A statistical comparison between HMI vector magnetograms and line-of-sight–derived radial fields shows that LOS-based estimates systematically underestimate the true radial field, with the bias increasing toward the limb. A numerical modeling demonstrate that this center-to-limb variation in the underestimation of radial field arises from non-radial magnetic field inclinations.
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.
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.
HMI now routinely produces vector magnetic field synoptic charts. This Nugget describes the data reduction procedures and the method chosen to resolve the 180-degree ambiguity in azimuth.
The HMI team has developed several Python codes that can be used to conveniently analyze its many magnetic field data products. Check it out!
The effect of the spatial resolution of the boundary data on nonlinear force-free extrapolations is systematically explored for a solar case.