Different Types of Ion Populations Upstream of the 2013 October 8 Interplanetary Shock

Abstract

We show for the first time that different types of suprathermal ion distributions may exist upstream of a single interplanetary shock. ACE and the two ARTEMIS satellites observed a shock on 8 October 2013. The ARTEMIS P1 and P2 spacecraft first observed field-aligned ions (P1) and gyrating ions (P2) arriving from the shock. These were followed by intermediate ions and later by a diffuse population. At the location of the P2 the shock exhibited an Alfvénic Mach number of M A =5.7 and was marginally quasi-perpendicular, (θ Bn =47 • ). At P1 spacecraft the shock was weaker (M A =4.9) and more perpendicular (θ Bn =61 • ). Consequently the observed suprathermal ion and ultra low frequency wave properties were somewhat different. At P2 the ULF waves are more intense and extend farther upstream from the shock. The energies of field aligned and gyrating ions in the shock rest frame were ∼20 keV, which is much more than in the case of the stronger (M A =6-7) Earth's bow-shock, where they are less than 10 keV.Corresponding author: Primož Kajdič primoz@geofisica.unam.mx 2 Kajdič et al.

Multispacecraft Study of the Interaction Between an Interplanetary Shock and a Solar Wind Flux Rope

“…The ion foreshock observed by Cluster has complex ion distributions including beam and diffuse ions. This is in agreement with previous observations by Kajdič et al (2017) who described a variety of ion 10.1029/2019JA026748 distributions upstream of a single IP shock in the data of the ARTEMIS (Angelopoulos, 2011) spacecraft. These authors observed upstream ion distributions that changed from initial field-aligned (ARTEMIS-1) or gyrating (ARTEMIS-2) to intermediate and diffuse distributions.…”

“…• Shock interaction with small flux ropes in the solar wind can change shock geometry and impact ion injection at the shock • Interplanetary shock interaction with flux ropes can modify the upstream and downstream regions • Fluxes of particles with energy up to 125 keV are affected by the FRLS-shock interaction, modulating associated ESP events and evolution of ion distributions upstream of an IP shock were discussed by Kajdič et al (2017). This study showed that different ion populations can be observed upstream of a single IP shock with M A ∼ 4.…”

“…The microphysics and properties of IP shocks and regions associated to them have been studied by several authors (Blanco-Cano et al, 2016;Kajdič et al, 2012Kajdič et al, , 2017Krauss-Varban et al, 2008;Russell et al, 1983;Wilson et al, 2009Wilson et al, , 2012, but compared to the Earth's bow shock, we still know little about the detailed structure, ion distributions associated with these shocks, shock interaction with solar wind structures, shock reformation and rippling, etc.…”

First Observations of Irregular Surface of Interplanetary Shocks at Ion Scales by Cluster

“…Rippling was observed at the Earth's bow-shock by several authors by using multi-spacecraft data from Cluster [Horbury et al, 2002, 2001, Lobzin et al, 2008, Moullard et al, 2006 and Magnetospheric Multiscale (MMS) mission [Gingell et al, 2017, Johlander et al, 2016. As for the IP shocks, several authors [i.e., Kajdič et al, 2017, Koval & Szabo, 2010, Pulupa & Bale, 2008, Russell & Alexander, 1984, Russell et al, 2000, Szabo, 2005 discussed and/or observed their non-planar structure at scales of several tens of Earth radii (R E ), but never at ion scales.…”

Shock Drift Acceleration of Ions in an Interplanetary Shock Observed by MMS

“…Lario et al (2019) have described IP shock observations where enhancements in ions less than 10 keV appeared close to the shock. Similarly, ion populations of ~20 keV associated with an IP shock have been recorded by the ARTEMIS spacecraft (Kajdič et al 2017). In this paper we report experimental evidence of SDA in a population of 2-7 keV ions observed ahead of an interplanetary (IP) shock.…”