Category Archives: solar cycles

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.

204. Exploring Meridional Flow in the Solar Polar Caps

Contributed by Shuhong Yang. Posted on October 14, 2024

A surface flux transport model, using HMI-observed global magnetic field and active regions as inputs, with different polar meridional-flow profiles simulates the magnetic field in the polar caps. The simulation is then compared with Hinode-observed polar magnetic fields. The result supports an existence of counter cells above 70-degree latitude in each hemisphere.

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.

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.

178. Prediction based on the polar field rise rate suggests that Solar Cycle 25 will be slightly stronger than Cycle 24

Contributed by Bidya Karak. Posted on April 28, 2022

A new model, which explores the polar field build-up rate and the amplitude of the following cycle, predicts a slightly stronger Cycle 25 than previously thought.

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.

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.

112. A possible explanation of the double peaks in solar cycles

Contributed by Bidya Binay Karak. Posted on September 27, 2018

Through simulations using Babcock-Leighton flux transport model, it is found that the abrupt changes on the polar field near solar minimum could be the cause of the sunspot number double peaks in the next solar cycle.

109. How Many Active Regions Are Necessary to Predict the Solar Dipole Moment?

Contributed by Tim Whitbread. Posted on September 10, 2018

To assess the impact of active regions to the axial dipole moment, the authors isolate the contribution of individual regions for Cycles 21, 22, and 23 using a surface flux transport model, and find that although the top ~10% of contributors tend to define sudden large variations in the dipole moment, the cumulative contribution of many weaker regions cannot be ignored.

102. Solar magnetic cycle and its variability in a 3D Babcock-Leighton dynamo model

Contributed by Bidya Karak. Posted on June 7, 2018

Employing an updated Babcock–Leighton dynamo model, this study finds that the model with scattered tilt angles, which are around the Joy’s Law but with a standard deviation of 15°, is able to reproduce the observed variations of solar cycles.