Author Archives: admin

189. Spatial Scales and Time Variation of Solar Subsurface Convection

Contributed by Alexander Getling. Posted on October 31, 2022

Spectral analysis of the spatial structure of solar subphotospheric convection is carried out for subsurface flow maps. It is found that the horizontal flow scales increase rapidly with depth, from supergranulation to giant-cell values. The total power of the convective flows is found to be anticorrelated with the sunspot number variation over the solar activity cycle in shallow subsurface layers and positively correlated at larger depths.

188. Constraining Global Solar Models through Helioseismic Analysis

Contributed by Andrey Stejko. Posted on October 28, 2022

Forward modeling is applied to numerous global hydrodynamic solar models, and helioseismic measurements on the meridional circulation are made using the forward modeling results. Comparison against the observational measurements shows significant differences, indicating our insufficient knowledge on either the global hydrodynamic modeling or the helioseismic inversions.

187. Precursor Identification for Strong Flares Based on Anomaly Detection Algorithm

Contributed by Jingjing Wang. Posted on October 21, 2022

Some magnetic features in active regions, related to strong solar flares, are considered as “anomaly” features in a machine learning algorithm. An unsupervised auto-encoder network has been trained to identify such anomalies and is used to predict occurrence of strong flares.

186. Solar-Cycle Variation of quiet-Sun Magnetism and Surface Gravity Oscillation Mode

Contributed by Andreas Korpi-Lagg. Posted on October 17, 2022

Twelve years of HMI Dopplergram and magnetogram data have been used to uncover the solar cycle dependence of the magnetically quietest regions on the Sun and to reveal an enigmatic behavior of the surface-gravity wave energy contained in those regions.

184. Measuring the Compactness of Active Regions

Contributed by Kelvin Moresi. Posted on August 10, 2022

Compactness is one geometric property of a sunspot group that has not yet been systematically quantified. We calculate the compactness of a small sample of δ-spots and β-spots using a minimum bounding circle. On average, the δ-spots are found to be more than twice as compact as the β-spots.

183. Phase shifts measured in evanescent acoustic waves above the solar photosphere and their possible impacts on local helioseismology

Contributed by Junwei Zhao. Posted on July 31, 2022

Analysis on high-spectral resolution data shows that oscillations in the higher atmosphere lead those in the lower atmosphere by an order of 1 s when their frequencies are below about 3.0 mHz, and lags behind by about 1 s when their frequencies are above 3.0 mHz. These phase shifts in the evanescent waves pose great challenges to the interpretation of some local helioseismic measurements that involve data acquired at different atmospheric heights.

182. The magnetic topology of the inverse Evershed flow

Contributed by Avijeet Prasad. Posted on July 29, 2022

Inverse Evershed flow is derived from chromospheric observations. Coupling these flow with the non force-free model, the authors find that the flow is driven along magnetic field lines connecting network elements with the outer penumbra by a gas pressure difference.