Undamped transverse oscillations of coronal loops as a self-oscillatory process

Context. The relatively large-amplitude decaying regime of transverse oscillations of coronal loops has been known for two decades and has been interpreted in terms of magnetohydrodynamic kink modes of cylindrical plasma waveguides. In this regime oscillations decay in several cycles. Recent observational analysis has revealed so-called decay-less, small-amplitude oscillations, in which a multi-harmonic structure has been detected. Several models have been proposed to explain these oscillations. In particular, decay-less oscillations have been described in terms of standing kink waves driven with continuous mono-periodic motions of loop footpoints, in terms of a simple oscillator model of forced oscillations due to harmonic external force, and as a self-oscillatory process due to the interaction of a loop with quasi-steady flows. However, an alternative mechanism is needed to explain the simultaneous excitation of several longitudinal harmonics of the oscillation. Aims. We study the mechanism of random excitation of decay-less transverse oscillations of coronal loops. Methods. With a spatially one-dimensional and time-dependent analytical model taking into account effects of the wave damping and kink speed variation along the loop, we considered transverse loop oscillations driven by random motions of footpoints. The footpoint motions were modelled by broad-band coloured noise. Results. We found the excitation of loop eigenmodes and analysed their frequency ratios as well as the spatial structure of the oscillations along the loop. The obtained results successfully reproduce the observed properties of decay-less oscillations. In particular, excitation of eigenmodes of a loop as a resonator can explain the observed quasi-monochromatic nature of decay-less oscillations and the generation of multiple harmonics detected recently. Conclusions. We propose a mechanism that can interpret decay-less transverse oscillations of coronal loops in terms of kink waves randomly driven at the loop footpoints.

Download Full-text

The effect of foot-point boundary conditions on transverse oscillations of cooling coronal loops

Monthly Notices of the Royal Astronomical Society ◽

10.1093/mnras/stx504 ◽

2017 ◽

Vol 468 (3) ◽

pp. 2781-2787 ◽

Cited By ~ 1

Author(s):

K. Bahari

Keyword(s):

Boundary Conditions ◽

Coronal Loops ◽

Point Boundary ◽

Transverse Oscillations

Download Full-text

Theory of Transverse Oscillations of Solar Coronal Loops

10.1063/1.3137928 ◽

2009 ◽

Author(s):

M. S. Ruderman ◽

Ivan Zhelyazkov

Keyword(s):

Coronal Loops ◽

Transverse Oscillations ◽

Solar Coronal

Download Full-text

Transverse oscillations in solar coronal loops induced by propagating Alfvénic pulses

Astronomy and Astrophysics ◽

10.1051/0004-6361:20041880 ◽

2005 ◽

Vol 431 (3) ◽

pp. 1095-1104 ◽

Cited By ~ 33

Author(s):

L. Del Zanna ◽

E. Schaekens ◽

M. Velli

Keyword(s):

Coronal Loops ◽

Transverse Oscillations ◽

Solar Coronal

Download Full-text

Transverse oscillations of non-planar coronal loops

Astronomy and Astrophysics ◽

10.1051/0004-6361/201016172 ◽

2011 ◽

Vol 529 ◽

pp. A33 ◽

Cited By ~ 8

Author(s):

M. S. Ruderman ◽

A. Scott

Keyword(s):

Coronal Loops ◽

Transverse Oscillations

Download Full-text

Temperature Analysis of Flaring (AR11283) and non-Flaring (AR12194) Coronal Loops

Research in Astronomy and Astrophysics ◽

10.1088/1674-4527/ac47ac ◽

2022 ◽

Author(s):

Narges Fathalian ◽

Seyedeh Somayeh Hosseini Rad ◽

Nasibeh Alipour ◽

Hossein Safari

Keyword(s):

Active Region ◽

Extreme Ultraviolet ◽

Coronal Loops ◽

Temperature Structure ◽

Statistical Research ◽

Time Duration ◽

Temperature Oscillations ◽

Fitting Method ◽

Long Time ◽

Transverse Oscillations

Abstract Here, we study the temperature structure of flaring and non-flaring coronal loops, using extracted loops from images taken in six extreme ultraviolet (EUV) channels recorded by Atmospheric Imaging Assembly (AIA)/ Solar Dynamic Observatory (SDO). We use data for loops of X2.1-class-flaring active region (AR11283) during 22:10UT till 23:00UT, on 2011, September 6; and non-flaring active region (AR12194) during 08:00:00UT till 09:00:00UT on 2014, October 26. By using spatially-synthesized Gaussian DEM forward-fitting method, we calculate the peak temperatures for each strip of the loops. We apply the Lomb-Scargle method to compute the oscillations periods for the temperature series of each strip. The periods of the temperature oscillations for the flaring loops are ranged from 7 min to 28.4 min. These temperature oscillations show very close behavior to the slow-mode oscillation. We observe that the temperature oscillations in the flaring loops are started at least around 10 minutes before the transverse oscillations and continue for a long time duration even after the transverse oscillations are ended. The temperature amplitudes are increased at the flaring time (during 20 min) in the flaring loops. The periods of the temperatures obtained for the non-flaring loops are ranged from 8.5 min to 30 min,but their significances are less (below 0.5) in comparison with the flaring ones (near to one). Hence the detected temperature periods for the non-flaring loops' strips are less probable in comparison with the flaring ones, and maybe they are just fluctuations. Based on our confined observations, it seems that the flaring loops' periods show more diversity and their temperatures have wider ranges of variation than the non-flaring ones. More accurate commentary in this respect requires more extensive statistical research and broader observations.

Download Full-text

Temporal evolution of oscillating coronal loops

Astronomy and Astrophysics ◽

10.1051/0004-6361/202037467 ◽

2020 ◽

Vol 638 ◽

pp. A89 ◽

Cited By ~ 2

Author(s):

C. R. Goddard ◽

G. Nisticò

Keyword(s):

Emission Measure ◽

Initial Perturbation ◽

Active Regions ◽

Coronal Loops ◽

Magnetohydrodynamic Wave ◽

Distribution Width ◽

Local Medium ◽

Dem Analysis ◽

Using Data ◽

Transverse Oscillations

Context. Transverse oscillations of coronal structures are currently intensively studied to explore the associated magnetohydrodynamic wave physics and perform seismology of the local medium. Aims. We make a first attempt to measure the thermodynamic evolution of a sample of coronal loops that undergo decaying kink oscillations in response to an eruption in the corresponding active region. Methods. Using data from the six coronal wavelengths of SDO/AIA, we performed a differential emission measure (DEM) analysis of 15 coronal loops before, during, and after the eruption and oscillation. Results. We find that the emission measure, temperature, and width of the DEM distribution undergo significant variations on timescales relevant for the study of transverse oscillations. There are no clear collective trends of increases or decreases for the parameters we analysed. The strongest variations of the parameters occur during the initial perturbation of the loops, and the influence of background structures may also account for much of this variation. Conclusions. The DEM analysis of oscillating coronal loops in erupting active regions shows evidence of evolution on timescales important for the study of oscillations. Further work is needed to separate the various observational and physical mechanisms that may be responsible for the variations in temperature, DEM distribution width, and total emission measure.

Download Full-text