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Abstract:
The solar activity cycle is the root-cause of energetic particles and magnetic fields that can reach the Earth through interplanetary space and can create hazardous space weather. Current solar cycle 25 is in its ascending phase. Like all cycles, this one is progressing, not as a pure sinusoid, but in the form of a sequence of quasi-periodic bursts, followed by relatively quiet phases. This sequence is called the "seasons" of solar activity. Observations indicate the periods of these activity bursts are shorter in cycle 25 compared to cycles 23, 24, i.e., the "seasons" are faster in cycle 25 so far. TNO (Tachocline Nonlinear Oscillation) simulations have revealed that the TNOs, produced by nonlinear exchange of energies among Rossby waves, dynamo-generated magnetic fields and differential rotation in an MHD shallow-water model can lead to quasi-periodic enhanced activity-bursts, and also that the TNOs have shorter periods, for stronger toroidal magnetic fields. We will discuss the questions: (i) what can we expect cycle 25's strength to be? (ii) When will the next activity-burst occur? (iii) What are the patterns of global distribution of active regions in cycle 25? (iv) How are these patterns evolving? Are they evolving primarily in a systematic fashion, i.e., in the form of tight-fit toroids with low-longitudinal modes, or are they more complex, including major randomness? (iv) How are the active regions' distribution patterns evolving in the North compared to the South? We describe what we can infer about cycle 25 features from answers to these questions.
