University of Maryland and NRL
High-Energy Solar Observations: RHESSI Highlights/Anticipating GLAST
The Ramaty High Energy Solar Spectroscopic Imager (RHESSI) has been in orbit over 5 years. Although launched late in Cycle 23 it has observed over twenty gamma-ray flares, including those occurring during periods of intense solar energetic particle activity in 2003 October, 2005 January, and 2006 December. These observations along with those by other spacecraft and ground-based observatories provide a new view of the conditions in the flaring solar atmosphere and properties of accelerated ions and electrons at the Sun. The RHESSI detectors will be annealed within the next few months in order to repair radiation damage and prepare them for nuclear line observations in Cycle 24. RHESSI will be joined in orbit by the Gamma-ray Large Area Telescope (GLAST) planned for launch in late 2007/early 2008. GLAST provides solar observations from 10 keV to >100 GeV with capability for studying electron bremsstrahlung, nuclear-line radiation, and pion-decay emission. These measurements will allow the spectrum of flare-accelerated particles to be studied up to tens of GeV. Information on solar modulation in the inner heliosphere will be obtained through observations of pion-decay radiation from cosmic-ray proton/alpha-particle interactions at the Sun and by measurements of Compton-scattered sunlight by cosmic-ray electrons.