Penetration of a radio frequency electromagnetic field into a magnetized plasma: one-dimensional PIC simulation studies

Fumiko Otsuka,Takao Tanikawa,Tohru Hada,Shunjiro Shinohara

doi:10.1186/s40623-015-0244-9

Abstract

Penetration of a radio frequency (rf) electromagnetic field into a magnetized plasma is discussed by performing one-dimensional particle-in-cell (PIC) simulations. We consider two models: an electrostatic (ES) model using an external rf voltage and an electromagnetic (EM) model using an external rf current. The background magnetic field is perpendicular to the one-dimensional system. In the ES model, the external rf voltage across the plasma produces the rf electric field into the plasma. When ω rf =Ω e /2, where ω rf and Ω e are the externally applied field and electron gyrofrequencies, respectively, the ion-rich sheath is formed due to the electron wall loss caused by the electron polarization drift. When ω rf =ω LH /2, where ω LH is the lower hybrid frequency, the electron-rich sheath is formed due to the ion wall loss caused by its larger gyroradius than the electron. In the EM model, an induced electromagnetic field via the external rf current forms a standing wave in the plasma region bounded by the external antennas. When the diameter of the plasma is equal to the wave length, the spatial/temporal profiles of the rf standing waves are well explained by a cold collisionless plasma linear theory except for the existence of the sheath. When the rf magnetic field is increased to 10 % of the background magnetic field, the waveforms become irregular and complex because of the boundary effects.

Highlights

Wave penetration into a plasma is an important problem from the point of view of a fundamental physics and from numerous applications in various fields such as plasma production (Shinohara and Shamrai 2002; Shinohara et al 2009) plasma heating, and confinement (Shoji 1980)
We examined the ponderomotive acceleration (PA) combined with the ion cyclotron resonance (ICR) using the test particle simulations (Otsuka et al 2013a, 2013b)
For applications to various types of electrodeless plasma thrusters in general, we investigate the rf electric field penetration by performing one-dimensional particlein-cell (PIC) simulations

Summary

Introduction

Wave penetration into a plasma is an important problem from the point of view of a fundamental physics and from numerous applications in various fields such as plasma production (Shinohara and Shamrai 2002; Shinohara et al 2009) plasma heating, and confinement (Shoji 1980). In which the radio frequency (rf ) electric field penetration is essential, Otsuka et al Earth, Planets and Space (2015) 67:85 are the Lissajous Helicon Plasma Accelerator (LHPA) (Matsuoka et al 2012; Nakamura et al 2012; Nishida et al 2012), the Variable Specific Impulse Magnetoplasma Rocket (VASIMR) (Ando et al 2005, 2006; Bering III et al 2010), and the Ponderomotive Acceleration/Ion Cyclotron Resonance (PA/ICR) (Otsuka et al 2013a, 2013b). In our test particle simulations, the rf electromagnetic fields are assumed to be present inside the plasma This may well be an optimistic simplification because the plasma in general acts to shield the external waves from penetrating inside. For applications to various types of electrodeless plasma thrusters in general, we investigate the rf electric field penetration by performing one-dimensional particlein-cell (PIC) simulations

Methods

Results

Discussion

Conclusion