| Name: Soumya Mishra |
| Affiliation: NISER Bhubneshwar |
| Conference ID: ASI2026_906 |
| Title: Asymmetry in Sunspot Area Variation: Observational Evidence for Nonlinear Toroidal Flux Loss in the Solar Cycle |
| Abstract Type: Poster |
| Abstract Category: Sun, Solar System, Exoplanets, and Astrobiology |
| Author(s) and Co-Author(s) with Affiliation: Soumya Mishra(Niser Bhubhneshwar), Dr. Bidya Binay Karak(Indian Institute of Technology(BHU), Varanasi), Anu B Shreedevi(Indian Institute of Technology(BHU), Varanasi) |
| Abstract: Sunspots provide the most direct observational signature of the Sun’s toroidal magnetic field, generated and amplified by dynamo action within the convection zone. In this work, we analyze the statistical properties of sunspot group areas across the past 13 solar cycles (Cycles 12-24), complemented by Bipolar Magnetic Region (BMR) magnetic flux measurements for Cycles 23 and 24 derived from space-based line-of-sight magnetograms. Using a consistent phase separation into rising and declining intervals for each cycle, we compare area/flux distributions to test whether flux emergence leaves a systematic imprint on cycle evolution.We find a clear phase asymmetry: sunspot groups and BMRs are statistically larger and more flux-rich during the rising phase than during the declining phase. This indicates that the rising phase is, on average, more favorable for producing major active regions and therefore has a higher potential to drive severe space weather. Moreover, we show that the mean and median of the sunspot-area distribution during the rising phase correlate strongly with cycle strength, whereas the corresponding statistics during the declining phase are weakly dependent or effectively independent of cycle strength. This cycle-strength independence becomes most pronounced in the final three years of the decline, when activity belts from different cycles converge toward the equator along a common latitudinal trajectory.Taken together, these results provide observational support for nonlinear toroidal flux loss through flux emergence, offering a physical explanation for why solar cycles rise at different rates but decay in a broadly self-similar manner |
