arXiv subjects

V. Jerčić

Publications and source records attributed to V. Jerčić.

5 recordsLinked to original sources

arXiv2026

From simulations to observations of cool plasma: What we can learn from synthetic spectra

Cool plasma of coronal rain or prominences and filaments is ubiquitous in the solar corona. We explored the synthetic spectra of MgII h&k lines in detail and analyse how well a non-adiabatic magnetohydrodynamic (MHD) simulation of condensations in the corona matches observations when comparing the synthetic with the observed spectra. We applied, a Python implemented, non-local thermodynamic equilibrium (non-LTE) radiative-transfer framework, Promweaver to create synthetic spectra from a 2.5D MHD simulation created with MPI-AMRVAC. The simulation shows a dynamic system of numerous cold, dense thread-like structures that we compare to observations of the $\textit{Interface Region Imaging Spectrograph}$ (IRIS), with a focus on flare-driven coronal rain. We give a detailed description of the simulation from the aspect of the synthetic spectra. We show how and why the particular spectra form. A single thread already demonstrates great complexity. We further used the quartile analysis to systematically explore the evolution of observables in the observed and the synthetic spectra. This gives an overview of how the parameters change in time and that the changes seen in the simulation fit with the changes seen in observations. The results show that the simulation, in some aspects, matches particularly well to the observations of flare-driven coronal rain. Furthermore, we explored relations of parameters of the simulation and the observables. We find significant correlation between intensity and density, but not with temperature (in the studied temperature range of 5 to 20 kK). As a result, there is also a correlation of intensity and pressure. This relation allows us to further relate intensity and the vertical component of the Lorentz force. This brings us a step closer to a better understanding of the connection between the observed spectra and the atmosphere from which it originates.

astro-ph.SR↗

arXiv2025

Forming prominences accounting for partial ionisation effects

One of the most striking structures in the solar atmosphere are prominences, predominantly coronal structures, with thermodynamic conditions that vary from chromospheric internally to the corona that surrounds them. These structures play an important role in the energy transfer between all layers of the atmosphere. Although mostly studied as a fully ionised plasma, prominences are, in fact, composed of partially ionised plasma. We do not yet fully understand the extent to which the two-fluid plasma-neutral properties play a role in the evolution of these coronal structures. In this work, we explore for the very first time how prominence formation and growth in a coronal loop evolves in a two-fluid setting. We used MPI-AMRVAC to study the evaporation-condensation process, where we consider radiative cooling, thermal conduction, and localised heating in a coronal loop in a fully stratified atmosphere. We report on the differences the two-fluid plasma brings into the prominence evolution, and more specifically in the period after the dynamic formation process finishes. Furthermore, we highlight the role it plays during the linear and the non-linear phases of the evolution. We find pronounced two-fluid effects in shocks that appear with the first complete condensation and confirm decoupling effects in the PCTR on the order of 100$\,$m$\,$s$^{-1}$, consistent with observations.

astro-ph.SR↗

arXiv2024

Prominence and coronal rain formation by steady versus stochastic heating and how we can relate it to observations

Prominences and coronal rain are two forms of coronal condensations for which we still lack satisfactory details on the formation pathways and conditions under which the two come to exist. We compared prominences that formed via a steady versus stochastic type of heating. We performed 2.5D simulations using the open-source MPI-AMRVAC code. To further extend the work and allow for future direct comparison with observations, we used Lightweaver to form spectra of the filament view of our steady case prominence. With that, we analysed a reconnection event that shares certain characteristics with nanojets. We show how different forms of localised heating that induce thermal instability result in prominences with different properties. The steady form of heating results in prominence with a clear vertical structure stretching across the magnetic field lines. On the other hand, stochastic heating produces many threads that predominantly have a horizontal motion along the field lines. In the steady heating case, the prominence is relatively static; however, there is evidence of reconnection happening almost the entire time the prominence is present. In the case of stochastic heating, the threads are highly dynamic, with them also exhibiting a form of transverse oscillation (strongly resembling the decayless type). The fact that the threads in the stochastic heating case are constantly moving along the field lines suppresses any conditions for reconnection. It, therefore, appears that, to first order, the choice of heating prescription defines whether the prominence-internal dynamics are oriented vertically or horizontally. We closely inspected a sample reconnection event and computed the synthetic optically thick radiation using the open-source Lightweaver radiative transfer framework.

astro-ph.SR↗

arXiv2022

Dynamic formation of multi-threaded prominences in arcade configurations

With this study, we aim to understand the nature of prominences, governed by their formation process. We use a state-of-the-art threaded prominence model within a dipped magnetic arcade. The non-ideal magnetohydrodynamic (MHD) equations are solved using the open-source MPI-AMRVAC MHD toolkit. Unlike many previous 1D models, we study the full 2D dynamics in a fixed-shaped arcade. This allows for sideways field deformations and cross-field thermodynamic coupling. To achieve a realistic setup we consider field-aligned thermal conduction, radiative cooling and heating, wherein the latter combines a steady background and a localized stochastic component. The stochastic component simulates energy pulses localized in time and space at the footpoints of the magnetic arcade. We vary the height and amplitude of the localized heating and observe how it influences the prominence, its threads, and its overall dynamics. We show the importance of random localized 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 localized 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 quantify how these rates match with values from observations. We detail how stochastic sources determine counterstreaming flows and oscillations of prominence threads.

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arXiv2021

Multi-threaded prominence oscillations triggered by a coronal shock wave

In this work, we study the causal relations between a localised energy release and a remote prominence oscillation, where the prominence has a realistic thread-like structure. We used an open source magnetohydrodynamic (MHD) code known as MPI-AMRVAC to create a multithreaded prominence body. We introduced an additional energy source from which a shock wave originates, thereby inducing prominence oscillation. We studied two cases with different source amplitudes to analyze its effect on the oscillations. Our results show that the frequently used pendulum model does not suffice to fully estimate the period of the prominence oscillation, in addition to showing that the influence of the source and the thread-like prominence structure needs to be taken into account. Repeated reflections and transmissions of the initial shock wave occur at the specific locations of multiple high-temperature and high-density gradients in the domain. This includes the left and right transition region (TR) located at the footpoints of the magnetic arcade, as well as the various transition regions between the prominence and the corona (PCTR). This results in numerous interferences of compressional waves. They contribute to the restoring forces of the oscillation, causing the period to deviate from the expected pendulum model, in addition to leading to differences in attributed damping or even growth in amplitude between the various threads. Along with the global longitudinal motion that result from the shock impact, small-scale transverse oscillations are also evident. Multiple high-frequency oscillations represent the propagation of magnetoacoustic waves. The damping we see is linked to the conversion of energy and its exchange with the surrounding corona. Our simulations demonstrate the exchange of energy between different threads and their different modes of oscillation.

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