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Title: Fermi-LAT Observations of High-energy Behind-the-limb Solar Flares

In this paper, we report on the Fermi-LAT detection of high-energy emission from the behind-the-limb (BTL) solar flares that occurred on 2013 October 11, and 2014 January 6 and September 1. The Fermi-LAT observations are associated with flares from active regions originating behind both the eastern and western limbs, as determined by STEREO. All three flares are associated with very fast coronal mass ejections (CMEs) and strong solar energetic particle events. We present updated localizations of the >100 MeV photon emission, hard X-ray (HXR) and EUV images, and broadband spectra from 10 keV to 10 GeV, as well as microwave spectra. We also provide a comparison of the BTL flares detected by Fermi-LAT with three on-disk flares and present a study of some of the significant quantities of these flares as an attempt to better understand the acceleration mechanisms at work during these occulted flares. We interpret the HXR emission to be due to electron bremsstrahlung from a coronal thin-target loop top with the accelerated electron spectra steepening at semirelativistic energies. The >100 MeV gamma-rays are best described by a pion-decay model resulting from the interaction of protons (and other ions) in a thick-target photospheric source. In conclusion, the protonsmore » are believed to have been accelerated (to energies >10 GeV) in the CME environment and precipitate down to the photosphere from the downstream side of the CME shock and landed on the front side of the Sun, away from the original flare site and the HXR emission.« less
Authors:
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Publication Date:
Grant/Contract Number:
AC02-76SF00515
Type:
Accepted Manuscript
Journal Name:
The Astrophysical Journal (Online)
Additional Journal Information:
Journal Name: The Astrophysical Journal (Online); Journal Volume: 835; Journal Issue: 2; Journal ID: ISSN 1538-4357
Publisher:
Institute of Physics (IOP)
Research Org:
SLAC National Accelerator Lab., Menlo Park, CA (United States)
Sponsoring Org:
USDOE
Contributing Orgs:
Fermi LAT Collaboration
Country of Publication:
United States
Language:
English
Subject:
79 ASTRONOMY AND ASTROPHYSICS; Sun: flares; Sun: X-rays; gamma rays
OSTI Identifier:
1355739

Ackermann, M., Allafort, A., Baldini, L., Barbiellini, G., Bastieri, D., Bellazzini, R., Bissaldi, E., Bonino, R., Bottacini, E., Bregeon, J., Bruel, P., Buehler, R., Cameron, R. A., Caragiulo, M., Caraveo, P. A., Cavazzuti, E., Cecchi, C., Charles, E., Ciprini, S., Costanza, F., Cutini, S., D’Ammando, F., Palma, F. de, Desiante, R., Digel, S. W., Lalla, N. Di, Mauro, M. Di, Venere, L. Di, Drell, P. S., Favuzzi, C., Fukazawa, Y., Fusco, P., Gargano, F., Giglietto, N., Giordano, F., Giroletti, M., Grenier, I. A., Guillemot, L., Guiriec, S., Jogler, T., Jóhannesson, G., Kashapova, L., Krucker, S., Kuss, M., Mura, G. La, Larsson, S., Latronico, L., Li, J., Liu, W., Longo, F., Loparco, F., Lubrano, P., Magill, J. D., Maldera, S., Manfreda, A., Mazziotta, M. N., Mitthumsiri, W., Mizuno, T., Monzani, M. E., Morselli, A., Moskalenko, I. V., Negro, M., Nuss, E., Ohsugi, T., Omodei, N., Orlando, E., Pal’shin, V., Paneque, D., Perkins, J. S., Pesce-Rollins, M., Petrosian, V., Piron, F., Principe, G., Rainò, S., Rando, R., Razzano, M., Reimer, O., Costa, F. Rubio da, Sgrò, C., Simone, D., Siskind, E. J., Spada, F., Spandre, G., Spinelli, P., Tajima, H., Thayer, J. B., Torres, D. F., Troja, E., and Vianello, G.. Fermi-LAT Observations of High-energy Behind-the-limb Solar Flares. United States: N. p., Web. doi:10.3847/1538-4357/835/2/219.
Ackermann, M., Allafort, A., Baldini, L., Barbiellini, G., Bastieri, D., Bellazzini, R., Bissaldi, E., Bonino, R., Bottacini, E., Bregeon, J., Bruel, P., Buehler, R., Cameron, R. A., Caragiulo, M., Caraveo, P. A., Cavazzuti, E., Cecchi, C., Charles, E., Ciprini, S., Costanza, F., Cutini, S., D’Ammando, F., Palma, F. de, Desiante, R., Digel, S. W., Lalla, N. Di, Mauro, M. Di, Venere, L. Di, Drell, P. S., Favuzzi, C., Fukazawa, Y., Fusco, P., Gargano, F., Giglietto, N., Giordano, F., Giroletti, M., Grenier, I. A., Guillemot, L., Guiriec, S., Jogler, T., Jóhannesson, G., Kashapova, L., Krucker, S., Kuss, M., Mura, G. La, Larsson, S., Latronico, L., Li, J., Liu, W., Longo, F., Loparco, F., Lubrano, P., Magill, J. D., Maldera, S., Manfreda, A., Mazziotta, M. N., Mitthumsiri, W., Mizuno, T., Monzani, M. E., Morselli, A., Moskalenko, I. V., Negro, M., Nuss, E., Ohsugi, T., Omodei, N., Orlando, E., Pal’shin, V., Paneque, D., Perkins, J. S., Pesce-Rollins, M., Petrosian, V., Piron, F., Principe, G., Rainò, S., Rando, R., Razzano, M., Reimer, O., Costa, F. Rubio da, Sgrò, C., Simone, D., Siskind, E. J., Spada, F., Spandre, G., Spinelli, P., Tajima, H., Thayer, J. B., Torres, D. F., Troja, E., & Vianello, G.. Fermi-LAT Observations of High-energy Behind-the-limb Solar Flares. United States. doi:10.3847/1538-4357/835/2/219.
Ackermann, M., Allafort, A., Baldini, L., Barbiellini, G., Bastieri, D., Bellazzini, R., Bissaldi, E., Bonino, R., Bottacini, E., Bregeon, J., Bruel, P., Buehler, R., Cameron, R. A., Caragiulo, M., Caraveo, P. A., Cavazzuti, E., Cecchi, C., Charles, E., Ciprini, S., Costanza, F., Cutini, S., D’Ammando, F., Palma, F. de, Desiante, R., Digel, S. W., Lalla, N. Di, Mauro, M. Di, Venere, L. Di, Drell, P. S., Favuzzi, C., Fukazawa, Y., Fusco, P., Gargano, F., Giglietto, N., Giordano, F., Giroletti, M., Grenier, I. A., Guillemot, L., Guiriec, S., Jogler, T., Jóhannesson, G., Kashapova, L., Krucker, S., Kuss, M., Mura, G. La, Larsson, S., Latronico, L., Li, J., Liu, W., Longo, F., Loparco, F., Lubrano, P., Magill, J. D., Maldera, S., Manfreda, A., Mazziotta, M. N., Mitthumsiri, W., Mizuno, T., Monzani, M. E., Morselli, A., Moskalenko, I. V., Negro, M., Nuss, E., Ohsugi, T., Omodei, N., Orlando, E., Pal’shin, V., Paneque, D., Perkins, J. S., Pesce-Rollins, M., Petrosian, V., Piron, F., Principe, G., Rainò, S., Rando, R., Razzano, M., Reimer, O., Costa, F. Rubio da, Sgrò, C., Simone, D., Siskind, E. J., Spada, F., Spandre, G., Spinelli, P., Tajima, H., Thayer, J. B., Torres, D. F., Troja, E., and Vianello, G.. 2017. "Fermi-LAT Observations of High-energy Behind-the-limb Solar Flares". United States. doi:10.3847/1538-4357/835/2/219. https://www.osti.gov/servlets/purl/1355739.
@article{osti_1355739,
title = {Fermi-LAT Observations of High-energy Behind-the-limb Solar Flares},
author = {Ackermann, M. and Allafort, A. and Baldini, L. and Barbiellini, G. and Bastieri, D. and Bellazzini, R. and Bissaldi, E. and Bonino, R. and Bottacini, E. and Bregeon, J. and Bruel, P. and Buehler, R. and Cameron, R. A. and Caragiulo, M. and Caraveo, P. A. and Cavazzuti, E. and Cecchi, C. and Charles, E. and Ciprini, S. and Costanza, F. and Cutini, S. and D’Ammando, F. and Palma, F. de and Desiante, R. and Digel, S. W. and Lalla, N. Di and Mauro, M. Di and Venere, L. Di and Drell, P. S. and Favuzzi, C. and Fukazawa, Y. and Fusco, P. and Gargano, F. and Giglietto, N. and Giordano, F. and Giroletti, M. and Grenier, I. A. and Guillemot, L. and Guiriec, S. and Jogler, T. and Jóhannesson, G. and Kashapova, L. and Krucker, S. and Kuss, M. and Mura, G. La and Larsson, S. and Latronico, L. and Li, J. and Liu, W. and Longo, F. and Loparco, F. and Lubrano, P. and Magill, J. D. and Maldera, S. and Manfreda, A. and Mazziotta, M. N. and Mitthumsiri, W. and Mizuno, T. and Monzani, M. E. and Morselli, A. and Moskalenko, I. V. and Negro, M. and Nuss, E. and Ohsugi, T. and Omodei, N. and Orlando, E. and Pal’shin, V. and Paneque, D. and Perkins, J. S. and Pesce-Rollins, M. and Petrosian, V. and Piron, F. and Principe, G. and Rainò, S. and Rando, R. and Razzano, M. and Reimer, O. and Costa, F. Rubio da and Sgrò, C. and Simone, D. and Siskind, E. J. and Spada, F. and Spandre, G. and Spinelli, P. and Tajima, H. and Thayer, J. B. and Torres, D. F. and Troja, E. and Vianello, G.},
abstractNote = {In this paper, we report on the Fermi-LAT detection of high-energy emission from the behind-the-limb (BTL) solar flares that occurred on 2013 October 11, and 2014 January 6 and September 1. The Fermi-LAT observations are associated with flares from active regions originating behind both the eastern and western limbs, as determined by STEREO. All three flares are associated with very fast coronal mass ejections (CMEs) and strong solar energetic particle events. We present updated localizations of the >100 MeV photon emission, hard X-ray (HXR) and EUV images, and broadband spectra from 10 keV to 10 GeV, as well as microwave spectra. We also provide a comparison of the BTL flares detected by Fermi-LAT with three on-disk flares and present a study of some of the significant quantities of these flares as an attempt to better understand the acceleration mechanisms at work during these occulted flares. We interpret the HXR emission to be due to electron bremsstrahlung from a coronal thin-target loop top with the accelerated electron spectra steepening at semirelativistic energies. The >100 MeV gamma-rays are best described by a pion-decay model resulting from the interaction of protons (and other ions) in a thick-target photospheric source. In conclusion, the protons are believed to have been accelerated (to energies >10 GeV) in the CME environment and precipitate down to the photosphere from the downstream side of the CME shock and landed on the front side of the Sun, away from the original flare site and the HXR emission.},
doi = {10.3847/1538-4357/835/2/219},
journal = {The Astrophysical Journal (Online)},
number = 2,
volume = 835,
place = {United States},
year = {2017},
month = {1}
}