Abstract
Abstract. We present multi spacecraft measurements in the magnetosheath (MSH) and in the solar wind (SW) by Interball, Cluster and Polar, demonstrating that coherent structures with magnetosonic Mach number up to 3 – Supermagnetosonic Plasma Streams (SPS) – generate transient and anomalous boundary dynamics, which may cause substantial displacements of the magnetospheric boundaries and the riddling of peripheral boundary layers. In this regard, for the first time, we describe a direct plasma penetration into the flank boundary layers, which is a candidate for being the dominant transport mechanism for disturbed MSH periods. Typically SPS's have a ram pressure exceeding by several times that of the SW and lead to long-range correlations between processes at the bow shock (BS) and at the magnetopause (MP) on one side and between MSH and MP boundary layers on the other side. We demonstrate that SPS's can be observed both near the BS and near the MP and argue that they are often triggered by hot flow anomalies (HFA), which represent local obstacles to the SW flow and can induce the SPS generation as a means for achieving a local flow balance. Finally, we also discuss other causes of SPS's, both SW-induced and intrinsic to the MSH. SPS's appear to be universal means for establishing a new equilibrium between flowing plasmas and may also prove to be important for astrophysical and fusion applications.
Highlights
Recent observations by the Cluster, THEMIS and Interball-1 spacecraft indicate the presence of very fast plasma streams inside the MSH
The Supermagnetosonic Plasma Streams (SPS)’s, do not belong to a steady state MSH flow, but are transient periods of enhanced plasma flow. They have been found at all radial distances between the bow shock and the MP with the flow direction often being closer to the original solar wind (SW) flow vector than to the average MSH flow
Such jets have little to do with reconnection as their source, since their kinetic energy density by far exceeds the magnetic energy density
Summary
Recent observations by the Cluster, THEMIS and Interball-1 spacecraft (see Savin et al, 2006, 2008, 2010, 2011; Amata et al, 2006, 2011; Hietala et al, 2009; Jacobsen et al, 2009; Zhang et al, 2009, and references therein) indicate the presence of very fast plasma streams inside the MSH. The SPS’s, do not belong to a steady state MSH flow, but are transient periods of enhanced plasma flow They have been found at all radial distances between the bow shock and the MP with the flow direction often being closer to the original SW flow vector than to the average MSH flow. Such jets have little to do with reconnection as their source, since their kinetic energy density by far exceeds the magnetic energy density. This finding supports the phenomenological model of Savin et al (2011) and is not in contradiction with the model of Hietala et al (2009)
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