Atypically Intense and Delayed Response of the Martian Ionosphere to the Regional Dust Storm of 2016: A Study Using MAVEN Observations and Models

During Mars dust storms, atmospheric heating and expansion moves the ionospheric peak upward. Typically, peak altitude increases by no more than 10 km, and this increase occurs simultaneously with the expansion of the dust storm. However, Felici et al. (2020), https://doi.org/10.1029/2019JA027083, using the Mars Atmosphere Volatile EvolutioN (MAVEN) Radio Occultation Science Experiment (ROSE), reported an unusually large increase of ∼20 km at southern latitudes in early October 2016 during a modest dust storm. Here, we investigate why the ionospheric peak altitude increased so much in these observations. We extend the time series of ionospheric peak altitude values beyond the limited extent of the ROSE observations by applying a one-dimensional photochemical model, in which neutral atmospheric conditions are based on in situ MAVEN Neutral Gas Ion Mass Spectrometer observations at similar latitudes and solar zenith angles to those observed by ROSE. We find that the ionospheric peak altitude was highest throughout October 2016 yet both the local and global atmospheric dust loading were greatest 1 month earlier. We hypothesize that (a) a portion of the unusually large 20 km enhancement in peak altitude and (b) the unusual delay between the greatest dust loading and the highest peak altitude were both associated with the occurrence of perihelion, which maximizes solar heating of the atmosphere, in late October 2016. © 2022. American Geophysical Union. All Rights Reserved.Vrinda Mukundan is supported by the Department of Science and Technology (DST), Government of India, with Innovation in Science Pursuit for Inspired Research (INSPIRE) faculty award (Grant DST/INSPIRE/04/2019/002599). Vrinda Mukundan would like to thank the Director, NCESS and Dr. D. Padmalal, NCESS, for their encouragement and for facilitating a conducive research environment. Boston University's contribution to this project was supported, in part, by the NASA's MAVEN project. The work at Space Physics Laboratory is supported by the Indian Space Research Organisation. The work at Physical Research Laboratory is supported by the Department of Space, Government of India. Anil Bhardwaj was a J.C. Bose National Fellow during the period of this work. F. González-Galindo is funded by the Spanish Ministerio de Ciencia, Innovación y Universidades, the Agencia Estatal de Investigación and ECFEDER funds under project RTI2018-100920-J-I00 and acknowledges financial support from the State Agency for Research of the Spanish MCIU through the “Center of Excellence Severo Ochoa” award to the Instituto de Astrofísica de Andalucía (SEV-2017-0709). The authors gratefully acknowledge the MAVEN team for the data

Investigation of the solar wind-Moon interaction onboard Chandrayaan-1 mission with the SARA experiment

The SARA instrument (Sub-keV Atom Reflecting Analyser) comprises a low energy neutral atom (LENA) sensor for the energy range 10 eV-3.3 keV and an ion mass spectrometer (10 eV-15 keV). It is the first ever experiment to study the solar wind-planetary surface interaction via measurements of the sputtered atoms and neutralized back-scattered solar wind hydrogen. The neutral atom sensor uses conversion of the incoming neutrals to positive ions, which are then analysed via surface interaction technique. The ion mass spectrometer is based on the same principle. SARA performs LENA imaging of the Moon's elemental surface composition including that of permanently shadowed areas, and imaging of the lunar surface magnetic anomalies. It will also investigate processes of space weathering and sputtered sources of the exospheric gases