Tracking the Subsolar Bow Shock and Magnetopause

• Published in: Journal of geophysical research. Space physics Vol. 127; no. 9
• Main Authors: Sibeck, D. G., Silveira, M. V. D., Collier, M. R.
• Format: Journal Article
• Language: English
• Published: Washington Blackwell Publishing Ltd 01-09-2022
• Subjects: bow shock; Empirical models; Fluid flow; Mach number; Magnetic reconnection; Magnetohydrodynamic models; Magnetohydrodynamic simulation; Magnetopause; Magnetosheath; Nose; Plasma; Solar wind; Solar wind velocity; Spacecraft; Velocity; Wind speed; Wind velocities
• ISSN: 2169-9380; 2169-9402
• DOI: 10.1029/2022JA030704

Global magnetohydrodynamic models predict that plasma velocities vary almost linearly from 0 km s−1 at the nose of the stationary magnetopause on the stagnation streamline to a limiting value of 0.25 VSW for high solar wind Alfvénic Mach numbers at the nose of the bow shock, where VSW is the solar wind velocity. This paper presents a proof‐of‐concept study showing how two‐point measurements of the plasma velocity in the subsolar magnetosheath can be used to determine gradients in the plasma velocity and consequently the steady‐state or slowly moving locations of both the nose of the magnetopause and the nose of the bow shock. The results may be of use to those binning magnetosheath observations to develop empirical models, those testing models for magnetopause erosion or deposition in response to magnetic reconnection, and those determining the stand‐off distance of the bow shock as a function of solar wind conditions.
Plain Language Summary
We employ dual‐spacecraft observations to determine the radial gradient in plasma velocity through the subsolar magnetosheath. Relying upon results from global magnetohydrodynamic simulations indicating that this gradient is linear, we use it to determine the locations of the bow shock and magnetopause positions.
Key Points
Plasma velocities vary almost linearly along the stagnation streamline from the nose of the magnetopause to the nose of the bow shock
Magnetohydrodynamic theory and models predict magnetosheath plasma velocities at the noses of the bow shock and magnetopause
Radial gradients in the plasma velocity define the locations of the stationary or slow‐moving subsolar magnetopause and bow shock