Tag Archives: solar cycle

224. Moderate Nesting and Cross-Equatorial Asymmetry of Active Regions in Solar Cycle 24

Contributed by Aimee Norton. Posted on April 3, 2026

HMI data from Solar Cycle 24 data are used to determine how often the Sun emerges sunspots in activity nests. It is found that the Sun shows moderate nesting behavior with 41% (48%) of AR magnetic flux found in northern (southern) hemisphere located in nests. The maximum number of nests are found with slightly prograde rotational velocities, and the nesting behavior is asymmetric in the hemispheres.

199. Cycle 25: Timing of Polar field Reversal based on Advective Flux Transport Model

Contributed by Bibhuti Jha. Posted on March 29, 2024

The advective flux transport model, coupled with a random active region generator, predicts that the solar activity will peak in the northern hemisphere around August 2024, and peak in the southern hemisphere around February 2025.

196. Observations of Rossby wave parameter variations during solar cycle 24

Contributed by Mattias Waidele. Posted on September 25, 2023

Equatorial Rossby waves are detected using the HMI’s time-distance subsurface flow fields. It is also found that the power of the Rossby waves show a positive correlation with the sunspot number, while the frequency of the waves shows an anti-correlation with the sunspot number.

191. Explaining why all solar cycles rise differently but decay in the same way

Contributed by Bidya Karak. Posted on July 28, 2023

Magnetic flux loss from the solar interior due to flux emergence explains why all solar cycles decline in the same way.

169. The QBO-type signals in the Subsurface flow fields during solar cycles 23 and 24

Contributed by Fadil Inceoglu. Posted on November 3, 2021

Quasi-biennial oscillations are found in the Sun’s interior rotation-rate residuals. They appear differently at different depths and latitudes, and evolve with time.

149. Activity Complexes and a Prominent Poleward Surge During Solar Cycle 24

Contributed by Zi-Fan Wang. Posted on December 15, 2020

A surface flux-transport dynamo model assimilation shows that the long-lasting active-region complexes, which appeared in the Sun’s southern hemisphere during Cycle 24, played a crucial role in the pole’s polarity reversal and the field strength at the cycle minimum.

146. Prediction of Solar Cycle 25

Contributed by Leif Svalgaard. Posted on October 9, 2020

Using the solar axial magnetic dipole moment obtained prior to the solar minimum, the author predicts that the maximum sunspot number of Solar Cycle 25 is about 128.

128. Evolution of Magnetic Helicity in Solar Cycle 24

Contributed by V.V. Pipin. Posted on June 25, 2019

A novel approach is developed to reconstruct the surface magnetic helicity density for the Sun or sun-like stars. The method is applied on the SDO/HMI-observed vector field synoptic data to study the temporal evolution of the Sun’s magnetic helicity density during Solar Cycle 24.

118. Detection of Dynamo Waves inside the Sun

Contributed by Alexander G. Kosovichev. Posted on January 15, 2019

An analysis of zonal flow acceleration/deceleration inside the Sun reveals patterns of dynamo waves, and suggests that the primary seat of the dynamo is located in a high-latitude zone of the tachocline.

107. Cyclic Variations of the Sun’s Seismic Radius

Contributed by Alexander Kosovichev. Posted on July 30, 2018

The Sun’s seismic radius, measured from the frequencies of f modes, is determined using both MDI and HMI data, covering a total of 21 years. It is found that the seismic radius is reduced by 1-2 km during the maxima, but the largest change of the radius happens at about 5 Mm beneath the surface.