A little over 2 months ago, I wrote about the extended lack of spots on the sun (The Sun Has Lost Its Spots).
The sun has remained essentially spotless since then and has been blank 87% of 2009 through April 4th. In 2008, the sun was blank 266 out 366 days (73%) and was the blankest year since 1913.
We are currently in the solar minimum phase of the solar cycle — the part of the cycle where the fewest sunspots appear. A typical solar minimum is 485 days. The current solar minimum is 594 days and counting.
A typical solar cycle is about 11 years in length, with lengths since 1900 varying from 9.8 years to over 12 years. The current solar cycle length, which began in May 1996, is approaching 13 years, though several years ago the end had been projected for Spring of 2007. According to sunspot expert Dean Pesnell of the Goddard Space Flight Center, “We’re experiencing a very deep solar minimum.”
NASA has taken an interest in the current solar minimum and has solicited proposals “to study the causes and consequences of the minimum of Solar Cycle 23.” Scientists intending to propose a study have to let NASA know of their intent by April 17th and their proposals must be submitted by June 5th.
Besides a dearth of sunspots, other solar indicators are also much lower than normal.
- Measured by instruments on satellites, the solar wind is 20% below what it was in the 1990s and is at the lowest point since solar wind measurements began in the 1960s.
- Measurements of solar irradiance by other satellites indicate the sun’s brightness has dropped by 0.02% in visible light and 6% in extreme ultraviolet wavelengths – a 12 year low.
- The sun’s radio emissions, measured by radio telescopes, are the lowest since 1955.
The sun is the source of the energy that warms Earth and likely has a significant impact on climate and climate change.
What happens when the solar indicators remain low for an extended period of time?