H ?filtergram observations of ellerman bombs and its magnetic reconnection model

Abstract

From theHαfiltergram observations obtained at Ganyu station, identification and statistic works made for Ellerman bombs, it is found that they often occur in the superpenumbra area of a mature sunspot. We suggest a plasmoid model to account for the basic properties of a typical bomb: lifetime 11 min, diameter ∼ 5 × 107 cm, accompanying jet velocity ∼ 40 km/s, total energy ∼ 1027 erg,Te ∼ 104 K. First, a numerical simulation is made to prove that plasmoids can be lifted from the solar convective zone by magnetic buoyancy. Between the plasmoid and its surroundings a strong current sheet builds up in which a peculiar MHD (with plasma ponderamotive force) - resistive instability takes place. After the magnetic reconnection has begun, a local explosive instability ensues whose growth rate is so high that it allows the exhaustion of the ‘high temperature’ particles from the sheet in a short period. In this way, the temperature of a bomb may be kept unchanged or only rise slightly.