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Title: Effects of a random spatial variation of the plasma density on the mode conversion in cold, unmagnetized, and stratified plasmas

We study the effects of a random spatial variation of the plasma density on the mode conversion of electromagnetic waves into electrostatic oscillations in cold, unmagnetized, and stratified plasmas. Using the invariant imbedding method, we calculate precisely the electromagnetic field distribution and the mode conversion coefficient, which is defined to be the fraction of the incident wave power converted into electrostatic oscillations, for the configuration where a numerically generated random density variation is added to the background linear density profile. We repeat similar calculations for a large number of random configurations and take an average of the results. We obtain a peculiar nonmonotonic dependence of the mode conversion coefficient on the strength of randomness. As the disorder increases from zero, the maximum value of the mode conversion coefficient decreases initially, then increases to a maximum, and finally decreases towards zero. The range of the incident angle in which mode conversion occurs increases monotonically as the disorder increases. We present numerical results suggesting that the decrease of mode conversion mainly results from the increased reflection due to the Anderson localization effect originating from disorder, whereas the increase of mode conversion of the intermediate disorder regime comes from the appearance of manymore » resonance points and the enhanced tunneling between the resonance points and the cutoff point. We also find a very large local enhancement of the magnetic field intensity for particular random configurations. In order to obtain high mode conversion efficiency, it is desirable to restrict the randomness close to the resonance region.« less
Authors:
 [1] ;  [2]
  1. School of Space Research, Kyung Hee University, Yongin 446-701 (Korea, Republic of)
  2. Department of Energy Systems Research, Ajou University, Suwon 443-749 (Korea, Republic of)
Publication Date:
OSTI Identifier:
22218314
Resource Type:
Journal Article
Resource Relation:
Journal Name: Physics of Plasmas; Journal Volume: 20; Journal Issue: 12; Other Information: (c) 2013 AIP Publishing LLC; Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
70 PLASMA PHYSICS AND FUSION TECHNOLOGY; 71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSICS; ELECTROMAGNETIC FIELDS; ELECTROMAGNETIC RADIATION; INVARIANT IMBEDDING; MAGNETIC FIELDS; MODE CONVERSION; NUMERICAL ANALYSIS; OSCILLATIONS; PLASMA DENSITY; PLASMA RADIAL PROFILES; PLASMA WAVES; RANDOMNESS; VARIATIONS