Cooper, K. , Hannah, I. , Grenfenstette, B. W., Glesener, L., Krucker, S., Hudson, H. , White, S. and Smith, D. M. (2020) NuSTAR observation of a minuscule microflare in a solar active region. Astrophysical Journal Letters, 893(2), L40. (doi: 10.3847/2041-8213/ab873e)
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Abstract
We present X-ray imaging spectroscopy of one of the weakest active region (AR) microflares ever studied. The microflare occurred at ∼11:04 UT on 2018 September 9 and we studied it using the Nuclear Spectroscopic Telescope ARray (NuSTAR) and the Solar Dynamic Observatory's Atmospheric Imaging Assembly (SDO/AIA). The microflare is observed clearly in 2.5-7 keV with NuSTAR and in Fe XVIII emission derived from the hotter component of the 94 Å SDO/AIA channel. We estimate the event to be three orders of magnitude lower than a GOES A class microflare with an energy of 1.1e26 erg. It reaches temperatures of 6.7 MK with an emission measure of 8.0e43 cm^−3. Non-thermal emission is not detected but we instead determine upper limits to such emission. We present the lowest thermal energy estimate for an AR microflare in literature, which is at the lower limits of what is still considered an X-ray microflare.
Item Type: | Articles (Letter) |
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Status: | Published |
Refereed: | Yes |
Glasgow Author(s) Enlighten ID: | Hudson, Dr Hugh and Hannah, Dr Iain and Cooper, Mr Kristopher |
Authors: | Cooper, K., Hannah, I., Grenfenstette, B. W., Glesener, L., Krucker, S., Hudson, H., White, S., and Smith, D. M. |
Subjects: | Q Science > QB Astronomy |
College/School: | College of Science and Engineering > School of Physics and Astronomy |
Journal Name: | Astrophysical Journal Letters |
Publisher: | American Astronomical Society |
ISSN: | 2041-8205 |
ISSN (Online): | 2041-8213 |
Copyright Holders: | Copyright © 2020 The American Astronomical Society |
First Published: | First published in Astrophysical Journal Letters 893(2):L40 |
Publisher Policy: | Reproduced in accordance with the publisher copyright policy |
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