Numerical Simulation of Vertical Current Sheets in Solar Chromospheric Plasma with the Hall Effect

Аннотация

The consequences of the entry of the magnetic field from underlying layers into the Sun’s chromosphere are studied via numerical solution of the 2D MHD problem (with constant physical quantities along the straight horizontal magnetic lines of force). Chromospheric plasma is considered to be collisional; its Joule dissipation and the Hall effect are taken into account. The initial magnetic field is characterized by a value of β = 1.5 and corresponds to an upward current sheet of finite thickness. There are cases in which the coevolution of the magnetic field and plasma leads to the formation of a very thin, vertical current sheet, from which a plasma stream flows downward vertically. The process turned out to be typical of rather large heights, where the influence of the Hall effect on the magnetic field evolution begins to exceed the field-drift effect due to the (partial) freezing of the force lines. The formed thin current sheet then ceases to exist under the action of pinch (sausage and/or kink) instabilities. The reconnection of force lines is not seen under the conditions of this numerical experiment due to the assumed constancy of physical quantities (including velocity) along a force line. Accordingly, the described processes in nature will act as alternative or additional processes with respect to the typically considered scenarios of reconnection.