Slow Magnetoacoustic Oscillations in Stellar Coronal Loops

Abstract

Slow magnetoacoustic oscillations in stellar coronal loops with gravitational stratification are analyzed with a numerical solution of the boundary value problem for eigenvalues and eigenfunctions. In this study, we only focus on the resonant periods. The effects of the gravitational stratification, star mass, loop temperature, and loop length on the properties of slow magnetoacoustic oscillations are investigated. It is shown that the discrepancy between stratified and nonstratified loops is higher in density perturbations than in velocity perturbations. When the star has a larger mass, higher coronal temperature, and longer loop, the density perturbations in the stratified loop are significantly different from the harmonic functions. The periods in the stratified loop are slightly longer than in the nonstratified loop. The periods calculated in our model (14–644 minutes) are consistent with the periods of stellar quasi-periodic pulsations observed in both soft X-rays (2–70 minutes) and white lights (8–390 minutes).

OSCILACIONES EN BUCLES MAGNÉTICOS DE LA CORONA SOLAR : Observaciones y Modelos Teóricos

“…Este tipo de oscilaciones fue detectado por primera ocasión mediante el instrumento SUMER en SOHO, que comúnmente se los denomina ondas SUMER, las cuales se las interpreta como modos magnetoacústicas lentos (Wang et al 2021). Se los nombra SUMER debido a dos condiciones, dados por: (1) el instrumento que fue utilizado para su detección (radiotelescopio SUMER) y (2) por el periodo, el cual es más largo que el tiempo de tránsito acústico a lo largo de un bucle, decayendo rápidamente con el tiempo de amortiguamiento sobre el periodo de os-Oscilaciones en Bucles Magnéticos de la Corona Solar cilación a lo que se conoce como oscilaciones de emisión térmica (Lim et al 2022).…”

Coronal seismology by slow waves in non-adiabatic conditions

“…The seismological applications of slow waves in the corona span from probing the absolute value of the magnetic field in active regions (e.g., Wang et al, 2007;Jess et al, 2016) and the magnetic field direction (Marsh et al, 2009) to estimating the effective adiabatic index of the coronal plasma (e.g., Van Doorsselaere et al, 2011;Wang et al, 2015;Krishna Prasad et al, 2018), its effective energy transport coefficients (Wang et al, 2015(Wang et al, , 2018, multithermal nature of coronal loops (e.g., King et al, 2003;Krishna Prasad et al, 2017), and even properties of the coronal heating function (Reale et al, 2019;Kolotkov et al, 2020). Moreover, a similarity between the properties of the phenomenon of quasi-periodic pulsations, observed in solar and stellar flare lightcurves and attributed to the modulation of the flare emission by slow waves, allowed for revealing new solar-stellar analogies (Cho et al, 2016) and stimulated the development of the theory of slow waves in stellar coronal conditions (e.g., Reale et al, 2018;Lim et al, 2022).…”