The frequency ratio between the spot cycle and flip-flop cycle appears to be different for binary components and single stars. In RS CVn-type stars exhibiting both types of cycles, flip-flops appear to occur at the frequency of the spot cycle, implying the flip-flop cycle to be twice as long as the spot cycle. In young dwarfs flip-flop cycles are 3 – 4 times shorter than the spot cycle.
The solar active longitudes also exhibit a flip-flop cycle. On the Sun major spot activity alternates the active longitudes in about 1 – 3 yr, which results in flip-flop cycles of 3.8 and 3.65 yr in the northern and southern hemispheres, respectively (Berdyugina and Usoskin, 2003). This is about 1/3 of the 11-yr sunspot cycle and agrees with the results obtained for young solar analogues. The difference between flip-flop cycle lengths in the north and south is significant and produces an oscillating effect in the north-south asymmetry on a century time scale.
|Star||Sp||Prot, d||Pspot, yr||Pff, yr||Reference|
|II Peg||K2 IV||0.8||3.4||3.8||6.7066||9.3|||
|IM Peg||K2 III||1.5||13.3||1.05||24.65||13|||
|EI Eri||G5 IV||1.5||3.4||13.3||1.9510||9.0|||
|HR 7275||K2 IV||1||8||0.90||28.263||17.5|||
|HR 1099||K1 IV||9.2||2.841|||
|HD 37824||K0 III||2.0||12.6||0.5||53.12||13.5|||
|HD 181809||K0 III-IV||1.7||6.5||0.4||59.85||4|||
|LQ Hya||K2 V||0.7||0.8||16.3||1.601||15||5.2|||
|AB Dor||K0 V||0.8||0.8||50.5||0.515||20||5.5|||
|EK Dra||G1 V||1||1||10.0||2.606||10.5||4.5|||
|FK Com||G5 III||1.5||10||10.8||2.400||13/30||6.4|||
© Max Planck Society and the author(s)