München 2019 – wissenschaftliches Programm

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EP: Fachverband Extraterrestrische Physik

EP 1: Sun and Heliosphere I

EP 1.6: Vortrag

Montag, 18. März 2019, 18:00–18:15, HS 19

Shock accelerated electron beams in the solar corona — •Gottfried Mann — Leibniz-Institut fuer Astrophysik Potsdam, Potsdam, Deutschland

In the solar corona shock waves can be generated either by the blast wave due to a flare or driven ahead of a coronal mass ejection (CME). Such shocks are observed as solar type II bursts in the solar radio radiation indicating the generation of energetic electrons at these shock. The radio emission at shocks are regarded to be plasma emission, i.e. the energetic electrons excite Langmuir waves due to beam-plasma interaction. These Langmuir waves convert into escaping radio waves as a result of nonlinear plasma processes This mechanism requires that the velocity of energetic electrons must necessarily exceed 4 times the thermal electron speed. Assuming shock drift acceleration as the mechanism for producing energetic electrons at shocks a beam-like electron velocity distribution function is established in the upstream region of the shock. Such electron beams are really observed in the solar radio radiation in terms of herringbones as fine structures in type II radio bursts. The observational data can be explained in the best way, if the shock propagates nearly perpendicular to the ambient magnetic field. That is the case at the flanks of shocks driven by a CME.