Monthly Archives: October 2025

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.