Saved in:
| Main Authors: | , , |
|---|---|
| Format: | Preprint |
| Published: |
2023
|
| Subjects: | |
| Online Access: | https://arxiv.org/abs/2310.20171 |
| Tags: |
Add Tag
No Tags, Be the first to tag this record!
|
Table of Contents:
- Data from the Michelson Doppler Imager (MDI) and Helioseismic and Magnetic Imager (HMI) are analyzed from 1996 to 2023 to investigate tilt angles ($γ$) of bipolar magnetic regions and Joy's Law for Cycles 23, 24, and a portion of 25. The HMI radial magnetic field ($B_{r}$) and MDI magnetogram ($B_{los}$) data are used to calculate ($γ$) using the flux-weighted centroids of the positive and negative polarities. Each active region (AR) is only sampled once. The analysis includes only Beta ($β$)-class active regions since computing $γ$ of complex active regions is less meaningful. During the emergence of the ARs, we find that the average tilt angle ($\barγ$) increases from 3.30$^{\circ}\pm$0.75 when 20\% of the flux has emerged to 6.79$^{\circ}\pm$0.66 when the ARs are at their maximum flux. Cycle 24 had a larger average tilt $\barγ_{24}$=6.67$\pm$0.66 than Cycle 23, $\barγ_{23}$=5.11$\pm$0.61. No significant difference is found in the slope of Joy's law or $\barγ$ when sampling the ARs at the time of maximum flux or central meridian crossing. There are persistent differences in $\barγ$ in the hemispheres, with the southern hemisphere having higher ${\barγ}$ in Cycles 23 and 24, but the uncertainties are such that these differences are not statistically significant.