Electron acceleration to high energies at quasi-parallel shock waves in the solar corona

In the solar corona shock waves are generated by flares and/or coronal mass ejections. They manifest themselves in solar type II radio bursts appearing as emission stripes with a slow drift from high to low frequencies in dynamic radio spectra. Their nonthermal radio radiation indicates that electrons are accelerated to suprathermal and/or relativistic velocities at these shocks. As well known by extraterrestrial in-situ measurements supercritical, quasi-parallel, collisionless shocks are accompanied by so-called SLAMS (short large amplitude magnetic field structures). These SLAMS can act as strong magnetic mirrors, at which charged particles can be reflected and accelerated. Thus, thermal electrons gain energy due to multiple reflections between two SLAMS and reach suprathermal and relativistic velocities. This mechnism of accelerating electrons is discussed for the solar corona and may be responsible for the so-called 'herringbones' observed in solar type II radio bursts. (orig.)Available from TIB Hannover / FIZ - Fachinformationszzentrum Karlsruhe / TIB - Technische InformationsbibliothekSIGLEDEGerman

Catalogue of solar type II radio bursts observed from September 1990 to December 1993 and their statistical analysis

Solar type II radio bursts represent the radio signature of shock waves travelling through the solar corona. They are associated with flares, coronal mass ejections (CME's) and interplanetary shocks. Type II radio bursts appear as emission stripes slowly drifting from high to low frequencies in dynamic radio spectra. The spectral features of all solar type II radio bursts observed by the new radiospectrograph of the Astrophysikalisches Institut Potsdam in Tremsdorf during the time period from September 1, 1990 to December 31, 1993, i.e., during the first part of the ULYSSES spacecraft mission, are summarized and statistically investigated. (orig.)Available from TIB Hannover / FIZ - Fachinformationszzentrum Karlsruhe / TIB - Technische InformationsbibliothekSIGLEDEGerman