# MHD simulations of the eruption of coronal flux ropes under coronal streamers

## TL;DR

This paper uses 3D MHD simulations to study how coronal flux ropes under streamers erupt, revealing different eruption mechanisms like kink instability and torus instability depending on streamer size and flux rope twist.

## Contribution

It introduces a detailed simulation framework for flux rope eruptions under streamers, highlighting the roles of twist, streamer width, and instabilities in eruption dynamics.

## Key findings

- Flux ropes develop kink instability in broad streamers leading to eruptions.
- Prominence condensations form due to radiative cooling in twisted flux ropes.
- Eruptions occur via kink instability or torus instability depending on streamer size and flux rope twist.

## Abstract

Using three-dimensional magnetohydrodynamic (MHD) simulations, we investigate the eruption of coronal flux ropes underlying coronal streamers and the development of a prominence eruption. We initialize a quasi-steady solution of a coronal helmet streamer, into which we impose at the lower boundary the slow emergence of a part of a twisted magnetic torus. As a result a quasi-equilibrium flux rope is built up under the streamer. With varying sizes of the streamer and the different length and total twist of the emerged flux rope, we found different scenarios for the evolution from quasi-equilibrium to eruption. In the cases with a broad streamer, the flux rope remains well confined until there is sufficient twist such that it first develops the kink instability and evolves through a sequence of kinked, confined states with increasing height until it eventually develops a "hernia-like" ejective eruption. For the significantly twisted flux ropes, prominence condensations form in the dips of the twisted field lines due to run-away radiative cooling. Once formed, the prominence carrying field becomes significantly non-force-free due to the prominence weight despite being low plasma $\beta$. As the flux rope erupts, we obtain the eruption of the prominence, which shows substantial draining along the legs of the erupting flux rope. The prominence may not show a kinked morphology even though the flux rope becomes kinked. On the other hand, in the case with a narrow streamer, the flux rope with less than 1 wind of twist can erupt via the onset of the torus instability.