MHD model of solar penumbral microjet
In order to clarify the magnetic field configuration and associated dynamic process responsible for producing a solar penumbral microjet discovered by Hinode, we constructed a magnetohydrodynamic model of the microjet by utilizing three-dimensional simulation. A twisted flux tube whose inner part (axial component is dominant over azimuthal component) forms magnetic structure of a penumbral filament was placed horizontally in a gravitationally stratified atmosphere with a relatively vertical, background sunspot magnetic field. A key feature of this model is to incorporate an intermediate region between the flux tube and the background field into the model, in which the magnetic configuration smoothly changes from the former to the latter. The simulation showed that magnetic reconnection occurred in the intermediate region to form such plasma jet-like structure as suggested by Hinode's observation. The intermediate region contributed to not only producing the penumbral microjet via reconnection but protecting the magnetic structure of the penumbral filament against the reconnection.
Reference
Magara, T. 2010 ApJ, 715, L40
Inner white field lines (axial component is dominant over azimuthal component) compose magnetic structure of penumbral filament, while outer white field lines and some of the purple field lines surrounding the outer field lines are distributed in intermediate region. The other purple field lines standing relatively vertical represent background sunspot magnetic field.