Origin and Characteristics of the Southward Component of the Interplanetary Magnetic Field

We investigate the rectified interplanetary magnetic field (IMF) components in two coordinate systems, GSEQ and GSM, focusing on the southward pointing component (Bs\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$B_{\text{s}}$\end{document}) in GSM within the period 1999 – 2017. The analysis is performed for different solar activity levels. The obtained results are valuable for the theoretical interpretation of IMF components variations and variations seen in geomagnetic indices. Bs\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$B_{\text{s}}$\end{document} ordered according to the polarity exhibits a “pair of spectacles” pattern. This reveals that Bs\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$B_{\text{s}}$\end{document} can also exist for toward/away field in fall/spring. The field is reduced, but it is not zero. Thus, in “unfavorable” seasons, geomagnetic activity can be due to reduced Bs\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$B_{\text{s}}$\end{document} and not because the field is northward pointing. We show that patterns of the experimental Bs\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$B_{\text{s}}$\end{document} fields are not in agreement with the Russell-McPherron model of Bs\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$B_{\text{s}}$\end{document} as widely assumed. The present study contributes in understanding the nature and behavior of Bs\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$B_{\text{s}}$\end{document}, which is the important element that controls the reconnection process and has a great influence on terrestrial space weather over the solar cycle.