Density Derivation Using Controlled Spacecraft Potential in Earth's
Magnetosheath and Multi-scale Fluctuation Analysis
Abstract
In-situ measurements from the Magnetospheric Multiscale (MMS) mission
are used to estimate electron density from spacecraft potential and
investigate compressive turbulence in the Earth’s magnetosheath. During
the MMS Solar Wind Turbulence Campaign in February 2019, the four MMS
spacecraft were arranged in a logarithmic line constellation enabling
the study of measurements from multiple spacecraft at varying distances.
We estimate the electron density from spacecraft potential for a time
interval in which the ion emitters actively control the potential. The
derived electron density data product has a higher temporal resolution
than the plasma instruments, enabling the examination of fluctuation for
scales down to the sub-ion range. The inter-spacecraft separations range
from 132 km to 916 km; this corresponds to scales of 3.5 to 24.1 ion
inertial lengths. The derived density and magnetic field data are used
to study fluctuations in the magnetosheath through time lags on a single
spacecraft and spatial lags between pairs of spacecraft over almost one
decade in scale. The results show an increase in anisotropy as the scale
decreases.