2018/08/12 by Bidya Binay Karak, Sudip Mandal, Dipankar Banerjee · 55 citations
Physics and Astronomy · #Astronomy and Astrophysical Research #Dynamo #Field (mathematics) #Magnetic field #Polar #Scientific Research and Discoveries #Solar and Space Plasma Dynamics #Solar cycle #Solar dynamo #Sunspot #Toroid #astro-ph.EP #astro-ph.IM #astro-ph.SR
paper · pdf · doi:10.3847/1538-4357/aada0d
published in The Astrophysical Journal 866(1), 17 (IOP Publishing) · 12 pages including 5 figures. Accepted in ApJ
arxiv created 2018/08/12 · openalex created_date 2018/08/22 · openalex publication_date 2018/10/05 · arxiv updated 2018/10/11 · openalex updated_date 2026/08/05
Abstract One peculiar feature of the solar cycle that is yet to be understood properly is the frequent occurrence of double peaks (also known as the Gnevyshev peaks). The double peaks, and also multiple peaks and spikes, are often observed in any phase of the cycle. We propose that these peaks and spikes are generated due to fluctuations in the Babcock–Leighton process (the poloidal field generation from tilted bipolar magnetic regions). When the polar field develops, large negative fluctuations in the Babcock–Leighton process can reduce the net polar field abruptly. As these fluctuations in the polar field are propagated to the new toroidal field, these can promote double peaks in the next solar cycle. When fluctuations in the polar field occur outside the solar maximum, we observe their effects as spikes or dips in the following sunspot cycle. Using an axisymmetric Babcock–Leighton dynamo model, we first demonstrate this idea. Later, we perform a long simulation by including random scatter in the poloidal field generation process and successfully reproduce the double-peaked solar cycles. These results are robust under reasonable changes in the model parameters, as long as the diffusivity is not too much larger than 10 12 cm 2 s −1 . Finally, we analyze the observed polar field data to show a close connection between the short-term fluctuations in the polar field and the double peaks/spikes in the next cycle. Thereby, this supports our theoretical idea that the fluctuations in the Babcock–Leighton process can be responsible for the double peaks/spikes in the observed solar cycle.