Shocklets, SLAMS, and field-aligned ion beams in the terrestrial foreshock

TL;DR

This study uses Wind spacecraft data to show that SLAMS act like local shocks, reflecting ions and creating field-aligned beams, with significant ion and electron heating observed within these structures.

Contribution

It demonstrates that SLAMS can locally produce FABs, challenging the previous view that FABs originate solely from the bow shock.

Findings

SLAMS act as local quasi-perpendicular shocks reflecting ions.

FABs have energies around 80-850 eV and are associated with SLAMS.

Significant ion and electron heating occurs within shocklets and SLAMS.

Abstract

We present Wind spacecraft observations of ion distributions showing field-aligned beams (FABs) and large-amplitude magnetic fluctuations composed of a series of shocklets and short large-amplitude magnetic structures (SLAMS). We show that the SLAMS are acting like a local quasi-perpendicular shock reflecting ions to produce the FABs. Previous FAB observations reported the source as the quasi-perpendicular bow shock. The SLAMS exhibit a foot-like magnetic enhancement with a leading magnetosonic whistler train, consistent with previous observations. The FABs are found to have T_b ~ 80-850 eV, V_b/V_sw ~ 1-2, T_{b,perp}/T{b,para} ~ 1-10, and n_b/n_i ~ 0.2-14%. Strong ion and electron heating are observed within the series of shocklets and SLAMS increasing by factors \geq 5 and \geq 3, respectively. Both the core and halo electron components show strong perpendicular heating inside the feature.