Parametric studies on traveling compression regions observed in the Earth’s magnetotail

Abstract

On the basis of the spontaneous fast reconnection model, the traveling compression region (TCR) is studied by magnetohydrodynamic simulations for various plasma parameters. Once the fast reconnection mechanism involving slow shocks builds up, the general features of TCR, observed by virtual satellites located in the simulation box, are in good agreement with actual satellite observations. Quantitatively, the TCR signature is not significantly influenced by plasma β, whereas its duration time is proportional to VAe−1, where VAe is the Alfvén velocity in the magnetic field region; also, the compression ratio of TCR is larger for the smaller plasma density ρe in the magnetic field region because of larger compressibility. In the diffusion region, resistive tearing is likely to occur, giving rise to multiple small-scale TCRs following the major TCR. For the uniform resistivity model, where the fast reconnection mechanism is not realized, any TCR signature cannot be observed. Hence, the TCR signature, observed in association with substorms, provides a definite evidence such that the fast reconnection mechanism is realized in the Earth’s magnetotail.