2011/04/26 by Juan Hao, Mei Zhang · 1 citation
Physics and Astronomy · #Astro and Planetary Science #Astrophysics #Convection zone #Dynamo #Helicity #Magnetic field #Magnetic helicity #Particle physics #Physics #Quantum mechanics #Solar and Space Plasma Dynamics #Solar cycle #Solar wind #Stars #Stellar, planetary, and galactic studies #Sunspot #astro-ph.SR
paper · pdf · doi:10.1088/2041-8205/733/2/l27
accepted by ApJ Letters
arxiv created 2011/04/26 · openalex publication_date 2011/05/06 · arxiv updated 2015/05/28 · openalex created_date 2025/10/10 · openalex updated_date 2026/08/05
Using vector magnetograms obtained with the Spectro-polarimeter (SP) on board Hinode satellite, we studied two helicity parameters (local twist and current helicity) of 64 active regions that occurred in the descending phase of solar cycle 23 and the ascending phase of solar cycle 24. Our analysis gives the following results. (1) The 34 active regions of the solar cycle 24 follow the so-called hemispheric helicity rule, whereas the 30 active regions of the solar cycle 23 do not. (2) When combining all 64 active regions as one sample, they follow the hemispheric helicity sign rule as in most other observations. (3) Despite the so-far most accurate measurement of vector magnetic field given by SP/ Hinode , the rule is still weak with large scatters. (4) The data show evidence of different helicity signs between strong and weak fields, confirming previous result from a large sample of ground-based observations. (5) With two example sunspots we show that the helicity parameters change sign from the inner umbra to the outer penumbra, where the sign of penumbra agrees with the sign of the active region as a whole. From these results, we speculate that both the Σ-effect (turbulent convection) and the dynamo have contributed in the generation of helicity, whereas in both cases turbulence in the convection zone has played a significant role.