Solar Coronal Loop Dynamics

A special issue of Universe (ISSN 2218-1997). This special issue belongs to the section "Solar System".

Deadline for manuscript submissions: closed (1 March 2022) | Viewed by 7116

Special Issue Editors


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Guest Editor
Key Laboratory of Solar Activity, National Astronomical Observatories of Chinese Academy of Sciences, Datun Road 20A, Chaoyang District, Beijing, China
Interests: magnetic field extrapolation; solar radio bursts

E-Mail Website
Guest Editor
Division of Solar Physics, National Astronomical Observatories of Chinese Academy of Sciences, Beijing 100192, China
Interests: solar radio astronomy; solar physics; plasma astrophysics
Special Issues, Collections and Topics in MDPI journals

Special Issue Information

Dear Colleagues,

Since the era of Skylab, the discovery that a significant part of the energy emission from the solar corona is concentrated along well-defined curved paths, coronal loops, represents a major advance in our understanding of the Sun. Such magnetized plasma loops are the basic structural elements of the corona, particularly in and over solar-active regions. In fact, one may imagine that the corona is entirely composed of nested coronal loops with varying lengths, temperatures, densities, and activity levels, and should be ubiquitous in sun-like stars as well as in the Sun. The formation, oscillation, and interaction of coronal loops may mostly reflect and dominate the coronal heating processes and the details of the origin of solar eruptions, including solar flares, coronal mass ejections, eruptive filaments, and various scales of plasma jets, and even the origin and evolution of solar wind.

The dynamics of coronal loops include the magnetic field and its evolution; energy transport and release; heating, cooling and condensation; particle acceleration and emission; the evolution of waves and oscillations in the loops and the interactions between different loops; and the triggering and onset of MHD instabilities, etc. The dynamics of coronal loops may also connect with the unseen solar interior, revealing the interior structures, presenting the precursors of emerging active regions, and providing diagnostic tools through coronal loop seismology. In the past few decades, owing to the large number of observations from novel designed instruments, such as the space telescopes SOHO, TRACE, Hinode, STEREO, SDO, PSP, and SolO; many ground-based optic telescopes globally; and the ground-based radio telescopes NRH, NoRH, MUSER, and EVOSA, as well as JVLA, ALMA, LOFAR, MWA, etc., we have made great progress in the research of coronal loop dynamics with simulations and theoretical explanations.

We invite colleagues to submit their recent papers on one or more of the following topics for this Special Issue:

  1. New interesting observations of coronal loops;
  2. Magnetic field diagnostics and extrapolation;
  3. Waves and oscillations in coronal loops;
  4. Interactions between coronal loops;
  5. Heating, cooling, and condensation;
  6. Particle acceleration and radio emission in coronal loops;
  7. The triggering and onset of MHD instabilities;
  8. The evolution of the whole lives of coronal loops.

Prof. Dr. Yihua Yan
Prof. Dr. Baolin Tan
Guest Editors

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Keywords

  • Coronal loops
  • Magnetic fields
  • Oscillations
  • Heating and cooling
  • Emission
  • Evolution

Published Papers (5 papers)

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Research

11 pages, 1083 KiB  
Article
Damping Scenarios of Kink Oscillations of Solar Coronal Loops
by Valery M. Nakariakov and Naga V. Yelagandula
Universe 2023, 9(2), 95; https://doi.org/10.3390/universe9020095 - 11 Feb 2023
Cited by 2 | Viewed by 1021
Abstract
The transition from the large-amplitude rapidly-decaying regime of kink oscillations of plasma loops observed in the corona of the Sun to the low-amplitude decayless oscillations is modelled. In this study, the decayless regime is associated with the energy supply from coronal plasma flows, [...] Read more.
The transition from the large-amplitude rapidly-decaying regime of kink oscillations of plasma loops observed in the corona of the Sun to the low-amplitude decayless oscillations is modelled. In this study, the decayless regime is associated with the energy supply from coronal plasma flows, i.e., self-oscillations, or random movements of footpoints of the oscillating loop. The damping is attributed to the linear effect of resonant absorption. We demonstrate that the decay of an impulsively excited kink oscillation to the self-oscillatory stationary amplitude differs from the exponential decay. The damping time is found to depend on the oscillation amplitude to the power of a negative constant whose magnitude is less than unity. In this scenario, a better model for the damping seems to be super-exponential. In the separately considered case of the decayless oscillatory regime supported by a random driver, the oscillation amplitude experiences an exponential decay to the decayless level. Implications of this finding for magnetohydrodynamic seismology of the solar corona based on the effect of resonant absorption are discussed. Full article
(This article belongs to the Special Issue Solar Coronal Loop Dynamics)
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14 pages, 2857 KiB  
Article
Clusters of Solar Radio Spikes Modulated by Quasi-Periodic Pulsations in a Confined Flare
by Jing Huang, Chengming Tan, Xingyao Chen, Baolin Tan, Yihua Yan, Yin Zhang, Suli Ma, Zhichao Zhou, Minghui Zhang, Wei Wang and Linjie Chen
Universe 2022, 8(7), 348; https://doi.org/10.3390/universe8070348 - 24 Jun 2022
Cited by 2 | Viewed by 1341
Abstract
Spikes are typical radio bursts in solar flares, which are proposed to be the signal of energy release in the solar corona. The whole group of spikes always shows different spectral patterns in the dynamic spectrum. Here, we present a special new feature [...] Read more.
Spikes are typical radio bursts in solar flares, which are proposed to be the signal of energy release in the solar corona. The whole group of spikes always shows different spectral patterns in the dynamic spectrum. Here, we present a special new feature at 0.6–2 GHz in a confined flare. Each group of spikes is composed of many quasi-periodic sub-clusters, which are superposed on the broadband quasi-periodic pulsations (QPPs). The quasi-periodic cluster of spikes (QPSs) have very intense emissions, and each cluster includes tens of individual spikes. When the intensity of background pulsation is increased, the intensity, duration and bandwidth of the spike cluster are also enlarged. There are 21 groups of QPSs throughout the confined flare. The central frequency of the whole group shifts from 1.9 to 1.2 GHz, and the duration of each cluster shows a negative exponential decay pattern. We propose that nonthermal electron beams play a crucial role in emitting both pulsations and spikes. The tearing-mode oscillations of a confined flux rope produce periodic accelerated electron beams. These electron beams travel inside the closed magnetic structure to produce frequency drifting pulsations via plasma emission and scattered narrowband spikes by electron-cyclotron maser emission (ECME). The slow rise of flux rope makes the source region move upward, and thus, QPSs shift towards low frequency. We propose that the confined flux rope may provide the essential conditions for the formation of QPSs. Full article
(This article belongs to the Special Issue Solar Coronal Loop Dynamics)
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11 pages, 3304 KiB  
Article
One-Minute Quasi-Periodic Pulsations during an M-Class Solar Flare
by Fanpeng Shi, Dong Li and Zongjun Ning
Universe 2022, 8(2), 104; https://doi.org/10.3390/universe8020104 - 5 Feb 2022
Cited by 6 | Viewed by 1263
Abstract
We study the Quasi-Periodic Pulsations (QPPs) of an M4.4 class solar flare, which occurred in active region NOAA 11165 on 8 March 2011. With the Fast Fourier Transform (FFT) method, we decompose the flare light curve into fast- and slowly-varying components. The 100 [...] Read more.
We study the Quasi-Periodic Pulsations (QPPs) of an M4.4 class solar flare, which occurred in active region NOAA 11165 on 8 March 2011. With the Fast Fourier Transform (FFT) method, we decompose the flare light curve into fast- and slowly-varying components. The 100 s (0.01 Hz) is selected as the cutoff threshold between the fast- and slowly-varying components. One-minute QPPs are found around flare peak at soft X-ray (SXR) and Extreme Ultraviolet (EUV). Using the data from the Atmospheric Imaging Assembly (AIA) onboard the Solar Dynamics Observatory (SDO), the intermittent jets are detected and the interesting fact is that the jets also display one-minute period. The correlationship between the fast-varying components of SXR or EUV emissions and the jets suggests that the QPPs on light curves and periodic jets could come from the same origination, e.g., the periodic magnetic reconnection in this event. Full article
(This article belongs to the Special Issue Solar Coronal Loop Dynamics)
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20 pages, 5100 KiB  
Article
Multi-Wavelength Observations of a Failed Filament Eruption and Associated Hovered Coronal Mass Ejection
by Yin Zhang, Baolin Tan, Chengmin Tan, Jing Huang and Yihua Yan
Universe 2021, 7(11), 405; https://doi.org/10.3390/universe7110405 - 28 Oct 2021
Cited by 3 | Viewed by 1433
Abstract
Failed filament eruption remains mysterious on its initiation, magnetic environment, and erupting and failing mechanisms. We present multi-wavelength observations of a failed filament eruption and its associated hovered coronal mass ejection (hovered-CME) from limb observations of the Ahead of Solar Terrestrial Relations Observatory. [...] Read more.
Failed filament eruption remains mysterious on its initiation, magnetic environment, and erupting and failing mechanisms. We present multi-wavelength observations of a failed filament eruption and its associated hovered coronal mass ejection (hovered-CME) from limb observations of the Ahead of Solar Terrestrial Relations Observatory. On-disk observations from Solar Dynamics Observatory show the expansion of the anchored leg of an S-shaped filament during the pre-eruption phase. The main eruption starts as a sudden ejection of the erupted leg, which is followed by the appearance of EUV brightening in the S-shaped magnetic field. The brightening is spatio-temporal accompanied with hard X-ray emission enhancement, and cancellation of opposite magnetic polarities, which imply possible reconnection. After reaching the maximum displacement, the erupted material drains back to the Sun along the remaining anchored leg. The non-linear force free magnetic field extrapolation shows an S-shaped magnetic field, formed by two magnetic structures, with a strong enveloped magnetic field. The decay index at the possible apex of the filament is 0.8–1.2. Observations indicate that the failed filament eruption is triggered by tether cutting reconnection and is possibly confined by the upper magnetic field. The hovered-CME, resulting from the failed filament eruption and recording as a coronal mass ejection (CME), may cause the overestimation of the CME count. Full article
(This article belongs to the Special Issue Solar Coronal Loop Dynamics)
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13 pages, 1116 KiB  
Article
The Early Evolution of Solar Flaring Plasma Loops
by Baolin Tan
Universe 2021, 7(10), 378; https://doi.org/10.3390/universe7100378 - 11 Oct 2021
Cited by 2 | Viewed by 1309
Abstract
Plasma loops are the elementary structures of solar flaring active regions and dominate the whole process of flaring eruptions. Standard flare models explain evolution and eruption after magnetic reconnection around the hot cusp-structure above the top of plasma loops very well; however, the [...] Read more.
Plasma loops are the elementary structures of solar flaring active regions and dominate the whole process of flaring eruptions. Standard flare models explain evolution and eruption after magnetic reconnection around the hot cusp-structure above the top of plasma loops very well; however, the early evolution of plasma loops before the onset of magnetic reconnection is poorly understood. Considering that magnetic gradients are ubiquitous in solar plasma loops, this work applies the magnetic-gradient pumping (MGP) mechanism to study the early evolution of flaring plasma loops. The results indicate that early evolution depends on the magnetic field distribution and the geometry of the plasma loops, which dominate the balance between the accumulation and dissipation of the energy around loop tops. Driven by MGP process, both of the density and temperature as well as the plasma β value around the looptop will increase in the early phase of the plasma loop’s evolution. In fact, the solar plasma loops will have two distinct evolutionary results: low, initially dense plasma loops with relatively strong magnetic fields tend to be stable for their maximum β value, which is always smaller than the critical value β<βc, while the higher, initially diluted solar plasma loops with relatively weak magnetic fields tend to be unstable for their β values, exceeding the critical value β>βc at a time of about one hour after the formation of the solar-magnetized plasma loop. The latter may produce ballooning instability and may finally trigger the following magnetic reconnection and eruptions. These physical scenarios may provide us with a new viewpoint to understand the nature and origin of solar flares. Full article
(This article belongs to the Special Issue Solar Coronal Loop Dynamics)
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