HIGH-ENERGY GAMMA-RAY EMISSION FROM SOLAR FLARES: SUMMARY OF<i>FERMI</i>LARGE AREA TELESCOPE DETECTIONS AND ANALYSIS OF TWO M-CLASS FLARES

Ackermann, M.; Ajello, M.; Albert, A.; Allafort, A.; Baldini, Luca; Barbiellini, G.; Bastieri, D.; Bechtol, K.; Bellazzini, R.; Bissaldi, E.; Bonamente, E.; Bottacini, E.; Bouvier, A.; Brandt, T. J.; Bregeon, J.; Brigida, M.; Bruel, Pascal; 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.; Angelis, A. De; Palma, F. de; Dermer, C. D.; Desiante, R.; Digel, S. W.; Venere, L. Di; 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, Yoshiyuki; Jackson, M. S.; Jogler, T.; Jóhannesson, G.; Johnson, W. N.; Kamae, T.; Kawano, Takafumi; Knödlseder, J.; Kuss, M.; Landé, J.; Larsson, Stefan; 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.; Моисеев, А. А.; Monte, C.; Monzani, M. E.; Moretti, E.; Morselli, A.; Moskalenko, I. V.; Murgia, S.; Murphy, R. J.; Nemmen, R.; Nuss, E.; Ohno, M.; Ohsugi, T.; Okumura, A.; Omodei, N.; Orienti, M.; Orlando, E.; Ormes, J. F.; Paneque, D.; Panetta, J.; Perkins, J. S.; Pesce-Rollins, M.; Petrosian, V.; Piron, F.; Pivato, G.; Porter, T. A.; Rainò, S.; Rando, R.; Razzano, M.; Reimer, A.; Ritz, S.; Schulz, A.; Sgrò, C.; Siskind, E. J.; Spandre, G.; Spinelli, P.; Takahashi, H.; Takeuchi, Yoko; Tanaka, Yasuyuki; Thayer, J. G.; Thayer, J. B.; Thompson, D. J.; Tibaldo, L.; Tinivella, M.; Tosti, G.; Troja, E.; Tronconi, V.; Usher, T.; Vandenbroucke, J.; Vasileiou, V.; Vianello, G.; Vitale, V.; Werner, M. W.; Winer, B. L.; Wood, D. L.; Wood, K. S.; Wood, M.; Yang, Z.

doi:10.1088/0004-637x/787/1/15

Cited by 126 publications

(114 citation statements)

References 22 publications

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“…Time-extended nuclear gamma-ray emission, sometimes persisting over more than ten hours, was discovered by the GAMMA 1 mission (Akimov et al 1996) and the Compton Gamma-Ray Observatory (Kanbach et al 1993). The recent FERMI observations with much higher sensitivity have shown that this emission occurs rather often, even in moderate flares (Ackermann et al 2014). The greater altitude of the acceleration region and the possibly reduced access of the particles to the dense low solar atmosphere -depending on the magnetic field configurationcould explain why no such gamma-ray signatures were detected with other GLEs in the past.…”

Section: Discussionmentioning

confidence: 99%

The relativistic solar particle event of 2005 January 20: origin of delayed particle acceleration

Klein

Masson

Bouratzis

et al. 2014

A&A

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Context. The highest energies of solar energetic nucleons detected in space or through gamma-ray emission in the solar atmosphere are in the GeV range. Where and how the particles are accelerated is still controversial. Aims. We search for observational information on the location and nature of the acceleration region(s) by comparing the timing of relativistic protons detected on Earth and radiative signatures in the solar atmosphere during the particularly well-observed 2005 Jan. 20 event.Methods. This investigation focusses on the post-impulsive flare phase, where a second peak was observed in the relativistic proton time profile by neutron monitors. This time profile is compared in detail with UV imaging and radio spectrography over a broad frequency band from the low corona to interplanetary space. Results. It is shown that the late relativistic proton release to interplanetary space was accompanied by a distinct new episode of energy release and electron acceleration in the corona traced by the radio emission and by brightenings of UV kernels. These signatures are interpreted in terms of magnetic restructuring in the corona after the coronal mass ejection passage. Conclusions. We attribute the delayed relativistic proton acceleration to magnetic reconnection and possibly to turbulence in largescale coronal loops. While Type II radio emission was observed in the high corona, no evidence of a temporal relationship with the relativistic proton acceleration was found.

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Section: Discussionmentioning

confidence: 99%

The relativistic solar particle event of 2005 January 20: origin of delayed particle acceleration

Klein

Masson

Bouratzis

et al. 2014

A&A

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“…The same conclusion can be reached about other events reported by Ackermann et al (2012b) to have impulsive >100 MeV phases. Specifically, Share et al (2017) find that the first >100 MeV outburst on 2012 Mar 7 described in detail by Ackermann et al (2014) was distinct sustained emission and not directly associated with the X5.4 flare. LAT event (data points and˙1 statistical uncertainties).…”

Section: Long-duration -Ray Eventsmentioning

confidence: 96%

“…The emission was delayed about 10 s from the associated hard X-ray and nuclear-line emission and there was no evidence for any >100 MeV -ray emission in the hours after the flare. The Fermi/LAT team reported the detection of 18 >100 MeV events associated with solar flares covering the time period from 2008 August to 2012 August (Ackermann et al 2014) which they classified as being impulsive, sustained, or delayed. In some cases they categorized the events as having both impulsive and sustained characteristics.…”

Section: New Insights Of Sustained Emission Events From Fermi Observamentioning

confidence: 99%

“…We prefer to use the name "sustained" to categorize all emission that is distinct from the impulsive flare independent of its duration. Details of the 2011 Mar 7 and 2011 Jun 7 -ray observations and related solar measurements were also presented in Ackermann et al (2014). The March 7 event was reported as having both impulsive and sustained emission components, while the June 7 event was classified as only having sustained emission because -rays were detected in only one LAT exposure about 1 h after the flare and there was no exposure to the flare.…”

Section: New Insights Of Sustained Emission Events From Fermi Observamentioning

confidence: 99%

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X-Ray, Radio and SEP Observations of Relativistic Gamma-Ray Events

Klein¹,

Tziotziou²,

Zucca³

et al. 2017

Astrophysics and Space Science Library

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The rather frequent occurrence, and sometimes long duration, ofray events at photon energies above 100 MeV challenges our understanding of particle acceleration processes at the Sun. The emission is ascribed to pion-decay photons due to protons with energies above 300 MeV. We study the X-ray and radio emissions and the solar energetic particles (SEPs) in space for a set of 25 Fermi -ray events. They are accompanied by strong SEP events, including, in most cases where the parent activity is well-connected, protons above 300 MeV. Signatures of energetic electron acceleration in the corona accompany the impulsive and early post-impulsive -ray emission. -ray emission lasting several hours accompanies in general the decay phase of long-lasting soft X-ray bursts and decametric-tokilometric type II bursts. We discuss the impact of these results on the origin of the -ray events. IntroductionThe advent of the Fermi mission showed that the Sun is an occasional, but unexpectedly frequent, emitter of -ray photons above 100 MeV. These are understood to be produced by pion decays in nuclear interactions involving protons or He-nuclei at energies above 300 MeV/nucleon. One did not expect that the Sun was able to accelerate relativistic protons and nuclei even in seemingly modest flares. These particles are rarely detected in space (<1 event per year). Furthermore, the duration, several hours, of some -ray events is much longer than that of hard X-ray signatures of electron acceleration in the impulsive flare phase.The question of how the -ray emission is related to other signatures of particle acceleration and energy release in the corona is crucial to understanding the origin of the high-energy protons. It might also be expected that such high-energy populations interacting at the Sun are accompanied by particularly energetic solar energetic particle (SEP) events. This chapter is based on 25 events. The Fermi/LAT temporal data were made available to the HESPERIA project by G. Share prior to their publication in a comprehensive paper ). The present chapter introduces the relevant process of emission and pre-Fermi observations of piondecay -rays (Sect. 8.2), and gives an overview of the Fermi/LAT observations (Sect. 8.3). Section 8.3 was prepared by Gerald Share and Ron Murphy. Related X-ray and radio observations and associated SEP events are presented in Sects. 8.4 and 8.5, respectively. Preliminary conclusions on the interpretation of the -ray events are in Sect. 8.6. Theory and Early Observations of Gamma-Ray Emission at Photon Energies >60 MeVOn 1982 Jun 3 the gamma-ray spectrometer on the Solar Maximum Mission satellite observed emission from 0.3 to 100 MeV from a X8.0 GOES-class flare (Forrest et al. 1986). The impulsive flare lasted about 1 min and was followed by a distinct harder emission phase that peaked in about 1 min and lasted for over 15 min. The energy spectrum of this sustained emission displayed a characteristic hump at photon energies above 60 MeV (Fig. 8.1a), which appeared to be consistent with th...

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“…Details of the 2011 Mar 7 and 2011 Jun 7 -ray observations and related solar measurements were also presented in Ackermann et al (2014). The March 7 event was reported as having both impulsive and sustained emission components, while the June 7 event was classified as only having sustained emission because -rays were detected in only one LAT exposure about 1 h after the flare and there was no exposure to the flare.…”

Section: New Insights Of Sustained Emission Events From Fermi Observamentioning

confidence: 99%

Solar Particle Radiation Storms Forecasting and Analysis

Malandraki¹,

Crosby²

2018

Astrophysics and Space Science Library

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HIGH-ENERGY GAMMA-RAY EMISSION FROM SOLAR FLARES: SUMMARY OFFERMILARGE AREA TELESCOPE DETECTIONS AND ANALYSIS OF TWO M-CLASS FLARES

Cited by 126 publications

References 22 publications

The relativistic solar particle event of 2005 January 20: origin of delayed particle acceleration

The relativistic solar particle event of 2005 January 20: origin of delayed particle acceleration

X-Ray, Radio and SEP Observations of Relativistic Gamma-Ray Events

Solar Particle Radiation Storms Forecasting and Analysis

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