Predictions of electron temperatures in the Mars ionosphere and their effects on electron densities

Withers, Paul; Fallows, K.; Matta, Majd

doi:10.1002/2014gl059683

Cited by 16 publications

(35 citation statements)

References 38 publications

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“…All existing measurements of the

O_{2}^{+}

dissociative recombination coefficient, α , at 300 K agree within 15% [ McLain et al , ]. Meanwhile, since α is proportional to electron temperature to the power of −0.7 [ Peverall et al , ; McLain et al , ], the reduced value of α reported above would then imply an exceptionally high electron temperature of ≈7.2 × 10 3 K, which, at ionospheric altitudes, is not predicted by any existing models [e.g., Matta et al , ; Withers et al , ]. Strictly speaking, α in equation refers to the

O_{2}^{+}

dissociative recombination coefficient weighted by electron density squared.…”

Section: Modeling Of the Day‐to‐night Transportmentioning

confidence: 78%

Day‐to‐night transport in the Martian ionosphere: Implications from total electron content measurements

et al. 2015

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(2015), Day-to-night transport in the Martian ionosphere: Implications from total electron content measurements, J. Geophys. Res. Space Physics, 120, 2333-2346, doi:10.1002 Abstract The nightside Martian ionosphere is thought to be contributed by day-to-night transport and electron precipitation, of which the former has not been well studied. In this work, we evaluate the role of day-to-night transport based on the total electron content (TEC) measurements made by the Mars Advanced Radar for Subsurface and Ionospheric Sounding on board Mars Express. This is accomplished by an examination of the variation of nightside TEC in the time domain rather than the traditional solar zenith angle domain. Our analyses here, being constrained to the Northern Hemisphere where the effects of crustal magnetic fields can be neglected, reveal that day-to-night transport serves as the dominant source for the nightside Martian ionosphere from terminator crossing up to time in darkness of ≈ 5.3 × 10 3 s, beyond which it is surpassed by electron precipitation. The observations are compared with predictions from a simplified time-dependent ionosphere model. We conclude that the solid body rotation of Mars is insufficient to account for the observed depletion of nightside TEC but the data could be reasonably reproduced by a zonal electron flow velocity of ≈ 1.9 km s −1 .

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“…All existing measurements of the

O_{2}^{+}

O_{2}^{+}

dissociative recombination coefficient weighted by electron density squared.…”

Section: Modeling Of the Day‐to‐night Transportmentioning

confidence: 78%

Day‐to‐night transport in the Martian ionosphere: Implications from total electron content measurements

et al. 2015

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“…Withers et al . [] came to an opposite conclusion based on simulations of the dependence of the peak electron density with temperature using the Boston University ionosphere model [e.g., Martinis et al ., ; Matta et al ., ]. However, they assumed an electron temperature profile based on extrapolations of the Viking lander measurements to lower altitudes [ Mendillo et al ., ].…”

Section: Discussionmentioning

confidence: 99%

MAVEN observations of dayside peak electron densities in the ionosphere of Mars

et al. 2017

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The peak electron density in the dayside Martian ionosphere is a valuable diagnostic of the state of the ionosphere. Its dependence on factors like the solar zenith angle, ionizing solar irradiance, neutral scale height, and electron temperature has been well studied. The Mars Atmosphere and Volatile EvolutioN spacecraft's September 2015 “deep dip” orbits, in which the orbital periapsis was lowered to ~125 km, provided the first opportunity since Viking to sample in situ a complete dayside electron density profile including the main peak. Here we present peak electron density measurements from 37 deep dip orbits and describe conditions at the altitude of the main peak, including the electron temperature and composition of the ionosphere and neutral atmosphere. We find that the dependence of the peak electron density and the altitude of the main peak on solar zenith angle are well described by analytical photochemical theory. Additionally, we find that the electron temperatures at the main peak display a dependence on solar zenith angle that is consistent with the observed variability in the peak electron density. Several peak density measurements were made in regions of large crustal magnetic field, but there is no clear evidence that the crustal magnetic field strength influences the peak electron density, peak altitude, or electron temperature. Finally, we find that the fractional abundance of O2+ and CO2+ at the peak altitude is variable but that the two species together consistently represent ~95% of the total ion density.

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“…Physically, this rate can vary with the solar zenith angle (SZA) as solar wind normal pressure onto the planet is smaller with increasing SZA. In addition, the altitude of the Martian dayside electron density peak is also roughly proportional to a cosine function of SZA [e.g., Hantsch and Bauer , ; Withers , ; Withers et al , ], which can be explained by Chapman theory [ Chapman , ]. As a result, the magnetic pileup boundary (MPB) is closer to the planet near the subsolar point and at higher altitudes at larger SZA [e.g., Vignes et al , ; Crider et al , ; Nagy et al , ].…”

Section: Resultsmentioning

confidence: 99%

Solar wind electron precipitation into the dayside Martian upper atmosphere through the cusps of strong crustal fields

Liemohn

Mitchell

2014

JGR Space Physics

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Measurements made by the magnetometer/electron reflectometer on board the Mars Global Surveyor spacecraft have shown spatially localized enhancements in electron fluxes over the strong crustal fields on both the dayside and night, which are used to identify the cusps in between the closed magnetic fields. This paper provides a comprehensive statistical study on the occurrence rate of dayside solar wind/magnetosheath precipitation over the strong crustal fields. Also, the occurrence rate's dependence on the magnetic elevation angles and the solar zenith angle is presented. A seasonal variation of the precipitation is also expected and found, due to both the tilt and the orbital eccentricity of Mars. The maximum occurrence rate is 40%, when the solar zenith angles are small and the magnetic fields are nearly vertical. Finally, the energy flux deposition of the solar wind electrons is calculated as well, which is 0.1%–2% of solar EUV flux input.

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Predictions of electron temperatures in the Mars ionosphere and their effects on electron densities

Cited by 16 publications

References 38 publications

Day‐to‐night transport in the Martian ionosphere: Implications from total electron content measurements

Day‐to‐night transport in the Martian ionosphere: Implications from total electron content measurements

MAVEN observations of dayside peak electron densities in the ionosphere of Mars

Solar wind electron precipitation into the dayside Martian upper atmosphere through the cusps of strong crustal fields

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