Properties of a large-scale flux rope and current sheet region on the dayside of Mars: MGS MAG/ER and MEX ASPERA-3 ELS observations

Abstract

a b s t r a c tWe present dual spacecraft observations by MGS MAG/ER and MEX ASPERA-3 ELS of a large-scale magnetic flux rope on the dayside of Mars that occurs in close proximity to the crustal magnetic fields and a dayside current sheet region. A current sheet (including the large-scale flux rope) was observed on repeated MGS orbits when the draped solar wind magnetic field present in the ionosphere had a þB y component (in MSO). Minimum Variance Analysis (MVA) of the large-scale flux rope and two current sheet crossings that occur after show a common peak in magnetic field along the intermediate variance direction, indicating the normal component of a reconnecting current sheet. All repeated orbits demonstrated evidence of a plasma boundary by the decrease in electron differential flux above 100 eV when moving into regions dominated by the crustal magnetic field, and coincided with the measured magnetic field strength being double the undisturbed crustal magnetic field. We argue this forms evidence of magnetic reconnection between crustal magnetic fields and draped solar wind magnetic field (from ionosphere or magnetosheath) at a ''mini-magnetopause'' type boundary on the dayside of Mars. Similar electron pitch angle distributions observed during the large-scale flux rope, current sheet crossings, and regions of radial crustal magnetic field, suggest these regions share a common magnetic field topology for the trapping of magnetosheath particles on open crustal magnetic fields on the dayside of Mars. As such, indicates a trapping quadrupole magnetic field exist either at the magnetic reconnection X-line region or where open crustal magnetic fields meet oppositely directed solar wind magnetic field. At a time when the draped solar wind magnetic field present in the ionosphere was weaker in strength, the current sheet crossing was observed over an extended region of 2000 km. The extended current sheet demonstrated properties of a hot diamagnetic region and features of a mirror mode structure or magnetic hole, the first time such a structure has been found in the ionosphere of Mars. Observations suggests lower energy electrons could be accelerated by a local process of perpendicular heating/pitch angle diffusion and supports similar results at the Earth's polar cusp reported by Nykyri et al. (Nykyri et al. [2012]. J. Atmos. Sol-Terr. Phys. 87, 70). Such large scale and energetic structures are usually associated with regions beyond a planet's ionosphere, and the occurrence within the ionosphere of Mars may have an important impact on escape processes and the evolution of the martian atmosphere.

MAVEN observations of a giant ionospheric flux rope near Mars resulting from interaction between the crustal and interplanetary draped magnetic fields

“…The actual spatial difference between these commensurable orbits is smaller than ∼300 km. Analogous investigations were performed solely for the MGS measurements by Soobiah et al [].…”

“…orbits is smaller than ∼300 km. Analogous investigations were performed solely for the MGS measurements by Soobiah et al [2014]. Figure 1 shows an overview of the MAVEN magnetic field measurements when the spacecraft is at altitudes lower than 1000 km on orbit #1094.…”

Misbehaving High‐Energy Electrons: Evidence in Support of Ubiquitous Wave‐Particle Interactions on Dayside Martian Closed Crustal Magnetic Fields

“…These studies suggest that there are unstudied physical processes producing isotropic and trapped distributions on closed crustal field lines, as conservation of adiabatic invariants and collisional scattering predicts a source cone distribution. More recently, Soobiah et al () observed field‐aligned low‐energy electrons and trapped high‐energy electrons inside of an ionospheric flux rope and, during times of radial field lines, with low‐energy PADs that indicate they are open. The electron impact ionization cross sections for the primary upper atmosphere neutral species, CO 2 and O, peak around 100 eV (Itikawa, ; Thompson et al, ).…”

Survey of magnetic reconnection signatures in the Martian magnetotail with MAVEN

“…Injection and trapping of electrons on closed magnetic field lines have been observed near the Martian crustal magnetic fields [ Brain et al , ; Ulusşen and Linscott , ; Harada et al , ; Xu et al , ]. Magnetic flux ropes can be formed by reconnection between draped interplanetary fields in the induced tail current sheets, between crustal and draped fields, or between neighboring crustal fields [ Brain et al , ; Briggs et al , ; Beharrell and Wild , ; Eastwood et al , ; Hara et al , , ; Soobiah et al , ; DiBraccio et al , ]. In order to evaluate the role of reconnection in their generation processes, it is necessary to characterize the basic properties of magnetic reconnection at Mars based on in situ observations of particle and field signatures around X lines.…”