41. The Cause of the Weak Solar Cycle 24
Surface flux transport model suggests that the weak Cycle 24 is mainly caused by a number of bigger bipolar regions emerging at low latitudes with a “wrong” north-south orientation.
Category Archives: Magnetic Field
39. Solar Cycle Variation of the Inter-Network Magnetic Field
Solar inter-network magnetic field, the weakest component of the solar magnetism, seems to be invariant at ~10 G from the minimum to the maximum phase of Cycle 24. This suggests a possible origin of small-scale, local dynamo.
38. Subsurface Structure of Pores and Sunspots
Numerical simulation of sunspots indicate that different subsurface structures are possible. They may be deep coherent flux tubes or twisted spaghetti or shallow structures. It may well be that all the models proposed for sunspot structures are correct for some spot somewhere.
37. Why is the Great Solar Active Region 12192 Flare-Rich but CME-Poor?
AR 12192 produced six X-class flares, but none was associated with a CME. HMI observations reveal the mild nature of the giant. It has weak relative non-potentiality and strong overlying field; the confined X3 flare leaves little imprint on the photosphere.
34. Bimodal Distribution of Magnetic Fields and Areas of Sunspots
Are all sunspots created equal or are some sunspots formed by a different mechanism than others? High quality observations from the Helioseismic Magnetic Imager (HMI) on board the Solar Dynamics Observatory (SDO) suggest bimodal distribution in properties of sunspots.
33. Comparing nonlinear force-free and potential field modeling using full-disk HMI data
We present potential filed and nonlinear force-free magnetic field (NLFFF) extrapolations of full-disk magnetogram observed by SDO/HMI instrument. The study shows that NLFFF model agrees significantly better with coronal magnetic loops as observed in SDO/AIA images.
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.
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.