Abstract Details
| Name: Krishna Kumar Pandey Affiliation: Department of Astrnomy, Osmania University, Hyderabad Conference ID: ASI2018_931 Title : Study of solar activity during solar cycles 21-23 Authors and Co-Authors : 1. K.M.Hiremath, 2. G. Yellaiah 1. Indian Institute of Astrophysics, Bangaluru,India. 2. Osmania University, Hyderabad, India Abstract Type : Thesis Abstract Category : Thesis Abstract : 1. Dynamics of the Sun, an episode of ~11 years solar cycle, drives the solar activity, space weather and near-Earth space environment which has a greatest impact on human civilization. Solar observations by space-borne instruments, have led ‘solar magnetic field and associated flare activity’ research in a new horizon to uncover, the evolution of solar magnetic/flare activity and, Solar cycle’s varying characteristic. One of the important features, newly emerged, as the Sun’s different latitude has vivid characteristics. Thus Sun needs to be studied in segments (North, South hemisphere, low and high latitude) and smaller zones of area like latitude strips of 0-50 or 0-100 to understand the intrinsic nature of solar atmospheric variations. Asymmetry/symmetry pattern, despaired butterfly wing and mysterious evolution of Gnevyshev gap are few more interesting subjects of this study. 2.We emphasize the comparison of the results with traditional solar activity indices. The variations in sunspot area have closest link with the transient energy release in the solar corona. The persistency of asymmetry significantly increases up to 13 Carrington rotations (Joshi et al., 2015). The time evolution of the soft x-ray flare activity confirms the evolution of dual peaks in Gnevyshev gap. The distinctness of the double-peak structure varies between different cycles and activity parameters. 3. We report an interesting indication, that the strength of asymmetry lowers at ~5-6CRs, ~12CRs, and ~18CRs (Pandey et al., 2016) related to Rieger type periodicities. This is conjectured as, while asymmetry evolves with phases of solar cycle, symmetry also emerges probably to counter the excess of asymmetry. The number of significant asymmetry points probably depends upon the solar heights. 4.We have investigated, during 1996–2008 the Solar Cycle 23, an unusually multi-structured maximum with anomalous N-S despaired butterfly wing diagram. Incremental pattern of latitudinal magnetic coupling between consecutive latitude suggested that the anomaly in Cycle 23 (Pandey et al., 2015) was due to M-class flare in southern wing. This anomaly may be considered as precursor of forth coming minima of a weakest solar cycle 24 in ~100 years. 5.We investigated the latitudinal evolution of Gnevyshev gap in different activity parameters and found that magnitude of Gnevyshev gap appears to be increasing and more resolved in the following order. Whole disc < solar atmospheric height < hemisphere < latitude < homogeneity class. On this basis, for the first time, we proposed the time interval determination between two or multiple peaks (Pandey et al., 2017) and reported the formation of Gnevyshev gap at high latitude activity also. This led to conclude that the end phase of low latitude (< 500) activity is linked with Gnevyshev gap formed at high latitude (> 500) activity. During Gnevyshev gap the high energy events are minimized where as very low energy events continue their occurrence. We conjectured that during this gap the activity energy is scattered and absorbed in empowering various functions. Different valley depth indicates the absorption of energy is selective and depends upon energy threshold. |