Lyra Observations of Two Oscillation Modes in a Single Flare

Doorsselaere, Tom Van; Groof, A. De; Zender, Joe; Berghmans, D.; Goossens, Marcel

doi:10.1088/0004-637x/740/2/90

Cited by 79 publications

(65 citation statements)

References 37 publications

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“…This technique has been applied successfully in the corona where it is termed coronal seismology (Nakariakov & Verwichte 2005) and has been successful in determining the coronal magnetic field strength (Nakariakov et al 1999), the transverse structuring of Postdoctoral fellow of the FWO-Vlaanderen. the flux tubes (Aschwanden et al 2003;Goossens et al 2008), the coronal density stratification (Andries et al 2005), the adiabatic index and thermal conduction (Van Doorsselaere et al 2011b), and the flare plasma β (Van Doorsselaere et al 2011a).…”

Section: Introductionmentioning

confidence: 99%

Phase relations for seismology of photospheric flux tubes

Moreels

Doorsselaere

2013

A&A

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Aims. We present a mathematical framework for the seismology of photospheric flux tubes using a uniform straight cylinder as a flux-tube model. In contrast to the earlier model of Fujimura & Tsuneta (2009, ApJ, 702, 1443, we also include a non-zero gas pressure; we do not use the thin tube approximation and we use an underdense region inside the flux tube. Methods. We used the linearised ideal magnetohydrodynamic equations to describe different wave modes in the photosphere. Using the wave mode polarisations we then obtained phase relations which represent different observables. Those phase relations were used to calculate phase differences and amplitude ratios. Finally we inverted these amplitude ratios to obtain plasma parameters which are not directly observable. Results. The mathematical framework results in phase differences that can be conveniently compared with observational data to distinguish between different wave modes. Once the wave mode has been identified, the inverted amplitude ratios can be used to either analytically or numerically estimate the magnitude of plasma parameters which are not directly observable, such as the vertical wavenumber. Artificial observations of different wave modes have shown that the framework mostly succeeds in identifying the correct wave mode and in reproducing the correct plasma parameters using the inverted amplitude ratios.

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Section: Introductionmentioning

confidence: 99%

Phase relations for seismology of photospheric flux tubes

Moreels

Doorsselaere

2013

A&A

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“…A&A 578, A60 (2015) In this paper we focus on axisymmetric slow and fast sausage modes, which have recently been discovered in numerous structures, but have not been adequately modelled to estimate their energy content. They have been detected in coronal loops (De Moortel et al 2000;Wang et al 2002Wang et al , 2003Krishna Prasad et al 2012), in photospheric pores (Dorotovič et al 2008(Dorotovič et al , 2014Morton et al 2011;Moreels et al 2015), in network bright points (McAteer et al 2003;Bharti et al 2006;Martínez González et al 2011), in flares (Nakariakov et al 2003;Melnikov et al 2005;Van Doorsselaere et al 2011), and in the chromosphere (Morton et al 2012a). Some authors have attempted to estimate the amount of energy present in these observations.…”

Section: Introductionmentioning

confidence: 99%

Energy and energy flux in axisymmetric slow and fast waves

Moreels

Doorsselaere

Grant

et al. 2015

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Aims. We aim to calculate the kinetic, magnetic, thermal, and total energy densities and the flux of energy in axisymmetric sausage modes. The resulting equations should contain as few parameters as possible to facilitate applicability for different observations. Methods. The background equilibrium is a one-dimensional cylindrical flux tube model with a piecewise constant radial density profile. This enables us to use linearised magnetohydrodynamic equations to calculate the energy densities and the flux of energy for axisymmetric sausage modes.Results. The equations used to calculate the energy densities and the flux of energy in axisymmetric sausage modes depend on the radius of the flux tube, the equilibrium sound and Alfvén speeds, the density of the plasma, the period and phase speed of the wave, and the radial or longitudinal components of the Lagrangian displacement at the flux tube boundary. Approximate relations for limiting cases of propagating slow and fast sausage modes are also obtained. We also obtained the dispersive first-order correction term to the phase speed for both the fundamental slow body mode under coronal conditions and the slow surface mode under photospheric conditions.

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“…It operated in two ultraviolet wavebands: the far-UV (FUV: 1350-1750 Å) and/or near-UV (NUV: 1750-2800 Å) and was capable of providing sub-second time resolution data of flares. In addition to looking again at the oscillations reported by Welsh et al (2006), we include additional objects, plus we searched for evidence of additional periods in the data as done by Van Doorsselaere et al (2011). For this, we used two different techniques, wavelet transformation plus the empirical mode decomposition addressing different issues; how many of these UV flares on M dwarfs show oscillations, when during the flare do we see them, do we see more than one period during the flare and is there evidence for period evolution during the flare?…”

Section: Introductionmentioning

confidence: 99%