Using 14 years of helioseismic and magnetic-field observations, this study shows that deeper subsurface outflows from active regions play an important role in transporting magnetic fluxes to the polar regions and regulating polar-field formation.
Helioseismic analysis of solar torsional oscillations reveals dynamo-wave–like signatures that originate near the tachocline and propagate through the convection zone, linking internal zonal flows to the surface magnetic cycle. Additional evidence from frequency-splitting coefficients and rotational shear variations shows strong solar-cycle correlations, supporting the tachocline as a primary site of solar dynamo action.
Multiple X-class flares and CMEs were produced by AR 13664/8 during the Mother’s Day week of 2024. This study suggests that predicting the locations of magnetically complex active regions, and studying and tracking their eruptive states using different proxy parameters can greatly improve the capability to forecast intense storms.
Is the solar meridional circulation profile single-, double-, or multiple-cell? At least, a constraint of equatorward angular momentum transport by meridional circulation favors the double-cell structure, although the inversion with a constraint of mass conservation favors single cell.
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.
Quasi-biennial oscillations are found in the Sun’s interior rotation-rate residuals. They appear differently at different depths and latitudes, and evolve with time.
In order to make the properties of magnetic features observed by SDO/HMI more accessible, the Solar Photospheric Ephemeral and Active Region (SPEAR) catalogue has been created as an easy-to-read tabulated text file. Tilt angles from the SPEAR catalogue are shown as a histogram (top) and as a function of latitude (bottom) with colors indicating all regions (blue), regions with anti-Joy (red), and anti-Hale (purple) tilts. Over 40% of regions disobey the laws of Joy and Hale.