Temporal Evolution of the Rotation of the Interplanetary Magnetic Field Bx, By, and Bz Components

Abstract

Abstract The daily interplanetary magnetic field (IMF) B x , B y , and B z components from 1967 January 1 to 2018 December 31 listed in the OMNI database are used to investigate their periodicity and study temporal variation of their rotation cycle lengths through continuous wavelet transform, autocorrelation, and cross-correlation analyses. The dominant rotation period in each of the daily B x , B y , and B z components is 27.4 days, implying the existence of rotational modulation in the three time series. The dependence of the rotation cycle lengths for both B x and B y components on solar cycle phase almost shows the same result. The rotation cycle lengths for both B x and B y components increase from the start to the first year of a new Schwabe cycle, then decrease gradually from the first to the fourth year, and finally fluctuate around the 27.4-day period within a small amplitude from the fourth year to the end of the Schwabe solar cycle. For the B z component, its rotation cycle length does not show such a solar cycle variation. The significant periods in the variation of B x rotation are 2.9, 3.4, 4.3, 4.9, 10.5, and 11.9 yr, and there exist significant periods of 3.4, 9.9, and 14.1 yr in the variation of B y rotation. The relationship of solar activity with B x and B y components is complex. The possible mechanisms for the temporal variation of the rotation period of the three components are discussed.