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The first X-ray imaging spectroscopy of quiescent solar active regions with NuSTAR

Hannah, Iain G. and Grefenstette, Brian W. and Smith, David M. and Glesener, Lindsay and Krucker, Säm and Hudson, Hugh S. and Madsen, Kristin K. and Marsh, Andrew and White, Stephen M. and Caspi, Amir and Shih, Albert Y. and Harrison, Fiona A. and Stern, Daniel and Boggs, Steven E. and Christensen, Finn E. and Craig, William W. and Hailey, Charles J. and Zhang, William W. (2016) The first X-ray imaging spectroscopy of quiescent solar active regions with NuSTAR. Astrophysical Journal Letters, 820 (1). Art. No. L14. ISSN 2041-8205. doi:10.3847/2041-8205/820/1/L14.

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We present the first observations of quiescent active regions (ARs) using NuSTAR, a focusing hard X-ray telescope capable of studying faint solar emission from high temperature and non-thermal sources. We analyze the first directly imaged and spectrally resolved X-rays above 2~keV from non-flaring ARs, observed near the west limb on 2014 November 1. The NuSTAR X-ray images match bright features seen in extreme ultraviolet and soft X-rays. The NuSTAR imaging spectroscopy is consistent with isothermal emission of temperatures 3.1 − 4.4~MK and emission measures 1 – 8 × 10^(46)~cm^(−3). We do not observe emission above 5~MK but our short effective exposure times restrict the spectral dynamic range. With few counts above 6~keV, we can place constraints on the presence of an additional hotter component between 5 and 12~MK of ∼ 10^(46)cm^(−3) and ∼10^(43) cm^(−3), respectively, at least an order of magnitude stricter than previous limits. With longer duration observations and a weakening solar cycle (resulting in an increased livetime), future NuSTAR observations will have sensitivity to a wider range of temperatures as well as possible non-thermal emission.

Item Type:Article
Related URLs:
URLURL TypeDescription Paper
Hannah, Iain G.0000-0003-1193-8603
Grefenstette, Brian W.0000-0002-1984-2932
Smith, David M.0000-0002-0542-5759
Glesener, Lindsay0000-0001-7092-2703
Hudson, Hugh S.0000-0001-5685-1283
Madsen, Kristin K.0000-0003-1252-4891
Marsh, Andrew0000-0003-1086-6900
White, Stephen M.0000-0002-8574-8629
Caspi, Amir0000-0001-8702-8273
Harrison, Fiona A.0000-0003-2992-8024
Stern, Daniel0000-0003-2686-9241
Boggs, Steven E.0000-0001-9567-4224
Christensen, Finn E.0000-0001-5679-1946
Zhang, William W.0000-0002-1426-9698
Additional Information:© 2016 The American Astronomical Society. Received 2016 February 8; accepted 2016 March 2; published 2016 March 16. This paper made use of data from the NuSTAR mission, a project led by the California Institute of Technology, managed by the Jet Propulsion Laboratory, funded by the National Aeronautics and Space Administration. We thank the NuSTAR Operations, Software, and Calibration teams for support with the execution and analysis of these observations. This research made use of the NuSTAR Data Analysis Software (NUSTARDAS) jointly developed by the ASI Science Data Center (ASDC, Italy) and the California Institute of Technology (USA). This work is supported by: NASA grants NNX12AJ36G, NNX14AG07G, IGH (Royal Society University Research Fellowship), AM (NASA Earth Space Science Fellowship, NNX13AM41H), SK (Swiss National Science Foundation, 200021-140308), AC (NASA NNX15AK26G, NNX14AN84G). Thanks to Kim Tolbert for OSPEX help.
Group:NuSTAR, Space Radiation Laboratory
Funding AgencyGrant Number
NASA Earth and Space Science FellowshipUNSPECIFIED
Swiss National Science Foundation (SNSF)200021-140308
Subject Keywords:Sun: X-rays, gamma rays; Sun: activity; Sun: corona
Other Numbering System:
Other Numbering System NameOther Numbering System ID
Space Radiation Laboratory2016-60
Issue or Number:1
Record Number:CaltechAUTHORS:20160318-095344335
Persistent URL:
Official Citation:Iain G. Hannah et al 2016 ApJ 820 L14
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:65477
Deposited By: Melissa Ray
Deposited On:18 Mar 2016 17:53
Last Modified:10 Nov 2021 23:46

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