Generation of kinetic Alfvén waves by upper-hybrid pump waves

Abstract

The nonlinear mechanism for kinetic-Alfvén-wave (KAW) excitation by upper-hybrid waves (UHWs) is discussed. Taking into account perpendicular dispersion of KAWs, caused by effects of finite ion Larmor radius and electron inertia, we examine a new channel for UHW decay, in which a pump UHW decays into another UHW and an ultralow-frequency wave, KAW: UHW→KAW+UHW. A nonlinear dispersion relation is derived, and the growth rate of the parametric decay instability is calculated for a pump UHW propagating at an arbitrary angle to the background magnetic field. We find that the resulting KAWs often have a two-peaked spectrum with different perpendicular dispersions. Using satellite observations, the analytical results are applied to show that the considered process represents an effective mechanism for KAW generation and the consequent spreading of the UHW spectrum in the Earth's magnetosphere and solar corona.

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“…Ïîñëåäíåå aeå ïðè îïðåäåëåííûõ äîïîëíèòåëüíûõ óñëîâèÿõ [9,14,15,18,19,23,48,50,51,54] ìîaeåò îáðàçîâàòü âñïëåñê èçëó÷åíèÿ â ìèêðîâîëíîâîì äèàïàçîíå, ÿâëÿþùèéñÿ ÷àùå âñåãî ïðåäâåñòíèêîì âñïûøêè â àêòèâíîé îáëàñòè (ÀÎ) [15,17,23,34,48,57]. Ñòîèò îñîáî îòìåòèòü, ÷òî ÊÀ è ÊÈÇ çàìå÷àòåëüíû íå òîëüêî òåì, ÷òî ÿâëÿþòñÿ íåèçìåííûìè ó÷àñòíèêàìè áîëüøèíñòâà òðåõâîëíîâûõ ïðîöåññîâ [51,[54][55][56], íî è ñàìè ïî ñåáå îáëàäàþò òàêèìè çàìå÷àòåëüíûìè ñâîéñòâàìè, êàê ðàñïàäíûé ñïåêòð [5,28,29] è ñîáñòâåííîå («ïðîäîëüíîå») ýëåêòðè÷åñêîå ïîëå [28,29], êîòîðîå ïîçâîëÿåò èì ýôôåêòèâíî ó÷àñòâîâàòü â ïðîöåññå óñêîðåíèÿ ÷àñòèö [45]. Ýòè âîëíû òàêaeå âåñüìà ýôôåêòèâíû â ïðîöåññå âîçíèêíîâåíèÿ â ïëàçìå àíîìàëüíîãî ñîïðîòèâëåíèÿ è íàãðåâàíèÿ ñðåäû [2-4, 12, 14, 28, 29].…”

Oblique Bernstein Mode Generation Near the Upper-hybrid Frequency in Solar Pre-flare Plasmas

“…Alexandrov, Bogdankevich, and Rukhadze, 1984). Yukhimuk et al (1998) have shown that the parametric decay of the upper-hybrid pump wave (UHW) into a kinetic Alfvén wave (KAW) and an EMW is possible in the solar atmosphere, i.e.,…”

Kinetic Alfvén waves in plasmas with heavy ions

“…Since the pioneer work of Hasegawa and Chen 3 in 1975, the KAW has been applied extensively to various energization phenomena of plasma particles, such as tokamak plasma heating in the laboratory, 4,5 the flare plasma energization, 6,7 the plasma heating of solar coronal loops and plumes, 8,9 and the auroral electron acceleration in space plasmas. [10][11][12] Meanwhile, the generation of KAWs by various linear [13][14][15][16][17][18] and nonlinear [19][20][21][22][23] mechanisms has been diffusely studied.…”