Mesoscale Structure and Properties of the Terrestrial Magnetotail Plasma Sheet From the Magnetospheric Multiscale Mission

摘要

Using Magnetospheric Multiscale mission (MMS) orbits in the Earth's magnetotail from 2017 to 2020, plasma conditions and the 3D spatial structure of inner-magnetotail plasma environments (with a focus on the plasma sheet (PS)) are studied with different approaches. Threshold conditions for distinguishing the PS, PS boundary layers, and lobes are derived from the statistical properties of background plasma parameters. Our results support previous studies that employed similar methods using Cluster data. However, stronger currents are observed in both the lobes and PS, likely due to the smaller spacecraft separation (less than or similar to 70 km) that can resolve thin electron-scale currents. Threshold conditions are used together with magnetic field and electric field measurements to image the spatial structure of the PS. Results are in good agreement with a global neutral sheet model based on solar wind conditions and magnetospheric configurations. Furthermore, the Earth's dipole tilts toward the Sun around June solstice, which warps the magnetotail as much as similar to 2-4 R-E in Z geocentric solar magnetospheric. This warping effect is relaxed toward September equinox. Consequently, as MMS travels through the magnetotail from dawn to dusk during this period, there is an apparent dawn-dusk asymmetry in plasma conditions between June and September. Kink-like flapping waves and interplanetary magnetic field twisting are other mesoscale processes attributed with a few R-E of flaring near the flanks. These findings reveal important insights into the mesoscale structure and dynamics of the magnetotail. Plain Language Summary Data from 4 years of observations by NASA's MMS mission are used to statistically identify distinctive regions within the Earth's magnetospheric tail. This study reveals insights into the spatial structure of this "magnetotail" and seasonal variations attributed with changes in the Earth's magnetic field configurations, particularly those of the orientation of the Earth's dipole. Our results agree with reported findings from ESA's Cluster mission. However, certain aspects unique to MMS lead to some improved measurements and features relating to MMS orbital design. The presented results are highly beneficial to future large statistical studies with MMS data.