Comparative Analysis of Dayside Reconnection Models in Global Magnetosphere Simulations

TL;DR

This study compares various dayside magnetic reconnection models in Earth's magnetosphere using high-resolution simulations, assessing their accuracy in predicting reconnection locations under different solar wind conditions.

Contribution

It introduces a robust image processing method to evaluate and compare reconnection location models against magnetic separators in detailed magnetosphere simulations.

Findings

Models perform well with southward IMF, especially where reconnection rates are maximized.

Maximum magnetic shear model best maps separators in the cusp region with northward IMF.

Accounting for plasma flow shear improves model predictions under northward IMF.

Abstract

We test and compare a number of existing models predicting the location of magnetic reconnection at Earth's dayside magnetopause for various solar wind conditions. We employ robust image processing techniques to determine the locations where each model predicts reconnection to occur. The predictions are then compared to the magnetic separators, the magnetic field lines separating different magnetic topologies. The predictions are tested in distinct high-resolution simulations with interplanetary magnetic field (IMF) clock angles ranging from 30 to 165 degrees in global magnetohydrodynamic simulations using the three-dimensional Block-Adaptive Tree Solarwind Roe-type Upwind Scheme (BATS-R-US) code with a uniform resistivity, although the described techniques can be generally applied to any self-consistent magnetosphere code. Additional simulations are carried out to test location model dependence on IMF strength and dipole tilt. We find that most of the models match large portions of the magnetic separators when the IMF has a southward component, with the models saying reconnection occurs where the local reconnection rate and reconnection outflow speed are maximized performing best. When the IMF has a northward component, none of the models tested faithfully map the entire magnetic separator, but the maximum magnetic shear model is the best at mapping the separator in the cusp region where reconnection has been observed. Predictions for some models with northward IMF orientations improve after accounting for plasma flow shear parallel to the reconnecting components of the magnetic fields. Implications for observations are discussed.