Solar cycle 24

Solar cycle 24
ISES Solar Cycle 24 Sunspot Number Progression
Sunspot Data
Start date	January 4, 2008
Cycle chronology
Previous cycle	Solar cycle 23 (1996-2008)

Solar Cycle 24 is the 24th solar cycle since 1755, when extensive recording of solar sunspot activity began. It is the current solar cycle, and began on January 4, 2008, but there was minimal activity until early 2010. It is on track to be the smallest sunspot cycle in over a century.

Prior to the minima between the end of Solar Cycle 23 and the beginning of Solar Cycle 24, there were essentially two competing theories about how strong Solar Cycle 24 would be. The two camps could be distinguished by those postulating the Sun retained a long memory (Solar Cycle 24 would be active) or whether it had a short memory (Solar Cycle 24 would be quiet). Prior to 2006, the difference was very drastic with a minority set of researchers predicting "the smallest solar cycle in 100 years." Another group of researchers, including one at NASA, were predicting that it "looks like its going to be one of the most intense cycles since record-keeping began almost 400 years ago."

The delayed onset of high latitude spots indicating the start of Solar Cycle 24 led the "active cycle" researchers to revise their predictions downward and the consensus by 2007 was split 5-4 in favor of a smaller cycle. By 2012, consensus was a small cycle, as solar cycles are much more predictable 3 years after minima.

In May 2009 the NOAA/Space Weather Prediction Center's Solar Cycle 24 Prediction Panel predicted the cycle to peak at 90 sunspots in May 2013. In May 2012 NASA's expert David Hathaway predicted that current solar cycle would peak by the Spring of 2013 with about 60 sunspots.

NASA also directly funded and used Ken Schatten's physics-based models, which utilized a solar Dynamo model to accurately predict the low sunspot count in cycle 24. This method has used the correlation between solar magnetic field strength at solar minimum to sun spot number at solar maximum to accurately predict the peak solar flux of each of the last three solar cycles. Careful comparison of Schatten's predictions with those of Hathaway will demonstrate the superiority of Schatten's predictions: they are accurate as soon as solar minima 5–6 years before solar max.

In early 2013, after several months of calm, it was obvious that the active 2011 was not a prelude to a widely predicted late 2012-early 2013 peak in solar flares, sunspots and other activity. This unexpected stage prompted some scientists to propose a "double-peaked" solar maximum, which then occurred. The first peak reached 99 in 2011 and the second peak came in early 2014 at 101.

According to NASA, the intensity of geomagnetic storms during Solar Cycle 24 may be elevated in some areas where the Earth's magnetic field is weaker than expected. This fact was discovered by the THEMIS spacecraft in 2008. A 20-fold increase in particle counts that penetrate the Earth's magnetic field may be expected. Solar Cycle 24 has been the subject of various hypotheses and commentary pertaining to its potential effects on Earth.