The electrodynamic aerobraking in atmospheric earth entries is simulated using a computational fluid dynamics analysis to predict the magnetic interaction parameter Q and electrodynamic force at high altitudes H≥70-100 km. As a result, Q is found to be much larger than 1 in altitudes lower than 92 km. In accordance with these large Q, the large electrodynamic force generates at H ≤ 84 km. However, the electrodynamic force suddenly vanishes at H≥86 km in spite of Q》1. Accordingly, the electrodynamic aerobraking is found to have a critical altitude at which the electrodynamic force suddenly vanishes. A time-accurate computation is performed to clarify the mechanism of this sudden change at the critical altitude. The computation reveals that the cause originates from two mechanisms in rarefied flows with a strong Hall effect at high altitudes. The first mechanism is initial Joule heating which occurs at a shock front and is required to initiate an electrodynamic shock layer enlargement. The second is the avalanche ionization inside the shock layer which is triggered by the thermal equilibrium process progressing with the electrodynamic shock layer enlargement.
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