Conveners
1.2 Long-term evolution of the global structure of solar magnetic fields (chair Theo Chatzistergios)
- Theodosios Chatzistergos (Max Planck Institute for Solar System Research, DE)
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Dr Adam Finley (ESA, NL)09/06/2026, 14:00Invited review
The magnetic activity of stars like the Sun is driven by the interplay of rotation and convection that fuels dynamo-action in their interiors. At the surface, dynamo-generated magnetic fields emerge as "spots" or active regions that influence the circumstellar environment via winds, radiation, and transient events like flares and coronal mass ejections (collectively “space weather”). Flux...
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Dr Laure Lefevre (Royal Observatory of Belgium, BE)09/06/2026, 14:20Solicited
The Sunspot Number series, with its almost 420 years of data, is one of the longest and most detailed available series in astrophysics, it is produced and maintained at the World Data Center SILSO (https://sidc.be/SILSO/home). Since 2010, eJorts have been undertaken by the solar community to revise both the Sunspot Number and the Group Number series (SN and GN). After an extensive...
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Dr Alexei Pevtsov (US National Solar Observatory, US)09/06/2026, 14:40
This work continues revisiting the manual observations of magnetic fields in sunspots from 1917-2025. Observations from Mount Wilson Observatory, Potsdam, and Crimean Astrophysical Observatory are included. We review the methods of observations, describe observational setups, compare measurements, and discuss systematics. While we see a solar cycle variation in the amplitude of strongest...
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Dr Marianna Korsos (University of Sheffield, UK)09/06/2026, 14:52
We investigate the large-scale longitudinal and hemispheric organization of solar magnetic activity across multiple solar cycles, including Cycles 23, 24, and the ongoing Cycle 25. Using synoptic magnetic maps and flare catalogues, we examine the relationship between active longitudes, the spatial distribution of magnetically complex active regions, and the preferred longitudes of the most...
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Prof. Eckhard Weisshaar (U. of Applied Sciences, Wiesbaden, DE)09/06/2026, 15:04Solicited
$^{14}$C measurements from tree rings have been used by Usoskin et al. (2021, 2025, 2026) to reconstruct past solar activity cycles over three millenia from the year 1000 BCE onward. In Weisshaar et al. (2023, A&A 671, A87) we analysed a first data set covering the epochs of reconstructed activity minima and maxima of the reconstructed cycles between 971 and 1900 CE in order to determine...
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Dr Ismo Tähtinen (Oulu U., FI)09/06/2026, 15:19
We present a novel method for quantifying the eect that individual active regions have on the large-scale solar magnetic field as their magnetic flux spreads across the photosphere. This is achieved by combining the surface flux transport (SFT) model with a recent vector sum method.
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We simulated the evolution of individual active regions of solar cycle 24 with the SFT model and used the... -
Ms Srinjana Routh (ARIES, IN)
Accurately measuring the Sun’s polar magnetic fields remains a challenge, whether using Earth-based telescopes or spacecraft operating near the ecliptic plane. Among various indicators, the strength of polar fields at the sunspot cycle minimum, representing the radial component of the poloidal magnetic field, has proven to be the most robust predictor of the toroidal component and thus the...
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