Cosmic Ray and Magnetically Driven Bubbles in Galaxies

The Parker instability impacts the evolution of galaxies and gas clouds. Driven by buoyancy, it describes a feedback loop for warping magnetic fields. As the Parker instability evolves, it can cause magnetic field lines to cross and reconnect, accelerating gas bubbles into or away from the disk. How these bubbles form and evolve is significant to understanding how magnetic reconnection can affect the larger galactic system.

This study investigates the behavior of hot, dense gas bubbles accelerated by magnetic reconnection and heated by cosmic rays (CRs). The results shed light on the effects of reconnection and the effectiveness of the code that simulates it. Similar hot bubbles have been observed in the intergalactic medium.

I examine the evolution of these bubbles through a combination of numerical simulations in the magnetohydrodynamic code FLASH and Athena++ using data processing methods in Python. I find evidence confirming the idea that these bubbles are formed by reconnection. I find bubble velocities over time to identify the relevant forces accelerating the bubble against gravity.

The FLASH code does not rigorously model magnetic reconnection, but it is possible to learn about the bubble’s behavior after the reconnection event. Findings will inform future development of magnetohydrodynamic simulations and offer nuance to observed reconnection events. I am working to run the simulations with an improved CR package and resolution in Athena++.

Acknowledgements: This research is generously supported by NSF Grant AST 2007323, the L&S STEM Summer of Excellence in Research (LASER), and the Sophomore Research Scholarship at UW-Madison.