scholarly journals Observation and Modeling of Chromospheric Evaporation in a Coronal Loop Related to Active Region Transient Brightening

2018 ◽  
Vol 857 (2) ◽  
pp. 137 ◽  
Author(s):  
G. R. Gupta ◽  
Aveek Sarkar ◽  
Durgesh Tripathi
Keyword(s):  
Active Region ◽  
Coronal Loop ◽  
Chromospheric Evaporation

scholarly journals Contribution of observed multi frequency spectrum of Alfvén waves to coronal heating

2019 ◽  
Vol 623 ◽  
pp. A37 ◽  
Author(s):  
P. Pagano ◽  
I. De Moortel
Keyword(s):  
Active Region ◽  
Power Spectrum ◽  
Solar Corona ◽  
Coronal Loop ◽  
Alfven Waves ◽  
Mhd Waves ◽  
Alfvén Waves ◽  
Coronal Loops ◽  
Phase Mixing ◽  
Transverse Oscillations

Context. Whilst there are observational indications that transverse magnetohydrodynamic (MHD) waves carry enough energy to maintain the thermal structure of the solar corona, it is not clear whether such energy can be efficiently and effectively converted into heating. Phase-mixing of Alfvén waves is considered a candidate mechanism, as it can develop transverse gradient where magnetic energy can be converted into thermal energy. However, phase-mixing is a process that crucially depends on the amplitude and period of the transverse oscillations, and only recently have we obtained a complete measurement of the power spectrum for transverse oscillations in the corona. Aims. We aim to investigate the heating generated by phase-mixing of transverse oscillations triggered by buffeting of a coronal loop that follows from the observed coronal power spectrum as well as the impact of these persistent oscillations on the structure of coronal loops. Methods. We considered a 3D MHD model of an active region coronal loop and we perturbed its footpoints with a 2D horizontal driver that represents a random buffeting motion of the loop footpoints. Our driver was composed of 1000 pulses superimposed to generate the observed power spectrum. Results. We find that the heating supply from the observed power spectrum in the solar corona through phase-mixing is not sufficient to maintain the million-degree active region solar corona. We also find that the development of Kelvin–Helmholtz instabilities could be a common phenomenon in coronal loops that could affect their apparent life time. Conclusions. This study concludes that is unlikely that phase-mixing of Alfvén waves resulting from an observed power spectrum of transverse coronal loop oscillations can heat the active region solar corona. However, transverse waves could play an important role in the development of small scale structures.

scholarly journals Coronal loop seismology using multiple transverse loop oscillation harmonics

2007 ◽  
Vol 3 (S247) ◽  
pp. 140-146 ◽  
Author(s):  
T. Van Doorsselaere ◽  
V. M. Nakariakov ◽  
E. Verwichte
Keyword(s):  
Time Series ◽  
Active Region ◽  
Coronal Loop ◽  
Scale Height ◽  
Coronal Seismology ◽  
Physical Quantities ◽  
Density Scale ◽  
Oscillation Properties

AbstractTRACE observations (23/11/1998 06:35:57-06:48:43UT) in the 171 Å bandpass of an active region are studied. Coronal loop oscillations are observed after a violent disruption of the equilibrium. The oscillation properties are studied to give seismological estimates of physical quantities, such as the density scale height. A loop segment is traced during the oscillation, and the resulting time series is analysed for periodicities. In the loop segment displacement, two periods are found: 435.6±4.5 s and 242.7±6.4 s, consistent with the periods of the fundamental and 2nd harmonic fast kink oscillation. The small uncertainties allow us to estimate the density scale height in the loop to be 109 Mm, which is about double the estimated hydrostatical value of 50 Mm. The eigenfunction is used to do spatial coronal seismology, but that method does not give any conclusive results.

scholarly journals Simulating Coronal Loop Implosion and Compressible Wave Modes in a Flare Hit Active Region

2017 ◽  
Vol 851 (2) ◽  
pp. 120 ◽  
Author(s):  
Aveek Sarkar ◽  
Bhargav Vaidya ◽  
Soumitra Hazra ◽  
Jishnu Bhattacharyya
Keyword(s):  
Active Region ◽  
Coronal Loop ◽  
Wave Modes

scholarly journals Chromospheric evaporation and phase mixing of Alfvén waves in coronal loops

2020 ◽  
Vol 635 ◽  
pp. A174
Author(s):  
H. J. Van Damme ◽  
I. De Moortel ◽  
P. Pagano ◽  
C. D. Johnston
Keyword(s):  
Density Gradient ◽  
High Frequency ◽  
Coronal Loop ◽  
Alfven Waves ◽  
Alfvén Waves ◽  
Mixing Process ◽  
Phase Mixing ◽  
Field Density ◽  
Chromospheric Evaporation ◽  
The Cross

Context. Phase mixing of Alfvén waves has been studied extensively as a possible coronal heating mechanism but without the full thermodynamic consequences considered self-consistently. It has been argued that in some cases, the thermodynamic feedback of the heating could substantially affect the transverse density gradient and even inhibit the phase mixing process. Aims. In this paper, for the first time, we use magnetohydrodynamic (MHD) simulations with the appropriate thermodynamical terms included to quantify the evaporation following heating by phase mixing of Alfvén waves in a coronal loop and the effect of this evaporation on the transverse density profile. Methods. The numerical simulations were performed using the Lagrangian Remap code Lare2D. We set up a 2D loop model consisting of a field-aligned thermodynamic equilibrium and a cross-field (background) heating profile. A continuous, sinusoidal, high-frequency Alfvén wave driver was implemented. As the Alfvén waves propagate along the field, they undergo phase mixing due to the cross-field density gradient in the coronal part of the loop. We investigated the presence of field-aligned flows, heating from the dissipation of the phase-mixed Alfvén waves, and the subsequent evaporation from the lower atmosphere. Results. We find that phase mixing of Alfvén waves leads to modest heating in the shell regions of the loop and evaporation of chromospheric material into the corona with upflows of the order of only 5–20 m s−1. Although the evaporation leads to a mass increase in the shell regions of the loop, the effect on the density gradient and, hence, on the phase mixing process, is insignificant. Conclusions. This paper self-consistently investigates the effect of chromospheric evaporation on the cross-field density gradient and the phase mixing process in a coronal loop. We found that the effects in our particular setup (small amplitude, high frequency waves) are too small to significantly change the density gradient.

scholarly journals Decametric Radio Bursts Associated with Coronal Loop Structures

1980 ◽  
Vol 86 ◽  
pp. 435-438
Author(s):  
T. E. Gergely ◽  
M. R. Kundu ◽  
L. Golub ◽  
D. Webb
Keyword(s):  
Active Region ◽  
Coronal Loop ◽  
Opposite Polarity ◽  
Small Scale ◽  
List Type ◽  
Radio Bursts ◽  
Type Number ◽  
X Ray ◽  
Decameter Wavelength ◽  
Different Types

The soft x-ray (2–54 Å) pictures obtained by the S-054 experiment aboard SKYLAB provide an excellent opportunity to study the association of x-ray loop structures with radio bursts. We report here on the properties of meter-decameter wavelength radio bursts which appear to be associated with two different types of loop structures: a)Relatively short lived small scale loops, which are observed to link magnetic fields of opposite polarity, called x-ray bright points (XBPs); andb)Longer lived loop systems which appear to connect opposite magnetic polarities of an active region and active region complexes as well.

scholarly journals High-frequency oscillations in a solar active region coronal loop

2001 ◽  
Vol 326 (2) ◽  
pp. 428-436 ◽  
Author(s):  
D.R. Williams ◽  
K.J.H. Phillips ◽  
P. Rudawy ◽  
M. Mathioudakis ◽  
P.T. Gallagher ◽  
...  
Keyword(s):  
Active Region ◽  
High Frequency ◽  
Coronal Loop ◽  
Solar Active Region ◽  
High Frequency Oscillations

scholarly journals Restricted propagation of an “EIT wave” in the low solar corona

2015 ◽  
Vol 11 (S320) ◽  
pp. 98-102
Author(s):  
David M. Long ◽  
David Pérez–Suárez ◽  
Gherardo Valori
Keyword(s):  
Active Region ◽  
Solar Corona ◽  
Coronal Hole ◽  
Magnetic Structure ◽  
Coronal Loop ◽  
Three Dimensional ◽  
Loop System ◽  
Data Sets ◽  
Class Flare ◽  
Insight Into

AbstractWe present observations of an “EIT wave” associated with an X-class flare from 2012 July 6, the propagation of which was severely restricted by the magnetic structure of the solar corona surrounding the erupting active region. The “EIT wave” was observed by both SDO and STEREO-A, allowing a three-dimensional examination of how the propagation of the disturbance was affected both by a neighbouring coronal hole and a trans-equatorial loop system. In addition, the eruption was observed at the limb by the ground-based CoMP instrument, allowing the Doppler motion associated with the eruption and resulting coronal loop oscillation to be investigated in detail. This combination of data-sets provides a unique insight into the three-dimensional evolution of the “EIT wave” and its effects on the surrounding corona.

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