scholarly journals Observation and simulation of a filament eruption associated with the contraction of the overlying coronal loops and the filament rotation

2013 ◽  
Vol 8 (S300) ◽  
pp. 504-506
Author(s):  
X. L. Yan ◽  
Z. K. Xue ◽  
Z. X. Mei
Keyword(s):  
Coronal Loop ◽  
Coronal Loops ◽  
Solar Dynamics Observatory ◽  
Filament Eruption ◽  
Solar Dynamics ◽  
Rotation Motion

AbstractBy using the data of Solar Dynamics Observatory (SDO), we present a case study of the contraction of the overlying coronal loop and the rotation motion of a sigmoid filament on 2012 May 22. At the beginning of the filament eruption, the overlying coronal loop experienced a significant contraction. In the following, the filament started to rotate counterclockwise. We also carried the simulation to investigate the process of the filament eruption.

scholarly journals Signatures of red-shifted footpoints in the quiescent coronal loop system

2019 ◽  
Author(s):  
Yamini K. Rao ◽  
Abhishek K. Srivastava ◽  
Pradeep Kayshap ◽  
Bhola N. Dwivedi
Keyword(s):  
Spectral Data ◽  
Coronal Loop ◽  
Doppler Velocity ◽  
Coronal Loops ◽  
Solar Dynamics Observatory ◽  
Heating Mechanism ◽  
Multi Wavelength ◽  
Solar Dynamics ◽  
Impulsive Heating ◽  
Imaging Spectrograph

Abstract. We observed quiescent coronal loops using multi-wavelength observations from the Atmospheric Imaging Assembly (AIA) onboard the Solar Dynamics Observatory (SDO) on 2016 April 13. The flows at the footpoints of such loop systems are studied using spectral data from Interface Region Imaging Spectrograph (IRIS). The Doppler velocity distributions at the footpoints lying in the moss region show the negligible or small flows at Ni I, Mg II k3 and C II line corresponding to upper photospheric and chromospheric emissions. Significant red-shifts (downflows) ranging from (1 to 7) km s−1 are observed at Si IV (1393.78 Å; log(T/K) = 4.8) which is found to be consistent with the existing results regarding dynamical loop systems and moss regions. Such downflows agree well with the impulsive heating mechanism reported earlier.

scholarly journals Signatures of red-shifted foot points in the quiescent coronal loop system

2019 ◽  
Vol 37 (4) ◽  
pp. 765-773
Author(s):  
Yamini K. Rao ◽  
Abhishek K. Srivastava ◽  
Pradeep Kayshap ◽  
Bhola N. Dwivedi
Keyword(s):  
Spectral Data ◽  
Coronal Loop ◽  
Doppler Velocity ◽  
Coronal Loops ◽  
Solar Dynamics Observatory ◽  
Heating Mechanism ◽  
Multi Wavelength ◽  
Solar Dynamics ◽  
Impulsive Heating ◽  
Imaging Spectrograph

Abstract. We observed quiescent coronal loops using multi-wavelength observations from the Atmospheric Imaging Assembly (AIA) aboard the Solar Dynamics Observatory (SDO) on 13 April 2016. The flows at the foot points of such loop systems are studied using spectral data from the Interface Region Imaging Spectrograph (IRIS). The Doppler velocity distributions at the foot points lying in the moss region show the negligible or small flows at the Ni I, Mg II k3, and C II line corresponding to upper photospheric and chromospheric emissions. Significant red shifts (downflows) ranging from 1 to 7 km s−1 are observed at Si IV (1393.78 Å; log⁡(T/K)=4.8), which is found to be consistent with the existing results regarding dynamical loop systems and moss regions. Such downflows agree well with the impulsive heating mechanism reported earlier.

scholarly journals Multi-Stranded Coronal Loops: Quantifying Strand Number and Heating Frequency from Simulated Solar Dynamics Observatory (SDO) Atmospheric Imaging Assembly (AIA) Observations

Solar Physics ◽  
2021 ◽  
Vol 296 (6) ◽  
Author(s):  
Thomas Williams ◽  
Robert W. Walsh ◽  
Stephane Regnier ◽  
Craig D. Johnston
Keyword(s):  
Energy Content ◽  
Time Lag ◽  
Low Frequency ◽  
Building Blocks ◽  
Coronal Loops ◽  
Loop Model ◽  
Solar Dynamics Observatory ◽  
Heat Deposition ◽  
Total Energy Content ◽  
Solar Dynamics

AbstractCoronal loops form the basic building blocks of the magnetically closed solar corona yet much is still to be determined concerning their possible fine-scale structuring and the rate of heat deposition within them. Using an improved multi-stranded loop model to better approximate the numerically challenging transition region, this article examines synthetic NASA Solar Dynamics Observatory’s (SDO) Atmospheric Imaging Assembly (AIA) emission simulated in response to a series of prescribed spatially and temporally random, impulsive and localised heating events across numerous sub-loop elements with a strong weighting towards the base of the structure: the nanoflare heating scenario. The total number of strands and nanoflare repetition times is varied systematically in such a way that the total energy content remains approximately constant across all the cases analysed. Repeated time-lag detection during an emission time series provides a good approximation for the nanoflare repetition time for low-frequency heating. Furthermore, using a combination of AIA 171/193 and 193/211 channel ratios in combination with spectroscopic determination of the standard deviation of the loop-apex temperature over several hours alongside simulations from the outlined multi-stranded loop model, it is demonstrated that both the imposed heating rate and number of strands can be realised.

INSIGHTS INTO FILAMENT ERUPTION ONSET FROM SOLAR DYNAMICS OBSERVATORY OBSERVATIONS

2011 ◽  
Vol 731 (1) ◽  
pp. L3 ◽  
Author(s):  
Alphonse C. Sterling ◽  
Ronald L. Moore ◽  
Samuel L. Freeland
Keyword(s):  
Solar Dynamics Observatory ◽  
Filament Eruption ◽  
Solar Dynamics

scholarly journals Evolution of downflows in the transition region above a sunspot over short time-scales

2020 ◽  
Vol 640 ◽  
pp. A120
Author(s):  
C. J. Nelson ◽  
S. Krishna Prasad ◽  
M. Mathioudakis
Keyword(s):  
Transition Region ◽  
Time Scales ◽  
Spectral Lines ◽  
Formation Mechanisms ◽  
Coronal Loops ◽  
Imaging Data ◽  
Solar Dynamics Observatory ◽  
Solar Dynamics ◽  
Short Time ◽  
Imaging Spectrograph

Context. Downflows with potentially super-sonic velocities have been reported to occur in the transition region above many sunspots; however, how these signatures evolve over short time-scales in both spatial and spectral terms is still unknown and requires further research. Aims. In this article, we investigate the evolution of downflows detected within spectral lines sampling the transition region on time-scales of the order of minutes and we search for clues as to the formation mechanisms of these features in co-temporal imaging data. Methods. For the purposes of this article, we used high-resolution spectral and imaging data sampled by the Interface Region Imaging Spectrograph on the 20 and 21 May 2015 to identify and analyse downflows. Additionally, photospheric and coronal imaging data from the Hinode and Solar Dynamics Observatory satellites were studied to provide context about the wider solar atmosphere. Results. Four downflows were identified and analysed through time. The potential super-sonic components of these downflows had widths of around 2″ and were observed to evolve over time-scales of the order of minutes. The measured apparent downflow velocities were structured both in time and space, with the highest apparent velocities occurring above a bright region detected in Si IV 1400 Å images. Downflows with apparent velocities below the super-sonic threshold that was assumed here were observed to extend a few arcseconds away from the foot-points, suggesting that the potential super-sonic components are linked to larger-scale flows. The electron density and mass flux for these events were found to be within the ranges of 109.6–1010.2 cm−3 and 10−6.81–10−7.48 g cm−2 s−1, respectively. Finally, each downflow formed at the foot-point of thin “fingers”, extending out around 3–5″ in Si IV 1400 Å data with smaller widths (< 1″) than the super-sonic downflow components. Conclusions. Downflows can appear, disappear, and recur within time-scales of less than one hour in sunspots. As the potential super-sonic downflow signatures were detected at the foot-points of both extended fingers in Si IV 1400 SJI data and sub-sonic downflows in Si IV 1394 Å spectra, it is likely that these events are linked to larger-scale flows within structures such as coronal loops.

scholarly journals Nature of the energy source powering solar coronal loops driven by nanoflares

2018 ◽  
Vol 615 ◽  
pp. L9 ◽  
Author(s):  
L. P. Chitta ◽  
H. Peter ◽  
S. K. Solanki
Keyword(s):  
Magnetic Field ◽  
Energy Source ◽  
Extreme Ultraviolet ◽  
Magnetic Energy ◽  
Plasma Heating ◽  
Active Regions ◽  
Coronal Loops ◽  
Solar Dynamics Observatory ◽  
Mixed Polarity ◽  
Solar Dynamics

Context. Magnetic energy is required to heat the corona, the outer atmosphere of the Sun, to millions of degrees. Aims. We study the nature of the magnetic energy source that is probably responsible for the brightening of coronal loops driven by nanoflares in the cores of solar active regions. Methods. We consider observations of two active regions (ARs), 11890 and 12234, in which nanoflares have been detected. To this end, we use ultraviolet (UV) and extreme ultraviolet (EUV) images from the Atmospheric Imaging Assembly (AIA) onboard the Solar Dynamics Observatory (SDO) for coronal loop diagnostics. These images are combined with the co-temporal line-of-sight magnetic field maps from the Helioseismic and Magnetic Imager (HMI) onboard SDO to investigate the connection between coronal loops and their magnetic roots in the photosphere. Results. The core of these ARs exhibit loop brightening in multiple EUV channels of AIA, particularly in its 9.4 nm filter. The HMI magnetic field maps reveal the presence of a complex mixed polarity magnetic field distribution at the base of these loops. We detect the cancellation of photospheric magnetic flux at these locations at a rate of about 1015 Mx s−1. The associated compact coronal brightenings directly above the cancelling magnetic features are indicative of plasma heating due to chromospheric magnetic reconnection. Conclusions. We suggest that the complex magnetic topology and the evolution of magnetic field, such as flux cancellation in the photosphere and the resulting chromospheric reconnection, can play an important role in energizing active region coronal loops driven by nanoflares. Our estimate of magnetic energy release during flux cancellation in the quiet Sun suggests that chromospheric reconnection can also power the quiet corona.

Automatic detection and extraction algorithm of coronal loops based on match filter and oriented directivity

2019 ◽  
Vol 490 (4) ◽  
pp. 5567-5584
Author(s):  
Song Zhiming ◽  
Yan Xiaoli ◽  
Qu Zhongquan ◽  
Li Hong-Bo
Keyword(s):  
Coronal Loops ◽  
Solar Dynamics Observatory ◽  
Pass Filter ◽  
Match Filter ◽  
Unsharp Mask ◽  
Global Threshold ◽  
Extraction Algorithm ◽  
Local Direction ◽  
Solar Dynamics ◽  
High Pass

ABSTRACT In this paper, an efficient algorithm is developed to automatically detect and extract coronal loops. First of all, in the algorithm, three characteristics associated with coronal loops are used to construct a match filter able to enhance the loops. Secondly, the method combining a high-pass filter (unsharp-mask enhancement) with a global threshold is used to further enhance and segment the loops. Thirdly, to extract every individual coronal loop and obtain their parameters (the 2D projected space coordinates and lengths) from the segmented loops, a clustering method of the pixels with approximate local direction and connected domain is further used. Fourthly, to evaluate the performance of the developed algorithm, images observed by the Transition Region and Coronal Explorer (TRACE), the Atmospheric Imaging Assembly (AIA) of the Solar Dynamics Observatory (SDO) and the High-Resolution Coronal Imager (Hi-C) are used, and comparison experiments between the existing algorithms and the developed algorithm are performed. Finally, it is found that the developed algorithm is commensurate with the two most promising algorithms, oriented coronal curved loop tracing (OCCULT) and its improved version, OCCULT-2, in performance. Therefore, for scientific applications associated with coronal loops, the developed algorithm will be a powerful tool.

scholarly journals Impulsive coronal heating during the interaction of surface magnetic fields in the lower solar atmosphere

2020 ◽  
Vol 644 ◽  
pp. A130
Author(s):  
L. P. Chitta ◽  
H. Peter ◽  
E. R. Priest ◽  
S. K. Solanki
Keyword(s):  
Solar Surface ◽  
Magnetic Energy ◽  
Active Regions ◽  
Opposite Polarity ◽  
Space Mission ◽  
Magnetic Polarity ◽  
Coronal Heating ◽  
Coronal Loops ◽  
Solar Dynamics Observatory ◽  
Solar Dynamics

Coronal plasma in the cores of solar active regions is impulsively heated to more than 5 MK. The nature and location of the magnetic energy source responsible for such impulsive heating is poorly understood. Using observations of seven active regions from the Solar Dynamics Observatory, we found that a majority of coronal loops hosting hot plasma have at least one footpoint rooted in regions of interacting mixed magnetic polarity at the solar surface. In cases when co-temporal observations from the Interface Region Imaging Spectrograph space mission are available, we found spectroscopic evidence for magnetic reconnection at the base of the hot coronal loops. Our analysis suggests that interactions of magnetic patches of opposite polarity at the solar surface and the associated energy release during reconnection are key to impulsive coronal heating.

scholarly journals Simultaneous transverse oscillations of a coronal loop and a filament excited by a circular-ribbon flare

2020 ◽  
Vol 642 ◽  
pp. A159
Author(s):  
Q. M. Zhang
Keyword(s):  
Magnetic Reconnection ◽  
Blast Wave ◽  
Coronal Loop ◽  
Extreme Ultraviolet ◽  
Transverse Oscillation ◽  
Peak Time ◽  
Coronal Loops ◽  
Solar Dynamics Observatory ◽  
X Ray ◽  
Transverse Oscillations

Aims. The aim of this study is to investigate the excitation of kink oscillations in coronal loops and filaments, by analyzing a C3.4 circular-ribbon flare associated with a blowout jet in active region 12434 on 2015 October 16. Methods. The flare was observed in ultraviolet and extreme-ultraviolet wavelengths by the Atmospheric Imaging Assembly on board the Solar Dynamics Observatory (SDO) spacecraft. The line-of-sight (LOS) magnetograms of the photosphere were observed by the Helioseismic and Magnetic Imager on board SDO. Soft X-ray fluxes of the flares in 0.5−4 and 1−8 Å were recorded by the GOES spacecraft. Results. The flare excited small-amplitude kink oscillation of a remote coronal loop. The oscillation lasted for ≥4 cycles without significant damping. The amplitude and period are 0.3 ± 0.1 Mm and 207 ± 12 s. Interestingly, the flare also excited transverse oscillation of a remote filament. The oscillation lasted for ∼3.5 cycles with decaying amplitudes. The initial amplitude is 1.7−2.2 Mm. The period and damping time are 437−475 s and 1142−1600 s. The starting times of simultaneous oscillations of coronal loop and filament were concurrent with the hard X-ray peak time. Though small in size and short in lifetime, the flare set off a chain reaction. It generated a bright secondary flare ribbon (SFR) in the chromosphere, remote brightening (RB) that was cospatial with the filament, and intermittent, jet-like flow propagating in the northeast direction. Conclusions. The loop oscillation is most probably excited by the flare-induced blast wave at a speed of ≥1300 km s−1. The excitation of the filament oscillation is more complicated. The blast wave triggers secondary magnetic reconnection far from the main flare, which not only heats the local plasma to higher temperatures (SFR and RB), but produces jet-like flow (i.e., reconnection outflow) as well. The filament is disturbed by the secondary magnetic reconnection and experiences transverse oscillation. These findings provide new insight into the excitation of transverse oscillations of coronal loops and filaments.

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