# Coronal rain in magnetic bipolar weak fields

## TL;DR

This study uses 3D radiative MHD simulations to explore the formation, dynamics, and observational signatures of coronal rain in bipolar magnetic fields, revealing detailed physical processes and matching real solar observations.

## Contribution

It provides a comprehensive simulation-based analysis of coronal rain formation, dynamics, and multi-stranded structures, advancing understanding of solar atmospheric phenomena.

## Key findings

- Coronal rain blobs are mainly small, less than 10^10 g.
- Blobs fall along magnetic loops, showing non-uniform velocities and shearing.
- Simulated images match observations, showing dark and bright rain features.

## Abstract

We intend to investigate the underlying physics for the coronal rain phenomenon in a representative bipolar magnetic field, including the formation and the dynamics of coronal rain blobs. With the MPI-AMRVAC code, we performed three dimensional radiative magnetohydrodynamic (MHD) simulation with strong heating localized on footpoints of magnetic loops after a relaxation to quiet solar atmosphere. Progressive cooling and in-situ condensation starts at the loop top due to radiative thermal instability. The first large-scale condensation on the loop top suffers Rayleigh-Taylor instability and becomes fragmented into smaller blobs. The blobs fall vertically dragging magnetic loops until they reach low beta regions and start to fall along the loops from loop top to loop footpoints. A statistic study of the coronal rain blobs finds that small blobs with masses of less than 10^10 g dominate the population. When blobs fall to lower regions along the magnetic loops, they are stretched and develop a non-uniform velocity pattern with an anti-parallel shearing pattern seen to develop along the central axis of the blobs. Synthetic images of simulated coronal rain with Solar Dynamics Observatory Atmospheric Imaging Assembly well resemble real observations presenting dark falling clumps in hot channels and bright rain blobs in a cool channel. We also find density inhomogeneities during a coronal rain "shower", which reflects the observed multi-stranded nature of coronal rain.