A statistical study of emerging active regions demonstrates that these ARs tend to produce CMEs when they accumulate significant budgets of both magnetic helicity and energy.
The authors show that the new inversion code for the HMI’s vector field reduces the number of pixels that reverse signs after passing the central meridian. The analysis also reveals that the radial components of the HMI’s vector magnetic fields have a hemispheric bias, too.
For weak magnetic regions, HMI’s vector magnetic fields are known to give ambiguous signs in the east-west direction. A new inversion strategy is developed to address this problem, and the follow-up analysis shows that the new code improves HMI’s weak vector magnetic fields.
Through analyzing a number of active regions, this analysis finds that while flares are guided by the physical properties that scale with AR size, CMEs are guided by mean properties, with little dependence on the amount of shear at the polarity inversion line or the net current.
This analysis shows that a new bipolar emergence, whose positive polarity collided with the pre-existing negative polarity, in AR11283 led to energy and helicity buildup in the form of magnetic flux ropes. Recurrent energy releases caused a few homologous CMEs from this region.
A segment of bald patch in AR 12673 disintegrated rapidly during solar cycle 24’s most intense flare. The horizontal magnetic field perpendicular to the polarity inversion line changed sign, while the parallel component permanently increased.
In order to make the properties of magnetic features observed by SDO/HMI more accessible, the Solar Photospheric Ephemeral and Active Region (SPEAR) catalogue has been created as an easy-to-read tabulated text file. Tilt angles from the SPEAR catalogue are shown as a histogram (top) and as a function of latitude (bottom) with colors indicating all regions (blue), regions with anti-Joy (red), and anti-Hale (purple) tilts. Over 40% of regions disobey the laws of Joy and Hale.
A time variable center-to-limb effect in photospheric velocity measurements through local correlation tracking is identified, and a robust methodology to correct for it is developed.
A statistical study of hundreds of solar flares, with or without CMEs associated with them, indicates the larger the total magnetic flux of the flare-host active region, the less likely the flare is associated with a CME.
Magnetic-field dependence of active regions’ tilt angles are analyzed using the MDI and HMI observations for two solar cycles. The variation of the tilt angles with the maximum magnetic-field strength of the ARs indicates a nonlinear tilt quenching in the Babcock–Leighton process.