Subject will be restored when possible |
|
Arnold O. Benz Submitted: 2008-02-26 11:45
Solar flares are observed at all wavelengths from decameter radio waves to gamma-rays at 100 MeV. This review focuses on recent observations in EUV, soft and hard X-rays, white light and radio waves. Space missions such as RHESSI, Yohkoh, TRACE, and SOHO have enlarged widely the observational base. They have revealed a number of surprises: Coronal sources appear before the hard X-ray emission in chromospheric footpoints, major flare acceleration sites appear to be independent of coronal mass ejections (CMEs), electrons and ions may be accelerated at different sites, and basic characteristics vary from small to large flares. Recent progress also includes improved insights into the flare energy partition, on the location(s) of energy release, tests of energy release scenarios and
particle acceleration. The interplay of observations with theory is important to deduce the geometry and to disentangle the various processes involved. There is increasing evidence supporting reconnection of magnetic
field lines as the basic cause. While this process has become generally accepted as the trigger, it does not explain the huge energy involved, nor the impulsive acceleration of charged particles. Flare-like processes may
be responsible for large-scale restructuring of the magnetic field in the corona as well as for its heating. Large flares influence interplanetary space and substantially affect the Earth's lower ionosphere. While flare scenarios have slowly converged over the past decades, every new observation still reveals major unexpected results, demonstrating that solar flares, after 150 years since their discovery, remain an unexplained problem of astrophysics.
Authors: Arnold O. Benz
Projects: None
|
Publication Status: published in Living Reviews in Solar Physics (2008)
Last Modified: 2008-09-23 21:22
|
 
 
 
 
|
|