Journal Article

Interplay of Three‐Dimensional Instabilities and Magnetic Reconnection in the Explosive Onset of Magnetospheric Substorms

Totorica, Samuel R., Bhattacharjee, Amitava

2023

Overview

Magnetospheric substorms are preceded by a slow growth phase of magnetic flux loading and current sheet thinning in the tail. Extensive data sets have provided evidence of the triggering of instabilities at substorm onset, including magnetic reconnection and ballooning instabilities. Using an exact kinetic magnetotail equilibrium we present particle‐in‐cell simulations which capture the explosive nature of substorms through a disruption of the dipolarization front by the ballooning instability. We use self‐consistent particle tracking to determine the nonthermal particle acceleration mechanisms. Plain Language Summary Magnetospheric substorms are events featuring bursty flows of magnetized plasma, highly energetic particles, and intense polar auroras. Substorms play a key role in the response of the magnetosphere to variations in the incoming solar wind. The Earth's magnetic field lines are like elastic strings, and when they snap charged particles can be accelerated to high energies. Additionally, when there is enough plasma pressure pushing against the magnetic field, the magnetic field lines can develop an unstable oscillation known as a “ballooning instability” which is driven by the alignment of the plasma pressure gradient with magnetic field curvature. Using computer simulations that follow the trajectories of billions of particles in the Earth's magnetosphere and compute their self‐consistent electromagnetic forces, we show the importance of the interplay between reconnection and ballooning in the onset of substorms and acceleration of charged particles to high energies. These results have strong implications for the development of accurate models to predict space weather events and mitigate their damaging effects on critical infrastructure. Key Points For the first time, an exact kinetic magnetotail equilibrium is used to model magnetospheric substorm onset Comparing 2D and 3D simulations reveals the importance of the coupling between magnetic reconnection and the kinetic ballooning instability Self‐consistent particle trajectories are analyzed for the first time in a realistic fully kinetic magnetotail configuration

• Publisher: John Wiley & Sons, Inc,American Geophysical Union (AGU),Wiley
• Subject: Acceleration / ASTRONOMY AND ASTROPHYSICS / Auroras / Balloons / Charged particle acceleration / Charged particles / Critical infrastructure / Current sheets / Earth / Earth magnetosphere / Electromagnetic forces / Energetic particles / Geomagnetic field / Magnetic field / Magnetic fields / Magnetic flux / Magnetic reconnection / Magnetospheric substorms / Magnetotails / Mathematical models / Particle acceleration / Particle tracking / Plasma pressure / Pressure gradients / Solar magnetic field / Solar wind / Space weather