Magnetohydrodynamic turbulence is central to laboratory and astrophysical plasmas, and is invoked for interpreting many observed scalings. Verifying predicted scaling law behaviour requires extreme-resolution direct numerical simulations (DNS), with needed computing resources excluding systematic parameter surveys. We here present an analytic generator of realistically looking turbulent magnetic fields, that computes 3D O(1000 3 ) solenoidal vector fields in minutes to hours on desktops. Our model is inspired by recent developments in 3D incompressible fluid turbulence theory, where a Gaussian white noise vector subjected to a non-linear transformation results in an intermittent, multifractal random field. Our B × C model has only few parameters that have clear geometric interpretations. We directly compare a (costly) DNS with a swiftly B × C-generated realization, in terms of its (i) characteristic sheet-like structures of current density, (ii) volume-filling aspects across current intensity, (iii) power-spectral behaviour, (iv) probability distribution functions of increments for magnetic field and current density, structure functions, spectra of exponents, and (v) partial variance of increments. The model even allows to mimic time-evolving magnetic and current density distributions and can be used for synthetic observations on 3D turbulent data cubes.
Aims. Solar prominences represent large-scale condensations suspended against gravity within the solar atmosphere. The Rayleigh-Taylor (RT) instability is proposed to be one of the important fundamental processes leading to the generation of dynamics at many spatial and temporal scales within these long-lived, cool, and dense structures amongst the solar corona. We aim to study such turbulent processes using high-resolution, direct numerical simulations of solar prominences. Methods. We run 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 follow the instability transitioning from a multi-mode linear perturbation to its nonlinear, fully turbulent state. Over the succeeding ∼ 25 minute period, we perform a statistical analysis of the prominence at a cadence of ∼ 0.858 s. Results. We find the dominant guiding B z component induces coherent structure formation predominantly in the vertical velocity V y component, consistent with observations, demonstrating an anisotropic turbulence state within our prominence. We find powerlaw 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 multifractality, in addition to different scale characteristics and behavior between the longitudinal and transverse directions. Thus, the statistics remain consistent with the conclusions from previous observational studies, enabling us to directly relate the RT instability to the turbulent characteristics found within quiescent prominence.
<p>The purpose of our study is to deepen our understanding on the turbulence that arises from Rayleigh Taylor Instabilities in quiescent solar prominences. Quiescent prominences in the solar corona are cool and dense condensates that show internal dynamics over a wide range of spatial and temporal scales. These dynamics are dominated by vertical flows in the prominence body where the mean magnetic field is predominantly in the horizontal direction and the magnetic pressure suspends the dense prominence material. We perform numerical simulations using&#160; MPI-AMRVAC (http://amrvac.org) to study the Rayleigh Taylor Instabilitiy at the prominence-corona transition region using the Ideal-magentohydrodyamics approach. High resolution simulations achieve a resolution of &#8764;23 km for &#8764;21 min transitioning from a multi-mode perturbation instability to the non-linear regime and finally a fully turbulent prominence. We use statistical methods to quantify the rich dynamics in quiescent prominence as being indicative of turbulence.</p>
<p>The internal dynamics of solar prominences have been observed for many decades to be highly complex, many of which also indicate the possibility of turbulence. Prominences represent large-scale, dense condensations suspended against gravity at great heights within the solar atmosphere. It is therefore of no surprise that the fundamental process of the Rayleigh-Taylor (RT) instability has been suggested as the potential mechanism for driving the dynamics and turbulence remarked upon within observations. We use the open-source <strong>MPI-AMRVAC</strong> code to construct an extremely high-resolution, 2.5D fully-resistive magnetohydrodynamic model, and employ it to explore the turbulent nature of RT-induced magnetic reconnection processes within solar prominences. The intermittent events of heating and energy dissipation are caused by magnetic reconnection. Furthermore, the strength of the mean magnetic field directed into the 2D plane, and its alignment with the plane itself, creates a system with varying turbulent behaviour. Based on low plasma beta (magnetic pressure dominant) evolution near the chromosphere and a higher value (plasma pressure dominant) evolution within the corona, the stratified numerical model generates different fluctuation statistics. Hence, we find the turbulent dynamics and prominence reconnection events to differ distinctly from those elsewhere within the solar corona.</p><div></div>
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
hi@scite.ai
10624 S. Eastern Ave., Ste. A-614
Henderson, NV 89052, USA
Copyright © 2024 scite LLC. All rights reserved.
Made with 💙 for researchers
Part of the Research Solutions Family.