The Mechanism and Efficiency of Magnetic Field Inflating by Plasma Jets

Abstract

In this study, We analyzed the magnetic field inflation by a low Alfvenic plasma jet from the center region of dipole magnetic field using ideal magnetohydrodynamic simulation. The plasma jet is assumed to be chocked at the nozzle exit, and four simulations were conducted by changing Alfven Mach number at the nozzle exit; 0.3, 0.1, 0.03 and 0.01. When the Alfven Mach number of plasma flow becomes higher, it was found that the plasma flow drags the magnetic field in the radial direction. As a result, the magnetic field is inflated to stronger magnetic field and we found two kinds of magnetic field region; the open magnetic field region where the plasma flows outward with dragging the magnetic field; the other is the closed magnetic field region where the plasm can not flow because the flow is trapped by the storong magnetic field. When the Alfven Mach number at the nozzle exit becomes lower, although the structure of flow field and the strength of inflated magnetic field do not change considerably, the sub Alfvenic flow area gets larger; it is therefore clarified that plasma jets at Alfven Mach number of 10−5 creates a sub Alfvenic flow field of several kilometers in radius. This magnetic field inflation is the essential process for Magneto Plasma Sail to produce thrust.