Tag Archives: active regions

151. Hemispheric Sign Preference of Magnetic Helicity Flux in Solar Cycle 24

Contributed by Sung-Hong Park. Posted on January 26, 2021

To study the physical processes causing the hemispheric sign preference (HSP) of helicity in the Sun, the authors surveyed active regions (ARs) observed during Solar Cycle 24 to estimate their magnetic helicity flux, and studied the HSP dependences of the magnetic helicity flux with respect to various properties of ARs.

149. Activity Complexes and a Prominent Poleward Surge During Solar Cycle 24

Contributed by Zi-Fan Wang. Posted on December 15, 2020

A surface flux-transport dynamo model assimilation shows that the long-lasting active-region complexes, which appeared in the Sun’s southern hemisphere during Cycle 24, played a crucial role in the pole’s polarity reversal and the field strength at the cycle minimum.

147. Recurring Homologous Solar Eruptions in NOAA AR 11429

Contributed by Suman Dhakal. Posted on October 14, 2020

Through studying three homologous eruptive events in an active region, the authors conclude that shearing motions and magnetic flux cancellation play a dominant role leading to the recurrent eruptions, and are key processes forming the eruptive structures.

140. Solar Flare Predictive Features Derived from Polarity Inversion Line Masks in Active Regions Using an Unsupervised Machine Learning Algorithm

Contributed by Jingjing Wang. Posted on May 4, 2020

An unsupervised machine-learning algorithm is used on selected features derived from the polarity inversion lines (PIL) mask and difference PIL mask. It is found these features are effective in predicting flaring occurrences.

138. Electric Current Neutralization in Solar Active Regions and Its Relation to Eruptive Activity

Contributed by Ellis Avallone. Posted on March 11, 2020

Electric current neutralization, which measures the ratio of direct current and return current inside active regions (ARs), is studied for a total of 30 AR samples. It is found that flare-productive ARs are more likely to exhibit non-neutralized currents than those flare-quiet ARs.