AGS-PRF: Instability of Sheetlike Structures in Alfvenic Turbulence

Mallet Alfred, Durham NH

Investigators

Abstract

The solar wind provides the background of the space environment in which our planet exists. It is analogous, in some ways, to the jet streams in Earth's atmosphere, with flows that vary in speed and direction. This solar wind is the background on which space weather events occur. To correctly and accurately model space weather events and their impact on Earth, it is crucial to appropriately model the solar wind. The solar wind is turbulent in nature and this project aims to understand the intermittency of turbulence and certain instabilities that are expected to arise in the turbulent space plasmas such as those at the magnetopause and as a result of solar flares. Turbulent plasma is ubiquitous in astrophysics, so understanding plasma turbulence is important more generally, and not just in the setting of the solar wind - for example, in accretion disks, galaxy clusters, or in fusion devices on earth. This work is a unique combination of theoretical work to predict when the instabilities set in and numerical experiments to verify the prediction. This work is very timely and will form a basis for predictions for NASAs upcoming mission Solar Probe Plus. The PI of this Postdoctoral Research Fellowship plans to incorporate student participation through a research class at the University of New Hampshire as well as through the organization of a session at the Solar and Heliospheric INterplanetary Environment (SHINE) meeting. Typically, 25% of the attendees of this meeting are students. The project seeks to investigate the impacts of Kelvin-Helmoltz and plasmoid instabilities on Alfevnic turbulence. These instabilities become important once coherent structures in the turbulent plasma, the Elsasser sheets, reach a critical aspect ratio. The growth rates of these instabilities will be predicted and then confirmed with Reduced Magnetohydrodynamics simulations. The updated turbulence model will predict the local anisotropy of the turbulence, how the outer scale properties of the turbulence in the solar wind affect the statistical properties at small scales, and the type of intermittent structures that are produced. The dissipation in plasmas is observed to be closely linked to intermittent structures. This is an important current topic of interest to the community. The intermittent structures formed in the Alfvenic turbulence investigated here are strongly affected by the presence of the instabilities, and so this project is important for the understanding of the dissipation of turbulent energy.