Bursty Ion Escape Fluxes at Mars

Abstract

Based on the Mars Atmosphere and Volatile EvolutioN (MAVEN) measurements we have observed cases when the fluxes of oxygen ions escaping the Martian ionosphere exceed their median values by more than a factor of 100. In the Martian tail very high fluxes of the more energetic (E > 30 eV) oxygen ions fill the plasma sheet which then becomes much broader than under conditions with median values of ion fluxes. We have analyzed the occurrence of such events in the upper ionosphere near the terminator plane, which is the main source region of ions in the plasma tail. The maximum values of fluxes of oxygen ions with E > 30 eV were observed mostly in the hemisphere where the motional electric field imposed by the solar wind is directed outward from the planet. Although high values of the solar wind dynamic pressure and (or) the motional electric field are favorable for the observation of the extreme values of ion fluxes with E > 30 eV there must also be other factors which initiate these events. In particular, we found a close relation of the maximum ion fluxes with the values of the simultaneously measured fluxes of solar wind penetrating into the upper ionosphere.Direct interaction of both plasmas might be a critical factor for the strong growth of the oxygen ion escape. Very high fluxes of the low-energy oxygen ions (E < 30 eV) are often related with ion 'clouds' with anomalously large number density observed in the upper ionosphere.

A Statistical Investigation of Factors Influencing the Magnetotail Twist at Mars

“…• Mars' magnetotail can be twisted up to 60 deg away from its expected location based on interplanetary magnetic field (IMF) draping, much greater than Earth's tail twist • MAVEN observations show that Mars' tail exhibits larger twisting for +B Y IMF orientation, compared to −B Y IMF • Mars crustal magnetic fields may play a significant role in shaping the twisted structure of the Martian magnetotail (Bowers et al, 2021;Hara et al, 2017). The Martian magnetotail also serves as a major pathway for atmospheric escape (e.g., Brain, Barabash, et al (2010); Dong et al (2017); Dubinin et al (2011Dubinin et al ( , 2021; Halekas et al (2016); Lundin (2011)).…”

Ultra‐low Frequency Foreshock Waves and Ion Dynamics at Mars

“…Thus, the ULF waves modulate the heavy ion plume and planetary ion acceleration very strongly locally. Strong local variations (more than two orders of magnitude with respect to the mean value) in the heavy ion escape have also been observed by MAVEN and occur often in the +E sw hemisphere (Dubinin et al, 2021). It was proposed that is related to waves and instabilities.…”

“…Several of the escape channels are associated with steady‐state acceleration mechanisms like the planetary ion pickup by the solar wind and the formation of the heavy ion plume (Dong et al., 2017; Futaana et al., 2017). In addition, also dynamical processes can affect planetary ion acceleration in induced magnetospheres (Dubinin et al., 2021; Jarvinen et al., 2020a; Luhmann et al., 1987; Lundin et al., 2011; Omidi et al., 2020). Especially, a foreshock is formed in the upstream region by backstreaming charged particle populations scattered near the bow shock (Brain et al., 2002; Eastwood et al., 2005; Mazelle et al., 2004).…”

Heavy Ion Escape From Martian Wake Enhanced by Magnetic Reconnection

“…Ion escape through the tail or the wake region, however, should be inefficient because of Mars' obstruction. It has been reported that bursty and efficient ion escape processes exist in tail regions (Dubinin et al., 2012, 2021). A similar process occurs in the Venusian tail (Zhang et al., 2012), suggesting this process should be a common characteristic of unmagnetized planets.…”