223. Helioseismic evidence that the solar dynamo originates near the tachocline

Contributed by Krishnendu Mandal. Posted on February 26, 2026

Helioseismic analysis of solar torsional oscillations reveals dynamo-wave–like signatures that originate near the tachocline and propagate through the convection zone, linking internal zonal flows to the surface magnetic cycle. Additional evidence from frequency-splitting coefficients and rotational shear variations shows strong solar-cycle correlations, supporting the tachocline as a primary site of solar dynamo action.

222. On the Need for Rescaling Regular Synoptic Maps of the Solar Radial Magnetic Field

Contributed by Yang Liu. Posted on

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.

221. The Tilted Structure of Equatorial Rossby Waves Beneath the Solar Surface

Contributed by Oana Vesa. Posted on February 13, 2026

Equatorial Rossby waves at different depths are studied, and it is found that the Rossby waves are tilted retrograde with depth rather than being a columnar structure. The tilt remains relatively stable through the solar cycle without being consistently modulated by magnetic activity.

220. Stray Light Correction applied to HMI Data

Contributed by A.A. Norton. Posted on February 7, 2026

We report a point spread function (PSF) and deconvolution procedure to remove stray light from the Helioseismic and Magnetic Imager (HMI) data. The deconvolution uses a Richardson-Lucy algorithm and takes less than one second per full-disk image. In 2018, the HMI team began providing full-disk, stray-light-corrected data daily. The results, on average, show decreases in umbral continuum intensity, a doubling of the granulation intensity contrast, increases in the total field strength, most notably in plage by ∼1.4–2.5 the original value, and a partial correction for the convective blueshift.

219. SOHO/MDI and SDO/HMI Sunspot Area Measurement

Contributed by Peter Meadows. Posted on October 14, 2025

A robust, calibrated method for measuring sunspot areas from SOHO/MDI and SDO/HMI full-disk images enables a consistent, observer-independent, long-term catalogue of daily sunspot areas, revealing detailed patterns of sunspot group area evolution and solar cycle variability.

218. Reversal of Current Helicity Trend During Solar Eruptions

Contributed by Zheng Sun. Posted on October 13, 2025

Through MHD simulations of flux eruptions, the study finds that the current helicity decreases prior to eruptions and then reverses to increase afterward. By examining multiple flare events, the authors identified observational evidence supporting these simulation results.

217. Mother’s Day 2024 Superstorms: Tracing the Roots of Solar Eruptions Weeks Ahead

Contributed by Mausumi Dikpati. Posted on August 27, 2025

Multiple X-class flares and CMEs were produced by AR 13664/8 during the Mother’s Day week of 2024. This study suggests that predicting the locations of magnetically complex active regions, and studying and tracking their eruptive states using different proxy parameters can greatly improve the capability to forecast intense storms.

216. An “Average” Solar Active Region: Revealing Common Patterns in Magnetic and Flow Evolution

Contributed by Michal Švanda. Posted on August 17, 2025

Each solar active region (AR) has its unique shape, size, and lifetime. In this work, the authors developed a method to ‘average’ bipolar ARs by normalizing their size, orientation, and timing, thereby revealing the typical properties of an AR and its evolutionary pattern.

215. Quantifying Suppression of Solar Surface Magnetic Flux Advection with Increasing Field Strength

Contributed by V. Aparna. Posted on July 30, 2025

It is widely known that magnetic fields suppress convection, but this effect has not been quantitatively assessed. Using vector magnetograms from HMI observations, the authors measured the advection speeds of magnetic flux as a function of field strength and found that the speeds steadily decrease with increasing field strength.

214. Characterizing the Observational Properties of the Sun’s High-latitude m=1 Inertial Mode

Contributed by Boyang Ding. Posted on July 25, 2025

High-latitude m=1 inertial modes were analyzed and characterized using the time-distance helioseismic subsurface flows. It was found that the mode’s power exhibits an anti-correlation with solar activity. Magnetic flux transported from low to high latitudes influences both the mode’s power and lifetime, enhancing its power and shortening its lifetime upon arrival.