Correção de efeito sistemático causado pelo movimento relativo do polo solar em observações de modos de pressão (p) no limbo

Abstract

Like geoseismology, the helioseismology makes it possible to obtain information from inside the body under study, where it is not likely to send probes. In the case of the Sun, the simplest model takes into account only pressure and gravity as mechanisms for equilibrium, which is known as hydrostatic equilibrium for a spherical body. The equations perturbation from this model reveals that resonant oscillation in the solar interior is possible and splits into p and g modes. The p modes have pressure as a restoring force, while the g modes have gravity. The most accurate instrument for helioseismology measurements today is the Helioseismic Magnetic Imager (HMI) onboard the Solar Dynamics Observatory (SDO). One way to observe the modes is by analyzing the Fourier transform of the temporal luminosity profile through the limb obtained from the instrument’s filtergrams, making use of the data series limbfit. The modes in these limb data suffer from a higher dispersion due to the effect of the B0 angle movement that the solar disk performs from the Earth’s point of view. In this work, we analyze how this correction can improve the signal/noise ratio of the modes by adjusting the limbfit data with a correction applied. We used routines developed in IDL (Interactive Data Language) to calculate the Fourier transformation and data interpolation, and the values of B0 are obtained by cross-correlation and adjusted on the software Period04. The adjustment of the lag sine function between the diagrams exhibits an amplitude of 6.93 ± 0.05º, while the nominal value is around 7.2º. The correction of the measured B0 was developed as well as the routines to get the fitting parameters to the data so we could compare the way the modes in data were affected by compensation of B0 shift.