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Joint X-ray, EUV and UV Observations of a Small Microflare

Hannah, Iain G. and Kleint, Lucia and Krucker, Säm and Grefenstette, Brian W. and Glesener, Lindsay and Hudson, Hugh S. and White, Stephen M. and Smith, David M. (2019) Joint X-ray, EUV and UV Observations of a Small Microflare. Astrophysical Journal, 881 (2). Art. No. 109. ISSN 1538-4357. doi:10.3847/1538-4357/ab2dfa.

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We present the first joint observation of a small microflare in X-rays with the Nuclear Spectroscopic Telescope ARray (NuSTAR), in UV with the Interface Region Imaging Spectrograph (IRIS), and in EUV with the Solar Dynamics Observatory/Atmospheric Imaging Assembly (SDO/AIA). These combined observations allow us to study the hot coronal and cooler chromospheric/transition region emission from the microflare. This small microflare peaks from 2016 July 26 23:35 to 23:36 UT, in both NuSTAR, SDO/AIA, and IRIS. Spatially, this corresponds to a small loop visible in the SDO/AIA Fe XVIII emission, which matches a similar structure lower in the solar atmosphere seen by IRIS in SJI1330 and 1400 Å. The NuSTAR emission in both 2.5–4 and 4–6 keV is located in a source at this loop location. The IRIS slit was over the microflaring loop, and fits show little change in Mg II but do show intensity increases, slight width enhancements, and redshifts in Si IV and O IV, indicating that this microflare had most significance in and above the upper chromosphere. The NuSTAR microflare spectrum is well fitted by a thermal component of 5.1 MK and 6.2 × 10^(44) cm^(−3), which corresponds to a thermal energy of 1.5 × 10^(26) erg, making it considerably smaller than previously studied active region microflares. No non-thermal emission was detected but this could be due to the limited effective exposure time of the observation. This observation shows that even ordinary features seen in UV can remarkably have a higher-energy component that is clear in X-rays.

Item Type:Article
Related URLs:
URLURL TypeDescription Paper
Hannah, Iain G.0000-0003-1193-8603
Grefenstette, Brian W.0000-0002-1984-2932
Glesener, Lindsay0000-0001-7092-2703
Hudson, Hugh S.0000-0001-5685-1283
White, Stephen M.0000-0002-8574-8629
Smith, David M.0000-0002-0542-5759
Additional Information:© 2019 The American Astronomical Society. Original content from this work may be used under the terms of the Creative Commons Attribution 3.0 licence. Any further distribution of this work must maintain attribution to the author(s) and the title of the work, journal citation and DOI. Received 2018 December 21; revised 2019 June 20; accepted 2019 June 28; published 2019 August 20. 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). IRIS is a NASA small explorer mission developed and operated by LMSAL with mission operations executed at NASA Ames Research center and major contributions to downlink communications funded by ESA and the Norwegian Space Centre. I.G.H. is supported by a Royal Society University Fellowship. The authors thank the International Space Science Institute (ISSI) for support for P. Testa's team "New Diagnostics of Particle Acceleration in Solar Coronal Nanoflares from Chromospheric Observations and Modeling," where this work benefited from productive discussions. Facilities: NuSTAR - The NuSTAR (Nuclear Spectroscopic Telescope Array) mission, IRIS - , SDO/AIA - , GOES. -
Group:NuSTAR, Space Radiation Laboratory
Funding AgencyGrant Number
Subject Keywords:Sun: activity – Sun: corona – Sun: transition region – Sun: UV radiation – Sun: X-rays, gamma rays
Issue or Number:2
Record Number:CaltechAUTHORS:20190814-073445942
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Official Citation:Iain G. Hannah et al 2019 ApJ 881 109
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:97866
Deposited By: Tony Diaz
Deposited On:14 Aug 2019 16:49
Last Modified:16 Nov 2021 17:34

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