175. Solving a long-standing problem with the HMI data products

Contributed by Ana Griñón-Marín. Posted on March 21, 2022

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.

174. Toward Improved Understanding of Magnetic Fields Participating in Solar Flares: Statistical Analysis of Magnetic Fields within Flare Ribbons

Contributed by Maria Kazachenko. Posted on February 24, 2022

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.

173. Buildup of the Magnetic Flux Ropes in Homologous Solar Eruptions

Contributed by Rui Wang. Posted on February 17, 2022

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.

171. Flare-induced Sunquake Signatures in the Ultraviolet as Observed by the Atmospheric Imaging Assembly

Contributed by Sean Quinn. Posted on November 23, 2021

Sunquakes are helioseismic waves excited by solar flares, usually observed in the photosphere. However, some of these events are found to have their counterparts in the chromosphere, as observed in the SDO/AIA UV channels.

170. Solar Toroidal Field Evolution Spanning Four Sunspot Cycles Seen By WSO, SOHO/MDI, and SDO/HMI

Contributed by Allison L. Liu. Posted on November 19, 2021

The Sun’s toroidal field is derived using 45 years of Wilcox Solar Observatory data, 16 years of Michelson Doppler Imager data, and 11 years of Helioseismic and Magnetic Imager data. The duration of each cycle in both hemispheres is also estimated.

168. Introducing the SPEAR Catalogue from HMI Data

Contributed by Aimee Norton. Posted on October 29, 2021

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.

167. White-light Continuum Observation of the Off-limb Loops of the SOL2017-09-10 X8.2 Flare: Temporal and Spatial Variations

Contributed by Junwei Zhao. Posted on October 28, 2021

An unprecedented observation of a limb flare in HMI’s white-light continuum shows that the white-light intensity at the post-flare loop-top continues to grow for 16 more minutes while UV/EUV intensities decay. Both the WL/UV intensity and the EUV intensities show quasi-periodic pulsations with a period close to 8.0 and 6.8 minutes, respectively.

166. One-Sided Arc Averaging Geometries in Time-Distance Local Helioseismology

Contributed by David Korda. Posted on October 25, 2021

Instead of the center-annulus measurement geometry that time-distance helioseismology typically uses, a new one-sided center-arc measurement scheme is developed. This method shows advantage in measuring subsurface flows in in a close neighborhood of magnetic regions.