Finite Larmor radius effects in the magnetosphere

Stasiewicz, K.

doi:10.1007/bf00754509

Cited by 26 publications

(16 citation statements)

References 107 publications

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“…A spatially localized source would launch a broad Akñ spectrum. The spatial structuring of the source region could be possibly related to the fundamental mechanism for splitting of accelerated magnetospheric flows [Stasiewicz, 1994], which would lead to establishment of structures with thickness smaller than the direct ion gyroradius. The launched waves would propagate along the ray path given by (2), within the resonance cone (4).…”

mentioning

confidence: 99%

Cavity resonators and Alfvén resonance cones observed on Freja

Stasiewicz¹,

Gustafsson²,

Marklund³

et al. 1997

J. Geophys. Res.

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mentioning

confidence: 99%

Cavity resonators and Alfvén resonance cones observed on Freja

Stasiewicz¹,

Gustafsson²,

Marklund³

et al. 1997

J. Geophys. Res.

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“…Transport of momentum across the layers is also provided by ions with larger gyroradius without any magnetic field annihilation. The momentum transfer has been discussed by Stasiewicz (1994) in terms of gyro-viscosity, which in the case of anti-parallel magnetic fields predicts a forcing of the boundary Earthward without a macro-reconnection. The ratio of the normal to MP gyroviscous stress to Maxwell stresses is ∼βρ u /2d, where ρ u is directional gyroradius and d -the MP width.…”

Section: Discussionmentioning

confidence: 99%

“…In this case the frozen-in condition for ions is violated due to the small current scale, it could be also described in terms of an effective viscosity (see e.g. Stasiewicz, 1994). Belmont and Rezeau, (2001) show similar effects of Alfven waves on the magnetic flux erosion and use the term 'micro-reconnection' in contrast to a stationary laminar reconnection with the Xline configuration (see Sibeck et al, 1999).…”

Section: Small-scale Electrodynamicsmentioning

confidence: 99%

“…Previous studies of data from Interball-1, Polar and Cluster (Nikutowski et al, 1998(Nikutowski et al, , 1999Mozer et al, 2003a;Vaivads et al, 2004) have been mostly limited to the comparison with models of stationary X-line macro reconnection. In the TCS the frozen-in condition is violated due to the small current scale, which can be described not only in reconnection-like approximations, but also in terms of gyroviscosity (Stasiewicz, 1994;Sibeck et al, 1999). Belmont and Rezeau (2001) use the term "micro reconnection" for similar effects of Alfven waves on the magnetic flux erosion.…”

Section: Introductionmentioning

confidence: 99%

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Experimental study of nonlinear interaction of plasma flow with charged thin current sheets: 2. Hall dynamics, mass and momentum transfer

Savin

Amata

André

et al. 2006

Nonlin. Processes Geophys.

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Abstract.Proceeding with the analysis of Amata et al. (2005), we suggest that the general feature for the local transport at a thin magnetopause (MP) consists of the penetration of ions from the magnetosheath with gyroradius larger than the MP width, and that, in crossing it, the transverse potential difference at the thin current sheet (TCS) is acquired by these ions, providing a field-particle energy exchange without parallel electric fields. It is suggested that a part of the surface charge is self-consistently produced by deflection of ions in the course of inertial drift in the nonuniform electric field at MP.Consideration of the partial moments of ions with different energies demonstrates that the protons having gyroradii of roughly the same size or larger than the MP width carry fluxes normal to MP that are about 20% of the total flow in the plasma jet under MP. This is close to the excess of the ion transverse velocity over the cross-field drift speed in the plasma flow just inside MP (Amata et al., 2005), which conforms to the contribution of the finite-gyroradius inflow across MP. A linkage through the TCS between different plasmas results from the momentum conservation of the Correspondence to: S. Savin (ssavin@iki.rssi.ru) higher-energy ions. If the finite-gyroradius penetration occurs along the MP over ∼1.5 R E from the observation site, then it can completely account for the formation of the jet under the MP. To provide the downstream acceleration of the flow near the MP via the cross-field drift, the weak magnetic field is suggested to rotate from its nearly parallel direction to the unperturbed flow toward being almost perpendicular to the accelerated flow near the MP.We discuss a deceleration of the higher-energy ions in the MP normal direction due to the interaction with finite-scale electric field bursts in the magnetosheath flow frame, equivalent to collisions, providing a charge separation. These effective collisions, with a nonlinear frequency proxy of the order of the proton cyclotron one, in extended turbulent zones are a promising alternative in place of the usual parallel electric fields invoked in the macro-reconnection scenarios. Further cascading towards electron scales is supposed to be due to unstable parallel electron currents, which neutralize the potential differences, either resulted from the ion-burst interactions or from the inertial drift.The complicated MP shape suggests its systematic velocity departure from the local normal towards the average one, inferring domination for the MP movement of the non-local processes over the small-scale local ones.Published by Copernicus GmbH on behalf of the European Geosciences Union and the American Geophysical Union. The measured Poynting vector indicates energy transmission from the MP into the upstream region with the waves triggering impulsive downstream flows, providing an input into the local flow balance and the outward movement of the MP.Equating the transverse electric field inside the MP TCS by the Hall term in the Ohm's law ...

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“…mum, the electron orbit becomes larger than the gradient scale length of the field, ͉B/ٌB͉Ӎ4 cm. Large Larmor radius effects reduce the cross-field drifts 19,20 and change wave-particle interactions, 21,22 which can quench the instability. During the saturated instability, the observed density enhancements are smaller than the density depressions.…”

Section: F Particle Trajectoriesmentioning

confidence: 99%

Electron magnetohydrodynamic turbulence in a high-beta plasma. III. Conditionally averaged multipoint fluctuation measurements

Stenzel

Urrutia

2000

Physics of Plasmas

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A large discharge plasma is generated whose electron pressure exceeds that of an external magnetic field. A magnetic cavity exists in the plasma interior. The ions are unmagnetized while the electron magnetization varies from complete to none. In the region of pressure and field gradients a strong instability is observed. It is a cross-field instability driven by the electron diamagnetic drift through the unmagnetized ions, creating large density and magnetic field fluctuations near the lower hybrid frequency that propagate at the sound speed in the diamagnetic drift direction. The basic plasma parameters leading to the instability have been presented in Part I of three companion papers. Spectra, correlations, amplitude distributions, and magnetic hodograms derived from single-point fluctuation measurements have been presented in Part II. These led to the discovery of density cavities and current sheet formation by nonlinear wave steepening. The present Part III deals with multipoint fluctuation measurements using on-line conditional averaging, which resolves the structure of typical fluctuations in space and time. Propagation velocity and coherence of the flutelike density perturbations is measured. The topology of the magnetic fluctuations and associated current density is investigated and shown to consist of flux ropes of negative self-helicities. Superposition of the nonuniform mean field and fluctuating fields yields the net field and current density. Instantaneous field lines and magnitude distributions in three-dimensional space are presented for a turbulent high-beta plasma. The results suggest that the demagnetization of electrons in large positive density fluctuations provides a new saturation mechanism for the instability.

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Finite Larmor radius effects in the magnetosphere

Cited by 26 publications

References 107 publications

Cavity resonators and Alfvén resonance cones observed on Freja

Cavity resonators and Alfvén resonance cones observed on Freja

Experimental study of nonlinear interaction of plasma flow with charged thin current sheets: 2. Hall dynamics, mass and momentum transfer

Electron magnetohydrodynamic turbulence in a high-beta plasma. III. Conditionally averaged multipoint fluctuation measurements

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