scholarly journals Excitation of decay-less transverse oscillations of coronal loops by random motions

2020 ◽  
Vol 633 ◽  
pp. L8 ◽  
Author(s):  
A. N. Afanasyev ◽  
T. Van Doorsselaere ◽  
V. M. Nakariakov
Keyword(s):  
Broad Band ◽  
Random Excitation ◽  
Forced Oscillations ◽  
Oscillatory Process ◽  
Coronal Loops ◽  
Alternative Mechanism ◽  
Steady Flows ◽  
Kink Waves ◽  
Random Motions ◽  
Transverse Oscillations

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.

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

2016 ◽  
Vol 591 ◽  
pp. L5 ◽  
Author(s):  
V. M. Nakariakov ◽  
S. A. Anfinogentov ◽  
G. Nisticò ◽  
D.-H. Lee
Keyword(s):  
Oscillatory Process ◽  
Coronal Loops ◽  
Transverse Oscillations

scholarly journals Kink Oscillations of Coronal Loops

2021 ◽  
Vol 217 (6) ◽  
Author(s):  
V. M. Nakariakov ◽  
S. A. Anfinogentov ◽  
P. Antolin ◽  
R. Jain ◽  
D. Y. Kolotkov ◽  
...  
Keyword(s):  
Oscillation Amplitude ◽  
Wave Theory ◽  
Coronal Loops ◽  
Steady Flows ◽  
Magnetohydrodynamic Wave ◽  
Minor Radius ◽  
Kink Waves ◽  
Major Radius ◽  
A Minor ◽  
Theoretical Results

AbstractKink oscillations of coronal loops, i.e., standing kink waves, is one of the most studied dynamic phenomena in the solar corona. The oscillations are excited by impulsive energy releases, such as low coronal eruptions. Typical periods of the oscillations are from a few to several minutes, and are found to increase linearly with the increase in the major radius of the oscillating loops. It clearly demonstrates that kink oscillations are natural modes of the loops, and can be described as standing fast magnetoacoustic waves with the wavelength determined by the length of the loop. Kink oscillations are observed in two different regimes. In the rapidly decaying regime, the apparent displacement amplitude reaches several minor radii of the loop. The damping time which is about several oscillation periods decreases with the increase in the oscillation amplitude, suggesting a nonlinear nature of the damping. In the decayless regime, the amplitudes are smaller than a minor radius, and the driver is still debated. The review summarises major findings obtained during the last decade, and covers both observational and theoretical results. Observational results include creation and analysis of comprehensive catalogues of the oscillation events, and detection of kink oscillations with imaging and spectral instruments in the EUV and microwave bands. Theoretical results include various approaches to modelling in terms of the magnetohydrodynamic wave theory. Properties of kink oscillations are found to depend on parameters of the oscillating loop, such as the magnetic twist, stratification, steady flows, temperature variations and so on, which make kink oscillations a natural probe of these parameters by the method of magnetohydrodynamic seismology.

scholarly journals Seismology of kink oscillations in coronal loops: Two decades of resonant damping

2007 ◽  
Vol 3 (S247) ◽  
pp. 228-242 ◽  
Author(s):  
Marcel Goossens
Keyword(s):  
Wave Theory ◽  
Resonant Absorption ◽  
Mhd Waves ◽  
Coronal Loops ◽  
Equilibrium Models ◽  
Kink Waves ◽  
The Common ◽  
Uniform Equilibrium ◽  
Transverse Oscillations ◽  
Alfven Velocity

AbstractThe detection of rapidly damped transverse oscillations in coronal loops by Aschwanden et al. (1999) and Nakariakov et al. (1999) gave a strong impetus to the study of MHD waves and their damping. The common interpretation of the observations of these oscillations is based on kink modes. This paper reviews how the observed period and damping time can be reproduced by MHD wave theory when non-uniform equilibrium models are considered that have a transversal variation of the local Alfven velocity. The key point here is that resonant absorption cannot be avoided and occurs as natural damping mechanism for kink waves in non-uniform equilibrium models. The present paper starts with work by Hollweg & Yang (1988) and discusses subsequent developments in theory and their applications to seismology of coronal loops. It addresses the consistent use of observations of periods and damping times as seismological tools within the framework of resonant absorption. It shows that within the framework of resonant absorption infinitely many equilibrium models can reproduce the observed values of periods and damping times.

Vibration Durability of Sn3.0Ag0.5Cu (SAC305) Solder Interconnects: Harmonic and Random Excitation

2009 ◽  
Vol 52 (1) ◽  
pp. 63-86 ◽  
Author(s):  
Y. Zhou ◽  
G. Plaza ◽  
A. Dasgupta ◽  
M. Osterman
Keyword(s):  
Random Vibration ◽  
Room Temperature ◽  
Failure Modes ◽  
Broad Band ◽  
Random Excitation ◽  
Fatigue Properties ◽  
Time To Failure ◽  
Test Matrix ◽  
Vibration Excitation ◽  
Plastic Ball

In this study, the durability of lead (Pb)-free tin(Sn3.0)silver(Ag0.5)copper(Cu) (SAC305) printed wiring assemblies (PWAs) is investigated under constant amplitude, narrow-band (harmonic) excitation and under step-stress broad-band (random) excitation, and compared to the durability of Pb-based Sn37Pb PWAs. The results show that Sn37Pb assemblies last longer than SAC305 assemblies at similar excitation levels, for both harmonic and random excitations used in this study. The test specimens are identical for all tests, consisting of a PWA with plastic ball grid array components, quad flat pack components, leadless ceramic chip carriers, and leadless chip resistors. The test matrix includes test boards with different kinds of finishes and different aging conditions. Both the harmonic and random vibration tests are conducted on single-axis electrodynamic shakers. The harmonic vibration excitation is applied to a single specimen at a time, while the random vibration excitation is applied simultaneously to 20 test specimens using a specially designed test fixture. The flexural response of each test specimen mounted in the fixture is first thoroughly characterized before conducting the durability experiment. The flexural strain histories, measured on the PWAs, are used to compare the performance of the assemblies at different excitation conditions and also as inputs in other studies for stress analysis to quantify the damage in the solder joints.1 The durability tests are then conducted and time-to-failure is documented for the entire test matrix. The random durability tests are conducted at three temperatures: 125 °Centigrade (C), 25 °C (room temperature), and -40 °C. The harmonic tests are conducted only at room temperature. Destructive failure analysis (cross-sectioning, polishing, and microscopy) is conducted to confirm the failure modes. The test results presented here are analyzed in related publications1 to extract the high-cycle fatigue properties of the SAC305 and Sn37Pb solder materials.

scholarly journals Transverse oscillations in solar coronal loops induced by propagating Alfvénic pulses

2005 ◽  
Vol 431 (3) ◽  
pp. 1095-1104 ◽  
Author(s):  
L. Del Zanna ◽  
E. Schaekens ◽  
M. Velli
Keyword(s):  
Coronal Loops ◽  
Transverse Oscillations ◽  
Solar Coronal

scholarly journals Transverse oscillations of non-planar coronal loops

2011 ◽  
Vol 529 ◽  
pp. A33 ◽  
Author(s):  
M. S. Ruderman ◽  
A. Scott
Keyword(s):  
Coronal Loops ◽  
Transverse Oscillations

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

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.

Sign in / Sign up

Export Citation Format

Share Document