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Evidence of Significant Energy Input in the Late Phase of A Solar Flare from NuSTAR X-Ray ObservationsWe present observations of the occulted active region AR 12222 during the third Nuclear Spectroscopic Telescope ARray (NuSTAR) solar campaign on 2014 December 11, with concurrent Solar Dynamics Observatory (SDO)/ AIA and FOXSI-2 sounding rocket observations. The active region produced a medium-size solar flare 1 day before the observations, at approximately 18 UT on 2014 December 10, with the post-flare loops still visible at the time of NuSTAR observations. The time evolution of the source emission in the SDO/AIA 335 Å channel reveals the characteristics of an extreme-ultraviolet late-phase event, caused by the continuous formation of new post-flare loops that arch higher and higher in the solar corona. The spectral fitting of NuSTAR observations yields an isothermal source, with temperature 3.8-4.6 MK, emission measure (0.3-1.8) × 1046 cm−3, and density estimated at (2.5-6.0) × 108 cm−3. The observed AIA fluxes are consistent with the derived NuSTAR temperature range, favoring temperature values in the range of 4.0-4.3 MK. By examining the post-flare loops' cooling times and energy content, we estimate that at least 12 sets of post-flare loops were formed and subsequently cooled between the onset of the flare and NuSTAR observations, with their total thermal energy content an order of magnitude larger than the energy content at flare peak time. This indicates that the standard approach of using only the flare peak time to derive the total thermal energy content of a flare can lead to a large underestimation of its value.
Document ID
20170006202
Acquisition Source
Goddard Space Flight Center
Document Type
Reprint (Version printed in journal)
Authors
Kuhar, Matej
(Eidgenoessische Technische Hochschule Zurich, Switzerland)
Krucker, Sam
(California Univ. Berkeley, CA, United States)
Hannah, Iain G.
(Glasgow Univ. United Kingdom)
Glesener, Lindsay
(Minnesota Univ. Minneapolis, MN, United States)
Saint-Hilaire, Pascal
(California Univ. Berkeley, CA, United States)
Grefenstette, Brian W.
(California Inst. of Tech. Pasadena, CA, United States)
Hudson, Hugh S.
(California Univ. Berkeley, CA, United States)
White, Stephen M.
(Air Force Research Lab. Albuquerque, NM, United States)
Smith, David M.
(California Univ. Santa Cruz, CA, United States)
Marsh, Andrew J.
(California Univ. Santa Cruz, CA, United States)
Wright, Paul J.
(Glasgow Univ. United Kingdom)
Boggs, Steven E.
(California Univ. Berkeley, CA, United States)
Christensen, Finn E.
(Technical Univ. of Denmark Lyngby, Denmark)
Craig, William W.
(California Univ. Berkeley, CA, United States)
Hailey, Charles J.
(Columbia Univ. New York, NY, United States)
Harrison, Fiona A.
(California Inst. of Tech. Pasadena, CA, United States)
Stern, Daniel
(Jet Propulsion Lab., California Inst. of Tech. Pasadena, CA, United States)
Zhang, William W.
(NASA Goddard Space Flight Center Greenbelt, MD United States)
Date Acquired
July 7, 2017
Publication Date
January 16, 2017
Publication Information
Publication: The Astrophysical Journal
Publisher: The American Astronomical Society
Volume: 835
Issue: 1
ISSN: 0004-637X
e-ISSN: 1538-4357
Subject Category
Astrophysics
Report/Patent Number
GSFC-E-DAA-TN43950
Funding Number(s)
CONTRACT_GRANT: NNX14AG07G
CONTRACT_GRANT: NNX13AM41H
CONTRACT_GRANT: NNX12AJ36G
CONTRACT_GRANT: NNX11AB75G
Distribution Limits
Public
Copyright
Other
Keywords
gamma rays
Sun: flares – Sun: particle emission – Sun: X-rays

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