KU Leuven Centre for mathematical Plasma-Astrophysics Seminar
Title: The role of turbulence in solar prominences using numerical simulations
Speaker: Madhurjya Changmai from CmPA
Abstract
Many solar prominences show intricate, turbulent internal dynamics. Since prominences represent large-scale condensations suspended against gravity in the solar atmosphere, the Rayleigh-Taylor (RT) instability is one of the important fundamental processes leading to turbulence seen in observations. We study this turbulence in quiescent solar prominences. These are long-lived, cool, and dense structures in the solar corona that demonstrate dynamics at a multitude of spatial and temporal scales. Observations show prominent vertical flows while the mean magnetic field is predominantly horizontal. We study prominence turbulence using high-resolution, direct numerical simulations.
We perform 2.5D ideal magnetohydrodynamic (MHD) simulations with the open-source {\tt MPI-AMRVAC} code and follow the far nonlinear evolution of an RT instability that starts at the prominence-corona interface. Our simulation achieves a resolution down to $\sim 23$ km on a domain of size 30 Mm $\times$ 30 Mm. We follow the instability transitioning from a multi-mode linear perturbation to its nonlinear fully turbulent state. We follow up to the turbulent state for $\sim 25$ minutes real time, and produce statistical analysis on extracted data with a cadence of $\sim 0.858$ seconds.
We produce the statistical analysis of the nonlinear fully turbulent state. We find coherent structure formation predominantly in the vertical velocity component, clearly demonstrating anisotropic turbulence within our prominence. Furthermore, we find power-law scalings in the inertial range for the velocity, magnetic, and temperature fields. The presence of intermittency is evident from the probability density functions of the field fluctuations, which depart from Gaussianity; larger scales are more Gaussian, whereas the smaller scales in the prominence are highly intermittent. This aspect is then quantitatively analyzed using the higher-order structure functions, which show multifractality and different scale characteristics and behavior between the longitudinal and transverse directions. Thus, overall the statistics remain consistent with the observational work done in prominence turbulence, and we can relate the RT instability to be a key factor of turbulence found in the quiescent prominence.
The seminars are in hybrid mode, you can follow in person in room 200B 02.16 or online at the (permanent) link:
https://eu.bbcollab.com/guest/7406a5ec00dc4ec6948200f9c769d454
Date and time: Thursday, March 10, 2022 - 14:00 to 15:00
