Preprint article · Journal article
The first X-ray imaging spectroscopy of quiescent solar active regions with NuSTAR
University of Glasgow1
Astrophysics and Atmospheric Physics, National Space Institute, Technical University of Denmark2
Lawrence Livermore National Laboratory3
Columbia University4
California Institute of Technology5
University of California at Santa Cruz6
University of Minnesota Twin Cities7
University of California at Berkeley8
Air Force Research Laboratory9
Southwest Research Institute10
NASA Goddard Space Flight Center11
National Space Institute, Technical University of Denmark12
...and 2 moreWe present the first observations of quiescent active regions (ARs) using the Nuclear Spectroscopic Telescope Array (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 × 1046 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∼1046 cm−3 and ∼1043cm−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.
Language: | English |
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Publisher: | American Astronomical Society |
Year: | 2016 |
Pages: | L14 |
ISSN: | 20418213 and 20418205 |
Types: | Preprint article and Journal article |
DOI: | 10.3847/2041-8205/820/1/L14 |
ORCIDs: | Christensen, Finn Erland |