The Influence of Interplanetary Magnetic Field Direction on Martian Crustal Magnetic Field Topology

Weber, Tristan; Brain, David; Xu, Shaosui; Mitchell, David; Espley, J. R.; Halekas, J. S.; Mazelle, Christian; Lillis, R. J.; DiBraccio, G. A.; Jakosky, B. M.

doi:10.1029/2020gl087757

Cited by 34 publications

(39 citation statements)

References 52 publications

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“…Depending on solar wind IMF orientation, the draped magnetic field at Mars can be roughly opposite to a local crustal field direction. Indeed, the topology of Martian crustal magnetic fields depends upon the IMF clock angle (Brain et al., 2020; Weber et al., 2020), explaining the strong dependence of auroral detections on IMF orientation described in Section 4.3. The interface between these oppositely directed magnetic fields will have strong currents perpendicular to B (carried by pressure gradients) that can be unstable to reconnection.…”

Section: Conclusion and Discussionmentioning

confidence: 99%

Discrete Aurora on Mars: Insights Into Their Distribution and Activity From MAVEN/IUVS Observations

et al. 2021

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The Mars Atmosphere and Volatile Evolution (MAVEN) spacecraft has been orbiting Mars since September 21, 2014, with a primary mission to study the behavior of the upper atmosphere and the escape of its constituent gases to space (Jakosky et al., 2014). At the time of these observations, MAVEN orbited Mars on a 4.5-h elliptical orbit with a closest approach to Mars' surface at periapse of 150-200 km and an apoapse ranging from 6,200 km to 4,400 km over the mission. MAVEN carries one remote sensing instrument for the study of Mars' upper atmosphere: the Imaging UltraViolet Spectrograph (IUVS) (McClintock et al., 2015). The instrument captures spectra of the planet and its atmosphere in the far-UV (FUV) from 110 to 190 nm and mid-UV (MUV) from 180 to 340 nm, ideal for recording well-known atmospheric emissions from CO 2 and its dissociation and ionization products. The instrument is mounted on an Articulated Payload Platform (APP), which can orient IUVS's field of view relative to Mars depending on spacecraft location, orientation and desired viewing geometry. IUVS was designed to observe the Mars dayglow, nightglow, hydrogen corona, D/H ratio, and stellar occultations, and is also sensitive to auroral emissions. Mars exhibits at least three types of aurora (Figure 1). The SPICAM instrument on Mars Express discovered discrete aurora: small, short-lived patches of aurora related to the crustal magnetic fields in Mars' southern hemisphere (Bertaux et al., 2005). MAVEN/IUVS discovered a second type called diffuse aurora (Schneider,

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Section: Conclusion and Discussionmentioning

confidence: 99%

Discrete Aurora on Mars: Insights Into Their Distribution and Activity From MAVEN/IUVS Observations

et al. 2021

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“…In spite of the considerable transport channel controlled by the vertical magnetic field lines, the effects of ion supply and solar wind energy transfer on ion escape cannot be neglected. The supply of ions can be affected by ionization efficiency (e.g., Dubinin et al 2017b;Cui et al 2018), whereas the energy input may control by the interplanetary magnetic field direction (e.g., Weber et al 2020;Sakai et al 2021) and solar wind conditions (e.g., Nilsson et al 2011;Ramstad et al 2015;Ramstad & Barabash 2021). However, this study only considers the typical solar wind conditions as well as the strength and direction of the interplanetary magnetic field.…”

Section: Discussionmentioning

confidence: 99%

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

Cao

et al. 2022

ApJ

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Ion escape from the atmosphere to space is one of the most likely reasons to account for the evolution of the Martian climate. Based on three-dimensional multifluid magnetohydrodynamic simulations, we investigated the impact of the magnetic inclination angle on O+ escape at low altitudes of 275–1000 km under the typical solar wind conditions. Numerical results showed that an outward ion velocity in the direction opposite to the electromagnetic (EM) force results in weak outward flux and leads to ions becoming trapped by the horizontal magnetic field lines at the local horizontal magnetic equator. Much of the EM force can be attributed to the Hall electric force. In the region of high absolute magnetic inclination angle, the outward ion velocity has the same direction as the EM force, which increases the outward flux and causes ions to diffuse upward along open magnetic field lines to higher altitude. In addition, the EM force is mainly provided by the electron pressure gradient force and the motional electric force. Global results for the magnetic inclination angle indicate that the strong crustal field regions in the southern hemisphere are mainly occupied by magnetic field lines with high absolute magnetic inclination angle, while horizontal field lines are dominant in the northern hemisphere, which leads to a higher O+ escape rate in the Martian southern hemisphere than in the northern, from altitudes of 275 to 1000 km. This is a significant advance in understanding the impact and mechanism of the Martian magnetic field directions on ion escape.

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“…Mars' crustal magnetic field intensity is strong enough to create a magnetic barrier against the solar wind, thereby creating a hybrid magnetosphere which consist of a (to first order) miniature Earth-like dipole field in the Southern Hemisphere surrounded by induced and draped field (DiBraccio et al, 2018;Dubinin et al, 1994;Xu et al, 2020). The presence of the crustal magnetic field further complicates the magnetic field topology (i.e., open, closed and draped field lines) and dynamics within the Martian plasma environment (Brain et al, 2007;Lillis & Brain, 2013;Xu et al, 2017Xu et al, , 2018Xu et al, , 2019Xu et al, , 2020Weber et al, 2020). As such, it becomes more relevant and important to ask the following question: where is the K-H unstable flow shear boundary at Mars?…”

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On the Growth and Development of Non‐Linear Kelvin–Helmholtz Instability at Mars: MAVEN Observations

et al. 2021

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In this study, we have analyzed Mars Atmosphere and Volatile EvolutioN (MAVEN) observations of fields and plasma signatures associated with an encounter of fully developed Kelvin–Helmholtz (K–H) vortices at the northern polar terminator along Mars' induced magnetosphere boundary. The signatures of the K–H vortices event are: (a) quasi‐periodic, “bipolar‐like” sawtooth magnetic field perturbations, (b) corresponding density decrease, (c) tailward enhancement of plasma velocity for both protons and heavy ions, (d) co‐existence of magnetosheath and planetary plasma in the region prior to the sawtooth magnetic field signature (i.e., mixing region of the vortex structure), and (e) pressure enhancement (minimum) at the edge (center) of the sawtooth magnetic field signature. Our results strongly support the scenario for the non‐linear growth of K–H instability along Mars’ induced magnetosphere boundary, where a plasma flow difference between the magnetosheath and induced‐magnetospheric plasma is expected. Our findings are also in good agreement with 3‐dimensional local magnetohydrodynamics simulation results. MAVEN observations of protons with energies greater than 10 keV and results from the Walén analyses suggests the possibility of particle energization within the mixing region of the K–H vortex structure via magnetic reconnection, secondary instabilities or other turbulent processes. We estimate the lower limit on the K–H instability linear growth rate to be ∼5.84 × 10−3 s−1. For these vortices, we estimate the instantaneous atmospheric ion escape flux due to the detachment of plasma clouds during the late non‐linear stage of K–H instability to be ∼5.90 × 1026 particles/s. Extrapolation of loss rates integrated across time and space will require further work.

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The Influence of Interplanetary Magnetic Field Direction on Martian Crustal Magnetic Field Topology

Cited by 34 publications

References 52 publications

Discrete Aurora on Mars: Insights Into Their Distribution and Activity From MAVEN/IUVS Observations

Discrete Aurora on Mars: Insights Into Their Distribution and Activity From MAVEN/IUVS Observations

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

On the Growth and Development of Non‐Linear Kelvin–Helmholtz Instability at Mars: MAVEN Observations

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The Influence of Interplanetary Magnetic Field Direction on Martian Crustal Magnetic Field Topology

Cited by 34 publications

References 52 publications

Discrete Aurora on Mars: Insights Into Their Distribution and Activity From MAVEN/IUVS Observations

Discrete Aurora on Mars: Insights Into Their Distribution and Activity From MAVEN/IUVS Observations

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

On the Growth and Development of Non‐Linear Kelvin–Helmholtz Instability at Mars: MAVEN Observations

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