Abstract
We present initial analysis and conclusions from plasma observations made during the reported "Mars plume event" of March - April 2012. During this period, multiple independent amateur observers detected a localized, high-altitude "plume" over the Martian dawn terminator [Sanchez-Lavega et al., Nature, 2015, doi:10.1038/nature14162], the cause of which remains to be explained. The estimated brightness of the plume exceeds that expected for auroral emissions, and its projected altitude greatly exceeds that at which clouds are expected to form. We report on in-situ measurements of ionospheric plasma density and solar wind parameters throughout this interval made by Mars Express, obtained over the same surface region, but at the opposing terminator. Measurements in the ionosphere at the corresponding location frequently show a disturbed structure, though this is not atypical for such regions with intense crustal magnetic fields. We tentatively conclude that the formation and/or transport of this plume to the altitudes where it was observed could be due in part to the result of a large interplanetary coronal mass ejection (ICME) encountering the Martian system. Interestingly, we note that the only similar plume detection in May 1997 may also have been associated with a large ICME impact at Mars.
Highlights
Mars, including its surface, atmosphere, and induced magnetosphere, has been the subject of continuous in situ study for nearly two decades
We report on in situ measurements of ionospheric plasma density and solar wind parameters throughout this interval made by Mars Express, obtained over the same surface region but at the opposing terminator
Summary We have presented observations of the Martian ionosphere and induced magnetosphere obtained during the period March–April 2012, during which an anomalously high-altitude atmospheric plume was reported by SL15
Summary
Mars, including its surface, atmosphere, and induced magnetosphere, has been the subject of continuous in situ study for nearly two decades. Solar flares and the associated increase in ionizing UV light has been shown to enhance the Martian ionosphere [e.g., Mendillo et al, 2006; Mahajan and Mayr, 1990], as has the precipitation of shock-accelerated solar energetic particles (SEPs) into the atmosphere [e.g., Lillis et al, 2012; Ulusen et al, 2012; Nemec et al, 2014] It must be noted, that these three sources of short-term variations in the ionosphere and induced magnetosphere, while themselves often having a common root cause on the solar surface, often are incident at Mars at markedly different times. Distributed multipoint measurements and/or advanced modeling schemes are required to fully understand the causal relationships between these observations [e.g., Falkenberg et al, 2011]
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