Locations of Atmospheric Photoelectron Energy Peaks Within the Mars Environment

Frahm, R. A.; Sharber, J. R.; Winningham, J. D.; Würz, Peter; Liemohn, Michael W.; Kallio, Esa; Yamauchi, M.; Lundin, R.; Barabash, S.; Coates, A. J.; Linder, Dietmar; Kozyra, J. U.; Holmström, Mats; Jeffers, S. J.; Andersson, H.; McKenna-Lawler, S.

doi:10.1007/s11214-006-9119-5

Cited by 86 publications

(70 citation statements)

References 17 publications

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“…It will be shown here that ionospheric electrons are observed in a wide range of altitudes and the boundary of the photoelectrons (PEB) is often located at higher altitudes than it was reported by Mitchell et al (2001) (see also Frahm et al, 2006b). It is not clear yet whether PEB and ionopause are collocated since the lowest energy part of the plasma distribution which primary contributes to the thermal pressure has not been measured yet.…”

Section: Introductionmentioning

confidence: 60%

“…Indeed, the electron spectra within the Martian magnetosphere contain clear signatures of the ionosphere. The peaks in the electron fluxes near ∼20-30 eV appear due to the absorption of the strong solar He II line at 304Å in the carbon dioxide dominated atmosphere of Mars (Mantas and Hanson, 1979;Frahm et al, 2006a). These peaks can be used for tracing of ionospheric photoelectrons.…”

Section: Observationsmentioning

confidence: 99%

“…The ionospheric electrons are observed at altitudes up to ∼7000 km. Statistics of their occurrence at different altitudes is discussed in more detail by Frahm et al (2006b). Another interesting feature is that the photoelectrons are often detected close to the nominal magnetospheric boundary almost filling the whole dayside magnetosphere.…”

Section: Ionospheric Photoelectronsmentioning

confidence: 99%

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Plasma Morphology at Mars. Aspera-3 Observations

et al. 2006

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A total of about of 400 orbits during the first year of the ASPERA-3 operation onboard the Mars Express spacecraft were analyzed to obtain a statistical pattern of the main plasma domains in the Martian space environment. The environment is controlled by the direct interaction between the solar wind and the planetary exosphere/ionosphere which results in the formation of the magnetospheric cavity. Ionospheric plasma was traced by the characteristic "spectral lines" of photoelectrons that make it possible to detect an ionospheric component even far from the planet. Plasma of solar wind and planetary origin was distinguished by the ion mass spectrometry. Several different regions, namely, boundary layer/mantle, plasma sheet, region with ionospheric photoelectrons, ray-like structures near the wake boundary were identified. Upstream parameters like solar wind ram pressure and the direction of the interplanetary electric field were inferred as proxy from the Mars Global Surveyor magnetic field data at a reference point of the magnetic pile up region in the northern dayside hemisphere. It is shown that morphology and dynamics of the main plasma domains and their boundaries are governed by these factors as well as by local crustal magnetizations which add complexity and variability to the plasma and magnetic field environment.

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Section: Introductionmentioning

confidence: 60%

Section: Observationsmentioning

confidence: 99%

Section: Ionospheric Photoelectronsmentioning

confidence: 99%

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Plasma Morphology at Mars. Aspera-3 Observations

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“…While in sunlight, the ELS observes a characteristic dayside ionosphere electron signature with photoelectron peaks near 20 eV observed energy (not corrected for spacecraft potential). These electrons are liberated from the photoionization of atmospheric CO 2 and O by He II 30.4 nm solar photon and are created on the dayside on Mars [Frahm et al, 2006. This kind of photoelectron plasma will be referred to throughout this paper as peaked photoelectron plasma (PPP).…”

Section: Nightside Steep Density Gradientsmentioning

confidence: 99%

Nightside ionosphere of Mars studied with local electron densities: A general overview and electron density depressions

et al. 2011

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The radar sounder Mars Advanced Radar for Subsurface and Ionospheric Sounding (MARSIS) on the Mars Express spacecraft provides local electron densities from electron plasma oscillations. Here, we use the local electron densities to study the nightside ionosphere of Mars. In this study, in which local densities were sampled to a minimum altitude of about 275 km, we measured the maximum average densities as 1000 cm−3 on the nightside. The electron density profiles on the nightside are highly variable. An inverse exponential relationship is observed between the electron density and the altitude. At low altitudes, the median electron density decreases with increasing solar zenith angle (SZA). However, at high altitudes no dependence on SZA is observed. Steep electron density gradients, similar to the ionopause at Venus, are also observed in 15% of the passes in the nightside ionosphere. A commonly encountered structure on the nightside is an ionospheric density depression, which is a deep trough in the electron density. Nightside density depressions are large features, with an average width of 950 km. In some cases, the depressions in MARSIS data are associated with ion flow features in the Analyzer of Space Plasma and Energetic Atoms (ASPERA‐3) data. In other cases, the depressions correspond to density depletion regions. Half of the depressions are aligned with the edge of the dayside‐generated photoelectrons. It is concluded that several different conditions can cause the electron density depressions.

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“…They have been observed in several solar system contexts, including Earth (e.g. Coates et al, 1985), Mars (Frahm et al, 2006a), Titan (e.g. Coates et al, 2007), in Saturn's ring ionosphere (Coates et al, 2005) and in Saturn's inner magnetosphere (Schippers et al, 2009).…”

Section: Introductionmentioning

confidence: 99%

Ionospheric photoelectrons at Venus: Case studies and first observation in the tail

Tsang

Coates

Jones

et al. 2015

Planetary and Space Science

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a b s t r a c tThe presence of photoelectrons in ionospheres, including that of unmagnetised Venus, can be inferred from their characteristic spectral peaks in the electron energy spectrum. The electrons within the peaks are created by the photoionisation of neutrals in the upper atmosphere by the solar HeII 30.4 nm line. Here, we present some case studies of photoelectron spectra observed by the ASPERA-4 instrument aboard Venus Express with corresponding ion data. In the first case study, we observe photoelectron peaks in the sunlit ionosphere, indicating relatively local production. In the second case study, we observe broadened peaks in the sunlit ionosphere near the terminator, which indicate scattering processes between a more remote production region and the observation point. In the third case study, we present the first observation of ionospheric photoelectrons in the induced magnetotail of Venus, which we suggest is due to the spacecraft being located at that time on a magnetic field line connected to the dayside ionosphere at lower altitudes. Simultaneously, low energy ions are observed moving away from Venus. In common with observations at Mars and at Titan, these imply a possible role for the relatively energetic electrons in producing an ambipolar electric field which enhances ion escape.

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Locations of Atmospheric Photoelectron Energy Peaks Within the Mars Environment

Cited by 86 publications

References 17 publications

Plasma Morphology at Mars. Aspera-3 Observations

Plasma Morphology at Mars. Aspera-3 Observations

Nightside ionosphere of Mars studied with local electron densities: A general overview and electron density depressions

Ionospheric photoelectrons at Venus: Case studies and first observation in the tail

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