Joint X-ray, EUV, and UV observations of a small microflare

Hannah, I. G. , Kleint, L., Krucker, S., Grefenstette, B. W., Glesener, L., Hudson, H. S. , White, S. M. and Smith, D. M. (2019) Joint X-ray, EUV, and UV observations of a small microflare. Astrophysical Journal, 881(2), 109. (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 × 1044 cm−3, which corresponds to a thermal energy of 1.5 × 1026 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:Articles
Glasgow Author(s) Enlighten ID:Hannah, Dr Iain and Hudson, Dr Hugh
Authors: Hannah, I. G., Kleint, L., Krucker, S., Grefenstette, B. W., Glesener, L., Hudson, H. S., White, S. M., and Smith, D. M.
College/School:College of Science and Engineering > School of Physics and Astronomy
Journal Name:Astrophysical Journal
Publisher:American Astronomical Society
ISSN (Online):1538-4357
Published Online:20 August 2019
Copyright Holders:Copyright © 2019 The American Astronomical Society
First Published:First published in Astrophysical Journal 881(2): 109
Publisher Policy:Reproduced under a Creative Commons License

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Project CodeAward NoProject NamePrincipal InvestigatorFunder's NameFunder RefLead Dept
617954The many scales of flaring energy release on the SunIain HannahThe Royal Society (ROYSOC)UF120063S&E P&A - PHYSICS & ASTRONOMY
3019350URF RenewalIain HannahThe Royal Society (ROYSOC)URF/R/180010P&S - Physics & Astronomy