Research
Viscosity in the Intracluster Medium
The plasma that permeates the space in between galaxies in galaxy clusters - known as the intracluster medium - is frequently stirred up by mergers with other clusters and outflows from the nuclei of galaxies contained within. These processes are understood to drive turbulence, which facilitates the movement of energy between flows at different scales. However this plasma is also expected to be very viscous, which implies that the swirling turbulent flows cannot cascade to much smaller scales before they are dissipated. In this project, we are investigating how the plasma self-organizes, through a process known as "magneto-immutability", to avoid the motions that are most susceptible to viscosity. As a result, we anticipate that these fluctuations can span from hundreds of kiloparsecs, all the way down to the scale of planets!
Manuscript in preparation
Magneto-immutability
Collisionless plasmas, especially those where the ratio of thermal to magnetic pressure is high, are subject to a number of effects that demand knowledge of what the individual particles are doing. As a result when we attempt to describe their evolution, we are often forced to use kinetic models that account for varying distributions of particle energies, rather than fluid models, which limit us to a single choice for that distribution. However, there are certain conditions in turbulence that can lead to the plasma organizing in a way that is surprisingly well described by fluid models. This process is called magneto-immutability, and it may be relevant to numerous astrophysical environments, making it easier to describe their dynamics.
Collisionless waves
Wave dynamics is one of the most fundamental aspects of how a plasma evolves. Much progress has been made in turbulence by understanding the kinds of waves present in a plasma and how they interact to move energy between scales. In many astrophysical plasmas, these waves are affected by individual particle effects such as damping from resonant wave-particle interactions or small-scale instabilities. We studied the importance of these effects in compressive waves, to better understand their role in turbulent plasmas like those seen around black holes or in galaxy clusters.
Guide field distributions of the plasmoid instability
Magnetic reconnection is a phenomenon by which significantly strained magnetic field lines suddenly release large amounts of energy into the surrounding plasma, breaking and snapping together in such a way that they reach a much more relaxed state. Various models have aimed to explain how this reconnection can happen in a sufficiently rapid manner that explains observations of energy release in events like coronal mass ejections. One such model focuses on a process called the plasmoid instability, which speeds up this reconnection by creating numerous magnetic islands, each of which drive reconnection at many different sites (sort of like how a parallel computing task can be completed faster than a serial one). We investigated the changes that would occur to the long-time limit behavior of this instability when another component of the magnetic field is added to the process, one which doesn't partake in the reconnection itself (known as a guide field).