The Sun is the closest star to Earth and hence provides a unique opportunity to study numerous stellar phenomena in detail unprecedented to other stars. One such phenomena, which is a longstanding mystery, is coronal heating of low mass stars. The solar corona contains plasma in excess of 1 MK at all times, strong concentrations of magnetic field called active region contain plasma at least up to 3 MK, and large flares heat plasma above 10 MK. The distribution of temperatures, elemental abundance, and time scales of each phenomena, provide unique insights on the various types of coronal heating processes. Currently, there are very few in-situ measurements of coronal plasma near the Sun (the solar wind provides an additional probe), thus radiative diagnostics are commonly used.
Detection of soft X-rays (sxr) from the Sun provide direct information on coronal plasma of temperatures in excess of ~1 MK, but there have been relatively few solar spectrally resolved measurements from 0.5 – 10. keV. CubeSats, SmallSats, and Sounding Rockets can be low-cost alternatives to rapidly fill astrophysical observation gaps, that large missions are currently missing. The twin Miniature X-ray Solar Spectrometer (MinXSS) and Dual Aperture X-ray Solar Spectrometer (DAXSS) CubeSats have provided measurements from 0.8 -12 keV, with resolving power ~40 or greater at 5.9 keV, at a nominal ~10 second time cadence. Quiescent solar coronal measurements by MinXSS and DAXSS constrain plasma temperatures to further isolate the dominate coronal heating mechanisms. MinXSS and DAXSS spectra allow for determining coronal abundance variations for Fe, Mg, Ni, Ca, Si, S, and Ar in active regions and during flares.
Future improvements in solar soft X-ray spectroscopy can be achieved by combining Miniature X-ray Optics (MiXO) with high speed readout CMOS detectors for spectral imaging, improved dynamic range, and improved spectral resolution. These new prospects on a funded NASA Sounding Rocket instrument and a potential future SmallSat will also be discussed.
Host: Gabor Furesz
Subset of Relevant Publication Links:
Relevant Web Links:
NASA Press Release: MinXSS CubeSat Brings New Information to Study of Solar Flares
NASA ScienceCasts: Small Satellites yield Big Discoveries
MinXSS Data Videos
MinXSS CubeSat – Solar Physics
SSAXI SmallSat – SmallSat Conference