Plasma diamagnetism and solar coronal activity

Kiyoto Shibasaki

Gyration of charged particles around magnetic lines of force creates ring current. The equivalent magnet is anti-parallel to the surrounding magnetic field. This is the origin of diamagnetism of plasma. The magnetic moment of thermal plasma is proportional to plasma pressure and is inversely proportional to magnetic flux density (M = P/B). When magnetic field has gradient, plasma particles are pushed toward weak field region (F = - M dB/dr). In closed magnetic loops, plasmas are confined around the loop top. In open magnetic field, plasmas are pushed outwards against the gravity. Even in the closed magnetic loop, plasmas tend to get out from the loop top when the plasma beta value is high (high-beta disruption). In general, magnetic field strength decreases outwards; hence plasmas are pushed outwards against gravity by magnetic force. This is the origin of solar coronal activity.

Correspondence

Kiyoto Shibasaki (shibasaki@nro.nao.ac.jp), Nobeyama Solar Radio Observatory

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