Dynamic formation of multi-threaded prominences in arcade configurations

Abstract

Context. High in the Sun’s atmosphere, prominences are plasma structures two orders of magnitude colder and denser than the surrounding corona. They often erupt, forming the core of violent and Earth-threatening coronal mass ejections. It is still unclear how these giant structures form and what causes their internal fine structure and dynamics. Moreover, it is not evident how mass and energy get exchanged with the lower layers of the Sun’s atmosphere. Aims. We aim to understand the nature of prominences, governed by their formation process. We attempt to answer how exactly evaporation-condensation proceeds, and what the mass and energy exchange is like between the prominence and the regions where they are rooted, most notably the chromosphere and the transition region. Methods. We used a state-of-the-art threaded prominence model within a dipped magnetic arcade. We solved the non-ideal magnetohydrodynamic (MHD) equations using the open source MPI-AMRVAC MHD toolkit. Unlike many previous 1D models where a magnetic field was assumed ‘infinitely strong’, we studied the full 2D dynamics in a fixed-shaped arcade. This allowed for sideways field deformations and a cross-field thermodynamic coupling. To achieve a realistic setup, we considered field-aligned thermal conduction, radiative cooling, and heating, wherein the latter combines a steady background and a localised stochastic component. The stochastic component simulates energy pulses localised in time and space at the footpoints of the magnetic arcade. We varied the height and the amplitude of the localised heating and observed how it influences the prominence, its threads, and its overall dynamics. Results. We show with this work the importance of the random localised heating in the evolution of prominences and their threaded structure. Random heating strongly influences the morphology of the prominence threaded structure, the area, the mass the threads reach, their minimum temperature, and their average density. More importantly, the strength of the localised heating plays a role in maintaining the balance between condensation and draining, affecting the general prominence stability. Stronger sources form condensations faster and result in larger and more massive prominences. We show how the condensation rates scale with the amplitude of the heating inputs and we quantify how these rates match with values from observations. We detail how stochastic sources determine counter-streaming flows and the oscillations of prominence threads.

Modeling of Condensations in Coronal Loops Produced by Impulsive Heating with Variable Frequencies and Locations

“…Mendoza-Briceño et al (2005), for instance, state that for their simulations with randomized heating impulses, distributions of pulses closer to loop footpoints produce more rapid temperature depressions than do distributions extending further up the loop legs. Jerčić & Keppens (2023) performed a study more focused on the parameters of the randomized nanoflare distribution, but applied to a two-dimensional prominence magnetic configuration rather than a one-dimensional loop configuration as we have here. They focused on variations in height and intensity of the nanoflares.…”

Radiative loss and ion-neutral collisional effects in astrophysical plasmas

“…At the same time, many recent works [e.g. [2][3][4][5][6][7][8][9][10][11][12][13][14][15][16] support the original claim by Parker [17] that thermal instability is a fundamental process that can trigger in situ condensations, like prominences and coronal rain in the solar atmosphere, but also denser clumps in galactic winds, or in other astrophysical contexts [18][19][20]. For this reason, the linear mode which grows exponentially due to the energy loss is usually called 'thermal' or 'condensation' mode (see [21]).…”

Mass Cycle and Dynamics of a Virtual Quiescent Prominence

“…These siphoning flows form the basis of all numerical models that adopt the evaporation-condensation mechanism, which gradually evaporates upper chromospheric matter into the corona (Poland & Mariska 1986). In practice, a localized heating term in the governing magnetohydrodynamic (MHD) energy equation is added to evaporate the plasma from denser low-lying regions, and this elevated matter subsequently condenses at the top of the (dipped) magnetic arcades in one dimension (1D; Xia et al 2011;Zhou et al 2014) and two dimensions (2D; Xia et al 2012;Jercić & Keppens 2023;Zhou et al 2023). The evaporationcondensation model has also been implemented for threedimensional (3D) flux-rope models (Xia & Keppens 2016).…”