Interaction of rotational discontinuities with energetic ions in the precursor of the Earth’s bow shock

We combined in-situ solar wind observations by ARTEMIS and MMS missions with kinetic hybrid simulations to study the interaction of solar wind rotational discontinuities (RDs) with the foreshock of the Earth’s bow shock. We found that whistler modes excited by diffuse energetic particles were strongly coupled with RDs and lead to their temporary dissociation. At the same time, RDs trigger the steepening of whistler waves and the generation of ’shocklets’ - small localised shock-like structures, capable of trapping energetic particles and growing up by absorbing the particles energy.

Downstream Super-magnetosonic Plasma Jet Generation as a Direct Consequence of Shock Reformation

Earth's bow shock, resulting from the interaction of the super-magnetosonic solar wind and Earth's magnetic field, has been studied for over 50 years and serves as an ideal astrophysical laboratory to study collisionless shocks. The Earth's bow shock offers a unique opportunity to study it through in-situ measurements. 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 SLAMS, while at the shock and downstream, particle acceleration, magnetic reconnection and plasma jets can be observed. Here, using Magnetospheric Multiscale (MMS) we show the first in-situ evidence of super-magnetosonic 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.

Particle energisation and transport at collisionless shocks propagating through turbulent media.

<p>Shocks and turbulence are spectacular, ubiquitous phenomena and are crucial ingredients to understand the production and transport of energetic particles in several astrophysical systems. The interaction between an oblique, supercritical shock and fully developed plasma turbulence is here investigated by means of kinetic simulations, for different turbulence amplitudes. The role of pre-existing, upstream turbulence on plasma transport is addressed using a novel technique, relying on the coarse-graining of the Vlasov equation. We find that the upstream transport properties strongly depend on upstream turbulence strength, with patterns modulated by the presence of turbulent structures. These results are relevant for a variety of systems, ranging from the Earth's bow shock interacting with solar wind turbulence, to the largest scales of radio relics in galaxy clusters.</p>

Parallel velocity mixing yielding enhanced electron heating during magnetic pumping

Magnetic wave perturbations are observed in the solar wind and in the vicinity of Earth's bow shock. For such environments, recent work on magnetic pumping with electrons trapped in the magnetic perturbations has demonstrated the possibility of efficient energization of superthermal electrons. Here we also analyse the energization of such energetic electrons for which the transit time through the system is short compared with time scales associated with the magnetic field evolution. In particular, considering an idealized magnetic configuration we show how trapping/detrapping of energetic magnetized electrons can cause effective parallel velocity ( $v_{\parallel }$ -) diffusion. This parallel diffusion, combined with naturally occurring mechanisms known to cause pitch angle scattering, such as whistler waves, produces enhanced heating rates for magnetic pumping. We find that at low pitch angle scattering rates, the combined mechanism enhances the heating beyond the predictions of the recent theory for magnetic pumping with trapped electrons.