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Abstract
High velocity clouds (HVCs) are clouds of gas moving at high relative speeds through galaxies, including our own. They play an important role in the evolution of the galaxies with which they interact. This work explores several important topics related to HVCs. We determine how mixing between an HVC and the ambient environment affects the HVC's distribution of ionization states. We then use those results to develop a new prescription for estimating the mass of HVCs from observables. We also perform hydrodynamic and magnetohydrodynamic simulations of HVCs colliding with the Galactic disk, to analyze the survivability of such a collision for the HVC and the effects of the collision on the disk. The HVCs in these simulations are modeled by a dark matter minihalo, with most of the clouds also including a baryonic component. We also develop a new algorithm for calculating the radiative losses due to the actual populations of ions present in the gas, rather than using the typical approximation that the ions are in collisional ionization equilibrium (CIE). We test our algorithm against two CIE radiative cooling algorithms, one developed here which uses the same elements as our NEI algorithm, and the other the existing FLASH radiative cooling module which includes contributions from a larger number of elements. Finally, we apply our new radiative cooling algorithm to simulations of HVCs.