Magnetosheath interaction with high latitude magnetopause: Dynamic flow chaotization

Exploration of plasma–plasma interactions at the high-latitude magnetopause versus a simulated sheared current sheet with strong fluctuations of realistic spectral shape, revealed a new type of dynamic equilibrium, in which nonlinear disturbances serve as an effective obstacle for 80% of the incident magnetosheath ions, providing also the exchange by ∼10% of plasma particles with the stagnant high-beta boundary layer in the minimum field region over the polar cusps. The measured waves, reflected upstream by the boundary, interact in the 3-wave manner with the magnetosonic (MS) fluctuations of the incident flow, resulting in their amplification and then decay into accelerated MS-jets and Alfven waves, driving decelerated flows at the Alfven speed. This impulsive momentum loss via the MS-jets contributes in the average flow bend around the magnetosphere. The leading jet appearance is suggested to be phase-synchronized with both the initial MS fluctuations and nonlinear cascades upstream at the magnetopause, which constitutes the wavy obstacle with multiple decays into the smaller MS-jets and Alfvenic flows. High dynamic pressure in the MS-jets does not fit their acceleration by a reconnection; instead the jets are able to initiate the driven reconnection in the process of interaction with a downstream magnetopause. The acceleration of the MS-jets is consistent with a Fermi-type mechanism, in which electric wave-trains play the role of a moving non-continuous ‘wall’. Estimations of the jet scales from the approach of a nonlinear Cherenkov resonance conforms 2–3 reflections of the jet from the ‘wall’ before overcoming the ‘wall’ potential barrier. We demonstrate quantitative agreement of the acceleration of the leading MS-jet in the process of inertial ion drift in variable electric fields. Current sheets, generated due to opposite sign of the ion and electron inertial drift, can account for the intermittency of the TBL fluctuations.