Simulating Rayleigh-Taylor induced magnetohydrodynamic turbulence in prominences^⋆

Centre for mathematical Plasma-Astrophysics, Celestijnenlaan 200B, 3001 Leuven, KU Leuven, Belgium
e-mail: madhurjya.changmai@kuleuven.be

Received: 3 January 2022
Accepted: 7 February 2023

Abstract

Aims. Solar prominences are large-scale condensations suspended against gravity within the solar atmosphere. The Rayleigh-Taylor (RT) instability is proposed to be one of the fundamental processes that lead to the generation of dynamics at many spatial and temporal scales within these long-lived, cool, and dense structures, which are located in the solar corona. We aim to study such turbulent processes using high-resolution, direct numerical simulations of solar prominences.

Methods. We ran 2.5D ideal magnetohydrodynamic (MHD) simulations with the open-source MPI-AMRVAC code far into the nonlinear evolution of an RT instability perturbed at the prominence-corona interface. Our simulation achieves a resolution down to ∼23 km on a 2D (x, y) domain of size 30 Mm × 30 Mm. We followed the instability transitioning from a multimode linear perturbation to its nonlinear, fully turbulent state. Over the succeeding ∼25 min period, we performed a statistical analysis of the prominence at a cadence of ∼0.858 s.

Results. We find that the dominant guiding component, B_z, induces coherent structure formation predominantly in the vertical velocity component, V_y, consistent with observations, indicating an anisotropic turbulence state within our prominence. 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 as we consider smaller and smaller scales. In exact agreement, the higher-order structure functions quantify the multi-fractality, as do different scale characteristics and the behavior between the longitudinal and transverse directions. Thus, the statistics remain consistent with conclusions from previous observational studies, enabling us to directly relate the RT instability to the turbulent characteristics found within quiescent prominences.