Opportunities for Solar Science with NuSTAR
Abstract
While NuSTAR was designed to observe faint cosmic sources in hard X-rays (HXR), its unprecedented sensitivity can also be used to address several outstanding questions in high energy solar physics. Medium- and large-sized solar flares have been well -studied in HXR by the Reuven Ramaty High Energy Solar Spectroscopic Imager (RHESSI), launched in 2002. These flares are always found in active regions and usually emit nonthermal HXR from accelerated electrons, along with thermal bremsstrahlung as those electrons lose their energy and heat the ambient plasma. To date, no HXR flares outside active regions have been observed, though thermal brightenings in soft X-rays and EUV suggest that small "nanoflares" may occur frequently across the entire solar disk, even at quiet times when no active regions are present. Even a few minutes of NuSTAR solar observations will allow a search for HXR from quiet-Sun nanoflares with better sensitivity than any previous study. These observations will have important implications for the role of flares in supplying the corona with its surprisingly hot temperature (1--2 MK, as compared with the photospheric temperature of 5800 K). NuSTAR will also make the first observations of escaping flare electrons associated with Type III radio emission, can image faint coronal sources in partially occulted flares that are below RHESSI's sensitivity, and, combined with RHESSI data, could study the faint, earliest phase of flares, where direct signatures of particle acceleration are most likely to be observed.
- Publication:
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American Astronomical Society Meeting Abstracts #221
- Pub Date:
- January 2013
- Bibcode:
- 2013AAS...22124423G