Electromagnetic Emission Due to Cyclotron Instability as a Possible Source of Non-Thermal Continuum Radiation in Space Plasmas

0497611 - ÚFA 2019 SG eng A - Abstrakt
Horký, Miroslav - Omura, Y.
Electromagnetic Emission Due to Cyclotron Instability as a Possible Source of Non-Thermal Continuum Radiation in Space Plasmas.
Abstracts of AOGS : 15th Annual Meeting. Singapore: Asia Oceania Geosciences Society, 2018. ST03-D1-PM1-323C-020.
[AOGS Annual Meeting /15./. 03.06.2018-08.06.2018, Honolulu, Hawaii]
Institucionální podpora: RVO:68378289
Klíčová slova: space plasma * non-thermal radiation mechanisms * wave mode conversion * electrostatic wave * electromagnetic wave
Obor OECD: Fluids and plasma physics (including surface physics)
https://www.meetmatt-svr3.net/aogs/aogs2018/mars2/pubViewAbs.asp?sMode=session&sId=180&submit=Browse+Abstracts

Wave mode conversion is a process during which electrostatic wave is converted to electromagnetic wave and vice versa which usually occurs on plasma density gradient or density irregularity. For its description the linear theory is mainly used, however in recent years the numerical simulations governing also non-linear physics became important. Though, in nature most of the processes are not linear, there are not many non-linear studies on this topic. Thus, in this contribution we present a novel model of non-linear wave mode conversion from the electrostatic to the electromagnetic waves.

Specifically, we investigate some kinds of velocity distributions like loss cone distributions which can trigger cyclotron instability generating z-mode waves. Magnetic component of the z-mode wave is perpendicular to the velocity of electrons causing oscillations of Lorentz force in the direction of the external magnetic field Affected electrons then act like antenna generating ordinary electromagnetic wave (O-mode). Because of the non-gyrotropy of velocity distribution, the generated waves contain also harmonics of basic cyclotron frequency. To support proposed theory we perform electromagnetic particle simulations containing density gradient and loss-cone distribution of electrons in the dense area showing emission of electromagnetic waves to the free space.

Similar waves, for instance non-thermal continuum radiation emitted from plasmasphere, are routinely measured in plasmapause by Cluster, Van Allen Probes, and Arase spacecraft. Thus our results might help to understand the origin of the non-thermal continuum radiation.
Trvalý link: http://hdl.handle.net/11104/0290158