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The turbulence evolution in the high β region of the Earth's foreshock
Author(s) -
Li Huimin,
Pang Ye,
Huang Shiyong,
Zhou Meng,
Deng Xiaohua,
Yuan Zhigang,
Wang Dedong,
Li HaiMeng
Publication year - 2013
Publication title -
journal of geophysical research: space physics
Language(s) - English
Resource type - Journals
eISSN - 2169-9402
pISSN - 2169-9380
DOI - 10.1002/2013ja019424
Subject(s) - physics , instability , polarization (electrochemistry) , cascade , computational physics , energy cascade , foreshock , plasma , wavenumber , turbulence , mechanics , optics , geology , chemistry , chromatography , seismology , aftershock , quantum mechanics
In this paper, we study the foreshock turbulence evolution in high β region via both Cluster observation on 29 March 2002 and 1‐D hybrid simulation. The quasi‐sinusoidal and the irregular wave trains are both detected in this event. The former one is believed to be generated by ion‐ion right‐hand nonresonant instability due to the right‐hand polarization and antisunward propagation in the plasma frame. Since the ion distribution associated with the wave train is more “intermediate” rather than “diffused”, we suggest that the wave train reported in this paper can be viewed as a “midstep” of “isolated” and “irregular”. From the quasi‐sinusoidal to the irregular waveform, the corresponding polarizations appear to transit: right‐hand wave of higher frequency (wave number) is substituted by a left‐hand wave with lower frequency (wave number) in spacecraft frame. Then the 1‐D hybrid simulation is applied for two cases with various velocities to study such polarization transition. By comparing observation results with the simulation, such polarization transition and “inversed cascade” (wave energy transferring from large wave number to small wave number) can be understood as the consequence of decay instability. Although decay instability cannot be initiated in high beta ( β > 1) plasma in magnetohydrodynamic theory, such β dependence can be modified by ion kinetic effect. Moreover, it is found that in simulation no matter which right‐hand instability is dominant in early stage, left‐hand wave will be the prime component of magnetic field disturbance in the final stage.