Does the Time Resolution of the Geoeffective IMF Component Influence Its Annual, Semiannual and Diurnal Patterns?

Abstract

The geoeffective interplanetary magnetic field (IMF) component \(B_{\mathrm{s}}\), \(B_{\mathrm{s}} = B_{z, {\mathrm{GSM}}}\) when \(B_{z, {\mathrm{GSM}}}<0\), is the most commonly used at 1-hour resolution for studying solar wind–magnetosphere coupling. In this way, the fluctuation of both \(B_{z,\mathrm{GSM}}\) (and thus \(B_{\mathrm{s}}\)) and IMF polarity within the hour are not taken into account. We investigate whether the global patterns of \(B_{\mathrm{s}}\) and \(B_{\mathrm{s}}\) sorted by IMF polarity (\(B_{\mathrm{s}}\) fields) change when these fluctuations are considered with respect to those based on hourly data. We have obtained \(B_{\mathrm{s}}\) fields at the high 16-second resolution. In this way, the information about the existence of \(B_{\mathrm{s}}\) fields within an hour is retained. The present study has shown that the initial resolution of the IMF data used to obtain \(B_{\mathrm{s}}\) fields (16-seconds or 1-hour) does not affect their characteristic patterns: diurnal, annual, and semiannual variations. Regardless of the initial IMF resolution, the \(B_{\mathrm{s}}\) sorted by the IMF polarity exists in all seasons. They show the two annual sinusoidal-like variations of opposite phase, the “pair of spectacles” pattern. The initial resolution affects only slightly the absolute values of \(B_{\mathrm{s}}\) fields. The results have shown that hourly values of IMF data are suitable for studying their global behavior within the year and also for investigating their relationship with magnetospheric quantities.