The Alfvén mode gyrokinetic equation in finite‐pressure magnetospheric plasma

Klimushkin, D. Yu.; Mager, P. N.

doi:10.1002/2015ja021045

Cited by 13 publications

(10 citation statements)

References 48 publications

(63 reference statements)

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“…The classic KAW is evaluated in the intermediate‐high beta plasma ( m e / m i < β < 1). In the high beta plasma sheet, full effect of plasma pressure should be taken into account when evaluating wave properties [e.g., Denton , ; Dai , ; Klimushkin and Mager , ]. Another effect that may impact the Kinetic Alfven Eigenmode (KAE) property is the effect of field line curvature.…”

Section: Discussionmentioning

confidence: 99%

Evidence of kinetic Alfvén eigenmode in the near‐Earth magnetotail during substorm expansion phase

et al. 2016

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Unipolar pulses of kinetic Alfvén waves (KAW) are first observed in the near‐Earth plasma sheet (NEPS) associated with dipolarizations during substorm expansion phases. Two similar events are studied with Time History of Events and Macroscale Interactions during Substorms (THEMIS) observations during substorms on 3 February 2008 and 7 February 2008. The unipolar pulses were located at a trough‐like Alfvén speed profile in the northern plasma sheet at a distance of 10–11 RE from Earth. The dominant wave components consist of a southward δEz toward the neutral plane and a +δBy toward the dusk. The |δEz|/|δBy| ratio was in the range of a few times the local Alfvén speed, a strong indication of KAW nature. The wave Poynting flux was earthward and nearly parallel to the background magnetic field. The pulse was associated with an earthward field‐aligned current carried by electrons. These observational facts strongly indicate a KAW eigenmode that is confined by the plasma sheet but propagates earthward along the field line. The KAW eigenmode was accompanied by short timescale (1 min) dipolarizations likely generated by transient magnetotail reconnection. The observed polarity of the KAW field/current is consistent with that of the Hall field/current in magnetic reconnection, supporting the scenario that the Hall fields/current propagate out from reconnection site as KAW eigenmodes. Aurora images on the footprint of THEMIS spacecraft suggest that KAW eigenmode may power aurora brightening during substorm expansion phase.

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Section: Discussionmentioning

confidence: 99%

Evidence of kinetic Alfvén eigenmode in the near‐Earth magnetotail during substorm expansion phase

et al. 2016

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“…The accuracy of D E LL estimation relies on the understanding of ULF waves in the inner magnetosphere. The ULF waves are abundant in the inner magnetosphere generated by external sources like the disturbance in the solar wind [Leonovich et al, 2003;Mcpherron, 2005] and internal sources like instabilities and the braking of the earthward high-speed flow in the plasma sheet [Kepko and Kivelson, 1999;Lu et al, 2002;Cao et al, 2008Cao et al, , 2010Yeoman et al, 2012;Dai et al, 2013;Klimushkin and Mager, 2015;Zhou et al, 2015]. With recent improvement on in situ electric field measurements by THEMIS [Angelopoulos, 2008] and Van Allen Probes, ULF wave distributions have been further studied [Liu et al, 2009;Takahashi et al, 2015aTakahashi et al, , 2015bDai et al, 2015].…”

Section: Introductionmentioning

confidence: 99%

On the calculation of electric diffusion coefficient of radiation belt electrons with in situ electric field measurements by THEMIS

Liu

et al. 2016

Geophysical Research Letters

108

220

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Based on 7 years' observations from Time History of Events and Macroscale Interactions during Substorms (THEMIS), we investigate the statistical distribution of electric field Pc5 ULF wave power under different geomagnetic activities and calculate the radial diffusion coefficient due to electric field, DLLE, for outer radiation belt electrons. A simple empirical expression of DLLE[]THEMIS is also derived. Subsequently, we compare DLLE[]THEMIS to previous DLL models and find similar Kp dependence with the DLLE[]CRRES model, which is also based on in situ electric field measurements. The absolute value of DLLE[]THEMIS is constantly higher than DLLE[]CRRES, probably due to the limited orbital coverage of CRRES. The differences between DLLE[]THEMIS and the commonly used DLLM[]normalB‐normalA and DLLE[]Ozeke models are significant, especially in Kp dependence and energy dependence. Possible reasons for these differences and their implications are discussed. The diffusion coefficient provided in this paper, which also has energy dependence, will be an important contributor to quantify the radial diffusion process of radiation belt electrons.

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“…Cheremnykh et al [2014Cheremnykh et al [ , 2016 set up a two-dimensional (2-D) inhomogeneous cylinder model with hot plasma pressure and curved magnetic field and investigated the transverse structure and propagation of high m ULF waves. Klimushkin and Mager [2015] derived an Alfvén mode equation in finite-pressure plasma using the gyrokinetic approach and found that the only wave mode from the solution is the Alfvén-ballooning compressional wave. This wave mode of high m was investigated thoroughly by Chan et al [1994] for a dipole field modified by a small…”

Section: Introductionmentioning

confidence: 99%

Eigenmode analysis of compressional poloidal modes in a self‐consistent magnetic field

et al. 2017

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In this study, we simulate a self‐consistent magnetic field that satisfies force balance with a model ring current that is radially localized, axisymmetric, and has anisotropic plasma pressure. We find that the magnetic field dip forms near the high plasma pressure region with plasma β >∼ 0.6, and the formed magnetic dip becomes deeper for larger plasma β and also slightly deeper for larger anisotropy. We perform linear analysis on a ppol of self‐consistent equilibria for second harmonic compressional poloidal modes of sufficiently high azimuthal wave number. We investigate the effect of anisotropic pressure on the eigenfrequency of the poloidal modes and the characteristics of the compressional magnetic field component. We find that the eigenfrequency is reduced at the outer edge of the thermal pressure peak and increased at the inner edge. The compressional magnetic field component occurs primarily within 10° of the equator on both the inner and outer edges, with stronger compressional magnetic field component on the outer edge. Larger β and smaller anisotropy can increase the change of eigenfrequency and the strength of the compressional magnetic field component. The critical condition on plasma β and pressure anisotropy of an Alfvén ballooning instability is also identified.

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The Alfvén mode gyrokinetic equation in finite‐pressure magnetospheric plasma

Cited by 13 publications

References 48 publications

Evidence of kinetic Alfvén eigenmode in the near‐Earth magnetotail during substorm expansion phase

Evidence of kinetic Alfvén eigenmode in the near‐Earth magnetotail during substorm expansion phase

On the calculation of electric diffusion coefficient of radiation belt electrons with in situ electric field measurements by THEMIS

Eigenmode analysis of compressional poloidal modes in a self‐consistent magnetic field

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