Shocks are one of nature’s most powerful particle accelerators and have been connected to relativistic electron acceleration and cosmic rays. Upstream shock observations include wave generation, wave-particle interactions and magnetic compressive structures, while at the shock and downstream, particle acceleration, magnetic reconnection and plasma jets can be observed. Here, using Magnetospheric Multiscale (MMS) we show in-situ evidence of high-speed downstream flows (jets) generated at the Earth’s bow shock as a direct consequence of shock reformation. Jets are observed downstream due to a combined effect of upstream plasma wave evolution and an ongoing reformation cycle of the bow shock. This generation process can also be applicable to planetary and astrophysical plasmas where collisionless shocks are commonly found.

We use Cluster multi-point measurements to investigate the different magnetosheath plasma environments according to the upstream conditions. 10• Local magnetosheath measurements can be used to characterize and classify the 11 magnetosheath plasma with respect to upstream conditions. 12• We suggest future extensions to the methodology.

As the supersonic solar wind (SW) approaches Earth, it interacts with the planet's magnetic field, forming a bow shock. Downstream of the shock, the magnetosheath (MSH) region forms, which is a highly turbulent plasma environment where several phenomena co-exist. One of these phenomena is the so called MSH jets and during the last two decades, they have drawn considerable attention (Plaschke et al., 2018). These jets are transient dynamic pressure enhancement with respect to the downstream ambient background plasma. The dynamic pressure enhancements can be due to either a velocity and/or density increase (Archer et al., 2012).One of the most important features that determines the properties of jets is whether they are found in the so called Quasi-parallel (Qpar) or Quasi-perpendicular (Qperp) MSH. These regions are, respectively, the plasma downstream of a Qpar or a Qperp shock crossing. Typically, the distinction between Qpar and Qperp shock crossings is based on the angle between the upstream Interplanetary Magnetic Field vector and the bow shock normal vector. If the angle is less than 45°, we call the crossing Qpar, while if it is greater, we call it Qperp. The downstream MSH of the Qpar shocks is more turbulent, exhibits lower temperature anisotropy, and contains more high-energy particles (Fuselier, 1994;Karlsson et al., 2021;. The complexity of Qpar shocks also extends upstream of the shock to the foreshock region where non-linear ULF waves, field-aligned beams and wave-particle interaction regions are observed (

We discuss the influence of charged dust on radar observations in the Earth ionosphere. This region in the upper Earth atmosphere can be described as a partially ionized, low-temperature plasma. Plasma parameters vary by orders of magnitude spatially and in time. Dust particles influence the charge balance, in some cases dusty plasma condition is met. The polar mesospheric echoes are an example of dust plasma interactions observed with radar. The mesosphere is a region where atmospheric temperature decreases with altitude and can reach frost point temperature.The formation of the polar mesospheric radar echoes involves neutral atmosphere dynamics, which is latitude dependent and it involves charged dust particles, especially icy dust that forms in the polar summer mesosphere. Charged dust can also influence incoherent scatter that results from electromagnetic waves scattering off electrons, where the electrons are coupled to other charged components. Observers rarely report charged dust signatures in the incoherent scatter spectra; we show that there is a good chance for doing so with improved observations. The incoherent scatter can possibly also be used to estimate the amount of charged dust in the direct vicinity of a meteor, as we show based on the order of magnitude considerations. This prospect of new observational results makes theoretical investigations of radio-wave scattering in the presence of charged dust with size distributions worthwhile.

Abstract. Solar wind magnetic holes are localized depressions of the magnetic field strength, on timescales of seconds to minutes. We use Cluster multipoint measurements to identify 26 magnetic holes which are observed just upstream of the bow shock and, a short time later, downstream in the magnetosheath, thus showing that they can penetrate the bow shock and enter the magnetosheath. For two magnetic holes, we show that the relation between upstream and downstream properties of the magnetic holes are well described by the MHD (magnetohydrodynamic) Rankine–Hugoniot (RH) jump conditions. We also present a small statistical investigation of the correlation between upstream and downstream observations of some properties of the magnetic holes. The temporal scale size and magnetic field rotation across the magnetic holes are very similar for the upstream and downstream observations, while the depth of the magnetic holes varies more. The results are consistent with the interpretation that magnetic holes in Earth's and Mercury's magnetosheath are of solar wind origin, as has previously been suggested. Since the solar wind magnetic holes can enter the magnetosheath, they may also interact with the magnetopause, representing a new type of localized solar wind–magnetosphere interaction.