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 journalArticlepeer-review

16 Scopus citations


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.

Original languageEnglish (US)
Article numbere2021GL093623
JournalGeophysical Research Letters
Issue number14
StatePublished - Jul 28 2021


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

ASJC Scopus subject areas

  • Geophysics
  • General Earth and Planetary Sciences


Dive into the research topics of 'In-Situ Measurements of Electron Temperature and Density in Mars' Dayside Ionosphere'. Together they form a unique fingerprint.

Cite this