Another new solar sunspot peak of 75.0 for Cycle 24 was set last month. It broke the old record of 73.2 set just a month earlier. A suddenly resurgent sun continues to confound the experts.
It’s poetic justice the new solar maximum is exactly 75. Solar physicists Leif Svalgaard, Edward W. Cliver, and Yohsuke Kamide bravely predicted solar maximum at 75±8 in 2004. They called it “potentially the smallest cycle in the last 100 years”. At the time, no one believed them.
Back in 2004 most solar physicists, led by NASA’s James Hathaway, thought solar max would beat out last cycle by a country mile, getting to over 140. They were very wrong.
Svalgaard, et al., used a new physics-based approach to forecasting solar max. Before that others used statistical methods based mostly on past solar behavior.
For the second month in a row, the sunspot number dropped while the sunspot peak rose to a record high for the cycle. It’s an artifact of calculating solar maximum as a 13-month smoothed average.
Another solar maximum record is likely again this month even if the monthly sunspot number goes down again. Solar maximum could get over 80 before all is said and done.
The continuing story is how much larger the secondary sunspot peak is than the first. Secondary peaks larger than the first are rare in the 400-year sunspot record. This one is already the largest increase ever.
SILSO data, Royal Observatory of Belgium, Brussels: New solar maximum set in April
On May 1st, The Royal Observatory of Belgium released the official sunspot number for April. April dropped to a daily average of 84.7 spots. It’s down over 18 spots/day from the 102.8 monthly high set in February.
The Royal Observatory has been known as SIDC for the last 32 years. It’s transitioning to a new name, SILSO, to reflect expansion into new solar data collections over the years. SILSO stands for “Sunspot Index and Long-term Solar Observations”.
Other sun news from last month
NASA Goddard released this video of a medium sized M6.5 class solar flare that occurred on April 2, 2014.
Two reports came out last month on the subject of sunspots that appear slightly at odds with each other. Christoph Kiess, Reza Rezaei and Wolfgang Schmidt from the Kiepenheuer-Institut für Sonnenphysik (KIS) present data showing the general characteristics of sunspots this cycle are no different than Cycle 23.
On the other hand, Fraser Watson at the U.S. National Solar Observatory (NRO) presents a chart in support of NRO colleagues Penn and Livingston showing there is a general decline in umbral magnetic field strength, but that it is now leveling off. Watson also explains earlier measurement discrepancies between two sources.
The amount of decline in umbral field strength is a major puzzle piece indicating we may be headed toward a long-term lull in solar activity. If the decline is not as fast or low as previously believed then solar activity may not decline to near zero, as many now think. That has long-term climate change implications, too.
The biggest news in solar physics isn’t what happened on the sun last month. The biggest news is what is going to happen on earth this month.
The 4th and final Sunspot Number Workshop examining the 400-year long record of daily sunspot counts will be held this month. The expected outcome is a finalized revision of the record correcting for errors that have accumulated in it over the centuries. The workshops started in 2011.
The 400-year daily sunspot count is the longest continuously maintained scientific measurement in the world. Changing it affects conclusions drawn in thousands of papers written over several centuries, including those in the “settled science” of climate change.