Speaker
Description
First Name: Stanislav
Last Name: Gunar
Affiliation: Astronomical Institute, Czech Academy of Sciences
All Authors: TEI Akiko, GUNAR Stanislav, OKAMOTO Takenori J., YOSHIDA Minami, KATSUKAWA Yukio
Abstract: The solar polar regions are of great interest because they are where magnetic reversals occur and the solar wind originates. Thus, a better understanding of the properties of the solar polar atmosphere and their cyclical variations is a subject of renewed interest. In this work, we investigate variations in the polar chromosphere and spicules with the solar cycle. We also study the asymmetry between the north and south poles. To do so, we utilize, for the first time, the unique 11-year-long data set of high-resolution chromospheric Mg II h and k spectra obtained at the north and south poles by the Interface Region Imaging Spectrograph (IRIS) during 2014–2025, with a nearly weekly cadence. We used the dataset to investigate temporal variations in the Mg II h and k line properties as a function of height above the limb. Our results for the first time show the presence of solar-cycle variation and its north-south asymmetry in the Mg II profiles. The variations are apparent in the integrated intensity and width of the Mg II k line, and the ratio of the integrated intensities of the Mg II k and h lines. Additionally, we for the first time detected strong correlations (or anticorrelations) between studied chromospheric indicators (the spicule height, the maximum width of the k line, and the altitude where the Mg II k line reaches the maximum width) and various indicators of the solar cycle (the sunspot number, the polar mean magnetic field, and the polar coronal intensity for both northern and southern poles).