Growth rates of the ion cyclotron instability in the magnetosphere

Märk, E.

doi:10.1029/ja079i022p03218

Cited by 35 publications

(14 citation statements)

References 11 publications

(5 reference statements)

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“…The EMIC instability appears to be a likely candidate in driving the heat flux into the ionosphere as well as having some role in the generation of the equatorial heating of the plasmasphere [ Cornwall et al , 1971; Khazanov et al , 2003]. General consensus is that the instability is probably active in the PBL when the ratio of hot to cold ion density is on the order of 0.01 [e.g., see Cornwall et al , 1970; Märk , 1974]. Since the R HC values in the figures only contain the He + density, is it necessary to include the H + contribution into the ratio before a comparison can be made between the predicted R HC for strong EMIC growth and the range observed in which the heat flux is generated.…”

Section: Discussionmentioning

confidence: 99%

Overlap of the plasmasphere and ring current: Relation to subauroral ionospheric heating

Gurgiolo¹,

Sandel

Perez

et al. 2005

J. Geophys. Res.

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[1] The overlap of the ring current with the outer plasmasphere is thought to play a major role in storm-time related increases in the subauroral ambient topside electron temperature. Instabilities generated within the overlap region, Coulomb collisions of plasmaspheric electrons with the ring current ions, and charge exchange are all thought to work either individually or together to generate a downward heat flux into the ionosphere to produce the increase in temperature. Analysis of IMAGE two-dimensional ring current and plasmasphere density maps together with in situ DMSP ambient electron temperature data shows that the heating generally occurs over a small radial extent within the plasmasphere/ ring current overlap region and may be significantly earthward of the plasmapause. This argues against collisional heat conduction as the source of the heat flux and for an instability-based process. The finding that the heating occurs within well-defined ratios of the cold plasmasphere to hot ring current density strengthens this supposition.

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Section: Discussionmentioning

confidence: 99%

Overlap of the plasmasphere and ring current: Relation to subauroral ionospheric heating

Gurgiolo¹,

Sandel

Perez

et al. 2005

J. Geophys. Res.

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“…Since ER is inversely proportional to the plasma density, an increase of N leads to a decrease of the resonant energy. This is basically the argument that has led Cornwall [1972] and many others (see, for instance, Mark [1974] and Cuperman et al [1975]) to conclude that ion cyclotron waves can only be destabilized inside the plasmasphere. Assuming that ICWs have random phases, Kennel and Petschek [1966] and Gendrin [1968] have used quasi-linear type equations to describe the saturation of ICWs.…”

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confidence: 80%

Wave‐particle interactions near Ω_He+ observed on board GEOS 1 and 2: 2. Generation of ion cyclotron waves and heating of He⁺ ions

Roux¹,

Perraut²,

Rauch³

et al. 1982

J. Geophys. Res.

235

188

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This work is a continuation of paper 1 (Young et al., 1981) and is devoted to the generation process of ion cyclotron waves (ICWs) and the acceleration of He+ ions up to suprathermal energies. Simultaneous measurements are used from the ion composition experiment (0 < E < 16 keV), the energetic particle experiment (24 < E < 3 300 keV), and the ULF wave experiment (0.2–10 Hz) on board the GEOS 1 and GEOS 2 spacecraft. General characteristics of the local time distribution of ICWs will be presented and compared with those of the thermal anisotropy of energetic protons and the He+ abundance. Further calculations of the convective growth rate are conducted by applying two different methods, both of which are based upon the measured proton fluxes. The generation conditions of the ICWs in the presence of He+ ions will be investigated and three possible explanations will be discussed: (1) enhanced convection growth rates, (2) lowering of the threshold for absolute instabilities, and (3) change of the ICWs ray path (laser‐like effect). Finally, it is shown that the flux of suprathermal He+ ions is modulated at the ICW frequency. Owing to nonlinear effects, part of the energy of the energetic protons is transfered via the ICWs to the He+ ions that are essentially accelerated in the direction perpendicular to the static magnetic field. Then in the otherwise collisionless plasma the friction between energetic anisotropic protons and thermal He+ ions is achieved through the ICWs.

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“…A good estimation of the relaxation time for the ion cyclotron instability should probably relate to the bouncing period of the particles travelling along the field lines. For sake of simplicity we approximate the growth rate based on observations in the magnetosphere [ Anderson et al , 1996] and theories [ Märk , 1974; Gary et al , 1993, 1995] as

τ_{italicic} = \frac{10^{2}}{Ω_{i}} .

…”

Section: Methodsmentioning

confidence: 99%

Pressure anisotropy in global magnetospheric simulations: A magnetohydrodynamics model

et al. 2012

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[1] In order to better describe the space plasmas where pressure anisotropy has prominent effects, we extend the BATS-R-US magnetohydrodynamics (MHD) model to include anisotropic pressure. We implement the anisotropic MHD equations under the double adiabatic approximation with an additional pressure relaxation term into BATS-R-US and perform global magnetospheric simulations. The results from idealized magnetospheric simulations confirm previous studies: pressure anisotropy widens the magnetosheath, increases the density depletion in the vicinity of the magnetopause, enhances the nightside plasma pressure, and introduces an eastward ring current. In addition, we find that the flow speed in the magnetotail is significantly reduced by including pressure anisotropy in MHD simulations. Our model is validated through comparing the simulations to the THEMIS data on both the dayside and nightside of the magnetosphere during quiet times. The comparison to the results from isotropic MHD simulations implies that although anisotropic MHD is comparable to isotropic MHD in matching the measurement, it improves the simulated plasma velocity in some cases.

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Growth rates of the ion cyclotron instability in the magnetosphere

Abstract: Growth rates of the ion cyclotron instability in the magnetosphere are calculated, including the corrections coming from finite proton and electron temperatures. The effect of (artificial) injection of cold plasma with different ion masses is discussed in detail.

Cited by 35 publications

References 11 publications

Overlap of the plasmasphere and ring current: Relation to subauroral ionospheric heating

Overlap of the plasmasphere and ring current: Relation to subauroral ionospheric heating

Wave‐particle interactions near Ω_He+ observed on board GEOS 1 and 2: 2. Generation of ion cyclotron waves and heating of He⁺ ions

Pressure anisotropy in global magnetospheric simulations: A magnetohydrodynamics model

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Growth rates of the ion cyclotron instability in the magnetosphere

Abstract: Growth rates of the ion cyclotron instability in the magnetosphere are calculated, including the corrections coming from finite proton and electron temperatures. The effect of (artificial) injection of cold plasma with different ion masses is discussed in detail.

Cited by 35 publications

References 11 publications

Overlap of the plasmasphere and ring current: Relation to subauroral ionospheric heating

Overlap of the plasmasphere and ring current: Relation to subauroral ionospheric heating

Wave‐particle interactions near ΩHe+ observed on board GEOS 1 and 2: 2. Generation of ion cyclotron waves and heating of He+ ions

Pressure anisotropy in global magnetospheric simulations: A magnetohydrodynamics model

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Wave‐particle interactions near Ω_He+ observed on board GEOS 1 and 2: 2. Generation of ion cyclotron waves and heating of He⁺ ions