Model calculations of the dayside ionosphere of Venus: Energetics

Cravens, T. E.; Gombosi, T. I.; Kozyra, J. U.; Nagy, Andrew F.; Brace, L. H.; Knudsen, W. C.

doi:10.1029/ja085ia13p07778

Cited by 105 publications

(59 citation statements)

References 30 publications

(6 reference statements)

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“…If the gyroradius of a particle is less than the correlation length, then its effective mean free path can be taken to be approximately the correlation length, A. If, on the other hand, the gyroradius is considerably larger than A, then the mean free path can be assumed to be of the order of the gyroradius [Cravens et al, 1980] …”

Section: Introductionmentioning

confidence: 99%

Effect of the magnetic field on the energetics of Mars ionosphere

Choi

Kim²,

Kang

et al. 1998

Geophysical Research Letters

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Abstract.The coupled, one-dimensional electron and ion energy equations, with a combination of small steady and fluctuating horizontal magnetic fields imposed, are solved for the Mars ionosphere, corresponding to conditions encountered during the Viking mission. A series of calculations with various boundary conditions and heat sources result in a range of electron and ion temperature profiles, which are compared with the results obtained by the RPA's carried aboard the Viking landers. It is shown that solar EUV heating alone does not lead to the observed temperature profiles and that assuming reasonable heat fluxes at the top result in good agreement. It is also found that the introduction of small steady and altitude dependent fluctuating horizontal magnetic fields, which modify the thermal conductivity, leads to electron temperatures in reasonably good agreement with the RPA data, but does not match the observed ion temperatures above about 240 kin. The effects of chemical and Joule heating are also examined and found not to be significant.

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Section: Introductionmentioning

confidence: 99%

Effect of the magnetic field on the energetics of Mars ionosphere

Choi

Kim²,

Kang

et al. 1998

Geophysical Research Letters

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“…Below this altitude, downward cascade from 20 eV to lower energies is more effective than that from higher energies to 20 eV, while it is less effective above that altitude. A similar transition region from local equilibrium to transport dominance has been found in previous model calculations of the suprathermal electron population in the Venus ionosphere [e.g., Cravens et al, 1980], though the exact location of the transition region varies with the adopted input parameters.…”

Section: Effect Of Transportmentioning

confidence: 55%

“…Along with these early PVO RPA in situ observations, various modeling efforts have been devoted into this topic [e.g., McCormick et al, 1976;Butler and Stolarski, 1978;Cravens et al, 1980;Gan et al, 1990], mostly concentrated on the overall shape and magnitude of suprathermal electron spectrum as well as the associated thermal electron heating rate. More recently, the suprathermal electron intensity on Venus has been acquired from measurements made with the Electron Spectrometer (ELS) of the Analyzer of Space Plasmas and Energetic Atoms (ASPERA-4) onboard Venus Express (VEx) [Barabash et al, 2007].…”

Section: Introductionmentioning

confidence: 99%

Suprathermal electron spectra in the Venus ionosphere

et al. 2011

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[1] In this study, a multistream kinetic model is used to derive the suprathermal electron intensity in the Venus ionosphere, to be compared with the observations made by the Analyzer of Space Plasmas and Energetic Atoms (ASPERA-4) Electron Spectrometer (ELS) instrument onboard Venus Express (VEx) on 18 May 2006. Input parameters of the model are chosen to be consistent with the detailed ephemeris information. We consider two cases for the magnetic field line configuration. The first assumes vertical magnetic field lines, while in the second the configuration is consistent with the VEx Magnetometer (MAG) measurements for that particular orbit. The model calculations suggest that the energy spectrum of suprathermal electrons not only depends on the local photoelectron production but is also strongly influenced by transport as well as energy degradation. We confirm the postulation of Coates et al. (2008) (2008). The model results indicate that the condition of local equilibrium is satisfied for suprathermal electrons below ∼155 km on Venus. However, transport becomes effective at higher altitudes, significantly altering the secondary electron production rate and leading to strongly anisotropic suprathermal electron flow. For the case with the MAG-derived, slanted magnetic field configuration, we make a data-model comparison in terms of both the absolute magnitude of the suprathermal electron intensity and the appearance of spectral peaks. The comparison suggests that the actual magnetic field lines are probably inclined more vertically than a simple extrapolation from the MAG measurements.

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“…The use of the expression for thermal conductivity, appropriate for a fully ionized gas, appears to be inappropriate for model calculations. The fluctuation of the magnetic field in the Mars ionosphere and/or the presence of a horizontal magnetic field can reduce the heat conduction (Hoegy et al, 1990;Cravens et al, 1980). The assumption of such a modified thermal conductivity can be studied by means of d.c. and fluctuating magnetic field data which will be provided by the magnetometer and the wave receiver onboard "NOZOMI".…”

Section: Scientific Objectivesmentioning

confidence: 99%

Electron temperature probe onboard Japan’s Mars orbiter

Oyama

Abe

Schlegel³

et al. 2014

Earth Planet Sp

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Japan' s first Mars spacecraft PLANET-B was successfully launched on 4th of July, 1998 and was named "NO-ZOMI" after the launch. One of the scientific instruments is a unique electron temperature probe which was developed in Japan and has been used for more than 20 years on sounding rockets as well as on scientific satellites (Oyama, 1991). The electron temperature probe dubbed PET (Probe for Electron Temperature measurements) consists of two planar electrodes, 150 mm in diameter, placed at the edges of the two solar cell panels of the "NOZOMI" spacecraft. Electron temperatures can be measured in plasmas with densities exceeding 1000 cm −3 with sufficient accuracy. The maximum sampling rate of 8 data points per satellite spin for each probe allows high resolution measurements (i.e., an angular resolution around the spin axis of 23 degrees). Additionally, the probe can measure the anisotropy of the electron temperature, if it exists. It is also possible to infer the existence of nonthermal electrons.

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Model calculations of the dayside ionosphere of Venus: Energetics

Cited by 105 publications

References 30 publications

Effect of the magnetic field on the energetics of Mars ionosphere

Effect of the magnetic field on the energetics of Mars ionosphere

Suprathermal electron spectra in the Venus ionosphere

Electron temperature probe onboard Japan’s Mars orbiter

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