Deciphering Solar Magnetic Activity: Spotting Solar Cycle 25

Share this story:
Friday, June 9, 2017

We present observational signatures of solar cycle 25 onset. Those signatures are visibly following a migratory path from high to low latitudes. They had starting points that are asymmetrically offset in each hemisphere at times that are 21-22 years after the corresponding, same polarity, activity bands of solar cycle 23 started their migration.

Comparing the evolution of the daily hemispheric sunspot number and a data-inspired representation of activity band polarity and migration image
Comparing the evolution of the daily hemispheric sunspot number (top) and a data-inspired representation of activity band polarity and migration (bottom). The top panel shows the variation of the daily sunspot number in the northern (red) and southern (blue) hemispheres while the total sunspot number is represented in black. The northern and southern hemispheric maxima are indicated as red and blue dashed vertical lines, respectively.

Those bands define the so-called "extended solar cycle." The four magnetic bands currently present in the system are approaching a mutually cancelling configuration, and solar minimum conditions are imminent. Further, using a tuned analysis of the daily band latitude-time diagnostics, we are able to utilize the longitudinal wave number (m=1) variation in the data to more clearly reveal the presence of the solar cycle 25 bands. This clarification illustrates that prevalently active longitudes (different in each hemisphere) exist at mid-latitudes presently, lasting many solar rotations, that can be used for detailed study over the next several years with instruments like the Spectrograph on IRIS, the Spectropolarimeter on Hinode, and, when they come online, similar instruments on the Daniel K. Inouye Solar Telescope (DKIST) as we watch those bands evolve following the cancellation of the solar cycle 24 activity bands at the equator late in 2019.

Organizations: