Modeling Penumbral Microjets by Two-Fluid Simulations

Abstract

We investigate how penumbral microjets, recently observed by the Hinode satellite, can be produced within sunspot penumbra. We consider two penumbral filaments with axial currents and axial flows. We assume that a vertical magnetic flux tube exists between two horizontal penumbral filaments. We also assume that the axial flows are not steady; a high-velocity axial flow is imposed on the background slow axial flow. We find that this high-velocity axial flow can trigger magnetic reconnection between one penumbral filament and the vertical flux tube. As a result, inclined bidirectional jetlike flows, driven by the magnetic reconnection, propagate along the vertical magnetic flux tube. Strong proton heating, up to 25 times their original temperature, is observed in these generated jets. Conversely, the neutral-hydrogen particles are only very weakly heated. We propose that these plasma jets explain the phenomenon of penumbral microjets, recently observed by the Hinode satellite.