In-Situ Measurements of Electron Temperature and Density in Mars' Dayside Ionosphere

R. E. Ergun; L. A. Andersson; C. M. Fowler; S. A. Thaller; R. V. Yelle

doi:10.1029/2021GL093623

In-Situ Measurements of Electron Temperature and Density in Mars' Dayside Ionosphere

R. E. Ergun, L. A. Andersson, C. M. Fowler, S. A. Thaller, R. V. Yelle

Research output: Contribution to journal › Article › peer-review

21 Scopus citations

Abstract

We present dayside electron temperature (T_e) and density altitude profiles at Mars from MAVEN satellite deep-dip orbits. The data are after recalibration of the Langmuir Probe and Waves instrument that results in reduced uncertainties to as low as ±82°K. At MAVEN's lowest altitudes, (∼120–∼135 km), the measured values of T_e are, after uncertainties, higher than those predicted by several modeling efforts. To better understand this discrepancy, we perform a basic heat-transfer analysis for two specific dayside deep dips. The analysis supports that CO₂ excitation/de-excitation of its lowest-energy vibrational states dominates energy transfer to and from electrons. We hypothesize that the discrepancy between the measured and modeled T_e is due to (a) the coupling of T_e to CO₂ vibrational temperatures combined with a non-LTE (local thermal equilibrium) excess of excited CO₂ and/or (b) a non-Maxwellian electron distribution that moderates CO₂ cooling.

Original language	English (US)
Article number	e2021GL093623
Journal	Geophysical Research Letters
Volume	48
Issue number	14
DOIs	https://doi.org/10.1029/2021GL093623
State	Published - Jul 28 2021

Keywords

CO excited states
CO temperatures
Mars' ionosphere
electron temperature
energy transfer

ASJC Scopus subject areas

Geophysics
General Earth and Planetary Sciences

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10.1029/2021GL093623

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title = "In-Situ Measurements of Electron Temperature and Density in Mars' Dayside Ionosphere",

abstract = "We present dayside electron temperature (Te) and density altitude profiles at Mars from MAVEN satellite deep-dip orbits. The data are after recalibration of the Langmuir Probe and Waves instrument that results in reduced uncertainties to as low as ±82°K. At MAVEN's lowest altitudes, (∼120–∼135 km), the measured values of Te are, after uncertainties, higher than those predicted by several modeling efforts. To better understand this discrepancy, we perform a basic heat-transfer analysis for two specific dayside deep dips. The analysis supports that CO2 excitation/de-excitation of its lowest-energy vibrational states dominates energy transfer to and from electrons. We hypothesize that the discrepancy between the measured and modeled Te is due to (a) the coupling of Te to CO2 vibrational temperatures combined with a non-LTE (local thermal equilibrium) excess of excited CO2 and/or (b) a non-Maxwellian electron distribution that moderates CO2 cooling.",

keywords = "CO excited states, CO temperatures, Mars' ionosphere, electron temperature, energy transfer",

author = "Ergun, {R. E.} and Andersson, {L. A.} and Fowler, {C. M.} and Thaller, {S. A.} and Yelle, {R. V.}",

note = "Funding Information: The authors thank Gwen Hanley for useful discussions. The MAVEN project is supported by NASA through the Mars Exploration Program. Publisher Copyright: {\textcopyright} 2021. American Geophysical Union. All Rights Reserved.",

year = "2021",

month = jul,

day = "28",

doi = "10.1029/2021GL093623",

language = "English (US)",

volume = "48",

journal = "Geophysical Research Letters",

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T1 - In-Situ Measurements of Electron Temperature and Density in Mars' Dayside Ionosphere

AU - Ergun, R. E.

AU - Andersson, L. A.

AU - Fowler, C. M.

AU - Thaller, S. A.

AU - Yelle, R. V.

N1 - Funding Information: The authors thank Gwen Hanley for useful discussions. The MAVEN project is supported by NASA through the Mars Exploration Program. Publisher Copyright: © 2021. American Geophysical Union. All Rights Reserved.

PY - 2021/7/28

Y1 - 2021/7/28

N2 - We present dayside electron temperature (Te) and density altitude profiles at Mars from MAVEN satellite deep-dip orbits. The data are after recalibration of the Langmuir Probe and Waves instrument that results in reduced uncertainties to as low as ±82°K. At MAVEN's lowest altitudes, (∼120–∼135 km), the measured values of Te are, after uncertainties, higher than those predicted by several modeling efforts. To better understand this discrepancy, we perform a basic heat-transfer analysis for two specific dayside deep dips. The analysis supports that CO2 excitation/de-excitation of its lowest-energy vibrational states dominates energy transfer to and from electrons. We hypothesize that the discrepancy between the measured and modeled Te is due to (a) the coupling of Te to CO2 vibrational temperatures combined with a non-LTE (local thermal equilibrium) excess of excited CO2 and/or (b) a non-Maxwellian electron distribution that moderates CO2 cooling.

AB - We present dayside electron temperature (Te) and density altitude profiles at Mars from MAVEN satellite deep-dip orbits. The data are after recalibration of the Langmuir Probe and Waves instrument that results in reduced uncertainties to as low as ±82°K. At MAVEN's lowest altitudes, (∼120–∼135 km), the measured values of Te are, after uncertainties, higher than those predicted by several modeling efforts. To better understand this discrepancy, we perform a basic heat-transfer analysis for two specific dayside deep dips. The analysis supports that CO2 excitation/de-excitation of its lowest-energy vibrational states dominates energy transfer to and from electrons. We hypothesize that the discrepancy between the measured and modeled Te is due to (a) the coupling of Te to CO2 vibrational temperatures combined with a non-LTE (local thermal equilibrium) excess of excited CO2 and/or (b) a non-Maxwellian electron distribution that moderates CO2 cooling.

KW - CO excited states

KW - CO temperatures

KW - Mars' ionosphere

KW - electron temperature

KW - energy transfer

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U2 - 10.1029/2021GL093623

DO - 10.1029/2021GL093623

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JO - Geophysical Research Letters

JF - Geophysical Research Letters

IS - 14

M1 - e2021GL093623

ER -

In-Situ Measurements of Electron Temperature and Density in Mars' Dayside Ionosphere

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Keywords

ASJC Scopus subject areas

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