Main Objective:
Measure flare-temperature plasma and/or accelerated electron distribution in the quiescent corona.
Scientific Justification:
The proposed observations are in support of the upcoming launch of NASA’s FOXSI (Focusing Optics X-ray Solar Imager) sounding rocket. FOXSI will provide hard X-ray imaging observations in the 5-20 keV range at a 50 times improved sensitivity compared to RHESSI. This will allow us to investigate the low-level hard X-ray emission that is predicted in some coronal heating scenarios, and/or by nanoflares. The launch date is August 21, 2018. During the 6-minute FOXSI flight, an active region (if available) and the quiet Sun will be observed. The FOXSI field-of-few is 16x16 arcmin.
Coronal heating is one of the main unsolved problems in Heliophysics. Low-level energy releases at high occurrence rates (so-called nanoflares) are one of the proposed mechanisms to heat the corona. Results from the previous FOXSI-2 rocket flight included a direct observation of 10 MK plasma in a quiescent region (Ishikawa et al. 2017; Nature Astronomy). We aim for a second measurement of such plasma in our third flight, with an upgraded instrument including a photon-counting soft X-ray imager. For the quiet Sun, we will measure or set new upper limits on the hard X-rays produced by hot plasma and/or accelerated electrons. |
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