Tag Archives: active regions

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.

124. On Solar surface Electric field Estimation with 3 Poisson solvers (SEE3Po) for driving time-dependent MHD simulations of solar active regions

Contributed by Keiji Hayashi. Posted on April 28, 2019

An algorithm, which is to calculate the electric field in order to retrieve the time variations of solar surface magnetic field observed by HMI, was recently developed.

121. The Origin of Major Solar Activity: Collisional Shearing between Nonconjugated Polarities of Multiple Bipoles Emerging within Active Regions

Contributed by Georgios Chintzoglou. Posted on February 28, 2019

Magnetic flux of opposite polarities belonging to two different emerging/emerged bipoles inside multipolar magnetic regions, can experience “collisional shearing”, a process resulting in strong shearing and fast cancellation of magnetic flux near the polarity inversion line. This type of flux cancellation is found to be the cause of a succession of major flares and CMEs in complex active regions.

120. Magnetic Fields and the Supply of Low-Frequency Acoustic Waves to the Solar Chromosphere

Contributed by S. P. Rajaguru. Posted on February 27, 2019

Through analyzing simultaneous HMI’s visible-light observations and AIA’s ultraviolet observations, the authors show that a significant amount of acoustic waves with frequencies lower than the theoretical cutoff frequency can channel up along less inclined magnetic field from the photosphere to the chromosphere.

117. Evidence that Network Jetlets are Miniature Versions of Coronal Jets

Contributed by Navdeep Panesar. Posted on December 10, 2018

Observations of 10 coronal jetlets show that flux cancelation is usually a necessary condition for buildup and triggering of UV/EUV coronal network jetlets, and that network jetlets are plausibly small-scale versions of larger coronal jets.

114. What We Learned from a Long-term Study of Sunspot Physical Parameters

Contributed by Jing Li. Posted on November 20, 2018

Physical parameters, including sunspots tilt angles, total magnetic flux, polarity pole separations, and magnetic areas, are measured for most sunspot groups in solar cycles 23 and 24. Differences between Hale and anti-Hale sunspots in separate hemispheres and cycles are studied statistically.