Impact of Martian Crustal Magnetic Field on the Ion Escape

Abstract

Based on the Mars Atmosphere and Volatile EvolutioN (MAVEN) observations, we have analyzed the role of the crustal magnetic field on ion loss driven by the direct interaction of the solar wind with the Mars ionosphere. Crustal magnetic fields significantly attenuate the ion ionospheric motions and raise the flux of returning ions. On the other hand, since the ion densities in the ionosphere with strong crustal field are significantly higher than in the ionosphere with a weak crustal magnetic field, the net escape fluxes from the ionosphere with the crustal sources remain vital. The crustal magnetic field also leads to the expansion of the ionosphere and increase of the area exposed to solar wind. As a result, fluxes from higher altitudes essentially contribute to the flow pattern in Martian tail producing an excess of ion loss rate (∼15%) through the southern part of the tail. Thus, effects of inhibition and enhancement of the escape rate by the crustal magnetic field at Mars operate in competition producing a minor influence on the total ion loss.

The Impact and Mechanism of the Magnetic Inclination Angle on O+ Escape from Mars

“…Based on the analysis in this paper, the explanation is that the southern hemisphere possesses more magnetic field lines with high absolute inclination angle to transport O + ions upwards. It is worth noticing that the inward O + fluxes due to backflow are prevalent at lower altitudes in both hemispheres, which is consistent with maps of ion radial velocity in the northern/ southern quadrants provided by Dubinin et al (2020), who suggested that the direction of ion velocity is inward at altitudes below around 400 km. Moreover, the backflow rate is smaller in the southern hemisphere than in the northern one, which can be explained by the flux distributions in Figure 3 where the southern hemisphere has a strong outflow area over the Martian crustal field at lower altitudes.…”

A Spherical Harmonic Martian Crustal Magnetic Field Model Combining Data Sets of MAVEN and MGS

“…Since the better performance of G110 model in low altitude has been demonstrated in the above subsections, it is possible now to survey the crustal field morphology based on the G110 model. The geometric structure of the crustal field is vital for many studies, such as in Martian plate tectonics and Martian particle escape (Bertaux et al., 2005; Dubinin et al., 2020; Fan et al., 2020; Thomas et al., 2018; Xu et al., 2020). Based on calculations from the G110 model, Figure shows the average field lines of crustal field projected in the meridian plane of longitude 180° in the southern hemisphere.…”

Response of Mars's Topside Ionosphere to Changing Solar Activity and Comparisons to Venus

“…Seasonal and solar activity effects on the ionosphere have been explored, including the effects of dust storms (Felici et al., 2020), solar flares (Thiemann et al., 2018), and coronal mass ejections (Duru et al., 2017; Thampi et al., 2018). MAVEN has also enhanced our understanding of how Mars's ionosphere is influenced by the presence of crustal magnetic fields (e.g., Flynn et al., 2017; Withers et al., 2019), which has important implications for ionospheric escape (e.g., Dubinin et al., 2020) and the behavior of Mars's sporadic ionopause (e.g., Duru et al., 2020; Sánchez‐Cano et al., 2020).…”