Density profile in the magnetosheath adjacent to the magnetopause Original Research Article

The structure of the magnetopause is a subject of intensive study for many years. The experimental and theoretical results reveal a layer of gradually decreased plasma density created in front of the low-latitude magnetopause when the magnetic shear across the magnetopause is sufficiently low. Our study of three INTERBALL-1/MAGION-4 passes shows that a similar profile of the plasma density in the vicinity of the flank magnetopause can be observed regardless of the magnetic shear and/or north/south orientation of the magnetic field. The first pass resembles all features reported for the Plasma Depletion Layer (PDL) adjacent to the low-shear magnetopause (plasma depletion and corresponding pile-up of the magnetic field strength) but a magnetic shear across the magnetopause was as high as 90°. The second event recorded at the nightside low-latitude magnetopause exhibits even a higher magnetic shear, near 180°, but a density decrease is not accomplished with any enhancement of the magnetic field. The third example shows low-shear dayside magnetopause crossing without any indications of a density decrease in front of the magnetopause. Based on the analysis of these three cases, we conclude that a formation of the magnetosheath density profile in regions adjacent to the magnetopause can be influenced by other factors as a presence of high-energy particles.