MAVEN Observations of Periodic Low-altitude Plasma Clouds at Mars

Abstract

Ion escape to space through the interaction of solar wind and Mars is an important factor influencing the evolution of the Martian atmosphere. The plasma clouds (explosive bulk plasma escape), considered an important ion escaping channel, have been recently identified by spacecraft observations. However, our knowledge about Martian plasma clouds is lacking. Based on the observations of the Mars Atmosphere and Volatile EvolutioN (MAVEN) spacecraft, we study a sequence of periodic plasma clouds that occurred at low altitudes (∼600 km) on Mars. We find that the heavy ions in these clouds are energy-dispersed and have the same velocity, regardless of species. By tracing such energy-dispersed ions, we find the source of these clouds is located in a low-altitude ionosphere (∼120 km). The average tailward moving flux of ionospheric plasma carried by clouds is on the order of 107 cm−2 s−1, which is one order higher than the average escaping flux for the magnetotail, suggesting explosive ion escape via clouds. Based on the characteristics of clouds, we suggest, similar to the outflow of Earth’s cusp, these clouds might be the product of heating due to solar wind precipitation along the open field lines, which were generated by magnetic reconnection between the interplanetary magnetic field and crustal fields that occurred above the source.

Three‐Dimensional Configuration of Induced Magnetic Fields Around Mars

“…Solar wind dynamic pressure (Pdy) is believed to significantly impact the magnetic structure of an induced magnetosphere and ion escape (e.g., C. Zhang et al, 2021;Dubinin et al, 2017;Nilsson et al, 2010Nilsson et al, , 2011T. L. Zhang et al, 1994;Ramstad et al, 2015).…”

“…Solar wind dynamic pressure (Pdy) is believed to significantly impact the magnetic structure of an induced magnetosphere and ion escape (e.g., C. Zhang et al., 2021; Dubinin et al., 2017; Nilsson et al., 2010, 2011; T. L. Zhang et al., 1994; Ramstad et al., 2015). Based on our data set, we quantitatively evaluate how Pdy affects the magnetic field structure around Mars.…”

“…The draped IMF is stretched by the solar wind and slips into the wake to form an elongated induced magnetotail (e.g., Acuña et al., 1998; Luhmann et al., 2004; Ma et al., 2002; McComas et al., 1986). Researchers realize that most of the planetary ions escape to interplanetary space via the electromagnetic force, for example, the solar wind electric fields ( E ), the hall electric fields, and the ambipolar electric fields (e.g., Barabash et al., 2007; C. Zhang et al., 2021; Dubinin & Fraenz, 2015; Dubinin et al., 2011; Futaana et al., 2017; Lundin, 2011; Nilsson et al., 2021); therefore, knowledge of the magnetic field structure around the Mars is vital for understanding associated magnetospheric processes (e.g., the escape of planetary ions).…”

Mars‐Ward Ion Flows in the Martian Magnetotail: Mars Express Observations

“…Correspondingly, the solar wind accelerates planetary ions via the electromagnetic forces, such as motional electric fields (Barabash et al., 1991; C. Dong et al., 2014; Fang et al., 2008), Hall electric fields (Dubinin et al., 2011; Lundin, 2011), and ambipolar electric fields (e.g., Collinson et al., 2019; Y. J. Ma et al., 2019; Xu et al., 2021). In addition, localized intense crustal fields complexify the Martian magnetosphere and affect ion escape (e.g., Connerney et al., 2005; C. Dong et al., 2015; Y. Dong et al., 2015; Fang et al., 2010; Ramstad et al., 2016; C. Zhang et al., 2021).…”

In‐Situ Measurements of Ion Density in the Martian Ionosphere: Underlying Structure and Variability Observed by the MAVEN‐STATIC Instrument

“…MAVEN has complemented earlier estimates of ion escape rates with studies that demonstrate how these rates change as functions of various drivers that include the crustal magnetic fields, seasonal influences and variations in upstream solar wind conditions (Brain et al, 2015;Dong et al, 2017;Ledvina et al, 2017;Ramstad et al, 2016;Zhang et al, 2021). It has long been thought that the Mars-solar wind interaction would lead to electromagnetic wave heating of the topside Martian ionosphere (Ergun et al, 2006;Lundin et al, 2004;Moses et al, 1988), and MAVEN case studies have captured these processes in action (C. C.…”