Electron pitch angle distributions as indicators of magnetic field topology near Mars

Brain, David; Lillis, Robert J.; Mitchell, David; Halekas, J. S.; Lin, R. P.

doi:10.1029/2007ja012435

Cited by 168 publications

(358 citation statements)

References 41 publications

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“…Corresponding auroral emissions above these crustal magnetization regions has indeed also been observed [Bertaux et al, 2005;Leblanc et al, 2008]. Furthermore, and as noted by Lundin et al [2006], acceleration and outflow of ionospheric ions occurs primarily on what appears to be the boundary between open and closed magnetic field lines [Brain et al, 2007] attached to the crustal field. Auroral acceleration at Mars is in this respect similar to that over the Earth's discrete aurora [see, e.g., Paschmann et al, 2002, and references therein].…”

Section: Introductionmentioning

confidence: 75%

“…While the northern hemisphere O + flow tracks the external flow, the southern hemisphere behaves like an additional obstacle with flow vectors pointing perpendicular to the external flow. The southern polar cap (dashed circle) is characterized Brain et al, 2007]. In the further analysis of O + outflow we have binned the data in three 120°wide longitude sectors as indicated by (1), (2), and (3).…”

Section: Measurement Resultsmentioning

confidence: 99%

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On the relation between plasma escape and the Martian crustal magnetic field

Lundin

Barabash

Yamauchi

et al. 2011

Geophys. Res. Lett.

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[1] Data from ASPERA-3 on Mars Express is used to study the geographic distribution of ionospheric O + outflow and escape from Mars. Of particular interest is how the ion outflow relates to the crustal magnetic field regions facing the dayside, flank, and nightside of Mars. The most intense O + fluxes are generated on the dayside at altitudes below ≈1000 km, peaking over the southern hemisphere in the longitude sector 120°-250°. This sector coincides with the strongest crustal magnetic field regions at Mars. On the other hand, the correspondence between dayside and nightside O + fluxes is weak, i.e. the tailward transport of dayside O + ions is apparently inhibited. This suggests that most ionospheric O + ions on crustal magnetic field lines remain on the dayside. The dayside "mini-magnetospheres" developed acts as cellular structures recycling ionospheric plasma and reducing the tailward transport and escape of ionospheric plasma. Further support for this is that the O + flow over the southern hemisphere deviates strongly from the tailward northern hemisphere flow, leading to eddy structures over the southern polar cap. Citation: Lundin, R., S. Barabash, M. Yamauchi, H. Nilsson, and D. Brain (2011), On the relation between plasma escape and the Martian crustal magnetic field,

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Section: Introductionmentioning

confidence: 75%

Section: Measurement Resultsmentioning

confidence: 99%

On the relation between plasma escape and the Martian crustal magnetic field

Lundin

Barabash

Yamauchi

et al. 2011

Geophys. Res. Lett.

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“…The extent and variability of the Martian ionosphere was investigated by Mitchell et al (2001) using the electron observations on Mars Global Surveyor. Analyzing the shape of electron pitch-angle distributions Brain et al (2007) have inferred a topology of magnetic field lines. Brain et al (2007) could distinguish between closed, open and draped field lines.…”

Section: Introductionmentioning

confidence: 99%

“…Analyzing the shape of electron pitch-angle distributions Brain et al (2007) have inferred a topology of magnetic field lines. Brain et al (2007) could distinguish between closed, open and draped field lines. Mitchell et al (2007) inferred a magnetic field pattern below 400 km altitude with implications for the formation mechanisms of the dichotomy on Mars from analysis of electron angular distributions.…”

Section: Introductionmentioning

confidence: 99%

Access of solar wind electrons into the Martian magnetosphere

et al. 2008

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Abstract. Electrons with energy of ∼40-80 eV measured by the instrument ASPERA-3 on Mars Express and MAG-ER onboard Mars Global Surveyor are used to trace an access of solar wind electrons into the Martian magnetosphere. Crustal magnetic fields create an additional protection from solar wind plasma on the dayside of the Southern Hemisphere by shifting the boundary of the induced magnetosphere (this boundary is often refereed as the magnetic pileup boundary) above strong crustal sources to ∼400 km as compared to the Northern Hemisphere. Localized intrusions through cusps are also observed. On the nightside an access into the magnetosphere depends on the IMF orientation. Negative values of the B yIMF component assist the access to the regions with strong crustal magnetizations although electron fluxes are strongly weakened below ∼600 km. A precipitation pattern at lower altitudes is formed by intermittent regions with reduced and enhanced electron fluxes. The precipitation sites are longitudinally stretched narrow bands in the regions with a strong vertical component of the crustal field. Fluxes ≥10 9 cm −2 s −1 of suprathermal electrons necessary to explain the observed aurora emissions are maintained only for the periods with enhanced precipitation. The appearance of another class of electron distributions -inverted V structures, characterized by peaks on energy spectra, is controlled by the IMF. They are clustered in the hemisphere pointed by the interplanetary electric field that implies a constraint on their origin.

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“…They also elevate the induced magnetosphere boundary (IMB) Brain et al, 2005;Dubinin et al, 2006]. Moreover, the magnetic anomalies allow the magnetosheath electrons to precipitate in the cusp-like regions [Ness et al, 2000;Krymskii et al, 2002;Soobiah et al, 2006] and restrict the vertical diffusion of ionospheric electrons in the closed field line regions [Soobiah et al, 2006;Brain et al, 2007]. The parameters and/or chemical states of the neutral atmosphere over the magnetic anomalies could be influenced by the varied plasma flux.…”

Section: Introductionmentioning

confidence: 99%

Influence of Martian crustal magnetic anomalies on the emission of energetic neutral hydrogen atoms

et al. 2014

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We analyze the data on hydrogen energetic neutral atoms (ENAs) emissions from the dayside of Mars, recorded by a Neutral Particle Detector of the Analyzer of Space Plasmas and Energetic Atoms aboard Mars Express from 14 March to 9 July 2004. We first identify and analyze events of the ENA flux enhancement coinciding with the presence of the crustal magnetic anomalies on the dayside of Mars. We then backtrace the ENA emissions to the lower altitudes (source region) and build up an average map of the flux intensities in the geographic coordinates with all the available data. The map shows a peak-to-valley ENA flux enhancement of 40%-90% close to the crustal magnetic anomaly regions. These results suggest the influence of the magnetic anomalies on the ENA emission from the dayside of Mars. The enhancement may result from the deviation of the highly directional plasma flow above anomalies toward the detectors such that more charge exchange ENAs would be recorded. Alternatively, higher exospheric densities above the anomalies would also result in an increase of the charge exchange ENA flux.

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Electron pitch angle distributions as indicators of magnetic field topology near Mars

Cited by 168 publications

References 41 publications

On the relation between plasma escape and the Martian crustal magnetic field

On the relation between plasma escape and the Martian crustal magnetic field

Access of solar wind electrons into the Martian magnetosphere

Influence of Martian crustal magnetic anomalies on the emission of energetic neutral hydrogen atoms

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