The expansion of a plasma into a vacuum: Basic phenomena and processes and applications to space plasma physics

Samir, Uri; Wright, K. H.; Stone, N. H.

doi:10.1029/rg021i007p01631

Cited by 171 publications

(150 citation statements)

References 63 publications

(66 reference statements)

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“…plasma betas, sonic and Alfvénic numbers etc.). Additionally, as within Saturn's plasmasphere the ion and electron thermal velocities are comparable or much higher than the plasma bulk velocity, the refilling of the wake should happen in a very close distance behind the moon (Samir et al, 1983). That is important as with a close flyby, both the structure of the wake and the processes refilling it can be monitored.…”

Section: Introductionmentioning

confidence: 99%

“…Such interactions have been studied extensively for supersonic plasma flows, using spacecraft observations, theory, numerical and laboratory simulations (e.g. Halekas et al, 2005;Kallio, 2005;Travnicek et al, 2005;Farrell et al, 1997;Ogilvie et al, 1996;Samir et al, 1983;Podgorny et al, 1982;Podgorny and Andrijanov, 1978;Dubinin et al, 1977;Whang and Ness, 1970;Whang, 1969). Khurana et al (2008) and Roussos et al (2007) have studied such interactions in the the subsonic plasma flows in Saturn's magnetosphere, using magnetic field and energetic electron Published by Copernicus Publications on behalf of the European Geosciences Union.…”

Section: Introductionmentioning

confidence: 99%

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Plasma and fields in the wake of Rhea: 3-D hybrid simulation and comparison with Cassini data

et al. 2008

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Abstract. Rhea's magnetospheric interaction is simulated using a three-dimensional, hybrid plasma simulation code, where ions are treated as particles and electrons as a massless, charge-neutralizing fluid. In consistency with Cassini observations, Rhea is modeled as a plasma absorbing obstacle. This leads to the formation of a plasma wake (cavity) behind the moon. We find that this cavity expands with the ion sound speed along the magnetic field lines, resulting in an extended depletion region north and south of the moon, just a few Rhea radii (R Rh ) downstream. This is a direct consequence of the comparable thermal and bulk plasma velocities at Rhea. Perpendicular to the magnetic field lines the wake's extension is constrained by the magnetic field. A magnetic field compression in the wake and the rarefaction in the wake sides is also observed in our results. This configuration reproduces well the signature in the Cassini magnetometer data, acquired during the close flyby to Rhea on November 2005. Almost all plasma and field parameters show an asymmetric distribution along the plane where the corotational electric field is contained. A diamagnetic current system is found running parallel to the wake boundaries. The presence of this current system shows a direct corelation with the magnetic field configuration downstream of Rhea, while the resulting j×B forces on the ions are responsible for the asymmetric structures seen in the velocity and electric field vector fields in the equatorial plane. As Rhea is one of the many plasma absorbing moons of Saturn, we expect that this case study should be relevant for most lunar-type interactions at Saturn.

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Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Plasma and fields in the wake of Rhea: 3-D hybrid simulation and comparison with Cassini data

et al. 2008

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“…However, there are many kinetic processes that cannot be described by fluid models, e.g., the non-Maxwellian particle populations in the wake region, so particle models should capture more of the physical processes. An approximation of the refill of the lunar wake is the general one-dimensional problem where plasma expands into a vacuum (Widner et al, 1971;Samir et al, 1983;Mora, 2003), and such models have specifically been applied to the refill of the lunar wake (Farrell et al, 1998;Birch and Chapman, 2001). A nice property of such models is that even if they are one-dimensional, they can to some degree approximate a two-dimensional model of the lunar wake, where time corresponds to distance downstream the wake, i.e., the one-dimensional model is applied perpendicular to the solar wind flow and convects with the flow.…”

Section: Introductionmentioning

confidence: 99%

The interaction between the Moon and the solar wind

et al. 2012

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We study the interaction between the Moon and the solar wind using a three-dimensional hybrid plasma solver. The proton fluxes and electromagnetical fields are presented for typical solar wind conditions with different magnetic field directions. We find two different wake structures for an interplanetary magnetic field that is perpendicular to the solar wind flow, and for one that is parallell to the flow. The wake for intermediate magnetic field directions will be a mix of these two extreme conditions. Several features are consistent with a fluid interaction, e.g., the presence of a rarefaction cone, and an increased magnetic field in the wake. There are however several kinetic features of the interaction. We find kinks in the magnetic field at the wake boundary. There are also density and magnetic field variations in the far wake, maybe from an ion beam instability related to the wake refill. The results are compared to observations by the WIND spacecraft during a wake crossing. The model magnetic field and ion velocities are in agreement with the measurements. The density and the electron temperature in the central wake are not as well captured by the model, probably from the lack of electron physics in the hybrid model.

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“…The Debye sheath is well understood. Wake potential gradients have been described theoretically by self-simular plasma expansion 58 and have been observed experimentally. 52 Unlike previous studies, ions in this system are magnetized ( i ϽR).…”

Section: Discussionmentioning

confidence: 99%

Ion acceleration and anomalous transport in the near wake of a plasma limiter

1997

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Ion acceleration and anomalous transport were studied experimentally in the near wake region of an electrically floating disk limiter immersed in two different types of collisionless, supersonically flowing, magnetized plasmas: the first initially quiescent, the second initially turbulent. Ion densities and velocity distributions were obtained using a nonperturbing laser induced fluorescence diagnostic. Large-amplitude, low-frequency turbulence was observed at the obstacle edge and in the wake. Rapid ion and electron configuration space transport and ion velocity space transport were observed. Configuration space and velocity space transport were similar for both quiescent and turbulent plasma-obstacle systems, suggesting that plasma-obstacle effects outweigh the effects of initial plasma turbulence levels.

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The expansion of a plasma into a vacuum: Basic phenomena and processes and applications to space plasma physics

Cited by 171 publications

References 63 publications

Plasma and fields in the wake of Rhea: 3-D hybrid simulation and comparison with Cassini data

Plasma and fields in the wake of Rhea: 3-D hybrid simulation and comparison with Cassini data

The interaction between the Moon and the solar wind

Ion acceleration and anomalous transport in the near wake of a plasma limiter

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