is in place to provide short-term warnings for hazardous solar radiation storms. FORSPEF system provides forecasting of solar eruptive events, such as solar flares with a projection to coronal mass ejections (CMEs) (occurrence and velocity) and the likelihood of occurrence of a SEP event. It also provides nowcasting of SEP events based on actual solar flare and CME near real-time alerts, as well as SEP characteristics (peak flux, fluence, rise time, duration) per parent solar event. The prediction of solar flares relies on a morphological method which is based on the sophisticated derivation of the effective connected magnetic field strength (Beff) of potentially flaring active-region (AR) magnetic configurations and it utilizes analysis of a large number of AR magnetograms. For the prediction of SEP events a new reductive statistical method has been implemented based on a newly constructed database of solar flares, CMEs and SEP events that covers a large time span from 1984-2013. The method is based on flare location (longitude), flare size (maximum soft X-ray intensity), and the occurrence (or not) of a CME. Warnings are issued for all > C1.0 soft X-ray flares. The warning time in the forecasting scheme extends to 24 hours with a refresh rate of 3 hours while the respective warning time for the nowcasting scheme depends on the availability of the near real-time data and falls between 15-20 minutes. We discuss the modules of the FORSPEF system, their interconnection and the operational set up. The dual approach in the development of FORPSEF (i.e. forecasting and nowcasting scheme) permits the refinement of predictions upon the availability of new data that characterize changes on the Sun and the interplanetary space, while the combined usage of solar flare and SEP forecasting methods upgrades FORSPEF to an integrated forecasting solution. This work has been funded through the "FORSPEF: FORecasting Solar Particle Events and Flares", ESA Contract No. 4000109641/13/NL/AK

  13. Nonlocal thermal transport in solar flares. II - Spectroscopic diagnostics

    NASA Technical Reports Server (NTRS)

    Karpen, Judith T.; Cheng, Chung-Chieh; Doschek, George A.; Devore, C. Richard

    1989-01-01

    Physical parameters obtained for a flaring solar atmosphere in an earlier paper are used here to predict time-dependent emission-line profiles and integrated intensities as a function of position for two spectral lines commonly observed during solar flares: the X-ray resonance lines of Ca XIX and Mg XI. Considerations of ionization nonequilibrium during the rise phase of the flare are addressed, and the effects on the predicted spectral-line characteristics are discussed. It is concluded that some spectroscopic diagnostics favor the nonlocal model, but other long-standing discrepancies between the numerical models and the observations remain unresolved.

  14. MAGNETIC NONPOTENTIALITY IN PHOTOSPHERIC ACTIVE REGIONS AS A PREDICTOR OF SOLAR FLARES

    SciTech Connect

    Yang Xiao; Lin Ganghua; Zhang Hongqi; Mao Xinjie, E-mail: yangx@nao.cas.cn [Key Laboratory of Solar Activity, National Astronomical Observatories, Chinese Academy of Sciences, 20A Datun Road, Beijing 100012 (China)

    2013-09-10

    Based on several magnetic nonpotentiality parameters obtained from the vector photospheric active region magnetograms obtained with the Solar Magnetic Field Telescope at the Huairou Solar Observing Station over two solar cycles, a machine learning model has been constructed to predict the occurrence of flares in the corresponding active region within a certain time window. The Support Vector Classifier, a widely used general classifier, is applied to build and test the prediction models. Several classical verification measures are adopted to assess the quality of the predictions. We investigate different flare levels within various time windows, and thus it is possible to estimate the rough classes and erupting times of flares for particular active regions. Several combinations of predictors have been tested in the experiments. The True Skill Statistics are higher than 0.36 in 97% of cases and the Heidke Skill Scores range from 0.23 to 0.48. The predictors derived from longitudinal magnetic fields do perform well, however, they are less sensitive in predicting large flares. Employing the nonpotentiality predictors from vector fields improves the performance of predicting large flares of magnitude {>=}M5.0 and {>=}X1.0.

  15. High energy gamma-emission of faint solar flares

    NASA Astrophysics Data System (ADS)

    Arkhangelskaja, Irene; Kotov, Yury; Glyanenko, Alexander; Arkhangelsky, Andrey; Kolchina, Mary; Kirichenko, Alexey

    Hard X-ray and gamma-ray emission in energy band E¿50 keV was first observed by AVS-F apparatus onboard CORONAS-F satellite (detector SONG-D) during some solar flares classes B and C by GOES classification. Such hard component registered in flares with duration less than 30 min. According to AVS-F data about 50High energy gamma-emission up to several tens of MeV was observed during some classes B and C flares, which temporal profiles were not corresponded to Neupert effect. For example, during class B2.3 limb solar flare January 7, 2005 maximum observed energy was Emax 36 MeV and during class B4.6 disk solar flare January 12, 2005 maximum observed energy was Emax 12 MeV. Properties of temporal profiles and energy spectra of faint solar flares, during which high energy gamma-emission were registered discussed in the presented work. There is not any strong correlation between presence or absence of hard X-ray and gamma-ray emission and the intensity of soft X-ray emission during solar flares. It was not observed any statistically significant count rate exceed above background level was during some class M flares, for example, during event November 8, 2001 (class M4.2, flare lasts from 14:59 UT up to 16:00 UT, maximum of soft X-ray emission was at 15:35 UT on GOES data).

  16. Proton versus electron heating in solar flares

    Microsoft Academic Search

    M. Gordovskyy; V. V. Zharkova; Yu. M. Voitenko; M. Goossens

    2005-01-01

    Proton and electron heating of a flaring atmosphere is compared in a kinetic approach for the particles ejected from a non-neutral reconnecting current sheet (RCS) located above the top of reconnected flaring loops in a two-ribbon flare. Two kinds of high-energy particles are considered: particles accelerated by a super-Dreicer electric field and those ejected from the reconnection region as neutral

  17. 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 1044solar microflares to protostellar flares, if the magnetic field strength B of a flare loop is nearly constant for solar and stellar flares. PMID:10534459

  18. Spectral Hardening of Large Solar Flares

    E-print Network

    Paolo C. Grigis; Arnold O. Benz

    2008-05-01

    RHESSI observations are used to quantitatively study the hard X-ray evolution in 5 large solar flares selected for spectral hardening in the course of the event. The X-ray bremsstrahlung emission from non-thermal electrons is characterized by two spectroscopically distinct phases: impulsive and gradual. The impulsive phase usually consists of several emission spikes following a soft-hard-soft spectral pattern, whereas the gradual stage manifests itself as spectral hardening while the flux slowly decreases. Both the soft-hard-soft (impulsive) phase and the hardening (gradual) phase are well described by piecewise linear dependence of the photon spectral index on the logarithm of the hard X-ray flux. The different linear parts of this relation correspond to different rise and decay phases of emission spikes. The temporal evolution of the spectra is compared with the configuration and motion of the hard X-ray sources in RHESSI images. These observations reveal that the two stages of electron acceleration causing these two different behaviors are closely related in space and time. The transition between the impulsive and gradual phase is found to be smooth and progressive rather than abrupt. This suggests that they arise because of a slow change in a common accelerator rather than being caused by two independent and distinct acceleration processes. We propose that the hardening during the decay phase is caused by continuing particle acceleration with longer trapping in the accelerator before escape.

  19. Predicting Arrival Of Protons Emitted In Solar Flares

    NASA Technical Reports Server (NTRS)

    Spagnuolo, John N., Jr.; Schwuttke, Ursula M.; Han, Cecilia S.; Hervias, Felipe

    1996-01-01

    Visual Utility for Localization of Corona Accelerated Nuclei (VULCAN) computer program provides both advance warnings and insight for post-event analyses of effects of solar flares. Using measurements of peak fluxes, times of detection, flare location, solar wind velocities, and x-ray emissions from Sun, as electronically sent by NOAA (National Oceanographic and Atmospheric Administration), VULCAN predicts resulting intensities of proton fluxes at various user-chosen points (spacecraft or planets) of solar system. Also predicts times of onset of fluxes of protons and peak values of fluxes.

  20. Imaging coronal magnetic-field reconnection in a solar flare

    NASA Astrophysics Data System (ADS)

    Su, Yang; Veronig, Astrid M.; Holman, Gordon D.; Dennis, Brian R.; Wang, Tongjiang; Temmer, Manuela; Gan, Weiqun

    2013-08-01

    Magnetic-field reconnection is believed to play a fundamental role in magnetized plasma systems throughout the Universe, including planetary magnetospheres, magnetars and accretion disks around black holes. This letter presents extreme ultraviolet and X-ray observations of a solar flare showing magnetic reconnection with a level of clarity not previously achieved. The multi-wavelength extreme ultraviolet observations from SDO/AIA show inflowing cool loops and newly formed, outflowing hot loops, as predicted. RHESSI X-ray spectra and images simultaneously show the appearance of plasma heated to >10MK at the expected locations. These two data sets provide solid visual evidence of magnetic reconnection producing a solar flare, validating the basic physical mechanism of popular flare models. However, new features are also observed that need to be included in reconnection and flare studies, such as three-dimensional non-uniform, non-steady and asymmetric evolution.

  1. 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.

  2. Observations and interpretation of solar flares at microwave frequencies

    Microsoft Academic Search

    C. J. Crannell; G. A. Dulk; T. Kosugi; A. Magun

    1988-01-01

    The physical processes responsible for microwave emission in solar flares are outlined, and examples of how microwave observations have been interpreted in terms of physical parameters are described. Selected results obtained during Solar Cycle 21 with the microwave observatories dedicated to synoptic observations of the Sun are summarized. The status and future plans for these facilities at Bern and in

  3. Solar flare neutron fluxes derived from interplanetary charged particle measurements

    Microsoft Academic Search

    P. Evenson; R. Kroeger; P. Meyer; D. Muller

    1983-01-01

    The first observation of interplanetary protons produced by the decay of solar neutrons made by Evenson et al. (1983) after a solar flare which occurred on June 3, 1982, is expanded, extending the measurement of the spectrum of the decay protons to higher energy. The spectrum of the decay protons for the June 21, 1980, neutron event observed by Chupp

  4. Critical Issues For Understanding Particle Acceleration in Impulsive Solar Flares

    Microsoft Academic Search

    James A. Miller; Peter J. Cargill; A. Gordon Emslie; Gordon D. Holman; Brian R. Dennis; Ted N. La Rosa; Robert M. Winglee; Stephen G. Benka; S. Tsuneta

    1997-01-01

    This paper, a review of the present status of existing models for particle acceleration during impulsive solar flares, was inspired by a week-long workshop held in the Fall of 1993 at NASA Goddard Space Flight Center. Recent observations from Yohkoh and the Compton Gamma Ray Observatory, and a reanalysis of older observations from the Solar Maximum Mission, have led to

  5. Solar Flare Effects on the Thermosphere and Ionosphere

    NASA Astrophysics Data System (ADS)

    Solomon, S.; Qian, L.; Rodgers, E.; Bailey, S.

    The Solar Extreme-ultraviolet Experiment SEE on the TIMED satellite and by the X-ray Photometer System XPS on the SORCE satellite provide the first comprehensive irradiance measurements of the complete solar spectrum during large solar flares However the soft X-ray portion of these observations are performed using silicon photodiodes coated with metallic filters to provide photometric measurements with multiple band passes which leads to complexities in obtaining spectral information A new analysis technique developed specifically for flare conditions is used to infer flare spectra in this region These are combined with spectrographic measurements in the extreme ultraviolet and far ultraviolet and applied to the NCAR Thermosphere-Ionosphere-Electrodynamics General Circulation Model TIE-GCM The electron content neutral density and airglow response to large flares during the declining phase of solar cycle 23 are calculated using this model and compared to several measurement sets obtaining good agreement This supports both the validity of the solar X-ray analysis and the modeling methodology showing that although flare-driven effects in the upper atmosphere are significant they are shorter and of much smaller magnitude than geomagnetic disturbances

  6. SOLAR CYCLE VARIATIONS OF THE OCCURRENCE OF CORONAL TYPE III RADIO BURSTS AND A NEW SOLAR ACTIVITY INDEX

    SciTech Connect

    Lobzin, Vasili; Cairns, Iver H.; Robinson, Peter A. [School of Physics, University of Sydney, New South Wales (Australia)

    2011-07-20

    This Letter presents the results of studies of solar cycle variations of the occurrence rate of coronal type III radio bursts. The radio spectra are provided by the Learmonth Solar Radio Observatory (Western Australia), part of the USAF Radio Solar Telescope Network (RSTN). It is found that the occurrence rate of type III bursts strongly correlates with solar activity. However, the profiles for the smoothed type III burst occurrence rate differ considerably from those for the sunspot number, 10.7 cm solar radio flux, and solar flare index. The type III burst occurrence rate (T3BOR) is proposed as a new index of solar activity. T3BOR provides complementary information about solar activity and should be useful in different studies including solar cycle predictions and searches for different periodicities in solar activity. This index can be estimated from daily results of the Automated Radio Burst Identification System. Access to data from other RSTN sites will allow processing 24 hr radio spectra in near-real time and estimating true daily values of this index. It is also shown that coronal type III bursts can even occur when there are no visible sunspots on the Sun. However, no evidence is found that the bursts are not associated with active regions. It is also concluded that the type III burst productivity of active regions exhibits solar cycle variations.

  7. TRANSITION REGION EMISSION FROM SOLAR FLARES DURING THE IMPULSIVE PHASE

    SciTech Connect

    Johnson, H.; Raymond, J. C.; Murphy, N. A.; Suleiman, R. [Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge, MA 02138 (United States); Giordano, S. [INAF-Osservatorio Astronomico di Torino, via Osservatorio 20, 10025 Pino Torinese (Italy); Ko, Y.-K. [Space Science Division, Naval Research Laboratory, Washington, DC 20375 (United States); Ciaravella, A. [INAF-Osservatorio Astronomico di Palermo, P.za Parlamento 1, 90134 Palermo (Italy)

    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.

  8. X1.6 Class Solar Flare on Sept. 10, 2014 - Duration: 37 seconds.

    NASA Video Gallery

    An X1.6 class solar flare flashes in the middle of the sun on Sept. 10, 2014. These images were captured by NASA's Solar Dynamics Observatory. It first shows the flare in the 171 Angstrom wavelengt...

  9. Oblique Shocks in the Reconnection Jet in Solar Flares

    NASA Astrophysics Data System (ADS)

    Tanuma, S.; Shibata, K.

    2007-10-01

    The strong hard X-ray emission of energetic electrons is observed in some solar flares. The origin of energetic electrons is, however, not known fully. Then, we suggest that the internal shocks are created in the reconnection jet in solar flares, and that energetic electrons are accelerated by the shocks. In this paper, we examine 2D MHD simulations of magnetic reconnection with a high spatial resolution. As the results, the magnetic reconnection occurs after the secondary tearing instability at the current sheet. We find that, during the non-steady Petschek reconnection, the oblique strong shocks are created by the Kelvin-Helmholtz-like instability in the reconnection jet when we assume an anomalous resistivity model. The oblique shocks can be possible sites of the particle acceleration in the solar flares.

  10. Oblique Shocks in the Magnetic Reconnection Jet in Solar Flares

    NASA Astrophysics Data System (ADS)

    Tanuma, Syuniti; Shibata, Kazunari

    2007-04-01

    Strong radio emission of energetic electrons is observed in some solar flares. The origin of energetic electrons is, however, not fully known. In this letter we suggest that oblique shocks are created in reconnection jets in solar flares, and that energetic electrons are accelerated by shocks. We examine 2D MHD simulations of magnetic reconnection with high spacial resolution by assuming an anomalous resistivity model. As a result, magnetic reconnection is found to occur after a secondary tearing instability at the current sheet. We find that, during nonsteady Petschek reconnection, oblique shocks are created by an even mode of the Kelvin-Helmholtz-like instability in the reconnection jet when we assume an anomalous resistivity model. Furthermore, bursty, time-dependent reconnection ejects many plasmoids from the diffusion region, and creates shocks. We suggest that these shocks can be possible sites of particle acceleration in solar flares.

  11. Common SphinX and RHESSI observations of solar flares

    NASA Astrophysics Data System (ADS)

    Mrozek, T.; Gburek, S.; Siarkowski, M.; Sylwester, B.; Sylwester, J.; Gryciuk, M.

    The Polish X-ray spectrofotometer SphinX has observed a great number of solar flares in the year 2009 - during the most quiet solar minimum almost over the last 100 years. Hundreds of flares have been recorded due to excellent sensitivity of SphinX's detectors. The Si-PIN diodes are about 100 times more sensitive to X-rays than GOES X-ray Monitors. SphinX detectors were absolutely calibrated on Earth with a use of the BESSY synchrotron. In space observations were made in the range 1.2-15~keV with 480~eV energy resolution. SphinX data overlap with the low-energy end of the Ramaty High Energy Solar Spectroscopic Imager (RHESSI) data. RHESSI detectors are quite old (7 years in 2009), but still sensitive enough to provide us with observations of extremely weak solar flares such as those which occurred in 2009. We have selected a group of flares simultaneously observed by RHESSI and SphinX and performed a spectroscopic analysis of the data. Moreover, we compared the physical parameters of these flares plasma. Preliminary results of the comparison show very good agreement between both instruments.

  12. Solar Flare Intermittency and the Earth's Temperature Anomalies Nicola Scafetta1,2

    E-print Network

    Scafetta, Nicola

    Solar Flare Intermittency and the Earth's Temperature Anomalies Nicola Scafetta1,2 and Bruce J; published 17 June 2003) We argue that Earth's short-term temperature anomalies and the solar flare data sets that corresponds to the one that would be induced by the solar flare intermittency. The mean

  13. Solar flares as cascades of reconnecting magnetic loops.

    PubMed

    Hughes, D; Paczuski, M; Dendy, R O; Helander, P; McClements, K G

    2003-04-01

    A model for the solar coronal magnetic field is proposed where multiple directed loops evolve in space and time. Loops injected at small scales are anchored by footpoints of opposite polarity moving randomly on a surface. Nearby footpoints of the same polarity aggregate, and loops can reconnect when they collide. This may trigger a cascade of further reconnection, representing a solar flare. Numerical simulations show that a power law distribution of flare energies emerges, associated with a scale-free network of loops, indicating self-organized criticality. PMID:12689272

  14. PLASMA HEATING IN THE VERY EARLY PHASE OF SOLAR FLARES

    SciTech Connect

    Siarkowski, M. [Space Research Centre, Polish Academy of Sciences, 51-622 Wroclaw, ul. Kopernika 11 (Poland); Falewicz, R.; Rudawy, P., E-mail: ms@cbk.pan.wroc.p, E-mail: falewicz@astro.uni.wroc.p, E-mail: rudawy@astro.uni.wroc.p [Astronomical Institute, University of Wroclaw, 51-622 Wroclaw, ul. Kopernika 11 (Poland)

    2009-11-10

    In this Letter, we analyze soft X-ray (SXR) and hard X-ray (HXR) emission of the 2002 September 20 M1.8 GOES class solar flare observed by the RHESSI and GOES satellites. In this flare event, SXR emission precedes the onset of the main bulk HXR emission by approx5 minutes. This suggests that an additional heating mechanism may be at work at the early beginning of the flare. However, RHESSI spectra indicate a presence of the non-thermal electrons also before the impulsive phase. So, we assumed that a dominant energy transport mechanism during the rise phase of solar flares is electron-beam-driven evaporation. We used non-thermal electron beams derived from RHESSI spectra as the heating source in a hydrodynamic model of the analyzed flare. We showed that energy delivered by non-thermal electron beams is sufficient to heat the flare loop to temperatures in which it emits SXR closely following the GOES 1-8 A light curve. We also analyze the number of non-thermal electrons, the low-energy cutoff, electron spectral indices, and the changes of these parameters with time.

  15. Plausible mechanisms for rapid acceleration of protons during solar flares

    NASA Technical Reports Server (NTRS)

    Bai, T.

    1983-01-01

    The distinctive physical features of 20 gamma-ray line flares observed during Solar Maximum Mission are discussed. The average energy deposition by nonthermal electrons in the impulsive phase of the flare event of April 27, 1980 is calculated, on the basis of spectral data from the Hinotori satellite. Analysis of the hard X-ray spectral evolution of the flare events of June 21, 1980 and April 27, 1981, showed a very hot (about 10 to the 8th K) thermal component with an emission measure of 3 x 10 to the 47th per cu cm. Some possible mechanisms for the particle acceleration observed during the flare events are discussed, including: the delay of high-energy hard X-rays; first-order Fermi acceleration by shocks propagating in a closed flare loop; and the compression of accelerated particles by upstream and downstream scattering centers around a shock front. In addition to the above mechanisms, sotchastic acceleration by turbulence is identified as a possible mechanism for rapid proton acceleration during solar flare events.

  16. Solar cosmic ray, solar wind, solar flare, and neutron albedo measurements, part C

    NASA Technical Reports Server (NTRS)

    Burnett, D.; Hohenberg, C.; Maurette, M.; Monnin, M.; Walker, R.; Wollum, D.

    1972-01-01

    All mineral detectors exposed on Apollo 16 had high surface track densities probably produced by a solar flare that occurred during the mission. The heavy ions followed a power law spectrum with exponent approximately 3 down to approximately 200 KeV/nucleon. The abundance of low-energy particle tracks observed in this flare may explain the high track densities observed in lunar dust grains. Pristine heavy-particle tracks in feldspar give long tracks. Shallow pits similar to those expected from extremely heavy solar wind ions were observed in about the expected number. Initial results give a low apparent value of neutron albedo relative to theory.

  17. Variability of Thermosphere and Ionosphere Responses to Solar Flares

    NASA Technical Reports Server (NTRS)

    Qian, Liying; Burns, Alan G.; Chamberlin, Philip C.; Solomon, Stanley C.

    2011-01-01

    We investigated how the rise rate and decay rate of solar flares affect the thermosphere and ionosphere responses to them. Model simulations and data analysis were conducted for two flares of similar magnitude (X6.2 and X5.4) that had the same location on the solar limb, but the X6.2 flare had longer rise and decay times. Simulated total electron content (TEC) enhancements from the X6.2 and X5.4 flares were 6 total electron content units (TECU) and approximately 2 TECU, and the simulated neutral density enhancements were approximately 15% -20% and approximately 5%, respectively, in reasonable agreement with observations. Additional model simulations showed that for idealized flares with the same magnitude and location, the thermosphere and ionosphere responses changed significantly as a function of rise and decay rates. The Neupert Effect, which predicts that a faster flare rise rate leads to a larger EUV enhancement during the impulsive phase, caused a larger maximum ion production enhancement. In addition, model simulations showed that increased E x B plasma transport due to conductivity increases during the flares caused a significant equatorial anomaly feature in the electron density enhancement in the F region but a relatively weaker equatorial anomaly feature in TEC enhancement, owing to dominant contributions by photochemical production and loss processes. The latitude dependence of the thermosphere response correlated well with the solar zenith angle effect, whereas the latitude dependence of the ionosphere response was more complex, owing to plasma transport and the winter anomaly.

  18. GEOMAGNETIC CONSEQUENCES OF THE SOLAR FLARES DURING THE LAST HALE SOLAR CYCLE (II)

    E-print Network

    radiation. The results are of a high interest not only for solar physics but also for otherGEOMAGNETIC CONSEQUENCES OF THE SOLAR FLARES DURING THE LAST HALE SOLAR CYCLE (II) Georgeta Maris@aira.astro.ro ABSTRACT/RESUME The effects of the solar energetic phenomena cover the entire terrestrial environment, from

  19. The Quasi-periodic Occurrence of Solar Radio Bursts, Auroral Kilometric Radiation, and Other Plasma Wave Phenomena Observed by the GEOTAIL Plasma Wave Investigation

    Microsoft Academic Search

    R. R. Anderson; I. Nagano; S. Yagitani; H. Matsumoto; K. Hashimoto; H. Kojima; H. Takano

    2004-01-01

    Type III solar radio bursts and auroral kilometric radiation (AKR) are among the most common phenomena observed by the GEOTAIL Plasma Wave Investigation in more than eleven years of operation. The occurrence of Type III bursts, generated in the solar wind by energetic electrons ejected from the sun by solar flares, varies from less than one per day to nearly

  20. Proton versus electron heating in solar flares

    Microsoft Academic Search

    Yu. M. Voitenko; V. V. Zharkova; M. Gordovskyy

    2004-01-01

    Recently we have reported that protons and electrons accelerated by super Dreicer electric feld in a current sheet with non-zero guiding magnetic field are ejected into different legs of a flaring loop either separately or as partially neutralized beams. This particle separation at ejection may have consequences onto the particle precipitation scenarios depending on electron versus proton abundances, energy and

  1. Low energy particle composition. [energy spectra, particle emission - solar flares

    NASA Technical Reports Server (NTRS)

    Gloeckler, G.

    1975-01-01

    The energy spectra and composition of the steady or 'quiet-time' particle flux, whose origin is unknown was studied. Particles and photons which are associated with solar flares or active regions on the sun were also studied. Various detection techniques used to measure the composition and energy spectra of low energy particles are discussed. Graphs of elemental abundance and energy spectra are given.

  2. Magnetic shielding of interplanetary spacecraft against solar flare radiation

    Microsoft Academic Search

    Franklin H. Cocks; Seth Watkins

    1993-01-01

    The ultimate objective of this work is to design, build, and fly a dual-purpose, piggyback payload whose function is to produce a large volume, low intensity magnetic field and to test the concept of using such a magnetic field (1) to protect spacecraft against solar flare protons, (2) to produce a thrust of sufficient magnitude to stabilize low satellite orbits

  3. Fuzzy forecast of flood disaster caused by solar proton flares

    Microsoft Academic Search

    Zhengzhong Han; Yuhua Tang

    1999-01-01

    The flood disaster caused by solar proton flares is forecasted using the theory of fuzzy mathematics. The index system and standards of fuzzy evaluation, as well as the membership function are proposed. A practical software of computer data processing for forecasting flood disaster is given.

  4. The Solar Flare: A Strongly Turbulent Particle Accelerator

    E-print Network

    California at Berkeley, University of

    Chapter 5 The Solar Flare: A Strongly Turbulent Particle Accelerator L. Vlahos, S. Krucker, and P) and particle acceleration during such an event are rarely discussed together in the same article. Many the topic of particle acceleration is often presented as an addi- tional complication to be addressed

  5. Particle acceleration in solar flares: observations versus numerical simulations

    E-print Network

    Particle acceleration in solar flares: observations versus numerical simulations A O Benz, P C processes such as isotropization and magnetic trapping are made. Keywords: Particle acceleration, hard X. As the electric field of reconnection with possible parallel component capable of particle acceleration is limited

  6. Massively Parallel Simulations of Solar Flares and Plasma Turbulence

    E-print Network

    Grauer, Rainer

    Massively Parallel Simulations of Solar Flares and Plasma Turbulence Lukas Arnold, Christoph Beetz simulations need an efficient parallel implementation. We will describe the physics behind these problems and present the numerical frameworks for solving these problems on massive parallel computers. 1 Introduction

  7. Max '91: Flare research at the next solar maximum

    NASA Technical Reports Server (NTRS)

    Dennis, Brian; Canfield, Richard; Bruner, Marilyn; Emslie, Gordon; Hildner, Ernest; Hudson, Hugh; Hurford, Gordon; Lin, Robert; Novick, Robert; Tarbell, Ted

    1988-01-01

    To address the central scientific questions surrounding solar flares, coordinated observations of electromagnetic radiation and energetic particles must be made from spacecraft, balloons, rockets, and ground-based observatories. A program to enhance capabilities in these areas in preparation for the next solar maximum in 1991 is recommended. The major scientific issues are described, and required observations and coordination of observations and analyses are detailed. A program plan and conceptual budgets are provided.

  8. High energy observations of June 1980 solar flares

    Microsoft Academic Search

    B. Lokanadham; P. K. Subramanian; A. L. Kiplinger; B. R. Dennis

    1986-01-01

    The paper presents a detailed study of the high energy X-ray observations of the most unusual solar events observed on 4 and 7 June, 1980 with the Hard X-Ray Burst Spectrometer (HXRBS) on Solar Maximum Mission (SMM) satellite. The hard X-ray data of the events are also compared with the radio microwave fluxes. The X-ray time profiles of these flares

  9. Impulsive Heating of Solar Flare Ribbons Above 10 MK

    NASA Astrophysics Data System (ADS)

    Simões, P. J. A.; Graham, D. R.; Fletcher, L.

    2015-06-01

    The chromospheric response to the input of flare energy is marked by extended extreme ultraviolet (EUV) ribbons and hard X-ray (HXR) footpoints. These are usually explained as the result of heating and bremsstrahlung emission from accelerated electrons colliding in the dense chromospheric plasma. We present evidence of impulsive heating of flare ribbons above 10 MK in a two-ribbon flare. We analyse the impulsive phase of SOL2013-11-09T06:38, a C2.6 class event using data from Atmospheric Imaging Assembly (AIA) on board of the Solar Dynamics Observatory (SDO) and the Reuven Ramaty High Energy Solar Spectroscopic Imager (RHESSI) to derive the temperature, emission measure and differential emission measure of the flaring regions and investigate the evolution of the plasma in the flaring ribbons. The ribbons were visible at all SDO/AIA EUV/UV wavelengths, in particular, at 94 and 131 Å filters, sensitive to temperatures of 8 MK and 12 MK. The time evolution of the emission measure of the plasma above 10 MK at the ribbons has a peak near the HXR peak time. The presence of hot plasma in the lower atmosphere is further confirmed by a RHESSI imaging spectroscopy analysis, which shows resolved sources at 11 - 13 MK that are associated with at least one ribbon. We found that collisional beam-heating can only marginally explain the power necessary to heat the 10 MK plasma at the ribbons.

  10. NEW SOLAR EXTREME-ULTRAVIOLET IRRADIANCE OBSERVATIONS DURING FLARES

    SciTech Connect

    Woods, Thomas N.; Hock, Rachel; Eparvier, Frank; Jones, Andrew R. [Laboratory for Atmospheric and Space Physics, University of Colorado, Boulder, CO 80303 (United States); Chamberlin, Phillip C.; Klimchuk, James A. [NASA Goddard Space Flight Center, Solar Physics Laboratory, Greenbelt, MD 20771 (United States); Didkovsky, Leonid; Judge, Darrell [Space Sciences Center, University of Southern California, Los Angeles, CA 90089 (United States); Mariska, John; Warren, Harry [Space Science Division, Naval Research Laboratory, Washington, DC 20375 (United States); Schrijver, Carolus J. [Lockheed Martin Solar and Astrophysics Laboratory, Palo Alto, CA 94304 (United States); Webb, David F. [Institute for Scientific Research, Boston College, Chestnut Hill, MA 02467 (United States); Bailey, Scott [Electrical and Computer Engineering Department, Virginia Tech, Blacksburg, VA 24061 (United States); Tobiska, W. Kent, E-mail: tom.woods@lasp.colorado.edu [Space Environment Technologies, Pacific Palisades, CA 90272 (United States)

    2011-10-01

    New solar extreme-ultraviolet (EUV) irradiance observations from the NASA Solar Dynamics Observatory (SDO) EUV Variability Experiment provide full coverage in the EUV range from 0.1 to 106 nm and continuously at a cadence of 10 s for spectra at 0.1 nm resolution and even faster, 0.25 s, for six EUV bands. These observations can be decomposed into four distinct characteristics during flares. First, the emissions that dominate during the flare's impulsive phase are the transition region emissions, such as the He II 30.4 nm. Second, the hot coronal emissions above 5 MK dominate during the gradual phase and are highly correlated with the GOES X-ray. A third flare characteristic in the EUV is coronal dimming, seen best in the cool corona, such as the Fe IX 17.1 nm. As the post-flare loops reconnect and cool, many of the EUV coronal emissions peak a few minutes after the GOES X-ray peak. One interesting variation of the post-eruptive loop reconnection is that warm coronal emissions (e.g., Fe XVI 33.5 nm) sometimes exhibit a second large peak separated from the primary flare event by many minutes to hours, with EUV emission originating not from the original flare site and its immediate vicinity, but rather from a volume of higher loops. We refer to this second peak as the EUV late phase. The characterization of many flares during the SDO mission is provided, including quantification of the spectral irradiance from the EUV late phase that cannot be inferred from GOES X-ray diagnostics.

  11. Muon and Tau Neutrinos Spectra from Solar Flares

    NASA Astrophysics Data System (ADS)

    Fargion, Daniele; Moscato, Federica

    2003-12-01

    Most power-full solar flare as the ones occurred on 23th February 1956, September 29th 1989, 28th October and on 2nd-4th November 2003 are sources of cosmic rays, X, gamma and neutrino bursts. These flares took place both on front or in the edge and in the hidden solar disk. The 4th November event was the most powerful X event in the highest known rank category X28 just at horizons. The observed and estimated total flare energy (EFL ? 1031div 1033 erg) should be a source 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 by the solar charged flare particles reaching the terrestrial atmosphere. These first earliest prompt solar neutrino burst might be observed, in a few neutrino clustered events, in present or future largest neutrino underground detectors as Super-Kamiokande one, in time correlation with the X-Radio flare. The onset in time correlation has great statistical significance. Our first estimate on the neutrino number events detection at the Super-Kamiokande II Laboratory for horizontal or hidden flare is found to be few events: NeV_bar{?}_e? 0.63&etae ()/(35 MeV) ()/(1031 erg); and NeV_bar{?}? ? 3.58()/(200 MeV) ()/(1031erg) ?,SUB>?, where ?? 1, E?? > 113 MeV. Our first estimates of neutrino signals in largest underground detectors hint for few events in correlation with X, gamma, radio onser. Our approximated spectra for muons and taus from these rare solar eruption are shown over the most common background. The muon and tau signature is very peculiar and characteristic over electron and anti-electron neutrino fluxes. The rise of muon neutrinos will be detectable above the minimal muon threshold E? ? 113 MeV energy, or above the pion and ? ° thresholds (E?? 151 and 484 MeV). Any large neutrino flare event record might also verify the expected neutrino flavour mixing leading to a few as well as a comparable, ?e, ??, bar{?}e, bar{?}? energy fluence and spectra. The rarest tau appearance will be possible only for hardest solar neutrino energies above 3.471 GeV.

  12. Measurements and Modeling of Total Solar Irradiance in X-class Solar Flares

    NASA Technical Reports Server (NTRS)

    Moore, Christopher S.; Chamberlin, Phillip Clyde; Hock, Rachel

    2014-01-01

    The Total Irradiance Monitor (TIM) from NASA's SOlar Radiation and Climate Experiment can detect changes in the total solar irradiance (TSI) to a precision of 2 ppm, allowing observations of variations due to the largest X-class solar flares for the first time. Presented here is a robust algorithm for determining the radiative output in the TIM TSI measurements, in both the impulsive and gradual phases, for the four solar flares presented in Woods et al., as well as an additional flare measured on 2006 December 6. The radiative outputs for both phases of these five flares are then compared to the vacuum ultraviolet (VUV) irradiance output from the Flare Irradiance Spectral Model (FISM) in order to derive an empirical relationship between the FISM VUV model and the TIM TSI data output to estimate the TSI radiative output for eight other X-class flares. This model provides the basis for the bolometric energy estimates for the solar flares analyzed in the Emslie et al. study.

  13. Measurements and Modeling of Total Solar Irradiance in X-class Solar Flares

    NASA Astrophysics Data System (ADS)

    Moore, Christopher Samuel; Chamberlin, Phillip Clyde; Hock, Rachel

    2014-05-01

    The Total Irradiance Monitor (TIM) from NASA's SOlar Radiation and Climate Experiment can detect changes in the total solar irradiance (TSI) to a precision of 2 ppm, allowing observations of variations due to the largest X-class solar flares for the first time. Presented here is a robust algorithm for determining the radiative output in the TIM TSI measurements, in both the impulsive and gradual phases, for the four solar flares presented in Woods et al., as well as an additional flare measured on 2006 December 6. The radiative outputs for both phases of these five flares are then compared to the vacuum ultraviolet (VUV) irradiance output from the Flare Irradiance Spectral Model (FISM) in order to derive an empirical relationship between the FISM VUV model and the TIM TSI data output to estimate the TSI radiative output for eight other X-class flares. This model provides the basis for the bolometric energy estimates for the solar flares analyzed in the Emslie et al. study.

  14. Measurements and modeling of total solar irradiance in X-class solar flares

    SciTech Connect

    Moore, Christopher Samuel [Center for Astrophysics and Space Astronomy, University of Colorado, UCB 389, Boulder, CO 80309 (United States); Chamberlin, Phillip Clyde [Solar Physics Laboratory, NASA Goddard Space Flight Center, Greenbelt, MD 20771 (United States); Hock, Rachel [Space Vehicle Directorate, Air Force Research Laboratory, Kirtland Air Force Base, NM 87117 (United States)

    2014-05-20

    The Total Irradiance Monitor (TIM) from NASA's SOlar Radiation and Climate Experiment can detect changes in the total solar irradiance (TSI) to a precision of 2 ppm, allowing observations of variations due to the largest X-class solar flares for the first time. Presented here is a robust algorithm for determining the radiative output in the TIM TSI measurements, in both the impulsive and gradual phases, for the four solar flares presented in Woods et al., as well as an additional flare measured on 2006 December 6. The radiative outputs for both phases of these five flares are then compared to the vacuum ultraviolet (VUV) irradiance output from the Flare Irradiance Spectral Model (FISM) in order to derive an empirical relationship between the FISM VUV model and the TIM TSI data output to estimate the TSI radiative output for eight other X-class flares. This model provides the basis for the bolometric energy estimates for the solar flares analyzed in the Emslie et al. study.

  15. Acceleration of runaway electrons and Joule heating in solar flares

    NASA Technical Reports Server (NTRS)

    Holman, G. D.

    1984-01-01

    The electric field acceleration of electrons out of a thermal plasma and the simultaneous Joule heating of the plasma are studied. Acceleration and heating timescales are derived and compared, and upper limits are obtained on the acceleration volume and the rate at which electrons can be accelerated. These upper limits, determined by the maximum magnetic field strength observed in flaring regions, place stringent restrictions upon the acceleration process. The role of the plasma resistivity in these processes is examined, and possible sources of anomalous resistivity are summarized. The implications of these results for the microwave and hard X-ray emission from solar flares are examined.

  16. Effects of solar flares on the ionosphere of Mars.

    PubMed

    Mendillo, Michael; Withers, Paul; Hinson, David; Rishbeth, Henry; Reinisch, Bodo

    2006-02-24

    All planetary atmospheres respond to the enhanced x-rays and ultraviolet (UV) light emitted from the Sun during a flare. Yet only on Earth are observations so continuous that the consequences of these essentially unpredictable events can be measured reliably. Here, we report observations of solar flares, causing up to 200% enhancements to the ionosphere of Mars, as recorded by the Mars Global Surveyor in April 2001. Modeling the altitude dependence of these effects requires that relative enhancements in the soft x-ray fluxes far exceed those in the UV. PMID:16497929

  17. Low-latitude Ionospheric Heating during Solar Flares

    NASA Astrophysics Data System (ADS)

    Klenzing, J.; Chamberlin, P. C.; Qian, L.; Haaser, R. A.; Burrell, A. G.; Earle, G. D.; Heelis, R. A.; Simoes, F. A.

    2013-12-01

    The advent of the Solar Dynamics Observatory (SDO) represents a leap forward in our capability to measure rapidly changing transient events on the sun. SDO measurements are paired with the comprehensive low latitude measurements of the ionosphere and thermosphere provided by the Communication/Navigation Outage Forecast System (C/NOFS) satellite and state-of-the-art general circulation models to discuss the coupling between the terrestrial upper atmosphere and solar radiation. Here we discuss ionospheric heating as detected by the Coupled Ion-Neutral Dynamics Investigation (CINDI) instrument suite on the C/NOFS satellite during solar flares. Also discusses is the necessity of decoupling the heating due to increased EUV irradiance and that due to geomagnetic storms, which sometimes occur with flares. Increases in both the ion temperature and ion density in the subsolar topside ionosphere are detected within 77 minutes of the 23 Jan 2012 M-class flare, and the observed results are compared with the Thermosphere-Ionosphere-Mesosphere-Electrodynamics General Circulation Model (TIME-GCM) using the Flare Irradiance Spectral Model (FISM) as an input.

  18. A comparison between statistical properties of solar X-ray flares and avalanche predictions in cellular automata statistical flare models

    Microsoft Academic Search

    M. K. Georgoulis; N. Vilmer; N. B. Crosby

    2001-01-01

    We perform a tentative comparison between the statistical properties of cellular automata statistical flare models including a highly variable non-linear external driver and the respective properties of the WATCH flare data base, constructed during the maximum of solar cycle 21. The model is based on the concept of Self-Organized Criticality (SOC). The frequency distributions built on the measured X-ray flare

  19. Statistical analysis of thermospheric and ionospheric response to solar flares in solar cycle 23

    NASA Astrophysics Data System (ADS)

    Le, Huijun; Liu, Libo; Chen, Yiding; Wan, Weixing

    2013-04-01

    In the present study, we first explored the thermospheric response to all X-class solar flares during 2001-2006 by analyzing CHAMP and GRACE measurements. The observed results show that X5 and stronger solar flares can induce an average enhancement of 10-13% in thermospheric density in latitude 50°S-50°N within ~4 hours after the flare onset. Many important lines and continua in solar EUV region are optically thick, thus EUV enhancements are smaller for flares located near the solar limb due to absorption by the solar atmosphere. Limb flares induce smaller thermospheric responses, due to the limb effect of solar EUV. The thermospheric density enhancement is much more correlated with integrated EUV flux than with peak EUV flux, with a high correlation coefficient of 0.91, which suggests that thermospheric response is strongly dependent on the total integrated energy into the thermosphere. Then we studied the ionospheric responses to solar flares during 1999-2006 by using the GOES 0.1-0.8nm X-ray, 26-34nm EUV, and GPS/TEC in the worldwide. The statistical results show the TEC enhancements are highly related to the solar zenith angle (SZA). The smaller SZA would result in the greater TEC responses. The TEC response is not highly related with the X-ray flux (the correlation coefficient 0.6), which is due to that the ionospheric response is not only related to the X-ray flux level, but also related to the flare location on solar disc. The limb flare has less effect on the ionosphere than the central flare. The reason for this is that the main ionization source EUV flux has such flare location dependence. The statistical results show that the flare location effect decreases with decreasing flare X-ray class. The results also show that the TEC enhancement does not linearly increase with X-ray flux. Its uprising amplitude increases with X-ray flux. The TEC response also has slight latitude dependence: it decrease with latitude. And the TEC response has significant seasonal dependence. The maximum response occurred at equinox and the minimum response at summer.

  20. Signatures of current loop coalescence in solar flares

    NASA Technical Reports Server (NTRS)

    Sakai, J.; Nakajima, H.; Zaidman, E.; Tajima, T.; Kosugi, T.; Brunel, F.

    1986-01-01

    The nonlinear coalescence instability of current carrying solar loops can explain many of the characteristics of the solar flares such as their impulsive nature, heating and high energy particle acceleration, amplitude oscillations of electromagnetic emission as well as the characteristics of 2-D microwave images obtained during a solar flare. The physical characteristics of the explosive coalescence of currents are presented in detail through computer simulation and theory. Canonical characteristics of the explosive coalescence are: (1) a large amount of impulsive increase of kinetic energies of electrons and ions; (2) simultaneous heating and acceleration of electrons and ions in high and low energy spectra; (3) ensuing quasi-periodic amplitude oscillations in fields and particle quantities; and (4) the double peak (or triple peak) structure in these profiles, participate in the coalescence process, yielding varieties of phenomena.

  1. Automated Feature Detection and Solar Flare Prediction Using SDO Data

    NASA Astrophysics Data System (ADS)

    Qahwaji, Rami; Ahmed, Omar; Colak, Tufan

    The importance of real-time processing of solar data especially for space weather applica-tions is increasing continuously, especially with the launch of SDO which will provide sev-eral times more data compared to previous solar satellites. In this paper, we will show the initial results of applying our Automated Solar Activity Prediction (ASAP) system for the short-term prediction of significant solar flares to SDO data. This automated system is cur-rently working in real-time mode with SOHO/MDI images and its results are available online (http://spaceweather.inf.brad.ac.uk/) whenever a new solar image available. This system inte-grates image processing and machine learning to deliver these predictions. A machine learning-based system is designed to analyse years of sunspots and flares data to extract knowledge and to create associations that can be represented using computer-based learning rules. An imaging-based real time system that provides automated detection, grouping and then clas-sification of recent sunspots based on the McIntosh classification and integrated within this system. The results of current feature detections and flare predictions of ASAP using SOHO data will be compared to those results of ASAP using SDO data and will also be presented in this paper.

  2. 15Data Corruption by High-Energy Particles Solar flares can severely affect sensitive instruments in

    E-print Network

    15Data Corruption by High-Energy Particles Solar flares can severely affect sensitive instruments in space and corrupt the data that they produce. On July 14, 2000 the sun produced a powerful X-class flare

  3. The Effects of Solar Flares on the Ionospheres of Earth and Mars

    E-print Network

    Withers, Paul

    The Effects of Solar Flares on the Ionospheres of Earth and Mars Paul Withers Boston University.10.31 (withers@bu.edu) #12;Solar Flares http://www.assabfn.co.za/pictures/solar_boydenflare_historical_articles photons, and lots of them, but they don't create any ions · Variable (eg 27 day solar rotation) flux

  4. Extreme Ultra-Violet Spectroscopy of the Flaring Solar Chromosphere

    E-print Network

    Milligan, Ryan O

    2015-01-01

    The extreme ultraviolet portion of the solar spectrum contains a wealth of diagnostic tools for probing the lower solar atmosphere in response to an injection of energy, particularly during the impulsive phase of solar flares. These include temperature and density sensitive line ratios, Doppler shifted emission lines and nonthermal broadening, abundance measurements, differential emission measure profiles, and continuum temperatures and energetics, among others. In this paper I shall review some of the advances made in recent years using these techniques, focusing primarily on studies that have utilized data from Hinode/EIS and SDO/EVE, while also providing some historical background and a summary of future spectroscopic instrumentation.

  5. Solar flares and focused energy transport by MHD waves

    NASA Astrophysics Data System (ADS)

    Russell, A. J. B.; Stackhouse, D. J.

    2013-10-01

    Context. Transport of flare energy from the corona to the chromosphere has traditionally been assigned to electron beams; however, interest has recently been renewed in magnetohydrodynamic (MHD) waves as a complementary or alternative mechanism. Aims: We determine whether, and under what conditions, MHD waves deliver spatially localised energy to the chromosphere, as required if MHD waves are to contribute to emission from flare ribbons and kernels. This paper also highlights several properties of MHD waves that are relevant to solar flares and demonstrates their application to the flare problem. Methods: Transport is investigated using a magnetic arcade model and 2.5D MHD simulations. Different wave polarisations are considered and the effect of fine structuring transverse to the magnetic field is also examined. Ray tracing provides additional insight into the evolution of waveguided fast waves. Results: Alfvén waves are very effective at delivering energy fluxes to small areas of chromosphere, localisation being enhanced by magnetic field convergence and phase mixing. Fast waves, in the absence of fine coronal structure, are more suited to powering emission from diffuse rather than compact sources; however, fast waves can be strongly localised by coronal waveguides, in which case focused energy is best transported to the chromosphere when waveguides are directly excited by the energy release. Conclusions: MHD waves pass an important test for inclusion in future flare models.

  6. Temporal Variability of Ion Acceleration and Abundances in Solar Flares

    NASA Technical Reports Server (NTRS)

    Shih, Albert

    2011-01-01

    Solar flares accelerate both ions and electrons to high energies, and their X-ray and gamma-ray signatures not only probe the relationship between their respective acceleration, but also allow for the measurement of accelerated and ambient abundances. RHESSI observations have shown a striking close linear correlation of gamma-ray line fluence from accelerated ions greater than approximately 20 MeV and bremsstrahlung emission from relativistic accelerated electrons greater than 300 keV, when integrated over complete flares, suggesting a common acceleration mechanism. SMM/GRS observations, however, show a weaker correlation, and this discrepancy might be associated with previously observed electron-rich episodes within flares and/or temporal variability of gamma-ray line fluxes over the course of flares. We use the latest RHESSI gamma-ray analysis techniques to study the temporal behavior of the RHESSI flares, and determine what changes can be attributed to an evolving acceleration mechanism or to evolving abundances. We also discuss possible explanations for changing abundances.

  7. Temporal Variability of Ion Acceleration and Abundances in Solar Flares

    NASA Technical Reports Server (NTRS)

    Shih, Albert Y.

    2012-01-01

    solar flares accelerate both ions and electrons to high energies, and their x-ray and gamma-ray signatures not only probe the relationship between their respective acceleration, but also allow for the measurement of accelerated and ambient abundances. RHESSI observations have shown a striking close linear correlation of gamma-ray line fluence from accelerated ions > approx 20 MeV and bremsstrahlung emission from relativistic accelerated electrons >300 kev, when integrated over complete flares, suggesting a common acceleration mechanism. SMM/GRS observations, however, show a weaker correlation, and this discrepancy might be associated with previously observed electron-rich episodes within flares and/or temporal variability of gamma-ray line fluxes over the course of flares. We use the latest RHESSI gamma-ray analysis techniques to study the temporal behavior of the RHESSI flares, and determine what changes can be attributed to an evolving acceleration mechanism or to evolving abundances. We also discuss possible explanations for changing abundances.

  8. Particle acceleration and gamma-emission from solar flares

    NASA Astrophysics Data System (ADS)

    Miroshnichenko, Leonty; Gan, W. Q.; Troitskaia, E. V.

    Experiments on SMM, Yohkoh, GRANAT, Compton GRO, INTEGRAL, RHESSI and CORONAS-F satellites over the past three decades have provided copious data for fundamental research relating to particle acceleration, transport and energetics in flares and to the ambient abun-dance of the corona, chromosphere and photosphere. We summarize main results of solar gamma-astronomy and try to appraise critically a real contribution of those results into modern understanding of solar flares, particle acceleration at the Sun and some properties of the solar atmosphere. Recent findings based on the RHESSI, INTEGRAL and CORONAS-F measure-ments (source locations, spectrum peculiarities, 3He abundance etc.) are especially discussed. Some unusual features of extreme solar events have been found in gamma-ray production and generation of relativistic particles (solar cosmic rays). A number of different plausible assump-tions are considered concerning the details of underlying physical processes during large flares: existence of a steeper distribution of surrounding medium density, enhanced content of the 3He isotope, formation of magnetic trap with specific properties etc. Possible implications of these results are briefly discussed. It is emphasized that real progress in this field may be achieved only by combination of gamma-ray data in different energy ranges with multi-wave and ener-getic particle observations during the same event. We especially note several promising lines for the further studies: 1) resonant acceleration of the 3He ions in the corona; 2) timing of the flare evolution by gamma-ray fluxes in energy range above 90 MeV; 3) separation of gamma-ray fluxes from different sources at/near the Sun (e.g., different acceleration sources/episodes during the same flare, contribution of energetic particles accelerated by the CME-driven shocks etc.); 4) modeling of self-consistent time scenario of the event. Keywords: Sun: atmosphere density, solar flares; Particle acceleration: source location, energy spectrum; Gamma rays: annihilation and de-excitation lines, neutron capture line, pion decay emission

  9. THE THERMAL PROPERTIES OF SOLAR FLARES OVER THREE SOLAR CYCLES USING GOES X-RAY OBSERVATIONS

    SciTech Connect

    Ryan, Daniel F.; Gallagher, Peter T. [School of Physics, Trinity College Dublin, Dublin 2 (Ireland); Milligan, Ryan O.; Dennis, Brian R.; Kim Tolbert, A.; Schwartz, Richard A.; Alex Young, C. [Solar Physics Laboratory (Code 671), Heliophysics Science Division, NASA Goddard Space Flight Center, Greenbelt, MD 20771 (United States)

    2012-10-15

    Solar flare X-ray emission results from rapidly increasing temperatures and emission measures in flaring active region loops. To date, observations from the X-Ray Sensor (XRS) on board the Geostationary Operational Environmental Satellite (GOES) have been used to derive these properties, but have been limited by a number of factors, including the lack of a consistent background subtraction method capable of being automatically applied to large numbers of flares. In this paper, we describe an automated Temperature and Emission measure-Based Background Subtraction method (TEBBS), that builds on the methods of Bornmann. Our algorithm ensures that the derived temperature is always greater than the instrumental limit and the pre-flare background temperature, and that the temperature and emission measure are increasing during the flare rise phase. Additionally, TEBBS utilizes the improved estimates of GOES temperatures and emission measures from White et al. TEBBS was successfully applied to over 50,000 solar flares occurring over nearly three solar cycles (1980-2007), and used to create an extensive catalog of the solar flare thermal properties. We confirm that the peak emission measure and total radiative losses scale with background subtracted GOES X-ray flux as power laws, while the peak temperature scales logarithmically. As expected, the peak emission measure shows an increasing trend with peak temperature, although the total radiative losses do not. While these results are comparable to previous studies, we find that flares of a given GOES class have lower peak temperatures and higher peak emission measures than previously reported. The TEBBS database of flare thermal plasma properties is publicly available at http://www.SolarMonitor.org/TEBBS/.

  10. The Thermal Properties of Solar Flares over Three Solar Cycles Using GOES X-Ray Observations

    NASA Astrophysics Data System (ADS)

    Ryan, Daniel F.; Milligan, Ryan O.; Gallagher, Peter T.; Dennis, Brian R.; Tolbert, A. Kim; Schwartz, Richard A.; Young, C. Alex

    2012-10-01

    Solar flare X-ray emission results from rapidly increasing temperatures and emission measures in flaring active region loops. To date, observations from the X-Ray Sensor (XRS) on board the Geostationary Operational Environmental Satellite (GOES) have been used to derive these properties, but have been limited by a number of factors, including the lack of a consistent background subtraction method capable of being automatically applied to large numbers of flares. In this paper, we describe an automated Temperature and Emission measure-Based Background Subtraction method (TEBBS), that builds on the methods of Bornmann. Our algorithm ensures that the derived temperature is always greater than the instrumental limit and the pre-flare background temperature, and that the temperature and emission measure are increasing during the flare rise phase. Additionally, TEBBS utilizes the improved estimates of GOES temperatures and emission measures from White et al. TEBBS was successfully applied to over 50,000 solar flares occurring over nearly three solar cycles (1980-2007), and used to create an extensive catalog of the solar flare thermal properties. We confirm that the peak emission measure and total radiative losses scale with background subtracted GOES X-ray flux as power laws, while the peak temperature scales logarithmically. As expected, the peak emission measure shows an increasing trend with peak temperature, although the total radiative losses do not. While these results are comparable to previous studies, we find that flares of a given GOES class have lower peak temperatures and higher peak emission measures than previously reported. The TEBBS database of flare thermal plasma properties is publicly available at http://www.SolarMonitor.org/TEBBS/.

  11. SHORT-TERM SOLAR FLARE PREDICTION USING MULTIRESOLUTION PREDICTORS

    SciTech Connect

    Yu Daren; Huang Xin; Hu Qinghua; Zhou Rui [Harbin Institute of Technology, No. 92 West Da-Zhi Street, Harbin, Heilongjiang Province (China); Wang Huaning [National Astronomical Observatories, 20A Datun Road, Chaoyang District, Beijing (China); Cui Yanmei, E-mail: huangxinhit@yahoo.com.c [Center for Space Science and Applied Research, No. 1 Nanertiao, Zhongguancun, Haidian District, Beijing (China)

    2010-01-20

    Multiresolution predictors of solar flares are constructed by a wavelet transform and sequential feature extraction method. Three predictors-the maximum horizontal gradient, the length of neutral line, and the number of singular points-are extracted from Solar and Heliospheric Observatory/Michelson Doppler Imager longitudinal magnetograms. A maximal overlap discrete wavelet transform is used to decompose the sequence of predictors into four frequency bands. In each band, four sequential features-the maximum, the mean, the standard deviation, and the root mean square-are extracted. The multiresolution predictors in the low-frequency band reflect trends in the evolution of newly emerging fluxes. The multiresolution predictors in the high-frequency band reflect the changing rates in emerging flux regions. The variation of emerging fluxes is decoupled by wavelet transform in different frequency bands. The information amount of these multiresolution predictors is evaluated by the information gain ratio. It is found that the multiresolution predictors in the lowest and highest frequency bands contain the most information. Based on these predictors, a C4.5 decision tree algorithm is used to build the short-term solar flare prediction model. It is found that the performance of the short-term solar flare prediction model based on the multiresolution predictors is greatly improved.

  12. 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

  13. DOES A SCALING LAW EXIST BETWEEN SOLAR ENERGETIC PARTICLE EVENTS AND SOLAR FLARES?

    SciTech Connect

    Kahler, S. W., E-mail: AFRL.RVB.PA@kirtland.af.mil [Air Force Research Laboratory, Space Vehicles Directorate, 3550 Aberdeen Ave., Kirtland AFB, NM 87117 (United States)

    2013-05-20

    Among many other natural processes, the size distributions of solar X-ray flares and solar energetic particle (SEP) events are scale-invariant power laws. The measured distributions of SEP events prove to be distinctly flatter, i.e., have smaller power-law slopes, than those of the flares. This has led to speculation that the two distributions are related through a scaling law, first suggested by Hudson, which implies a direct nonlinear physical connection between the processes producing the flares and those producing the SEP events. We present four arguments against this interpretation. First, a true scaling must relate SEP events to all flare X-ray events, and not to a small subset of the X-ray event population. We also show that the assumed scaling law is not mathematically valid and that although the flare X-ray and SEP event data are correlated, they are highly scattered and not necessarily related through an assumed scaling of the two phenomena. An interpretation of SEP events within the context of a recent model of fractal-diffusive self-organized criticality by Aschwanden provides a physical basis for why the SEP distributions should be flatter than those of solar flares. These arguments provide evidence against a close physical connection of flares with SEP production.

  14. THE ACCELERATION OF IONS IN SOLAR FLARES DURING MAGNETIC RECONNECTION

    SciTech Connect

    Knizhnik, K. [Department of Physics and Astronomy, Johns Hopkins University, Baltimore, MD 21218 (United States); Swisdak, M.; Drake, J. F., E-mail: kknizhni@pha.jhu.edu, E-mail: swisdak@umd.edu, E-mail: drake@umd.edu [Institute for Research in Electronics and Applied Physics, University of Maryland, College Park, MD 20742 (United States)

    2011-12-20

    The acceleration of solar flare ions during magnetic reconnection is explored via particle-in-cell simulations that self-consistently and simultaneously follow the motions of both protons and {alpha} particles. We show that the dominant heating of thermal ions during guide field reconnection, the usual type in the solar corona, results from pickup behavior during the entry into reconnection exhausts. In contrast to anti-parallel reconnection, the temperature increment is dominantly transverse, rather than parallel, to the local magnetic field. A comparison of protons and {alpha} reveals a mass-to-charge (M/Q) threshold in pickup behavior that favors the heating of high-M/Q ions, which is consistent with impulsive flare observations.

  15. Particle Acceleration by Fast Modes in Solar Flares

    E-print Network

    Huirong Yan; A. Lazarian; V. Petrosian

    2008-05-08

    We address the problem of particle acceleration in solar flares by fast modes which may be excited during the reconnection and undergo cascade and are subjected to damping. We extend the calculations beyond quasilinear approximation and compare the acceleration and scattering by transit time damping and gyroresonance interactions. We find that the acceleration is dominated by the so called transit time damping mechanism. We estimate the total energy transferred into particles, and show that our approach provides sufficiently accurate results We compare this rate with energy loss rate. Scattering by fast modes appears to be sufficient to prevent the protons from escaping the system during the acceleration. Confinement of electrons, on the other hand, requires the existence of plasma waves. Electrons can be accelerated to GeV energies through the process described here for solar flare conditions.

  16. Internal and External Reconnection Series Homologous Solar Flares

    NASA Technical Reports Server (NTRS)

    Sterling, Alphonse C.; Moore, Ronald L.

    2001-01-01

    Using data from the extreme ultraviolet imaging telescope (EIT) on SOHO and the soft X-ray telescope (SXT) on Yohkoh, we examine a series of morphologically homologous solar flares occurring in National Oceanic and Atmospheric Administration (NOAA) active region 8210 over May 1-2, 1998. An emerging flux region (EFR) impacted against a sunspot to the west and next to a coronal hole to the east is the source of the repeated flaring. An SXT sigmoid parallels the EFR's neutral line at the site of the initial flaring in soft X rays. In EIT each flaring episode begins with the formation of a crinkle pattern external to the EFR. These EIT crinkles move out from, and then in toward, the EFR with velocities approx. 20 km/ s. A shrinking and expansion of the width of the coronal hole coincides with the crinkle activity, and generation and evolution of a postflare loop system begins near the time of crinkle formation. Using a schematic based on magnetograms of the region, we suggest that these observations are consistent with the standard reconnection-based model for solar eruptions but are modified by the presence of the additional magnetic fields of the sunspot and coronal hole. In the schematic, internal reconnection begins inside of the EFR-associated fields, unleashing a flare, postflare loops, and a coronal mass ejection (CME). External reconnection, first occurring between the escaping CME and the coronal hole field and second occurring between fields formed as a result of the first external reconnection, results in the EIT crinkles and changes in the coronal hole boundary. By the end of the second external reconnection, the initial setup is reinstated; thus the sequence can repeat, resulting in morphologically homologous eruptions. Our inferred magnetic topology is similar to that suggested in the "breakout model" of eruptions although we cannot determine if our eruptions are released primarily by the breakout mechanism (external reconnection) or, alternatively, primarily by the internal reconnection.

  17. Solar Flare Observations at Submm-waves

    NASA Astrophysics Data System (ADS)

    Kaufmann, P.; Raulin, J.-P.; Correia, E.; Costa, J. E. R.; Guillermo, C.; de Castro, Giménez; Silva, A. V. R.; Levato, H.; Rovira, M.; Mandrini, C.; Fernández-Borda, R.; Bauer, O.

    We report on the recent installation of the new Solar Submillimeter Telescope(SST) at the El Leoncito site, located in the Argentinean Andes, and also show first observational results. The instrument consists of a radome-enclosed 1.5-m cassegrain reflector and a system of two radiometers at 405 GHz and four at 212 GHz. The SST observes the quiet Sun and solar bursts simultaneously at both submillimeter-wave frequencies with a sampling rate of 1 millisecond. Since SST has seen the "first light" in May 1999, nearly 45 hours of continuous tracking of solar active regions were collected during short campaigns which produced first evidence for solar activity. The project has been funded by the Brazilian agency FAPESP, receiving support from the Argentinean agency CONICET through their institutes CASLEO and IAFE and from IAP, University of Bern and the Swiss National Science Foundation.

  18. The North-South Asymmetry of Soft X-Ray Solar Flares

    Microsoft Academic Search

    Georgeta Maris; Miruna Daniela Popescu; Marilena Mierla

    2002-01-01

    We analyse the North-South (N-S) asymmetry of soft X-ray (SXR) solar flares during the 11-year solar cycle (SC). After reviewing the literature on flare dominance in the northern and southern hemispheres of the solar disk for SCs 17-23, we analyse the SXR flare distribution in the two hemispheres during the period 1976-2001. The analysis was made using the number of

  19. THE NORTH-SOUTH ASYMMETRY OF SOFT X-RAY SOLAR FLARES

    Microsoft Academic Search

    MIRUNA DANIELA POPESCU; MARILENA MIERLA; N. Ireland

    2002-01-01

    We analyse the North-South (N-S) asymmetry of soft X-ray (SXR) solar flares during the 11-year solar cycle (SC). After reviewing the literature on flare dominance in the northern and southern hemispheres of the solar disk for SCs 17-23, we analyse the SXR flare distribution in the two hemispheres during the period 1976- 2001. The analysis was made using the number

  20. Microwave Fine Structures in the Initial Phase of Solar Flares and CMEs

    Microsoft Academic Search

    C. M. Tan; Y. H. Yan; Q. J. Fu; Y. Y. Liu; H. R. Ji; Z. J. Chen

    2005-01-01

    Solar radio fine structures (FSs) may be as an important diagnostics stool to draw the evolution map of the flare loop in the initial phase of solar flares. Also, it may be an important signature of the initial phase of CMEs. Here we analyzed a series of solar radio bursts with drift pulsation structures (DPS) and FSs during the former

  1. The impulsive hard X-rays from solar flares

    NASA Technical Reports Server (NTRS)

    Leach, J.

    1984-01-01

    A technique for determining the physical arrangement of a solar flare during the impulsive phase was developed based upon a nonthermal model interpretation of the emitted hard X-rays. Accurate values are obtained for the flare parameters, including those which describe the magnetic field structure and the beaming of the energetic electrons, parameters which have hitherto been mostly inaccessible. The X-ray intensity height structure can be described readily with a single expression based upon a semi-empirical fit to the results from many models. Results show that the degree of linear polarization of the X-rays from a flaring loop does not exceed 25 percent and can easily and naturally be as low as the polarization expected from a thermal model. This is a highly significant result in that it supersedes those based upon less thorough calculations of the electron beam dynamics and requires that a reevaluation of hopes of using polarization measurements to discriminate between categories of flare models.

  2. Solar flare impulsive phase emission observed with SDO/EVE

    SciTech Connect

    Kennedy, Michael B.; Milligan, Ryan O.; Mathioudakis, Mihalis; Keenan, Francis P., E-mail: mkennedy29@qub.ac.uk [Astrophysics Research Centre, School of Mathematics and Physics, Queen's University Belfast, University Road, Belfast BT7 1NN (United Kingdom)

    2013-12-10

    Differential emission measures (DEMs) during the impulsive phase of solar flares were constructed using observations from the EUV Variability Experiment (EVE) and the Markov-Chain Monte Carlo method. Emission lines from ions formed over the temperature range log T{sub e} = 5.8-7.2 allow the evolution of the DEM to be studied over a wide temperature range at 10 s cadence. The technique was applied to several M- and X-class flares, where impulsive phase EUV emission is observable in the disk-integrated EVE spectra from emission lines formed up to 3-4 MK and we use spatially unresolved EVE observations to infer the thermal structure of the emitting region. For the nine events studied, the DEMs exhibited a two-component distribution during the impulsive phase, a low-temperature component with peak temperature of 1-2 MK, and a broad high-temperature component from 7 to 30 MK. A bimodal high-temperature component is also found for several events, with peaks at 8 and 25 MK during the impulsive phase. The origin of the emission was verified using Atmospheric Imaging Assembly images to be the flare ribbons and footpoints, indicating that the constructed DEMs represent the spatially average thermal structure of the chromospheric flare emission during the impulsive phase.

  3. Solar flares and solar wind helium enrichments: July 1965–July 1967

    Microsoft Academic Search

    J. Hirshberg; S. J. Bame; D. E. Robbins

    1972-01-01

    It has previously been suggested that the very high relative abundances of helium occasionally observed in the solar wind mark the plasma accelerated by major solar flares. To confirm this hypothesis, we have studied the 43 spectra with He\\/H ? 15% that were observed among 10300 spectra collected by Vela 3 between July 1965–July 1967. The 43 spectra were distributed

  4. Anatomy of a Solar Flare: Measurements of the 2006 December 14 X-class Flare with GONG, Hinode, and RHESSI

    NASA Astrophysics Data System (ADS)

    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.

  5. Study on the triggering process of solar flares based on Hinode/SOT observations

    SciTech Connect

    Bamba, Y.; Kusano, K.; Yamamoto, T. T. [Solar-Terrestrial Environment Laboratory, Nagoya University, Furo-cho, Chikusa-ku, Nagoya, Aichi 464-8601 (Japan); Okamoto, T. J., E-mail: y-bamba@stelab.nagoya-u.ac.jp [ISAS/JAXA, Sagamihara, Kanagawa 252-5210 (Japan)

    2013-11-20

    We investigated four major solar flare events that occurred in active regions NOAA 10930 (2006 December 13 and 14) and NOAA 11158 (2011 February 13 and 15) by using data observed by the Solar Optical Telescope on board the Hinode satellite. To reveal the trigger mechanism of solar flares, we analyzed the spatio-temporal correlation between the detailed magnetic field structure and the emission image of the Ca II H line at the central part of flaring regions for several hours prior to the onset of the flares. In all the flare events, we observed that the magnetic shear angle in the flaring regions exceeded 70°, as well as that characteristic magnetic disturbances developed at the centers of flaring regions in the pre-flare phase. These magnetic disturbances can be classified into two groups depending on the structure of their magnetic polarity inversion lines; the so-called opposite-polarity and reversed-shear magnetic field recently proposed by our group, although the magnetic disturbance in one event of the four samples is too subtle to clearly recognize the detailed structure. The result suggests that some major solar flares are triggered by rather small magnetic disturbances. We also show that the critical size of the flare-trigger field varies among flare events and briefly discuss how the flare-trigger process depends on the evolution of active regions.

  6. Simultaneous 2 and 6 centimeter wavelength observations of a solar flare using the VLA

    Microsoft Academic Search

    M. R. Kundu; T. Velusamy; S. M. White

    1987-01-01

    VLA observations of a solar active region and a flare are discussed. The event was observed at wavelengths of 2 and 6 cm simultaneously. Radio maps prior to the flare delineate the most important magnetic structures in the region. Interaction between these structures apparently led to preheating of plasma above the active region some 30 minutes prior to the flare.

  7. Energetic particles in solar flares. Chapter 4 in the proceedings of the 2nd Skylab Workshop on Solar Flares

    NASA Technical Reports Server (NTRS)

    Ramaty, R.; Colgate, S. A.; Dulk, G. A.; Hoyng, P.; Knight, J. W., III; Lin, R. P.; Melrose, D. B.; Paizis, C.; Orrall, F.; Shapiro, P. R.

    1978-01-01

    The recent direct observational evidence for the acceleration of particles in solar flares, i.e. radio emission, bremsstrahlung X-ray emission, gamma-ray line and continuum emission, as well as direct observations of energetic electrons and ions, are discussed and intercorrelated. At least two distinct phases of acceleration of solar particles exist that can be distinguished in terms of temporal behavior, type and energy of particles accelerated and the acceleration mechanism. Bulk energization seems the likely acceleration mechanism for the first phase while Fermi mechanism is a viable candidate for the second one.

  8. Magnetic and Dynamical Photospheric Disturbances Observed During an M3.2 Solar Flare

    NASA Astrophysics Data System (ADS)

    Kuckein, C.; Collados, M.; Manso Sainz, R.

    2015-02-01

    This Letter reports on a set of full-Stokes spectropolarimetric observations in the near-infrared He i 10830 Å spectral region covering the pre-flare, flare, and post-flare phases of an M3.2 class solar flare. The flare originated on 2013 May 17 and belonged to active region NOAA 11748. We detected strong He i 10830 Å emission in the flare. The red component of the He i triplet peaks at an intensity ratio to the continuum of about 1.86. During the flare, He i Stokes V is substantially larger and appears reversed compared to the usually larger Si i Stokes V profile. The photospheric Si i inversions of the four Stokes profiles reveal the following: (1) the magnetic field strength in the photosphere decreases or is even absent during the flare phase, as compared to the pre-flare phase. However, this decrease is not permanent. After the flare, the magnetic field recovers its pre-flare configuration in a short time (i.e., 30 minutes after the flare). (2) In the photosphere, the line of sight velocities show a regular granular up- and downflow pattern before the flare erupts. During the flare, upflows (blueshifts) dominate the area where the flare is produced. Evaporation rates of ˜ {{10}-3} and ˜ {{10}-4} g cm-2 s-1 have been derived in the deep and high photosphere, respectively, capable of increasing the chromospheric density by a factor of two in about 400 s.

  9. Singly charged energetic helium emitted in solar flares

    NASA Technical Reports Server (NTRS)

    Hovestadt, D.; Hoefner, H.; Klecker, B.; Scholer, M.; Gloeckler, G.; Ipavich, F. M.; Fan, C. Y.; Fisk, L. A.; Ogallagher, J. J.

    1981-01-01

    First direct charge state measurements of 0.41-1.05 MeV per nucleon helium accelerated at the sun reveal surprisingly large abundances of singly ionized helium, with typical He(+)/He(++) ratios between 0.04 and 0.21. This unexpected overabundance of He(+) was observed in each of the three large solar-flare particle events which occurred between 1978 August and 1979 October. The data were obtained with the Max-Planck-Institut/University of Maryland Experiment on board the ISEE-3 spacecraft. The observations suggest either strong coronal temperature inhomogeneities including cool regions of approximately 100,000 K or injection of 'cold' chromospheric/photospheric material into the flare acceleration region.

  10. Continuum analysis of an avalanche model for solar flares.

    PubMed

    Liu, Han-Li; Charbonneau, Paul; Pouquet, Annick; Bogdan, Thomas; McIntosh, Scott

    2002-11-01

    We investigate the continuum limit of a class of self-organized critical lattice models for solar flares. Such models differ from the classical numerical sandpile model in their formulation of stability criteria in terms of the curvature of the nodal field, and are known to belong to a different universality class. A fourth-order nonlinear hyperdiffusion equation is reverse engineered from the discrete model's redistribution rule. A dynamical renormalization-group analysis of the equation yields scaling exponents that compare favorably with those measured in the discrete lattice model within the relevant spectral range dictated by the sizes of the domain and the lattice grid. We argue that the fourth-order nonlinear diffusion equation that models the behavior of the discrete model in the continuum limit is, in fact, compatible with magnetohydrodynamics (MHD) of the flaring phenomenon in the regime of strong magnetic field and the effective magnetic diffusivity characteristic of strong MHD turbulence. PMID:12513560

  11. A mechanism for deep chromospheric heating during solar flares

    NASA Technical Reports Server (NTRS)

    Machado, M. E.; Emslie, A. G.; Mauas, P. J.

    1986-01-01

    The role of the negative hydrogen ion, H(-), in the energy balance of the deep solar chromosphere is reexamined and it is found, in contrast with earlier authors, that H(-) is a source of heating at these levels. The response of this region to an ionizing flux of flare-associated UV radiation (1500 to 1900 A) is then addressed: it is found that the excess ionization of Si to Si(+) increases the local electron number density considerably, since most species are largely neutral at deep chromospheric levels. This in turn increases the electron-hydrogen atom association rate, the H(-) abundance, and the rate of absorption of photospheric radiation by this ion. It is found that the excess absorption by this process may lead to a substantial temperature enhancement at temperature minimum levels during flares.

  12. 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-increasing motion continues. The authors propose that a series of these flaring processes constitutes a set of homologous flares. The time interval between successive flaring events depends on the energy input rate into the system, which is governed by the nature of the footpoint motion and the flux reconnecting rate. They have also investigated the destruction of a magnetic island in a system undergoing a decrease of magnetic shear. The result suggests that there is a critical value of magnetic shear for existence of a magnetic island in an arcade-like field configuration.

  13. Relaxation of magnetic field relative to plasma density during solar flares

    NASA Astrophysics Data System (ADS)

    Yu, Sijie; Yan, Yihua; Tan, Baolin

    2013-07-01

    We investigated the variations of 74 microwave ZP structures observed by Chinese Solar Broadband Radio Spectrometer at 2.6-3.8 GHz in 9 solar flares, found that the ratio between the plasma density scale height LN and the magnetic field scale height LB in emission source displays a tendency of decrease during the flaring process, indicates that LB increases faster than the LN during solar flares. The detailed analysis of the step-wise decrease of LN/LB in three typical X-class flares reveals the magnetic field relaxation relative to the plasma density.

  14. The isotopic composition of solar flare accelerated magnesium

    NASA Technical Reports Server (NTRS)

    Mewaldt, R. A.; Spalding, J. D.; Stone, E. C.; Vogt, R. E.

    1981-01-01

    Measurements of the abundances of three isotopes of magnesium in solar energetic particles are reported. Data were obtained from the Heavy Isotope Spectrometer Telescope on board the ISEE 3 spacecraft during a large solar particle event following the 2B solar flare of September 23, 1978. A two-dimensional maximum likelihood analysis of the mass determinations for each event, which were taken with a resolution of 0.23 amu, indicates a Mg-25/Mg-24 ratio of 0.14 (+0.05, -0.02) and a Mg-26/Mg-24 ratio of 0.15 (+0.04, -0.03) in the energy interval 12-36 MeV/n. The results are consistent with terrestrial magnesium isotope abundances.

  15. An upper limit on the hardness of the nonthermal electron spectra produced during the flash phase of solar flares.

    NASA Technical Reports Server (NTRS)

    Kane, S. R.

    1971-01-01

    The observations of impulsive solar-flare X-rays above 10 keV made with OGO-5 satellite have been analyzed in order to study the variation of the nonthermal electron spectrum from one flare to another. The X-ray spectrum at the maxima of 129 impulsive X-ray bursts is represented by KE to the minus-gamma power photons per sq cm per sec per keV, and the frequency of occurrence of bursts with different values of gamma is studied. It is found that for gamma less than 4.0 the frequency of bursts rapidly decreases with the decrease in the value of gamma. The probability of occurrence of a burst with gamma less than 2.3 is extremely small.

  16. Seismic Emission from A M9.5Class Solar Flare

    Microsoft Academic Search

    A.-C. Donea; D. Besliu-Ionescu; P. S. Cally; C. Lindsey; V. V. Zharkova

    2006-01-01

    Following the discovery of a few significant seismic sources at 6.0 mHz from the large solar flares of October 28 and 29,\\u000a 2003, we have extended SOHO\\/MDI helioseismic observations to moderate M-class flares. We report the detection of seismic waves\\u000a emitted from the ? ? ? active region NOAA 9608 on September 9, 2001. A quite impulsive solar flare of

  17. Measuring and Modeling Solar Flares with SDO EVE

    NASA Technical Reports Server (NTRS)

    Chamberlin, Phillip C.; Woods, Thomas N.; Wilson, Anne; Lindholm, Chris

    2010-01-01

    The Flare Irradiance Spectral Model (FISM) currently provides estimations of the solar Vacuum Ultra-Violet (VUV; 0.1-190 nm) irradiance from 1947 to present at 1 nm bins and 60 second temporal resolution. The accuracy of FISM is limited to 1nm because the TIMED SEE Level 3 and Level 3A measurement, for which the FISM relationships were based on, were at Inm. With the launch of the Solar Dynamics Observatory (SDO) in Feb 2010, the EUV Variability Experiment (EVE) will provide more accurate, increased spectral resolution (0.1 nm) measurements from 6 nm to 106 nm every 10-seconds and almost 100% duty cycle. EVE also observes additional broadband measurements for 0.1-7 nm, some EUV bands from 16 nm to 40 nm, and Hydrogen Lyman alpha at 121.6 nm. Along with the better spectral resolution of EVE leading to similar spectral resolution improvements in FISM, other significant improvements provide by SDO/EVE measurements will be multi-thermal gradual phase decay, impulsive phase center-to-limb variation characterization, non-flare sub-daily variations, and multi-thermal proxies. SDO/EVE observations of various solar flares with different characteristics will be presented, with the discussion theme focused on how EVE observations will help improve the accuracy of the FISM in the future. The final topic will present the updated FISM website that now has easier access to the FISM results and produce real-time updates that are useful for Space Weather studies.

  18. Stochastic three-wave interaction in flaring solar loops

    NASA Technical Reports Server (NTRS)

    Vlahos, L.; Sharma, R. R.; Papadopoulos, K.

    1983-01-01

    A model is proposed for the dynamic structure of high-frequency microwave bursts. The dynamic component is attributed to beams of precipitating electrons which generate electrostatic waves in the upper hybrid branch. Coherent upconversion of the electrostatic waves to electromagnetic waves produces an intrinsically stochastic emission component which is superposed on the gyrosynchrotron continuum generated by stably trapped electron fluxes. The role of the density and temperature of the ambient plasma in the wave growth and the transition of the three wave upconversion to stochastic, despite the stationarity of the energy source, are discussed in detail. The model appears to reproduce the observational features for reasonable parameters of the solar flare plasma.

  19. Magnetohydrodynamic turbulence dissipation and stochastic proton acceleration in solar flares

    NASA Technical Reports Server (NTRS)

    Miller, James A.

    1991-01-01

    The Alfven and fast magnetosonic wave MHD modes can stochastically accelerate protons from super-Alfvenic to ultrarelativistic energies in solar flares. It is the Landau resonance, however, which generates most of the magnetosonic wave energy being dissipated on electron heating rather than on stochastic proton acceleration. Alfven waves are also subject to a nonlinear wave-particle interaction, and nonlinear Landau damping can selectively and efficiently heat the ambient protons to preaccelerate many to super-Alfvenic speeds. A spectrum of Alfven waves can therefore energize protons from low-temperature thermal to ultrarelativistic energies through a combination of linear and nonlinear particle-wave interactions.

  20. Impulsive phase solar flare X-ray polarimetry

    NASA Technical Reports Server (NTRS)

    Chanan, Gary; Emslie, A. Gordon; Novick, Robert

    1986-01-01

    The pioneering observational work in solar flare X-ray polarimetry was done in a series of satellite experiments by Tindo and his collaborators in the Soviet Union; initial results showed high levels of polarization in X-ray flares (up to 40%), although of rather low statistical significance, and these were generally interpreted as evidence for strong beaming of suprathermal electrons in the flare energy release process. However, the results of the polarimeter flown by the Columbia Astrophysics Laboratory as part of the STS-3 payload on the Space Shuttle by contrast showed very low levels of polarization. The largest value (observed during the impulsive phase of a single event) was 3.4% + or - 2.2%. At the same time but independent of the observational work, Leach and Petrosian (1983) showed that the high levels of polarization in the Tindo results were difficult to understand theoretically, since the electron beam is isotropized on an energy loss timescale. A subsequent comparison by Leach, Emslie, and Petrosian (1985) of the impulsive phase STS-3 result and the above theoretical treatment shows that the former is consistent with several current models and that a factor of approximately 3 improvement in sensitivity is needed to distinguish properly among the possibilities.

  1. Extremely Large EUV Late Phase of Solar Flares

    E-print Network

    Liu, Kai; Zhang, Jie; Cheng, Xin; Liu, Rui; Shen, Chenglong

    2015-01-01

    The second peak in the Fe XVI 33.5 nm line irradiance observed during solar flares by Extreme ultraviolet Variability Experiment (EVE) is known as Extreme UltraViolet (EUV) late phase. Our previous paper (Liu et al. 2013) found that the main emissions in the late phase are originated from large-scale loop arcades that are closely connected to but different from the post flare loops (PFLs), and we also proposed that a long cooling process without additional heating could explain the late phase. In this paper, we define the extremely large late phase because it not only has a bigger peak in the warm 33.5 irradiance profile, but also releases more EUV radiative energy than the main phase. Through detailedly inspecting the EUV images from three point-of-view, it is found that, besides the later phase loop arcades, the more contribution of the extremely large late phase is from a hot structure that fails to erupt. This hot structure is identified as a flux rope, which is quickly energized by the flare reconnection...

  2. Space radiation dose analysis for solar flare of August 1989

    NASA Technical Reports Server (NTRS)

    Nealy, John E.; Simonsen, Lisa C.; Sauer, Herbert H.; Wilson, John W.; Townsend, Lawrence W.

    1990-01-01

    Potential dose and dose rate levels to astronauts in deep space are predicted for the solar flare event which occurred during the week of August 13, 1989. The Geostationary Operational Environmental Satellite (GOES-7) monitored the temporal development and energy characteristics of the protons emitted during this event. From these data, differential fluence as a function of energy was obtained in order to analyze the flare using the Langley baryon transport code, BRYNTRN, which describes the interactions of incident protons in matter. Dose equivalent estimates for the skin, ocular lens, and vital organs for 0.5 to 20 g/sq cm of aluminum shielding were predicted. For relatively light shielding (less than 2 g/sq cm), the skin and ocular lens 30-day exposure limits are exceeded within several hours of flare onset. The vital organ (5 cm depth) dose equivalent is exceeded only for the thinnest shield (0.5 g/sq cm). Dose rates (rem/hr) for the skin, ocular lens, and vital organs are also computed.

  3. Extremely Large EUV Late Phase of Solar Flares

    NASA Astrophysics Data System (ADS)

    Liu, Kai; Wang, Yuming; Zhang, Jie; Cheng, Xin; Liu, Rui; Shen, Chenglong

    2015-04-01

    The second peak in the Fe XVI 33.5 nm line irradiance observed during solar flares by Extreme ultraviolet Variability Experiment (EVE) is known as Extreme UltraViolet (EUV) late phase. Our previous paper found that the main emissions in the late phase are originated from large-scale loop arcades that are closely connected to but different from the post flare loops (PFLs), and we also proposed that a long cooling process without additional heating could explain the late phase. In this paper, we define the extremely large late phase because it not only has a bigger peak in the warm 33.5 irradiance profile, but also releases more EUV radiative energy than the main phase. Through detailedly inspecting the EUV images from three point-of-view, it is found that, besides the later phase loop arcades, the more contribution of the extremely large late phase is from a hot structure that fails to erupt. This hot structure is identified as a flux rope, which is quickly energized by the flare reconnection and later on continuously produces the thermal energy during the gradual phase. Together with the late-phase loop arcades, the fail to erupt flux rope with the additional heating creates the extremely large EUV late phase.

  4. Electron-cyclotron maser emission during solar and stellar flares

    NASA Technical Reports Server (NTRS)

    Winglee, R. M.

    1985-01-01

    Radio bursts, with high brightness temperature 10 to the 10th power K and high degree of polarization, and the heating of the solar and stellar coronae during flares have been attributed to emission from the semirelativistic maser instability. In plasmas where the electron-plasma frequency, p, omega sub p, and the electron-cyclotron frequency, Omega sub e, are such that omega sup 2 sub p/Omega sup 2 sub e 1, x-mode growth dominates while z-mode growth dominates if omega sup 2 sub p/Omega sup 2 sub e is of order unity. The actual value of omega sup 2 sub p/Omega sup 2 sub e at which x-mode growth dominates is shown to be dependent on the plasma temperature with x-mode growth dominating at higher omega sub p/Omega sub e as the plasma temperature increases. Observations from a set of 20 impulsive flares indicate that the derived conditions for the dominance of x-mode growth are satisfied in about 75 percent of the flares.

  5. Electron-cyclotron maser emission during solar and stellar flares

    NASA Technical Reports Server (NTRS)

    Winglee, R. M.

    1985-01-01

    Radio bursts, with high brightness temperature 10 to the 10th power K and high degree of polarization, and the heating of the solar and stellar coronae during flares have been attributed to emission from the semirelativistic maser instability. In plasmas where the electron-plasma frequency, p, omega sub p, and the electron-cyclotron frequency, Omega sub e, are such that omego sup 2 sub p/Omega sup 2 sub e 1, x-mode growth dominates while z-mode growth dominates if omega sup 2 sub p/Omega sup 2 sub e at which x-mode growth dominates is shown to be dependent on the plasma temperature with x-mode growth dominating at higher omega sub p/Omega sub e as the plasma temperature increases. Observations from a set of 20 impulsive flares indicate that the derived conditions for the dominance of x-mode growth are satisfied in about 75 percent of the flares.

  6. The U.S. Max '91 program of flare research at the next solar maximum

    NASA Technical Reports Server (NTRS)

    Dennis, Brian R.

    1988-01-01

    A brief summary is presented of Max '91, a proposed program to study the problems of flare physics during the next solar maximum. The program uses instruments on spacecraft, rockets, balloons, and ground-based observations to study the processes of particle acceleration and energy storage, release, and transport in solar flares. The space missions, instruments, and experiments included in the program are outlined.

  7. MICROWAVE AND HARD XRAY OBSERVATIONS OF FOOTPOINT EMISSION FROM SOLAR FLARES

    E-print Network

    White, Stephen

    radio and X­ray imaging data for two solar flares in order to test the idea that asymmetric on the Yohkoh spacecraft, and by the Nobeyama 17 GHz radioheliograph. The hard X­ray images in one case show twoMICROWAVE AND HARD X­RAY OBSERVATIONS OF FOOTPOINT EMISSION FROM SOLAR FLARES M. R. KUNDU Dept

  8. Space weather effects on the Mars ionosphere due to solar flares and meteors

    E-print Network

    Withers, Paul

    Space weather effects on the Mars ionosphere due to solar flares and meteors P. Withers (1), M) Using data from the Radio Science Experiment onboard the Mars Global Surveyor (MGS) satellite, we have observed two aspects of space weather at Mars. Following solar flares of both moderate to strong magnitude

  9. NEUTRON AND ELECTROMAGNETIC EMISSIONS DURING THE 1990 MAY 24 SOLAR FLARE

    E-print Network

    Usoskin, Ilya G.

    NEUTRON AND ELECTROMAGNETIC EMISSIONS DURING THE 1990 MAY 24 SOLAR FLARE L. G. KOCHAROV,* JEONGWOO revised form 15 July, 1994) Abstract. In this paper, we are primarilyconcerned with the solar neutron emission during the 1990 May 24 flare, utilizing the counting rate of the Climax neutron monitor

  10. Variations of magnetic fields and electric currents associated with a solar flare

    Microsoft Academic Search

    Yuanzhang Lin; Xiaolei Wei; Hongqi Zhang

    1993-01-01

    The high-resolution vector magnetograms obtained with the solar telescope magnetograph of the Beijing Astronomical Observatory of the active region AR 4862 on 7 October, 1987, close before and after a solar flare, were used to calculate the electric current densities in the region. Then the relations between the flare and the magnetic fields as well as the electric currents were

  11. The solar flare of the 14th of July 2000 (L3+C detector results)

    Microsoft Academic Search

    P. Achard; O Adriani; M. Aguilar-Benitez; M. van den Akker; J. Alcaraz; G. Alemanni; James V Allaby; A. Aloisio; M. G. Alviggi; H. Anderhub; V. P. Andreev; F. Anselmo; A. Arefiev; T. Azemoon; T. Aziz; P. Bagnaia; A. Bajo; G. Baksay; L. Baksay; J. Bähr; S. V. Baldew; S. Banerjee; A. Barczyk; R. Barillère; P. Bartalini; M. Basile; N. Batalova; R. Battiston; A. Bay; F. Becattini; U. Becker; F. Behner; L. Bellucci; R. Berbeco; J. Berdugo; P. Berges; B. Bertucci; B. L. Betev; M. Biasini; M. Biglietti; A. Biland; J. J. Blaising; S. C. Blyth; G. J. Bobbink; A. Böhm; L. Boldizsar; B. Borgia; S. Bottai; D. Bourilkov; M. Bourquin; S. Braccini; J. G. Branson; F. Brochu; J. D. Burger; W. J. Burger; X. D. Cai; M. Capell; G. Cara Romeo; G. Carlino; A. Cartacci; J. Casaus; F. Cavallari; N. Cavallo; C. Cecchi; M. Cerrada; M Chamizo-Llatas; T. Chiarusi; Y. H. Chang; M. Chemarin; A. Chen; G. Chen; H. F. Chen; H. S. Chen; G. Chiefari; L. Cifarelli; F. Cindolo; I. Clare; R. Clare; G. Coignet; N. Colino; S. Costantini; B. de la Cruz; S. Cucciarelli; R. de Asmundis; P. Déglon; J. Debreczeni; A. Degré; K. Dehmelt; K. Deiters; D. della Volpe; E. Delmeire; P. Denes; F. DeNotaristefani; A. De Salvo; M. Diemoz; M. Dierckxsens; L. K. Ding; C. Dionisi; M. Dittmar; A. Doria; M. T. Dova; D. Duchesneau; M. Duda; I. Duran; B. Echenard; A. Eline; A. El Hage; H. El Mamouni; A. Engler; F. J. Eppling; P. Extermann; G. Faber; M. A. Falagan; S. Falciano; A. Favara; J. Fay; O. Fedin; M. Felcini; T. Ferguson; H S Fesefeldt; E. Fiandrini; J. H. Field; F. Filthaut; W. Fisher; G. Forconi; K. Freudenreich; C. Furetta; Yu. Galaktionov; S. N. Ganguli; P. Garcia-Abia; M. Gataullin; S. Gentile; S. Giagu; Z. F. Gong; H. J. Grabosch; G. Grenier; O. Grimm; H. Groenstege; M. W. Gruenewald; M. Guida; Y. N. Guo; S. K. Gupta; V. K. Gupta; A. Gurtu; L. J. Gutay; D. Haas; Ch. Haller; D. Hatzifotiadou; Y. Hayashi; Z. X. He; T. Hebbeker; A. Hervé; J. Hirschfelder; H. Hofer; M. Hohlmann; A. Holzner; S. R. Hou; A. X. Huo; N. Ito; B. N. Jin; P. Jindal; C. L. Jing; L. W. Jones; P. de Jong; I. Josa-Mutuberría; V. Kantserov; M. Kaur; S. Kawakami; M. N. Kienzle-Focacci; J. K. Kim; J. Kirkby; W. Kittel; A. Klimentov; A. C. König; E. Kok; A. Korn; M. Kopal; V. Koutsenko; M. Kräber; H. H. Kuang; R. W. Kraemer; A. Krüger; J. Kuijpers; A. Kunin; P. Ladron de Guevara; I. Laktineh; G. Landi; M. Lebeau; A. Lebedev; P Lecomte; P. Lecomte; P. Lecoq; P. Le Coultre; J. M. Le Goff; Y. Lei; H. Leich; R. Leiste; M. Levtchenko; P. Levtchenko; C. Li; L. Li; Z. C. Li; S. Likhoded; C. H. Lin; W. T. Lin; F. L. Linde; L. Lista; Z. A. Liu; W. Lohmann; E. Longo; Y. S. Lu; C. Luci; L. Luminari; W. Lustermann; W. G. Ma; X. H. Ma; Y. Q. Ma; L. Malgeri; A. Malinin; C. Maña; J P Martin; J. P. Martin; F. Marzano; K. Mazumdar; R. R. McNeil; X. W. Meng; L. Merola; M. Meschini; W. J. Metzger; A Van Mil; H. Milcent; G. Mirabelli; J. Mnich; G. B. Mohanty; B. Monteleoni; G. S. Muanza; A. J. M. Muijs; M. Musy; S. Nagy; R. Nahnhauer; V. A. Naumov; S. Natale; M. Napolitano; F. Nessi-Tedaldi; H. Newman; A. Nisati; T. Novak; H. Nowak; R. Ofierzynski; G. Organtini; I. Pal; C. Palomares; P. Paolucci; R. Paramatti; J.-F. Parriaud; G. Passaleva; S. Patricelli; T. Paul; M. Pauluzzi; C. Paus; F. Pauss; M. Pedace; S. Pensotti; D. Perret-Gallix; B. Petersen; D. Piccolo; F. Pierella; M Pioppi; P. A. Piroué; E. Pistolesi; V. Plyaskin; M. Pohl; V. Pojidaev; J. Pothier; D O Prokofiev; C. R. Qing; G. Rahal-Callot; M. A. Rahaman; P. Raics; N. Raja; R. Ramelli; P. G. Rancoita; R. Ranieri; A V Raspereza; K. C. Ravindran; P. Razis; S. Rembeczki; D. Ren; M. Rescigno; S. Reucroft; P A M Rewiersma; S. Riemann; A. Rojkov; L. Romero; A. Rosca; C. Rosemann; C. Rosenbleck; S. Rosier-Lees; S. Roth; J. A. Rubio; G. Ruggiero; H. Rykaczewski; A. Sakharov; S. Saremi; S. Sarkar; J. Salicio; E. Sanchez; C. Schäfer; V Shchegelskii; B. Schoeneich; D. J. Schotanus; C. Sciacca; L. Servoli; C. Q. Shen; S. Shevchenko; N. Shivarov; V. Shoutko; E. Shumilov; A. Shvorob; D. Son; C. Souga; P. Spillantini; M. Steuer; D. P. Stickland; B. Stoyanov; A. Straessner; K. Sudhakar; G G Sultanov; L. Z. Sun; S. Sushkov; H. Suter; J. D. Swain; Z. Szillasi; X. W. Tang; P. Tarjan; L. Tauscher; L. Taylor; B. Tellili; D. Teyssier; C. Timmermans; Samuel C. C. Ting; S. M. Ting; S. C. Tonwar; J. Tóth; G. Trowitzsch; C. Tully; K. L. Tung; J. Ulbricht; M. Unger; E. Valente; H. Verkooijen; R. T. Van de Walle; R. Vasquez; G. Vesztergombi; I Vetlitskii; G. Viertel; M. Vivargent; S. Vlachos; I. Vodopianov; H. Vogel; H. Vogt; I. Vorobiev; A. A. Vorobyov; M. Wadhwa; R. G. Wang; Q. Wang; X. L. Wang; X. W. Wang; Z. M. Wang; M. Weber; R. van Wijk; T. A. M. Wijnen; H. Wilkens; S. Wynhoff; L. Xia; Y. P. Xu; Z. Z. Xu; B. Z. Yang; C. G. Yang; H. J. Yang; M. Yang; X. F. Yang; Z. G. Yao; S. C. Yeh; Z. Q. Yu; An. Zalite; Yu. Zalite; C. Zhang

    2006-01-01

    Aims.Several experiments have reported observations on possible correlations between the flux of high energy muons and intense solar flares. If confirmed, these observations would have significant implications for acceleration processes in the heliosphere able to accelerate protons and other ions to energies of at least tens of GeV. Methods: The solar flare of the 14 of July 2000 offered a

  12. Exploring Magnetism in Solar Flares: A Teachers' Magnetism Activity Guide for Grades 8-12

    NSDL National Science Digital Library

    2011-04-20

    Exploring Magnetism in Solar Flares is part of a series of guides highlighting the importance of magnetism in Earth and space sciences. It contains four activities exploring solar flares while addressing science, math, and literacy standards. The material is appropriate for grades 8-12. Lessons are available for download in PDF format.

  13. The Soft XRay/Microwave Ratio of Solar and Stellar Flares and Coronae

    E-print Network

    Guedel, Manuel

    as thermal radiations of coronal plasmas. On the other hand, the microwave emission of stars and solar flares. Some coronae of active stars of late spectral type are detected microwave sources. The microwaveThe Soft X­Ray/Microwave Ratio of Solar and Stellar Flares and Coronae A. O. Benz Institute

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

    SciTech Connect

    Inoue, S.; Magara, T.; Choe, G. S. [School of Space Research, Kyung Hee University 1, Seocheon-dong, Giheung-gu, Yongin, Gyeonggi-do 446-701 (Korea, Republic of); Hayashi, K. [W. W. Hansen Experimental Physics Laboratory, Stanford University, Stanford, CA 94305 (United States); Shiota, D., E-mail: inosato@khu.ac.kr [Solar-Terrestrial Environment Laboratory, Nagoya University Furo-cho, Chikusa-ku, Nagoya 464-8601 (Japan)

    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.

  15. Observations of the 12.3 micron Mg I emission line during a major solar flare

    NASA Technical Reports Server (NTRS)

    Deming, Drake; Jennings, Donald E.; Osherovich, Vladimir; Wiedemann, Gunter; Hewagama, Tilak

    1990-01-01

    The extremely Zeeman-sensitive 12.32 micron Mg I solar emission line was observed during a 3B/X5.7 solar flare on October 24, 1989. When compared to postflare values, Mg I emission-line intensity in the penumbral flare ribbon was 20 percent greater at the peak of the flare in soft X-rays, and the 12 micron continuum intensity was 7 percent greater. The flare also excited the emission line in the umbra where it is normally absent. The umbral flare emission exhibits a Zeeman splitting 200 G less than the adjacent penumbra, suggesting that it is excited at higher altitude. The absolute penumbral magnetic field strength did not change by more than 100 G between the flare peak and postflare period. However, a change in the inclination of the field lines, probably related to the formation and development of the flare loop system, was seen.

  16. Influence of solar activity on fibrinolysis and fibrinogenolysis. [statistical correlation between solar flare and blood coagulation indices

    NASA Technical Reports Server (NTRS)

    Marchenko, V. I.

    1974-01-01

    During periods of high solar activity fibrinolysis and fibrinogenolysis are increased. A direct correlative relationship is established between the indices of fibrinolysis, fibrinogenolysis and solar flares which were recorded two days before the blood was collected for analysis.

  17. Global Energetics of Solar Flares: II. Thermal Energies

    NASA Astrophysics Data System (ADS)

    Aschwanden, Markus J.; Boerner, Paul; Ryan, Daniel; Caspi, Amir; McTiernan, James M.; Warren, Harry P.

    2015-03-01

    We present the second part of a project on the global energetics of solar flares and coronal mass ejections that includes about 400 M- and X-class flares observed with the Atmospheric Imaging Assembly (AIA) onboard the Solar Dynamics Observatory (SDO) during the first 3.5 yr of its mission. In this Paper II we compute the differential emission measure (DEM) distribution functions and associated multithermal energies, using a spatially-synthesized Gaussian DEM forward-fitting method. The multithermal DEM function yields a significantly higher (by an average factor of ?14), but more comprehensive (multi-)thermal energy than an isothermal energy estimate from the same AIA data. We find a statistical energy ratio of {{E}th}/{{E}diss} ? 2-40% between the multithermal energy Eth and the magnetically dissipated energy Ediss, which is an order of magnitude higher than the estimates of Emslie et al. 2012. For the analyzed set of M- and X-class flares we find the following physical parameter ranges: L={{10}8.2}{{-10}9.7} cm for the length scale of the flare areas, {{T}p}={{10}5.7}{{-10}7.4} K for the DEM peak temperature, {{T}w}={{10}6.8}{{-10}7.6} K for the emission measure-weighted temperature, {{n}p}={{10}10.3}-{{10}11.8} cm-3 for the average electron density, E{{M}p}={{10}47.3}-{{10}50.3} cm-3 for the DEM peak emission measure, and {{E}th}={{10}26.8}-{{10}32.0} erg for the multithermal energies. The deduced multithermal energies are consistent with the RTV scaling law {{E}th,RTV}=7.3× {{10}-10} Tp3Lp2, which predicts extremal values of {{E}th,max }? 1.5× {{10}33} erg for the largest flare and {{E}th,min }? 1× {{10}24} erg for the smallest coronal nanoflare. The size distributions of the spatial parameters exhibit powerlaw tails that are consistent with the predictions of the fractal-diffusive self-organized criticality model combined with the RTV scaling law.

  18. Global Energetics of Solar Flares. I. Magnetic Energies

    NASA Astrophysics Data System (ADS)

    Aschwanden, Markus J.; Xu, Yan; Jing, Ju

    2014-12-01

    We present the first part of a project on the global energetics of solar flares and coronal mass ejections that includes about 400 M- and X-class flares observed with Atmospheric Imaging Assembly (AIA) and Helioseismic and Magnetic Imager (HMI) on board the Solar Dynamics Observatory (SDO). We calculate the potential (Ep ), the nonpotential (E np) or free energies (E free = E np - Ep ), and the flare-dissipated magnetic energies (E diss). We calculate these magnetic parameters using two different NLFFF codes: the COR-NLFFF code uses the line-of-sight magnetic field component Bz from HMI to define the potential field, and the two-dimensional (2D) coordinates of automatically detected coronal loops in six coronal wavelengths from AIA to measure the helical twist of coronal loops caused by vertical currents, while the PHOT-NLFFF code extrapolates the photospheric three-dimensional (3D) vector fields. We find agreement between the two codes in the measurement of free energies and dissipated energies within a factor of <~ 3. The size distributions of magnetic parameters exhibit powerlaw slopes that are approximately consistent with the fractal-diffusive self-organized criticality model. The magnetic parameters exhibit scaling laws for the nonpotential energy, Enp \\propto E_p1.02, for the free energy, Efree \\propto E_p1.7 and Efree \\propto B\\varphi 1.0 L1.5, for the dissipated energy, Ediss \\propto E_p1.6 and Ediss \\propto Efree0.9, and the energy dissipation volume, V \\propto Ediss1.2. The potential energies vary in the range of Ep = 1 × 1031-4 × 1033 erg, while the free energy has a ratio of E free/Ep ? 1%-25%. The Poynting flux amounts to F flare ? 5 × 108-1010 erg cm-2 s-1 during flares, which averages to F AR ? 6 × 106 erg cm-2 s-1 during the entire observation period and is comparable with the coronal heating rate requirement in active regions.

  19. The Human Impact of Solar Flares and Magnetic Storms

    NASA Astrophysics Data System (ADS)

    Joselyn, Jo Ann

    1998-01-01

    The Sun shines, and Earth and its inhabitants benefit. But the Sun radiates more than light, and these radiations are variable over time scales of seconds to days to years. The consequences for people range from glorious celestial displays-auroras-to subtle but potentially damaging effects on the technological systems that are increasingly important for daily living. For example, electric power transmission systems and communication links have proven vulnerable to solar phenomena. And outside of Earth's protective atmosphere and magnetic shield, there is a small but genuine risk of a solar energetic particle burst that would be lethal to satellite sensors and command and control systems and astronauts. It has been known since the time of Galileo that the Sun is neither featureless nor steady. Besides ordinary sunlight, there are three classes of solar emanations that can be directly associated with effects at Earth-photon radiation from solar flares, solar energetic particles, and inhomogeneties in the solar wind that drive magnetic storms. Below, the emanations are summarized and their effects are described.

  20. Statistics and classification of the microwave zebra patterns associated with solar flares

    SciTech Connect

    Tan, Baolin; Tan, Chengming; Zhang, Yin [Key Laboratory of Solar Activity, National Astronomical Observatories of Chinese Academy of Sciences, Beijing 100012 (China); Mészárosová, H.; Karlický, M., E-mail: bltan@nao.cas.cn [Astronomical Institute of the Academy of Sciences of the Czech Republic, Ondrejov 15165 (Czech Republic)

    2014-01-10

    The microwave zebra pattern (ZP) is the most interesting, intriguing, and complex spectral structure frequently observed in solar flares. A comprehensive statistical study will certainly help us to understand the formation mechanism, which is not exactly clear now. This work presents a comprehensive statistical analysis of a big sample with 202 ZP events collected from observations at the Chinese Solar Broadband Radio Spectrometer at Huairou and the Ond?ejov Radiospectrograph in the Czech Republic at frequencies of 1.00-7.60 GHz from 2000 to 2013. After investigating the parameter properties of ZPs, such as the occurrence in flare phase, frequency range, polarization degree, duration, etc., we find that the variation of zebra stripe frequency separation with respect to frequency is the best indicator for a physical classification of ZPs. Microwave ZPs can be classified into three types: equidistant ZPs, variable-distant ZPs, and growing-distant ZPs, possibly corresponding to mechanisms of the Bernstein wave model, whistler wave model, and double plasma resonance model, respectively. This statistical classification may help us to clarify the controversies between the existing various theoretical models and understand the physical processes in the source regions.

  1. Statistics and Classification of the Microwave Zebra Patterns Associated with Solar Flares

    NASA Astrophysics Data System (ADS)

    Tan, Baolin; Tan, Chengming; Zhang, Yin; Mészárosová, H.; Karlický, M.

    2014-01-01

    The microwave zebra pattern (ZP) is the most interesting, intriguing, and complex spectral structure frequently observed in solar flares. A comprehensive statistical study will certainly help us to understand the formation mechanism, which is not exactly clear now. This work presents a comprehensive statistical analysis of a big sample with 202 ZP events collected from observations at the Chinese Solar Broadband Radio Spectrometer at Huairou and the Ond?ejov Radiospectrograph in the Czech Republic at frequencies of 1.00-7.60 GHz from 2000 to 2013. After investigating the parameter properties of ZPs, such as the occurrence in flare phase, frequency range, polarization degree, duration, etc., we find that the variation of zebra stripe frequency separation with respect to frequency is the best indicator for a physical classification of ZPs. Microwave ZPs can be classified into three types: equidistant ZPs, variable-distant ZPs, and growing-distant ZPs, possibly corresponding to mechanisms of the Bernstein wave model, whistler wave model, and double plasma resonance model, respectively. This statistical classification may help us to clarify the controversies between the existing various theoretical models and understand the physical processes in the source regions.

  2. Solar flare protons and alpha particles during the last three solar cycles

    NASA Technical Reports Server (NTRS)

    Goswami, J. N.; Mcguire, R. E.; Reedy, R. C.; Lal, D.; Jha, R.

    1988-01-01

    This paper presents solar-flare-associated proton and alpha-particle fluxes determined for major events from October 1972 through March 1987 (the period that represents the last part of solar cycle 20 and the whole of solar cycle 21), using data obtained by detectors on board the IMP-7 and IMP-8 satellites, along with earlier obtained data for cycle 20. It was found that the average omnidirectional flux of protons with kinetic energy above 10 MeV for cycle 21 (64/sq cm per sec) is lower than the corresponding number for cycle 20 (92/sq cm per sec) and for the cycle 19 (378/sq cm per sec). No definitive correlation was found to exist between cycle-averaged solar flare proton fluxes and peak sunspot numbers.

  3. Solar Wind Density Turbulence and Solar Flare Electron Transport from the Sun to the Earth

    Microsoft Academic Search

    Hamish A. S. Reid; Eduard P. Kontar

    2010-01-01

    Solar flare accelerated electron beams propagating away from the Sun can interact with the turbulent interplanetary media, producing plasma waves and Type III radio emission. These electron beams are detected near the Earth with a double power-law energy spectrum. We simulate electron beam propagation from the Sun to the Earth in the weak turbulent regime taking into account the self-consistent

  4. Structure of impulsive phase of solar flares from microwave observations

    NASA Technical Reports Server (NTRS)

    Petrosian, V.

    1981-01-01

    Variation of the microwave intensity and spectrum due to gyro-synchrotron radiation from semi-relativistic particles injected at the top of a closed magnetic loop is described. Using the recent high spatial resolution X-ray observations from the HXIS experiment of Solar Maximum Mission and from observations by the Very Large Array (VLA), it is shown that the high microwave brightness observed at the top of the flare loop can come about if (1) the magnetic field from top to footpoints of the loop does not increase very rapidly, and (2) the accelerated particles injected in the loop have a nearly isotropic pitch angle distribution. The limits on the rate of increase of the magnetic field and/or the average pitch angle depend on the geometry and location of the loop on the solar disk.

  5. Spontaneous Catastrophic Onset of Fast Magnetic Reconnection and Solar Flares

    NASA Astrophysics Data System (ADS)

    Cassak, P. A.; Drake, J. F.; Shay, M. A.

    2006-05-01

    The mechanism triggering the onset of fast magnetic reconnection, the driver of solar eruptions, has long been elusive. We have found that for a wide range of resistivities, both the collisional ("Sweet-Parker", exceedingly slow) and collisionless ("Hall", fast) reconnection solutions are independently valid for identical values of the resistivity, a condition known as bistability. However, when the Sweet-Parker layer becomes thinner than the ion skin depth, the Hall effect controls the dynamics and the Sweet-Parker solution ceases to exist. A catastrophic transition to Hall reconnection ensues, increasing the rate of reconnection by many orders of magnitude. In the corona, the transition is spontaneous because the current sheet naturally becomes thinner during Sweet-Parker reconnection as stronger magnetic fields are convected toward the X-line. We present numerical simulations confirming the model and show that predictions of onset conditions for solar flares are consistent with observations.

  6. Particle Densities within the Acceleration Region of a Solar Flare

    NASA Astrophysics Data System (ADS)

    Krucker, Säm; Battaglia, Marina

    2014-01-01

    The limb flare SOL2012-07-19T05:58 (M7.7) provides the best example of a non-thermal above-the-loop-top hard X-ray source with simultaneous observations by the Reuven Ramaty High Energy Solar Spectroscopic Imager (RHESSI) and the Atmospheric Imaging Assembly on board the Solar Dynamic Observatory. By combining the two sets of observations, we present the first direct measurement of the thermal proton density and non-thermal electron density within the above-the-loop-top source where particle acceleration occurs. We find that both densities are of the same order of magnitude of a few times 109 cm-3, about 30 times lower than the density in the underlying thermal flare loops. The equal densities indicate that the entire electron population within the above-the-loop-top source is energized. While the derived densities depend on the unknown source depth and filling factor, the ratio of these two densities does not. Within the uncertainties, the ratio is one for a low energy cutoff of the non-thermal electron spectrum between 10 and 15 keV. RHESSI observations only constrain the cutoff energy to below ~15 keV, leaving the spectral shape of the electrons within the above-the-loop-top source at lower energies unknown. Nevertheless, these robust results strongly corroborate earlier findings that the above-the-loop-top source is the acceleration region where a bulk energization process acts on all electrons.

  7. Solar energetic electrons related to the 28 October 2003 flare

    NASA Astrophysics Data System (ADS)

    Klassen, A.; Krucker, S.; Kunow, H.; Müller-Mellin, R.; Wimmer-Schweingruber, R.; Mann, G.; Posner, A.

    2005-09-01

    We investigate the solar origin of near-relativistic electrons and protons during the X17.2/4B flare as observed by the Comprehensive Suprathermal and Energetic Particle Analyser (COSTEP) and Three-Dimensional Plasma (3DP) analyzer experiments on board the SOHO and Wind spacecraft. These observations are combined with ground- and space-based spectral radio data obtained by the Potsdam spectrograph and the Wind/Waves instrument. Additionally, we use measurements of relativistic protons (ground-level event (GLE)) by neutron monitors (Kiel and Moscow). Timing and electron energy spectrum analysis suggest that there are three separate stages of electron injection into interplanetary space: (1) An injection of radio type III-producing electrons is observed first; (2) an impulsive injection with an almost symmetric time profile with a short duration (˜18 min) is released ˜11 min later, followed by (3) a gradual, long (>1 hour) lasting injection, with an onset ˜25 min after the first type III burst. While the first escaping type III-producing electrons are more likely related to the reconnection processes during the impulsive flare phase, the association of the two delayed electron injections with solar events is not well understood.

  8. Relativistic-Electron-Dominated Solar Flares Observed by Fermi/GBM

    NASA Astrophysics Data System (ADS)

    Shih, Albert Y.; Schwartz, R. A.; Dennis, B. R.

    2013-07-01

    Up to tens of percent of the energy released in solar flares goes into accelerating electrons above ~10 keV and ions above ~1 MeV, and the impulsive heating of the ambient solar atmosphere by these particles is partially or wholly responsible for the production of hot flare plasmas (up to ~50 MK). Although flares can accelerate electrons to relativistic energies, in even large flares the typical falling power-law energy spectrum means that the plasma is primarily heated by the much larger number of low-energy electrons. However, there have been flares observed where the electron energy spectra have high low-energy cutoffs (well above ~100 keV), which significantly changes the electron energies responsible for heating and modifies the usual conception of energy transport in a flare. A systematic study of a range of relativistic-electron-dominated flares can improve our understanding of the relevant acceleration processes and how they may differ from those in "typical" flares. We search the Fermi/GBM data set for such flares based on the electron-associated X-ray/gamma-ray bremsstrahlung emission, making use of an improved background-subtraction approach to improve the ability to detect weaker flares. We present the fitted parameters for the relativistic-electron spectrum and their evolution over time, and compare against RHESSI observations and other instruments when available. We also discuss these events in the context of previously observed correlations between relativistic-electron acceleration and ion acceleration in flares.

  9. Relativistic-Electron-Dominated Solar Flares Observed by Fermi/GBM

    NASA Astrophysics Data System (ADS)

    Shih, A. Y.; Schwartz, R. A.; Dennis, B. R.

    2013-12-01

    Up to tens of percent of the energy released in solar flares goes into accelerating electrons above ~10 keV and ions above ~1 MeV, and the impulsive heating of the ambient solar atmosphere by these particles is partially or wholly responsible for the production of hot flare plasmas (up to ~50 MK). Although flares can accelerate electrons to relativistic energies, in even large flares the typical falling power-law energy spectrum means that the plasma is primarily heated by the much larger number of low-energy electrons. However, there have been flares observed where the electron energy spectra have high low-energy cutoffs (well above ~100 keV), which significantly changes the electron energies responsible for heating and modifies the usual conception of energy transport in a flare. A systematic study of a range of relativistic-electron-dominated flares can improve our understanding of the relevant acceleration processes and how they may differ from those in "typical" flares. We search the Fermi/GBM data set for such flares based on the electron-associated X-ray/gamma-ray bremsstrahlung emission, making use of an improved background-subtraction approach to improve the ability to detect weaker flares. We present the fitted parameters for the relativistic-electron spectrum and their evolution over time, and compare against RHESSI observations and other instruments when available. We also discuss these events in the context of previously observed correlations between relativistic-electron acceleration and ion acceleration in flares.

  10. PRE-FLARE ACTIVITY AND MAGNETIC RECONNECTION DURING THE EVOLUTIONARY STAGES OF ENERGY RELEASE IN A SOLAR ERUPTIVE FLARE

    SciTech Connect

    Joshi, Bhuwan [Udaipur Solar Observatory, Physical Research Laboratory, Udaipur 313 001 (India); Veronig, Astrid M. [IGAM/Institute of Physics, University of Graz, A-8010 Graz (Austria); Lee, Jeongwoo [Physics Department, New Jersey Institute of Technology, Newark, NJ 07102 (United States); Bong, Su-Chan; Cho, Kyung-Suk [Korea Astronomy and Space Science Institute, Daejeon 305-348 (Korea, Republic of); Tiwari, Sanjiv Kumar [Max-Planck-Institut fuer Sonnensystemforschung, 37191 Katlenburg-Lindau (Germany)

    2011-12-20

    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 {approx}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 {approx}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 {approx}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.

  11. What Causes The Increasing Submillimeter Spectral Component Of Solar Flares?

    NASA Astrophysics Data System (ADS)

    Silva, Adriana V. R.; Share, G. H.; Murphy, R. J.; Costa, J. E.; Gimenez de Castro, C. G.; Raulin, J. P.; Kaufmann, P.

    2007-05-01

    The flare on November 2nd, 2003, at 17:17 UT, occurred on the very active region 486 located at S14W56. This X8.3 flare was simultaneously detected by RHESSI and the Solar Submillimeter Telescope (SST) at 212 and 405 GHz. The time profile of the submm emission resembles that of the high energy X-rays observed by RHESSI and the microwaves observed by OVSA. Moreover, the centroid position of the submm radiation is seen to originate within the same flaring loops of the ultraviolet and X-rays sources. Nevertheless, the submm spectra are distinct from the usual microwave spectra, showing a flux density increase with frequency. Three possibilities to explain this increasing radio spectra are discussed: (1) bremsstrahlung from thermal electrons, (2) gyrosynchrotron radiation from accelerated electrons, and finally (3) gyrosynchrotron emission from the positrons produced by pion or radioactive decay after nuclear interactions. It is possible to model the emission as thermal, the problem, however, is to explain the good agreement of the submm temporal profile with those of the non-thermal emission seen in microwaves and hard X-rays. If the submm emission is to be explained by gyrosynchrotron from the same population of accelerated electrons that emit hard X-rays, however, a discrepancy of 300 times more electrons between 40 keV and 20 MeV is found between the fit to the high frequency radio spectra and what was observed by RHESSI, even for a 3000 G field. Finally, synchrotron emission from positrons requires 3.3 - 10 × 105 more positrons than what is inferred from X and gamma-ray observations, thus ruling this out as a possible explanation. In summary, all possibilities listed above run into problems when trying to explain the increasing submm spectra, because of the extreme source parameters required. Therefore, the cause of this new component still remains unknown.

  12. Influence of solar flare's location and heliospheric current sheet on the associated shock's arrival at Earth

    Microsoft Academic Search

    Xinhua Zhao; Xueshang Feng; Chin-Chun Wu

    2007-01-01

    We study the source locations of 130 solar flare-type II radio burst events with the associated interplanetary shocks observed by L1 spacecraft (type A events) and 217 flare-type II events without such shocks observed at L1 (type B events) during February 1997-August 2002. In particular, we investigate the relative positions between the flare sources, the heliospheric current sheet (HCS), and

  13. Influence of solar flare's location and heliospheric current sheet on the associated shock's arrival at Earth

    Microsoft Academic Search

    Xinhua Zhao; Xueshang Feng; Chin-Chun Wu

    2007-01-01

    We study the source locations of 130 solar flare-type II radio burst events with the associated interplanetary shocks observed by L1 spacecraft (type A events) and 217 flare-type II events without such shocks observed at L1 (type B events) during February 1997–August 2002. In particular, we investigate the relative positions between the flare sources, the heliospheric current sheet (HCS), and

  14. Internal Shocks in the Magnetic Reconnection Jet in Solar Flares

    NASA Astrophysics Data System (ADS)

    Tanuma, S.; Shibata, K.

    2004-01-01

    The satellites such as Yohkoh and RHESSI observe the X- and gamma-ray emissions from the high energy particles in solar flare: for example at looptop and foot points of impulsive flare. In this paper we suggest that the multiple fast shock are created in the reconnection jet and they create the high energy particles by performing two-dimensional numerical resistive magnetohydrodynamic simulations. As the results we find that the current sheet becomes thin by tearing instability and it collapses to Sweet-Parker current sheet. The thin current sheet becomes unstable to the tearing instability again. The fast reconnection starts immediately after the plasmoid-ejection which are created by the secondary tearing instability. The internal shocks are created inside the reconnection jet due to the nonsteady plasmoid-ejection created by the secondary tearing instability. In the next phase the reconnection jet starts to oscillate which is due to Kelvin-Helmholtz instability or turbulence reconnection. The reconnection jet collides with two standing slow shocks so that the fast shocks are created as the oblique shocks. The fast shocks created by the magnetic reconnection is possible sites for the particle acceleration.

  15. RETURN CURRENTS AND ENERGY TRANSPORT IN THE SOLAR FLARING ATMOSPHERE

    SciTech Connect

    Codispoti, Anna; Torre, Gabriele; Piana, Michele; Pinamonti, Nicola [Dipartimento di Matematica, Universita di Genova, via Dodecaneso 35, I-16146 Genova (Italy)

    2013-08-20

    According to the standard Ohmic perspective, the injection of accelerated electrons into the flaring region violates local charge equilibrium and therefore, in response, return currents are driven by an electric field to equilibrate such charge violation. In this framework, the energy loss rate associated with these local currents has an Ohmic nature and significantly shortens the accelerated electron path. In the present paper, we adopt a different viewpoint and, specifically, we study the impact of the background drift velocity on the energy loss rate of accelerated electrons in solar flares. We first utilize the Rutherford cross-section to derive the formula of the energy loss rate when the collisional target has a finite temperature and the background instantaneously and coherently moves up to equilibrate the electron injection. We then use the continuity equation for electrons and imaging spectroscopy data provided by RHESSI to validate this model. We show that this new formula for the energy loss rate provides a better fit of the experimental data with respect to the model based on the effects of standard Ohmic return currents.

  16. The role of the big flare syndrome in correlations of solar energetic proton fluxes and associated microwave burst parameters

    Microsoft Academic Search

    S. W. Kahler

    1982-01-01

    A hypothesis based on the big flare syndrome (BFS) is proposed which attempts to explain the observed correlations between solar energetic proton fluxes and microwave burst parameters in terms of the statistical correlation between solar flare energy release and the magnitude of flare energy manifestations in general. Correlations between peak prompt proton fluxes and associated microwave burst parameters are examined

  17. Recent Advances in Understanding Particle Acceleration Processes in Solar Flares

    E-print Network

    Zharkova, Valentina V; Benz, Arnold O; Browning, Phillippa; Dauphin, Cyril; Emslie, A Gordon; Fletcher, Lyndsay; Kontar, Eduard P; Mann, Gottfried; Onofri, Marco; Petrosian, Vahe; Turkmani, Rim; Vilmer, Nicole; Vlahos, Loukas

    2011-01-01

    We review basic theoretical concepts in particle acceleration, with particular emphasis on processes likely to occur in regions of magnetic reconnection. Several new developments are discussed, including detailed studies of reconnection in three-dimensional magnetic field configurations (e.g., current sheets, collapsing traps, separatrix regions) and stochastic acceleration in a turbulent environment. Fluid, test-particle, and particle-in-cell approaches are used and results compared. While these studies show considerable promise in accounting for the various observational manifestations of solar flares, they are limited by a number of factors, mostly relating to available computational power. Not the least of these issues is the need to explicitly incorporate the electrodynamic feedback of the accelerated particles themselves on the environment in which they are accelerated. A brief prognosis for future advancement is offered.

  18. Optimal Electron Energies for Driving Chromospheric Evaporation in Solar Flares

    E-print Network

    Reep, Jeffrey; Alexander, David

    2015-01-01

    In the standard model of solar flares, energy deposition by a beam of electrons drives strong chromospheric evaporation leading to a significantly denser corona and much brighter emission across the spectrum. Chromospheric evaporation was examined in great detail by Fisher, Canfield, & McClymont (1985a,b,c), who described a distinction between two different regimes, termed explosive and gentle evaporation. In this work, we examine the importance of electron energy and stopping depths on the two regimes and on the atmospheric response. We find that with explosive evaporation, the atmospheric response does not depend strongly on electron energy. In the case of gentle evaporation, lower energy electrons are significantly more efficient at heating the atmosphere and driving up-flows sooner than higher energy electrons. We also find that the threshold between explosive and gentle evaporation is not fixed at a given beam energy flux, but also depends strongly on the electron energy and duration of heating. Furt...

  19. Recent Advances in Understanding Particle Acceleration Processes in Solar Flares

    NASA Astrophysics Data System (ADS)

    Zharkova, V. V.; Arzner, K.; Benz, A. O.; Browning, P.; Dauphin, C.; Emslie, A. G.; Fletcher, L.; Kontar, E. P.; Mann, G.; Onofri, M.; Petrosian, V.; Turkmani, R.; Vilmer, N.; Vlahos, L.

    2011-09-01

    We review basic theoretical concepts in particle acceleration, with particular emphasis on processes likely to occur in regions of magnetic reconnection. Several new developments are discussed, including detailed studies of reconnection in three-dimensional magnetic field configurations (e.g., current sheets, collapsing traps, separatrix regions) and stochastic acceleration in a turbulent environment. Fluid, test-particle, and particle-in-cell approaches are used and results compared. While these studies show considerable promise in accounting for the various observational manifestations of solar flares, they are limited by a number of factors, mostly relating to available computational power. Not the least of these issues is the need to explicitly incorporate the electrodynamic feedback of the accelerated particles themselves on the environment in which they are accelerated. A brief prognosis for future advancement is offered.

  20. Magnetic and dynamical photospheric disturbances observed during an M3.2 solar flare

    E-print Network

    Kuckein, C; Sainz, R Manso

    2015-01-01

    This letter reports on a set of full-Stokes spectropolarimetric observations in the near infrared He I 10830 A spectral region covering the pre-, flare, and post-flare phases of an M3.2 class solar flare. The flare originated on 2013 May 17 and belonged to active region NOAA 11748. We detected strong He I 10830 A emission in the flare. The red component of the He I triplet peaks at an intensity ratio to the continuum of about 1.86. During the flare, He I Stokes V is substantially larger and appears reversed compared to the usually larger Si I Stokes V profile. The photospheric Si I inversions of the four Stokes profiles reveal the following: (1) the magnetic field strength in the photosphere decreases or is even absent during the flare phase, as compared to the pre-flare phase. However, this decrease is not permanent. After the flare the magnetic field recovers its pre-flare configuration in a short time (i.e., in 30 minutes after the flare). (2) In the photosphere, the line-of-sight velocities show a regular...

  1. Thermal Structure of Supra-Arcade Plasma in Two Solar Flares

    NASA Technical Reports Server (NTRS)

    Reeves, Katharine K.; Savage, Sabrina; McKenzie, David E.; Weber, Mark A.

    2012-01-01

    In this work, we use Hinode/XRT and SDO/AIA data to determine the thermal structure of supra-arcade plasma in two solar flares. The first flare is a Ml.2 flare that occurred on November 5, 2010 on the east limb. This flare was one of a series of flares from AR 11121, published in Reeves & Golub (2011). The second flare is an XI.7 flare that occurred on January 27, 2012 on the west limb. This flare exhibits visible supra-arcade downflows (SADs), where the November 2010 flare does not. For these two flares we combine XRT and AlA data to calculate DEMs of each pixel in the supra-arcade plasma, giving insight into the temperature and density structures in the fan of plasma above the post-flare arcade. We find in each case that the supra-arcade plasma is around 10 MK, and there is a marked decrease in the emission measure in the SADs. We also compare the DEMs calculated with the combined AIA/XRT dataset to those calculated using AIA alone.

  2. Solar-wind and solar-flare maturation of the lunar regolith

    NASA Technical Reports Server (NTRS)

    Bibring, J. P.; Borg, J.; Vassent, B.; Burlingame, A. L.; Langevin, Y.; Maurette, M.

    1975-01-01

    Detailed predictions concerning the depth and time-dependent accumulation of solar-wind effects and solar-flare tracks in lunar dust grains were obtained by use of an adaptation of a Monte Carlo soil-mixing computer code described by Duraud et al. (1975). The predictions are compared to experimental measurements obtained by analyzing lunar dust grains as well as artificially irradiated minerals by a variety of techniques. A study of amorphous coatings of solar-wind radiation-damaged material on certain lunar grains sets limits on the integrated residence time of these grains in the ancient solar wind. Other topics discussed include solar wind maturation, the peculiar shape of the experimental distribution of central track densities in 50-micron grains, and the interpretation of both track gradients in 50-micron feldspars and the relatively 'low' concentration of solar-wind species implanted in ilmenite grains.

  3. Particle densities within the acceleration region of a solar flare

    SciTech Connect

    Krucker, Säm; Battaglia, Marina, E-mail: krucker@ssl.berkeley.edu [University of Applied Sciences and Arts Northwestern Switzerland, CH-5210 Windisch (Switzerland)

    2014-01-01

    The limb flare SOL2012-07-19T05:58 (M7.7) provides the best example of a non-thermal above-the-loop-top hard X-ray source with simultaneous observations by the Reuven Ramaty High Energy Solar Spectroscopic Imager (RHESSI) and the Atmospheric Imaging Assembly on board the Solar Dynamic Observatory. By combining the two sets of observations, we present the first direct measurement of the thermal proton density and non-thermal electron density within the above-the-loop-top source where particle acceleration occurs. We find that both densities are of the same order of magnitude of a few times 10{sup 9} cm{sup –3}, about 30 times lower than the density in the underlying thermal flare loops. The equal densities indicate that the entire electron population within the above-the-loop-top source is energized. While the derived densities depend on the unknown source depth and filling factor, the ratio of these two densities does not. Within the uncertainties, the ratio is one for a low energy cutoff of the non-thermal electron spectrum between 10 and 15 keV. RHESSI observations only constrain the cutoff energy to below ?15 keV, leaving the spectral shape of the electrons within the above-the-loop-top source at lower energies unknown. Nevertheless, these robust results strongly corroborate earlier findings that the above-the-loop-top source is the acceleration region where a bulk energization process acts on all electrons.

  4. DETERMINATION OF STOCHASTIC ACCELERATION MODEL CHARACTERISTICS IN SOLAR FLARES

    SciTech Connect

    Chen, Qingrong; Petrosian, Vahé [Department of Physics, Stanford University, Stanford, CA 94305 (United States)

    2013-11-01

    Following our recent paper, we have developed an inversion method to determine the basic characteristics of the particle acceleration mechanism directly and non-parametrically from observations under the leaky box framework. Earlier, we demonstrated this method for obtaining the energy dependences of the escape time and pitch angle scattering time. Here, by converting the Fokker-Planck equation to its integral form, we derive the energy dependences of the energy diffusion coefficient and direct acceleration rate for stochastic acceleration in terms of the accelerated and escaping particle spectra. Combining the regularized inversion method of Piana et al. and our procedure, we relate the acceleration characteristics in solar flares directly to the count visibility data from RHESSI. We determine the timescales for electron escape, pitch angle scattering, energy diffusion, and direct acceleration at the loop top acceleration region for two intense solar flares based on the regularized electron flux spectral images. The X3.9 class event shows dramatically different energy dependences for the acceleration and scattering timescales, while the M2.1 class event shows a milder difference. The discrepancy between the M2.1 class event and the stochastic acceleration model could be alleviated by a turbulence spectrum that is much steeper than the Kolmogorov-type spectrum. A likely explanation of the X3.9 class event could be that the escape of electrons from the acceleration region is not governed by a random walk process, but instead is affected by magnetic mirroring, in which the scattering time is proportional to the escape time and has an energy dependence similar to the energy diffusion time.

  5. PROPERTIES OF THE ACCELERATION REGIONS IN SEVERAL LOOP-STRUCTURED SOLAR FLARES

    E-print Network

    Piana, Michele

    spectroscopy observations, we analyze electron flux maps for a number of extended coronal loop flares. For eachPROPERTIES OF THE ACCELERATION REGIONS IN SEVERAL LOOP-STRUCTURED SOLAR FLARES Jingnan Guo1 , A event, we fit a collisional model with an extended acceleration region to the observed variation of loop

  6. Discrepancies between empirical and theoretical models of the flaring solar chromosphere and their possible resolution

    NASA Technical Reports Server (NTRS)

    Emslie, G. A.; Brown, J. C.; Machado, M. E.

    1980-01-01

    Models of the solar chromosphere during flaring deduced theoretically or empirically are compared. Marked discrepancies are noted and various reasons are offered to explain their existence. A means is presented for testing theoretical heating models (electron heating) by analyzing the net energy loss rates in (observed) empirical atmospheres and inverting the flare energy equation to deduce the parameters of the supposed heating mechanism.

  7. Statistical properties of H ? flares in relation to sunspots and active regions in the cycle 23

    Microsoft Academic Search

    S. I. Zharkov; V. V. Zharkova

    2011-01-01

    The statistical properties of H? flare occurrences compared with those of sunspot and active region areas in the cycle 23. The flare numbers in the cycle 23 of all significances and locations were obtained from the Solar Geophysical Data (SGD) and the other data were taken from the automated Solar Feature Catalogues (SFC, http:\\/\\/solar.inf.brad.ac.uk). The average monthly flare occurrences during

  8. Observations of interplanetary energetic charged particles from gamma-ray line solar flares

    NASA Technical Reports Server (NTRS)

    Pesses, M. E.; Klecker, B.; Gloeckler, G.; Hovestadt, D.

    1981-01-01

    Observations of interplanetary energetic ions from the 7 June, 21 June and 1 July 1980 gamma ray line solar flares are presented. The observations are from the Max-Planck-Institut/University of Maryland Ultra Low Energy Wide Angle Telescope aboard the ISEE-3 spacecraft. Both June flares produced relatively low intensity proton events at earth with peak intensities at 10-20 MeV approximately 5 x .01 protons square cm sec sr MeV)-1. Neither flare showed evidence of being enriched in either 3He or Fe at approximately 1 MeV/nucleon. The 1 July flare produced no observable ion or electron enhancements.

  9. Upper limits on the solar-neutron flux at the Yangbajing neutron monitor from BATSE-detected solar flares

    E-print Network

    H. Tsuchiya; H. Miyasaka; E. Takahashi; S. Shimoda; Y. Yamada; I. Kondo; K. Makishima; F. Zhu; Y. Tan; H. Hu; Y. Tang; J. Zhang; H. Lu; X. Meng

    2007-03-16

    The purpose of this work is to search the Yangbajing neutron monitor data obtained between 1998 October and 2000 June for solar neutrons associated with solar flares. Using the onset times of 166 BATSE-detected flares with the GOES peak flux (1 -- 8 \\AA) higher than $1.0 \\times 10^{-5}$ $\\mathrm{Wm^{-2}}$, we prepare for each flare a light curve of the Yangbajing neutron monitor, spanning $\\pm$ 1.5 hours from the BATSE onset time. Based on the light curves, a systematic search for solar neutrons in energies above 100 MeV from the 166 flares was performed. No statistically significant signals due to solar neutrons were found in the present work. Therefore, we put upper limits on the $>$ 100 MeV solar-neutron flux for 18 events consisting of 2 X and 16 M class flares. The calculation assumed a power-law shaped neutron energy spectrum and three types of neutron emission profiles at the Sun. Compared with the other positive neutron detections associated with X-class flares, typical 95% confidence level upper limits for the two X-class flares are found to be comparable to the lowest and second lowest neutron fluxes at the top of the atmosphere.In addition, the upper limits for M-class flares scatter in the range of $10^{-2}$ to 1 neutrons $\\mathrm{cm^{-2}s^{-1}}$. This provides the first upper limits on the solar-neutron flux from M-class solar flares, using space observatories as well as ground-based neutron monitors.

  10. Variation in Nuclear Decay Rates as a Possible Predictor of Solar Flares

    NASA Astrophysics Data System (ADS)

    Sturrock, P. A.; Buncher, J.; Fischbach, E.; Gruenwald, J.; Javorsek, D.; Jenkins, J.; Krause, D.; Mattes, J.

    2009-12-01

    Jenkins and Fischbach (Astroparticle Physics, 31, 407, 2009) have recently found evidence for fluctuations in the decay rates of radioactive isotopes in association with solar flares. Jenkins et al. (Astroparticle Physics, 32, 42, 2010) have also found strong evidence for annual variations in measurements of decay rates acquired at the Brookhaven National Laboratory (BNL) and at the Physikalisch-Technische Bundesanstalt (PTB) in Germany. If these claims are confirmed, they pose important questions in particle physics and in solar physics, with the intriguing possibility that such measurements may lead to procedures for predicting the occurrence of some solar flares. The purpose of this presentation is to discuss these questions. The strongest feature of the variability of isotopic decay rates is an annual variation in both BNL and PTB data. The phases of these variations rule out the possibility that they are due either to the annual variation in temperature or to the annual variation in Sun-Earth distance. However, we found some time ago that the solar neutrino flux, as measured at Earth, is influenced not only by the varying Sun-Earth distance, but also by the variation in the heliospheric latitude of the Sun-Earth vector (Sturrock,Walther, and Wheatland, Astrophys. J., 507, 978, 1998). The phases of the annual variation in the BNL and PTB data are consistent with the combined effect of varying Sun-Earth distance and varying heliospheric latitude. This result suggests that the decay rates may be influenced by solar neutrinos. This interpretation would require a revision of neutrino physics. In order to check this hypothesis, it would clearly be desirable to be able to compare decay data with neutrino data. The difficulty is that the decay-rate variations amount to only a few parts in 10,000. This is far too small a fraction to be detectable in neutrino data. However, we have recently found that there is a close association between variations in the solar neutrino flux and variations in solar irradiance. Hence we may, with caution, use irradiance data as a proxy for neutrino data. This has the advantage that irradiance data has been measured several times a day with very high accuracy for over thirty years. We shall present recent results on the comparison of decay data and irradiance data, and comment on possible processes that might explain these associations. This work was supported by the National Science Foundation through grant AST-0607572.

  11. Radio imaging of solar flares using the very large array - New insights into flare process

    NASA Technical Reports Server (NTRS)

    Kundu, M. R.; Schmahl, E. J.; Vlahos, L.; Velusamy, T.

    1982-01-01

    An interpretation of VLA observations of microwave bursts is presented in an attempt to distinguish between certain models of flares. The VLA observations provide information about the pre-flare magnetic field topology and the existence of mildly relativistic electrons accelerated during flares. Examples are shown of changes in magnetic field topology in the hour before flares. In one case, new bipolar loops appear to emerge, which is an essential component of the model developed by Heyvaerts et al. (1977). In another case, a quadrupole structure, suggestive of two juxtaposed bipolar loops, appears to trigger the flare. Because of the observed diversity of magnetic field topologies in microwave bursts, it is believed that the magnetic energy must be dissipated in more than one way. The VLA observations are clearly providing means for sorting out the diverse flare models.

  12. SDO Captures Release of X1.2 Class Solar Flare - Duration: 15 seconds.

    NASA Video Gallery

    This movie shows imagery from NASA's Solar Dynamics Observatory as the sun emitted an X-class flare on Jan. 7, 2014. The movie shows light in the 1600 Angstrom wavelength showing both sunspots visi...

  13. Multiple Views of X1.4 Solar Flare on July 12, 2012 - Duration: 60 seconds.

    NASA Video Gallery

    This video shows the July 12, 2012 X1.4 class solar flare in a variety of wavelength; 131- Teal colored, 335 - blue colored, 171 - yellow colored and finally a combined wavelength view. All video w...

  14. Solar flare X-ray polarimeter utilizing a large area thin beryllium scattering disk

    NASA Technical Reports Server (NTRS)

    Gotthelf, E.; Hamilton, T.; Novick, R.; Chanan, G.; Emslie, A.; Weisskopf, M.

    1989-01-01

    A model of a solar flare X-ray polarimeter utilizing a large-area thin beryllium scattering disk was developed using Monte Carlo techniques for several classes of solar flares. The solar-flare polarimeter consists of a 30-cm-diam Be disk of about 1/3 of a scattering length thickness, which is surrounded by a cylindrical detector composed of six segmented panels of NaI scintillators, each coupled to 15 photomultiplier tubes. The instrument is sensitive to X-rays from 10 to 100 keV. For a class-M-2 solar flare observed for 10 sec from a balloon at an altitude of 150,000 ft, the minimum detectable polarization at the 99 percent statistical confidence level was found to be 1-6 percent over the energy range 20-100 keV.

  15. Multi-wavelength Observations of Solar Flares with a Constrained Peak X-Ray Flux

    NASA Astrophysics Data System (ADS)

    Bowen, Trevor A.; Testa, Paola; Reeves, Katharine K.

    2013-06-01

    We present an analysis of soft X-ray (SXR) and extreme-ultraviolet (EUV) observations of solar flares with an approximate C8 Geostationary Operational Environmental Satellite (GOES) class. Our constraint on peak GOES SXR flux allows for the investigation of correlations between various flare parameters. We show that the duration of the decay phase of a flare is proportional to the duration of its rise phase. Additionally, we show significant correlations between the radiation emitted in the flare rise and decay phases. These results suggest that the total radiated energy of a given flare is proportional to the energy radiated during the rise phase alone. This partitioning of radiated energy between the rise and decay phases is observed in both SXR and EUV wavelengths. Though observations from the EUV Variability Experiment show significant variation in the behavior of individual EUV spectral lines during different C8 events, this work suggests that broadband EUV emission is well constrained. Furthermore, GOES and Atmospheric Imaging Assembly data allow us to determine several thermal parameters (e.g., temperature, volume, density, and emission measure) for the flares within our sample. Analysis of these parameters demonstrate that, within this constrained GOES class, the longer duration solar flares are cooler events with larger volumes capable of emitting vast amounts of radiation. The shortest C8 flares are typically the hottest events, smaller in physical size, and have lower associated total energies. These relationships are directly comparable with several scaling laws and flare loop models.

  16. MULTI-WAVELENGTH OBSERVATIONS OF SOLAR FLARES WITH A CONSTRAINED PEAK X-RAY FLUX

    SciTech Connect

    Bowen, Trevor A.; Testa, Paola; Reeves, Katharine K., E-mail: tbowen@cfa.harvard.edu [Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, MS 58, Cambridge, MA 02138 (United States)

    2013-06-20

    We present an analysis of soft X-ray (SXR) and extreme-ultraviolet (EUV) observations of solar flares with an approximate C8 Geostationary Operational Environmental Satellite (GOES) class. Our constraint on peak GOES SXR flux allows for the investigation of correlations between various flare parameters. We show that the duration of the decay phase of a flare is proportional to the duration of its rise phase. Additionally, we show significant correlations between the radiation emitted in the flare rise and decay phases. These results suggest that the total radiated energy of a given flare is proportional to the energy radiated during the rise phase alone. This partitioning of radiated energy between the rise and decay phases is observed in both SXR and EUV wavelengths. Though observations from the EUV Variability Experiment show significant variation in the behavior of individual EUV spectral lines during different C8 events, this work suggests that broadband EUV emission is well constrained. Furthermore, GOES and Atmospheric Imaging Assembly data allow us to determine several thermal parameters (e.g., temperature, volume, density, and emission measure) for the flares within our sample. Analysis of these parameters demonstrate that, within this constrained GOES class, the longer duration solar flares are cooler events with larger volumes capable of emitting vast amounts of radiation. The shortest C8 flares are typically the hottest events, smaller in physical size, and have lower associated total energies. These relationships are directly comparable with several scaling laws and flare loop models.

  17. A mechanism for the abundance enhancements of heavy nuclei in solar flare particle events

    NASA Technical Reports Server (NTRS)

    Cartwright, B. G.; Mogro-Campero, A.

    1973-01-01

    A mechanism is proposed to account for the recently reported abundance enhancements of heavy nuclei in solar flares. The mechanism requires two acceleration stages for its operation: First, fully stripped ions are accelerated to suprathermal energies, and subsequently, a fraction of these ions are Fermi accelerated to higher energies. It is shown that because injection into Fermi acceleration is rigidity dependent and the ions may pick up electrons during transport to the Fermi acceleration region, an enhancement of the abundances of heavy nuclei can occur. The degree of the enhancement depends on a number of factors particular to each flare, so that the degree of enhancement may be variable from flare to flare, or may be a function of time within a given flare. In some flares, conditions may be such that no enhancement would be expected.

  18. Radio and soft X-ray investigation of the solar flares of February 4, 1986

    NASA Technical Reports Server (NTRS)

    Ji, Shuchen; Ding, Youji; Chen, Guoqiang; Cao, Wenda

    1993-01-01

    The 3B flare of February 4, 1986 is studied comprehensively. The escape electrons accelerated to 10-100 keV at the top of coronal loop are confirmed by type III bursts. The energetic electron beams moved downward trigger the eruptions in the lower layer of the solar atmosphere. The radio and soft X-ray bursts are interpreted, respectively, by the maser mechanism and evaporation effect. Finally, the important role of energetic electron beams in solar flares is pointed out.

  19. Excitation of Geomagnetic Micropulsations by Means of Ionospheric Conductivity Changes Induced by Solar Flares

    Microsoft Academic Search

    Peter Barry Morris

    1985-01-01

    In this thesis we develop the premise that solar flares with large components in the X-ray and EUV spectra stimulate geomagnetic pulsations in the earth's magnetosphere by means of sudden conductivity changes in the dayside ionosphere. Ground-based observations of 7-22 mHz (Pc4 band) magnetic pulsations are shown to be associated with conductivity enhancements for four selected solar flare events in

  20. Response of the equatorial electrojet to solar flare related X-ray flux enhancements

    Microsoft Academic Search

    G. Manju; K. S. Viswanathan

    2005-01-01

    The response of ionospheric E-region electric fields and currents to solar flare related X-ray flux enhancements are studied at the magnetic equatorial location of Trivandrum (8.5°N, 77°E; dip 0.5°N) using VHF (54.95 MHz) coherent backscatter radar observations in the altitude region of 95-110 km conducted during daytime. The amplitude of the Solar Flare Effects (SFE) observed in the earth's magnetic

  1. Implications of X-ray Observations for Electron Acceleration and Propagation in Solar Flares

    Microsoft Academic Search

    G. D. Holman; M. J. Aschwanden; H. Aurass; M. Battaglia; P. C. Grigis; E. P. Kontar; W. Liu; P. Saint-Hilaire; V. V. Zharkova

    2011-01-01

    High-energy X-rays and ?-rays from solar flares were discovered just over fifty years ago. Since that time, the standard for the interpretation of\\u000a spatially integrated flare X-ray spectra at energies above several tens of keV has been the collisional thick-target model.\\u000a After the launch of the Reuven Ramaty High Energy Solar Spectroscopic Imager (RHESSI) in early 2002, X-ray spectra and

  2. Molecular models need to be tested: the case of a solar flares discoidal HDL model.

    PubMed

    Shih, Amy Y; Sligar, Stephen G; Schulten, Klaus

    2008-06-01

    In the absence of atomic structures of high-density lipoproteins in their lipid-bound states, many molecular models have been produced based on experimental data. Using molecular dynamics, we show that a recently proposed "solar-flares" model of discoidal high-density lipoprotein is implausible. Our simulations show a collapse of the protruding solar-flare loops and a notable protein rearrangement due to an energetically unfavorable orientation of the hydrophobic protein surface toward the aqueous solvent. PMID:18375520

  3. High-temperature phase transition in a plasma and the mechanism of powerful solar flares

    E-print Network

    Fedor V. Prigara

    2006-05-04

    It is shown that the high- temperature phase transition in a plasma gives the mechanism of transition from the highly conductive state to the highly resistive state of a plasma in the `electric circuit' model of solar flares which was first introduced by H.Alfven and P.Carlqvist in 1967. With this addendum, the modern version of the electric circuit model can explain both the fast dissipation of energy and the acceleration of particles in a solar flare.

  4. Power Laws in Solar Flares: Self-Organized Criticality or Turbulence?

    Microsoft Academic Search

    Guido Boffetta; Vincenzo Carbone; Paolo Giuliani; Pierluigi Veltri; Angelo Vulpiani

    1999-01-01

    The statistics of quiescent times tauL between successive bursts of solar flares activity, performed using 20 years of data, displays a power law distribution with exponent alpha~=2.4. This is an indication of an underlying complex dynamics with long correlation times. The observed scaling behavior is in contradiction with the self-organized criticality models of solar flares which predict Poisson-like statistics. Chaotic

  5. Particle acceleration and radiation by direct electric fields in flaring complex solar active regions

    E-print Network

    Anastasiadis, Anastasios

    Particle acceleration and radiation by direct electric fields in flaring complex solar active-Meudon, 92195 Meudon Cedex, FRANCE Abstract The acceleration and radiation of solar energetic particles with the existing observations. 1 Introduction The approach used for particle acceleration models proposed for solar

  6. Acceleration, containment, and emission of very low energy solar flare particles

    NASA Technical Reports Server (NTRS)

    Lin, R. P.; Mcguire, R. E.; Anderson, K. A.

    1974-01-01

    We present the first observations of protons down to 44 keV and electrons down to less than about 2 keV emitted in an impulsive solar particle event. The observations are from the Apollo 15 Subsatellite during a flare event which began on September 1, 1971. We obtain a lower limit estimate of the energy contained in protons above about 0.05 MeV in the flare. The effects of adiabatic deceleration in the interplanetary medium and dE/dx energy loss in the corona are discussed. We conclude that energetic protons may constitute a major energy release in large solar flares.

  7. How can we interpret and understand pulsations in solar flare emission? A Bayesian model comparison approach.

    NASA Astrophysics Data System (ADS)

    Inglis, Andrew; Ireland, Jack; Dominique, Marie

    2015-04-01

    Recent work has shown that power-law-like Fourier power spectra are an intrinsic property of solar and stellar flare signals, similarly to other astrophysical objects such as gamma-ray bursts and magnetars. It is therefore critical to account for this in order to understand the nature and significance of short-timescale fluctuations in flares.We present the results of a Bayesian model comparison method for investigating flare time series, fully considering these Fourier power-law properties. Using data from the PROBA2/Large Yield Radiometer, Fermi/Gamma-ray Burst Monitor, Nobeyama Radioheliograph, and Yohkoh/HXT instruments, we study a selection of flares from the literature identified as 'quasi-periodic puslation (QPP)' events. While emphasising that the observed fluctuations are real and of solar origin, we find that, for all but one event tested, an explicit oscillation is not required to explain the observations. Instead, the observed flare signals are adequately described as a manifestation of a power law in the Fourier power spectrum. This evaluation of the QPP phenomenon is markedly different from much of the prior literature.We conclude that the prevalence of oscillatory signatures in solar and stellar flares may be less than previously believed. Furthermore, studying the slope of the observed Fourier power spectrum as a function of energy may provide us with a diagnostic window into the fundamental nature of solar flares.

  8. A technique for short-term warning of solar energetic particle events based on flare location, flare size, and evidence of particle escape

    Microsoft Academic Search

    M. Laurenza; E. W. Cliver; J. Hewitt; M. Storini; A. G. Ling; C. C. Balch; M. L. Kaiser

    2009-01-01

    We have developed a technique to provide short-term warnings of solar energetic proton (SEP) events that meet or exceed the Space Weather Prediction Center threshold of J (>10 MeV) = 10 pr cm?2 s?1 sr?1. The method is based on flare location, flare size, and evidence of particle acceleration\\/escape as parameterized by flare longitude, time-integrated soft X-ray intensity, and time-integrated

  9. Wavelength dependence of solar flare irradiance enhancement and its influence on the thermosphere-ionosphere system

    NASA Astrophysics Data System (ADS)

    Huang, Y.; Richmond, A. D.; Deng, Y.; Qian, L.; Solomon, S. C.; Chamberlin, P. C.

    2012-12-01

    The wavelength dependence of irradiance enhancement during solar flare is one of the important factors in determining how the Thermosphere-Ionosphere (T-I) system responds to flares. To investigate the wavelength dependence of irradiance, the Flare Irradiance Spectral Model (FISM) was run for 34 X-class flares. The results show that the percentage increases of solar irradiance at flare peak have a clear wavelength dependence. In the wavelength range between 0 - 195 nm, it can vary from 1% to 10000%. The solar irradiance enhancement is largest (~1000%) in the XUV range (0 - 25 nm), and is about 100% in the EUV range (25 - 120 nm). The influence of different wavebands on the T-I system during the October 28th, 2003 flare (X17.2-class) has also been examined using the latest version of the National Center for Atmospheric Research (NCAR) Thermosphere-Ionosphere-Electrodynamics General Circulation Model (TIE-GCM). While the enhancement of the globally integrated solar energy deposition is largest in the 0 - 14 nm waveband, the impact of solar irradiance enhancement on the thermosphere at 400km is largest for the 25 - 105 nm waveband. The effect of the enhancement of the 122 - 195 nm waveband is small in magnitude, but it decays slowly.

  10. Implications of X-Ray Observations for Electron Acceleration and Propagation in Solar Flares

    NASA Technical Reports Server (NTRS)

    Holman, G. D.; Aschwanden, M. J.; Aurass, H.; Battaglia, M.; Grigis, P. C.; Kontar, E. P.; Liu, W.; Saint-Hilaire, P.; Zharkova, V. V.

    2011-01-01

    High-energy X-rays and gamma-rays from solar flares were discovered just over fifty years ago. Since that time, the standard for the interpretation of spatially integrated flare X-ray spectra at energies above several tens of keV has been the collisional thick-target model. After the launch of the Reuven Ramaty High Energy Solar Spectroscopic Imager (RHESSI) in early 2002, X-ray spectra and images have been of sufficient quality to allow a greater focus on the energetic electrons responsible for the X-ray emission, including their origin and their interactions with the flare plasma and magnetic field. The result has been new insights into the flaring process, as well as more quantitative models for both electron acceleration and propagation, and for the flare environment with which the electrons interact. In this article we review our current understanding of electron acceleration, energy loss, and propagation in flares. Implications of these new results for the collisional thick-target model, for general flare models, and for future flare studies are discussed.

  11. Solar X-ray Flare Hazards on the Surface of Mars

    E-print Network

    David S. Smith; John M. Scalo

    2006-10-03

    Putative organisms on the Martian surface would be exposed to potentially high doses of ionizing radiation during strong solar X-ray flares. We extrapolate the observed flare frequency-energy release scaling relation to releases much larger than seen so far for the sun, an assumption supported by observations of flares on other solar- and subsolar-mass main sequence stars. We calculate the surficial reprocessed X-ray spectra using a Monte Carlo code we have developed. Biological doses from indirect genome damage are calculated for each parameterized flare spectrum by integration over the X-ray opacity of water. We estimate the mean waiting time for solar flares producing a given biological dose of ionizing radiation on Mars and compare with lethal dose data for a wide range of terrestrial organisms. These timescales range from decades for significant human health risk to 0.5 Myr for D. radiodurans lethality. Such doses require total flare energies of 10^33--10^38 erg, the lower range of which has been observed for other stars. Flares are intermittent bursts, so acute lethality will only occur on the sunward hemisphere during a sufficiently energetic flare, unlike low-dose-rate, extended damage by cosmic rays. We estimate the soil and CO_2 ice columns required to provide 1/e shielding as 4--9 g cm^-2, depending on flare mean energy and atmospheric column density. Topographic altitude variations give a factor of two variation in dose for a given flare. Life in ice layers that may exist ~ 100 g cm^-2 below the surface would be well protected.

  12. Solar flare accelerated isotopes of hydrogen and helium. [observed by IMP-4 and IMP-5

    NASA Technical Reports Server (NTRS)

    Anglin, J. D.; Dietrich, W. F.; Simpson, J. A.

    1973-01-01

    Measurements of solar flare hydrogen, deuterium, tritium, helium-3, and helium-4 in the energy range approximately 10 to 50 MeV per nucleon obtained with instrumentation on the IMP-4 and IMP-5 satellites are reported and studies based on these results which place several constraints on theories of solar flare particle acceleration are discussed. A brief review of previous work and the difficulties in studying the rare isotopes of hydrogen and helium is also included. Particular emphasis is placed on the fact that the information to be obtained from the solar flare products of high energy interactions is not available through either solar wind observations where both the acceleration mechanism and the coronal source of the nuclear species are different, or optical measurements of solar active regions.

  13. Dynamics of Electric Currents, Magnetic Field Topology and Helioseismic Response of a Solar Flare

    E-print Network

    Sharykin, I N

    2015-01-01

    The solar flare on July 30, 2011 was of a modest X-ray class (M9.3), but it made a strong photospheric impact and produced a "sunquake," observed with the Helioseismic and Magnetic Imager (HMI) on NASA's Solar Dynamics Observatory (SDO). In addition to the helioseismic waves (also observed with the SDO/AIA instrument), the flare caused a large expanding area of white-light emission and was accompanied by substantial restructuring of magnetic fields, leading to the rapid formation of a sunspot structure in the flare region. The flare produced no significant hard X-ray emission and no coronal mass ejection. This indicates that the flare energy release was mostly confined to the lower atmosphere. The absence of significant coronal mass ejection rules out magnetic rope eruption as a mechanism of helioseismic waves. We discuss the connectivity of the flare energy release with the electric currents dynamics and show the potential importance of high-speed plasma flows in the lower solar atmosphere during the flare e...

  14. Strong-Flare Rates of Solar-Like Stars in Kepler Cluster NGC 6811

    NASA Astrophysics Data System (ADS)

    Wright, Paul J.; Saar, S. H.; Meibom, S.; Kashyap, V.; Drake, J. J.

    2014-01-01

    Strong flares on the Sun are accompanied by intense ionizing radiation (X-rays, far UV) and are often associated with coronal mass ejections (CMEs), which can be hazardous to astronauts, and infrastructure such as satellites and electrical systems. The rates of the largest flare events are, however, poorly known. By taking advantage of the exquisite precision of Kepler photometry, we derive white light flare distributions for a sample of near-solar-mass (G1-G5) dwarfs in NGC 6811 (age ~ 1 Gyr). Using a solar-based relationship, we estimate the X-ray emission from these flares in order to compare the results to other solar and stellar X-ray flare data. We also take a first look at some stars of different masses, to study the mass dependence of flaring at fixed age, and explore the implications of our results for the rates of the largest flaring events on the Sun. This work was supported by Kepler grants NNX11AC82G and NNX13AC29G and NASA HGI grant NNX10AF29G.

  15. New observational facts about particle acceleration and transport during solar flares

    NASA Technical Reports Server (NTRS)

    Trottel, G.

    1996-01-01

    Extensive hard X-ray (HXR)/gamma-ray (GR) observations of solar flares, performed during solar cycles 21 and 22 have led to important new discoveries. These data, combined with observations obtained in other parts of the electromagnetic spectrum (soft X-ray, Hard X-ray, optical, and radio) largley contributed to get a better understanding and to develop new ideas on particle acceleration and transport during solar flares. This review presents new observational facts relevant to hard X-ray/gamma-ray producing flares. Among these are the frequent presence of sub-second time structure in the hard X-ray emission, the variability in hard X-ray and radio spatial distributions during a flare and from flare to flare, the evidence for strong gamma-ray line emission from the Corona and the existence of extended phases of the gamma-ray emission lasting for several hours after the flare onset. This ensemble of observations indicates that particle acceleration takes place at different sites in a complex and dynamic magnetic field environment.

  16. Solar flare and IMF sector structure effects in the lower ionosphere

    SciTech Connect

    Lastovicka, J.

    1984-05-01

    About 1% of all sudden ionospheric disturbances (SIDs) observed at the Panska Ves Observatory (Czechoslovakia), were found to be not of solar-XUV origin. Among them, the very rare SWF events (observed at L 2.4) of corpuscular origin are the most interesting. The IMF sector structure effects in the midlatitude lower ionosphere are minor in comparison with effects of solar flares, geomagnetic storms, etc. There are two basic types of effects. The first type is a disturbance, best developed in geomagnetic activity, and observed in the night-time ionosphere. It can be interpreted as a response to sector structure related changes of geomagnetic (magnetospheric) activity. The other type is best developed in the tropospheric vorticity area index and is also observed in the day-time ionosphere in winter. This effect is quietening in the ionosphere as well as troposphere. While the occurrence of the former type is persistent in time, the latter is severely diminished in some periods. All the stratosphere, the 10-mb level temperature and height above Berlin-Tempelhof do not display any observable IMF section structure effect.

  17. Solar flare and IMF sector structure effects in the lower ionosphere

    NASA Astrophysics Data System (ADS)

    Lastovicka, J.

    1984-05-01

    About 1% of all sudden ionospheric disturbances (SIDs) observed at the Panska Ves Observatory (Czechoslovakia), were found to be not of solar-XUV origin. Among them, the very rare SWF events (observed at L = 2.4) of corpuscular origin are the most interesting. The IMF sector structure effects in the midlatitude lower ionosphere are minor in comparison with effects of solar flares, geomagnetic storms, etc. There are two basic types of effects. The first type is a disturbance, best developed in geomagnetic activity, and observed in the night-time ionosphere. It can be interpreted as a response to sector structure related changes of geomagnetic (= magnetospheric) activity. The other type is best developed in the tropospheric vorticity area index and is also observed in the day-time ionosphere in winter. This effect is quietening in the ionosphere as well as troposphere. While the occurrence of the former type is persistent in time, the latter is severely diminished in some periods. All the stratosphere, the 10-mb level temperature and height above Berlin-Tempelhof do not display any observable IMF section structure effect.

  18. Solar Flare and IMF Sector Structure Effects in the Lower Ionosphere

    NASA Technical Reports Server (NTRS)

    Lastovicka, J.

    1984-01-01

    About 1% of all sudden ionospheric disturbances (SIDs) observed at the Panska Ves Observatory (Czechoslovakia), were found to be not of solar-XUV origin. Among them, the very rare SWF events (observed at L = 2.4) of corpuscular origin are the most interesting. The IMF sector structure effects in the midlatitude lower ionosphere are minor in comparison with effects of solar flares, geomagnetic storms, etc. There are two basic types of effects. The first type is a disturbance, best developed in geomagnetic activity, and observed in the night-time ionosphere. It can be interpreted as a response to sector structure related changes of geomagnetic (= magnetospheric) activity. The other type is best developed in the tropospheric vorticity area index and is also observed in the day-time ionosphere in winter. This effect is quietening in the ionosphere as well as troposphere. While the occurrence of the former type is persistent in time, the latter is severely diminished in some periods. All the stratosphere, the 10-mb level temperature and height above Berlin-Tempelhof do not display any observable IMF section structure effect.

  19. Magnetic shielding of interplanetary spacecraft against solar flare radiation

    NASA Astrophysics Data System (ADS)

    Cocks, Franklin H.; Watkins, Seth

    1993-07-01

    The ultimate objective of this work is to design, build, and fly a dual-purpose, piggyback payload whose function is to produce a large volume, low intensity magnetic field and to test the concept of using such a magnetic field (1) to protect spacecraft against solar flare protons, (2) to produce a thrust of sufficient magnitude to stabilize low satellite orbits against orbital decay from atmospheric drag, and (3) to test the magsail concept. These all appear to be capable of being tested using the same deployed high temperature superconducting coil. In certain orbits, high temperature superconducting wire, which has now been developed to the point where silver-sheathed high T sub c wires one mm in diameter are commercially available, can be used to produce the magnetic moments required for shielding without requiring any mechanical cooling system. The potential benefits of this concept apply directly to both earth-orbital and interplanetary missions. The usefulness of a protective shield for manned missions needs scarcely to be emphasized. Similarly, the usefulness of increasing orbit perigee without expenditure of propellant is obvious. This payload would be a first step in assessing the true potential of large volume magnetic fields in the US space program. The objective of this design research is to develop an innovative, prototype deployed high temperature superconducting coil (DHTSC) system.

  20. Bulk Energization of Electrons in Solar Flares by Alfvén Waves

    NASA Astrophysics Data System (ADS)

    Melrose, D. B.; Wheatland, M. S.

    2014-03-01

    Bulk energization of electrons to 10 - 20 keV in solar flares is attributed to dissipation of Alfvén waves that transport energy and potential downward to an acceleration region near the chromosphere. The acceleration involves the parallel electric field that develops in the limit of inertial Alfvén waves (IAWs). A two-potential model for IAWs is used to relate the parallel potential to the cross-field potential transported by the waves. We identify a maximum parallel potential in terms of a maximum current density that corresponds to the threshold for the onset of anomalous resistivity. This maximum is of order 10 kV when the threshold is that for the Buneman instability. We argue that this restricts the cross-field potential in an Alfvén wave to about 10 kV. Effective dissipation requires a large number of up- and down-current paths associated with multiple Alfvén waves. The electron acceleration occurs in localized, transient, anomalously conducting regions (LTACRs) and is associated with the parallel electric field determined by Ohm's law with an anomalous resistivity. We introduce an idealized model in which the LTACRs are (upward-)current sheets, a few skin depths in thickness, separated by much larger regions of weaker return current. We show that this model can account semi-quantitatively for bulk energization.

  1. Ulysses particle observations of the March 1991 solar flare events

    NASA Technical Reports Server (NTRS)

    Sanderson, T. R.; Marsden, R. G.; Heras, A. M.; Wenzel, K.-P.; Anglin, J. D.; Balogh, A.; Forsyth, R.

    1992-01-01

    Observations of energetic ions from the COSPIN instrument on the Ulysses spacecraft at 2.5 AU during the March 1991 series of solar flare events arae presented. The intensity profiles observed during this sequence of events were affected both by the presence of interplanetary shocks and large-scale discontinuities in the magnetic field, the low-energy (about 1 MeV) protons being influenced mainly by the shocks and the discontinuities, and the high-energy (about 100 MeV) protons by the discontinuities. The first shock observed at Ulysses was followed by several discontinuities and a Coronal Mass Ejection (CME) which were probably moving with the shock. Particles following this shock were prevented from propagating freely into the heliosphere by the structure moving with the shock, and were carried along with it. A second shock was followed by a region containing bi-directional particle anisotropies. A subsequent enhancement of low-energy particles suggests the passage of another shock. This was followed by a slow intensity decay which coincided with a second CME and where bi-directional particle anisotropies were again observed.

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

    SciTech Connect

    Bian, Nicolas; Kontar, Eduard P. [School of Physics and Astronomy, University of Glasgow, Glasgow G12 8QQ (United Kingdom); Emslie, A. Gordon, E-mail: n.bian@physics.gla.ac.uk, E-mail: eduard@astro.gla.ac.uk, E-mail: emslieg@wku.edu [Department of Physics and Astronomy, Western Kentucky University, Bowling Green, KY 42101 (United States)

    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.

  3. CORONAL ELECTRON DISTRIBUTION IN SOLAR FLARES: DRIFT-KINETIC MODEL

    SciTech Connect

    Minoshima, Takashi; Kusano, Kanya [Institute for Research on Earth Evolution, Japan Agency for Marine-Earth Science and Technology, 3173-25, Syowa-machi, Kanazawaku, Yokohama 236-0001 (Japan); Masuda, Satoshi; Miyoshi, Yoshizumi, E-mail: minoshim@jamstec.go.jp [Solar-Terrestrial Environment Laboratory, Nagoya University, Furo-cho, Chikusa-ku, Nagoya 464-8601 (Japan)

    2011-05-10

    Using a model of particle acceleration and transport in solar flares, we investigate the height distribution of coronal electrons by focusing on the energy-dependent pitch-angle scattering. When pitch-angle scattering is not included, the peak heights of loop-top electrons are constant, regardless of their energy, owing to the continuous acceleration and compression of the electrons via shrinkage of magnetic loops. On the other hand, under pitch-angle scattering, the electron heights are energy-dependent: intermediate-energy electrons are at a higher altitude, whereas lower and higher energy electrons are at lower altitudes. This implies that the intermediate-energy electrons are inhibited from following the shrinking field lines to lower altitudes because pitch-angle scattering causes efficient precipitation of these electrons into the footpoint and their subsequent loss from the loop. This result is qualitatively consistent with the position of the above-the-loop-top hard X-ray (HXR) source that is located above coronal HXR loops emitted by lower energy electrons and microwaves emitted by higher energy electrons. Quantitative agreement with observations might be achieved by considering primary acceleration before the onset of loop shrinkage and additional pitch-angle scattering via wave-particle interactions.

  4. Relationship between unusual features in umbrae and flares

    NASA Astrophysics Data System (ADS)

    Sainz Dalda, Alberto; Kleint, Lucia

    2014-06-01

    The influence of photospheric and chromospheric dynamics and morphologies on flare activity are still unclear. We present a study of two flaring active regions (ARs) with complementary instruments (DST/IBIS, Hinode/SOT-SP, SDO/HMI and SDO/AIA) to investigate the temporal evolution of the sunspots and their magnetic and thermodynamic properties. In spite of vast differences in flare occurrence and flare magnitudes, both ARs show similar features in the lower solar atmosphere during flares. We investigate common magnetic topologies and dynamics, which may favor flare activity.

  5. A CRITICAL EXAMINATION OF THE FUNDAMENTAL ASSUMPTIONS OF SOLAR FLARE AND CORONAL MASS EJECTION MODELS

    SciTech Connect

    Spicer, D. S. [Department of Physics, Drexel University, 3141 Chestnut Street, Philadelphia, PA 19104 (United States); Bingham, R.; Harrison, R. [Rutherford Appleton Laboratory, Chilton, Oxon OX11 0QX (United Kingdom)

    2013-05-01

    The fundamental assumptions of conventional solar flare and coronal mass ejection (CME) theory are re-examined. In particular, the common theoretical assumption that magnetic energy that drives flares and CMEs can be stored in situ in the corona with sufficient energy density is found wanting. In addition, the observational constraint that flares and CMEs produce non-thermal electrons with fluxes of order 10{sup 34}-10{sup 36} electrons s{sup -1}, with energies of order 10-20 keV, must also be explained. This constraint when imposed on the ''standard model'' for flares and CMEs is found to miss the mark by many orders of magnitude. We suggest, in conclusion, there are really only two possible ways to explain the requirements of observations and theory: flares and CMEs are caused by mass-loaded prominences or driven directly by emerging magnetized flux.

  6. The Impact of Return-Current Losses on the Observed Emissions from Solar Flares

    NASA Technical Reports Server (NTRS)

    Holman, Gordon D.

    2011-01-01

    Electrons accelerated in solar flares are expected to drive a co-spatial return current in the ambient plasma when they escape the acceleration region. This return current maintains plasma neutrality and the stability of the beam of streaming electrons. The electric field that drives this return current also decelerates the energetic electrons in the beam. The corresponding energy loss experienced by the accelerated electrons can affect the observed properties of the X-ray and radio emissions from flares and the evolution of the thermal flare plasma. I will discuss the properties of the flare emissions expected in a classical, steady-state model. As part of this discussion, I will examine Gordon Emslie's 1980 conjecture that return-current losses result in a maximum brightness for the hard X-ray emission from flares.

  7. PLASMA HEATING IN THE VERY EARLY AND DECAY PHASES OF SOLAR FLARES

    SciTech Connect

    Falewicz, R.; Rudawy, P. [Astronomical Institute, University of Wroclaw, 51-622 Wroclaw, ul. Kopernika 11 (Poland); Siarkowski, M., E-mail: falewicz@astro.uni.wroc.pl, E-mail: rudawy@astro.uni.wroc.pl, E-mail: ms@cbk.pan.wroc.pl [Space Research Centre, Polish Academy of Sciences, 51-622 Wroclaw, ul. Kopernika 11 (Poland)

    2011-05-20

    In this paper, we analyze the energy budgets of two single-loop solar flares under the assumption that non-thermal electrons (NTEs) are the only source of plasma heating during all phases of both events. The flares were observed by RHESSI and GOES on 2002 September 20 and 2002 March 17, respectively. For both investigated flares we derived the energy fluxes contained in NTE beams from the RHESSI observational data constrained by observed GOES light curves. We showed that energy delivered by NTEs was fully sufficient to fulfill the energy budgets of the plasma during the pre-heating and impulsive phases of both flares as well as during the decay phase of one of them. We concluded that in the case of the investigated flares there was no need to use any additional ad hoc heating mechanisms other than heating by NTEs.

  8. High-energy Gamma-Ray Emission from Solar Flares: Summary of Fermi Large Area Telescope Detections and Analysis of Two M-class Flares

    NASA Astrophysics Data System (ADS)

    Ackermann, M.; Ajello, M.; Albert, A.; Allafort, A.; Baldini, L.; Barbiellini, G.; Bastieri, D.; Bechtol, K.; Bellazzini, R.; Bissaldi, E.; Bonamente, E.; Bottacini, E.; Bouvier, A.; Brandt, T. J.; Bregeon, J.; Brigida, M.; Bruel, P.; Buehler, R.; Buson, S.; Caliandro, G. A.; Cameron, R. A.; Caraveo, P. A.; Cecchi, C.; Charles, E.; Chekhtman, A.; Chen, Q.; Chiang, J.; Chiaro, G.; Ciprini, S.; Claus, R.; Cohen-Tanugi, J.; Conrad, J.; Cutini, S.; D'Ammando, F.; de Angelis, A.; de Palma, F.; Dermer, C. D.; Desiante, R.; Digel, S. W.; Di Venere, L.; Silva, E. do Couto e.; Drell, P. S.; Drlica-Wagner, A.; Favuzzi, C.; Fegan, S. J.; Focke, W. B.; Franckowiak, A.; Fukazawa, Y.; Funk, S.; Fusco, P.; Gargano, F.; Gasparrini, D.; Germani, S.; Giglietto, N.; Giordano, F.; Giroletti, M.; Glanzman, T.; Godfrey, G.; Grenier, I. A.; Grove, J. E.; Guiriec, S.; Hadasch, D.; Hayashida, M.; Hays, E.; Horan, D.; Hughes, R. E.; Inoue, Y.; Jackson, M. S.; Jogler, T.; Jóhannesson, G.; Johnson, W. N.; Kamae, T.; Kawano, T.; Knödlseder, J.; Kuss, M.; Lande, J.; Larsson, S.; Latronico, L.; Lemoine-Goumard, M.; Longo, F.; Loparco, F.; Lott, B.; Lovellette, M. N.; Lubrano, P.; Mayer, M.; Mazziotta, M. N.; McEnery, J. E.; Michelson, P. F.; Mizuno, T.; Moiseev, A. A.; Monte, C.; Monzani, M. E.; Moretti, E.; Morselli, A.; Moskalenko, I. V.; Murgia, S.; Murphy, R.; Nemmen, R.; Nuss, E.; Ohno, M.; Ohsugi, T.; Okumura, A.; Omodei, N.; Orienti, M.; Orlando, E.; Ormes, J. F.; Paneque, D.; Panetta, J. H.; Perkins, J. S.; Pesce-Rollins, M.; Petrosian, V.; Piron, F.; Pivato, G.; Porter, T. A.; Rainò, S.; Rando, R.; Razzano, M.; Reimer, A.; Reimer, O.; Ritz, S.; Schulz, A.; Sgrò, C.; Siskind, E. J.; Spandre, G.; Spinelli, P.; Takahashi, H.; Takeuchi, Y.; Tanaka, Y.; Thayer, J. G.; Thayer, J. B.; Thompson, D. J.; Tibaldo, L.; Tinivella, M.; Tosti, G.; Troja, E.; Tronconi, V.; Usher, T. L.; Vandenbroucke, J.; Vasileiou, V.; Vianello, G.; Vitale, V.; Werner, M.; Winer, B. L.; Wood, D. L.; Wood, K. S.; Wood, M.; Yang, Z.

    2014-05-01

    We present the detections of 18 solar flares detected in high-energy ?-rays (above 100 MeV) with the Fermi Large Area Telescope (LAT) during its first 4 yr of operation. This work suggests that particle acceleration up to very high energies in solar flares is more common than previously thought, occurring even in modest flares, and for longer durations. Interestingly, all these flares are associated with fairly fast coronal mass ejections (CMEs). We then describe the detailed temporal, spatial, and spectral characteristics of the first two long-lasting events: the 2011 March 7 flare, a moderate (M3.7) impulsive flare followed by slowly varying ?-ray emission over 13 hr, and the 2011 June 7 M2.5 flare, which was followed by ?-ray emission lasting for 2 hr. We compare the Fermi LAT data with X-ray and proton data measurements from GOES and RHESSI. We argue that the ?-rays are more likely produced through pion decay than electron bremsstrahlung, and we find that the energy spectrum of the proton distribution softens during the extended emission of the 2011 March 7 flare. This would disfavor a trapping scenario for particles accelerated during the impulsive phase of the flare and point to a continuous acceleration process at play for the duration of the flares. CME shocks are known for accelerating the solar energetic particles (SEPs) observed in situ on similar timescales, but it might be challenging to explain the production of ?-rays at the surface of the Sun while the CME is halfway to the Earth. A stochastic turbulence acceleration process occurring in the solar corona is another likely scenario. Detailed comparison of characteristics of SEPs and ?-ray-emitting particles for several flares will be helpful to distinguish between these two possibilities.

  9. The Relation between Solar Eruption Topologies and Observed Flare Features I: Flare Ribbons

    E-print Network

    Savcheva, A; McKillop, S; McCauley, P; Hanson, E; Su, Y; Werner, E; DeLuca, E E

    2015-01-01

    In this paper we present a topological magnetic field investigation of seven two-ribbon flares in sigmoidal active regions observed with Hinode, STEREO, and SDO. We first derive the 3D coronal magnetic field structure of all regions using marginally unstable 3D coronal magnetic field models created with the flux rope insertion method. The unstable models have been shown to be a good model of the flaring magnetic field configurations. Regions are selected based on their pre-flare configurations along with the appearance and observational coverage of flare ribbons, and the model is constrained using pre-flare features observed in extreme ultraviolet and X-ray passbands. We perform a topology analysis of the models by computing the squashing factor, Q, in order to determine the locations of prominent quasi-separatrix layers (QSLs). QSLs from these maps are compared to flare ribbons at their full extents. We show that in all cases the straight segments of the two J-shaped ribbons are matched very well by the flux...

  10. Tsallis non-extensive statistics, intermittent turbulence, SOC and chaos in the solar plasma. Part two: Solar Flares dynamics

    E-print Network

    L. P. Karakatsanis; G. P. Pavlos; M. N. Xenakis

    2012-04-03

    In the second part of this study and similarly with part one, the nonlinear analysis of the solar flares index is embedded in the non-extensive statistical theory of Tsallis [1]. The triplet of Tsallis, as well as the correlation dimension and the Lyapunov exponent spectrum were estimated for the SVD components of the solar flares timeseries. Also the multifractal scaling exponent spectrum, the generalized Renyi dimension spectrum and the spectrum of the structure function exponents were estimated experimentally and theoretically by using the entropy principle included in Tsallis non extensive statistical theory, following Arimitsu and Arimitsu [2]. Our analysis showed clearly the following: a) a phase transition process in the solar flare dynamics from high dimensional non Gaussian SOC state to a low dimensional also non Gaussian chaotic state, b) strong intermittent solar corona turbulence and anomalous (multifractal) diffusion solar corona process, which is strengthened as the solar corona dynamics makes phase transition to low dimensional chaos: c) faithful agreement of Tsallis non equilibrium statistical theory with the experimental estimations of i) non-Gaussian probability distribution function, ii) multifractal scaling exponent spectrum and generalized Renyi dimension spectrum, iii) exponent spectrum of the structure functions estimated for the sunspot index and its underlying non equilibrium solar dynamics. e) The solar flare dynamical profile is revealed similar to the dynamical profile of the solar convection zone as far as the phase transition process from SOC to chaos state. However the solar low corona (solar flare) dynamical characteristics can be clearly discriminated from the dynamical characteristics of the solar convection zone.

  11. The thermal phase of a large solar flare. [Skylab observations

    NASA Technical Reports Server (NTRS)

    Withbroe, G. L.

    1978-01-01

    EUV and X-ray observations are used to derive the differential emission measures, temperatures, densities, radiative and conductive cooling rates, and thermal energy content of a class 2B flare that occurred on September 7, 1973. The results of the analysis indicate that (1) most of the flare plasma was at temperatures between 3 and 10 million degrees; (2) the peak temperature decreased with time from about 8 million K to 5 million K over a period of 3.5 hours; (3) the differential emission measure steadily decreased with time at nearly all temperatures; (4) both radiation and conduction were important cooling mechanisms for the plasma at temperatures above 100,000 K; and (5) a substantial amount of energy, of the order of 3 x 10 to the 31st power ergs, was deposited in the flare loops after flare maximum. The empirically determined flare parameters are compared with similar parameters derived from a simple theoretical loop model.

  12. The role of magnetic field shear in solar flares

    NASA Technical Reports Server (NTRS)

    Hagyard, M. J.; Moore, R. L.; Emslie, A. G.

    1984-01-01

    Observational results and their physical implications on magnetic field shear in relation to flares are presented. The observed character of magnetic shear and its involvement in the buildup and release of flare energy are reviewed. It is pointed out that the magnetic field in active regions can become sheared by several processes, including shear flow in the photosphere, flux emergence, magnetic reconnection, and flux submergence. Modeling studies of the buildup of stored magnetic energy by shearing are reported which show ample energy storage for flares. Observational evidence is presented that flares are triggered when the field shear reaches a critical degree, in qualitative agreement with some theoretical analyses of sheared force-free fields. Finally, a scenario is outlined for the class of flares resulting from large-scale magnetic shear; the overall instability driving the energy release results from positive feedback between reconnection and eruption of the sheared field.

  13. Satellite-based analysis of thermosphere response to extreme solar flares

    NASA Astrophysics Data System (ADS)

    Krauss, S.; Pfleger, M.; Lammer, H.

    2014-10-01

    We present a refined algorithm to calculate pseudo solar indices, which enable the reproduction of a solar flare impact on the upper Earth's atmosphere for the empirical thermosphere model Jacchia-Bowman 2008. In a first step we compare the estimates of the new algorithm with those from a previous study by analysing an extreme X17.2 flare in 2003 using TIMED/SEE EUV observations. In a second step we adapt the method to use SOHO/SEM measurements within the algorithm and compare the findings with the previous results. Furthermore, the latter procedure is validated by means of GRACE density measurements during a X2.0 solar flare in November 2004. In each of the cases also a comparison with theoretical thermosphere models is performed, which shows a good agreement and suggests that the algorithm can support theoretical evolution studies in case no in situ density measurements during extreme solar events are available.

  14. Statistical study of free magnetic energy and flare productivity of solar active regions

    SciTech Connect

    Su, J. T.; Jing, J.; Wang, S.; Wang, H. M. [Space Weather Research Laboratory, New Jersey Institute of Technology, University Heights, Newark, NJ 07102-1982 (United States); Wiegelmann, T., E-mail: sjt@bao.ac.cn [Max-Planck-Institut fur Sonnensystemforschung, Max-Planck-Strasse 2, D-37191 Katlenburg-Lindau (Germany)

    2014-06-20

    Photospheric vector magnetograms from the Helioseismic and Magnetic Imager on board the Solar Dynamic Observatory are utilized as the boundary conditions to extrapolate both nonlinear force-free and potential magnetic fields in solar corona. Based on the extrapolations, we are able to determine the free magnetic energy (FME) stored in active regions (ARs). Over 3000 vector magnetograms in 61 ARs were analyzed. We compare FME with the ARs' flare index (FI) and find that there is a weak correlation (<60%) between FME and FI. FME shows slightly improved flare predictability relative to the total unsigned magnetic flux of ARs in the following two aspects: (1) the flare productivity predicted by FME is higher than that predicted by magnetic flux and (2) the correlation between FI and FME is higher than that between FI and magnetic flux. However, this improvement is not significant enough to make a substantial difference in time-accumulated FI, rather than individual flare, predictions.

  15. Electron impact polarization expected in solar EUV lines from flaring chromospheres/transition regions

    NASA Technical Reports Server (NTRS)

    Fineschi, S.; Fontenla, Juan M.; Macneice, P.; Ljepojevic, N. N.

    1991-01-01

    We have evaluated lower bounds on the degree of impact Extreme Ultraviolet/Ultraviolet (EUV/UV) line polarization expected during solar flares. This polarization arises from collisional excitation by energetic electrons with non-Maxwellian velocity distributions. Linear polarization was observed in the S I 1437 A line by the Ultraviolet Spectrometer and Polarimeter/Solar Maximum Mission (UVSP/SMM) during a flare on 15 July 1980. An early interpretation suggested that impact excitation by electrons propagating through the steep temperature gradient of the flaring transition region/high chromosphere produced this polarization. Our calculations show that the observed polarization in this UV line cannot be due to this effect. We find instead that, in some flare models, the energetic electrons can produce an impact polarization of a few percent in EUV neutral helium lines (i.e., lambda lambda 522, 537, and 584 A).

  16. Geometrical properties of avalanches in self-organized critical models of solar flares.

    PubMed

    McIntosh, Scott W; Charbonneau, Paul; Bogdan, Thomas J; Liu, Han-Li; Norman, James P

    2002-04-01

    We investigate the geometrical properties of avalanches in self-organized critical models of solar flares. Traditionally, such models differ from the classical sandpile model in their formulation of stability criteria in terms of the curvature of the nodal field, and belong to a distinct universality class. With a view toward comparing these properties to those inferred from spatially and temporally resolved flare observations, we consider the properties of avalanche peak snapshots, time-integrated avalanches in two and three dimensions, and the two-dimensional projections of the latter. The nature of the relationship between the avalanching volume and its projected area is an issue of particular interest in the solar flare context. Using our simulation results we investigate this relationship, and demonstrate that proper accounting of the fractal nature of avalanches can bring into agreement hitherto discrepant results of observational analyses based on simple, nonfractal geometries for the flaring volume. PMID:12005944

  17. Temporal and spatial relationships between O V and Fe XXI emissions in solar flares

    NASA Technical Reports Server (NTRS)

    Cheng, Chung-Chieh; Pallavicini, Roberto

    1988-01-01

    The temporal-spatial structure of simple solar flares observed with the Ultraviolet Spectrometer and Polarimeter of the Solar Maximum mission satellite has been studied in order to investigate the relationships between the impulsive O V and the gradual Fe XXI emissions. The point-like flares are characterized by the cotemporal evolution of the O V and Fe XXI emissions. The simple loop flares have a much larger spatial extent and show two distinctive phases: an initial impulsive phase with its emission localized in loop footpoints, and a gradual phase with its emission distributed in the loop. The temporal evolution of the Fe XXI and O V emissions in a flare is found to be closely related to its spatial structure.

  18. HARD X-RAY AND MICROWAVE FLUX SPECTRA OF THE 2 NOVEMBER 1991 SOLAR FLARE

    E-print Network

    HARD X-RAY AND MICROWAVE FLUX SPECTRA OF THE 2 NOVEMBER 1991 SOLAR FLARE CHIK-YIN LEE1,2 and HAIMIN WANG1 1Big Bear Solar Observatory, New Jersey Institute of Technology, 40386 North Shore Lane, Big Bear City, CA 92314-9672, U.S.A. 2Department of Physics, Rutgers University, Newark, NJ 07102-1811, U

  19. Ionospheric and magnetospheric effects of solar flares monitored by ground-based riometer and magnetometers

    Microsoft Academic Search

    Tardelli Ronan Coelho Stekel; Nelson Jorge Schuch; Ezequiel Echer; Fernando Guarnieri; Kazuo Makita; Cassio Espindola Antunes; Juliano Moro; Claudio Machado Paulo

    2010-01-01

    The solar flare incidence follows a behavior similar to the solar cycle activity, which results in periodic disturbances on the Earth's ionosphere and magnetosphere. The correlation of this phenomenon can provide important information about the magnetosphere, the Sun\\/Earth interaction, as well as events occurring in the ionosphere which can, for instance, generate disturbances in telecommunications, small satellites or even in

  20. Propagation pattern of interplanetary shock waves associated with solar proton flares

    NASA Technical Reports Server (NTRS)

    Sakurai, K.

    1973-01-01

    The two dimensional pattern of interplanetary shock waves is deduced by taking into account the solar longitude dependence of the time intervals between SSC geomagnetic storms and responsible flares. This pattern near the earth's orbit is not symmetric with respect to the meridian plane which crosses the position of the flare, and the highest speed of this wave propagation is observed in the direction about 30 degrees east of this meridian plane. The magnitude of the Forbush decreases of galactic cosmic rays also varies with the longitude positions of those flares. This is used to estimate the distribution of magnetic fields behind the shock waves.

  1. A study of the evolution of energetic electrons in a solar flare

    SciTech Connect

    Holman, G.D.; Kundu, M.R.; Dennis, B.R.

    1984-01-15

    The impulsive microwave and hard X-ray emissions from the 1980 June 25 (1550 UT) solar flare are studied. Time profiles are obtained for the four major bipolar regions that were found by Kundu, Schmah, and Velusamy to contribute to the 6 cm emission from the flare. The light curves are found to be consistent with the regions flaring in unison (to within the 10 s time resolution of the VLA observations) rather than sequentially or in an uncorrelated manner. There is no indication of any change in the magnetic field structure in the emitting regions to within the 2'' spatial resolution of the observations.

  2. Comparing Solar-Flare Acceleration of > 20 MeV Protons and Electrons Above Various Energies

    NASA Astrophysics Data System (ADS)

    Shih, Albert Y.; Dennis, B. R.; Lin, R. P.

    2010-05-01

    A large fraction (up to tens of percent) of the energy released in solar flares goes into accelerated ions and electrons, and studies indicate that these two populations have comparable energy content. RHESSI observations have shown a striking close linear correlation between the 2.223 MeV neutron-capture gamma-ray line and electron bremsstrahlung emission >300 keV, indicating that the flare acceleration of > 20 MeV protons and >300 keV electrons is roughly proportional over >3 orders of magnitude in fluence. We show that the correlations of neutron-capture line fluence with GOES class or with bremsstrahlung emission at lower energies show deviations from proportionality, primarily for flares with lower fluences. From analyzing thirteen flares, we demonstrate that there appear to be two classes of flares with high-energy acceleration: flares that exhibit only proportional acceleration of ions and electrons down to 50 keV and flares that have an additional soft, low-energy bremsstrahlung component, suggesting two separate populations of accelerated electrons. We use RHESSI spectroscopy and imaging to investigate a number of these flares in detail.

  3. Statistical Analysis of Soft X-Ray Solar Flares During Solar Cycles 21, 22 and 23

    E-print Network

    Joshi, Navin Chandra; Pande, Seema; Pande, Bimal; Pandey, Kavita

    2009-01-01

    This paper presents a statistical analysis of Soft X-ray (SXR) flares during the period January 1976 to December 2007 covering solar cycles (SCs) 21, 22, and 23. We have analysed north-south (N-S) and east-west (E-W) asymmetry of SXR at low (less than equal to 40 degree), high (greater than equal to 50 degree) and total latitudes and center meridian distances (CMDs) respectively. We have also presented the N-S and E-W asymmetry of different intensity classes (B, C, M, and X) during the period of investigation. A slight southern and eastern excess is found after analysis during SC 21, 22, and 23. We found that the annual N-S and E-W hemispheric asymmetry at low latitudes and CMDs is the same as total latitudes and CMDs respectively. E-W asymmetry is different at low and high CMDs. Our statistical result shows that N-S asymmetry is statistically more significant than E-W asymmetry. Total SXR flare activity during SC 23 is high compared to SC 21 and 22. The B class flare activity is higher for SC 23 where as C, ...

  4. A solar flare X-ray polarimeter for the space shuttle

    Microsoft Academic Search

    J. R. Lemen; G. A. Chanan; J. P. Hughes; M. R. Laser; R. Novick; I. T. Rochwarger; M. Sackson; L. J. Tramiel

    1982-01-01

    We have recently built and tested an instrument designed to measure the polarization of the hard (5–30 keV) X-ray emission from solar flares, and thereby to investigate the energy release mechanism and constrain flare models. In particular, these measurements will help to determine whether hard X-ray bursts are produced by nonthermal or by thermal electrons. The polarimeter makes use of

  5. A Solar Flare X-Ray Polarimeter for the Space Shuttle

    Microsoft Academic Search

    J. R. Lemen; G. A. Chanan; J. P. Hughes; M. R. Laser; R. Novick; I. T. Rochwarger; M. Sackson; L. J. Tramiel

    1982-01-01

    We have recently built and tested an instrument designed to measure the polarization of the hard (5 30 keV) X-ray emission from solar flares, and thereby to investigate the energy release mechanism and constrain flare models. In particular, these measurements will help to determine whether hard X-ray bursts are produced by nonthermal or by thermal electrons. The polarimeter makes use

  6. A Model for the Escape of Solar-flare-accelerated Particles

    NASA Astrophysics Data System (ADS)

    Masson, S.; Antiochos, S. K.; DeVore, C. R.

    2013-07-01

    We address the problem of how particles are accelerated by solar flares can escape into the heliosphere on timescales of an hour or less. Impulsive solar energetic particle (SEP) bursts are generally observed in association with so-called eruptive flares consisting of a coronal mass ejection (CME) and a flare. These fast SEPs are believed to be accelerated directly by the flare, rather than by the CME shock. However, the precise mechanism by which the particles are accelerated remains controversial. Regardless of the origin of the acceleration, the particles should remain trapped in the closed magnetic fields of the coronal flare loops and the ejected flux rope, given the magnetic geometry of the standard eruptive-flare model. In this case, the particles would reach the Earth only after a delay of many hours to a few days (coincident with the bulk ejecta arriving at Earth). We propose that the external magnetic reconnection intrinsic to the breakout model for CME initiation can naturally account for the prompt escape of flare-accelerated energetic particles onto open interplanetary magnetic flux tubes. We present detailed 2.5-dimensional magnetohydrodynamic simulations of a breakout CME/flare event with a background isothermal solar wind. Our calculations demonstrate that if the event occurs sufficiently near a coronal-hole boundary, interchange reconnection between open and closed fields can occur. This process allows particles from deep inside the ejected flux rope to access solar wind field lines soon after eruption. We compare these results to standard observations of impulsive SEPs and discuss the implications of the model on further observations and calculations.

  7. Spread-Spectrum VLF Observations at Arrival Heights, Antarctica During Solar X-Ray Flares

    Microsoft Academic Search

    T. Wang; R. C. Moore; A. C. Fraser-Smith

    2010-01-01

    It is well known that subionospherically-propagating very low frequency (VLF) signals are sensitive to the ionospheric effects of solar flares. It has been documented since the 1960's that the typical X-ray flare affects the phase of the VLF signal (known as a sudden phase anomaly, or SPA), but a sudden change in both the amplitude and the phase of the

  8. The origins of space weather: recent advances in understanding solar flares

    NASA Astrophysics Data System (ADS)

    Browning, Philippa

    “Space weather” events affecting the terrestrial magnetosphere have their origins in explosive events in the solar atmosphere, notably solar flares. Solar flares may affect the magnetosphere through EUV/X-ray radiation and energetic charged particles (both ions and electrons) , as well as the production of Coronal Mass Ejections (CMEs). A brief overview of our current theoretical and observational understanding of solar flares will be given, focusing on the generation of radiation, particles and CMEs. Recent new models of the acceleration of charged particles by magnetic reconnection in large-scale current sheets solar flares will be described, showing how populations of both trapped and escaping non-thermal particles are generated - the latter propagating into the heliosphere. Test particle and particle-in-cell modelling allow prediction of the time evolution of energy spectra and pitch angles of energetic particles, and their spatial distributions. Smaller, confined flares may occur due to instabilities in twisted magnetic loops. Recent modelling of the heating and particle acceleration in unstable twisted loops will be described, using a coupled magnetohydrodynamic and test particle approach. The time dependence of the radiation in EUV and soft X-rays, due to plasma heating, as well as the Hard X-rays associated with the non-thermal particles are forward-modelled, allowing comparison with data from SDO and RHESSI, and radio instruments.

  9. Solar X-ray Flare Hazards on the Surface of Mars

    E-print Network

    Smith, D S; Smith, David S.; Scalo, John M.

    2006-01-01

    Putative organisms on the Martian surface would be exposed to potentially high doses of ionizing radiation during strong solar X-ray flares. We extrapolate the observed flare frequency-energy release scaling relation to releases much larger than seen so far for the sun, an assumption supported by observations of flares on other solar- and subsolar-mass main sequence stars. We calculate the surficial reprocessed X-ray spectra using a Monte Carlo code we have developed. Biological doses from indirect genome damage are calculated for each parameterized flare spectrum by integration over the X-ray opacity of water. We estimate the mean waiting time for solar flares producing a given biological dose of ionizing radiation on Mars and compare with lethal dose data for a wide range of terrestrial organisms. These timescales range from decades for significant human health risk to 0.5 Myr for D. radiodurans lethality. Such doses require total flare energies of 10^33--10^38 erg, the lower range of which has been observe...

  10. Investigation of Solar Flares Using Spectrally, Spatially, and Temporally Resolved Observations in Gamma Rays, Hard X Rays, and Microwaves

    NASA Technical Reports Server (NTRS)

    Crannell, Carol Jo; Oegerle, William (Technical Monitor)

    2003-01-01

    The high-energy components of solar flares radiate at a wide range of wavelengths. We are using spatially, spectrally, and temporally resolved hard X-ray, gamma-ray, and microwave observations of solar flares to investigate flare models and to understand the flare acceleration process. The hard X-ray and gamma-ray observations are obtained with the Reuven Ramaty High-Energy Solar Spectroscopic Imager (RHESSI) spacecraft that was launched on February 5, 2002. The microwave observations are obtained with the Owens Valley Radio Observatory (OVRO), which has been dedicated to daily observations of solar flares in microwaves with a five-element interferometer since June 1992. These studies are expected to yield exciting new insights into the fundamental physics of the flare acceleration processes.

  11. Thermal Evolution of Solar Flares During the First Year of SDO as Seen by the EVE Instrument

    NASA Technical Reports Server (NTRS)

    Chamberlin, Phillip C.; Woods, Thomas N.

    2011-01-01

    It is very evident during the first year of the Solar Dynamics Observatory (SDO) that the Sun awoke from its prolonged minimum and is well into solar cycle 24. There has been tens of moderate M-class flares and a large X-class event (as of abstract submission), with more surely to come as the solar cycle activity increases. With SDO's 24/7 observations, every single flare has been observed through their entire evolution, providing new insights in the thermal evolution of every flare. It is evident that this evolution is extremely different for many of the flares, even for flares with similar X-ray magnitude classifications. Presented and discussed will be these different flares with their varying thermal evolution profiles as observed by the Extreme ultraviolet Variability Experiment (EVE) onboard the Solar Dynamics Observatory (SDO).

  12. Radiative hydrodynamic modelling and observations of the X-class solar flare on 2011 March 9

    NASA Astrophysics Data System (ADS)

    Kennedy, Michael B.; Milligan, Ryan O.; Allred, Joel C.; Mathioudakis, Mihalis; Keenan, Francis P.

    2015-06-01

    Aims: We investigated the response of the solar atmosphere to non-thermal electron beam heating using the radiative transfer and hydrodynamics modelling code RADYN. The temporal evolution of the parameters that describe the non-thermal electron energy distribution were derived from hard X-ray observations of a particular flare, and we compared the modelled and observed parameters. Methods: The evolution of the non-thermal electron beam parameters during the X1.5 solar flare on 2011 March 9 were obtained from analysis of RHESSI X-ray spectra. The RADYN flare model was allowed to evolve for 110 s, after which the electron beam heating was ended, and was then allowed to continue evolving for a further 300 s. The modelled flare parameters were compared to the observed parameters determined from extreme-ultraviolet spectroscopy. Results: The model produced a hotter and denser flare loop than that observed and also cooled more rapidly, suggesting that additional energy input in the decay phase of the flare is required. In the explosive evaporation phase a region of high-density cool material propagated upward through the corona. This material underwent a rapid increase in temperature as it was unable to radiate away all of the energy deposited across it by the non-thermal electron beam and via thermal conduction. A narrow and high-density (ne ? 1015 cm-3) region at the base of the flare transition region was the source of optical line emission in the model atmosphere. The collision-stopping depth of electrons was calculated throughout the evolution of the flare, and it was found that the compression of the lower atmosphere may permit electrons to penetrate farther into a flaring atmosphere compared to a quiet Sun atmosphere.

  13. Estimating Flaring Probability from High-Cadence Images of the Solar Chromosphere

    NASA Astrophysics Data System (ADS)

    Norquist, Donald C.; Balasubramaniam, K.

    2011-05-01

    We applied principal component analysis to 8-10 hour sequences of chromospheric H? images of selected solar active regions as observed by the U. S. Air Force Improved Solar Optical Observation Network (ISOON) telescope at Sacramento Peak, NM at one-minute intervals. A covariance matrix of all combinations of image time pairs was computed from the picture element H? intensities from each image sequence, and eigenvalues and eigenvectors were computed. Computation of explained variance from the eigenvalues indicated that 99.9% of the characteristics were represented by the first 50 eigenvectors or so. The leading eigenvectors were matched at each image time with a flare category indicator deduced from coincident active region area-average H? intensity and 1-8 Å GOES X-ray flux measurements at one-minute intervals. Multivariate discriminant analysis (MVDA) was applied to the eigenvector elements and flaring indicators from a training set of image sequences to compute a vector of coefficients whose linear combination with the eigenvector predictors maximizes the distinction among flaring groups. The discriminant function, computed from the dot product of the coefficients with the eigenvectors of an independent ISOON case, is used to compute the probability of each flaring group at each measurement time. Flare category indicators from independent case times are used to assess the flaring probability estimates. Multivariate logistic regression (MVLR) was also applied to the subset of eigenvectors in the training data, and the derived coefficients were also dotted with the independent eigenvalues to generate a separate flaring probability estimate. A total of 47 ISOON image sequences were available for training and flaring probability estimation. Preliminary results showed that the MVLR was competitive with MVDA in skill of diagnosing flaring probability. If this approach shows promise in a diagnostic mode, efforts will be made to extend it to short-term (1-3 hour) prognostic mode.

  14. Energy release topology in a multiple-loop solar flare

    NASA Technical Reports Server (NTRS)

    Cheng, C.-C.; Pallavicini, R.; Acton, L. W.; Tandberg-Hanssen, E.

    1985-01-01

    The temporal and spatial structures of the UV and X-ray emissions and the magnetic field configuration in the November 12, 1980 flare observed from SMM have been studied. The UV observations were done in the O V and Fe XXI lines with a spatial resolution of 10 arcsec. The observations show that the impulsive UV bursts, and also the hard X-ray bursts by their temporal correlation with the impulsive O V emission, occurred in small localized kernels. By comparing the O V, Fe XXI, and X-ray raster images of the flare with the magnetogram, these emission kernels were identified as footpoints of interacting magnetic flux loops. The temporal evolution of the O V/Fe XXI emission shows that there was considerable preheating in the flare plasma some 8-9 minutes prior to the onset of the main hard X-ray bursts. The results are interpreted as indicating that the primary flare energy release occurred in a highly sheared multiloop structure, which lies along a magnetic neutral line. By either beam particle propagation or convective motion, flare energy is transported via a common footpoint to another loop which brightened later. The preheating of the flare plasma is shown to create a more favorable environment for energetic particle acceleration which resulted in the main impulsive hard X-ray bursts.

  15. Characteristics of the Photospheric Magnetic Field Associated with Solar Flare Initiation

    NASA Astrophysics Data System (ADS)

    Yang, Ya-Hui; Chen, P. F.; Hsieh, Min-Shiu; Wu, S. T.; He, Han; Tsai, Tsung-Che

    2014-05-01

    The physical environment governing the solar flare initiation is not fully understood, although there are significant efforts to address the relationship between magnetic non-potential parameters and early flare signatures. In this study, we attempt to characterize the flare initiation based on the processed Helioseismic and Magnetic Imager vector magnetograms, Atmospheric Imaging Assembly 1600 Å, and RHESSI hard X-ray observations. Three flare events, the M6.6 flare on 2011 February 13, the X2.2 flare on 2011 February 15, and the X2.1 flare on 2011 September 6, in two active regions AR 11158 and AR 11283 are investigated. We analyze the source field strength in the photosphere, which is defined as the magnitude of the observed magnetic field deviation from the potential field. It is found that one of the strong source field regions above the magnetic polarity inversion line well connects the initial bright kernels of two conjugate ribbons. The results imply that the distribution of the photospheric source field strength can be used to locate the initiation site of flaring loops regardless of the configuration of pre-flare magnetic fields or the evolution of active regions. Moreover, the field configuration in the strong source field regions tends to become more inclined after flares, which is consistent with the coronal implosion scenario. We also employ a fast method to derive the total current density from the photospheric vector magnetogram in the framework of force-free field. This method can provide fast estimation of photospheric current density within a reasonable accuracy without appealing for the more accurate calculation from a model extrapolation.

  16. Table-top solar flares produced with laser driven magnetic reconnections

    NASA Astrophysics Data System (ADS)

    Zhong, J. Y.; Li, Y. T.; Wang, X. G.; Wang, J. Q.; Dong, Q. L.; Liu, X.; Lin, X. X.; Yuan, D. W.; Du, F.; Wang, S. J.; Zhang, L.; An, L.; Xiao, C. J.; Wei, H. G.; Zhang, K.; Wang, F. L.; Jiang, S. E.; Ding, Y. K.; Cao, Z. R.; Yuan, Z.; Zhang, H. Y.; Yang, Z. W.; Zhu, J. Q.; He, X. T.; Cai, H. B.; Zhao, G.; Zhang, J.

    2013-11-01

    The American Nuclear Society (ANS) has presented the prestigious Edward Teller award to Dr. Bruce A. Remington during the 2011 IFSA conference due to his "pioneering scientific work in the fields of inertial confinement fusion (ICF), and especially developing an international effort in high energy density laboratory astrophysics" [1,2]. This is a great acknowledgement to the subject of high energy density laboratory astrophysics. In this context, we report here one experiment conducted to model solar flares in the laboratory with intense lasers [3]. The mega-gauss -scale magnetic fields produced by laser produced plasmas can be used to make magnetic reconnection topology. We have produced one table-top solar flare in our laboratory experiment with the same geometric setup as associated with solar flares.

  17. The interpretation of hard X-ray polarization measurements in solar flares

    NASA Technical Reports Server (NTRS)

    Leach, J.; Petrosian, V.; Emslie, A. G.

    1985-01-01

    Observations of polarization of moderately hard X-rays in solar flares are reviewed and compared with the predictions of recent detailed modeling of hard X-ray bremsstrahlung production by non-thermal electrons. The recent advances in the complexity of the modeling lead to substantially lower predicted polarizations than in earlier models and more fully highlight how various parameters play a role in determining the polarization of the radiation field. The new predicted polarizations are comparable to those predicted by thermal modeling of solar flare hard X-ray production, and both are in agreement with the observations. In the light of these results, new polarization observations with current generation instruments are proposed which could be used to discriminate between non-thermal and thermal models of hard X-ray production in solar flares.

  18. The interpretation of hard X-ray polarization measurements in solar flares

    NASA Technical Reports Server (NTRS)

    Leach, J.; Emslie, A. G.; Petrosian, V.

    1983-01-01

    Observations of polarization of moderately hard X-rays in solar flares are reviewed and compared with the predictions of recent detailed modeling of hard X-ray bremsstrahlung production by non-thermal electrons. The recent advances in the complexity of the modeling lead to substantially lower predicted polarizations than in earlier models and more fully highlight how various parameters play a role in determining the polarization of the radiation field. The new predicted polarizations are comparable to those predicted by thermal modeling of solar flare hard X-ray production, and both are in agreement with the observations. In the light of these results, new polarization observations with current generation instruments are proposed which could be used to discriminate between non-thermal and thermal models of hard X-ray production in solar flares.

  19. Comparison between IBIS Observations and Radiative Transfer Hydrodynamic Simulations of a Solar Flare

    NASA Astrophysics Data System (ADS)

    Rubio da Costa, F.; Kleint, L.; Liu, W.; Sainz Dalda, A.; Petrosian, V.

    2014-12-01

    High-resolution spectroscopic observations of solar flares are rare but can provide valuable diagnostics. On September 24, 2011 an M3.0 class flare was observed by the Interferometric BIdimensional Spectropolarimeter (IBIS) in chromospheric H? and CaII 8542 Å lines and by the Reuven Ramaty High Energy Solar Spectroscopic Imager (RHESSI) in X-rays. We fitted the RHESSI spectra at different times with a power-law plus isothermal component. We then used the fitted real-time spectral parameters of nonthermal electrons as the input to the RADYN radiative hydrodynamic code (Carlsson et al, 1992, 1996; Allred et al, 2005) to simulate the low-chromospheric response to collisional heating by energetic electrons. We synthesized both the H? and CaII 8542 Å lines from the simulation results and compare them with the IBIS observations. We discuss the constraints from this comparison on particle acceleration mechanisms in solar flares.

  20. Can microbunch instability on solar flare accelerated electron beams account for bright broadband coherent synchrotron microwaves?

    SciTech Connect

    Kaufmann, Pierre; Raulin, Jean-Pierre [Centro de Radio-Astronomia e Astrofisica-CRAAM-Escola de Engenharia, Universidade Presbiteriana Mackenzie, Sao Paulo, SP (Brazil)

    2006-07-15

    The physical processes producing bright broadband coherent synchrotron radiation (CSR) bursts in laboratory accelerators are proposed to happen also in solar flares, bringing a plausible explanation to serious interpretation constraints raised by the discovery of a solar flare sub-mm-wave spectral emission component peaking in the terahertz (THz) range simultaneous to the well-known microwaves component. The THz component is due to incoherent synchrotron radiation (ISR) produced by a beam of ultrarelativistic electrons. Beam density perturbations, on a scale of the order of or smaller than the emitting wavelength, sets a microbunch instability producing the intense CSR at lower frequencies. Hard x-ray/{gamma}-ray emissions may include a significant synchrotron emission component from the same ISR spectrum, bringing a new possibility to explain the so called ''solar flare electron number paradox'.

  1. Hybrid Kinetic and Radiative Hydrodynamic Simulations of Solar Flares and Comparison With Multiwavelength Observations

    NASA Astrophysics Data System (ADS)

    Rubio Da Costa, Fatima; Petrosian, Vahe; Liu, Wei; Carlsson, Mats; Kleint, Lucia

    2014-06-01

    We present a unified simulation which combines two physical processes: how the particles are accelerated and the energy is transported along a coronal loop, and how the atmosphere responds. The “flare” code from Stanford University (Petrosian et al, 2001) models the stochastic acceleration and transport of particles and radiation of solar flares. It includes pitch angle diffusion and energy loss, and computes collisional heating to the background plasma and bremsstrahlung emission along the loop. The radiative hydrodynamic RADYN Code (Carlsson et al, 1992, 1996; Allred et al, 2005) computes the energy transport by the injected non-thermal electrons at the top of a 1D coronal loop. Recently, we have combined the two codes by updating the non-thermal heating in the RADYN code from the "flare" code, allowing us to develop a self-consistent simulation. In addition, we can now model more realistically the multi-wavelength emission of solar flares and compare it with observations, e.g., at optical wavelengths from IBIS at the Dunn Solar Telescope and in X-rays from RHESSI. The high resolution UV observations from the recently launched IRIS imaging spectrograph will be particularly useful in this regard. These will allow us to compare numerically modeled and observed emissions of solar flares in several lines using more robust simulations than possible before.

  2. Ionospheric and magnetospheric effects of solar flares monitored by ground-based riometer and magnetometers

    NASA Astrophysics Data System (ADS)

    Ronan Coelho Stekel, Tardelli; Schuch, Nelson Jorge; Echer, Ezequiel; Guarnieri, Fernando; Makita, Kazuo; Espindola Antunes, Cassio; Moro, Juliano; Machado Paulo, Claudio

    The solar flare incidence follows a behavior similar to the solar cycle activity, which results in periodic disturbances on the Earth's ionosphere and magnetosphere. The correlation of this phenomenon can provide important information about the magnetosphere, the Sun/Earth interaction, as well as events occurring in the ionosphere which can, for instance, generate disturbances in telecommunications, small satellites or even in the space weather. Riometer and magnetometers data analysis can provide useful way for measuring and understanding the effects of solar flare radiation in the ionosphere and magnetosphere. The Solar Flare effect (SFE) is associated with the sudden change of ionospheric currents caused by the extra ionization produced by soft X-ray (0.1 to 9.0 nm) and EUV (9.0 to 100.0 nm) radiation from the solar flare. The objective of this work is to present the correlation of the ionospheric and magnetospheric (H, D, Z) sudden disturbances due to high-intensity solar flares (M and X class), that can emit up to 1032 ergs of energy. For this purpose, analysis were performed for the riometer and magnetometers dedicated to study the Solar-Earth interactions at the Southern Space Observatory (SSO/CRS/INPE -MCT), (29.4° S, 53.8° W, 480m a.s.l), São Martinho da a Serra, RS, Brazil. To identify and investigate the sudden radiation increase caused by the solar flare, the X-ray data (0.1 to 0.8 nm) from GOES Satellites and the EUV data (26.0 to 34.0 nm and 0.1 to 50.0 nm) from the Solar EUV Monitor (SEM) on the SOHO spacecraft are correlated. With the analysis of these ground-based instruments and spacecrafts data, the correlation of the solar activity and the magnetospheric and ionospheric disturbances were performed, as for the Sudden Ionospheric Disturbance (SID) and Magnetic Crochet about 60% D-component variation during a large solar flare was observed.

  3. Solar Demon: near real-time Flare, Dimming and EUV wave monitoring

    NASA Astrophysics Data System (ADS)

    Kraaikamp, Emil; Verbeeck, Cis

    Dimmings and EUV waves have been observed routinely in EUV images since 1996. They are closely associated with coronal mass ejections (CMEs), and therefore provide useful information for early space weather alerts. On the one hand, automatic detection and characterization of dimmings and EUV waves can be used to gain better understanding of the underlying physical mechanisms. On the other hand, every dimming and EUV wave provides extra information on the associated front side CME, and can improve estimates of the geo-effectiveness and arrival time of the CME. Solar Demon has been designed to detect and characterize dimmings, EUV waves, as well as solar flares in near real-time on Solar Dynamics Observatory/Atmospheric Imaging Assembly (SDO/AIA) data. The detection modules are running continuously at the Royal Observatory of Belgium on both quick-look data, as well as synoptic science data. The output of Solar Demon can be accessed in near real-time on the Solar Demon website, and includes images, movies, light curves, and the numerical evolution of several parameters. Solar Demon is the result of collaboration between the FP7 projects AFFECTS and COMESEP. Flare detections of Solar Demon are integrated into the COMESEP alert system. Here we present the Solar Demon detection algorithms and their output. We will show several interesting flare, dimming and EUV wave events, and present general statistics of the detections made so far during solar cycle 24.

  4. High-energy particle production in solar flares (SEP, gamma-ray and neutron emissions). [solar energetic particles

    NASA Technical Reports Server (NTRS)

    Chupp, E. L.

    1987-01-01

    Electrons and ions, over a wide range of energies, are produced in association with solar flares. Solar energetic particles (SEPs), observed in space and near earth, consist of electrons and ions that range in energy from 10 keV to about 100 MeV and from 1 MeV to 20 GeV, respectively. SEPs are directly recorded by charged particle detectors, while X-ray, gamma-ray, and neutron detectors indicate the properties of the accelerated particles (electrons and ions) which have interacted in the solar atmosphere. A major problem of solar physics is to understand the relationship between these two groups of charged particles; in particular whether they are accelerated by the same mechanism. The paper reviews the physics of gamma-rays and neutron production in the solar atmosphere and the method by which properties of the primary charged particles produced in the solar flare can be deduced. Recent observations of energetic photons and neutrons in space and at the earth are used to present a current picture of the properties of impulsively flare accelerated electrons and ions. Some important properties discussed are time scale of production, composition, energy spectra, accelerator geometry. Particular attention is given to energetic particle production in the large flare on June 3, 1982.

  5. Magnetic and Velocity Field Changes Related to the Solar Flares of 28 and 29 October 2003

    NASA Astrophysics Data System (ADS)

    Maurya, R. A.; Ambastha, A.

    Magnetic and velocity field measurements of solar active regions suffer from ambiguities caused by the change in spectral line profiles that occur during the impulsive phase of a major flare. This leads to difficulties in correct interpretation of any flare-related changes. Using magnetic and Doppler movies taken with GONG and MDI, we have detected transient, "moving" features around the peak phases of the X17.2/4B flare observed on 28 October 2003 and the X10/2B flare observed on 29 October 2003 in super-active region NOAA 10486. These features were located near the compact acoustic sources reported earlier by Donea and Lindsey (2005) and the seismic sources reported by Zharkova and Zharkov (2007).We find a moving feature, spatially and temporally associated with the flare ribbons, that separates away at speeds ranging from 30 to 50 km s-1 as observed in photospheric white light and in temperature-minimum (1600 Å), chromospheric (H?), and transition-region (284Å ) intensities.We suggest that such moving features arise from the line-profile changes attributed to downward electron jets associated with the flare, and do not reflect real changes in the photospheric magnetic and velocity fields. However, abrupt and persistent changes in the pre- and post-flare phases were also found, which do not seem to be affected by line-profile changes. The detailed results have been appeared in Maurya and Ambastha (2009).

  6. Azimuthal propagation of low-energy solar flare protons - Interpretation of observations

    NASA Technical Reports Server (NTRS)

    Mckibben, R. B.

    1973-01-01

    The major conclusions reached by McKibben (1972) in a report of fluxes and spectra of solar flare protons in the approximate energy range from 10 to 30 MeV are reviewed. The observations had been made with cosmic ray telescopes on board the deep space probes Pioneer 6 and Pioneer 7 and the earth satellite Imp 4 during nine solar flare proton events occurring in the period from December 1967 to August 1968. The interpretation of the observations is discussed, giving attention to the stochastic field model of Jokipii and Parker (1969). Aspects of interplanetary diffusion are considered together with observations of corotating events.

  7. Deuterium and tritium from solar flares at approximately 10 MeV per nucleon

    NASA Technical Reports Server (NTRS)

    Anglin, J. D.; Dietrich, W. F.; Simpson, J. A.

    1973-01-01

    It is indicated that the observations with the high-resolution solid-state charged-particle telescopes of the IMP-5 and IMP-6 earth satellites have resolved all the hydrogen and helium isotopes of solar-flare origin in groups of solar flares during the period from September, 1969, through November, 1972. The values obtained for the average isotope ratios are given and are compared with previous values. It is concluded that the observed high yields of H(2), H(3) and He(3) can be explained only by high-energy nuclear interactions and that an acceleration process must have taken place in the chromosphere at that time.

  8. Implications of X-ray Observations for Electron Acceleration and Propagation in Solar Flares

    E-print Network

    Holman, Gordon D; Aurass, Henry; Battaglia, Marina; Grigis, Paolo C; Kontar, Eduard P; Liu, Wei; Saint-Hilaire, Pascal; Zharkova, Valentina V

    2011-01-01

    High-energy X-rays and gamma-rays from solar flares were discovered just over fifty years ago. Since that time, the standard for the interpretation of spatially integrated flare X-ray spectra at energies above several tens of keV has been the collisional thick-target model. After the launch of the Reuven Ramaty High Energy Solar Spectroscopic Imager (RHESSI) in early 2002, X-ray spectra and images have been of sufficient quality to allow a greater focus on the energetic electrons responsible for the X-ray emission, including their origin and their interactions with the flare plasma and magnetic field. The result has been new insights into the flaring process, as well as more quantitative models for both electron acceleration and propagation, and for the flare environment with which the electrons interact. In this article we review our current understanding of electron acceleration, energy loss, and propagation in flares. Implications of these new results for the collisional thick-target model, for general fla...

  9. The solar minimum X2.6/1B flare and CME of 9 July 1996. Pt. 1; Solar data

    NASA Technical Reports Server (NTRS)

    Andrews, M. D.; Dryer, M.; Aurass, H.; DeForest, C.; Kiplinger, A. L.; Meisner, R.; Paswaters, S. E.; Smith, Z.; Tappin, S. J.; Thompson, B. J.; Watari, S.-I.; Lamy, P.; Mann, G.; Schwenn, R.; Michels, D. J.; Brueckner, G. E.; Howard, R. A.; Koomen, M.

    1997-01-01

    The solar observations from GOES-8, the Solar and Heliospheric Observatory (SOHO), and the Yohkoh satellite concerning the events of the X-class flare are discussed. The Michelson Doppler imager (MDI) magnetometer shows a new region of magnetic activity in AR 7978. The rapid development and evolution of this region is shown by the MDI and the extreme-ultraviolet Doppler telescope (EDT) data. The coronal mass ejections (CMEs) observed using coronagraphs are presented. The possible association between the CME and the X-flare is considered.

  10. Solar magnetic polarity dependency of geomagnetic storm seasonal occurrence

    NASA Astrophysics Data System (ADS)

    Oh, S. Y.; Yi, Y.

    2011-06-01

    For nearly a century it has been known that the tendency for geomagnetic activity is, on average, higher at the equinoxes than at the solstices. Previous studies on semiannual geomagnetic activity were performed mainly for geomagnetic indices such as am, aa, U, and AL. Thus, we need to understand the seasonal variation of geomagnetic activity defined by the Dst index over the long term. It is also necessary to test the solar magnetic polarity dependence of geomagnetic activity. This paper is a statistical analysis of the geomagnetic storms defined by the Dst index. Our storm data consists of two sets of storm data for 5 years at each solar minimum during the four solar cycles (19-22) from 1962 through 1998 for two of each solar magnetic polarity. The storms are divided into two groups defined by Dst index (Dst(min) < -50 nT, ?Dst? > 70 nT; Dst(min) < -50 nT, ?Dst? > 90 nT). Monthly occurrences of these storms are compared. Storms of ?Dst? > 90 nT and of ?Dst? > 70 nT occurred 153 and 238 times, respectively, during the testing periods. Storms occurred more frequently during the spring and fall seasons for all solar cycle minima, regardless of solar magnetic polarity.

  11. Prompt particle acceleration around moving X-point magnetic field during impulsive phase of solar flares

    NASA Technical Reports Server (NTRS)

    Sakai, Jun-Ichi

    1992-01-01

    We present a model for high-energy solar flares to explain prompt proton and electron acceleration, which occurs around moving X-point magnetic field during the implosion phase of the current sheet. We derive the electromagnetic fields during the strong implosion phase of the current sheets, which is driven by the converging flow derived from the magnetohydrodynamic equations. It is shown that both protons and electrons can be promptly (within 1 second) accelerated to approximately 70 MeV and approximately 200 MeV, respectively. This acceleration mechanism can be applicable for the impulsive phase of the gradual gamma ray and proton flares (gradual GR/P flare), which have been called two-ribbon flares.

  12. Observations of Unresolved Photospheric Magnetic Fields in Solar Flares Using Fe i and Cr i Lines

    NASA Astrophysics Data System (ADS)

    Gordovskyy, M.; Lozitsky, V. G.

    2014-10-01

    The structure of the photospheric magnetic field during solar flares is examined using echelle spectropolarimetric observations. The study is based on several Fe i and Cr i lines observed at locations corresponding to brightest H? emission during thermal phase of flares. The analysis is performed by comparing magnetic-field values deduced from lines with different magnetic sensitivities, as well as by examining the fine structure of I± V Stokes-profiles' splitting. It is shown that the field has at least two components, with stronger unresolved flux tubes embedded in weaker ambient field. Based on a two-component magnetic-field model, we compare observed and synthetic line profiles and show that the field strength in small-scale flux tubes is about 2 - 3 kG. Furthermore, we find that the small-scale flux tubes are associated with flare emission, which may have implications for flare phenomenology.

  13. Simultaneous 2 and 6 centimeter wavelength observations of a solar flare using the VLA

    SciTech Connect

    Kundu, M.R.; Velusamy, T.; White, S.M.

    1987-10-01

    VLA observations of a solar active region and a flare are discussed. The event was observed at wavelengths of 2 and 6 cm simultaneously. Radio maps prior to the flare delineate the most important magnetic structures in the region. Interaction between these structures apparently led to preheating of plasma above the active region some 30 minutes prior to the flare. The 2 and 6 cm flare positions were coincident, and the time profiles of the burst at the two wavelengths were almost identical, implying that the same population of electrons was responsible for emission at the two wavelengths. Emission was probably nonthermal gyrosynchrotron radiation, and the physical conditions in the burst source are derived using this assumption. 15 references.

  14. Simultaneous 2 and 6 centimeter wavelength observations of a solar flare using the VLA

    NASA Technical Reports Server (NTRS)

    Kundu, M. R.; Velusamy, T.; White, S. M.

    1987-01-01

    VLA observations of a solar active region and a flare are discussed. The event was observed at wavelengths of 2 and 6 cm simultaneously. Radio maps prior to the flare delineate the most important magnetic structures in the region. Interaction between these structures apparently led to preheating of plasma above the active region some 30 minutes prior to the flare. The 2 and 6 cm flare positions were coincident, and the time profiles of the burst at the two wavelengths were almost identical, implying that the same population of electrons was responsible for emission at the two wavelengths. Emission was probably nonthermal gyrosynchrotron radiation, and the physical conditions in the burst source are derived using this assumption.

  15. Comparative study of measured amplitude and phase perturbations on VLF and LF radio signals induced by solar flares

    E-print Network

    Sulic, D M

    2014-01-01

    Very Low Frequency, VLF and Low Frequency, LF signal perturbations were examined to study ionospheric disturbances induced by solar X-ray flares. The aim was to understand processes in propagation VLF/LF radio signals over short paths, and to estimate specific characteristics of each short path. The receiver at Belgrade station continuously monitor the amplitude and phase of coherent and subionospherically propagating LF signal operated in Sicily, NSC at 45.90, kHz and VLF signal operated in Isola di Tavolara ICV at 20.27 kHz, with great circle distances of 953 km and 976 km, respectively. Geographical locations of transmitters and receiver site result that these short paths have many similarity. The main difference is in transmitter frequencies. In period from 2008 to February 2014 were selected around 200 events for further examination. In all selected examples amplitude and phase on VLF and LF signals were perturbed by occurrence of solar X-ray flares. This six years period covers minimum and maximum of so...

  16. Implosion of Coronal Loops during the Impulsive Phase of a Solar Flare

    NASA Astrophysics Data System (ADS)

    Simões, P. J. A.; Fletcher, L.; Hudson, H. S.; Russell, A. J. B.

    2013-11-01

    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.

  17. Energetic Electrons in Solar Flares - As Viewed in X-Rays

    NASA Technical Reports Server (NTRS)

    Holman, Gordon D.

    2004-01-01

    Hard X-ray observations provide the most direct diagnostic we have of the suprathermal electrons and the hottest thermal plasma present in solar flares. The Ramaty High Energy Solar Spectroscopic Imager (RHESSI) is obtaining the most comprehensive observations of individual solar flares ever available in hard X-rays. For the first time, high-resolution spectra are available for a large number of flares that accurately display the spectral shape and its evolution and, in many cases, allow us to identify the transition from the bremsstrahlung X-rays produced by suprathermal electrons to the bremsstrahlung at lower energies emitted by thermal plasma. Also, for the first time, images can be produced in arbitrary energy bands above 3 keV, and spectra of distinct imaged components can be obtained. I will review what we have learned from RHESSI observations about flare suprathermal electron distributions and their evolution Next, I will present computations of the energy deposited by these suprathermal electrons in individual flares and compare this with the energy contained in the hot thermal plasma. I will point out unsolved problems in deducing both suprathermal electron distributions and the energy content of the thermal plasma, and discuss possible solutions. Finally, I will present evidence that electron acceleration is associated with magnetic reconnection in the corona.

  18. Properties of Chromospheric Evaporation and Plasma Dynamics of a Solar Flare from Iris

    NASA Astrophysics Data System (ADS)

    Sadykov, Viacheslav M.; Vargas Dominguez, Santiago; Kosovichev, Alexander G.; Sharykin, Ivan N.; Struminsky, Alexei B.; Zimovets, Ivan

    2015-06-01

    The dynamics of hot chromospheric plasma of solar flares is a key to understanding the mechanisms of flare energy release and particle acceleration. A moderate M1.0 class flare of 2014 June 12, (SOL2014-06-12T21:12) was simultaneously observed by NASA's Interface Region Imaging Spectrograph (IRIS) and other spacecraft, and also by the New Solar Telescope at the BBSO. This paper presents the first part of our investigation focused on analysis of the IRIS data. Our analysis of the IRIS data in different spectral lines reveals a strong redshifted jet-like flow with a speed of ?100 km s?1 of the chromospheric material before the flare. Strong nonthermal emission of the C ii k 1334.5 Å line, formed in the chromosphere–corona transition region, is observed at the beginning of the impulsive phase in several small (with a size of ?1?) points. It is also found that the C ii k line is redshifted across the flaring region before, during, and after the impulsive phase. A peak of integrated emission of the hot (1.1 · 107 K) plasma in the Fe xxi 1354.1 Å line is detected approximately five minutes after the integrated emission peak of the lower temperature C ii k. A strong blueshift of the Fe xxi line across the flaring region corresponds to evaporation flows of the hot chromospheric plasma with a speed of 50 km s?1. Additional analysis of the RHESSI data supports the idea that the upper chromospheric dynamics observed by IRIS has features of “gentle” evaporation driven by heating of the solar chromosphere by accelerated electrons and by a heat flux from the flare energy release site.

  19. TIME-DEPENDENT DENSITY DIAGNOSTICS OF SOLAR FLARE PLASMAS USING SDO/EVE

    SciTech Connect

    Milligan, Ryan O.; Kennedy, Michael B.; Mathioudakis, Mihalis; Keenan, Francis P. [Astrophysics Research Centre, School of Mathematics and Physics, Queen's University Belfast, University Road, Belfast BT7 1NN (United Kingdom)

    2012-08-10

    Temporally resolved electron density measurements of solar flare plasmas are presented using data from the EUV Variability Experiment (EVE) on board the Solar Dynamics Observatory. The EVE spectral range contains emission lines formed between 10{sup 4} and 10{sup 7} K, including transitions from highly ionized iron ({approx}>10 MK). Using three density-sensitive Fe XXI ratios, peak electron densities of 10{sup 11.2}-10{sup 12.1} cm{sup -3} were found during four X-class flares. While previous measurements of densities at such high temperatures were made at only one point during a flaring event, EVE now allows the temporal evolution of these high-temperature densities to be determined at 10 s cadence. A comparison with GOES data revealed that the peak of the density time profiles for each line ratio correlated well with that of the emission measure time profile for each of the events studied.

  20. Spectral Atlas of X-ray Lines Emitted During Solar Flares Based on CHIANTI

    NASA Technical Reports Server (NTRS)

    Landi, E.; Phillips, K. J. H.

    2005-01-01

    A spectral atlas of X-ray lines in the wavelength range 7.47-18.97 Angstroms is presented, based on high-resolution spectra obtained during two M-class solar flares (on 1980 August 25 and 1985 July 2) with the Flat Crystal Spectrometer on board the Solar Maximum Mission. The physical properties of the flaring plasmas are derived as a function of time using strong, isolated lines. From these properties predicted spectra using the CHIANTI database have been obtained which were then compared with wavelengths and fluxes of lines in the observed spectra to establish line identifications. identifications for nearly all the observed lines in the resulting atlas are given, with some significant corrections to previous analysis of these flare spectra.

  1. Observations with the SMM gamma-ray spectrometer - The impulsive solar flares of 1980 March 29

    NASA Technical Reports Server (NTRS)

    Ryan, J. M.; Forrest, D. J.; Chupp, E. L.; Cherry, M. L.; Reppin, C.; Rieger, E.; Pinkau, K.; Kanbach, G.; Share, G. H.; Kinzer, R. L.

    1981-01-01

    Gamma-ray continuum emission from 0.3 to 1 MeV was observed with the gamma-ray spectrometer on the Solar Maximum Mission satellite during two impulsive solar flares on 1980 March 29, from active region 2363 at 0918 UT and from active region 2357 at 0955 UT. Evidence is presented for a hardening of the spectrum during the impulsive phase of the flares. The photon intensity greater than 100 keV appears to decay at a slower rate than that at lower energies. Time-integrated photon spectra for both flares are incompatible with a single-temperature thermal-bremsstrahlung model. Upper limits for prompt and delayed gamma-ray lines are presented.

  2. The Contribution of Microbunching Instability to Solar Flare Emission in the GHz to THz Range of Frequencies

    NASA Astrophysics Data System (ADS)

    Klopf, J. Michael; Kaufmann, Pierre; Raulin, Jean-Pierre; Szpigel, Sérgio

    2014-08-01

    Recent solar flare observations in the sub-terahertz range have provided evidence of a new spectral component with fluxes increasing for larger frequencies, separated from the well-known microwave emission that maximizes in the gigahertz range. Suggested interpretations explain the terahertz spectral component but do not account for the simultaneous microwave component. We present a mechanism for producing the observed "double spectra." Based on coherent enhancement of synchrotron emission at long wavelengths in laboratory accelerators, we consider how similar processes may occur within a solar flare. The instability known as microbunching arises from perturbations that produce electron beam density modulations, giving rise to broadband coherent synchrotron emission at wavelengths comparable to the characteristic size of the microbunch structure. The spectral intensity of this coherent synchrotron radiation (CSR) can far exceed that of the incoherent synchrotron radiation (ISR), which peaks at a higher frequency, thus producing a double-peaked spectrum. Successful CSR simulations are shown to fit actual burst spectral observations, using typical flaring physical parameters and power-law energy distributions for the accelerated electrons. The simulations consider an energy threshold below which microbunching is not possible because of Coulomb repulsion. Only a small fraction of the radiating charges accelerated to energies above the threshold is required to produce the microwave component observed for several events. The ISR/CSR mechanism can occur together with other emission processes producing the microwave component. It may bring an important contribution to microwaves, at least for certain events where physical conditions for the occurrence of the ISR/CSR microbunching mechanism are possible.

  3. Ionization effects due to solar flare on terrestrial ionosphere

    NASA Technical Reports Server (NTRS)

    Wu, S. T.; Tan, A.

    1976-01-01

    Sudden frequency deviation ionospheric disturbances related to the flares of May 18 and 19, 1973 were observed from the NASA/MSFC high frequency Doppler sounder array system in Huntsville, Alabama. The results are compared with those observed at Table Mountain near Boulder, Colorado and at the University of Hawaii.

  4. Plasma heating in solar flares and their soft and hard X-ray emissions

    SciTech Connect

    Falewicz, R., E-mail: falewicz@astro.uni.wroc.pl [Astronomical Institute, University of Wroc?aw, 51-622 Wroc?aw, ul. Kopernika 11 (Poland)

    2014-07-01

    In this paper, the energy budgets of two single-loop-like flares observed in X-ray are analyzed under the assumption that nonthermal electrons (NTEs) are the only source of plasma heating during all phases of both events. The flares were observed by RHESSI and GOES on 2002 February 20 and June 2, respectively. Using a one-dimensional (1D) hydrodynamic code for both flares, the energy deposited in the chromosphere was derived applying RHESSI observational data. The use of the Fokker-Planck formalism permits the calculation of distributions of the NTEs in flaring loops and thus spatial distributions of the X-ray nonthermal emissions and integral fluxes for the selected energy ranges that were compared with the observed ones. Additionally, a comparative analysis of the spatial distributions of the signals in the RHESSI images was conducted for the footpoints and for all the flare loops in selected energy ranges with these quantities' fluxes obtained from the models. The best compatibility of the model and observations was obtained for the 2002 June 2 event in the 0.5-4 Å GOES range and total fluxes in the 6-12 keV, 12-25 keV, 20-25 keV, and 50-100 keV energy bands. Results of photometry of the individual flaring structures in a high energy range show that the best compliance occurred for the 2002 June 2 flare, where the synthesized emissions were at least 30% higher than the observed emissions. For the 2002 February 20 flare, synthesized emission is about four times lower than the observed one. However, in the low energy range the best conformity was obtained for the 2002 February 20 flare, where emission from the model is about 11% lower than the observed one. The larger inconsistency occurs for the 2002 June 2 solar flare, where synthesized emission is about 12 times greater or even more than the observed emission. Some part of these differences may be caused by inevitable flaws of the applied methodology, like by an assumption that the model of the flare is symmetric and there are no differences in the emissions originating from the feet of the flares loop and by relative simplicity of the applied numerical 1D code and procedures. No doubt a significant refinement of the applied numerical models and more sophisticated implementation of the various physical mechanisms involved are required to achieve a better agreement. Despite these problems, a collation of modeled results with observations shows that soft and hard X-ray emissions observed for analyzed single-loop-like events may be fully explained by electron-beam-driven evaporation only.

  5. Plasma Heating in Solar Flares and their Soft and Hard X-Ray Emissions

    NASA Astrophysics Data System (ADS)

    Falewicz, R.

    2014-07-01

    In this paper, the energy budgets of two single-loop-like flares observed in X-ray are analyzed under the assumption that nonthermal electrons (NTEs) are the only source of plasma heating during all phases of both events. The flares were observed by RHESSI and GOES on 2002 February 20 and June 2, respectively. Using a one-dimensional (1D) hydrodynamic code for both flares, the energy deposited in the chromosphere was derived applying RHESSI observational data. The use of the Fokker-Planck formalism permits the calculation of distributions of the NTEs in flaring loops and thus spatial distributions of the X-ray nonthermal emissions and integral fluxes for the selected energy ranges that were compared with the observed ones. Additionally, a comparative analysis of the spatial distributions of the signals in the RHESSI images was conducted for the footpoints and for all the flare loops in selected energy ranges with these quantities' fluxes obtained from the models. The best compatibility of the model and observations was obtained for the 2002 June 2 event in the 0.5-4 Å GOES range and total fluxes in the 6-12 keV, 12-25 keV, 20-25 keV, and 50-100 keV energy bands. Results of photometry of the individual flaring structures in a high energy range show that the best compliance occurred for the 2002 June 2 flare, where the synthesized emissions were at least 30% higher than the observed emissions. For the 2002 February 20 flare, synthesized emission is about four times lower than the observed one. However, in the low energy range the best conformity was obtained for the 2002 February 20 flare, where emission from the model is about 11% lower than the observed one. The larger inconsistency occurs for the 2002 June 2 solar flare, where synthesized emission is about 12 times greater or even more than the observed emission. Some part of these differences may be caused by inevitable flaws of the applied methodology, like by an assumption that the model of the flare is symmetric and there are no differences in the emissions originating from the feet of the flares loop and by relative simplicity of the applied numerical 1D code and procedures. No doubt a significant refinement of the applied numerical models and more sophisticated implementation of the various physical mechanisms involved are required to achieve a better agreement. Despite these problems, a collation of modeled results with observations shows that soft and hard X-ray emissions observed for analyzed single-loop-like events may be fully explained by electron-beam-driven evaporation only.

  6. Automated Solar Activity Prediction: A hybrid computer platform using machine learning and solar imaging for automated prediction of solar flares

    NASA Astrophysics Data System (ADS)

    Colak, T.; Qahwaji, R.

    2009-06-01

    The importance of real-time processing of solar data especially for space weather applications is increasing continuously. In this paper, we present an automated hybrid computer platform for the short-term prediction of significant solar flares using SOHO/Michelson Doppler Imager images. This platform is called the Automated Solar Activity Prediction tool (ASAP). This system integrates image processing and machine learning to deliver these predictions. A machine learning-based system is designed to analyze years of sunspot and flare data to create associations that can be represented using computer-based learning rules. An imaging-based real-time system that provides automated detection, grouping, and then classification of recent sunspots based on the McIntosh classification is also created and integrated within this system. The properties of the sunspot regions are extracted automatically by the imaging system and processed using the machine learning rules to generate the real-time predictions. Several performance measurement criteria are used and the results are provided in this paper. Also, quadratic score is used to compare the prediction results of ASAP with NOAA Space Weather Prediction Center (SWPC) between 1999 and 2002, and it is shown that ASAP generates more accurate predictions compared to SWPC.

  7. Solar flares observed simultaneously with SphinX, GOES and RHESSI

    NASA Astrophysics Data System (ADS)

    Mrozek, Tomasz; Gburek, Szymon; Siarkowski, Marek; Sylwester, Barbara; Sylwester, Janusz; K?pa, Anna; Gryciuk, Magdalena

    2013-07-01

    In February 2009, during recent deepest solar minimum, Polish Solar Photometer in X-rays (SphinX) begun observations of the Sun in the energy range of 1.2-15 keV. SphinX was almost 100 times more sensitive than GOES X-ray Sensors. The silicon PIN diode detectors used in the experiment were carefully calibrated on the ground using Synchrotron Radiation Source BESSY II. The SphinX energy range overlaps with the Ramaty High Energy Solar Spectroscopic Imager (RHESSI) energy range. The instrument provided us with observations of hundreds of very small flares and X-ray brightenings. We have chosen a group of solar flares observed simultaneously with GOES, SphinX and RHESSI and performed spectroscopic analysis of observations wherever possible. The analysis of thermal part of the spectra showed that SphinX is a very sensitive complementary observatory for RHESSI and GOES.

  8. High-energy solar flare observations at the Y2K maximum

    NASA Astrophysics Data System (ADS)

    Emslie, A. Gordon

    2000-04-01

    Solar flares afford an opportunity to observe processes associated with the acceleration and propagation of high-energy particles at a level of detail not accessible in any other astrophysical source. I will review some key results from previous high-energy solar flare observations, including those from the Compton Gamma-Ray Observatory, and the problems that they pose for our understanding of energy release and particle acceleration processes in the astrophysical environment. I will then discuss a program of high-energy observations to be carried out during the upcoming 2000-2001 solar maximum that is aimed at addressing and resolving these issues. A key element in this observational program is the High Energy Solar Spectroscopic Imager (HESSI) spacecraft, which will provide imaging spectroscopic observations with spatial, temporal, and energy resolutions commensurate with the physical processes believed to be operating, and will in addition provide the first true gamma-ray spectroscopy of an astrophysical source. .

  9. Radioactivity Induced in Apollo 11 Lunar Surface Material by Solar Flare Protons

    Microsoft Academic Search

    H. R. Heydegger; Anthony Turkevich

    1970-01-01

    Comparison of values of the specific radioactivities reported for lunar surface material from the Apollo 11 mission with analogous data for stone meteorites suggests that energetic particles from the solar flare of 12 April 1969 may have produced most of the cobalt-56 observed.

  10. Observational aspects of the study of plasma turbulence in solar flares

    NASA Astrophysics Data System (ADS)

    Firstova, N. M.

    1990-07-01

    Using two techniques (the polarization method and the Baranger-Mozer method) a study has been made of plasma turbulence in solar emission features. The study suggests the conclusion that the 0.02-0.03 plasma turbulence level (E = 1-2 kV/cm seems to be the highest achieved in flares.

  11. Do Sandpile Models Explain Observations of Complex Dynamics in Solar Flares and Polar Aurora?

    Microsoft Academic Search

    K. Rypdal; K. Boris; M. Rypdal

    2007-01-01

    Many complex systems in nature are at present not accessible for description based on first physical principles, partly due to the complexity of the dynamics and partly due to lack of necessary observational data. For some phenomena, like solar flare activity or optical aurora, detailed spatiotemporal information is only available as fluctuations of a scalar 2D radiation field emitted from

  12. Modeling the equatorial and low latitude ionosphere response to an intense X-class solar flare

    NASA Astrophysics Data System (ADS)

    Nogueira, P.; Souza, J.; Abdu, M. A.; Paes, R. D. R.; Santos, J. S.; Marques, M. S.; Bailey, G. J.; Cueva, R.; De Nardin, C. M.; Takahashi, H.; Batista, I. S.; Chen, S. S.

    2014-12-01

    We have investigated the ionospheric response close to the subsolar point due to the strong solar flare (X2.8) that occurred on May 13th, 2013. The present work discusses the sudden disturbances observed in the major ionospheric parameters, such as in the E-region current system as obtained from ground based magnetometer observations near magnetic equator, and at low and mid-latitude stations. A strong intensification of the eastward Equatorial Electrojet (EEJ) was observed over Peru. The dayside ionosphere showed an abrupt increase of the Total Electron Content (TEC) over South America, especially over the low latitude region, due to the flare enhanced ionizing solar radiation flux. In this work we have used the Sheffield University Plasmasphere-Ionosphere Model (SUPIM) to model the TEC enhancement as arising from the flare enhanced solar EUV flux and soft X-rays. The simulation results are compared with the observational data to validate our results. The overall results can significantly advance our knowledge of ionospheric photochemistry and dynamics to improve our predictive capability on the low latitude ionospheric response to solar flares.

  13. Quasi-periodic hard X-ray oscillations before impulsive phase of solar flares

    NASA Astrophysics Data System (ADS)

    Tomczak, Michal; Jakimiec, Jerzy

    Using observations from the YOHKOH Hard X-ray Telescope and Compton Gamma Ray Ob-servatory spectrometer we have found small-amplitude quasi-periodic hard X-ray oscillations before impulsive phase (OBIP) of solar flares. We have been investigating properties of the oscillations and transition from the OBIP to impulsive phase. Our results support the model of electron acceleration in oscillating magnetic traps (Jakimiec and Tomczak 2010, Solar Physics, 261, 233).

  14. The HUS solar flare and cosmic gamma-ray burst detector aboard the ULYSSES spacecraft

    Microsoft Academic Search

    Michel Boer; Michael Sommer; K. Hurley

    1990-01-01

    The HUS-Ulysses team has prepared an instrument aboard the ULYSSES spacecraft consisting of 2 CsI detectors and 2 Si surface barrier detectors for measuring X-rays in the range 5–200 keV up to 8 ms resolution. The prime objectives are the study of solar flares and of cosmic gamma-ray bursts. The ULYSSES mission will leave the ecliptic during the next solar

  15. Combined STEREO\\/RHESSI Study of Coronal Mass Ejection Acceleration and Particle Acceleration in Solar Flares

    Microsoft Academic Search

    M. Temmer; A. M. Veronig; E. P. Kontar; S. Krucker; B. Vrsnak

    2010-01-01

    Using the potential of two unprecedented missions, Solar Terrestrial Relations Observatory (STEREO) and Reuven Ramaty High-Energy Solar Spectroscopic Imager (RHESSI), we study three well-observed fast coronal mass ejections (CMEs) that occurred close to the limb together with their associated high-energy flare emissions in terms of RHESSI hard X-ray (HXR) spectra and flux evolution. From STEREO\\/EUVI and STEREO\\/COR1 data, the full

  16. Semiempirical photospheric models of a solar flare on May 28, 2012

    NASA Astrophysics Data System (ADS)

    Andriets, E. S.; Kondrashova, N. N.

    2015-02-01

    The variation of the photosphere physical state during the decay phase of SF/B6.8-class solar flare on May 28, 2012 in active region NOAA 11490 is studied. We used the data of the spectropolarimetric observations with the French-Italian solar telescope THEMIS (Tenerife, Spain). Semi-empirical model atmospheres are derived from the inversion with SIR (Stokes Inversion based on Response functions) code. The inversion was based on Stokes profiles of six photospheric lines. Each model atmosphere has a two-component structure: a magnetic flux tube and non-magnetic surroundings. The Harvard Smithsonian Reference Atmosphere (HSRA) has been adopted for the surroundings. The macroturbulent velocity and the filling factor were assumed to be constant with the depth. The optical depth dependences of the temperature, magnetic field strength, and line-of-sight velocity are obtained from inversion. According to the received model atmospheres, the parameters of the magnetic field and the thermodynamical parameters changed during the decay phase of the flare. The model atmospheres showed that the photosphere remained in a disturbed state during observations after the maximum of the flare. There are temporal changes in the temperature and the magnetic field strength optical depth dependences. The temperature enhancement in the upper photospheric layers is found in the flaring atmospheres relative to the quiet-Sun model. The downflows are found in the low and upper photosphere at the decay phase of the flare.

  17. CONTINUUM CONTRIBUTIONS TO THE SDO/AIA PASSBANDS DURING SOLAR FLARES

    SciTech Connect

    Milligan, Ryan O.; McElroy, Sarah A., E-mail: r.milligan@qub.ac.uk [Astrophysics Research Centre, School of Mathematics and Physics, Queen's University Belfast, University Road, Belfast BT7 1NN (United Kingdom)

    2013-11-01

    Data from the Multiple EUV Grating Spectrograph component of the Extreme-ultraviolet Variability Experiment (EVE) on board the Solar Dynamics Observatory (SDO) were used to quantify the contribution of continuum emission to each of the extreme ultraviolet (EUV) channels of the Atmospheric Imaging Assembly (AIA), also on SDO, during an X-class solar flare that occurred on 2011 February 15. Both the pre-flare-subtracted EVE spectra and fits to the associated free-free continuum were convolved with the AIA response functions of the seven EUV passbands at 10 s cadence throughout the course of the flare. It was found that 10%-25% of the total emission in the 94 Å, 131 Å, 193 Å, and 335 Å passbands throughout the main phase of the flare was due to free-free emission. Reliable measurements could not be made for the 171 Å channel, while the continuum contribution to the 304 Å channel was negligible due to the presence of the strong He II emission line. Up to 50% of the emission in the 211 Å channel was found to be due to free-free emission around the peak of the flare, while an additional 20% was due to the recombination continuum of He II. The analysis was extended to a number of M- and X-class flares and it was found that the level of free-free emission contributing to both the 171 Å and 211 Å passbands increased with increasing GOES class. These results suggest that the amount of continuum emission that contributes to AIA observations during flares is more significant than stated in previous studies which used synthetic, rather than observed, spectra. These findings highlight the importance of spectroscopic observations carried out in conjunction with those from imaging instruments so that the data are interpreted correctly.

  18. Radioactive Positron Emitter Production by Energetic Alpha Particles in Solar Flares

    NASA Astrophysics Data System (ADS)

    Murphy, R. J.; Kozlovsky, B.; Share, G. H.

    2014-12-01

    Measurements of the 0.511 MeV positron-annihilation line from solar flares are used to explore the flare process in general and ion acceleration in particular. In flares, positrons are produced primarily by the decay of radioactive positron-emitting isotopes resulting from nuclear interactions of flare-accelerated ions with ambient solar material. Kozlovsky et al. provided ion-energy-dependent production cross sections for 67 positron emitters evaluated from their threshold energies (some <1 MeV nucleon-1) to a GeV nucleon-1, incorporating them into a computer code for calculating positron-emitter production. Adequate cross-section measurements were available for proton reactions, but not for ?-particle reactions where only crude estimates were possible. Here we re-evaluate the ?-particle cross sections using new measurements and nuclear reaction codes. In typical large gamma-ray line flares, proton reactions dominate positron production, but ?-particle reactions will dominate for steeper accelerated-ion spectra because of their relatively low threshold energies. With the accelerated-3He reactions added previously, the code is now reliable for calculating positron production from any distribution of accelerated-ion energies, not just those of typical flares. We have made the code available in the online version of the Journal. We investigate which reactions, projectiles, and ion energies contribute to positron production. We calculate ratios of the annihilation-line fluence to fluences of other gamma-ray lines. Such ratios can be used in interpreting flare data and in determining which nuclear radiation is most sensitive for revealing acceleration of low-energy ions at the Sun.

  19. RADIOACTIVE POSITRON EMITTER PRODUCTION BY ENERGETIC ALPHA PARTICLES IN SOLAR FLARES

    SciTech Connect

    Murphy, R. J. [Code 7650, Naval Research Laboratory, Washington, DC 20375 (United States); Kozlovsky, B. [Tel Aviv University, Tel Aviv (Israel); Share, G. H., E-mail: murphy@ssd5.nrl.navy.mil, E-mail: benz@wise.tau.ac.il, E-mail: share@astro.umd.edu [University of Maryland, College Park, MD 20742 (United States)

    2015-01-01

    Measurements of the 0.511 MeV positron-annihilation line from solar flares are used to explore the flare process in general and ion acceleration in particular. In flares, positrons are produced primarily by the decay of radioactive positron-emitting isotopes resulting from nuclear interactions of flare-accelerated ions with ambient solar material. Kozlovsky et al. provided ion-energy-dependent production cross sections for 67 positron emitters evaluated from their threshold energies (some <1 MeV nucleon{sup –1}) to a GeV nucleon{sup –1}, incorporating them into a computer code for calculating positron-emitter production. Adequate cross-section measurements were available for proton reactions, but not for ?-particle reactions where only crude estimates were possible. Here we re-evaluate the ?-particle cross sections using new measurements and nuclear reaction codes. In typical large gamma-ray line flares, proton reactions dominate positron production, but ?-particle reactions will dominate for steeper accelerated-ion spectra because of their relatively low threshold energies. With the accelerated-{sup 3}He reactions added previously, the code is now reliable for calculating positron production from any distribution of accelerated-ion energies, not just those of typical flares. We have made the code available in the online version of the Journal. We investigate which reactions, projectiles, and ion energies contribute to positron production. We calculate ratios of the annihilation-line fluence to fluences of other gamma-ray lines. Such ratios can be used in interpreting flare data and in determining which nuclear radiation is most sensitive for revealing acceleration of low-energy ions at the Sun.

  20. Directivity of HXR Solar Flare Emission Obtained from Stereoscopic Observations by Mars Odyssey (HEND), RHESSI and CORONAS-F (SONG)

    Microsoft Academic Search

    Moisey Livshits; Dmitry Golovin; Igor Mitrofanov; S. Alexander Kozyrev; Maxim Litvak; Vladislav Tretyakov; Anton Sanin; William V. Boynton; Larisa Kashapova; Irina Myagkova; Andrey Bogomolov

    2010-01-01

    Two powerful X-Ray flares were observed on 2005, July 14 by three spacecrafts whose heliolon-gitudes were spaced on 39 degrees. The flares were observed, as projected on the solar disc by Mars Odyssey (HEND) and seeing almost directly on the limb by RHESSI and CORONAS-F. The most intensive hard X-ray and gamma-ray flare (up to 2 MeV) was observed by

  1. Element Abundances in High-temperature Solar Flare Plasma from MESSENGER SAX Observations

    NASA Astrophysics Data System (ADS)

    Dennis, Brian R.; Nittler, Larry R.; Phillips, Kenneth; Schwartz, Richard A.; Starr, Richard D.; Tolbert, Anne K

    2014-06-01

    X-ray spectral measurements of many solar flares made with the MESSENGER SAX instrument have been used to determine the abundances of Fe, Ca, Ar, S, and Si in the high temperature plasma. All available data from launch in 2004 to date have been used to obtain spectral fits to the SAX data from 2.3 to 8.5 keV for all time intervals with a detectable count rate in the Fe-line complex at 6.7 keV. For each time interval, OSPEX, our object-oriented IDL spectral analysis program, is used to obtain values of the emission measure, temperature distribution, and abundances that give the best-fit of the corresponding CHIANTI photon spectrum folded through the instrument response matrix to the measured count-rate spectrum above background. Distributions will be presented of element abundances for each flare and for all flares detected during each year of observations. Variations in measured abundances will be discussed as to whether they reflect real differences from the mean or differences due to statistical and/or systematic uncertainties. Comparisons will be made with abundance measurements made from other data sets, in particular by Phillips and Dennis (2012) using data from the Ramaty High Energy Solar Spectroscopic Imager (RHESSI), and by Warren et al. (2013) using data from the EUV Variability Experiment (EVE) on the Solar Dynamics Observatory (SDO).Phillips, K. J. H. and Dennis, B. R., “The Solar Flare Iron Abundance,” 2012, ApJ, 748, 52.Warren, H. “Measurements of Absolute Abundances in Solar Flares,” 2013, arXiv, 2013arXiv1310.4765W

  2. Ionospheric response to the X-class solar flare on 7 September 2005

    NASA Astrophysics Data System (ADS)

    Xiong, Bo; Wan, Weixing

    2013-04-01

    We investigate the extreme ionospheric effect during the intense solar flare (X17.0/3B) that occurred on 7 September 2005. A strong E region electron density enhancement is observed by the incoherent scatter radars at Millstone Hill, Sondrestrom, and Tromsø, as well as by the radio occultation experiment on board the CHAMP satellite. The observations from both Millstone Hill and Sondrestrom stations show the average percentage enhancements of electron density during 17:40-18:10 UT are more than 200% near the E region peak height but only about 10% near the F region peak height; as a result, it leads to an unusual phenomenon where the E region electron density exceeds the F region electron density. We ascribe the unusual response to weak enhancement in EUV flux and strong enhancement in X-ray flux during this flare. To further understand this unusual feature, we analyze in detail the E region response by comparing the electron production rates derived from the measurements with those fitted by the Chapman production function. Our results demonstrate that the Chapman production theory fits the observations better in the flare time than in the nonflare time, which is attributed to the obvious difference in the solar radiation spectra at flare and nonflare times. Owing to the strong enhancement in X-ray flux during this flare, the E region electron production is more dominated by the X-ray, and the Chapman ionization theory is more applicable in the flare time than in the nonflare time. In addition, we propose a method to estimate the effective solar radiation flux from the ionospheric observations of electron density profiles. The radiation flux derived with our method agrees well with the X-ray flux at 0.1-0.8 nm observed by GOES 12.

  3. Ionospheric response to the X-class solar flare on 7 September 2005

    NASA Astrophysics Data System (ADS)

    Xiong, Bo; Wan, Weixing; Liu, Libo; Withers, Paul; Zhao, Biqiang; Ning, Baiqi; Wei, Yong; Le, Huijun; Ren, Zhipeng; Chen, Yiding; He, Maosheng; Liu, Jing

    2011-11-01

    We investigate the extreme ionospheric effect during the intense solar flare (X17.0/3B) that occurred on 7 September 2005. A strong E region electron density enhancement is observed by the incoherent scatter radars at Millstone Hill, Sondrestrom, and Tromsø, as well as by the radio occultation experiment on board the CHAMP satellite. The observations from both Millstone Hill and Sondrestrom stations show the average percentage enhancements of electron density during 17:40-18:10 UT are more than 200% near the E region peak height but only about 10% near the F region peak height; as a result, it leads to an unusual phenomenon that the E region electron density exceeds the F region electron density. We ascribe the unusual response to weak enhancement in EUV flux and strong enhancement in X-ray flux during this flare. To further understand this unusual feature, we analyze in detail the E region response by comparing the electron production rates derived from the measurements with those fitted by the Chapman production function. Our results demonstrate that the Chapman production theory fits the observations better in the flare time than in the nonflare time, which is attributed to the obvious difference in the solar radiation spectra at flare and nonflare times. Owing to the strong enhancement in X-ray flux during this flare, the E region electron production is more dominated by the X-ray, and the Chapman ionization theory is more applicable in the flare time than in the nonflare time. In addition, we propose a method to estimate the effective solar radiation flux from the ionospheric observations of electron density profiles. The radiation flux derived with our method agrees well with the X-ray flux at 0.1-0.8 nm observed by GOES-12.

  4. 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. [Korea Astronomy and Space Science Institute, Daejeon 305-348 (Korea, Republic of); Veronig, Astrid [IGAM/Institute of Physics, University of Graz, Universitaetsplatz 5, A-8010 Graz (Austria); Somov, B. V. [Astronomical Institute, Moscow State University, Universitetskij Prospekt 13, Moscow 119992 (Russian Federation); Moon, Y.-J. [School of Space Research, Kyung Hee University, Yongin 446-701 (Korea, Republic of); Lee, Jeongwoo [Physics Department, New Jersey Institute of Technology, 161 Warren Street, Newark, NJ 07102 (United States); Manoharan, P. K., E-mail: bhuwan@prl.res.i [Radio Astronomy Centre, Tata Institute of Fundamental Research, Udhagamandalam (Ooty) 643 001 (India)

    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 and upward motion of the LT source.

  5. Using SDO-EVE Satellite Data to Model for the First Time how Large Solar Flares Influence the Earths Ionosphere

    NASA Astrophysics Data System (ADS)

    Jensen, Joseph; Sojka, Jan; Schunk, Robert; David, Michael; Woods, Tom; Eparvier, Frank

    2012-10-01

    The earth's ionosphere is very important in our everyday life. During large solar flares the ionosphere expands to the point of disrupting communications from GPS, military, and commercial communications satellites, and even radio blackouts can occur. The EVE instrument on the SDO satellite has given unprecedented spectral resolution for the Extreme Ultraviolet(EUV) spectrum with a time cadence of 10 seconds. This has made it possible to analyze flare spectra as never before. Using the Time Dependent Ionospheric Model (TDIM) we have input this new spectral data for large solar flares and analyzed the effect on the ionosphere. We take as a test case the X1.6 flare on March 9, 2011. Even this minor X-class provides insight into how the ionospheric layers respond differently to solar flares.

  6. Electron densities in a solar flare derived from X-ray spectra

    NASA Astrophysics Data System (ADS)

    McKenzie, D. L.; Broussard, R. M.; Landecker, P. B.; Rugge, H. R.; Young, R. M.; Doschek, G. A.; Feldman, U.

    1982-01-01

    A major solar flare was observed with the RAP crystal of the SOLEX B spectrometer. The spectra were obtained by scanning back and forth between Bragg angles of 17.4 deg and 61.7 deg (7.8 to 23 A) at a rate of 0.525 degrees-.15. A full scan took 84.5 sec. A line list identifying more than 100 lines observed in this flare was compiled. Measurements of the density sensitive O 7 lines near 22 A are discussed.

  7. Evidence for explosive chromospheric evaporation in a solar flare observed with SMM

    NASA Technical Reports Server (NTRS)

    Zarro, D. M.; Saba, J. L. R.; Strong, K. T.; Canfield, R. C.; Metcalf, T.

    1986-01-01

    SMM 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 upflow motions, was observed in the coronal Ca XIX line during the soft X-ray rise phase. H-alpha redshifts, indicative of downward motions, were observed simultaneously in bright flare kernels during the period of hard X-ray emission. It is shown that, to within observational errors, the impulsive phase momentum transported by the upflowing soft X-ray plasma is equivalent to that of the downward moving chromospheric material.

  8. Magnetic Energy Dissipation during the 2014 March 29 Solar Flares

    E-print Network

    Aschwanden, Markus J

    2015-01-01

    We calculated the time evolution of the free magnetic energy during the 2014-Mar-29 flare (SOL2014-03-29T17:48), the first X-class flare detected by IRIS. The free energy was calculated from the difference between the nonpotential field, constrained by the geometry of observed loop structures, and the potential field. We use AIA/SDO and IRIS images to delineate the geometry of coronal loops in EUV wavelengths, as well as to trace magnetic field directions in UV wavelengths in the chromosphere and transition region. We find an identical evolution of the free energy for both the coronal and chromospheric tracers, as well as agreement between AIA and IRIS results, with a peak free energy of $E_{free}(t_{peak}) \\approx (45 \\pm 2) \\times 10^{30}$ erg, which decreases by an amount of $\\Delta E_{free} \\approx (29 \\pm 3) \\times 10^{30}$ erg during the flare decay phase. The consistency of free energies measured from different EUV and UV wavelengths for the first time here, demonstrates that vertical electric currents...

  9. Diagnostics of energetic electrons with anisotropic distributions in solar flares. I. Hard X-rays bremsstrahlung emission

    Microsoft Academic Search

    V. V. Zharkova; A. A. Kuznetsov; T. V. Siversky

    2010-01-01

    Aims: The paper aims are to simulate steady-state distributions of electrons beams precipitating in collisional and Ohmic losses with pitch angle anisotropy into a flaring atmosphere with converging magnetic field and to apply these to the interpretation of HXR photon spectra, directivity and polarization observed for different photon energies and flare positions on the solar disk. Methods: Summary approximation method

  10. Solar Flare Hard X-ray Spectra Possibly Inconsistent with the Collisional Thick Target Model

    E-print Network

    Eduard P. Kontar; John C. Brown

    2005-08-19

    Recent progress in solar Hard X-ray (HXR) observations with RHESSI data and methods for spectral inversion allow us to study model-independent mean electron flux spectra in solar flares. We report several hard X-ray events observed by RHESSI in which the photon spectra $I(\\epsilon)$ are such that the inferred source mean electron spectra are not consistent with the standard model of collisional transport in solar flares. The observed photon spectra are so flat locally that the recovered mean electron flux spectra show a dip around 17-31 keV. While we note that alternative explanations, unrelated to electron transport, have not been ruled out, we focus on the physical implications of this tentative result for the collisional thick-target model.

  11. Solar flare proton rigidity spectra deduced from cosmic ray neutron monitor observations

    NASA Technical Reports Server (NTRS)

    Lockwood, J. A.; Webber, W. R.; Hsieh, L.

    1974-01-01

    The solar flare proton rigidity spectra for several flares occurring between 1967 and 1972 have been deduced from the ground level cosmic ray neutron monitor observations. To obtain consistent agreement for all the ground level events (GLEs) analyzed, the specific yield functions of Lockwood and Webber (1967) must be reduced slightly below P = 1.6 GV. The typical spectral indices of solar cosmic rays deduced for GLEs vary from 4 to 6 if the differential spectrum is represented by KP to the minus gamma power. Only occasionally is the spectrum as steep as 8 or 9. The observed spectral index is independent of the magnitude of the integral solar proton flux above 1 GV.

  12. Localization of HXR and H-alpha impulsive brightenings during the solar flares

    NASA Astrophysics Data System (ADS)

    Radziszewski, Krzysztof; Rudawy, Pawel

    We investigated localization of hard X-ray radiation (HXR) and H-alpha impulsive brightenings recorded during solar flares. Using high cadence observations we analysed temporal relation-ships and mutually changes of localizations as well as intensity variations of the non-thermal HXR and thermal H-alpha sources. The visual data (so-called spectra-images) were collected with the Multi-Channel Subtractive Double Pass (MSDP) spectrograph and Solar Eclipse Coro-nal Imaging System (SECIS) in Bialkow Observatory (University of Wroclaw, Poland) in H-alpha line with high time resolution (up to 50 ms). The HXR images were reconstructed from Reuven Ramaty High Energy Solar Spectroscopic Imager (RHESSI) observations, using the PIXON method. Ultraviolet observations from Transition Region and Coronal Explorer (TRACE) satellite were used for localizations of anchors of hot coronal loops within the solar flare regions. We found good conformity of HXR non-thermal sources with H-alpha emission, confirming our earlier results showing very fast radiative response of chromosphere in H-alpha range during impulsive phase of solar flares.

  13. New evidence of EIBS & IINF model on energy release in solar flare

    NASA Astrophysics Data System (ADS)

    Lu, Run Bao

    I developed a model named electron-ion bound state and its introducing nuclear fusion EIBS IINF in 1994 It met thoroughly and widely doubt The EIBS IINF model give the idea for solar flare energy release as following these are two independent processes of emission in solar flare p-e-p sim 12 5keV soft X-ray and p-e-A sim 25keV are source of soft X-ray sim 12 5keV or 25keV mainly d -e-d sim 25keV and d d fusion and secondary reactions producing gamma -ray are source of hard X-ray sim 13keV Widely accepted Neupert effect model or evaporation model or thick target model is contradiction to observations New observations by BATSE SPEC and LAD especially by RHESSI provide firmly evidences indicating that the EIBS IINF model is suitable to explain the mechanism of energy release in solar flare Reference 1 R P Lin P T Fetter and R A Schwartz APJ557 L125-L128 2001 2 S Krucker and R P Lin Solar Phys 210 229-243 2002 3 A O Benz and P C Grigis Solar Physics 210 431-444 2002

  14. Arcade and Supra-Arcade Structures During the Record X28 Solar Flare of 2003 November 04

    NASA Astrophysics Data System (ADS)

    Hill, S. M. H.

    2004-05-01

    Important insights into the thermal and morphological evolution of solar eruptions are gained by analysis of high-cadence, multi-band observations. Of particular importance are synoptic observations, which can capture global data on extreme events. While rare, such intense activity can serve to highlight general principles with exceptional clarity. Presented here is a study of arcade and supra-arcade structures associated with the X28 limb flare of 2003 November 4. This flare holds the record for largest estimated soft X-ray (SXR) flux. Ha data from MLSO, extreme ultraviolet (EUV) data from SOHO EIT, and soft X-ray data from GOES-12 SXI are used to provide images covering plasma emission temperatures from 10000K to greater than 5 MK. This study explores the data from several perspectives. First, the observations are examined for persistence of loop structures as they cool through different instrument band passes and via examination of temperature and emission measure maps constructed from SXI data. Second, the data are examined for evidence of supra-arcade fans and downflows in the EUV and SXR bands. Third, arcade vertical temperature gradients and thermal evolution are examined and compared to a simple cooling model. Where appropriate, the properties of this extraordinary event are compared with those of more modest events. In the course of this work the occurrence of associated phenomena such as dimmings, pre-event brightening, and coronal waves are noted.

  15. Non-linear cosmic ray interaction with solar wind: Monitoring of flare energetic particle and solar wind matter space-time distributions by gamma rays

    Microsoft Academic Search

    Lev I. Dorman

    2006-01-01

    For great solar flare events we calculate expected gamma-ray fluxes in periods of flare energetic particle (FEP) generation and propagation. We calculate the expected space-time-energy distribution of these particles in the Heliosphere in the periods of FEP events. On the basis of investigations of cosmic ray non-linear interaction with solar wind we determine also the expected space-time distribution of solar

  16. Non-linear cosmic ray interaction with solar wind, 1. Monitoring of flare energetic particle and solar wind matter space - time distributions by gamma rays

    Microsoft Academic Search

    L. I. Dorman

    2004-01-01

    For great solar flare events we calculate expected gamma-ray fluxes in periods of flare energetic particle (FEP) generation and propagation. We calculate the expected space-time-energy distribution of these particles in the Heliosphere in the periods of FEP events. On the basis of investigations of cosmic ray non-linear interaction with solar wind we determine also the expected space-time distribution of solar

  17. OCCURRENCE OF EXTREME SOLAR PARTICLE EVENTS: ASSESSMENT FROM HISTORICAL PROXY DATA

    SciTech Connect

    Usoskin, Ilya G. [Sodankylae Geophysical Observatory (Oulu unit) and Department of Physical Sciences, University of Oulu, FIN-90014 Oulu (Finland); Kovaltsov, Gennady A., E-mail: ilya.usoskin@oulu.fi [Ioffe Physical-Technical Institute of RAS, 194021 St. Petersburg (Russian Federation)

    2012-09-20

    The probability of occurrence of extreme solar particle events (SPEs) with proton fluence (>30 MeV) F{sub 30} {>=} 10{sup 10} cm{sup -2} is evaluated based on data on the cosmogenic isotopes {sup 14}C and {sup 10}Be in terrestrial archives covering centennial-millennial timescales. Four potential candidates with F{sub 30} = (1-1.5) Multiplication-Sign 10{sup 10} cm{sup -2} and no events with F{sub 30} > 2 Multiplication-Sign 10{sup 10} cm{sup -2} are identified since 1400 AD in the annually resolved {sup 10}Be data. A strong SPE related to the Carrington flare of 1859 AD is not supported by the data. For the last 11,400 years, 19 SPE candidates with F{sub 30} = (1-3) Multiplication-Sign 10{sup 10} cm{sup -2} are found and clearly no event with F{sub 30} > 5 Multiplication-Sign 10{sup 10} cm{sup -2} (50 times the SPE of 1956 February 23) has occurred. These values serve as observational upper limits on the strength of SPEs on the timescale of tens of millennia. Two events, ca. 780 and 1460 AD, appear in different data series making them strong candidates for extreme SPEs. We build a distribution of the occurrence probability of extreme SPEs, providing a new strict observational constraint. Practical limits can be set as F{sub 30} Almost-Equal-To 1, 2-3, and 5 Multiplication-Sign 10{sup 10} cm{sup -2} for occurrence probabilities Almost-Equal-To 10{sup -2}, 10{sup -3}, and 10{sup -4} yr{sup -1}, respectively. Because of the uncertainties, our results should be interpreted as a conservative upper limit on the SPE occurrence near Earth. The mean solar energetic particle (SEP) flux is evaluated as Almost-Equal-To 40 (cm{sup 2} s){sup -1}, in agreement with estimates from lunar rocks. On average, extreme SPEs contribute about 10% to the total SEP fluence.

  18. Examination of solar radio burst onsets in view of different flare scenarios and preflare structures

    NASA Astrophysics Data System (ADS)

    Krueger, A.; Aurass, H.; Kliem, B.; Urpo, S.

    The time profiles of the solar microwave emission exhibit various phenomena reflecting the evolution of magnetic flux tubes before and during the onset of flare events. Different scenarios are possible to describe the processes of energy release in a flux tube and the interaction of a number of tubes during the preflare stage and the early flare development. Multi-peak structures at quite different time scales displayed by flux records at mm-, cm-, and dm-waves are examined; they raise the question how to distinguish between repeated energy release at one site and the propagation of the flare disturbances over an extended source area. A discussion of observed time scales and released energy in the frame of some scenarios is carried out.

  19. An equation for the evolution of solar and stellar flare loops

    NASA Technical Reports Server (NTRS)

    Fisher, George H.; Hawley, Suzanne L.

    1990-01-01

    An ordinary differential equation describing the evolution of a coronal loop subjected to a spatially uniform but time-varying heating rate is discussed. It is assumed that the duration of heating is long compared to the sound transit time through the loop, which is assumed to have uniform cross section area. The form of the equation changes as the loop evolves through three states: 'strong evaporation', 'scaling law behavior', and 'strong condensation'. Solutions to the equation may be used to compute the time dependence of the average coronal temperature and emission measure for an assumed temporal variation of the flare heating rate. The results computed from the model agree reasonably well with recent published numerical simulations and may be obtained with far less computational effort. The model is then used to study the May 21, 1980, solar flare observed by SMM and the giant April 12, 1985, flare observed on the star AD Leo.

  20. Characteristics of Solar Flare Doppler Shift Oscillations Observed with the Bragg Crystal Spectrometer on Yohkoh

    E-print Network

    John T. Mariska

    2005-11-02

    This paper reports the results of a survey of Doppler shift oscillations measured during solar flares in emission lines of S XV and Ca XIX with the Bragg Crystal Spectrometer (BCS) on Yohkoh. Data from 20 flares that show oscillatory behavior in the measured Doppler shifts have been fitted to determine the properties of the oscillations. Results from both BCS channels show average oscillation periods of 5.5 +/- 2.7 minutes, decay times of 5.0 +/-2.5 minutes, amplitudes of 17.1 +/- 17.0 km/s, and inferred displacements of 1070 +/- 1710 km, where the listed errors are the standard deviations of the sample means. For some of the flares, intensity fluctuations are also observed. These lag the Doppler shift oscillations by 1/4 period, strongly suggesting that the oscillations are standing slow mode waves. The relationship between the oscillation period and the decay time is consistent with conductive damping of the oscillations.

  1. Wavelength dependence of solar irradiance enhancement during X-class flares and its influence on the upper atmosphere

    NASA Astrophysics Data System (ADS)

    Huang, Yanshi; Richmond, Arthur D.; Deng, Yue; Chamberlin, Phillip C.; Qian, Liying; Solomon, Stanley C.; Roble, Raymond G.; Xiao, Zuo

    2014-08-01

    The wavelength dependence of solar irradiance enhancement during flare events is one of the important factors in determining how the Thermosphere-Ionosphere (T-I) system responds to flares. To investigate the wavelength dependence of flare enhancement, the Flare Irradiance Spectral Model (FISM) was run for 61 X-class flares. The absolute and the percentage increases of solar irradiance at flare peaks, compared to pre-flare conditions, have clear wavelength dependences. The 0-14 nm irradiance increases much more (~680% on average) than that in the 14-25 nm waveband (~65% on average), except at 24 nm (~220%). The average percentage increases for the 25-105 nm and 122-190 nm wavebands are ~120% and ~35%, respectively. The influence of 6 different wavebands (0-14 nm, 14-25 nm, 25-105 nm, 105-120 nm, 121.56 nm, and 122-175 nm) on the thermosphere was examined for the October 28th, 2003 flare (X17-class) event by coupling FISM with the National Center for Atmospheric Research (NCAR) Thermosphere-Ionosphere-Electrodynamics General Circulation Model (TIE-GCM) under geomagnetically quiet conditions (Kp=1). While the enhancement in the 0-14 nm waveband caused the largest enhancement of the globally integrated solar heating, the impact of solar irradiance enhancement on the thermosphere at 400 km is largest for the 25-105 nm waveband (EUV), which accounts for about 33 K of the total 45 K temperature enhancement, and ~7.4% of the total ~11.5% neutral density enhancement. The effect of 122-175 nm flare radiation on the thermosphere is rather small. The study also illustrates that the high-altitude thermospheric response to the flare radiation at 0-175 nm is almost a linear combination of the responses to the individual wavebands. The upper thermospheric temperature and density enhancements peaked 3-5 h after the maximum flare radiation.

  2. The flare origin of Forbush decreases not associated with solar flares on the visible hemisphere of the Sun

    NASA Astrophysics Data System (ADS)

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

    1985-08-01

    Investigations have shown that Forbush decreases (Fds) are produced by the propagation into the interplanetary space of a strong perturbation originating from a solar flare (Sf) accompanied by Type IV radioemission. As the front of the perturbation propagates into the interplanetary space, the region in which the galactic cosmic rays are modulated (Fd-modulated region) rotates westward with the Sun and is generally included between two boundary streams; therefore the Fds not associated with observed type IV Sfs (N.Ass.Fds) are likely to be produced by type IV Sfs occurred on the Sun's backside: these vents can be observed when the Earth crosses the corotating Western boundary of the modulated region.

  3. Electron Densities in Solar Flare Loops, Chromospheric Evaporation Upflows, and Acceleration Sites

    NASA Technical Reports Server (NTRS)

    Aschwanden, Markus J.; Benz, Arnold O.

    1996-01-01

    We compare electron densities measured at three different locations in solar flares: (1) in Soft X-Ray (SXR) loops, determined from SXR emission measures and loop diameters from Yohkoh Soft X-Ray Telescope maps (n(sub e, sup SXR) = (0.2-2.5) x 10(exp 11)/ cu cm); (2) in chromospheric evaporation upflows, inferred from plasma frequency cutoffs of decimetric radio bursts detected with the 0.1-3 GHz spectrometer Phoenix of ETH Zuerich (n(sub e, sup upflow) = (0.3-11) x 10(exp 10)/cu cm; and (3) in acceleration sites, inferred from the plasma frequency at the separatrix between upward-accelerated (type III bursts) and downward-accelerated (reverse-drift bursts) electron beams [n(sub e, sup acc) = (0.6-10) x 10(exp 9)/cu cm]. The comparison of these density measurements, obtained from 44 flare episodes (during 14 different flares), demonstrates the compatibility of flare plasma density diagnostics with SXR and radio methods. The density in the upflowing plasma is found to be somewhat lower than in the filled loops, having ratios in a range n(sub e, sup upflow)/n(sub e, sup SXR) = 0.02-1.3, and a factor of 3.6 higher behind the upflow front. The acceleration sites are found to have a much lower density than the SXR-bright flare loops, i.e., n(sub e, sup acc)/n(sub e, sup SXR) = 0.005- 0.13, and thus must be physically displaced from the SXR-bright flare loops. The scaling law between electron time-of-flight distances l' and loop half-lengths s, l'/s = 1.4 +/- 0.3, recently established by Aschwanden et al. suggests that the centroid of the acceleration region is located above the SXR-bright flare loop, as envisioned in cusp geometries (e.g., in magnetic reconnection models).

  4. Plasma heating to super-hot temperatures (>30 MK) in the August 9, 2011 solar flare

    NASA Astrophysics Data System (ADS)

    Sharykin, I. N.; Struminskii, A. B.; Zimovets, I. V.

    2015-01-01

    We investigate the August 9, 2011 solar flare of X-ray class X6.9, the "hottest" flare from 2000 to 2012, with a peak plasma temperature according to GOES data of ?32.5 MK. Our goal is to determine the cause of such an anomalously high plasma temperature and to investigate the energy balance in the flare region with allowance made for the presence of a super-hot plasma (>30 MK). We analyze the RHESSI, GOES, AIA/SDO, and EVE/SDO data and discuss the spatial structure of the flare region and the results of our spectral analysis of its X-ray emission. Our analysis of the RHESSI X-ray spectra is performed in the one-temperature and two-temperature approximations by taking into account the emission of hot (˜20 MK) and super-hot (˜45 MK) plasmas. The hard X-ray spectrum in both models is fitted by power laws. The observed peculiarities of the flare are shown to be better explained in terms of the two-temperature model, in which the super-hot plasma is located at the flare loop tops (or in the magnetic cusp region). The formation of the super-hot plasma can be associated with its heating through primary energy release and with the suppression of thermal conduction. The anomalously high temperature (33 MK according to GOES) is most likely to be an artefact of the method for calculating the temperature based on two-channel GOES measurements in the one-temperature approximation applied to the emission of a multi-temperature flare plasma with a minor contribution from the low-temperature part of the differential emission measure.

  5. Multiwavelength analysis of a well observed flare from SMM. [Solar Maximum Mission

    NASA Technical Reports Server (NTRS)

    Macneice, P.; Pallavicini, R.; Mason, H. E.; Simnett, G. M.; Antonucci, E.; Shine, R. A.; Dennis, B. R.

    1985-01-01

    Observations of an M 1.4 flare which began at 17:00 UT on November 12, 1980, are presented and analyzed. Ground based H-alpha and magnetogram data have been combined with EUV, soft and hard X-ray observations made with instruments on-board the Solar Maximum Mission satellite. The preflare phase was marked by a gradual brightening of the flare site in O v and the disappearance of an H-alpha filament. Filament ejecta were seen in O v moving southward at a speed of about 60 km/s, before the impulsive phase. The flare loop footpoints brightened in H-alpha and the Ca XIX resonance line broadened dramatically 2 min before the impulsive phase. Nonthermal hard X-ray emission was detected from the loop footpoints during the impulsive phase, while during the same period blue-shifts corresponding to upflows of 200-250 km/s were seen in Ca XIX. Evidence was found for energy deposition in both the chromosphere and corona at a number of stages during the flare. Two widely studied mechanisms for the production of the high temperature soft X-ray flare plasma in the corona are considered, i.e. chromospheric evaporation, and a model in which the heating and transfer of material occurs between flux tubes during reconnection.

  6. Faint Coronal Hard X-rays From Accelerated Electrons in Solar Flares

    NASA Astrophysics Data System (ADS)

    Glesener, Lindsay Erin

    Solar flares are huge explosions on the Sun that release a tremendous amount of energy from the coronal magnetic field, up to 1033 ergs, in a short time (100--1000 seconds), with much of the energy going into accelerated electrons and ions. An efficient acceleration mechanism is needed, but the details of this mechanism remain relatively unknown. A fraction of this explosive energy reaches the Earth in the form of energetic particles, producing geomagnetic storms and posing dangers to spaceborne instruments, astronauts, and Earthbound power grids. There are thus practical reasons, as well as intellectual ones, for wishing to understand this extraordinary form of energy release. Through imaging spectroscopy of the hard X-ray (HXR) emission from solar flares, the behavior of flare-accelerated electrons can be studied. The Reuven Ramaty High Energy Solar Spectroscopic Imager (RHESSI ) spacecraft launched in 2002 with the goal of better understanding flare particle acceleration. Using rotation modulation collimators, RHESSI is able to cover a wide energy range (3 keV--17 MeV) with fine angular and energy resolutions. RHESSI's success in the last 10 years in investigating the relationship between energetic electrons and ions, the nature of faint sources in the corona, the energy distribution of flares, and several other topics have significantly advanced the understanding of flares. But along with the wealth of information revealed by RHESSI come some clear observational challenges. Very few, if any, RHESSI observations have come close to imaging the electron acceleration region itself. This is undoubtedly due to a lack of both sensitivity (HXRs from electron beams in the tenuous corona are faint) and dynamic range (HXR sources at chromospheric flare footpoints are much brighter and tend to obscure faint coronal sources). Greater sensitivity is also required to investigate the role that small flares in the quiet Sun could play in heating the corona. The Focusing Optics X-ray Solar Imager (FOXSI ) is a developing project to address these observational difficulties. FOXSI is a sounding rocket payload developed under NASA's Low Cost Access to Space program. The project spearheads a shift to using direct imaging via focusing grazing-incidence HXR optics rather than the indirect Fourier techniques used by RHESSI and its predecessors. Such optics can attain higher sensitivity since photons are focused onto a small detector volume and have significantly better dynamic range than Fourier methods do. On November 2, 2012 the FOXSI rocket payload was flown for a 6-minute observation and successfully imaged a solar flare, providing the first focused HXR spectroscopic images of the Sun above 5 keV. The motivation, construction, testing, and flight of FOXSI will be described in this text, along with case studies on the use of RHESSI to analyze unique coronal HXR sources from two solar flares.

  7. Investigations of Solar X-ray flares from quiet Sun by instrument "PENGUIN-M" onboard satellite "CORONAS-PHOTON"

    NASA Astrophysics Data System (ADS)

    Glyanenko, Alexander; Kotov, Yury; Dergachev, Valentin; Yurov, Vitaly; Savchenko, Mikhail; Lazutkov, Vadim; Matveev, Gennady; Arkhangelsky, Andrey; Skorodumov, Dmitry; Pyatigorsky, Aleksei; Kruglov, Evgeny

    Hard X-rays spectrometer and polarimeter PENGUIN-M was launched in January, 31 2009 onboard CORONAS-PHOTON satellite. PENGUIN-M has two energy ranges: -1,8-20 keV (13 energy channels), 18-450 keV (40 energy channels). From the end of February, 2009 up to December, 1, 2009, more then 100 small Solar flares with classes A and B (GOES classification) and a dozen flares of C-class it was registered. Light profiles and data on fluxes in 1,8 -20 keV range were used for statistical study of these flares parameters. Time profiles have resolution 0,2 -1 sec. For flares of B and C-classes we calculate main physical parameters for flaring plasma properties (plasma temperature -T and Emission Measure -EM) using mono-thermal model for emitting region with time resolution 2 -10 sec. The result of statistical analysis of flare characteristics are discussed.

  8. The Gamma-Ray Imager/Polarimeter for Solar Flares (GRIPS)

    NASA Technical Reports Server (NTRS)

    Shih, Albert Y.; Lin, Robert P.; Hurford, Gordon J.; Duncan, Nicole A.; Saint-Hilaire, Pascal; Bain, Hazel M.; Boggs, Steven E.; Zoglauer, Andreas C.; Smith, David M.; Tajima, Hiroyasu; Amman, Mark S.; Takahashi, Tadayuki

    2012-01-01

    The balloon-borne Gamma-Ray Imager/Polarimeter for Solar flares (GRIPS) instrument will provide a near-optimal combination of high-resolution imaging, spectroscopy, and polarimetry of solar-flare gamma-ray/hard X-ray emissions from approximately 20 keV to greater than approximately 10 MeV. GRIPS will address questions raised by recent solar flare observations regarding particle acceleration and energy release, such as: What causes the spatial separation between energetic electrons producing hard X-rays and energetic ions producing gamma-ray lines? How anisotropic are the relativistic electrons, and why can they dominate in the corona? How do the compositions of accelerated and ambient material vary with space and time, and why? The spectrometer/polarimeter consists of sixteen 3D position-sensitive germanium detectors (3D-GeDs), where each energy deposition is individually recorded with an energy resolution of a few keV FWHM and a spatial resolution of less than 0.1 cubic millimeter. Imaging is accomplished by a single multi-pitch rotating modulator (MPRM), a 2.5-centimeter thick tungsten alloy slit/slat grid with pitches that range quasi-continuously from 1 to 13 millimeters. The MPRM is situated 8 meters from the spectrometer to provide excellent image quality and unparalleled angular resolution at gamma-ray energies (12.5 arcsec FWHM), sufficient to separate 2.2 MeV footpoint sources for almost all flares. Polarimetry is accomplished by analyzing the anisotropy of reconstructed Compton scattering in the 3D-GeDs (i.e., as an active scatterer), with an estimated minimum detectable polarization of a few percent at 150-650 keV in an X-class flare. GRIPS is scheduled for a continental-US engineering test flight in fall 2013, followed by long or ultra-long duration balloon flights in Antarctica.

  9. COMBINED STEREO/RHESSI STUDY OF CORONAL MASS EJECTION ACCELERATION AND PARTICLE ACCELERATION IN SOLAR FLARES

    SciTech Connect

    Temmer, M.; Veronig, A. M. [IGAM/Kanzelhoehe Observatory, Institute of Physics, Universitaet Graz, Universitaetsplatz 5, A-8010 Graz (Austria); Kontar, E. P. [Department of Physics and Astronomy, University of Glasgow, Glasgow G12 8QQ (United Kingdom); Krucker, S. [Space Sciences Laboratory, University of California, Berkeley, CA 94720-7450 (United States); Vrsnak, B., E-mail: mat@igam.uni-graz.a, E-mail: asv@igam.uni-graz.a, E-mail: eduard@astro.gla.ac.u, E-mail: krucker@ssl.berkeley.ed, E-mail: bvrsnak@gmail.co [Hvar Observatory, Faculty of Geodesy, University of Zagreb, Kaciceva 26, HR-10000 Zagreb (Croatia)

    2010-04-01

    Using the potential of two unprecedented missions, Solar Terrestrial Relations Observatory (STEREO) and Reuven Ramaty High-Energy Solar Spectroscopic Imager (RHESSI), we study three well-observed fast coronal mass ejections (CMEs) that occurred close to the limb together with their associated high-energy flare emissions in terms of RHESSI hard X-ray (HXR) spectra and flux evolution. From STEREO/EUVI and STEREO/COR1 data, the full CME kinematics of the impulsive acceleration phase up to {approx}4 R{sub sun} is measured with a high time cadence of <=2.5 minutes. For deriving CME velocity and acceleration, we apply and test a new algorithm based on regularization methods. The CME maximum acceleration is achieved at heights h <= 0.4 R{sub sun}, and the peak velocity at h <= 2.1 R{sub sun} (in one case, as small as 0.5 R{sub sun}). We find that the CME acceleration profile and the flare energy release as evidenced in the RHESSI HXR flux evolve in a synchronized manner. These results support the 'standard' flare/CME model which is characterized by a feedback relationship between the large-scale CME acceleration process and the energy release in the associated flare.

  10. Spectral Evolution of Coronal Hard X-ray Sources during Solar Flares

    NASA Astrophysics Data System (ADS)

    Krucker, Sam; Lin, R. P.

    2006-06-01

    Hard X-ray (HXR) emissions during solar flares are most prominent at chromospheric footpoints of flare loops which reveal where flare-accelerated electrons lose their energy by collision. The lower density in the corona makes it much more difficult to detect coronal HXR emissions, but coronal HXR sources directly reveal insights into the acceleration region (e.g. Masuda et al. 1994). Observations with Reuven Ramaty High Energy Solar Spectroscopic Imager (RHESSI) give for the first time detailed spatial and spectral observations in the HXR range. Initial results of a few events reveal at least two different spectral behavior, possibly indicating two different acceleration mechanisms: (1) Coronal HXR sources with a 'soft-hard-soft' behavior (Battaglia & Benz 2006), and (2) sources that show spectral hardening in time, i.e. a 'soft-hard-harder' behavior (Krucker et al. 2005). After a short review of recent RHESSI observations, we will present statistical results on the spectral evolution of coronal HXR sources of 50 partly occulted limb flares seen by RHESSI.

  11. Super-hot (T > 30 MK) thermal plasma in solar flares

    NASA Astrophysics Data System (ADS)

    Caspi, Amir

    2010-05-01

    The Sun offers a convenient nearby laboratory to study the physical processes of particle acceleration and impulsive energy release in magnetized plasmas that occur throughout the universe, from planetary magnetospheres to black hole accretion disks. Solar flares are the most powerful explosions in the solar system, releasing up to 1032-1033 ergs over only 100-1,000 seconds. These events can accelerate electrons up to hundreds of MeV and can heat plasma to tens of MK, exceeding ?40 MK in the most intense flares. The accelerated electrons and the hot plasma each contain tens of percent of the total flare energy, indicating an intimate link between particle acceleration, plasma heating, and flare energy release. X-ray emission is the most direct signature of these processes; accelerated electrons emit hard X-ray bremsstrahlung as they collide with the ambient atmosphere, while hot plasma emits soft X-rays from both bremsstrahlung and excitation lines of highly-ionized atoms. The Reuven Ramaty High Energy Solar Spectroscopic Imager (RHESSI) observes this emission from ?3 keV to ?17 MeV with unprecedented spectral, spatial, and temporal resolution, providing the most precise measurements of the X-ray flare spectrum and enabling the most accurate characterization of the X-ray-emitting hot and accelerated electron populations. RHESSI observations show that "super-hot" temperatures exceeding ?30 MK are common in large flares but are achieved almost exclusively by X-class events and appear to be strictly associated with coronal magnetic field strengths exceeding ?170 Gauss; these results suggest a direct link between the magnetic field and heating of super-hot plasma, and that super-hot flares may require a minimum threshold of field strength and overall flare intensity. Imaging and spectroscopic observations of the 2002 July 23 X4.8 event show that the superhot plasma is both spectrally and spatially distinct from the usual ?10-20 MK plasma observed in nearly all flares, and is located above rather than at the top of the loop containing the cooler plasma. It exists with high density even during the pre-impulsive phase, which is dominated by coronal non-thermal emission with negligible footpoints, suggesting that particle acceleration and plasma heating are intrinsically related but that, rather than the traditional picture of chromospheric evaporation, the origins of super-hot plasma may be the compression and subsequent thermalization of ambient material accelerated in the reconnection region above the flare loop, a physically-plausible process not detectable with current instruments but potentially observable with future telescopes. Explaining the origins of super-hot plasma would thus ultimately help to understand the mechanisms of particle acceleration and impulsive energy release in solar flares.

  12. Excitation of geomagnetic micropulsations by means of ionospheric conductivity changes induced by solar flares. (Volumes I and II)

    Microsoft Academic Search

    1986-01-01

    The premise is developed that solar flares with large components in the X-ray and euv spectra stimulate geomagnetic pulsations in the earth's magnetosphere by means of sudden conductivity changes in the dayside ionosphere. Ground-based observations of 7-22 mHz (Pc4 band) magnetic pulsations are shown to be associated with conductivity enhancements for four selected solar flare events in 1980. Magnetic activity

  13. Evolution of the magnetic fields of solar flare active regions from the geometry and topology of HMI/SDO magnetograms

    NASA Astrophysics Data System (ADS)

    Knyazeva, I. S.; Makarenko, N. G.

    2014-03-01

    The testing and development of topological approaches to the analysis of solar magnetic fields are considered. A technique based on the geometry of random fields, mathematical morphology and topology, and scale-space analyses are applied to describe and diagnose the pre-flare dynamics of the magnetic fields of solar active regions using HMI/SDO magnetograms. The results show that this formalism can be used to diagnose pre-flare dynamics over time intervals that are of practical interest.

  14. From Coronal Observations to MHD Simulations, the Building Blocks for 3D Models of Solar Flares (Invited Review)

    NASA Astrophysics Data System (ADS)

    Janvier, M.; Aulanier, G.; Démoulin, P.

    2015-06-01

    Solar flares are energetic events taking place in the Sun's atmosphere, and their effects can greatly impact the environment of the surrounding planets. In particular, eruptive flares, as opposed to confined flares, launch coronal mass ejections into the interplanetary medium, and as such, are one of the main drivers of space weather. After briefly reviewing the main characteristics of solar flares, we summarise the processes that can account for the build-up and release of energy during their evolution. In particular, we focus on the development of recent 3D numerical simulations that explain many of the observed flare features. These simulations can also provide predictions of the dynamical evolution of coronal and photospheric magnetic field. Here we present a few observational examples that, together with numerical modelling, point to the underlying physical mechanisms of the eruptions.

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

    NASA Astrophysics Data System (ADS)

    2005-05-01

    New results from NASA's Chandra X-ray Observatory imply that X-ray super-flares torched the young Solar System. Such flares likely affected the planet-forming disk around the early Sun, and may have enhanced the survival chances of Earth. By focusing on the Orion Nebula almost continuously for 13 days, a team of scientists used Chandra to obtain the deepest X-ray observation ever taken of this or any star cluster. The Orion Nebula is the nearest rich stellar nursery, located just 1,500 light years away. These data provide an unparalleled view of 1400 young stars, 30 of which are prototypes of the early Sun. The scientists discovered that these young suns erupt in enormous flares that dwarf - in energy, size, and frequency -- anything seen from the Sun today. Illustration of Large Flares Illustration of Large Flares "We don't have a time machine to see how the young Sun behaved, but the next best thing is to observe Sun-like stars in Orion," said Scott Wolk of Harvard-Smithsonian Center for Astrophysics in Cambridge, Mass. "We are getting a unique look at stars between one and 10 million years old - a time when planets form." A key result is that the more violent stars produce flares that are a hundred times as energetic as the more docile ones. This difference may specifically affect the fate of planets that are relatively small and rocky, like the Earth. "Big X-ray flares could lead to planetary systems like ours where Earth is a safe distance from the Sun," said Eric Feigelson of Penn State University in University Park, and principal investigator for the international Chandra Orion Ultradeep Project. "Stars with smaller flares, on the other hand, might end up with Earth-like planets plummeting into the star." Animation of X-ray Flares from a Young Sun Animation of X-ray Flares from a "Young Sun" According to recent theoretical work, X-ray flares can create turbulence when they strike planet-forming disks, and this affects the position of rocky planets as they 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

  16. Statistical Correlation between Solar Flares and GLE during 2000

    Microsoft Academic Search

    N. Martinic; F. Osco; N. Huaygua; R. Ticona; N. Inoue; Y. Takahashi; K. Miyazawa; K. Shinozaki; A. Mahrous; N. Kawasumi; I. Tsushima; K. Hashimoto; K. Honda; A. Ohsawa; M. Tamada; N. Ohmori; H. Aoki

    2001-01-01

    Using the 12NM64 and 45 plastic scintillators during 2000, both with rate recording sampling of less or equal to one minute a correlation among are location on the solar disk, are intensities with the cosmic rays intensities fluxes as seen at the Chacaltaya monitors are investigated in order to furnish the ux signature during the current solar maximum activity. Search

  17. High energy observations of June 1980 solar flares

    Microsoft Academic Search

    B. Lokanadham; P. K. Subramanian; Allan L. Kiplinger; B. R. Dennis

    1986-01-01

    The paper presents a detailed study of the high energy X-ray observation of the most unusual solar events observed on 4 and 7 June, 1980 with the Hard X-Ray Burst Spectrometer (HXRBS) on Solar Maximum Mission (SMM) satellite. The hard X-ray data of the events are also compared with the radio microwave fluxes.

  18. The solar flare of 18 August 1979: Incoherent scatter radar data and photochemical model comparisons

    SciTech Connect

    Zinn, J.; Sutherland, C.D.; Fenimore, E.E.; Ganguly, S.

    1988-04-01

    Measurements of electron density at seven D-region altidues were made with the Arecibo radar during a Class-X solar flare on 18 August 1979. Measurements of solar x-ray fluxes during the same period were available from the GOES-2 satellite (0.5 to 4 /angstrom/ and 1 to 8 /angstrom/) and from ISEE-3 (in four bands between 26 and 400 keV). From the x-ray flux data we computed ionization rates in the D-region and the associated chemical changes, using a coupled atmospheric chemistry and diffusion model (with 836 chemical reactions and 19 vertical levels). The computed electron densities matched the data fairly well after we had adjusted the rate coefficients of two reactions. We discuss the hierarchies among the many flare-induced chemical reactions in two altitude ranges within the D-region and the effects of adjusting several other rate coefficients. 51 refs., 6 figs., 3 tabs.

  19. Properties of solar flare electrons, deduced from hard X-ray and spatially resolved microwave observations

    NASA Technical Reports Server (NTRS)

    Marsh, K. A.; Hurford, G. J.; Zirin, H.; Dulk, G. A.; Dennis, B. R.; Frost, K. J.; Orwig, L. E.

    1981-01-01

    An important question concerning an understanding of impulsive solar flares is related to the energetic electrons responsible for the microwave and the hard X-ray emission. A description is presented of an investigation in which spatially resolved microwave observations of an impulsive flare and hard X-ray data from the Solar Maximum Mission (SMM) are used to test the hypothesis that the two types of emission come from the same basic electron population. The considered observations are found to imply that the microwaves and hard X-rays were not produced by a common population of electrons with either a Maxwellian or single power-law energy distribution. It is suggested that the calculations should be repeated when observations of stronger events become available, for which a better determination of the X-ray spectrum is possible. The possibility is considered that microwaves and moderately hard X-rays come from spatially different regions.

  20. H-2, H-3, He-3 production in solar flares. [using updated cross sections and kinematics

    NASA Technical Reports Server (NTRS)

    Ramaty, R.; Kozlovsky, B.

    1974-01-01

    The production of deuterium, tritium, and helium-3 from nuclear reactions of accelerated charged particles is evaluated with the ambient solar atmosphere. Updated cross sections and kinematics are used, calculations are extended to very low energies (approximates 0.1 MeV/nucleon), and the angular distribution of the secondary particles is calculated. The calculations are compared with data on accelerated isotopes from solar flares. In particular, the August 1972 events are considered for which both He-3 and nuclear gamma rays were observed. An explanation for He-3-rich events is provided in terms of the angular distributions of secondary isotopes, and the flux of 2.2 MeV gamma rays from such flares are also predicted.

  1. Solar flare ionization in the mesosphere observed by coherent-scatter radar

    NASA Technical Reports Server (NTRS)

    Parker, J. W.; Bowhill, S. A.

    1986-01-01

    The coherent-scatter technique, as used with the Urbana radar, is able to measure relative changes in electron density at one altitude during the progress of a solar flare when that altitude contains a statistically steady turbulent layer. This work describes the analysis of Urbana coherent-scatter data from the times of 13 solar flares in the period from 1978 to 1983. Previous methods of measuring electron density changes in the D-region are summarized. Models of X-ray spectra, photoionization rates, and ion-recombination reaction schemes are reviewed. The coherent-scatter technique is briefly described, and a model is developed which relates changes in scattered power to changes in electron density. An analysis technique is developed using X-ray flux data from geostationary satellites and coherent scatter data from the Urbana radar which empirically distinguishes between proposed D-region ion-chemical schemes, and estimates the nonflare ion-pair production rate.

  2. Power Laws in Solar Flares: Self-Organized Criticality or Turbulence?

    E-print Network

    Guido Boffetta; Vincenzo Carbone; Paolo Giuliani; Pierluigi Veltri; Angelo Vulpiani

    1999-04-23

    We study the time evolution of Solar Flares activity by looking at the statistics of quiescent times $\\tau_{L}$ between successive bursts. The analysis of 20 years of data reveals a power law distribution with exponent $\\alpha \\simeq 2.4$ which is an indication of complex dynamics with long correlation times. The observed scaling behavior is in contradiction with the Self-Organized Criticality models of Solar Flares which predict Poisson-like statistics. Chaotic models, including the destabilization of the laminar phases and subsequent restabilization due to nonlinear dynamics, are able to reproduce the power law for the quiescent times. In the case of the more realistic Shell Model of MHD turbulence we are able to reproduce all the observed distributions.

  3. Measurements of solar flare enhancements to the single event upset environment in the upper atmosphere

    SciTech Connect

    Dyer, C.S.; Sims, A.J. (Space Dept., Royal Aerospace Establishment, Farnborough, Hampshire (GB)); Farren, J.; Stephen, J. (Nuclear Physics and Instrumentation Div., Harwell Lab., Oxfordshire (GB))

    1990-12-01

    The Cosmic Radiation Environment Monitor has flown regularly on a supersonic airliner over a period of eighteen months in order to explore the extent of single-event phenomena in the upper atomsphere. Quiet-time data now have good statistical precision and are compared with predictions of environment models. A number of increases and decreases were observed during the solar flare events of September and October 1989.

  4. Temperature minimum heating in solar flares by resistive dissipation of Alfven waves

    NASA Technical Reports Server (NTRS)

    Emslie, A. G.; Sturrock, P. A.

    1981-01-01

    The possibility that the strong heating produced at temperature-minimum levels during solar flares is due to resistive dissipation of Alfven waves generated by the primary energy release process in the corona is studied. It is shown how, for suitable parameters, these waves can carry their energy essentially undamped into the temperature-minimum layers and can then produce a degree of heating consistent with observations.

  5. On the Possible Connection between Photospheric 5Min Oscillation and Solar Flare Microwave Emission

    Microsoft Academic Search

    A. G. Kislyakov; V. V. Zaitsev; A. V. Stepanov; S. Urpo

    2006-01-01

    Dynamic spectra of low-frequency modulation of microwave emission from solar flares are obtained. Data of 15 bursts observed\\u000a in 1989–2000 with Metshovi radio telescope at 37 GHz have been used. During 13 bursts a 5-min modulation of the microwave\\u000a emission intensity was detected with the frequency of ?I = 3.2 0.24 (1?) mHz. Five bursts revealed a 5-min wave superimposed

  6. Interferometric microwave polarimetry as a tool for short-term solar flare prediction. Report for 19 Feb 80-31 Mar 81

    SciTech Connect

    Hurford, G.J.

    1981-08-01

    The purpose of this study is to look at a data base of interferometric solar microwave data in order to identify, evaluate and interpret preflare microwave signatures, with reference to their possible role in the short-term prediction of solar flares. Reserving the second half of this data base for verification of tentative results, 27 major flares were selected using optical, soft x-ray OR microwave flux criteria for which good quality interferometric data was available. These events were analysed in detail and very similar preflare signatures noted in four (15%) of the cases. The most common signature was a step-like increase in signal amplitude, accompanied by a decrease or reversal in the degree of polarization. Such a signature occurred between a few minutes to a few tens of minutes before the start of the impulsive phase. Optical data, available in three cases, showed the microwave changes were simultaneous with either small brightenings or small-scale filament disruptions. Preliminary results show that such microwave behavior occurs far too seldom for such an association with major flares to be a chance occurrence.

  7. SOLAR WIND DENSITY TURBULENCE AND SOLAR FLARE ELECTRON TRANSPORT FROM THE SUN TO THE EARTH

    SciTech Connect

    Reid, Hamish A. S.; Kontar, Eduard P., E-mail: hamish@astro.gla.ac.u, E-mail: eduard@astro.gla.ac.u [Department of Physics and Astronomy, University of Glasgow, G12 8QQ (United Kingdom)

    2010-09-20

    Solar flare accelerated electron beams propagating away from the Sun can interact with the turbulent interplanetary media, producing plasma waves and Type III radio emission. These electron beams are detected near the Earth with a double power-law energy spectrum. We simulate electron beam propagation from the Sun to the Earth in the weak turbulent regime taking into account the self-consistent generation of plasma waves and subsequent wave interaction with density fluctuations from low-frequency MHD turbulence. The rate at which plasma waves are induced by an unstable electron beam is reduced by background density fluctuations, most acutely when fluctuations have large amplitudes or small wavelengths. This suppression of plasma waves alters the wave distribution which changes the electron beam transport. Assuming a 5/3 Kolmogorov-type power-density spectrum of fluctuations often observed near the Earth, we investigate the corresponding energy spectrum of the electron beam after it has propagated 1 AU. We find a direct correlation between the spectrum of the double power-law below the break energy and the turbulent intensity of the background plasma. For an initial spectral index of 3.5, we find a range of spectra below the break energy between 1.6 and 2.1, with higher levels of turbulence corresponding to higher spectral indices.

  8. Coupling of Particle Acceleration and Atmospheric Dynamic Response to Impulsive Energy Release in Solar Flares

    NASA Astrophysics Data System (ADS)

    Liu, Wei; Petrosian, V.; Chen, Q.; Mariska, J.

    2012-05-01

    In solar flares, acceleration and transport of high-energy particles and fluid dynamics of the atmospheric plasma are interrelated processes coupled in a circular chain. Chromospheric evaporation, for example, can alter the density and temperature distribution along the flare loop, in particular in the acceleration site near the loop-top source. This produces a feedback on particle collisional heating, and more importantly on the energy release and acceleration process. This in turn will change the heating of the chromosphere and mass flows in the corona. In recent years, there have been increasing theoretical and observational motivations to investigate these coupled processes together in a self-consistent manner. We present here combined Fokker-­Planck modeling of particles and hydrodynamic simulation of flare plasma. We extended our earlier hybrid simulation (Liu, Petrosian, Mariska 2009) by feeding the updated plasma density and temperature at the loop-top source to the stochastic acceleration process. We find that the density enhancement causes the ratio of the electron plasma frequency to gyro-frequency to increase. This can lead to the reduction of the efficiency of electron acceleration and thus the quenching or spectral softening of nonthermal hard X-ray tails observed during the late stages of flares. This also affects the relative production of energetic electrons vs. protons (Petrosian and Liu 2004). We will compare our results with recent observations from RHESSI, SDO, and Hinode. We will also discuss their implications for cyclic spectral hardening, quasi-periodic flare pulsations, and recently imaged super-fast quasi-periodic coronal waves originating from flare kernels.

  9. Imaging and Spectral Observations of Quasi-periodic Pulsations in a Solar Flare

    NASA Astrophysics Data System (ADS)

    Li, D.; Ning, Z. J.; Zhang, Q. M.

    2015-07-01

    We explore the quasi-periodic pulsations (QPPs) in a solar flare observed by Fermi Gamma-ray Burst Monitor, Solar Dynamics Observatory, Solar Terrestrial Relations Observatory, and Interface Region Imaging Spectrograph (IRIS) on 2014 September 10. QPPs are identified as the regular and periodic peaks on the rapidly varying components, which are the light curves after removing the slowly varying components. The QPPs display only three peaks at the beginning on the hard X-ray emissions, but 10 peaks on the chromospheric and coronal line emissions, and more than seven peaks (each peak corresponds to a type III burst on the dynamic spectra) at the radio emissions. A uniform quasi-period of about 4 minutes is detected among them. AIA imaging observations exhibit that the 4-minute QPPs originate from the flare ribbon and tend to appear on the ribbon front. IRIS spectral observations show that each peak of the QPPs tends to a broad line width and a red Doppler velocity at C i, O iv, Si iv, and Fe xxi lines. Our findings indicate that the QPPs are produced by the non-thermal electrons that are accelerated by the induced quasi-periodic magnetic reconnections in this flare.

  10. Time-dependent coronal shock acceleration of energetic solar flare particles

    NASA Technical Reports Server (NTRS)

    Lee, M. A.; Ryan, J. M.

    1986-01-01

    A global time-dependent model is presented for the coronal and interplanetary shock acceleration and propagation of energetic solar flare particles. The calculations are carried out to help prove that coronal shock acceleration of solar flare particles is responsible for energetic solar flare event data gathered in interplanetary space. The model is based on the theory of diffusive shock acceleration, and requires particle speeds to be much greater than bulk velocities. Also, sufficient scattering must occur upstream and downstream of the shock for the particle scattering mean free path to be smaller than the characteristic scale lengths, which causes the same particles to encounter the shock repeatedly. A spherically symmetric shock wave is assumed, which leads to the same emission configuration for impulsively and monoenergetically emitted particles. Consideration is given to acceleration by compression at the shock front, adiabatic deceleration in the divergent downstream flow, the temporal evolution of the shock and the three-dimensional geometry of the corona. The model is used to generate normalized proton omnidirectional distributions at 1 AU and at the shock front. The spectral exhibit trends similar to those in observational data, especially proton acceleration times and the proton distribution profiles at 1 AU.

  11. Solar EUV Variability from FISM and SDO/EVE During Solar Minimum, Active, and Flaring Time Periods

    NASA Technical Reports Server (NTRS)

    Chamberlin, Phillip C.

    2011-01-01

    The Living With a Star (LWS) Focus Science Team has identified three periods of different solar activity levels for which they will be determining the Earth's Ionosphere and Thermosphere response. Not only will the team be comparing individual models (e.g. FLIP, T1MEGCM, GLOW) outcome driven by the various levels of solar activity, but the models themselves will also be compared. These models all rely on the input solar EUV (0.1 -190 nm) irradiance to drive the variability. The Flare Irradiance Spectral Model (FISM) and the EUV Variability Experiment (EVE) onboard provide the Solar Dynamics Observatory (SDO) provide the most accurate quantification of these irradiances. Presented and discussed are how much the solar EUV irradiance changes during these three scenarios, both as a function of activity and wavelength.

  12. Resik Solar X-Ray Flare Element Abundances on a Non-isothermal Assumption

    NASA Astrophysics Data System (ADS)

    Sylwester, B.; Phillips, K. J. H.; Sylwester, J.; K?pa, A.

    2015-05-01

    Solar X-ray spectra from the REntgenovsky Spektrometr s Izognutymi Kristalami (RESIK) crystal spectrometer on the CORONAS-F spacecraft (spectral range 3.3–6.1 Å) are analyzed for 33 flares using a method to derive abundances of Si, S, Ar, and K, emission lines of which feature prominently in the spectra. For each spectrum, the method first optimizes element abundances and then derives the differential emission measure as a function of temperature based on a procedure given by Sylwester et al. and Withbroe. This contrasts with our previous analyses of RESIK spectra in which an isothermal assumption was used. The revised abundances (on a logarithmic scale with A(H)=12) averaged for all the flares in the analysis are A(Si)=7.53+/- 0.08 (previously 7.89 ± 0.13), A(S)=6.91+/- 0.07 (7.16 ± 0.17), A(Ar)=6.47+/- 0.08 (6.45 ± 0.07), and A(K)=5.73+/- 0.19 (5.86 ± 0.20), with little evidence for time variations of abundances within the evolution of each flare. Our previous estimates of the Ar and K flare abundances are thus confirmed by this analysis, but those for Si and S are reduced. This suggests that the flare abundances of Si and Ar are very close to the photospheric abundance or solar proxies, while S is significantly less than photospheric and the K abundance is much higher than photospheric. These estimates differ to some extent from those in which a single enhancement factor applies to elements with first ionization potential less than 10 eV.

  13. Internal and External reconnection in a Series of Homologous Solar Flares

    NASA Technical Reports Server (NTRS)

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

    2000-01-01

    Using data from the Extreme Ultraviolet Telescope (EIT) on SOHO and the Soft X-ray Telescope (SXT) on Yohkoh, we examine a series of morphologically homologous solar flares occurring in NOAA AR 8210 over May 1-2, 1998. An emerging flux region (EFR) impacted against a sunspot to the west and next to a coronal hole to the east is the source of the repeated flaring. An SXT sigmoid parallels the EFR's neutral line at the site of the initial flaring in soft X-rays. In EIT, each flaring episode begins with the formation of a crinkle pattern external to the EFR. These EIT crinkles move out from, and then in toward, the EFR with velocities approximately 20 km/s. A shrinking and expansion of the width of the coronal hole coincides with the crinkle activity, and generation and evolution of a postflare loop system begins near the. time of crinkle formation. Using a schematic based on magnetograms of the region, we suggest that these observations are consistent with the standard reconnection-based model for solar eruptions, but modified by the presence of the additional magnetic fields of the sunspot and coronal hole. In the schematic, internal reconnection begins inside of the EFR-associated fields, unleashing a flare, postflare loops, and a CME. External reconnection, first occurring between the escaping CME and the coronal hole field, and second occurring between fields formed as a result of the first external reconnection, results in the EIT crinkles and changes in the coronal hole boundary. By the end of the second external reconnection, the initial setup is reinstated; thus the sequence can repeat, resulting in morphologically homologous eruptions. Our inferred magnetic topology is similar to that suggested in the "breakout model" of eruptions [Antiochos, 1998], although we cannot determine if our eruptions are released primarily by the breakout mechanism (external reconnection) or, alternatively, are released primarily by the internal reconnection.

  14. Effect of solar flares flux on the propagation and modal composition of VLF signal in the lower ionosphere

    NASA Astrophysics Data System (ADS)

    Bouderba, Yasmina; Nait Amor, Samir; Tribeche, Mouloud

    2015-04-01

    The VLF radio waves propagating in the Earth-Ionosphere waveguide are sensitive to the ionospheric disturbances due to X rays solar flux. In order to understand the VLF signal response to the solar flares, the LWPC code is used to simulate the signal perturbation parameters (amplitude and phase) at fixed solar zenith angle. In this work, we used the NRK-Algiers signal data and the study was done for different flares classes. The results show that the perturbed parameters increase with the increasing solar flares flux. This increases is due to the growth of the electron density resulting from the changes of the Wait's parameters. However, the behavior of the perturbation parameters as function of distance shows different forms of signal perturbations. It was also observed that the null points move towards the transmitter location when the flare flux increases which is related to the modal composition of the propagating signal. Effectively, for a given mode, the plot of the attenuation coefficient as function of the flare flux shows a decreases when the flux increases which is more significant for high modes. Thus, the solar flares effect is to amplify the VLF signal by reducing the attenuation coefficient.

  15. EVE-RHESSI Observations of Thermal and Nonthermal Solar Flare Emission

    NASA Astrophysics Data System (ADS)

    McTiernan, James; Caspi, A.; Warren, H.

    2013-07-01

    Solar flares accelerate electrons up to hundreds of MeV and heat plasma to tens of MK. In large (GOES M- and X-class) flares, in addition to the 10-25 MK plasma thought to be the result of chromospheric evaporation, even hotter plasma (up to 50 MK) may be directly heated in the corona. While observations of hard X-ray bremmstrahlung directly probe the nonthermal electron population, for large flares the spectra below 20-30 keV are typically dominated by thermal emission. The low energy extent of the nonthermal spectrum can be only loosely quantified by hard X-ray spectrometers, resulting in significant implications for calculating flare energy budgets and for constraining possible acceleration mechanisms. A precise characterization of the thermal emission is imperative. Extreme ultraviolet observations from the EUV Variability Experiment (EVE) on-board the Solar Dynamics Observatory (SDO), combined with X-ray data from the Reuven Ramaty High Energy Spectroscopic Imager (RHESSI), currently offer the most comprehensive view of the flare temperature distribution. EVE observes EUV emission lines with peak formation temperatures of 2-20 MK, while RHESSI observes the X-ray bremsstrahlung of hot, 10-50 MK plasma; combined, the two instruments cover the full range of flare plasma temperatures. In this work, we handle the EVE-RHESSI data for a few large flares in three steps; first we calculate differential emission measures (DEMs) using EVE and RHESSI independently for purposes of cross-calibration. Second, we create combined EVE-RHESSI DEMs, fixing the nonthermal spectral parameters to those found using a RHESSI-only spectral fit. The final step is to unconstrain the nonthermal parameters (in particular, the low-energy cutoff of the spectrum) and let them be fit in the same process as the EVE-RHESSI DEM, to obtain a fully self-consistent thermal plus nonthermal model. This research is supported by NASA Heliophysics Guest Investigator Grant NNX12AH48G.

  16. Helioseismic analysis of the solar flare-induced sunquake of 2005 January 15

    NASA Astrophysics Data System (ADS)

    Moradi, H.; Donea, A.-C.; Lindsey, C.; Besliu-Ionescu, D.; Cally, P. S.

    2007-01-01

    We report the discovery of one of the most powerful sunquakes detected to date, produced by an X1.2-class solar flare in active region AR10720 on 2005 January 15. We used helioseismic holography to image the source of seismic waves emitted into the solar interior from the site of the flare. Acoustic egression power maps at 3 and 6 mHz with a 2-mHz bandpass reveal a compact acoustic source strongly correlated with impulsive hard X-ray and visible-continuum emission along the penumbral neutral line separating the two major opposing umbrae in the ?-configuration sunspot that predominates AR10720. At 6 mHz the seismic source has two components, an intense, compact kernel located on the penumbral neutral line of the ?-configuration sunspot that predominates AR10720, and a significantly more diffuse signature distributed along the neutral line up to ~15 Mm east and ~30 Mm west of the kernel. The acoustic emission signatures were directly aligned with both hard X-ray and visible continuum emission that emanated during the flare. The visible continuum emission is estimated at 2.0 × 1023 J, approximately 500 times the seismic emission of ~4 × 1020 J. The flare of 2005 January 15 exhibits the same close spatial alignment between the sources of the seismic emission and impulsive visible continuum emission as previous flares, reinforcing the hypothesis that the acoustic emission may be driven by heating of the low photosphere. However, it is a major exception in that there was no signature to indicate the inclusion of protons in the particle beams thought to supply the energy radiated by the flare. The continued strong coincidence between the sources of seismic emission and impulsive visible continuum emission in the case of a proton-deficient white-lightflare lends substantial support to the `back-warming' hypothesis, that the low photosphere is significantly heated by intense Balmer and Paschen continuum-edge radiation from the overlying chromosphere in white-light flares.

  17. Solar Flare Composition and Thermodynamics from RESIK X-ray Spectra

    E-print Network

    Sylwester, B; Phillips, K J H; Kepa, A; Mrosek, T

    2014-01-01

    Previous estimates of the solar flare abundances of Si, S, Cl, Ar, and K from the RESIK X-ray crystal spectrometer on board the CORONAS-F spacecraft were made on the assumption of isothermal X-ray emission. We investigate the effect on these estimates by relaxing this assumption and instead determining the differential emission measure (DEM) or thermal structure of the emitting plasma by re-analyzing RESIK data for a GOES class M1.0 flare on 2002 November~14 (SOL2002-11-14T22:26) for which there was good data coverage. The analysis method uses a maximum-likelihood (Withbroe--Sylwester) routine for evaluating the DEM. In a first step, called here AbuOpt, an optimized set of abundances of Si, S, Ar, and K is found that is consistent with the observed spectra. With these abundances, the differential emission measure evolution during the flare is found. The abundance optimization leads to revised abundances of silicon and sulfur in the flare plasma: $A({\\rm S}) = 6.94 \\pm 0.06$ and $A({\\rm Si}) = 7.56 \\pm 0.08$ (...

  18. Densities and mass motions in transition-zone plasmas in solar flares observed from Skylab

    NASA Technical Reports Server (NTRS)

    Cheng, C.-C.

    1980-01-01

    The electron densities and bulk motions in the transition-zone plasma of a solar flare are investigated by an analysis of EUV emission line spectra taken on Skylab. Spectra of three flares were obtained with the NRL normal incidence grating slit spectrograph in the ranges 1100-1940 and 1940-3940 A. The line ratios of transition-zone Si III lines and the intensity of the forbidden O IV 1401-A lines during flare maximum indicate electron densities on the order of 10 to the 12th/cu cm, decreasing by a factor of 2 to 3 in the flare decay phase. Line broadening of the transition-zone ions such as Si III, O IV, C IV and N V is noted, and the observed asymmetrical N V line profiles are approximated by a bi-Gaussian model of a stationary and a moving plasma component with a bulk velocity of 12 to 70 km/sec. Turbulent velocities of from 45 to 85 km/sec and from 20 to 40 km/sec are also indicated for the moving and stationary components of the transition-zone plasma, respectively.

  19. Budget of energetic electrons during solar flares in the framework of magnetic reconnection

    NASA Astrophysics Data System (ADS)

    Mann, G.; Warmuth, A.

    2011-04-01

    Context. Among other things, solar flares are accompanied by the production of energetic electrons as seen in the nonthermal radio and X-ray radiation of the Sun. Observations of the RHESSI satellite show that 1032-1036 nonthermal electrons are produced per second during flares. They are related to an energy flux in the range 1018-1022 W. These electrons play an important role, since they carry a substantial part of the energy released during a flare. Aims: In which way so many electrons are accelerated up to high energies during a fraction of a second is still an open question. By means of radio and hard X-ray data, we investigate under which conditions this acceleration happens in the corona. Methods: The flare is considered in the framework of magnetic reconnection. The conditions in the acceleration region in the corona are deduced by using the conservation of the total electron number and energy. Results: In the inflow region of the magnetic reconnection site, there are typical electron number densities of about 2.07 × 109 cm-3 and magnetic fields of about 46 G. These are regions with high Alfvén speeds of about 2200 km s-1. Then, sufficient energetic electrons (as required by the RHESSI observations) are only generated if the plasma inflow towards the reconnection site has Alfvén-Mach numbers in the range 0.1-1, which can lead to a super-Alfvénic outflow with speeds up to 3100 km s-1.

  20. On the Origin of Pulsations of Sub-THz Emission from Solar Flares

    NASA Astrophysics Data System (ADS)

    Zaitsev, V. V.; Stepanov, A. V.; Kaufmann, P.

    2014-08-01

    We propose a model to explain fast pulsations in sub-THz emission from solar flares. The model is based on the approach of a flaring loop as an equivalent electric circuit and explains the pulse-repetition rate, the high-quality factor, Q?103, low modulation depth, pulse synchronism at different frequencies, and the dependence of the pulse-repetition rate on the emission flux, observed by Kaufmann et al. ( Astrophys. J. 697, 420, 2009). We solved the nonlinear equation for electric current oscillations using a Van der Pol method and found the steady-state value for the amplitude of the current oscillations. Using the pulse rate variation during the flare on 4 November 2003, we found a decrease of the electric current from 1.7×1012 A in the flare maximum to 4×1010 A just after the burst. Our model is consistent with the plasma mechanism of sub-THz emission suggested recently by Zaitsev, Stepanov, and Melnikov ( Astron. Lett. 39, 650, 2013).

  1. 44How Common are X-Class Solar Flares? CY J F M A M J J A S O N D

    E-print Network

    the premature re-entry of satellites into the atmosphere. The table above lists the number of X-class flares on the solar surface. They can cause short-wave radio interference, satellite malfunctions and can even cause. About how many X-class flares would you predict for this year using the tabulated flares from

  2. Modeling atmospheric effects of the September 1859 solar flare

    Microsoft Academic Search

    B. C. Thomas; C. H. Jackman; A. L. Melott

    2007-01-01

    We have modeled atmospheric effects, especially ozone depletion, due to a solar proton event which probably accompanied the extreme magnetic storm of 1–2 September 1859. We use an inferred proton fluence for this event as estimated from nitrate levels in Greenland ice cores. We present results showing production of odd nitrogen compounds and their impact on ozone. We also compute

  3. Langmuir turbulence effects on electron beam precipitation in solar flares

    Microsoft Academic Search

    Taras Siversky; Valentina Zharkova

    2010-01-01

    We study the evolution of an electron beam injected into the solar atmosphere taking into account Langmuir wave turbulence generated by the beam of electrons. We investigate possible spatial and time scales of the Langmuir turbulence generation for different energies of particles, beam parameters and mechanisms of energy losses.

  4. Collisional relaxation of electrons in a warm plasma and accelerated nonthermal electron spectra in solar flares

    E-print Network

    Kontar, E P; Emslie, A G; Bian, N H

    2015-01-01

    Extending previous studies of nonthermal electron transport in solar flares which include the effects of collisional energy diffusion and thermalization of fast electrons, we present an analytic method to infer more accurate estimates of the accelerated electron spectrum in solar flares from observations of the hard X-ray spectrum. Unlike for the standard cold-target model, the spatial characteristics of the flaring region, especially the necessity to consider a finite volume of hot plasma in the source, need to be taken into account in order to correctly obtain the injected electron spectrum from the source-integrated electron flux spectrum (a quantity straightforwardly obtained from hard X-ray observations). We show that, for a given source-integrated electron flux spectrum, the overall power in the injected electrons could be reduced by an order of magnitude or more relative to its cold-target value. Indeed, the extent of electron thermalization can be significant enough to nullify the need to introduce an...

  5. Imaging and Spectroscopic Observations of Magnetic Reconnection and Chromospheric Evaporation in a Solar Flare

    NASA Astrophysics Data System (ADS)

    Tian, Hui; Li, Gang; Reeves, Katharine K.; Raymond, John C.; Guo, Fan; Liu, Wei; Chen, Bin; Murphy, Nicholas A.

    2014-12-01

    Magnetic reconnection is believed to be the dominant energy release mechanism in solar flares. The standard flare model predicts both downward and upward outflow plasmas with speeds close to the coronal Alfvén speed. Yet, spectroscopic observations of such outflows, especially the downflows, are extremely rare. With observations of the newly launched Interface Region Imaging Spectrograph (IRIS), we report the detection of a greatly redshifted (~125 km s-1 along the line of sight) Fe XXI 1354.08 Å emission line with a ~100 km s-1 nonthermal width at the reconnection site of a flare. The redshifted Fe XXI feature coincides spatially with the loop-top X-ray source observed by RHESSI. We interpret this large redshift as the signature of downward-moving reconnection outflow/hot retracting loops. Imaging observations from both IRIS and the Atmospheric Imaging Assembly (AIA) on board the Solar Dynamics Observatory also reveal the eruption and reconnection processes. Fast downward-propagating blobs along these loops are also found from cool emission lines (e.g., Si IV, O IV, C II, Mg II) and images of AIA and IRIS. Furthermore, the entire Fe XXI line is blueshifted by ~260 km s-1 at the loop footpoints, where the cool lines mentioned above all exhibit obvious redshift, a result that is consistent with the scenario of chromospheric evaporation induced by downward-propagating nonthermal electrons from the reconnection site.

  6. The influence of the energy emitted by solar flare soft X-ray bursts on the propagation of their associated interplanetary shock waves

    NASA Technical Reports Server (NTRS)

    Pinter, S.; Dryer, M.

    1985-01-01

    The relationship between the thermal energy released from 29 solar flares and the propagation features of their associated interplanetary shock waves that were detected at 1 AU is investigated. The 29 interplanetary shock waves were identified unambiguously and their tracking from each solar flare was deduced by tracking their associated interplanetary type-II radio emission. The thermal energy released in the solar flares was estimated from the time-intensity profiles of 1-8 A soft X-ray bursts from each flare. A good relationship is found between the flares' thermal energy with the IP shock-waves' transient velocity and arrival time at the earth - that is, the largest flare energy released is associated with the faster shock waves. Finally, a possible scenario of formation of a shock wave during the early phase of the flare and its propagation features is discussed.

  7. Solar Flare Composition and Thermodynamics from RESIK X-Ray Spectra

    NASA Astrophysics Data System (ADS)

    Sylwester, B.; Sylwester, J.; Phillips, K. J. H.; K?pa, A.; Mrozek, T.

    2014-06-01

    Previous estimates of the solar flare abundances of Si, S, Cl, Ar, and K from the RESIK X-ray crystal spectrometer on board the CORONAS-F spacecraft were made on the assumption of isothermal X-ray emission. We investigate the effect on these estimates by relaxing this assumption and instead determining the differential emission measure (DEM) or thermal structure of the emitting plasma by re-analyzing RESIK data for a GOES class M1.0 flare on 2002 November 14 (SOL2002-11-14T22:26) for which there was good data coverage. The analysis method uses a maximum-likelihood (Withbroe-Sylwester) routine for evaluating the DEM. In a first step, called here AbuOpt, an optimized set of abundances of Si, S, Ar, and K is found that is consistent with the observed spectra. With these abundances, the DEM evolution during the flare is found. The abundance optimization leads to revised abundances of silicon and sulfur in the flare plasma: A(S) = 6.94 ± 0.06 and A(Si) = 7.56 ± 0.08 (on a logarithmic scale with A(H) = 12). Previously determined abundances of Ar, K, and Cl from an isothermal assumption are still the preferred values. During the flare's maximum phase, the X-ray-emitting plasma has a basically two-temperature structure, with the cooler plasma with approximately constant temperature (3-6 MK) and a hotter plasma with temperature 16-21 MK. Using imaging data from the RHESSI hard X-ray spacecraft, the emission volume of the hot plasma is deduced from which lower limits of the electron density Ne and the thermal content of the plasma are given.

  8. Hydrogen Balmer Continuum in Solar Flares Detected by the Interface Region Imaging Spectrograph (IRIS)

    NASA Astrophysics Data System (ADS)

    Heinzel, P.; Kleint, L.

    2014-10-01

    We present a novel observation of the white light flare (WLF) continuum, which was significantly enhanced during the X1 flare on 2014 March 29 (SOL2014-03-29T17:48). Data from the Interface Region Imaging Spectrograph (IRIS) in its near-UV channel show that at the peak of the continuum enhancement, the contrast at the quasi-continuum window above 2813 Å reached 100%-200% and can be even larger closer to Mg II lines. This is fully consistent with the hydrogen recombination Balmer-continuum emission, which follows an impulsive thermal and non-thermal ionization caused by the precipitation of electron beams through the chromosphere. However, a less probable photospheric continuum enhancement cannot be excluded. The light curves of the Balmer continuum have an impulsive character with a gradual fading, similar to those detected recently in the optical region on the Solar Optical Telescope on board Hinode. This observation represents a first Balmer-continuum detection from space far beyond the Balmer limit (3646 Å), eliminating seeing effects known to complicate the WLF detection. Moreover, we use a spectral window so far unexplored for flare studies, which provides the potential to study the Balmer continuum, as well as many metallic lines appearing in emission during flares. Combined with future ground-based observations of the continuum near the Balmer limit, we will be able to disentangle various scenarios of the WLF origin. IRIS observations also provide a critical quantitative measure of the energy radiated in the Balmer continuum, which constrains various models of the energy transport and deposit during flares.

  9. Modeling atmospheric effects of the September 1859 Solar Flare

    E-print Network

    Thomas, B; Melott, A; Thomas, Brian; Jackman, Charles; Melott, Adrian

    2006-01-01

    We have modeled atmospheric effects, especially ozone depletion, due to a solar proton event which probably accompanied the extreme magnetic storm of 1-2 September 1859. We use an inferred proton fluence for this event as estimated from nitrate levels in Greenland ice cores. We present results showing production of odd nitrogen compounds and their impact on ozone. We also compute rainout of nitrate in our model and compare to values from ice core data.

  10. Modeling atmospheric effects of the September 1859 Solar Flare

    E-print Network

    Brian Thomas; Charles Jackman; Adrian Melott

    2007-02-24

    We have modeled atmospheric effects, especially ozone depletion, due to a solar proton event which probably accompanied the extreme magnetic storm of 1-2 September 1859. We use an inferred proton fluence for this event as estimated from nitrate levels in Greenland ice cores. We present results showing production of odd nitrogen compounds and their impact on ozone. We also compute rainout of nitrate in our model and compare to values from ice core data.

  11. Rocket spectrogram of a solar flare in the 10-100 A region

    NASA Technical Reports Server (NTRS)

    Acton, L. W.; Bruner, M. E.; Brown, W. A.; Fawcett, B. C.; Schweizer, W.; Speer, R. J.

    1985-01-01

    The soft (10-100 A) X-ray spectrum of an M-class solar flare was observed with a high-resolution (0.02 A) rocket-borne spectrograph on 1982 July 13. The spectrum samples an area of 600/sq arcsec on the sun, centered on or near the brightest X-ray feature of the flare. Several hundred emission lines characteristic of temperatures from about 0.5 to 7 x 10 to the 6th K have been photographically recorded. All but three of the stronger lines have been identified. It is argued that previous identification of the line at 17.62 A as iron Ly-alpha is incorrect. Spectral lines from nickel, iron, chromium, calcium, sulphur, silicon, aluminium, magnesium, neon, oxygen, nitrogen, and carbon are tabulated and discussed with extensive reference to earlier work. Absolute line intensities are given and the calibration of the telescope-spectrograph is discussed.

  12. Radio pulsations associated with the solar flare of 1982 April 14

    NASA Astrophysics Data System (ADS)

    Pant, P.; Bondal, K. R.

    1984-09-01

    H-alpha observations of the complex class-2B solar flare of April 14, 1982, obtained in 4-msec exposures with a 70-pm passband Halle filter on a 15-cm f/15 refractor at Uttar Pradesh State Observatory are presented graphically and analyzed. Dynamic spectra of the associated radio event measured at Culgoora and flux-time profiles of the microwave bursts from Toyokawa Observatory are shown for comparison. Radio pulsation, type IV continuum, type III burst storms, and soft-X-ray emissions are found to precede the H-alpha event, which is characterized by formation of two ribbons, the release of streams of nonthermal electrons from kernels, and inward electron flow producing remote brightenings at a distance of about 100,000 km by interaction with lower chromospheric layers during the declining phase of the flare.

  13. The impulsive phase of solar flares. II - Characteristics of the hard X-rays

    NASA Technical Reports Server (NTRS)

    Leach, J.; Petrosian, V.

    1983-01-01

    The results of an investigation into the electron distribution in the general non-thermal models of solar flares were used to calculate the characteristics of the impulsive hard X-rays. The height distribution, the spectrum, the polarization, and directivity of the X-rays were observed and how these X-ray characteristics are affected by the parameters defining the model was investigated. An expression is obtained for the X-ray intensity as a function of source height which is an excellent fit under certain constraints. Some available data with spatial resolution are examined and it is shown that it is possible to reproduce these data adequately with the non-thermal model and to determine the values of the parameters describing the flares. Previously announced in STAR as N82-34328

  14. Impact polarization as a diagnostic for non-thermal particles in solar flares

    NASA Astrophysics Data System (ADS)

    Vogt, E.; Sahal-Bréchot, S.; Hénoux, J.-C.

    2002-03-01

    Observations of linear polarization of lines (mainly H?) during solar flares have been reported. The orientation (predominantly radial) and magnitude of the H? polarization (about 5%) suggest an interpretation as impact polarization by low energy (<200 keV) non-thermal protons, which are not accessible by more direct diagnostic observations, such as hard X-rays (for non-thermal electrons) or gamma-ray lines (for high energy protons, above a few MeV) which will be observed by the HESSI spacecraft, soon to be launched by NASA. Impact polarization observations could thus provide useful complementary data for the study of accelerated particles in flares. However, observations in a single line such as H? can give at best an order of magnitude estimate of the accelerated protons number flux, so multiline polarimetric observations, as can be done by the franco-italian THEMIS telescope, are highly desirable.

  15. The impulsive phase of solar flares. 2: Characteristics of the hard X-rays

    NASA Technical Reports Server (NTRS)

    Leach, J.; Petrosian, V.

    1982-01-01

    The results of an investigation into the electron distribution in the general non-thermal models of solar flares were used to calculate the characteristics of the impulsive hard X-rays. The height distribution, the spectrum, the polarization, and directivity of the X-rays were observed and how these X-ray characteristics are affected by the parameters defining the model was investigated. An expression is obtained for the X-ray intensity as a function of source height which is an excellent fit under certain constraints. Some available data with spatial resolution are examined and it is shown that it is possible to reproduce these data adequately with the non-thermal model and to determine the values of the parameters describing the flares.

  16. Relative timing of electron acceleration and injection at solar flares: A case study

    NASA Astrophysics Data System (ADS)

    Claßen, H. T.; Mann, G.; Klassen, A.; Aurass, H.

    2003-10-01

    Multiple-wavelength observations of a C-class solar flare and in situ measurements of high-energy electrons at 1 AU are combined for a detailed analysis of the relative timing of solar electromagnetic emission and high-energy electron injection. The primary energy release for the C8.0 flare on 2002 June 02 (10:05-10:30 UT) is studied using hard X-ray data of the Reuven Ramaty High Energy Solar Spectroscopic Imager (RHESSI). The propagation of disturbances through the solar corona and interplanetary space is investigated by means of dynamic radio spectra obtained by ground-based observatories (Ond?ejov, Czech Republic, and Potsdam, Germany). The time sequence of these indirect manifestations of highly energetic electrons is correlated with the extrapolated injection time obtained by a transit time analysis from Sun to Earth using the enhancement in the 27-182 keV electron intensity observed at the Wind spacecraft. This back-mapping of high-energy electrons shows that the particles are injected roughly 18 min after the first hard X-ray maximum. Almost at the same time there are observations of metric type II and IV radio bursts indicating the presence of a coronal shock wave and a moving plasmoid whose kinematics are analysed by means of dynamic radio spectra and radio images from the Nançay Radioheliograph (France). Implications for possible acceleration and injection scenarios are discussed.

  17. Coherent-phase or random-phase acceleration of electron beams in solar flares

    NASA Technical Reports Server (NTRS)

    Aschwanden, Markus J.; Benz, Arnold O.; Montello, Maria L.

    1994-01-01

    Time structures of electron beam signatures at radio wavelengths are investigated to probe correlated versus random behavior in solar flares. In particular we address the issue whether acceleration and injection of electron beams is coherently modulated by a single source, or whether the injection is driven by a stochastic (possibly spatially fragmented) process. We analyze a total of approximately = 6000 type III bursts observed by Ikarus (Zurich) in the frequency range of 100-500 MHz, during 359 solar flares with simultaneous greater than or = 25 keV hard X-ray emission, in the years 1890-1983. In 155 flares we find a total of 260 continuous type III groups, with an average number of 13 +/- 9 bursts per group, a mean duration of D = 12 +/- 14 s, a mean period of P = 2.0 +/- 1.2 s, with the highest burst rate at a frequency of nu = 310 +/- 120 MHz. Pulse periods have been measured between 0.5 and 10 s, and can be described by an exponential distribution, i.e., N(P) varies as e (exp -P/1.0s). The period shows a frequency dependence of P(nu)=46(exp-0.6)(sub MHz)s for different flares, but is invariant during a particular flare. We measure the mean period P and its standard deviation sigma (sub p) in each type III group, and quantify the degree of periodicity (or phase-coherence) by the dimensionless parameter sigma (sub p)P. The representative sample of 260 type III burst groups shows a mean periodicity of sigma (sub p/P) = 0.37 +/- 0.12, while Monte Carlo simulations of an equivalent set of truly random time series show a distinctly different value of sigma (sub p)P = 0.93 +/- 0.26. This result indicates that the injection of electron beams is coherently modulated by a particle acceleration source which is either compact or has a global organization on a timescale of seconds, in contrast to an incoherent acceleration source, which is stochastic either in time or space. We discuss the constraints on the size of the acceleration region resulting from electron beam propagation delays and from Alfvenic synchronization during a pulse period. We discuss two periodic preocesses in flares, which potentially control quasi-periodic particle acceleration: (1) MHD oscillations, and (2) current sheets with oscillatory dynamics.

  18. Search of Continuum Solar Flare Radiation from GHz to THz Frequencies

    NASA Astrophysics Data System (ADS)

    Kaufmann, P.; Correia, E.; Giménez de Castro, C.; Hurford, G.; Lin, R. P.; Makhmutov, V. S.; Marcon, R.; Marun, A.; Raulin, J.-P.; Shih, A. Y.; Stozhkov, Y. I.; Válio, A.; Villela, T.

    2011-05-01

    The new solar burst emission spectral component showing sub-THz fluxes increasing with frequency, spectrally separated from the well known microwave component, brings serious constraints for interpretation. The knowledge of THz continuum spectral shape is essential to investigate the nature of the emission mechanisms involved. New 45 and 90 GHz solar polarimeters are being installed at El Leoncito high altitude observatory, where sub-THz (0.2 and 0.4 THz) solar flare flux data are being obtained regularly since several years. The development of THz photometers for continuum requires solutions for several technical challenges. To avoid atmospheric attenuation the THz solar observations should be carried in space or at selected frequency windows on exceptionally high sites near the South Pole. A double THz solar photometer system has been developed to operate at center frequencies of 3 and 7 THz. Golay cell sensors are used, preceded by a low pass membrane filter (f < 15 THz), resonant metal mesh band-pass filters with center frequencies at 3 and 7 THz (± 10% bandwidth), and a tuning fork resonant chopper. The incoming solar signal is collected by 75 mm diameter Cassegrain telescopes which reflectors’ surfaces are roughened in order to diffuse most of the visible and near IR thermal radiation. Brazil funding agency FAPESP has recently approved the construction of the dual THz frequency photometer system to be flown in a long duration stratospheric balloon flight in Antarctica (two weeks circumnavigation) in cooperation with University of California, Berkeley, together with GRIPS (Gamma-Ray Imaging Polarimeter for solar flares) experiment. One test flight is planned for 2012. USA. Another balloon flight over Russia (one week) is considered between 2014-2016, in a cooperation with Moscow Lebedev Physics Institute.

  19. Energy of microwave-emitting electrons and hard X-ray\\/microwave source model in solar flares

    Microsoft Academic Search

    Nariaki Nitta; Takeo Kosugi

    1986-01-01

    We present a new method of estimating the energy of microwave-emitting electrons from the observed rate of increase of the microwave flux relative to the hard X-ray flux measured at various energies during the rising phase of solar flares. A total of 22 flares observed simultaneously in hard X-rays (20–400 keV) and in microwaves (17 GHz) were analyzed in this

  20. Effect of Solar Flare Index (If) on seasonal Rainfall variation over Gangetic West Bengal

    NASA Astrophysics Data System (ADS)

    Saha, Rajdeep

    It is well established that Sun is the source of all energy on the Earth and it controls many of tropospheric, stratospheric and ionospheric phenomenons. There are many solar parameters which are responsible for affecting the atmosphere. Among all parameters If index, defined by the Scientist Sawyer in the year 1967, has been taken into consideration. There are already so many work which has been established in the field of ionosphere with the If index and it is believed that there may be some correlation found between the tropospheric phenomenon and this solar If index. Therefore, this might be the first step taken to describe the findings of a correlation between the If index in the Troposphere with the monthly precipitation mainly in monsoon period along with three other different seasons as mentioned by the Indian Meteorological Department during a period of 22 year solar cycle in the year 1989 to 2010 over Gangetic West Bengal. As it is already known that the seasonal rainfall variation mainly depend on some predominating factor like inclination angle of the Earth, the perigee and apogee position of the earth with respect to the sun. Besides this, many world tropospheric phenomenons like EL NINO, Sea surface temperature variation, Southern Oscillation Index, high pressure over Tibetan plateau are directly or indirectly controlled by the Sun and these phenomenons also affects the monsoonal climate over Indian subcontinent. Here it is being found out a relation between the solar flare If index and the precipitation amount over Gangetic West Bengal and ultimately the symmetrical relationship in between these two parameter is seen. Since If index depends on the disc area which has been created at the time of solar flare. There are many solar parameters which have different periodic variation, therefore, it can be said that the disc area may be a periodically changed variable of Sun and it is a time dependent factor. During this small interval of time it is very difficult to find out a periodic change of this disc area and find out a correlation between the If index and precipitation over this area. But in this work it is concluded that the monthly precipitation amount over Gangetic West Bengal and the solar flare If index follows the same trend throughout all the seasons during the 22 year solar cycle having a period from 1989 to 2010.

  1. Radio evidence for a delayed acceleration process in solar flares

    NASA Technical Reports Server (NTRS)

    Kai, K.; Nakajima, H.; Kosugi, T.; Stewart, R. T.; Nelson, G. J.

    1986-01-01

    Observations of six delayed solar radio bursts at dm and mm frequencies are analyzed. The events included five Type II bursts. The data comprise 17 GHz interferometer data and ISEE-3 and SMM hard X-ray spectrometry data which peaked 0.5-1.0 hr after the main radio bursts. The data indicate the electrons with energies in the MeV range continue to be excited for tens of minutes after the impulsive phase acceleration. The continuing acceleration occurs in a large magnetic structure extending to at least 200,000 km altitude. The radio signals arise from a columnar source, the microwave signals being emitted near a leg or legs and meterwave emissions originating from the top of the magnetic structure.

  2. Simulations of the Solar Atmospheric Response to Flare-Accelerated Ion Beams

    NASA Astrophysics Data System (ADS)

    Allred, Joel C.

    2013-07-01

    We present models of the solar atmospheric response to heating from a beam of flare-accelerated ions. The ions heat the atmosphere through Coulomb collisions which we model by solving a Fokker-Planck kinetic equation. This method models how relativistic ions propagate through the solar atmosphere and includes the effects of pitch-angle scattering through Coulomb collisions, synchrotron emission and magnetic mirroring in a multi-species, partially-ionized plasma. We have performed simulations for a wide variety of injected ion beam energy spectra including those predicted from stochastic acceleration models. The atmospheric response is modeling by solving the radiative hydrodynamic equations in 1D using the RADYN code. This code solves the radiative transfer equation for non-LTE, non-equilibrium optically-thick transitions which dominate in the chromosphere allowing direct comparisons with observed transition profiles. We compare our predicted values for plasma velocities, emission measures, and temperature structure with observations of solar flares from the RHESSI, SDO, and Hinode observatories.

  3. Solar X-ray physics

    SciTech Connect

    Bornmann, P.L. (USAF, Geophysics Laboratory, Hanscom AFB, MA (United States))

    1991-01-01

    Research on solar X-ray phenomena performed by American scientists during 1987-1990 is reviewed. Major topics discussed include solar images observed during quiescent times, the processes observed during solar flares, and the coronal, interplanetary, and terrestrial phenomena associated with solar X-ray flares. Particular attention is given to the hard X-ray emission observed at the start of the flare, the energy transfer to the soft X-ray emitting plasma, the late resolution of the flare as observed in soft X-ray, and the rate of occurrence of solar flares as a function of time and latitude. Pertinent aspects of nonflaring, coronal X-ray emission and stellar flares are also discussed. 175 refs.

  4. Wavelength Dependence of Solar Irradiance Enhancement During X-Class Flares and Its Influence on the Upper Atmosphere

    NASA Technical Reports Server (NTRS)

    Huang, Yanshi; Richmond, Arthur D.; Deng, Yue; Chamberlin, Phillip C.; Qian, Liying; Solomon, Stanley C.; Roble, Raymond G.; Xiao, Zuo

    2013-01-01

    The wavelength dependence of solar irradiance enhancement during flare events is one of the important factors in determining how the Thermosphere-Ionosphere (T-I) system responds to flares. To investigate the wavelength dependence of flare enhancement, the Flare Irradiance Spectral Model (FISM) was run for 61 X-class flares. The absolute and the percentage increases of solar irradiance at flare peaks, compared to pre-flare conditions, have clear wavelength dependences. The 0-14 nm irradiance increases much more (approx. 680% on average) than that in the 14-25 nm waveband (approx. 65% on average), except at 24 nm (approx. 220%). The average percentage increases for the 25-105 nm and 122-190 nm wavebands are approx. 120% and approx. 35%, respectively. The influence of 6 different wavebands (0-14 nm, 14-25 nm, 25-105 nm, 105- 120 nm, 121.56 nm, and 122-175 nm) on the thermosphere was examined for the October 28th, 2003 flare (X17-class) event by coupling FISM with the National Center for Atmospheric Research (NCAR) Thermosphere-Ionosphere-Electrodynamics General Circulation Model (TIE-GCM) under geomagnetically quiet conditions (Kp=1). While the enhancement in the 0-14 nm waveband caused the largest enhancement of the globally integrated solar heating, the impact of solar irradiance enhancement on the thermosphere at 400 km is largest for the 25-105 nm waveband (EUV), which accounts for about 33 K of the total 45 K temperature enhancement, and approx. 7.4% of the total approx. 11.5% neutral density enhancement. The effect of 122-175 nm flare radiation on the thermosphere is rather small. The study also illustrates that the high-altitude thermospheric response to the flare radiation at 0-175 nm is almost a linear combination of the responses to the individual wavebands. The upper thermospheric temperature and density enhancements peaked 3-5 h after the maximum flare radiation.

  5. Wavelength Dependence of Solar Irradiance Enhancement During X-class Flares and Its Influence on the Upper Atmosphere

    NASA Technical Reports Server (NTRS)

    Huang, Yanshi; Richmond, A. D.

    2013-01-01

    The wavelength dependence of solar irradiance enhancement during flare events is one of the important factors in determining how the Thermosphere-Ionosphere (TI) system responds to flares. To investigate the wavelength dependence of flare enhancement, the Flare Irradiance Spectral Model (FISM) was run for 61X-class flares. The absolute and the percentage increases of solar irradiance at flare peaks, compared to pre-flare conditions, have clear wavelength dependences. The 0-4 nm irradiance increases much more ((is) approximately 680 on average) than that in the 14-25 nm waveband ((is) approximately 65 on average), except at 24 nm ( (is) approximately 220). The average percentage increases for the 25-105 nm and 122-190 nm wave bands are approximately 120 and approximately 35, respectively. The influence of 6 different wavebands (0-14 nm, 14-25 nm, 25-105 nm, 105-120 nm, 121.56 nm,and122-175 nm) on the thermosphere was examined for the October 28th, 2003 flare (X17-class) event by coupling FISM with the National Center for Atmospheric Research (NCAR) Thermosphere-Ionosphere-Electrodynamics General Circulation Model(TIE-GCM) under geomagnetically quiet conditions (Kp=1). While the enhancement in the0-14nm waveband caused the largest enhancement of the globally integrated solar heating, the impact of solar irradiance enhancement on the thermosphere at 400 km is largest for the 25-105 nm waveband (EUV), which accounts for about 33 K of the total 45 K temperature enhancement, and approximately 7.4% of the total approximately 11.5% neutral density enhancement. The effect of 122-175 nm flare radiation on the thermosphere is rather small. The study also illustrates that the high-altitude thermospheric response to the flare radiation at 0-175 nm is almost a linear combination of the responses to the individual wavebands. The upper thermospheric temperature and density enhancements peaked 3-5 h after the maximum flare radiation.

  6. Particle acceleration by slow modes in strong compressible MHD turbulence, with application to solar flares

    E-print Network

    Chandran, B D G

    2003-01-01

    Energetic particles that undergo strong pitch-angle scattering and diffuse through a plasma containing strong compressible MHD turbulence undergo diffusion in momentum space with diffusion coefficient Dp. In this paper, the contribution of slow modes to Dp is calculated assuming the rms turbulent velocity is of order the Alfven speed. The energy spectrum of accelerated particles is derived assuming slow modes make the dominant contribution to Dp, taking into account Coulomb losses and particle escape from the acceleration region with an energy-independent escape time. The results are applied to solar flares.

  7. Particle acceleration by slow modes in strong compressible MHD turbulence, with application to solar flares

    E-print Network

    Benjamin D. G. Chandran

    2003-11-13

    Energetic particles that undergo strong pitch-angle scattering and diffuse through a plasma containing strong compressible MHD turbulence undergo diffusion in momentum space with diffusion coefficient Dp. In this paper, the contribution of slow modes to Dp is calculated assuming the rms turbulent velocity is of order the Alfven speed. The energy spectrum of accelerated particles is derived assuming slow modes make the dominant contribution to Dp, taking into account Coulomb losses and particle escape from the acceleration region with an energy-independent escape time. The results are applied to solar flares.

  8. On the importance of reverse current ohmic losses in electron-heated solar flare atmospheres

    NASA Technical Reports Server (NTRS)

    Emslie, A. G.

    1980-01-01

    The passage of a beam of nonthermal electrons through the flaring solar atmosphere is considered, paying particular attention to the requirement that the beam be stable to the generation of plasma turbulence. The ratio is computed of energy losses due to reverse current ohmic heating, and heating by Coulomb collisions, respectively, for the greatest flux which can pass stably through the atmosphere. It is demonstrated that this ratio is determined by the low energy cutoff of the beam, by the electron temperature of the ambient atmosphere, and by the electron to ion temperature ratio. It is also independent of the atmospheric density.

  9. MODELING OF GYROSYNCHROTRON RADIO EMISSION PULSATIONS PRODUCED BY MAGNETOHYDRODYNAMIC LOOP OSCILLATIONS IN SOLAR FLARES

    SciTech Connect

    Mossessian, George; Fleishman, Gregory D. [Center For Solar-Terrestrial Research, New Jersey Institute of Technology, Newark, NJ 07102 (United States)

    2012-04-01

    A quantitative study of the observable radio signatures of the sausage, kink, and torsional magnetohydrodynamic (MHD) oscillation modes in flaring coronal loops is performed. Considering first non-zero order effect of these various MHD oscillation modes on the radio source parameters such as magnetic field, line of sight, plasma density and temperature, electron distribution function, and the source dimensions, we compute time-dependent radio emission (spectra and light curves). The radio light curves (of both flux density and degree of polarization) at all considered radio frequencies are then quantified in both time domain (via computation of the full modulation amplitude as a function of frequency) and in Fourier domain (oscillation spectra, phases, and partial modulation amplitude) to form the signatures specific to a particular oscillation mode and/or source parameter regime. We found that the parameter regime and the involved MHD mode can indeed be distinguished using the quantitative measures derived in the modeling. We apply the developed approach to analyze radio burst recorded by Owens Valley Solar Array and report possible detection of the sausage mode oscillation in one (partly occulted) flare and kink or torsional oscillations in another flare.

  10. Comparative Analysis of Non-thermal Emissions and Study of Electron Transport in a Solar Flare

    E-print Network

    T. Minoshima; T. Yokoyama; N. Mitani

    2007-10-02

    We study the non-thermal emissions in a solar flare occurring on 2003 May 29 by using RHESSI hard X-ray (HXR) and Nobeyama microwave observations. This flare shows several typical behaviors of the HXR and microwave emissions: time delay of microwave peaks relative to HXR peaks, loop-top microwave and footpoint HXR sources, and a harder electron energy distribution inferred from the microwave spectrum than from the HXR spectrum. In addition, we found that the time profile of the spectral index of the higher-energy ($\\gsim 100$ keV) HXRs is similar to that of the microwaves, and is delayed from that of the lower-energy ($\\lsim 100$ keV) HXRs. We interpret these observations in terms of an electron transport model called {\\TPP}. We numerically solved the spatially-homogeneous {\\FP} equation to determine electron evolution in energy and pitch-angle space. By comparing the behaviors of the HXR and microwave emissions predicted by the model with the observations, we discuss the pitch-angle distribution of the electrons injected into the flare site. We found that the observed spectral variations can qualitatively be explained if the injected electrons have a pitch-angle distribution concentrated perpendicular to the magnetic field lines rather than isotropic distribution.

  11. EVOLUTION OF CURRENTS OF OPPOSITE SIGNS IN THE FLARE-PRODUCTIVE SOLAR ACTIVE REGION NOAA 10930

    SciTech Connect

    Ravindra, B. [Indian Institute of Astrophysics, Koramangala, Bangalore 560 034 (India); Venkatakrishnan, P.; Tiwari, Sanjiv Kumar; Bhattacharyya, R., E-mail: ravindra@iiap.res.in, E-mail: pvk@prl.res.in, E-mail: tiwari@mps.mpg.de, E-mail: ramit@prl.res.in [Udaipur Solar Observatory, Physical Research Laboratory, Dewali, Bari Road, Udaipur 313 001 (India)

    2011-10-10

    Analysis of a time series of high spatial resolution vector magnetograms of the active region NOAA 10930 available from the Solar Optical Telescope SpectroPolarimeter on board Hinode revealed that there is a mixture of upward and downward currents in the two footpoints of an emerging flux rope. The flux emergence rate is almost the same in both the polarities. We observe that along with an increase in magnetic flux, the net current in each polarity increases initially for about three days after which it decreases. This net current is characterized by having exactly opposite signs in each polarity while its magnitude remains almost the same most of the time. The decrease of the net current in both the polarities is due to the increase of current having a sign opposite to that of the net current. The dominant current, with the same sign as the net current, is seen to increase first and then decreases during the major X-class flares. Evolution of non-dominant current appears to be a necessary condition for flare initiation. The above observations can be plausibly explained in terms of the superposition of two different force-free states resulting in a non-zero Lorentz force in the corona. This Lorentz force then pushes the coronal plasma and might facilitate the magnetic reconnection required for flares. Also, the evolution of the net current is found to follow the evolution of magnetic shear at the polarity inversion line.

  12. A Simple Model of Chromospheric Evaporation and Condensation Driven Conductively in a Solar Flare

    NASA Astrophysics Data System (ADS)

    Longcope, D. W.

    2014-11-01

    Magnetic energy released in the corona by solar flares reaches the chromosphere where it drives characteristic upflows and downflows known as evaporation and condensation. These flows are studied here for the case where energy is transported to the chromosphere by thermal conduction. An analytic model is used to develop relations by which the density and velocity of each flow can be predicted from coronal parameters including the flare's energy flux F. These relations are explored and refined using a series of numerical investigations in which the transition region (TR) is represented by a simplified density jump. The maximum evaporation velocity, for example, is well approximated by ve ~= 0.38(F/?co, 0)1/3, where ?co, 0 is the mass density of the pre-flare corona. This and the other relations are found to fit simulations using more realistic models of the TR both performed in this work, and taken from a variety of previously published investigations. These relations offer a novel and efficient means of simulating coronal reconnection without neglecting entirely the effects of evaporation.

  13. Relationship between hard X-ray and EUV sources in solar flares

    NASA Technical Reports Server (NTRS)

    Kane, S. R.; Frost, K. J.; Donnelly, R. F.

    1979-01-01

    The high time resolution hard X-ray (not less than 15 keV) observations of medium and large impulsive solar flares made with the OSO 5 satellite are compared with the simultaneous ground-based observations of 10-1030 A EUV flux made via sudden frequency deviations (SFD) at Boulder. For most flares the agreement between the times of maxima of the impulsive hard X-ray and EUV emissions is found to be consistent with earlier studies (not less than 1 s). The rise and decay times of the EUV emission are larger than the corresponding times for X-rays not less than 30 keV. When OSO 5 hard X-ray measurements are combined with those made by OGO1, OGO 3, OGO 5, and TD 1A satellites, it is found that there is a nearly linear relationship between the energy fluxes of impulsive EUV emission and X-rays not less than 10 keV over a wide range of flare magnitudes. A model involving only a 'partial precipitation' of energetic electrons and consisting of both thick and thin target hard X-ray sources is examined.

  14. Interplanetary Magnetic Field Line Mixing Deduced from Impulsive Solar Flare Particles.

    PubMed

    Mazur; Mason; Dwyer; Giacalone; Jokipii; Stone

    2000-03-20

    We have studied fine-scale temporal variations in the arrival profiles of approximately 20 keV nucleon-1 to approximately 2 MeV nucleon-1 ions from impulsive solar flares using instrumentation on board the Advanced Composition Explorer spacecraft at 1 AU between 1997 November and 1999 July. The particle events often had short-timescale ( approximately 3 hr) variations in their intensity that occurred simultaneously across all energies and were generally not in coincidence with any local magnetic field or plasma signature. These features appear to be caused by the convection of magnetic flux tubes past the observer that are alternately filled and devoid of flare ions even though they had a common flare source at the Sun. Thus, we have used the particles to study the mixing of the interplanetary magnetic field that is due to random walk. We deduce an average timescale of 3.2 hr for these features, which corresponds to a length of approximately 0.03 AU. PMID:10702137

  15. Rapid soft X-ray fluctuations in solar flares observed with the X-ray polychromator

    NASA Technical Reports Server (NTRS)

    Zarro, D. M.; Saba, J. L. R.; Strong, K. T.

    1986-01-01

    Three flares observed by the Soft X-Ray Polychromator on the Solar Maximum Mission were studied. Flare light curves from the Flat Crystal Spectrometer and Bent Crystal Spectrometer were examined for rapid signal variations. Each flare was characterized by an initial fast (less than 1 min) burst, observed by the Hard X-Ray Burst Spectrometer (HXRBS), followed by softer gradual X-ray emission lasting several minutes. From an autocorrelation function analysis, evidence was found for quasi-periodic fluctuations with rise and decay times of 10 s in the Ca XIX and Fe XXV light curves. These variations were of small amplitude (less than 20%), often coincided with hard X-ray emissions, and were prominent during the onset of the gradual phase after the initial hard X-ray burst. It is speculated that these fluctuations were caused by repeated energy injections in a coronal loop that had already been heated and filled with dense plasma associated with the initial hard X-ray burst.

  16. Wave-particle interaction and peculiarities of propagation and emission of accelerated particles in solar flares

    NASA Astrophysics Data System (ADS)

    Stepanov, A. V.; Tsap, Yu. T.

    2006-08-01

    Consequences of wave-particle interaction in the propagation and emission of accelerated particles in solar flares are considered. i. Strong diffusion energetic particles on small-scale waves (Trakhtengerts 1984) gives time delays of gamma ray line emission vs hard X-ray emission when electron and protons are accelerated simultaneously. ii. Anomalous propagation of relativistic electrons along the flare loop with velocity of 30 times less compared with light velocity (Yokoyama et al 2002) is explained in terms of the collective effects of interaction of electrons with plasma turbulence. A cloud of high-energetic electrons responsible for microwave emission generates whistler waves and a turbulent "wall" in the loop is formed. The electrons undergo strong resonant scattering and the emission front propagates with the wave phase velocity, which is much lower than particle velocity. iii. Absence of linear polarization (? 0.07%) in H? emission of some flares (Bianda et al 2005) is interpreted in terms of pitch-angle scattering of proton beams on small-scale Alfven waves. References Bianda M., Benz F.O., Stenflo J.O. et al 2005, A&A, 434, 1183 Trakhtengerts V.Yu. 1984, Relaxation of Plasma with Anisotropic Velocity Distribution, in A.A.Galeev and R.N.Sudan (eds.) Basic Plasma Physics II, North-Holland Physics Publishing Yokoyama T., Nakajima H., Shibasaki K, et al. 2002, ApJ, 576, L87

  17. Modelling Magnetic Reconnection and Nano-flare Heating in the Solar Corona

    NASA Astrophysics Data System (ADS)

    Biggs, George; Asgari-Targhi, Mahboubeh

    2015-01-01

    Current models describing magnetic reconnection in the solar corona assume single reconnection events occurring at random crossings between magnetic flux tubes. However, in the avalanche model of magnetic reconnection, multiple reconnections are expected to occur. The purpose of this research is to first, calculate the point of the greatest stress between magnetic flux tubes and then to allow for dynamic evolution utilising the avalanche model. This represents a significant increase in sophistication over previous models. This undertaking is not purely theoretical since we compare the results of our modelling with HI-C data. Using key inputs from the HIC and AIA observations such as loop length and magnetic field strength, we predict the number of reconnection events likely to take place. As a single reconnection event cannot currently be directly observed, the distribution of flare events are recorded instead. The power law fit yielded as a result of our simulations is within the expected range given the observational evidence of flare distributions and temperature values in the corona. This provides further evidence to support the role of Nano-flares in the heating of the corona.

  18. Sensing the Earth's low ionosphere during solar flares using VLF signals and GOES X-ray data

    E-print Network

    Kolarski, Aleksandra

    2014-01-01

    An analysis of D-region electron density height profile variations, induced by four isolated solar X-ray flares during period from September 2005 to December 2006, based on the amplitude and the phase delay perturbation of 22.1 kHz signal trace from Skelton (54.72 N, 2.88 W) to Belgrade (44.85 N, 20.38 E), coded GQD, was carried out. Solar flare data were taken from NOAA GOES12 satellite one-minute listings. For VLF data acquisition and recordings at the Institute of Physics, Belgrade, Serbia, the AbsPAL system was used. Starting from LWPCv21 code (Ferguson, 1998), the variations of the Earth-ionosphere waveguide characteristic parameters, sharpness and reflection height, were estimated during the flare conditions. It was found that solar flare events affected the VLF wave propagation in the Earth-ionosphere waveguide by changing the lower ionosphere electron density height profile, in a different way, for different solar flare events.

  19. STUDYING THE POLARIZATION OF HARD X-RAY SOLAR FLARES WITH THE GAMMA RAY POLARIMETER EXPERIMENT (GRAPE)

    NASA Astrophysics Data System (ADS)

    Ertley, Camden

    2014-01-01

    The degree of linear polarization of hard X-rays (50-500 keV) can provide a better understanding of the particle acceleration mechanisms and the emission of radiation during solar flares. Difficulties in measuring the linear polarization has limited the ability of past experiments to place constraints on solar flare models. The Gamma RAy Polarimeter Experiment (GRAPE) is a balloon-borne Compton polarimeter designed to measure polarization in the 50 - 500 keV energy range. This energy range minimizes the thermal contamination that can potentially affect measurements at lower energies. This research focuses on the analysis of data acquired during the first high altitude balloon flight of the GRAPE payload in 2011. During this 26 hour balloon flight two M-class flares were observed. The analysis effort includes the development of a Monte Carlo simulation of the full instrument payload with the GEANT4 toolkit. The simulations were used in understanding the background environment, creating a response matrix for the deconvolution of the energy loss spectra, and determining the modulation factor for a 100% linearly polarized source. We report on the results from the polarization analysis of the solar flare data. The polarization and spectral data can be used to further our understanding of particle acceleration in the context of current solar flare models.

  20. Uncertainty Estimation in Fitting Parameterized Models to Solar Flare Hard X-ray Spectra

    NASA Astrophysics Data System (ADS)

    Ireland, Jack; Tolbert, A. K.; Holman, G. D.; Dennis, B. R.; Schwartz, R. A.

    2012-05-01

    We compare four different methods of estimating the uncertainty in fit parameters when fitting models to Ramaty High Energy Solar Spectroscopic Imager (RHESSI) spectral data. Two flare spectra are studied: one from the GOES (Geostationary Operational Environmental Satellite) X1.3 class flare of 19-January-2005, and the other from the X4.8 flare of 23-July-2002. Three of our methods rely on assumptions about the shape of the hyper-surface formed by the weighted sum of the squares of the differences between the model fit and the data as a function of the fit parameters, evaluated around the minimum value of the hyper-surface, to generate uncertainty estimates. The fourth method is based on Bayesian data analysis techniques. The four methods give approximately equal uncertainty estimates for the 19-January-2005 model parameters, but give very different uncertainty estimates for the 23-July-2002 model parameters. This is because the assumptions required for the first three methods hold approximately for the 19-January-2005 analysis, but do not hold for the 23-July-2002 analysis. The Bayesian-based method does not require these assumptions, and so can give reliable uncertainty estimates regardless of the shape of the hyper-surface formed by the model fit to the data. We show that for the 23-July-2002 spectrum, there is a 95% probability that the low energy cutoff to the model distribution of emitting flare electrons lies below approximately 40keV, and a 68% probability that it lies in the estimated range 7-36 keV. The most probable flare electron energy flux is approximately 1028.1 erg-1sec-1 with a 68% credible interval estimated at 1028.1-29.1 erg-1sec-1, and a 95% credible interval estimated at 1028.0-30.3 erg-1sec-1. For the 19-January-2005 spectrum, these quantities are more tightly constrained to 105±4 keV and 1027.66±0.01 erg-1sec-1 (68% uncertainties). The reasons for these disparate results are discussed. This work is funded by the NASA Solar and Heliospheric Physics program.

  1. Chromospheric Height and Density Measurements in a Solar Flare Observed with RHESSI II. Data Analysis

    NASA Astrophysics Data System (ADS)

    Aschwanden, Markus J.; Brown, John C.; Kontar, Eduard P.

    2002-11-01

    We present an analysis of hard X-ray imaging observations from one of the first solar flares observed with the Reuven Ramaty High-Energy Solar Spectroscopic Imager (RHESSI) spacecraft, launched on 5 February 2002. The data were obtained from the 22 February 2002, 11:06 UT flare, which occurred close to the northwest limb. Thanks to the high energy resolution of the germanium-cooled hard X-ray detectors on RHESSI we can measure the flare source positions with a high accuracy as a function of energy. Using a forward-fitting algorithm for image reconstruction, we find a systematic decrease in the altitudes of the source centroids z(?) as a function of increasing hard X-ray energy ?, as expected in the thick-target bremsstrahlung model of Brown. The altitude of hard X-ray emission as a function of photon energy ? can be characterized by a power-law function in the ?=15 50 keV energy range, viz., z(?)?2.3(?/20 keV)-1.3 Mm. Based on a purely collisional 1-D thick-target model, this height dependence can be inverted into a chromospheric density model n(z), as derived in Paper I, which follows the power-law function n e(z)=1.25×1013(z/1 Mm)-2.5 cm-3. This density is comparable with models based on optical/UV spectrometry in the chromospheric height range of h?1000 km, suggesting that the collisional thick-target model is a reasonable first approximation to hard X-ray footpoint sources. At h?1000 2500 km, the hard X-ray based density model, however, is more consistent with the `spicular extended-chromosphere model' inferred from radio sub-mm observations, than with standard models based on hydrostatic equilibrium. At coronal heights, h?2.5 12.4 Mm, the average flare loop density inferred from RHESSI is comparable with values from hydrodynamic simulations of flare chromospheric evaporation, soft X-ray, and radio-based measurements, but below the upper limits set by filling-factor insensitive iron line pairs.

  2. BLOOD PRESSURE, HEART RATE AND MELATONIN CYCLES SYNCHRONIZATION WITH THE SEASON, EARTH MAGNETISM AND SOLAR FLARES.

    PubMed

    Cornélissen, G; Halberg, F; Sothern, R B; Hillman, D C; Siegelová, J

    2010-01-01

    Three spectral components with periods of about (~) 0.41, ~0.5 and ~1.0 year had been found with serially independent sampling in human circulating melatonin. The time series consisted of around-the-clock samples collected for 24 hours at 4-hour intervals from different patients over several years. Some of these components had been found to be circadian stage-dependent, the daytime measurements following mostly a circannual variation, whereas a half-year characterized the nighttime samples. The latter were incorporated into a circasemiannual map. The relative brevity of the series prevented a check for the coexistence of all three spectral components, even if each component seemed to have a raison d'être. In time series of transdisciplinary data, a 1.00-year synchronized component is interpreted as representing the seasons. The half-year may qualify the circannual waveform, but it is also a signature of geomagnetics. An ~0.41-year (~5-month) component is the signature of solar flares. It has been called a cis-half-year (cis = on this side of a half-year) and may be detected only intermittently. Charles L. Wolff predicted the existence, among others, of ~0.42- and ~0.56-year components as beat periods of rotations at different solar latitudes.The multiple components characterizing circulating melatonin could also be found in a (to our knowledge unique) data set of a clinically healthy scientist (RBS). Herein, we focus on vascular data self-measured by RBS as he aged from ~20 to ~60 years. A multi-component model consisting of cosine curves with periods of 0.41, 0.50 and 1.00 year was fitted to weekly means of systolic (S) and diastolic (D) blood pressure (BP) and heart rate (HR) collected ~5 times a day over 39 years by RBS. All three components can coexist for a while, although all of them are nonstationary in their characteristics and come and go by the criterion of statistical significance.Intermittently, BP and HR are synchronized selectively with one or the other aspect of RBS' physical environment, namely the seasons (at ~1.0 year), earth magnetism (at ~0.5 year) and/or solar flares (at ~0.42 year). Cosmic-biotic transfer of information, albeit hardly of energy (the biospheric amplitudes are very small) may be mediated in this set of frequency windows. As found earlier, RBS' circulation is also frequency-trapped environmentally in multidecadal windows, HR being locked into the transtridecadal Brückner, or rather Brückner-Egeson-Lockyer, BEL sunspot and terrestrial weather cycle, while his BP follows Hale's didecadal cycle in the changing polarity of sunspots.The ~0.41-year HR cycle may be associated with changes in solar flares, the cis-half-year amplitude of HR showing a cross-correlation coefficient of 0.79 with the total solar flare index (from both solar hemispheres) at a lag of ~3.2 years. The superposed time courses of these two variables indicate the presence of a shared Horrebow-Arago-Schwabe sunspot cycle of ~11 years, the cis-half-year in HR being more prominent after the total solar flare index reaches its ~11-year peak. Differences in the time-varying behavior of BP vs. HR are also described. PMID:21566725

  3. ACCELERATION, MAGNETIC FLUCTUATIONS, AND CROSS-FIELD TRANSPORT OF ENERGETIC ELECTRONS IN A SOLAR FLARE LOOP

    SciTech Connect

    Kontar, E. P.; Hannah, I. G.; Bian, N. H. [School of Physics and Astronomy, University of Glasgow, G12 8QQ (United Kingdom)

    2011-04-01

    Plasma turbulence is thought to be associated with various physical processes involved in solar flares, including magnetic reconnection, particle acceleration, and transport. Using RHESSI observations and the X-ray visibility analysis, we determine the spatial and spectral distributions of energetic electrons for a flare (GOES M3.7 class, 2002 April 14, 23:55 UT), which was previously found to be consistent with a reconnection scenario. It is demonstrated that because of the high density plasma in the loop, electrons have to be continuously accelerated about the loop apex of length {approx}2 x 10{sup 9} cm and width {approx}7 x 10{sup 8} cm. Energy-dependent transport of tens of keV electrons is observed to occur both along and across the guiding magnetic field of the loop. We show that the cross-field transport is consistent with the presence of magnetic turbulence in the loop, where electrons are accelerated, and estimate the magnitude of the field line diffusion coefficient for different phases of the flare. The energy density of magnetic fluctuations is calculated for given magnetic field correlation lengths and is larger than the energy density of the non-thermal electrons. The level of magnetic fluctuations peaks when the largest number of electrons is accelerated and is below detectability or absent at the decay phase. These hard X-ray observations provide the first observational evidence that magnetic turbulence governs the evolution of energetic electrons in a dense flaring loop and is suggestive of their turbulent acceleration.

  4. Automated Solar Flare Statistics in Soft X-rays over 37 Years of GOES Observations - The Invariance of Self-Organized Criticality during Three Solar Cycles

    E-print Network

    Aschwanden, Markus J

    2012-01-01

    We analyzed the soft X-ray light curves from the {\\sl Geostationary Operational Environmental Satellites (GOES)} over the last 37 years (1975-2011) and measured with an automated flare detection algorithm over 300,000 solar flare events (amounting to $\\approx 5$ times higher sensitivity than the NOAA flare catalog). We find a powerlaw slope of $\\alpha_F=1.98\\pm0.11$ for the (background-subtracted) soft X-ray peak fluxes that is invariant through three solar cycles and agrees with the theoretical prediction $\\alpha_F=2.0$ of the {\\sl fractal-diffusive self-organized criticality (FD-SOC)} model. For the soft X-ray flare rise times we find a powerlaw slope of $\\alpha_T =2.02\\pm0.04$ during solar cycle minima years, which is also consistent with the prediction $\\alpha_T=2.0$ of the FD-SOC model. During solar cycle maxima years, the powerlaw slope is steeper in the range of $\\alpha_T \\approx 2.0-5.0$, which can be modeled by a solar cycle-dependent flare pile-up bias effect. These results corroborate the FD-SOC mo...

  5. Estimating the Properties of Hard X-Ray Solar Flares by Constraining Model Parameters

    NASA Astrophysics Data System (ADS)

    Ireland, J.; Tolbert, A. K.; Schwartz, R. A.; Holman, G. D.; Dennis, B. R.

    2013-06-01

    We wish to better constrain the properties of solar flares by exploring how parameterized models of solar flares interact with uncertainty estimation methods. We compare four different methods of calculating uncertainty estimates in fitting parameterized models to Ramaty High Energy Solar Spectroscopic Imager X-ray spectra, considering only statistical sources of error. Three of the four methods are based on estimating the scale-size of the minimum in a hypersurface formed by the weighted sum of the squares of the differences between the model fit and the data as a function of the fit parameters, and are implemented as commonly practiced. The fourth method is also based on the difference between the data and the model, but instead uses Bayesian data analysis and Markov chain Monte Carlo (MCMC) techniques to calculate an uncertainty estimate. Two flare spectra are modeled: one from the Geostationary Operational Environmental Satellite X1.3 class flare of 2005 January 19, and the other from the X4.8 flare of 2002 July 23. We find that the four methods give approximately the same uncertainty estimates for the 2005 January 19 spectral fit parameters, but lead to very different uncertainty estimates for the 2002 July 23 spectral fit. This is because each method implements different analyses of the hypersurface, yielding method-dependent results that can differ greatly depending on the shape of the hypersurface. The hypersurface arising from the 2005 January 19 analysis is consistent with a normal distribution; therefore, the assumptions behind the three non-Bayesian uncertainty estimation methods are satisfied and similar estimates are found. The 2002 July 23 analysis shows that the hypersurface is not consistent with a normal distribution, indicating that the assumptions behind the three non-Bayesian uncertainty estimation methods are not satisfied, leading to differing estimates of the uncertainty. We find that the shape of the hypersurface is crucial in understanding the output from each uncertainty estimation technique, and that a crucial factor determining the shape of hypersurface is the location of the low-energy cutoff relative to energies where the thermal emission dominates. The Bayesian/MCMC approach also allows us to provide detailed information on probable values of the low-energy cutoff, Ec , a crucial parameter in defining the energy content of the flare-accelerated electrons. We show that for the 2002 July 23 flare data, there is a 95% probability that Ec lies below approximately 40 keV, and a 68% probability that it lies in the range 7-36 keV. Further, the low-energy cutoff is more likely to be in the range 25-35 keV than in any other 10 keV wide energy range. The low-energy cutoff for the 2005 January 19 flare is more tightly constrained to 107 ± 4 keV with 68% probability. Using the Bayesian/MCMC approach, we also estimate for the first time probability density functions for the total number of flare-accelerated electrons and the energy they carry for each flare studied. For the 2002 July 23 event, these probability density functions are asymmetric with long tails orders of magnitude higher than the most probable value, caused by the poorly constrained value of the low-energy cutoff. The most probable electron power is estimated at 1028.1 erg s-1, with a 68% credible interval estimated at 1028.1-1029.0 erg s-1, and a 95% credible interval estimated at 1028.0-1030.2 erg s-1. For the 2005 January 19 flare spectrum, the probability density functions for the total number of flare-accelerated electrons and their energy are much more symmetric and narrow: the most probable electron power is estimated at 1027.66 ± 0.01 erg s-1 (68% credible intervals). However, in this case the uncertainty due to systematic sources of error is estimated to dominate the uncertainty due to statistical sources of error.

  6. Toward magnetic field dissipation during the 23 July 2002 solar flare measured with Solar

    E-print Network

    Zharkova, Valentina V.

    Imager (RHESSI) Valentina V. Zharkova, Sergey I. Zharkov, Stanley S. Ipson, and Ali K. Benkhalil are proposed based on HXR and g-ray emission. Citation: Zharkova, V. V., S. I. Zharkov, S. S. Ipson, and A. K variations were detected for the Bastille flare 2000 [Kosovichev and Zharkova, 2001] using the LOS SOHO

  7. On the Nature of the Extreme-ultraviolet Late Phase of Solar Flares

    NASA Astrophysics Data System (ADS)

    Li, Y.; Ding, M. D.; Guo, Y.; Dai, Y.

    2014-10-01

    The extreme-ultraviolet (EUV) late phase of solar flares is a second peak of warm coronal emissions (e.g., Fe XVI) for many minutes to a few hours after the GOES soft X-ray peak. It was first observed by the EUV Variability Experiment on board the Solar Dynamics Observatory (SDO). The late-phase emission originates from a second set of longer loops (late-phase loops) that are higher than the main flaring loops. It is suggested to be caused by either additional heating or long-lasting cooling. In this paper, we study the role of long-lasting cooling and additional heating in producing the EUV late phase using the enthalpy based thermal evolution of loops model. We find that a long cooling process in late-phase loops can well explain the presence of the EUV late-phase emission, but we cannot exclude the possibility of additional heating in the decay phase. Moreover, we provide two preliminary methods based on the UV and EUV emissions from the Atmospheric Imaging Assembly on board SDO to determine whether or not additional heating plays a role in the late-phase emission. Using nonlinear force-free field modeling, we study the magnetic configuration of the EUV late phase. It is found that the late phase can be generated either in hot spine field lines associated with a magnetic null point or in large-scale magnetic loops of multipolar magnetic fields. In this paper, we also discuss why the EUV late phase is usually observed in warm coronal emissions and why the majority of flares do not exhibit an EUV late phase.

  8. Fiber Bursts in Solar Flares at High Time and Frequency Resolution

    NASA Astrophysics Data System (ADS)

    White, Stephen M.; Liu, Z.; Gary, D. E.; Nita, G. M.; Hurford, G. J.

    2007-05-01

    The FASR Subsystem Testbed (FST), operating on three dishes of the Owens Valley Solar Array, detected radio fiber bursts in two large solar flares in 2006. The frequencies of observation correspond to densities of order 10 to the 10 per cc, so the bursts are being emitted low in the corona, presumably near the energy release region. The fiber bursts drift in frequency with time, and appear to be travelling outwards. In one model, fiber bursts can be used to infer the magnetic field in the corona in the emission site. The FST data provide radio spectra of the bursts with a time resolution of milliseconds: using this exceptional data, we present the properties of the bursts and discuss their physical interpretation.

  9. The solar flare iron line to continuum ratio and the coronal abundances of iron and helium

    NASA Technical Reports Server (NTRS)

    Mckenzie, D. L.

    1975-01-01

    Narrow band Ross filter measurements of the Fe 25 line flux around 0.185 nm and simultaneous broadband measurements during a solar flare were used to determine the relationship between the solar coronal abundances of iron and helium. The Fe 25 ion population was also determined as a function of time. The proportional counter and the Ross filter on OSO-7 were utilized. The data were analyzed under the separate assumptions that (1) the electron density was high enough that a single temperature could characterize the continuum spectrum and the ionization equilibrium, and that (2) the electron density was low so that the ion populations trailed the electron temperature in time. It was found that the density was at least 5x10 to the 9th power, and that the high density assumption was valid. It was also found that the iron abundance is 0.000011 for a helium abundance of 0.2, relative to hydrogen.

  10. First high spatial resolution interferometric observations of solar flares at millimeter wavelengths

    SciTech Connect

    Kundu, M.R.; White, S.M.; Gopalswamy, N.; Bieging, J.H.; Hurford, G.J. (Maryland Univ., College Park (USA) California Univ., Berkeley (USA) California Institute of Technology, Pasadena (USA))

    1990-08-01

    The first high spatial resolution interferometric observations of solar flares at millimeter wavelengths, carried out with the Berkeley-Illinois-Maryland Array are presented. The observations were made at 3.3 mm wavelength during the very active periods of March 1989, using one or three baselines with fringe spacings of 2-5 arcsec. The observations represent an improvement of an order of magnitude in both sensitivity and spatial resolution compared with previous solar observations at these wavelengths. It appears that millimeter burst sources are not much smaller than microwave sources. The most intense bursts imply brightness temperatures of over 10 to the 6th K and are due to nonthermal gyrosynchrotron emission or possibly thermal free-free emission. If the emission in the flash phase is predominantly due to gyrosynchrotron emission, thermal gyrosynchrotron models can be ruled out for the radio emission because the flux at millimeter wavelengths is too high. 8 refs.

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

    SciTech Connect

    Doschek, G. A.; Warren, H. P. [Space Science Division, Naval Research Laboratory, Washington, DC 20375 (United States); McKenzie, D. E. [Montana State University, Bozeman, MT 59717 (United States)

    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.

  12. Electron-rich particle events and the production of gamma-rays by solar flares

    NASA Technical Reports Server (NTRS)

    Evenson, P.; Meyer, P.; Yanagita, S.; Forrest, D. J.

    1984-01-01

    The abundance of electrons of 5-50 MeV energies relative to protons of similar energy has been determined in a total of 49 particle events of apparently solar origin during the year 1980. Most events with high electron abundances appear to have been produced by flares which also produced observable fluxes of gamma-rays. The overall distribution of abundances is consistent with that measured in 1968-1970 at similar energies, but is systematically lower in electron content than abundance distributions measured at lower energies. Electron-rich particle events have harder electron spectra than more normal events, and are never accompanied by strong interplanetary shocks. Therefore, an investigation is conducted to decide whether observations are consistent with models in which energetic particles are accelerated by a shock produced at the flare site. It is concluded that, in such models, the variable nature of the interplanetary particle events must reflect some fundamental but variable property of the shocks - possibly their direction of propagation. An outward moving shock may produce a particle event in interplanetary space whereas a shock directed toward the sun may produce a flux of particles in the lower solar atmosphere which generate the gamma-radiation.

  13. Hydrogen Balmer line formation in solar flares affected by return currents

    E-print Network

    Jiri Stepan; Jana Kasparova; Marian Karlicky; Petr Heinzel

    2007-08-02

    Aims. We investigate the effect of the electric return currents in solar flares on the profiles of hydrogen Balmer lines. We consider the monoenergetic approximation for the primary beam and runaway model of the neutralizing return current. Methods. Propagation of the 10 keV electron beam from a coronal reconnection site is considered for the semiempirical chromosphere model F1. We estimate the local number density of return current using two approximations for beam energy fluxes between $4\\times 10^{11}$ and $1\\times 10^{12} {\\rm erg cm^{-2} s^{-1}}$. Inelastic collisions of beam and return-current electrons with hydrogen are included according to their energy distributions, and the hydrogen Balmer line intensities are computed using an NLTE radiative transfer approach. Results. In comparison to traditional NLTE models of solar flares that neglect the return-current effects, we found a significant increase emission in the Balmer line cores due to nonthermal excitation by return current. Contrary to the model without return current, the line shapes are sensitive to a beam flux. It is the result of variation in the return-current energy that is close to the hydrogen excitation thresholds and the density of return-current electrons.

  14. THE EFFECTS OF WAVE ESCAPE ON FAST MAGNETOSONIC WAVE TURBULENCE IN SOLAR FLARES

    SciTech Connect

    Pongkitiwanichakul, Peera; Chandran, Benjamin D. G. [Space Science Center and Department of Physics, University of New Hampshire, Durham, NH 03824 (United States); Karpen, Judith T. [NASA Goddard Space Flight Center, Greenbelt, MD 20771 (United States); DeVore, C. Richard, E-mail: pbu3@unh.edu, E-mail: benjamin.chandran@unh.edu, E-mail: judy.karpen@nasa.gov, E-mail: devore@nrl.navy.mil [Naval Research Laboratory, Washington, DC 20375 (United States)

    2012-09-20

    One of the leading models for electron acceleration in solar flares is stochastic acceleration by weakly turbulent fast magnetosonic waves ({sup f}ast waves{sup )}. In this model, large-scale flows triggered by magnetic reconnection excite large-wavelength fast waves, and fast-wave energy then cascades from large wavelengths to small wavelengths. Electron acceleration by large-wavelength fast waves is weak, and so the model relies on the small-wavelength waves produced by the turbulent cascade. In order for the model to work, the energy cascade time for large-wavelength fast waves must be shorter than the time required for the waves to propagate out of the solar-flare acceleration region. To investigate the effects of wave escape, we solve the wave kinetic equation for fast waves in weak turbulence theory, supplemented with a homogeneous wave-loss term. We find that the amplitude of large-wavelength fast waves must exceed a minimum threshold in order for a significant fraction of the wave energy to cascade to small wavelengths before the waves leave the acceleration region. We evaluate this threshold as a function of the dominant wavelength of the fast waves that are initially excited by reconnection outflows.

  15. Microwave, soft and hard X-ray imaging observations of two solar flares

    NASA Technical Reports Server (NTRS)

    Kundu, M. R.; Erskine, F. T.; Schmahl, E. J.; Machado, M. E.; Rovira, M. G.

    1984-01-01

    A set of microwave and hard X-ray observations of two flares observed simultaneously with the Very Large Array (VLA) and the Solar Maximum Mission Hard X-ray Imaging Spectrometer (SMM-HXIS) are presented. The LVA was used at 6 cm to map the slowly varying and burst components in three neighboring solar active regions (Boulder Nos. 2522, 2530, and 2519) from approximately 14:00 UT until 01:00 UT on June 24-25, 1980. Six microwave bursts less than 30 sfu were observed, and for the strongest of these, two-dimensional 'snapshot' (10 s) maps with spatial resolution of 5 in. were synthesized. HXIS data show clear interconnections between regions 2522 and 2530. The X-ray observations present a global picture of flaring activity, while the VLA data show the complexity of the small magnetic structures associated with the impulsive phase phenomena. It is seen that energy release did not occur in a single isolated magnetic structure, but over a large area of intermingled loop structures.

  16. Does There Exist a Relationship Between Acoustic and White-Light Emission in Hard-X ray Solar Flares?

    NASA Astrophysics Data System (ADS)

    Buitrago-Casas, J. C.; Martinez Oliveros, J. C.; Glesener, L.; Krucker, S.; Calvo-Mozo, B.

    2014-12-01

    Several mechanisms have been proposed to explain the observed seismicity during some solar flares. One theory associates high-energy electrons and white-light emission with sunquakes. This relationship is based on the back-warming model, where high-energy electrons and their subsequent heating of the photosphere induce acoustic waves in the solar interior. We carried out a correlative study of solar flares with emission in hard-X rays (HXRs) above 50 keV, enhanced white light emission at 6573Å, and acoustic sources. We selected those flares observed by RHESSI (Reuven Ramaty High Energy Solar Spectroscopic Imager) with a considerable flux in the 50-100 and 100-300 keV bands between January 1, 2010 and June 26, 2014. Additionally, we restricted the sample to flares close to disk center where it is observationally easiest to detect a sunquake. We then used data from the Helioseismic and Magnetic Imager onboard the Solar Dynamic Observatory (SDO/HMI) to search for white-light emission and helioseismic signatures. Finally, we calculated a coefficient of correlation for this set of dichotomic observables. We discuss the phenomenological connectivity between these physical quantities and the observational difficulties of detecting seismic signals and white-light radiation with terrestrial and space-borne observations.

  17. Hot Spine Loops and the Nature of a Late-Phase Solar Flare

    NASA Astrophysics Data System (ADS)

    Sun, Xudong; Hoeksema, J. T.; Liu, Y.; Aulanier, G.; Su, Y.; Hannah, I.; Hock, R.

    2013-07-01

    The fan-spine magnetic topology is believed to be responsible for many curious emission signatures in solar explosive events. A spine field line links topologically distinct flux domains and possibly their evolutionary trends, but direct observation of such structure has been rare. Here we report a unique event observed by the Solar Dynamic Observatory (SDO) where a set of hot coronal loops (over 10 MK) that developed during the rising phase of the flare connected to a quasi-circular chromospheric ribbon at one end and a remote brightening at the other. Magnetic field extrapolation suggests these loops are partly tracers of the evolving spine field line. The sequential brightening of the ribbon, the apparent shuffling loop motion, and the increasing volume occupied by the hot loops suggest that continuous slipping- and null-point-type reconnections were at work, energizing the loop plasma and transferring magnetic flux within and across the dome-shaped, fan quasi-separatrix layer (QSL). We argue that the initial reconnection is of the "break-out" type, which transitioned to more violent flare reconnection nearing the flare peak with an eruption from the fan dome. Significant magnetic field changes are expected and indeed ensued, which include a shift of the QSL footprint, an increase of the horizontal photospheric field, and de-shearing of the coronal loops. This event also features an extreme-ultraviolet (EUV) late phase -- a second emission peak observed in the warm EUV lines (about 2--7 MK) up to 1--2 hours after the soft X-ray peak. We show that this peak comes from the large post-flare arcades beside and above the compact fan dome, a direct product of eruption in such topological settings. Cooling of these large arcades naturally explains the sequential delay of the late-phase peaks in increasingly cooler EUV lines, and the estimated theoretical cooling time is compatible with observation. Our result demonstrates the critical nature of cross-scale magnetic coupling -- minor topological change in a sub-system may lead to explosions on a much larger scale.

  18. PROPERTIES OF A SOLAR FLARE KERNEL OBSERVED BY HINODE AND SDO

    SciTech Connect

    Young, P. R. [College of Science, George Mason University, 4400 University Drive, Fairfax, VA 22030 (United States)] [College of Science, George Mason University, 4400 University Drive, Fairfax, VA 22030 (United States); Doschek, G. A.; Warren, H. P. [Naval Research Laboratory, 4555 Overlook Avenue SW, Washington, DC 20375 (United States)] [Naval Research Laboratory, 4555 Overlook Avenue SW, Washington, DC 20375 (United States); Hara, H. [National Astronomical Observatory of Japan/NINS, 2-21-1 Osawa, Mitaka, Tokyo 181-8588 (Japan)] [National Astronomical Observatory of Japan/NINS, 2-21-1 Osawa, Mitaka, Tokyo 181-8588 (Japan)

    2013-04-01

    Flare kernels are compact features located in the solar chromosphere that are the sites of rapid heating and plasma upflow during the rise phase of flares. An example is presented from a M1.1 class flare in active region AR 11158 observed on 2011 February 16 07:44 UT for which the location of the upflow region seen by EUV Imaging Spectrometer (EIS) can be precisely aligned to high spatial resolution images obtained by the Atmospheric Imaging Assembly (AIA) and Helioseismic and Magnetic Imager (HMI) on board the Solar Dynamics Observatory (SDO). A string of bright flare kernels is found to be aligned with a ridge of strong magnetic field, and one kernel site is highlighted for which an upflow speed of Almost-Equal-To 400 km s{sup -1} is measured in lines formed at 10-30 MK. The line-of-sight magnetic field strength at this location is Almost-Equal-To 1000 G. Emission over a continuous range of temperatures down to the chromosphere is found, and the kernels have a similar morphology at all temperatures and are spatially coincident with sizes at the resolution limit of the AIA instrument ({approx}<400 km). For temperatures of 0.3-3.0 MK the EIS emission lines show multiple velocity components, with the dominant component becoming more blueshifted with temperature from a redshift of 35 km s{sup -1} at 0.3 MK to a blueshift of 60 km s{sup -1} at 3.0 MK. Emission lines from 1.5-3.0 MK show a weak redshifted component at around 60-70 km s{sup -1} implying multi-directional flows at the kernel site. Significant non-thermal broadening corresponding to velocities of Almost-Equal-To 120 km s{sup -1} is found at 10-30 MK, and the electron density in the kernel, measured at 2 MK, is 3.4 Multiplication-Sign 10{sup 10} cm{sup -3}. Finally, the Fe XXIV {lambda}192.03/{lambda}255.11 ratio suggests that the EIS calibration has changed since launch, with the long wavelength channel less sensitive than the short wavelength channel by around a factor two.

  19. The Multi-Instrument (EVE-RHESSI) DEM for Solar Flares, and Implications for Non-thermal Emission

    NASA Astrophysics Data System (ADS)

    McTiernan, J. M.; Caspi, A.; Warren, H. P.

    2013-12-01

    Observations of hard X-ray bremmstrahlung from solar flares directly probe the non-thermal electron population. For low energies, however, the spectra are typically dominated by thermal emission and the low energy extent of the non-thermal spectrum can be only loosely quantified. To address this issue, we combine observations from the EUV Variability Experiment (EVE) on-board the Solar Dynamics Observatory (SDO) and X-ray data from the Reuven Ramaty High Energy Spectroscopic Imager (RHESSI). For a sample of solar flares, we model the emission using a Differential Emission Measure (DEM) for the thermal emission seen with both instruments and a power law fit for the non-thermal emission observed by RHESSI. Spectra for both instruments are fit simultaneously in a self-consistent manner. This improvement over the traditional isothermal approximation for thermal flare emission is intended to resolve the ambiguity in the range where the thermal and non-thermal components may have similar photon fluxes. This "crossover" range can extend up to 30 keV for medium to large solar flares. It is expected that a low energy cutoff of the non-thermal electron spectrum is in this energy range, but is obscured by thermal emission. For each flare in the sample we establish limits for the low energy cutoff of the non-thermal spectrum. These limits, in turn, can be used to establish limits on the energy of non-thermal electrons accelerated during the flare. This research is supported by NASA contract NAS5-98033 and NASA Heliophysics Guest Investigator Grant NNX12AH48G.

  20. Occurrence of high-speed solar wind streams over the Grand Modern Maximum

    NASA Astrophysics Data System (ADS)

    Mursula, Kalevi; Lukianova, Renata; Holappa, Lauri

    2015-04-01

    In the declining phase of the solar cycle, when the new-polarity fields of the solar poles are strengthened by the transport of same-signed magnetic flux from lower latitudes, the polar coronal holes expand and form non-axisymmetric extensions toward the solar equator. These extensions enhance the occurrence of high-speed solar wind streams (HSS) and related co-rotating interaction regions in the low-latitude heliosphere, and cause moderate, recurrent geomagnetic activity in the near-Earth space. Here, using a novel definition of geomagnetic activity at high (polar cap) latitudes and the longest record of magnetic observations at a polar cap station, we calculate the annually averaged solar wind speeds as proxies for the effective annual occurrence of HSS over the whole Grand Modern Maximum (GMM) from 1920s onwards. We find that a period of high annual speeds (frequent occurrence of HSS) occurs in the declining phase of each solar cycle 16-23. For most cycles the HSS activity clearly maximizes during one year, suggesting that typically only one strong activation leading to a coronal hole extension is responsible for the HSS maximum. We find that the most persistent HSS activity occurred in the declining phase of solar cycle 18. This suggests that cycle 19, which marks the sunspot maximum period of the GMM, was preceded by exceptionally strong polar fields during the previous sunspot minimum. This gives interesting support for the validity of solar dynamo theory during this dramatic period of solar magnetism.

  1. Transient behavior of a flare-associated solar wind. I - Gas dynamics in a radial open field region

    NASA Technical Reports Server (NTRS)

    Nagai, F.

    1984-01-01

    A numerical investigation is conducted into the way in which a solar wind model initially satisfying both steady state and energy balance conditions is disturbed and deformed, under the assumption of heating that correspoonds to the energy release of solar flares of an importance value of approximately 1 which occur in radial open field regions. Flare-associated solar wind transient behavior is modeled for 1-8 solar radii. The coronal temperature around the heat source region rises, and a large thermal conductive flux flows inward to the chromosphere and outward to interplanetary space along field lines. The speed of the front of expanding chromospheric material generated by the impingement of the conduction front on the upper chromosphere exceeds the local sound velocity in a few minutes and eventually exceeds 100 million cm/sec.

  2. Pre-pulses: Signature of a trigger process in short (less than 60 secs) solar hard X ray flares

    Microsoft Academic Search

    U. Deasi; Larry E. Orwig

    1989-01-01

    The continuing study of short hard x ray events (less than 60 sec duration) from the Solar Maximum Mission (SMM) Hard X ray Burst Spectrometer (HXRBS) instrument has revealed a unique feature. A well-separated distinctly identifiable, narrow (2 to 6 sec wide) pulse occurs prior to the start of the longer-flare lasting emission activity. Light curves are presented for eight

  3. THE n-DISTRIBUTION OF ELECTRONS AND DOUBLE LAYERS IN THE ELECTRON-BEAM-RETURN-CURRENT SYSTEM OF SOLAR FLARES

    SciTech Connect

    Karlicky, Marian, E-mail: karlicky@asu.cas.cz [Astronomical Institute of the Academy of Sciences of the Czech Republic, CZ-25165 Ondrejov (Czech Republic)

    2012-05-01

    We investigate processes in the electron-beam-return-current system in the impulsive phase of solar flares to answer a question about the formation of the n-electron distribution detected in this phase of solar flares. An evolution of the electron-beam-return-current system with an initial local density depression is studied using a three-dimensional electromagnetic particle-in-cell model. In the system the strong double layer is formed. Its electric field potential increases with the electron beam flux. In this electric field potential, the electrons of background plasma are strongly accelerated and propagate in the return-current direction. The high-energy part of their distribution at the high-potential side of the strong double layer resembles that of the n-distribution. Thus, the detection of the n-distributions, where a form of the high-energy part of the distribution is the most important, can indicate the presence of strong double layers in solar flares. The similarity between processes in solar flare loops and those in the downward current region of the terrestrial aurora, where the double layers were observed by FAST satellite, supports this idea.

  4. Hamilton Echelle Spectroscopy of the 6 March 1993 Solar Flare 1 Christopher M. Johns--Krull 2

    E-print Network

    Johns-Krull, Christopher M.

    Donald Observatory, University of Texas, Austin, TX 78712, cmj@astro.as.utexas.edu Suzanne L. Hawley 3 Physics -- Instrumentation: Miscellaneous 2 #12; 1. Introduction Flares are among the most energetic phenomena in the solar cases optical continuum radiation is also ob­ served (Neidig, 1989). The impulsive phase is usu­ ally

  5. Flare energetics

    NASA Technical Reports Server (NTRS)

    Wu, S. T.; Dejager, C.; Dennis, B. R.; Hudson, H. S.; Simnett, G. M.; Strong, K. T.; Bentley, R. D.; Bornmann, P. L.; Bruner, M. E.; Cargill, P. J.

    1986-01-01

    In this investigation of flare energetics, researchers sought to establish a comprehensive and self-consistent picture of the sources and transport of energy within a flare. To achieve this goal, they chose five flares in 1980 that were well observed with instruments on the Solar Maximum Mission, and with other space-borne and ground-based instruments. The events were chosen to represent various types of flares. Details of the observations available for them and the corresponding physical parameters derived from these data are presented. The flares were studied from two perspectives, the impulsive and gradual phases, and then the results were compared to obtain the overall picture of the energics of these flares. The role that modeling can play in estimating the total energy of a flare when the observationally determined parameters are used as the input to a numerical model is discussed. Finally, a critique of the current understanding of flare energetics and the methods used to determine various energetics terms is outlined, and possible future directions of research in this area are suggested.

  6. High-Energy Solar Flare Studies with HAWC and Neutron Monitors

    NASA Astrophysics Data System (ADS)

    Ryan, J. M.; de Nolfo, G. A.; HAWC Collaboration

    2013-05-01

    Solar flares can produce ions in excess of 1 GeV/nuc, both impulsively and for extended periods of time. We know this by way of the ? radiation those ions produce. We have witnessed this in several Fermi flares above 100 MeV as well as in the data from SMM and Compton. Our ability to deduce the nature of parent ion population responsible for the ? rays is limited by the confounding multiple processes that separate the ion population from the consequent photons. However, when neutrons (>500 MeV) are produced, which should be almost every time pions are produced, we have complementary information about the ion spectrum if those neutrons are measured. The ? rays are most closely tied to the ion spectrum near the pion production threshold, while the ground level neutrons sample the ion spectrum >1 GeV. Together these two measurements provide information on the ion spectral shape and its turnover at high energy. The turnover embodies critical information about the parameters of the acceleration process and environment. Above 500 MeV, neutrons can be detected at the ground near the subsolar point. HAWC, the High Altitude Water ?erenkov ?-ray telescope is designed to measure cosmic TeV ?-ray sources. HAWC resides on Sierra Negra in Mexico at a latitude of 19 degrees and an altitude of 623 mbar. Neutron signals detected by HAWC will be from higher energy ions at the Sun, compared to the bulk of photons detected by Fermi. If a ? signal is also present in HAWC, this will be additional information with which to examine the solar ion spectrum. The neutron and ? data from HAWC and neutron monitors when combined with data from Fermi LAT/GBM will constitute the the most comprehensive measure of the high-energy solar ion spectrum.

  7. High-Energy Solar Flare Studies with HAWC and Neutron Monitors

    NASA Astrophysics Data System (ADS)

    Ryan, J. M.

    2013-12-01

    Solar flares can produce ions in excess of 1 GeV/nuc, both impulsively and for extended periods of time. We know this by way of the ? radiation those ions produce. We have witnessed this in several Fermi flares above 100 MeV as well as in the data from SMM and Compton. Our ability to deduce the nature of parent ion population responsible for the ? rays is limited by the confounding multiple processes that separate the ion population from the consequent photons. However, when neutrons (>500 MeV) are produced, which should be almost every time pions are produced, we have complementary information about the ion spectrum if those neutrons are measured. The ? rays are most closely tied to the ion spectrum near the pion production threshold, while the ground level neutrons sample the ion spectrum >1 GeV. Together these two measurements provide information on the ion spectral shape and its turnover at high energy. The turnover embodies critical information about the parameters of the acceleration process and environment. Above 500 MeV, neutrons can be detected at the ground near the subsolar point. HAWC, the High Altitude Water ?erenkov ?-ray telescope is designed to measure cosmic TeV ?-ray sources. HAWC resides on Sierra Negra in Mexico at a latitude of 19 degrees and an altitude of ~14,000 ft., 623 mbar. Neutron signals detected by HAWC will be from higher energy ions at the Sun, compared to the bulk of photons detected by Fermi. If a ? signal is also present in HAWC, this will be additional information with which to examine the solar ion spectrum. The neutron and ? data from HAWC and neutron monitors when combined with data from Fermi LAT/GBM will constitute the the most comprehensive measure of the high-energy solar ion spectrum.

  8. An Extreme Solar Event of 20 January 2005: Properties of the Flare and the Origin of Energetic Particles

    Microsoft Academic Search

    V. V. Grechnev; V. G. Kurt; I. M. Chertok; A. M. Uralov; H. Nakajima; A. T. Altyntsev; A. V. Belov; B. Yu. Yushkov; S. N. Kuznetsov; L. K. Kashapova; N. S. Meshalkina; N. P. Prestage

    2008-01-01

    The famous extreme solar and particle event of 20 January 2005 is analyzed from two perspectives. Firstly, using multi-spectral\\u000a data, we study temporal, spectral, and spatial features of the main phase of the flare, when the strongest emissions from\\u000a microwaves up to 200 MeV gamma-rays were observed. Secondly, we relate our results to a long-standing controversy on the origin\\u000a of solar

  9. The impulse bursts of the nearearth space radionoises were caused by a X-ray solar flares

    Microsoft Academic Search

    S. I. Musatenko; E. V. Kurochka

    1997-01-01

    Using night measuments at the dynamic IZMIRAN spectrograpth in the 90 - 180 MHz frequency band of the nearearth space radionoises on the middle latitudes during the solar activity maximum (December, 1989) the following results were obtained: 1. The X-ray solar flare produced in the Earth's ionosphere the two types of the impulsive burst radionoises: type I is wide-band short-life

  10. HARD X-RAY FLARE SOURCE SIZES MEASURED WITH THE RAMATY HIGH ENERGY SOLAR SPECTROSCOPIC IMAGER

    SciTech Connect

    Dennis, Brian R.; Pernak, Rick L. [Solar Physics Laboratory (Code 671), Heliophysics Science Division, NASA Goddard Space Flight Center, Greenbelt, MD 20771 (United States)

    2009-06-20

    Ramaty High Energy Solar Spectroscopic Imager (RHESSI) observations of 18 double hard X-ray sources seen at energies above 25 keV are analyzed to determine the spatial extent of the most compact structures evident in each case. The following four image reconstruction algorithms were used: Clean, Pixon, and two routines using visibilities-maximum entropy and forward fit (VFF). All have been adapted for this study to optimize their ability to provide reliable estimates of the sizes of the more compact sources. The source fluxes, sizes, and morphologies obtained with each method are cross-correlated and the similarities and disagreements are discussed. The full width at half-maximum (FWHM) of the major axes of the sources with assumed elliptical Gaussian shapes are generally well correlated between the four image reconstruction routines and vary between the RHESSI resolution limit of {approx}2'' up to {approx}20'' with most below 10''. The FWHM of the minor axes are generally at or just above the RHESSI limit and hence should be considered as unresolved in most cases. The orientation angles of the elliptical sources are also well correlated. These results suggest that the elongated sources are generally aligned along a flare ribbon with the minor axis perpendicular to the ribbon. This is verified for the one flare in our list with coincident Transition Region and Coronal Explorer (TRACE) images. There is evidence for significant extra flux in many of the flares in addition to the two identified compact sources, thus rendering the VFF assumption of just two Gaussians inadequate. A more realistic approximation in many cases would be of two line sources with unresolved widths. Recommendations are given for optimizing the RHESSI imaging reconstruction process to ensure that the finest possible details of the source morphology become evident and that reliable estimates can be made of the source dimensions.

  11. Height structure of X-ray, EUV, and white-light emission in a solar flare

    NASA Astrophysics Data System (ADS)

    Battaglia, M.; Kontar, E. P.

    2011-09-01

    Context. The bulk of solar flare emission originates from very compact sources located in the lower solar atmosphere and observable at a broad range of wavelengths such as near optical, UV, EUV, soft and hard X-rays, and gamma-rays. Nevertheless, very few spatially resolved imaging observations have been performed to determine the structure of these compact regions. Aims: We investigate the above-the-photosphere heights of hard X-ray (HXR), EUV, and white-light (6173 Å) continuum sources in the low atmosphere and the corresponding densities at these heights. By considering the collisional transport of solar energetic electrons, we also determine where and how much energy is deposited and compare these values with the emissions observed in HXR, EUV, and the continuum. Methods: Simultaneous EUV/continuum images from AIA/HMI on-board SDO and HXR RHESSI images are compared to study a well-observed gamma-ray limb flare. Using RHESSI X-ray visibilities, we determine the height of the HXR sources as a function of energy above the photosphere. Co-aligning AIA/SDO and HMI/SDO images with RHESSI, we infer, for the first time, the heights and characteristic densities of HXR, EUV, and continuum (white-light) sources in the flaring footpoint of the magnetic loop. Results: We find 35-100 keV HXR sources at heights of between 1.7 and 0.8 Mm above the photosphere, below the 6173 Å continuum emission that appears at heights 1.5-3 Mm and the peak of EUV emission originating near 3 Mm. Conclusions: The EUV emission locations are consistent with energy deposition from low energy electrons of ~12 keV occurring in the top layers of the fully ionized chromosphere/low corona and not by ? 20 keV electrons that produce HXR footpoints in the lower neutral chromosphere. The maximum of white-light continuum emission appears between the HXR and EUV emission, presumably in the transition between ionized and neutral atmospheres, implying that it consists of free-bound and free-free continuum emission. We note that the energy deposited by low energy electrons is sufficient to explain the energetics of both the optical and UV emissions. Two movies are available in electronic form at http://www.aanda.org

  12. MAGNETIC NON-POTENTIALITY OF SOLAR ACTIVE REGIONS AND PEAK X-RAY FLUX OF THE ASSOCIATED FLARES

    SciTech Connect

    Tiwari, Sanjiv Kumar; Venkatakrishnan, P.; Gosain, Sanjay, E-mail: pvk@prl.res.i, E-mail: sgosain@prl.res.i [Udaipur Solar Observatory, Physical Research Laboratory, Dewali, Bari Road, Udaipur 313 001 (India)

    2010-09-20

    Predicting the severity of solar eruptive phenomena such as flares and coronal mass ejections remains a great challenge despite concerted efforts to do so over the past several decades. However, the advent of high-quality vector magnetograms obtained from Hinode (SOT/SP) has increased the possibility of meeting this challenge. In particular, the spatially averaged signed shear angle (SASSA) seems to be a unique parameter for quantifying the non-potentiality of active regions. We demonstrate the usefulness of the SASSA for predicting flare severity. For this purpose, we present case studies of the evolution of magnetic non-potentiality using 115 vector magnetograms of four active regions, namely, ARs NOAA 10930, 10960, 10961, and 10963 during 2006 December 8-15, 2007 June 3-10, 2007 June 28-July 5, and 2007 July 10-17, respectively. The NOAA ARs 10930 and 10960 were very active and produced X and M class flares, respectively, along with many smaller X-ray flares. On the other hand, the NOAA ARs 10961 and 10963 were relatively less active and produced only very small (mostly A- and B-class) flares. For this study, we have used a large number of high-resolution vector magnetograms obtained from Hinode (SOT/SP). Our analysis shows that the peak X-ray flux of the most intense solar flare emanating from the active regions depends on the magnitude of the SASSA at the time of the flare. This finding of the existence of a lower limit of the SASSA for a given class of X-ray flares will be very useful for space weather forecasting. We have also studied another non-potentiality parameter called the mean weighted shear angle (MWSA) of the vector magnetograms along with the SASSA. We find that the MWSA does not show such distinction as the SASSA for upper limits of the GOES X-ray flux of solar flares; however, both the quantities show similar trends during the evolution of all active regions studied.

  13. Hard X-ray bremsstrahlung production in solar flares by high-energy proton beams

    NASA Technical Reports Server (NTRS)

    Emslie, A. G.; Brown, J. C.

    1985-01-01

    The possibility that solar hard X-ray bremsstrahlung is produced by acceleration of stationary electrons by fast-moving protons, rather than vice versa, as commonly assumed, was investigated. It was found that a beam of protons which involves 1836 times fewer particles, each having an energy 1836 times greater than that of the electrons in the equivalent electron beam model, has exactly the same bremsstrahlung yield for a given target, i.e., the mechanism has an energetic efficiency equal to that of conventional bremsstrahlung models. Allowance for the different degrees of target ionization appropriate to the two models (for conventional flare geometries) makes the proton beam model more efficient than the electron beam model, by a factor of order three. The model places less stringent constraints than a conventional electron beam model on the flare energy release mechanism. It is also consistent with observed X-ray burst spectra, intensities, and directivities. The altitude distribution of hard X-rays predicted by the model agrees with observations only if nonvertical injection of the protons is assumed. The model is inconsistent with gamma-ray data in terms of conventional modeling.

  14. The solar flare extreme ultraviolet to hard X-ray ratio

    NASA Technical Reports Server (NTRS)

    Mcclymont, A. N.; Canfield, R. C.

    1986-01-01

    Simultaneous measurements of the peak 10-1030 A extreme ultraviolet (EUV) flux enhancement and more than 10 keV hard X-ray (HXR) peak flux of many solar flare bursts, ranging over about four orders of magnitude in HXR intensity, are studied. A real departure from linearity is found in the relationship between the peak EUV and HXR fluxes in impulsive flare bursts. This relationship is well described by a given power law. Comparison of the predictions of the impulsive nonthermal thick-target electron beam model with observations shows that the model satisfactorily predicts the observed time differences between the HXR and EUV peaks and explains the data very well under given specific assumptions. It is concluded that the high-energy fluxes implied by the invariant area thick-target model cannot be completely ruled out, while the invariant area model with smaller low cutoff requires impossibly large beam densities. A later alternative thick-target model is suggested.

  15. Electron Beam Return-Current Losses in Solar Flares: Initial Comparison of Analytical and Numerical Results

    NASA Technical Reports Server (NTRS)

    Holman, Gordon

    2010-01-01

    Accelerated electrons play an important role in the energetics of solar flares. Understanding the process or processes that accelerate these electrons to high, nonthermal energies also depends on understanding the evolution of these electrons between the acceleration region and the region where they are observed through their hard X-ray or radio emission. Energy losses in the co-spatial electric field that drives the current-neutralizing return current can flatten the electron distribution toward low energies. This in turn flattens the corresponding bremsstrahlung hard X-ray spectrum toward low energies. The lost electron beam energy also enhances heating in the coronal part of the flare loop. Extending earlier work by Knight & Sturrock (1977), Emslie (1980), Diakonov & Somov (1988), and Litvinenko & Somov (1991), I have derived analytical and semi-analytical results for the nonthermal electron distribution function and the self-consistent electric field strength in the presence of a steady-state return-current. I review these results, presented previously at the 2009 SPD Meeting in Boulder, CO, and compare them and computed X-ray spectra with numerical results obtained by Zharkova & Gordovskii (2005, 2006). The phYSical significance of similarities and differences in the results will be emphasized. This work is supported by NASA's Heliophysics Guest Investigator Program and the RHESSI Project.

  16. 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. [Solar Physics Laboratory, Heliophysics Science Division, NASA Goddard Space Flight Center, Greenbelt, MD 20771 (United States)

    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.

  17. Astrophysical explosions: from solar flares to cosmic gamma-ray bursts.

    PubMed

    Wheeler, J Craig

    2012-02-13

    Astrophysical explosions result from the release of magnetic, gravitational or thermonuclear energy on dynamical time scales, typically the sound-crossing time for the system. These explosions include solar and stellar flares, eruptive phenomena in accretion discs, thermonuclear combustion on the surfaces of white dwarfs and neutron stars, violent magnetic reconnection in neutron stars, thermonuclear and gravitational collapse supernovae and cosmic gamma-ray bursts, each representing a different type and amount of energy release. This paper summarizes the properties of these explosions and describes new research on thermonuclear explosions and explosions in extended circumstellar media. Parallels are drawn between studies of terrestrial and astrophysical explosions, especially the physics of the transition from deflagration-to-detonation. PMID:22213668

  18. Space-born and ground-based observations of a solar active region and a flare

    NASA Astrophysics Data System (ADS)

    Chiuderi Drago, F.

    Observational data of the active solar region AR 2490 are discussed with an eye to underlying physical processes. Ground- and spaceborne measurements were made by radio, optical, and XUV instrumentation. A double structure observed at 6 and 20 cm wavelengths was overlying a sunspot group which displayed north polarity. The 6 cm emission was attributed to free-free emission, while the 20 cm feature was thought to be caused by gyroresonance absorption. An analytical formulation was developed which described the thermal component for maximum X ray intensities. A flare observed on June 10, 1980 was detected on H-alpha and C IV spectrographic bands. The origin of the emissions was fixed at the two feet of the X ray loop, with a radio emission coming from the top of the loop.

  19. Lower hybrid resonance acceleration of electrons and ions in solar flares and the associated microwave emission

    NASA Technical Reports Server (NTRS)

    Mcclements, K. G.; Bingham, R.; Su, J. J.; Dawson, J. M.; Spicer, D. S.

    1993-01-01

    The particle acceleration processes here studied are driven by the relaxation of unstable ion ring distributions; these produce strong wave activity at the lower hybrid resonance frequency which collapses, and forms energetic electron and ion tails. The results obtained are applied to the problem posed by the production of energetic particles by solar flares. The numerical simulation results thus obtained by a 2 1/2-dimensional particle-in-cell code show a simultaneous acceleration of electrons to 10-500 keV energies, and of ions to as much as the 1 MeV range; the energy of the latter is still insufficient to account for gamma-ray emission in the 4-6 MeV range, but furnish a seed population for further acceleration.

  20. DUAL-STAGE RECONNECTION DURING SOLAR FLARES OBSERVED IN HARD X-RAY

    SciTech Connect

    Xu Yan; Jing Ju; Wang Haimin [Space Weather Research Lab, Center for Solar-Terrestial Research, New Jersey Institute of Technology, 323 Martin Luther King Blvd, Newark, NJ 07102-1982 (United States); Cao Wenda [Big Bear Solar Observatory, 40386 North Shore Lane, Big Bear City, CA 92314 (United States)], E-mail: yx2@njit.edu

    2010-02-01

    In this Letter, we present hard X-ray (HXR) observation by the Reuven Ramaty High Energy Solar Spectroscopic Imager of the 2003 October 29 X10 flare. Two pairs of HXR conjugate footpoints have been identified during the early impulsive phase. This geometric configuration is very much in the manner predicted by the 'tether-cutting' scenario first proposed by Moore and Roumeliotis. The HXR light curves show that the outer pair of footpoints disappeared much faster than the other pair. This temporal behavior further confirms that this event is a good example of the 'tether-cutting' model. In addition, we reconstructed a three-dimensional magnetic field based on the nonlinear force-free extrapolation and found that each pair of HXR footpoints were indeed linked by corresponding magnetic field lines.