Abstract Details


Name: Rambahadur Gupta
Affiliation: Indian Institute of Technology (BHU) Varanasi
Conference ID: TVS202510198
Title: A statistical study of large Ephemeral Regions through HMI magnetograms
Authors and Co-Authors: Anu Sreedevi, Bidya Binay Karak, Bibhuti Kumar Jha
Abstract Type: Contributory Presentation
Abstract: Ephemeral Regions (ERs) are small, short-lived bipolar magnetic structures that appear across the entire solar disk on the photosphere and persist throughout the solar cycle. The reported magnetic flux of ERs varies across the literature, with a commonly used definition placing it between 10^19 Mx to 4.7 × 10²⁰ Mx (Harvey, 1973). ERs are thought to play a critical role in terms of the flux budget of the Sun and coronal heating. In this study, we use the AutoTAB catalog, which tracks the evolutionary properties of BMRs. From this dataset, we isolate ERs by applying an upper threshold of 3 × 10²⁰ Mx in the total flux and 1.2 days in the average tracked lifetime of the bipolar regions (Sreedevi et al. 2023). We find that the ER tilt shows a Gaussian distribution of mean of 7 deg and a considerable scatter around the mean. We also find that the tilt angles follow a weak Joy’s law trend. These nonzero tilt suggest a significant contribution of ERs in the generation of the polar field and in general the global solar dynamo, particularly during the extended grand minimum when the Sun produces only a few big active regions. Our results further suggest that with better data, we are in a position for a refined categorisation of ERs.