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.
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.
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.
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.
Contributed by Chia-Hsien Lin. Posted on August 17, 2022
This study reveals that a significant number of coronal-hole field lines extend beyond the coronal-hole boundaries and that many coronal-holes contain no open magnetic field lines.
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.
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.
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.
Contributed by Chris Hanson. Posted on June 27, 2022
High-frequency inertial waves were detected inside the Sun, propagating retrograde relative to the solar rotation with a phase speed faster than equatorial Rossby waves. How these waves are generated is discussed but remains unclear.
Contributed by Keiji Hayashi. Posted on May 30, 2022
Briefly shown here are some results from a new global coronal MHD simulation model, with a new method to use the three-component vector HMI synoptic maps as time-dependent boundary values.