Spatial distributions of sunspot oscillation modes at different temperatures

Abstract

Three-and five-minute oscillations of sunspots have different spatial distributions in the solar atmospheric layers. The spatial distributions are crucial to reveal the physical origin of sunspot oscillations and to investigate their propagation. In this study, six sunspots observed by Solar Dynamics Observatory/Atmospheric Imaging Assembly were used to obtain the spatial distributions of three-and five-minute oscillations. The fast Fourier transform method is applied to represent the power spectra of oscillation modes. We find that, from the temperature minimum to the lower corona, the powers of the five-minute oscillation exhibit a circle-shape distribution around its umbra, and the shapes gradually expand with temperature increase. However, the circle-shape is disappeared and the powers of the oscillations appear to be very disordered in the higher corona. This indicates that the five-minute oscillation can be suppressed in the high-temperature region. For the three-minute oscillations, from the temperature minimum to the high corona, their powers mostly distribute within an umbra, and part of them locate at the coronal fan loop structures. Moreover, those relative higher powers are mostly concentrated in the position of coronal loop footpoints.

Doppler shift oscillations of a sunspot detected by CYRA and IRIS

“…An interesting aspect is that the sunspot oscillation can be spatially resolved in the Doppler shifts, i.e., they can be discovered in three directions above sunspot at the solar atmosphere, for instance the directions that are perpendicular and parallel to the CYRA slit, and also parallel to the IRIS slit. This is different from previous spatial distributions of sunspot oscillations observed in intensity images (e.g., Yuan et al 2014;Wang et al 2020;Yurchyshyn et al 2020). Figures 3 and 4 demonstrate that the sunspot oscillations at the umbra and penumbra can appear in the directions perpendicular and parallel to the CYRA slits, including the long period of nearly 5 min and the short period of around 3 min.…”

“…Sunspot oscillations can be observed at various layers in solar atmosphere, and are often interpreted in terms of magnetohydrodynamic waves (e.g., Bogdan 2000;Chae & Goode 2015;Khomenko & Collados 2015;Jess et al 2016;Zhugzhda & Sych 2018;Chae et al 2019). The dominant period of sunspot oscillations in the low solar atmosphere (photosphere) is about five minutes (Beckers & Schultz 1972;Lites 1988;Wang et al 2020), which is believed to be related to the five-minute p-mode wave (Thomas 1985;Bogdan 2000;Solanki 2003;Yuan 2015). Instead, sunspot oscillations in the middle solar atmosphere (chromosphere and transition regions) often have a typical period of around three minutes, which can also be observed at photospheric sunspots (Solanki et al 1996;Bogdan 2000;Yang et al 2017).…”

Estimating red noise in quasi-periodic signals with MCMC-based Bayesian

“…The oscillations are usually observed in integrated light curves from radio waveband, optical, extreme ultraviolet to X-rays. For example, quasi-periodic pulsation (QPP) in solar flares (Li et al 2015(Li et al , 2018Ning 2017;Yuan et al 2016), three-and five-minute oscillations in sunspots (Stangalini et al 2012;Su et al 2016;Wang et al 2018;Tian et al 2014;Yuan et al 2014;Wang et al 2020).…”

Quasi-periodic pulsation detected in Lyman-alpha emission during solar flares

“…To examine the QPP feature in these two flares, the fast Fourier transform method (see, Ning 2017) is performed to the original light curves to obtain the Fourier spectrum in GOES Ly-α and SXR channels, as shown in the panels (f) & (g) of Figures 1 and 2. In the astrophysical observations (Vaughan 2005;Pugh et al 2017;Wang et al 2020), the term 'red noise' is often described by a power-law model in the Fourier power spectrum at longer periods, i.e., P (T ) ∼ T θ , where T is the period, θ represents a slope in the log-log coordinate system. While a white noise often refers to the flat spectrum at the shorter-period end.…”