Maile Marriot, UT-Austin

"MHD Modeling of Switchbacks in 3D"

Abstract: How the solar corona is heated to a temperature of a million degrees, and how the solar wind is accelerated are fundamental questions in space physics. Waves and turbulence are likely mechanisms, but how turbulence is generated at the sun and then evolves as it propagates out in interplanetary space is not yet fully understood. Interestingly, recent observations from the NASA mission Parker Solar Probe have revealed that the solar wind close to the sun is with waves of such large amplitude that the magnetic field reverses and points sunward. These highly kinked waves are known as switchbacks. The origin(s) and evolution of switchbacks remain important open questions, and switchbacks may be key to understanding the origins of the solar wind.

In this work we focus on the stability of a switchback to determine how it evolves and what affects its lifetime in the solar wind. Starting from an analytical model of a switchback in the form of a wave packet, we investigated its evolution via three-dimensional Magnetohydrodynamic simulations. We showed that the initial wave packet is unstable to the parametric decay instability, that develops in the plane of the wave packet. A second, transverse unstable mode also grows when noise is added along the out-of-plane direction. We find that the growth of the transverse mode greatly increases the decay rate of the switchback. We conclude by discussing the implications of these results for different models of switchback's generation mechanisms and by outlining our future work.