Asymmetry in the Rosenberg‐Coleman effect around solar minimum revealed by wavelet analysis of the interplanetary magnetic field polarity data (1927–2002)

Abstract

Interplanetary magnetic field (IMF) polarity data for the years 1927–2002 were studied by wavelet analysis technique, which permits the identification of non‐steady features in the IMF polarity data. It was found that the annual variation in the IMF polarity (the Rosenberg‐Coleman effect) is present only during the rise phase of solar cycles. This result is confirmed by the observed B x (radial) solar wind measurements since 1964. This asymmetry could be caused by a more stable and flat heliospheric current sheet being present only in the rise phase of solar cycles, with co‐rotating high speed streams disturbing it during the descending phases. This finding bears on the generally accepted explanation of the 22‐year geomagnetic activity cycle.