Derivation of Toroid Patterns from Analysis of Magnetograms And Inferring Their Deep-origin
Abstract
We employ a novel optimization method based on Trust Region Reflective algorithm to derive magnetic toroids from surface magnetograms. Toroids obtained are combinations of Fourier modes (amplitudes and phases) with low longitudinal wavenumbers. After validating the method using synthetic data generated as random numbers along a specified toroid, we compute shapes and latitudinal-widths of toroids from magnetograms, usually requiring several m 's to minimize residuals. By comparing properties of these toroids with patterns produced in the bottom toroidal band undergoing MHD evolution in a 3D thin-shell shallow-water type model, we infer their deep origin at/near convention-zone's base or tachocline. A threshold field-strength is chosen to include all active regions in magnetograms for toroid derivation, while avoiding non-contributing weaker fields. Higher thresholds yield narrower toroids, with m = 1 dominant, implying that stronger active regions are erupting from the core of the toroids at bottom. We determine the spatio-temporal evolution of toroids by optimally weighting amplitudes and phases of each Fourier mode for a sequence of 5 Carrington Rotations (CRs) to get the best amplitude and phases for the middle CR in the sequence. Taking more than 5 causes 'smearing' or degradation of toroid structure. As an example case, we analyze 'Halloween' storms toroids, and describe the features that might have caused the series of space weather events in October-November of 2003. We compare features of these toroids with analogous patterns derived from model-output. To find similarities/differences in toroids for different major space weather events, we will analyze long-term magnetograms for several solar cycles.
- Publication:
-
AGU Fall Meeting Abstracts
- Pub Date:
- December 2020
- Bibcode:
- 2020AGUFMSH0020013C
- Keywords:
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- 7522 Helioseismology;
- SOLAR PHYSICS;
- ASTROPHYSICS;
- AND ASTRONOMY;
- 7524 Magnetic fields;
- SOLAR PHYSICS;
- ASTROPHYSICS;
- AND ASTRONOMY;
- 7536 Solar activity cycle;
- SOLAR PHYSICS;
- ASTROPHYSICS;
- AND ASTRONOMY;
- 7924 Forecasting;
- SPACE WEATHER