Correlation of the Radial and Meridional Components of IMF and the Solar Wind Velocity: Dependence on the Time and the Fluctuation Frequency

Abstract

The behavior of the correlation between the radial BR and normal BN components of the interplanetary magnetic field (IMF) in the dependence on the time, the flow type of the solar wind, and the frequency of fluctuations has been studied with consideration of the peculiarities in IMF sectors of different signs. Based on the data of the Wind spacecraft obtained in 1995−2011, it has been found that the correlation between BR and BN is strongest in the periods of the solar activity minima and that the annual averages of the correlation coefficient obey the rules CRN > 0 or CRN < 0 northward or southward of the heliospheric current sheet, respectively. During the solar cycle, the correlation coefficient changes almost similarly in slow and fast solar wind streams. The dependence of the correlation between BR and BN on the fluctuation frequency was analyzed in a range of 1.2 × 10−5 to 8.3 × 10−3 Hz; it has been found that the correlation is maximal at low frequencies and that it slowly decreases, starting from 10−4 Hz, with increases in the frequency. It has been also found that, fluctuations in the components of the solar wind velocity VR and VN correlate analogously to the IMP components BR and BN at frequencies around 10−4 Hz or higher.