NOAA sunspot records from Cycles 22 to 24 reveal that the Sun’s north-south asymmetry is concentrated in activity nests. HMI observations show nesting tracks each hemisphere’s quasi-biennial oscillation and changes in the large-scale magnetic field.
The Solar Situation Awareness and Flare Forecasting Dataset provides 14 years of co-registered SDO/HMI, AIA, and Hα daily products with expert-reviewed active region, coronal hole, and filament annotations plus 24-hour flare labels, supporting AI-based forecasting.
HMI data from Solar Cycle 24 data are used to determine how often the Sun emerges sunspots in activity nests. It is found that the Sun shows moderate nesting behavior with 41% (48%) of AR magnetic flux found in northern (southern) hemisphere located in nests. The maximum number of nests are found with slightly prograde rotational velocities, and the nesting behavior is asymmetric in the hemispheres.
A surface flux transport model, using HMI-observed global magnetic field and active regions as inputs, with different polar meridional-flow profiles simulates the magnetic field in the polar caps. The simulation is then compared with Hinode-observed polar magnetic fields. The result supports an existence of counter cells above 70-degree latitude in each hemisphere.
The advective flux transport model, coupled with a random active region generator, predicts that the solar activity will peak in the northern hemisphere around August 2024, and peak in the southern hemisphere around February 2025.
Magnetic flux loss from the solar interior due to flux emergence explains why all solar cycles decline in the same way.
A new model, which explores the polar field build-up rate and the amplitude of the following cycle, predicts a slightly stronger Cycle 25 than previously thought.
The Sun’s toroidal field is derived using 45 years of Wilcox Solar Observatory data, 16 years of Michelson Doppler Imager data, and 11 years of Helioseismic and Magnetic Imager data. The duration of each cycle in both hemispheres is also estimated.
Using the solar axial magnetic dipole moment obtained prior to the solar minimum, the author predicts that the maximum sunspot number of Solar Cycle 25 is about 128.
Through simulations using Babcock-Leighton flux transport model, it is found that the abrupt changes on the polar field near solar minimum could be the cause of the sunspot number double peaks in the next solar cycle.