Line-of-sight effects on observability of kink and sausage modes in coronal structures with imaging telescopes

By F. C. Cooper, Valery M. Nakariakov, D. Tsiklauri. 2002

175 citations recorded by the source corpus.

Kink modes of solar coronal structures, perturbing the loop in the direction along the line-of-sight (LOS), can be observed as emission intensity disturbances propagating along the loop provided the angle between the LOS and the structure is not ninety degrees. The effect is based upon the change of the column depth of the loop (along the LOS) by the wave. The observed amplitude of the emission intensity variations can be larger than the actual amplitude of the wave by a factor of two and there is an optimal angle maximizing the observed amplitude. For other angles this effect can also attenuate the observed wave amplitude. The observed amplitude depends upon the ratio of the wave length of kink perturbations to the width of the structure and on the angle between the LOS and the axis of the structure. Sausage modes are always affected negatively from the observational point of view, as the observed amplitude is always less than the actual one. This effect should be taken into account in the interpretation of wave phenomena observed in the corona with space-borne and ground-based imaging telescopes.

Subfields: Astronomy and Astrophysics, Nuclear and High Energy Physics

View Paper: https://www.semanticscholar.org/paper/95df2ec872dfdf357dd1458936158b629aec6f62

How researchers see this paper

The researchers whose trusted networks rank it highest, strongest advocate first. Every researcher gets a different order.

In Astronomy and Astrophysics

1. Andrea Kotrlová
2. G. Torok
3. Zdenek Stuchlík

In Nuclear and High Energy Physics

1. Andrea Kotrlová
2. G. Torok
3. Zdenek Stuchlík

Citations in the corpus

• Multi-resonance orbital model of high-frequency quasi-periodic oscillations: possible high-precision determination of black hole and neutron star spin (2013, background): “…detected at lower frequencies, 600− 800 Hz vs. upper frequencies 900− 1200 Hz, demonstrating a clustering of the twin HF QPOs frequency ratio around 3 : 2 and thus indicating some analogy to the BH case (Abramowicz et al. 2003a; Belloni et al. 2007a; Török et al. 2008a,b,c; Boutelier et al. 2010).”
• Decayless low-amplitude kink oscillations: a common phenomenon in the solar corona? (2015, unknown): “…of the brightness itself as a result of the modulation of the column depth of the oscillating plasma non-uniformity by the oscillation (e.g. Cooper et al. 2003; Verwichte et al. 2009), or the periodic Doppler shift of coronal emission lines (e.g. Koutchmy et al. 1983; Tomczyk et al. 2007).”
• Oscillations and Waves in Sunspots (2015, unknown): “In the transition region and corona, filters are usually broad and contain in their bandpass emission lines formed at high temperatures and their brightness variation can be interpreted in terms of density variations or variations of column depth (Cooper et al., 2003).”
• Coronal Seismology by Means of Kink Oscillation Overtones (2009, unknown): “However, they observe the oscillations in the intensity, relying on an argument by Cooper et al. (2003) where the intensity oscillations are caused by a variation of the column depth during the oscillation.”
• CORONAL LOOP OSCILLATIONS OBSERVED WITH ATMOSPHERIC IMAGING ASSEMBLY—KINK MODE WITH CROSS-SECTIONAL AND DENSITY OSCILLATIONS (2011, unknown): “…of the amplitude-correlated flux variation is an aspect-angle change of the oscillating loop, which causes a variable line-of-sight column depth of the loop diameter w(t) = w0 cos[ϑ(t)] (Cooper et al. 2003), and hence would introduce a variation of the optically thin EUV flux f (t) ∝ n2e(t)w(t).”
• Advances in Observing Various Coronal EUV Waves in the SDO Era and Their Seismological Applications (Invited Review) (2014, unknown): “Such a distance is required for amplitude growth or a preferential LOS to be satisfied for detecting them (Cooper, Nakariakov, and Tsiklauri, 2003).”