NG41A-1776
Density fluctuation effects on Langmuir wave propagation
Thursday, 17 December 2015
Poster Hall (Moscone South)
Kyung-Dong Lee, Kyung Hee University, Yongin, South Korea, Eun-Hwa Kim, Princeton Plasma Physics Laboratory, Princeton, NJ, United States, Iver Hugh Cairns, University of Sydney, Sydney, Australia, Paul J Kellogg, University of Minnesota Twin Cities, Minneapolis, MN, United States, Jay Johnson, Princeton University, Plasma Physics Laboratiry, Princeton, NJ, United States and James W Labelle, Dartmouth College, Hanover, NH, United States
Abstract:
Linear mode conversion (LMC) occurs when Langmuir waves propagate in an inhomogeneous medium, so it is important to understand the effects on LMC of the density turbulence typically found in heliospheric plasmas. Although space plasmas typically contain density turbulence with large ranges of length scale L and orientations in 3D, most theoretical and numerical studies have focused on 1D linear density profiles. Other profiles are likely to yield semi-quantitative differences, as found previously for instance by comparing LMC for linear versus parabolic profiles. In this study, we examine the effects of superposing density fluctuations with a range of L onto linear density gradients. Langmuir waves are often observed as wave packets and this can result from short scale, weak, density fluctuations. Such small scale density fluctuations affect the wave propagation characteristics and wavevectors. Moreover, combining a linear density profile with superposed density fluctuations yielded trapped modes and resonant variations in the conversion efficiency. In particular, increased efficiencies are found when integer numbers of Langmuir wavelengths fit within one or more cavities formed by the superposed turbulence).
