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Macroscopic wave and oscillatory phenomena ubiquitously detected in the plasma of the corona of the Sun are interpreted in terms of magnetohydrodynamic theory. Fast and slow magnetoacoustic waves are clearly distinguished in observations. Properties of coronal magnetohydrodynamic waves are determined by local parameters of the plasma, including the field-aligned filamentation typical for the corona. It makes coronal magnetohydrodynamic waves reliable probes of the coronal plasma structures by the method of magnetohydrodynamic seismology. For example, propagating slow waves indicate the local direction of the guiding magnetic field. Standing, sloshing and propagating slow waves can be used for probing the coronal heating function and the polytropic index. Kink oscillations of coronal plasma loops provide us with estimations of the absolute value of the magnetic field in oscillating plasma loops. This tutorial introduces several techniques of magnetohydrodynamic seismology of solar coronal plasmas. It includes the description of practical steps in the data acquisition, pre-processing, and processing using the open-access data of the Atmospheric Imaging Assembly on the Solar Dynamics Observatory spacecraft, and elaborated data analysis techniques of motion magnification and Bayesian statistics.
Macroscopic wave and oscillatory phenomena ubiquitously detected in the plasma of the corona of the Sun are interpreted in terms of magnetohydrodynamic theory. Fast and slow magnetoacoustic waves are clearly distinguished in observations. Properties of coronal magnetohydrodynamic waves are determined by local parameters of the plasma, including the field-aligned filamentation typical for the corona. It makes coronal magnetohydrodynamic waves reliable probes of the coronal plasma structures by the method of magnetohydrodynamic seismology. For example, propagating slow waves indicate the local direction of the guiding magnetic field. Standing, sloshing and propagating slow waves can be used for probing the coronal heating function and the polytropic index. Kink oscillations of coronal plasma loops provide us with estimations of the absolute value of the magnetic field in oscillating plasma loops. This tutorial introduces several techniques of magnetohydrodynamic seismology of solar coronal plasmas. It includes the description of practical steps in the data acquisition, pre-processing, and processing using the open-access data of the Atmospheric Imaging Assembly on the Solar Dynamics Observatory spacecraft, and elaborated data analysis techniques of motion magnification and Bayesian statistics.
We investigate the origin of very long-periodic pulsations in the white-light emission of an X6.4 flare on 2024 February 22 (SOL2024-02-22T22:08), which occurred at the edge of a sunspot group. The flare white-light fluxes reveal four successive and repetitive pulsations, which are simultaneously measured by the Helioseismic and Magnetic Imager and the White-light Solar Telescope. A quasi-period of 8.6 − 1.9 + 1.5 minutes, determined by the Morlet wavelet transform, is detected in the visible continuum channel. The modulation depth, which is defined as the ratio between the oscillatory amplitude and its long-term trend, is smaller than 0.1%, implying that the quasi-periodic pulsation (QPP) feature is a weak wave process. Imaging observations show that the X6.4 flare occurs near a sunspot group. Moreover, the white-light brightening is located in sunspot penumbra, and a similar quasi-period of about 8.5 − 1.8 + 1.6 minutes is identified in one penumbral location of the nearest sunspot. The map of Fourier power distribution suggests that a similar periodicity is universally existing in most parts of the penumbra that is close to the penumbral–photospheric boundary. Our observations support the scenario that the white-light QPP is probably modulated by the slow-mode magnetoacoustic gravity wave leaking from the sunspot penumbra.
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