Dayside electron temperature and density profiles at Mars: First results from the MAVEN Langmuir probe and waves instrument

Ergun, R. E.; Morooka, M.; Andersson, L.; Fowler, Christopher; Delory, G. T.; Andrews, David; Eriksson, Anders; McEnulty, T.; Jakosky, B. M.

doi:10.1002/2015gl065280

Cited by 130 publications

(235 citation statements)

References 39 publications

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“…We expect that our results are lower than this quantity, as we are only analyzing SZA > 40°. Taking this into account, our results are in agreement to those of MAVEN shown in Ergun et al [], if for the peak region the ion temperature is approximately equal to the electron temperature as the Viking landers recorded [ Hanson et al , ; Hanson and Mantas , ]. An indirect comparison can also be done from the radio occultation profiles acquired by Mars Global Surveyor mission.…”

Section: Ionospheric Temperature Evolution With Solar Cyclesupporting

confidence: 90%

“…For high solar activity phase, our results can be compared to the recent MAVEN measurements of electron temperature. Ergun et al [] show that for 15° of solar zenith angle, the electron temperature is ~0.052 eV at 130 km (~600 K). We expect that our results are lower than this quantity, as we are only analyzing SZA > 40°.…”

Section: Ionospheric Temperature Evolution With Solar Cyclementioning

confidence: 99%

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Solar cycle variations in the ionosphere of Mars as seen by multiple Mars Express data sets

et al. 2016

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The response of the Martian ionosphere to solar activity is analyzed by taking into account variations in a range of parameters during four phases of the solar cycle throughout 2005–2012. Multiple Mars Express data sets have been used (such as Mars Advanced Radar for Subsurface and Ionospheric Sounding (MARSIS) in Active Ionospheric Sounding, MARSIS subsurface, and MaRS Radio Science), which currently cover more than 10 years of solar activity. The topside of the main ionospheric layer behavior is empirically modeled through the neutral scale height parameter, which describes the density distribution in altitude, and can be used as a dynamic monitor of the solar wind‐Martian plasma interaction, as well as of the medium's temperature. The main peak, the total electron content, and the relationship between the solar wind dynamic pressure and the maximum thermal pressure of the ionosphere with the solar cycle are assessed. We conclude that the neutral scale height was different in each phase of the solar cycle, having a large variation with solar zenith angle during the moderate‐ascending and high phases, while there is almost no variation during the moderate‐descending and low phases. Between end‐2007 and end‐2009, an almost permanent absence of secondary layer resulted because of the low level of solar X‐rays. Also, the ionosphere was more likely to be found in a more continuously magnetized state. The induced magnetic field from the solar wind, even if weak, could be strong enough to penetrate more than at other solar cycle phases.

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Section: Ionospheric Temperature Evolution With Solar Cyclesupporting

confidence: 90%

Section: Ionospheric Temperature Evolution With Solar Cyclementioning

confidence: 99%

Solar cycle variations in the ionosphere of Mars as seen by multiple Mars Express data sets

et al. 2016

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“…The neutral temperatures, T n , are not used in the calculation but are shown for completeness. Similarly, the electron temperatures, T e , have been modified from those presented by Ergun et al [2015] below 200 km to merge smoothly with the value of T n of 147 K at an altitude of 130 km. McFadden (private communication, 2016) and were constrained in the altitude region below 175-180 km to merge with the T n profile.…”

Section: Photochemical Equilibrium Calculationsmentioning

confidence: 94%

Photochemical determination of O densities in the Martian thermosphere: Effect of a revised rate coefficient

Fox

Johnson

Ard

et al. 2017

Geophysical Research Letters

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We investigate the production and loss rates of O2+ in the photochemical equilibrium region of the Martian ionosphere near the subsolar point. We adopt neutral and ion densities measured by the Mars Atmosphere and Volatiles EvolutioN (MAVEN) Neutral Gas and Ion Mass Spectrometer (NGIMS), electron densities and temperatures measured by the Langmuir Probe and Waves, and ion temperatures measured by the Supra‐Thermal and Thermal Ion Composition instruments on the MAVEN spacecraft. Contrary to the conventional wisdom, we find that loss of O2+ by dissociative recombination is balanced mainly by production due to the reaction of O+ with CO2, with a smaller contribution due to the reaction of CO2+ with O. We find that the O densities derived from this calculation are larger than those measured by the NGIMS instrument by a factor that averages about 4 over the range of 130–155 km. This general conclusion is supported by a newly measured rate coefficient for the reaction of O with CO2+, which is smaller by a factor of about 6 than the only value in the literature, which was measured 47 years ago.

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“…The LP instrument measures the electrical current generated from the surrounding plasma by sweeping the probe‐biased voltages with 128 steps with the maximum sweep range of −50 and 50 V (I–V characteristics), although the details of the sweeps (range and cadence) can vary depending on plasma regime. At periapsis, where the high‐resolution measurements are made, the sweep range is ±5 V (cold plasma) with sweep duration of 1 s and a sweep cadence of 1–2 per 4 s [ Andersson et al , ; Ergun et al , ]. The LPW has two independent cylindrical probes with a diameter of 0.0625 cm and with a length of 40 cm long, and the probes have a titanium nitride coating.…”

Section: Maven Measurementsmentioning

confidence: 99%

Electron energetics in the Martian dayside ionosphere: Model comparisons with MAVEN data

et al. 2016

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This paper presents a study of the energetics of the dayside ionosphere of Mars using models and data from several instruments on board the Mars Atmosphere and Volatile EvolutioN spacecraft. In particular, calculated photoelectron fluxes are compared with suprathermal electron fluxes measured by the Solar Wind Electron Analyzer, and calculated electron temperatures are compared with temperatures measured by the Langmuir Probe and Waves experiment. The major heat source for the thermal electrons is Coulomb heating from the suprathermal electron population, and cooling due to collisional rotational and vibrational CO2 dominates the energy loss. The models used in this study were largely able to reproduce the observed high topside ionosphere electron temperatures (e.g., 3000 K at 300 km altitude) without using a topside heat flux when magnetic field topologies consistent with the measured magnetic field were adopted. Magnetic topology affects both suprathermal electron transport and thermal electron heat conduction. The effects of using two different solar irradiance models were also investigated. In particular, photoelectron fluxes and electron temperatures found using the Heliospheric Environment Solar Spectrum Radiation irradiance were higher than those with the Flare Irradiance Spectrum Model‐Mars. The electron temperature is shown to affect the O2+ dissociative recombination rate coefficient, which in turn affects photochemical escape of oxygen from Mars.

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Dayside electron temperature and density profiles at Mars: First results from the MAVEN Langmuir probe and waves instrument

Cited by 130 publications

References 39 publications

Solar cycle variations in the ionosphere of Mars as seen by multiple Mars Express data sets

Solar cycle variations in the ionosphere of Mars as seen by multiple Mars Express data sets

Photochemical determination of O densities in the Martian thermosphere: Effect of a revised rate coefficient

Electron energetics in the Martian dayside ionosphere: Model comparisons with MAVEN data

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