HESSI--The High Energy Solar Spectroscopic Imager
A solar flare is the rapid release of a large amount of energy stored in
the solar atmosphere. During a flare, gas is heated to 10 to 20 million
degrees Kelvin (K) and radiates soft X-rays and longer-wavelength emission.
Unable to penetrate the Earth's atmosphere, the X-rays can only be detected
from space.
Instruments on Skylab, SMM, the Japanese/US Yohkoh mission and other
spacecraft have recorded many flares in X-rays over the last twenty years
or so. Ground-based observatories have recorded the visible and radio
outputs. These data form the basis of our current understanding of a solar
flare. But there are many possible mechanisms for heating the gas, and
observations to date have not been able to differentiate between them.
Researchers believe that much of the energy released during a flare is used
to accelerate, to very high energies, electrons (emitting primarily X-rays)
and protons and other ions (emitting primarily gamma rays). The new
approach of the HESSI mission is to combine, for the first time,
high-resolution imaging in hard X-rays and gamma rays with high-resolution
spectroscopy, so that a detailed energy spectrum can be obtained at each
point of the image. This new approach will enable researchers to find out
where these particles are accelerated and to what energies. Such
information will advance understanding of the fundamental high-energy
processes at the core of the solar flare problem.
Collaborators
NASA Goddard Space Flight Center, USA; University of Berkeley Space
Science Laboratory, USA; Montana State University, USA; University of
Alabama at Huntsville, USA; Lawrence Berkeley National Laboratory, USA;
National Oceanic and Atmospheric Administration (NOAA), USA; Observatoire
de Paris Meudon, France; ETHZ, Switzerland; Paul Scherrer Institute,
Switzerland; University of Glasgow, Scotland; The University of Tokyo, Japan;
DelftU, The Netherlands
Contact
Gordon D. Holman
Laboratory for Astronomy and Solar Physics
Goddard Space Flight Center (NASA), USA
holman@stars.gsfc.nasa.gov
http://hessi.ssl.berkeley.edu/
http://www.obspm.fr