# Numerical simulations of particle acceleration at interplanetary quasi-perpendicular shocks

## TL;DR

This study uses test particle simulations combined with observational data to investigate how quasi-perpendicular interplanetary shocks accelerate particles to high energies, highlighting the role of upstream speed and magnetic field orientation.

## Contribution

It introduces a backward-in-time simulation method to analyze particle acceleration at quasi-perpendicular shocks using real shock parameters and magnetic turbulence modeling.

## Key findings

- High upstream speed enhances particle acceleration efficiency.
- Quasi-perpendicular shocks can accelerate thermal particles to MeV energies.
- Magnetic field orientation with a component parallel to the shock normal influences acceleration.

## Abstract

Using test particle simulations we study particle acceleration at highly perpendicular ($\theta_{Bn}\geq 75^\circ$) shocks under conditions of modeling magnetic turbulence. We adopt a backward-in-time method to solve the Newton-Lorentz equation using the observed shock parameters for quasi-perpendicular interplanetary shocks, and compare the simulation results with $ACE$/EPAM observations to obtain the injection energy and timescale of particle acceleration. With our modeling and observations we find that a large upstream speed is responsible for efficient particle acceleration. Our results also show that the quasi-perpendicular shocks are capable of accelerating thermal particles to high energies of the order of MeV for both kappa and Maxwellian upstream distributions, which may originate from the fact that in our model the local background magnetic field has a component parallel to the shock normal.