Ways in which ICME sheaths differ from magnetosheaths

Abstract

Because the material that constitutes a coronal mass ejection expands as it propagates into interplanetary space (where it is referred to as an interplanetary coronal mass ejection, ICME), its sheath differs from other heliophysical sheaths in three ways: (1) the lateral deflection of the solar wind away from the nose of an ICME is reduced; (2) the solar wind tends to pile up in front of an ICME instead of flowing around it; and (3) the ICME sheath is thinner. (We refer here to ICME sheaths that have a preceding bow shock and that therefore are analogous to other heliophysical sheaths.) These three differences are explained here by physical arguments and illustrated with an MHD simulation.