Numerical MHD modeling of propagation of interplanetary shock through the magnetosheath

Abstract

[1] Propagation of an interplanetary (IP) shock through the bow shock and magnetosheath is studied using numerical results of a three-dimensional MHD model of the magnetosheath. According to already published theoretical studies, a fast forward shock passing through the bow shock would generate a train of new discontinuities including a slow expansion wave, a contact discontinuity, and a slow reversed shock. We have found that these particular discontinuities propagate with similar velocities and thus they cannot be distinguished in our calculations, and we observe one discontinuity that combines properties of all of them. We suggest that the same would be true for an analysis of experimental data. We have simulated three different ways of the magnetopause response to the IP shock. A comparison of these runs reveals that the magnetopause reaction defines the mode of reflected waves. Assuming a fast earthward motion of the magnetopause, about 240 km s À1 or more, we obtain that a fast rarefaction wave would propagate from the magnetopause toward the bow shock, while a slower magnetopause motion would result in a fast reversed shock. On the other hand, the speed of the IP shock propagation does not depend on the magnetopause response, and all three model runs confirm a deceleration of the modeled IP shock front in the magnetosheath in course of its motion from the subsolar region to the magnetosheath flanks.

Interplanetary shock transmitted into the Earth's magnetosheath: Cluster and Double Star observations

“…It is very interesting to stress that the numerical simulations by Samsonov et al (2006) are generally consistent with the observations reported in the present andŠafránková et al (2007) and Přech et al (2008) studies. Indeed, Samsonov et al (2006) have found a compound discontinuity (comprising a forward slow expansion wave, a contact discontinuity and a reversed slow shock) which travels, at nearly the local plasma flow speed, behind the transmitted IS and which is generated by the interaction between the IS and the bow shock. This discontinuity is mainly charatherized by an increase of n, a decrease of T and a weak increase of B.…”

“…8 and 11). In a particular case simulated by Yan and Lee (1996) and Samsonov et al (2006), this discontinuity was found to be a combination of a forward slow expansion wave, a contact discontinuity, and a reversed slow shock. The three discontinuities travel with similar speeds and can not be resolved in the 3-D simulations .…”

“…The Grib (1982) theoretical findings have been confirmed by later MHD simulations both in one-dimensional (Yan and Lee, 1996) and in full three-dimensional case close to the Sun-Earth line . Moreover, Samsonov et al (2006) have shown that the speeds of the forward slow expansion wave, of the contact discontinuity and of the reverse slow shock are all very close. In the experimental data, therefore, a compound discontinuity (i.e.…”

“…Our analysis provides some interesting quantitative results regarding the motion of the transmitted IS, of the bow shock and two secondary discontinuities generated by the IS-magnetosphere interactions. Moreover, we discuss our results also with the support of a specially set simulation based on the local model by Samsonov et al (2006) …”

Influence of the foreshock of the Earth’s bow shock on the interplanetary shock propagation during their mutual interaction

“…Although MHD modeling achieved a particular success in description of the IP shock interaction with the bow shock (e.g., Zhuang et al, 1981;Grib, 1982;Yan and Lee, 1996;Samsonov et al, 2006), the models have two significant limitations: (1) their present codes can be applied only to the shocks perpendicular to the solar wind velocity and (2) they cannot account for foreshock effects.…”