Speaker
Bidya Binay Karak
(Department of Physics, Indian Institute of Science, Bangalore)
Description
One of the most striking aspects of the sunspot cycle is that there have been times
in the past when sunspots did not appear for several years and a few cycles went
missing. A most well-known example of this is the Maunder minimum during 1645-1715.
Although reliable sunspot data did not exist before 1611, several indirect studies
(C14 data from old tree rings and the Be10 data from polar ice) indicate that there
have been several grand minima in the last. Moreover there are evidences that some
solar-like stars show grand minima. We address the question how grand minima are
produced and calculate the frequency of occurrences of grand minima using a flux
transport dynamo model. This model is basically a mean-field kinematic dynamo model
where the poloidal field generation is not due to the traditional (helical) alpha
effect rather due to the Babcock–Leighton mechanism operating near the surface. We
show that if the poloidal
field or the meridional circulation become sufficiently weak in this model, then
that can trigger the dynamo into a grand minima like event. From the observational
data of last 28 solar cycles, we calculate the level of the fluctuations of the
poloidal field and the meridional circulation and then with these fluctuations we are
able to model many aspects of grand minima including its frequency of occurrence.
Primary authors
Arnab Rai Choudhuri
(Department of Physics, Indian Institute of Science, Bangalore)
Bidya Binay Karak
(Department of Physics, Indian Institute of Science, Bangalore)
