Abstract Details
| Name: Chitradeep Saha Affiliation: Center of Excellence in Space Sciences India, IISER Kolkata Conference ID: ASI2024_518 Title : Origin of supermodulation in solar magnetic activity Authors and Co-Authors : Chitradeep Saha1, Suprabha Mukhopadhyay1,2, Dibyendu Nandy1,2 Abstract Type : Oral Abstract Category : Sun, Solar System, Exoplanets, and Astrobiology Abstract : Direct sunspot observations and indirect cosmogenic isotope based reconstructions of solar activity exhibit variabilities well beyond the decadal solar cycle timescale – a phenomenon termed as supermodulation. These long-term solar activity proxies point to the existence of quasiperiodic variabilities in solar activity, including the centennial Gleissberg cycle, the 200-year Suess or de Vries cycle, the 2400-year Hallstatt cycle, etc. Whether such long term modulation in the Sun’s magnetic output results from nonlinear mechanisms or stochastic perturbations is a matter of intense debate. Based on multi-millennial scale solar dynamo simulations, we show that long-term modulation in solar activity is only excited in the presence of stochastic fluctuations. Our simulations conclusively demonstrate that invoking nonlinear quenching mechanisms alone – in the absence of any stochastic forcing in the dynamo framework – cannot produce statistically significant and persistent supermodulation in the sunspot cycle. |