32. The Polar Field Reversal of Solar Cycle 24
HMI observations reveal a slow, north-south asymmetric polar magnetic field reversal. Cycle 24 has been weak; an even weaker Cycle 25 seems probable.
Category Archives: Magnetic Field
31. The Photospheric Size-Flux Distribution and its Relationship with the Small-Scale and Global Components of the Solar Dynamo
Taking advantage of 11 different databases, we use statistical analysis to probe the nature of photospheric magnetic structures. We find evidence of two separate mechanisms at play, and propose that they are directly connected to the global and small-scale components of the solar dynamo.
30. Surface and Coronal Field Signatures of Implosions in Two Homologous Solar Flares
By synthesizing the results of photospheric field change indicated by HMI observations and coronal field variation suggested by the NLFFF modeling, we study the flare-related 3D magnetic restructuring and find it consistent with the coronal implosion scenario in the low solar atmosphere.
29. The STARA Sunspot Catalog
The STARA catalog of sunspot properties from the SOHO/MDI and SDO/HMI data is presented and discussed. For STARA, an automated detection algorithm is employed to compile the first sunspot record from space-based instruments. This catalog is publicly available at http://www.nso.edu/staff/fwatson/STARA.
25. Solar Flare Forecasting Using HMI Vector Magnetic Field Data with a Support Vector Machine Algorithm
We attempt to forecast M- and X-class solar flares using a support vector machine algorithm and 4 years of HMI vector magnetic field data. With the true skill statistic as the preferred metric to estimate the algorithm performances, we obtain good predictive abilities. This may be partly due to fine-tuning the algorithm for this purpose, and to a choice of 13 SHARP parameters obtained from vector magnetograms.
23. Active Regions with Superpenumbral Whirls or Sunspots Like Pinwheels
The magnetic field of active region NOAA 11092 shows a persistent counter-clockwise twist in the solar atmosphere from the photosphere to the corona. The subsurface flows associated with this region are twisted in the opposite direction.
21. Three-ribbon Solar Flares: What Do They Imply for the 3D Magnetic Field Structure?
Combining the outstanding capability of HMI/SDO and NST/BBSO, we studied two rarely observed three-ribbon flares. The flaring site is characterized with an intriguing “fish-bone”-like morphology. These results are discussed in favor of reconnection along the coronal null-line.
20. Solar Meridional Flow in the Shallow Interior during the Rising Phase of Cycle 24
Subsurface meridional flow speed shows an anti-correlation with the magnetic flux being transported poleward above the latitude of 35°. In the lower latitude, the residual meridional flow, after a long-time mean profile is subtracted, shows converging flow toward the activity belts.
19. The CGEM Lorentz Force Data from HMI Vector Magnetograms
The Lorentz force acting on the solar atmosphere is useful for diagnosing the eruption dynamics. It is now available as a routine data product.
18. Correlations between sunspots and their moat flows
The statistical analysis of flow fields in and around sunspots indicates a distinct nature of the moat and Evershed flows.