Determination of the coronal magnetic field by
 coronal loop oscillations

Nakariakov, V. M.; Ofman, L.

doi:10.1051/0004-6361:20010607

Cited by 489 publications

(481 citation statements)

References 13 publications

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“…Transverse coronal-loop oscillations have been detected by TRACE (Aschwanden et al 1999a(Aschwanden et al , 2003a and interpreted as global kink-mode oscillations with periods of ≈280 s. These oscillations can be excited by strong flares, but occasionally also by filament eruptions . Nakariakov and Ofman (2001) estimated the magnetic field strength in an oscillating loop to be ≈1.3 mT. Slow magnetoacoustic disturbances propagating with speeds of roughly 100 km s −1 have been observed by the EIT and TRACE instruments in active-region loops (Robbrecht et al 2001).…”

Section: Coronal Oscillations and Wavesmentioning

confidence: 99%

Observations of the Sun at Vacuum-Ultraviolet Wavelengths from Space. Part II: Results and Interpretations

et al. 2007

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In Part I of this review, the concepts of solar vacuum-ultraviolet (VUV) observations were outlined together with a discussion of the space instrumentation used for the investigations. A section on spectroradiometry provided some quantitative results on the solar VUV radiation without considering any details of the solar phenomena leading to the radiation. Here, in Part II, we present solar VUV observations over the last decades and their interpretations in terms of the plasma processes and the parameters of the solar atmosphere, with emphasis on the spatial and thermal structures of the chromosphere, transition region and corona of the quiet Sun. In addition, observations of active regions, solar flares and prominences are included as well as of small-scale events. Special sections are devoted to the elemental composition of the solar atmosphere and theoretical considerations on the heating of the corona and the generation of the solar wind.

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Section: Coronal Oscillations and Wavesmentioning

confidence: 99%

Observations of the Sun at Vacuum-Ultraviolet Wavelengths from Space. Part II: Results and Interpretations

et al. 2007

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“…Besides the loop's average Alfvén speed and magnetic field strength (Nakariakov & Ofman 2001), there is the potential for seismologically determining the loop cross-section profile, including the density contrast, which is difficult to measure directly (e.g. Aschwanden et al 2003;Schmelz et al 2003;Terzo & Reale 2010).…”

Section: Introductionmentioning

confidence: 99%

Statistical seismology of transverse waves in the solar corona

Verwichte

Doorsselaere

White

et al. 2013

A&A

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Context. Observations show that transverse oscillations commonly occur in solar coronal loops. The rapid damping of these waves has been attributed to resonant absorption. The oscillation characteristics carries information of the structuring of the corona. However, self-consistent seismological methods that extract information from individual oscillations are limited because there are fewer observables than unknown parameters in the model, and the problem is underdetermined. Furthermore, it has been shown that one-to-one comparisons of the observed scaling of period and damping times with wave damping theories are misleading. Aims. We aim to investigate whether seismological information can be gained from the observed scaling laws in a statistical sense. Methods. A statistical approach is used whereby scaling laws are produced by forward modelling using distributions of values for key loop cross-sectional structuring parameters. We study two types of observations: 1) transverse loops oscillations as seen mainly with TRACE and SDO and 2) running transverse waves seen with the Coronal Multichannel Polarimeter (CoMP). Results. We demonstrate that the observed period-damping time scaling law does provide information about the physical damping mechanism, if observations are collected from as wide range of periods as possible and a comparison with theory is performed in a statistical sense. The distribution of the ratio of damping time over period, i.e. the quality factor, has been derived analytically and fitted to the observations. A minimum value for the quality factor of 0.65 has been found. From this, a constraint linking the ranges of possible values for the density contrast and inhomogeneity layer thickness is obtained for transverse loop oscillations. If the layer thickness is not constrained, then the density contrast is at most equal to 3. For transverse waves seen by CoMP, it is found that the ratio of maximum to minimum values for these two parameters has to be less than 2.06; i.e., the sampled values for the layer thickness and Alfvén travel time come from a relatively narrow distribution. Conclusions. Now that more and more transverse loop oscillations have been analysed, a statistical approach to coronal seismology becomes possible. Using the observed data cloud, we have found restrictions to the loop's density contrast and inhomogeneity layer thickness. Surprisingly, for running waves, narrow distributions for loop parameters have been found.

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“…Arregui et al 2005;Terradas et al 2006aTerradas et al ,b, 2008 modelling efforts and doing coronal seismology (e.g. Nakariakov & Ofman 2001;Andries et al 2005a;Arregui et al 2007). The current observational sample size of such oscillations is very limited, with up to 30 known events (Aschwanden et al 2002).…”

Section: Introductionmentioning

confidence: 99%

Detection of three periodicities in a single oscillating coronal loop

Doorsselaere

Birtill

Evans

2009

A&A

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Context. TRACE 171 Å observations of transverse loop oscillations on May 13, 2001 have been studied by De Moortel & Brady (2007). They found hints of 3 periodicities present in this event.Aims. The aim of this article is to improve the analysis, and measure the periodicities more accurately in order to do coronal seismology. Methods. We create multiple (x, t)-slices across the loop, and determine the oscillatory parameters within those slices. We then use statistical methods to reduce the errors on the measured oscillations parameters. Results. We find two populations with a clearly distinct period. The population at the loop top has a period of 895 ± 2 s, while the population in the loop leg has a period of 452 ± 1 s. The fact that the ratio of these two periods is roughly 2 and the geometry of the problem suggests that two harmonics are observed. In the residues, we confirm the presence of a 3rd harmonic with period 309 ± 15 s using two separate data analysis techniques. The three periods are then used to do a seismological estimate of the loop expansion and the density scale height.

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Determination of the coronal magnetic field by coronal loop oscillations

Cited by 489 publications

References 13 publications

Observations of the Sun at Vacuum-Ultraviolet Wavelengths from Space. Part II: Results and Interpretations

Observations of the Sun at Vacuum-Ultraviolet Wavelengths from Space. Part II: Results and Interpretations

Statistical seismology of transverse waves in the solar corona

Detection of three periodicities in a single oscillating coronal loop

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