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.
A statistical study of emerging active regions demonstrates that these ARs tend to produce CMEs when they accumulate significant budgets of both magnetic helicity and energy.
The authors show that the new inversion code for the HMI’s vector field reduces the number of pixels that reverse signs after passing the central meridian. The analysis also reveals that the radial components of the HMI’s vector magnetic fields have a hemispheric bias, too.
For weak magnetic regions, HMI’s vector magnetic fields are known to give ambiguous signs in the east-west direction. A new inversion strategy is developed to address this problem, and the follow-up analysis shows that the new code improves HMI’s weak vector magnetic fields.
Through analyzing a number of active regions, this analysis finds that while flares are guided by the physical properties that scale with AR size, CMEs are guided by mean properties, with little dependence on the amount of shear at the polarity inversion line or the net current.
This analysis shows that a new bipolar emergence, whose positive polarity collided with the pre-existing negative polarity, in AR11283 led to energy and helicity buildup in the form of magnetic flux ropes. Recurrent energy releases caused a few homologous CMEs from this region.
A segment of bald patch in AR 12673 disintegrated rapidly during solar cycle 24’s most intense flare. The horizontal magnetic field perpendicular to the polarity inversion line changed sign, while the parallel component permanently increased.
Sunquakes are helioseismic waves excited by solar flares, usually observed in the photosphere. However, some of these events are found to have their counterparts in the chromosphere, as observed in the SDO/AIA UV channels.
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.
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.