Determining the Near‐Instantaneous Curvature of Earth's Bow Shock Using Simultaneous IBEX and MMS Observations

The Interstellar Boundary Explorer (IBEX) mission provides a unique opportunity to study Earth's magnetosphere on a global scale via energetic neutral atom imaging. Due to the orbital configuration, IBEX is in a side-viewing vantage point relative to the magnetosphere for a few months every year. This allows the Earth's magnetosphere to be imaged in the X-Z geocentric solar ecliptic (GSE) plane. Using IBEX observations and near-simultaneous in-situ observations of Earth's bow shock (BS) from the Magnetospheric Multiscale mission, we determine the curvature of Earth's BS in the X-Z GSE plane for 22 instances. We then compare the curvature to different upstream solar wind parameters in order to identify correlations with the contemporary physical conditions. We find that the solar wind dynamic pressure, as well as the interplanetary magnetic field (IMF) strength, X-Y, and Y-Z components are all linearly related to the curvature. We then investigate the time scales over which these correlations persist using variable time windows over which the upstream parameters are averaged. Lastly, we investigate the asymmetry of the BS in the X-Z plane by comparing an asymmetry measure with different solar wind parameters. We find that the magnetic tension force from the IMF deflects the BS, and thus the underlying magnetopause obstacle. The results presented here provide the first near-instantaneous observations of Earth's BS on a global scale, show the importance of IMF on generating asymmetries, and provide a basis for future modeling and observational studies of the BS. Plain Language Summary Shock waves are a universal phenomenon found throughout space and they are capable of accelerating particles to high energies. Understanding how shock geometry responds to different characteristics of the upstream plasma is crucial toward understanding the production of energetic particles and cosmic rays. The Earth's bow shock (BS) is the boundary where the incident supersonic solar wind plasma is first deflected and decelerated as it encounters Earth's magnetosphere. In this work we characterize the global shape of the BS as it responds to incident solar wind and interplanetary magnetic field parameters. This work provides a basis for future modeling and observational studies of the BS.