E-Print Archive

There are 1713 abstracts currently viewable.


Search:

Advanced Search
Options
Main Page Add New E-Print Submitter
Information
Feedback
News Help/FAQ About Preferences
Manage Key Phrase
Notification
Damping of Fast Magnetohydrodymanic Oscillations in Quiescent Filament Threads  

Inigo Arregui   Submitted: 2008-06-18 02:46

High-resolution observations provide evidence about the existence of small-amplitude transverse oscillations in solar filament fine structures. These oscillations are believed to represent fast magnetohydrodynamic (MHD) waves and the disturbances are seen to be damped in short timescales of the order of 1 to 4 periods. In this Letter we propose that, due to the highly inhomogeneous nature of the filament plasma at the fine structure spatial scale, the phenomenon of resonant absorption is likely to operate in the temporal attenuation of fast MHD oscillations. By considering transverse inhomogeneity in a straight flux tube model we find that, for density inhomogeneities typical of filament threads, the decay times are of a few oscillatory periods only.

Authors: Inigo Arregui, Jaume Terradas, Ramon Oliver, Jose Luis Ballester
Projects: None

Publication Status: ApJ Letters, accepted
Last Modified: 2008-09-23 20:59
Go to main E-Print page  Edit Entry  Download Preprint  Submitter's Homepage Delete Entry 

Subject will be restored when possible  

Inigo Arregui   Submitted: 2008-04-24 04:00

We present an analytic approximate seismic inversion scheme for damped transverse coronal loop oscillations based on the thin tube and thin boundary approximation for computing the period and the damping time. Asymptotic expressions for the period and damping rate are used to illustrate the process of seismological inversion in a simple and easy to follow manner. The inversion procedure is formulated in terms of two simple functions, which are given by simple closed expressions. The analytic seismic inversion shows that an infinite amount of 1-dimensional equilibrium models can reproduce the observed periods and damping times. It predicts a specific range of allowable values for the Alfv'en travel time and lower bounds for the density contrast and the inhomogeneity length scale. When the results of the present analytic seismic inversion are compared with those of a previous numerical inversion, excellent agreement is found up to the point that the analytic seismic inversion emerges as a tool for validating results of numerical inversions. Actually it helped us to identify and correct inaccuracies in a previous numerical investigation.

Authors: M. Goossens, I. Arregui, J.L. Ballester, T.J. Wang
Projects: None

Publication Status: A&A, accepted
Last Modified: 2008-09-23 21:09
Go to main E-Print page  Edit Entry  Download Preprint  Submitter's Homepage Delete Entry 

Subject will be restored when possible  

Inigo Arregui   Submitted: 2008-02-08 09:38

There is not as yet full agreement on the mechanism that causes the rapid damping of the oscillations observed by TRACE in coronal loops. It has been suggested that the variation of the observed values of the damping time as function of the corresponding observed values of the period contains information on the possible damping mechanism. The aim of this Letter is to show that, for resonant absorption, this is definitely not the case unless detailed a priori information on the individual loops is available.

Authors: Inigo Arregui, Jose Luis Ballester, Marcel Goossens
Projects: None

Publication Status: ApJL, in press
Last Modified: 2008-02-08 12:16
Go to main E-Print page  Edit Entry  Download Preprint  Submitter's Homepage Delete Entry 

Subject will be restored when possible  

Inigo Arregui   Submitted: 2008-02-08 09:38

There is not as yet full agreement on the mechanism that causes the rapid damping of the oscillations observed by TRACE in coronal loops. It has been suggested that the variation of the observed values of the damping time as function of the corresponding observed values of the period contains information on the possible damping mechanism. The aim of this Letter is to show that, for resonant absorption, this is definitely not the case unless detailed a priori information on the individual loops is available.

Authors: Inigo Arregui, Jose Luis Ballester, Marcel Goossens
Projects:

Publication Status: ApJL, 676, L77-L80
Last Modified: 2008-03-10 02:50
Go to main E-Print page  Edit Entry  Download Preprint  Submitter's Homepage Delete Entry 

Subject will be restored when possible  

Inigo Arregui   Submitted: 2007-08-28 07:26

The theory of magnetohydrodynamic (MHD) waves in solar coronal slabs in a zero-$eta$ configuration and for parallel propagation of waves does not allow the existence of surface waves. When oblique propagation of perturbations is considered both surface and body waves are able to propagate. When the perpendicular wave number is larger than a certain value, the body kink mode becomes a surface wave. In addition, a sausage surface mode is found below the internal cut-off frequency. When non-uniformity in the equilibrium is included, surface and body modes are damped due to resonant absorption. In this paper, first, a normal-mode analysis is performed and the period, the damping rate, and the spatial structure of eigenfunctions are obtained. Then, the time-dependent problem is solved, and the conditions under which one or the other type of mode is excited are investigated.

Authors: I. Arregui, J. Terradas, R. Oliver, J.L. Ballester
Projects: None

Publication Status: Solar Physics. Accepted
Last Modified: 2007-08-30 21:46
Go to main E-Print page  Edit Entry  Download Preprint  Submitter's Homepage Delete Entry 

The resonant damping of fast magnetohydrodynamic oscillations in a system of two coronal slabs  

Inigo Arregui   Submitted: 2007-08-09 04:38

Observations of transversal coronal loop oscillations very often show the excitation and damping of oscillations in groups of coronal loops rather than in individual and isolated structures. We present results on the oscillatory properties (periods, damping rates, and spatial distribution of perturbations) for resonantly damped oscillations in a system of two inhomogeneous coronal slabs and compare them to the properties found in single slab loop models. A system of two identical coronal loops is modeled, in Cartesian geometry, as being composed by two density enhancements. The linear magnetohydrodynamic (MHD) wave equations for oblique propagation of waves are solved and the damping of the different solutions, due to the transversal inhomogeneity of the density profile, is computed. The physics of the obtained results is analyzed by an examination of the perturbed physical variables. We find that, due to the interaction between the loops, the normal modes of oscillation present in a single slab split into symmetric and antisymmetric oscillations when a system of two identical slabs is considered. The frequencies of these solutions may differ from the single slab results when the distance between the loops is of the order of a few slab widths. Oblique propagation of waves weakens this interaction, since solutions become more confined to the edges of the slabs. The damping is strong for surface-like oscillations, while sausage body-like solutions are unaffected. For some solutions, and small slab separations, the damping in a system of two loops differs substantially from the damping of a single loop.

Authors: Inigo Arregui, Jaume Terradas, Ramon Oliver, Jose Luis Ballester
Projects:

Publication Status: Submitted
Last Modified: 2007-08-10 11:00
Go to main E-Print page  Edit Entry  Download Preprint  Submitter's Homepage Delete Entry 

The influence of the internal structuring of coronal loops on the properties of their damped transverse oscillations  

Inigo Arregui   Submitted: 2007-02-08 07:37

The geometry and physical conditions in solar coronal loops are complicated and still not well understood. Recent high resolution observations, obtained with TRACE, indicate the existence of sub-resolution transverse structuring, not accessible to direct observation. This ingredient has not yet been taken into account in previous theoretical models used for the study of transversal coronal loop oscillations and their damping due to resonant conversion of energy. This study aims to assess the effect of the possibly unresolved internal structure of a coronal loop on the properties of its transverse oscillations and on the efficiency of resonant absorption as a damping mechanism of these oscillations. The equilibrium configuration of a single coronal loop with internal density structuring is modelled by considering the loop as being composed by two very close parallel identical coronal slabs in Cartesian geometry. The period of the oscillation and the damping time, for the resonantly damped fundamental kink mode, are computed. These quantities are then compared to those obtained for two models for a single equivalent slab without internal density structuring. We find that the period and the damping time of a coronal loop with internal density structuring change by less than 15\%, when compared to the same oscillatory properties of a single coronal loop with either the same density contrast or a single coronal loop with the same total mass. Therefore the internal density structuring of a coronal loop does not affect very much its oscillatory properties. However, the sub-resolution structuring of a coronal loop, with different densities in its components or with different widths could vary these results.

Authors: I. Arregui, J. Terradas, R. Oliver, & J.L. Ballester
Projects:

Publication Status: A&A, Vol. 466, 1145-1151 (2007)
Last Modified: 2007-04-26 02:46
Go to main E-Print page  Edit Entry  Download Preprint  Submitter's Homepage Delete Entry 

MHD seismology of coronal loops using the period and damping of quasi-mode kink oscillations  

Inigo Arregui   Submitted: 2006-11-23 01:45

We combine the magnetohydrodynamic (MHD) theory of resonantly damped quasi-mode kink oscillations with observational estimates of the period and damping of transverse coronal loop oscillations to extract information on physical parameters in oscillating loops. A numerical study of the quasi-mode period and damping, in one-dimensional fully non-uniform flux tubes, is used to obtain equilibrium models that reproduce the observed periods and damping rates. This scheme is applied to 11 loop oscillation events. When only the damping rate is used, the valid equilibrium models form a one-dimensional solution curve in the two-dimensional parameter space (density contrast, transverse inhomogeneity length-scale). Lower limits to the transverse inhomogeneity are obtained in the limit of high contrast loops. When both the period and the damping rate are used, the equilibrium Alfven speed (or Alfven travel time) comes into play. The valid equilibrium models then form a one-dimensional solution curve, in the three-dimensional parameter space (density contrast, transverse inhomogeneity length-scale, Alfven speed or Alfven travel time). The projection of these solutions onto the Alfven speed axis is found to be constrained to a rather limited interval. Upper limits to the internal Alfven speed are derived for 9 of the 11 analysed events.

Authors: I. Arregui, J. Andries, T. Van Doorsselaere, M. Goossens, S. Poedts
Projects:

Publication Status: Published, A&A, Vol 463, 333-338
Last Modified: 2007-01-30 05:20
Go to main E-Print page  Edit Entry  Download Preprint  Submitter's Homepage Delete Entry 


Key
Go to main E-Print pageGo to main E-Print page.
Download PreprintDownload Preprint.
Submitter's HomepageSubmitters Homepage.
Edit EntryEdit Entry.
Delete AbstractDelete abstract.

Abstracts by Author
Damping of Fast Magnetohydrodymanic Oscillations in Quiescent Filament Threads
Subject will be restored when possible
Subject will be restored when possible
Subject will be restored when possible
Subject will be restored when possible
The resonant damping of fast magnetohydrodynamic oscillations in a system of two coronal slabs
The influence of the internal structuring of coronal loops on the properties of their damped transverse oscillations
MHD seismology of coronal loops using the period and damping of quasi-mode kink oscillations

Related Pages
MSU Solar Physics.
Max Millennium Science Mail Archive.
Max Millennium Message of the Day Mail Archive.
Max Millennium Flare Catalog

Archive Maintainer
Alisdair Davey



© 2003 Solar Physics Group - Montana State University