Ion temperature enhancement in the wakes of ionospheric spacecraft

Samir, Uri; Israelevich, P. L.; Wright, K. H.; Stone, N. H.

doi:10.1029/2000ja000198

Cited by 3 publications

(2 citation statements)

References 22 publications

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“…In cold but rarefied, unbounded collisionless space plasmas, probes may be biased highly positive [3], with recent theoretical developments for new applications [4,5]. Ionospheric experiments have found particles heated in the plasma beyond probe [6,7] or spacecraft [8] sheaths.…”

Section: Introductionmentioning

confidence: 99%

New books on physics and related sciences

Zakharova¹

2002

Phys.-Usp.

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The electron-retarding range of the current-voltage characteristic of a flat Langmuir probe perpendicular to a strong magnetic field in a fully ionized plasma is analysed allowing for anomalous (Bohm) cross-field transport and temperature changes in the collection process. With probe size and ion thermal gyroradius comparable, and smaller than the electron mean free path, there is an outer quasineutral region with ion viscosity determinant in allowing nonambipolar parallel and cross flow. A potential overshoot lying either at the base or inside the quasineutral region both makes ions follow Boltzmann's law at negative bias and extends the electron-retarding range to probe bias eφ P ∼ +2T ∞ . Electron heating and cooling occur roughly at positive and negative bias, with a T e -minimum around eφ P ∼ −2T ∞ ; far from the probe heat conduction cools and heats electrons at and radially away from the probe axis, respectively. The potential overshoot with no thermal effects would reduce the electron current I e , making the ln I e versus φ P graph downwards-concave, but cooling further reduces I e substantially, and may tilt the slope upwards past the temperature minimum. The domain of strict validity of our analysis is narrow in case of low ion mass (deuterium), breaking down with the ion Boltzmann law.

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Section: Introductionmentioning

confidence: 99%

New books on physics and related sciences

Zakharova¹

2002

Phys.-Usp.

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“…A number of space, laboratory experiments and theoretical studies were made with the aim to investigate the plasma sheath formation and its structure, which depends on a number of parameters, such as geometry, size and potential of body, surface materials, Debye length, Mach number, plasma composition, density and energy of the charged particles, etc. Singh et al (1987) and Samir et al (2001) demonstrated that the electrons and ions are heated in the wake, while Siskind et al (1984) also observed an electron heating in the ram direction. Henderson and Samir (1967) measured the current depletion in the wake with respect to the ram and Samir et al (1979 studied the asymmetry in the current distribution in the wake.…”

Section: Introductionmentioning

confidence: 99%

The spherical segmented Langmuir probe in a flowing thermal plasma: numerical model of the current collection

Seran¹,

Berthelier²,

Saouri³

et al. 2005

Ann. Geophys.

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Abstract. The segmented Langmuir probe (SLP) has been recently proposed by one of the authors (Lebreton, 2002) as an instrument to derive the bulk velocity of terrestrial or planetary plasmas, in addition to the electron density and temperature that are routinely measured by Langmuir probes. It is part of the scientific payload on the DEMETER microsatellite developed by CNES. The basic concept of this probe is to measure the current distribution over the surface using independent collectors under the form of small spherical caps and to use the angular anisotropy of these currents to obtain the plasma bulk velocity in the probe reference frame. In order to determine the SLP capabilities, we have developed a numerical PIC (Particles In Cell) model which provides a tool to compute the distribution of the current collected by a spherical probe. Our model is based on the simultaneous determination of the charge densities in the probe sheath and on the probe surface, from which the potential distribution in the sheath region can be obtained. This method is well adapted to the SLP problem and has some advantages since it provides a natural control of the charge neutrality inside the simulation box, allows independent mesh sizes in the sheath and on the probe surface, and can be applied to complex surfaces. We present in this paper initial results obtained for plasma conditions corresponding to a Debye length equal to the probe radius. These plasma conditions are observed along the Demeter orbit. The model results are found to be in very good agreement with those published by Laframboise (1966) for a spherical probe in a thermal nonflowing plasma. This demonstrates the adequacy of the computation method and of the adjustable numerical parameters (size of the numerical box and mesh, time step, number of macro-particles, etc.) for the considered plasma-probe configuration. We also present the results obtained in the case of plasma flowing with mesothermal conditions reproducing the case of measurements onboard a low altitude spacecraft. Finally, we briefly discuss the capabilities of the SLP to deCorrespondence to: E. Séran (seran@cetp.ipsl.fr) duce the plasma bulk velocity under similar conditions and present the first onboard measurements.

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Electron cooling in probe collection from magnetized plasmas with anomalous transport

Charro¹,

Sanmartin²

2002

Plasma Phys. Control. Fusion

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The electron-retarding range of the current-voltage characteristic of a flat Langmuir probe perpendicular to a strong magnetic field in a fully ionized plasma is analysed allowing for anomalous (Bohm) cross-field transport and temperature changes in the collection process. With probe size and ion thermal gyroradius comparable, and smaller than the electron mean free path, there is an outer quasineutral region with ion viscosity determinant in allowing nonambipolar parallel and cross flow. A potential overshoot lying either at the base or inside the quasineutral region both makes ions follow Boltzmann's law at negative bias and extends the electron-retarding range to probe bias e(j)p ~ +2Too. Electron heating and cooling occur roughly at positive and negative bias, with a r e -minimum around efa ~ -27^; far from the probe heat conduction cools and heats electrons at and radially away from the probe axis, respectively. The potential overshoot with no thermal effects would reduce the electron current I e , making the In I e versus 4>p graph downwards-concave, but cooling further reduces I e substantially, and may tilt the slope upwards past the temperature minimum. The domain of strict validity of our analysis is narrow in case of low ion mass (deuterium), breaking down with the ion Boltzmann law.

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Ion temperature enhancement in the wakes of ionospheric spacecraft

Cited by 3 publications

References 22 publications

New books on physics and related sciences

New books on physics and related sciences

The spherical segmented Langmuir probe in a flowing thermal plasma: numerical model of the current collection

Electron cooling in probe collection from magnetized plasmas with anomalous transport

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