Global Ambipolar Potentials and Electric Fields at Mars Inferred From MAVEN Observations

Xu, Shaosui; Mitchell, David; Ma, Yingjuan; Weber, Tristan; Brain, David; Halekas, J. S.; Ruhunusiri, S.; DiBraccio, G. A.; Mazelle, C.

doi:10.1029/2021ja029764

Cited by 12 publications

(15 citation statements)

References 48 publications

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“…Furthermore, this type of electric field inferred from electrostatic potential also exists in the Martian bow shock (BS) and magnetosheath region (Schwartz et al 2019;Horaites et al 2021). The above global characterization and effect of the ambipolar electric field has been confirmed by observations and simulations (Ma et al 2019;Xu et al 2021).…”

Section: Introductionmentioning

confidence: 65%

Global Electric Fields at Mars Inferred from Multifluid Hall-MHD Simulations

Cao

et al. 2023

ApJ

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In the Martian induced magnetosphere, the motion of planetary ions is significantly controlled by the ambient electric fields, which can be decomposed into three components: the motional, Hall, and ambipolar electric fields. Each of them is dominant in different regions and provides the ion acceleration with a particular effectiveness. Therefore, it is necessary to characterize the global distribution of these electric field components. In this study, a global multifluid Hall-MHD model is applied, which considers the motional, Hall, and ambipolar electric fields in ion transport and magnetic induction equations to self-consistently investigate the morphology of the electric fields in the Martian space environment. Numerical results suggest that the motional electric field is dominant in the upstream of the bow shock and in the magnetosheath along the Z MSE direction, leading to the formation of the ion plume escape channel. At the bow shock, the ambipolar electric field points outward, to decelerate and deflect the solar wind plasma flow. In the magnetosheath region, the ambipolar and motional electric fields with inward direction tend to reaccelerate the solar wind ions. However, along the magnetic pileup boundary, the Hall electric field pointing outward prevents the solar wind ions from penetrating the Martian induced magnetosphere, which also prevails in the Martian magnetotail region, to accelerate the ions’ tailward escape. This is the first systematic investigation of the global distribution of electric fields, which is helpful to understand the processes of ion acceleration/deceleration and escape within the Mars–solar wind interaction.

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Section: Introductionmentioning

confidence: 65%

Global Electric Fields at Mars Inferred from Multifluid Hall-MHD Simulations

Cao

et al. 2023

ApJ

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“…Also, depending on the detection threshold and sensitivity of the remote‐sensing instrument, similarly, a threshold should be applied to the electron flux to select source electrons. Nominal nightside precipitating solar wind electron fluxes (below ∼400 km altitude) are observed to be lower than that in the upstream solar wind by both Mars Global Surveyor (MGS)(e.g., Mitchell et al., 2001; Shane et al., 2016) and MAVEN (e.g., Weber et al., 2017), which is caused by an accumulative deceleration by the ambipolar electric fields within the induced magnetosphere (Xu, Mitchell, et al., 2021). There are also dayside ionospheric photoelectrons transported and precipitating to the nightside via cross‐terminator closed field lines (e.g., Xu, Mitchell, et al., 2016; Xu, Mitchell, Liemohn, et al., 2017; Xu, Mitchell, Luhmann, et al., 2017).…”

Section: Introductionmentioning

confidence: 99%

Empirically Determined Auroral Electron Events at Mars—MAVEN Observations

Mitchell

McFadden

et al. 2022

Geophysical Research Letters

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Discrete aurorae have been observed at magnetized planets such as Earth and Jupiter, triggered by accelerated electrons. Similar aurorae have also been observed at Mars with only localized strong crustal magnetisms. However, our understanding of this phenomenon at Mars is still limited. In particular, direct and quantitative comparisons of the auroral and its source electron events are lacking as these two types of observations are usually made at different times and/or locations. In this study, we establish empirical criteria to select electron events (“auroral electrons”) that could trigger detectable auroral emissions with Mars Atmosphere and Volatile EvolutioN measurements, thereby enabling a direct statistical comparison. We find auroral electrons share similar statistical characteristics to those previously reported for discrete auroral events. This study bridges the gap between electron observations and auroral detections and enables collaborations across different Mars missions, as well as comparative planetary studies of discrete aurora.

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“…Measurements from Phobos 2 (Lundin, 1989), MEX (Barabash, 2007;Nilsson, 2021) and MAVEN (Dong, 2017) and estimates from magnetohydrodynamic (MHD) (Ma and nagy, 2007;Regoli, 2018) and hybrid models indicate that the heavy ions escape rate on Mars is between 10 23 −10 25 s −1 . The parameters affecting the solar wind interaction with the Martian atmosphere have been investigated, including the upstream conditions like extreme ultraviolet (EUV) radiation and solar wind dynamic pressure (Dong, 2017;Nilsson, 2021;Ramstad, 2021), and crustal magnetic fields Ramstad, 2016;Weber, 2021).…”

Section: Introductionmentioning

confidence: 99%

Effects of ion composition on escape and morphology at Mars

Zhang

Holmström²,

Holmström³

2023

Preprint

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Abstract. We refine a recently presented method to estimate ion escape from non-magnetized planets and apply it to Mars. The method combines in-situ observations and a hybrid plasma model (ions as particles, electrons as a fluid). We use measurements from the Mars Atmosphere and Volatile Evolution (MAVEN) mission and Mars Express (MEX) for one orbit on 2015-03-01. Observed upstream solar wind conditions are used as input to the model. We then vary the total ionospheric ion upflux until the solution fits the observed bow shock location. This solution is a self-consistent approximation of the global Mars-solar wind interaction at this moment, for the given upstream conditions. We can then study global properties, such as the heavy ion escape rate. Here we investigate the effects on escape estimates of assumed ionospheric ion composition, solar wind alpha particle concentration and temperature, solar wind velocity aberration, and solar wind electron temperature. We also study the amount of escape in the ion plume and in the tail of the planet. Here we find that estimates of total heavy ion escape are not very sensitive to the composition of the heavy ions, or the amount and temperature of the solar wind alpha particles. We also find that velocity aberration has a minor influence on escape, but that it is sensitive to the solar wind electron temperature. The plume escape is found to contribute 29 % of the total heavy ion escape, in agreement with observations. Heavier ions have a larger fraction of escape in the plume compared to the tail. We also find that the escape estimates scales inversely with the square root of the atomic mass of the escaping ion specie.

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Global Ambipolar Potentials and Electric Fields at Mars Inferred From MAVEN Observations

Cited by 12 publications

References 48 publications

Global Electric Fields at Mars Inferred from Multifluid Hall-MHD Simulations

Global Electric Fields at Mars Inferred from Multifluid Hall-MHD Simulations

Empirically Determined Auroral Electron Events at Mars—MAVEN Observations

Effects of ion composition on escape and morphology at Mars

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