NuSTAR Observation of a Minuscule Microflare in a Solar Active Region.

Autor: Cooper K; School of Physics & Astronomy, University of Glasgow, Glasgow G12 8QQ, UK., Hannah IG; School of Physics & Astronomy, University of Glasgow, Glasgow G12 8QQ, UK., Grefenstette BW; Cahill Center for Astrophysics, 1216 East California Boulevard, California Institute of Technology, Pasadena, CA 91125, USA., Glesener L; School of Physics & Astronomy, University of MinnesotaTwin Cities, Minneapolis, MN 55455, USA., Krucker S; University of Applied Sciences and Arts Northwestern Switzerland, 5210 Windisch, Switzerland.; Space Sciences Laboratory University of California, Berkeley, CA 94720, USA., Hudson HS; School of Physics & Astronomy, University of Glasgow, Glasgow G12 8QQ, UK.; Space Sciences Laboratory University of California, Berkeley, CA 94720, USA., White SM; Air Force Research Laboratory, Space Vehicles Directorate, Kirtland AFB, NM 87123, USA., Smith DM; Santa Cruz Institute of Particle Physics and Department of Physics, University of California, Santa Cruz, CA 95064, USA.
Jazyk: angličtina
Zdroj: The astrophysical journal. Letters [Astrophys J Lett] 2020 Apr 20; Vol. 893 (2). Date of Electronic Publication: 2020 Apr 22.
DOI: 10.3847/2041-8213/ab873e
Abstrakt: 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 1.1 × 10 26 erg. It reaches temperatures of 6.7 MK with an emission measure of 8.0 × 10 43 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.
Databáze: MEDLINE
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