The Quiet Sun

Today's Sun -- Spotless (Spaceweather.com)

Today's Sun -- Spotless (Spaceweather.com)

We’re now experiencing the most quiescent solar minimum in a century.

Sunspot counts last year were the lowest in more than 50 years. During 2009, we have experienced 81 days (87%) with no sunspots. Indeed, since 2004, there have been 592 days without sunspots, 107 more than the typical solar minimum of 485 days. Compared with the Solar Cycle 24 Predictions from NOAA’s Space Weather Prediction Center, which had projected an uptick beginning in March 2008, this cycle has been both deeper and longer than other recent sunspot minima. (For more on sunspot cycle prediction see this item from the Marshall Space Flight Center.)

There has been a 20 percent drop in the intensity of solar wind pressure since the mid 1990s. During this same period, the sun’s underlying magnetic field has also weakened by more than 30%. Solar irradiance in the extreme ultraviolet range has declined 6 percent since the solar minimum of 1996. And radio telescopes are recording the dimmest sun at radio wavelengths since 1955.

So, does all this suggest that there’s something terribly awry with the sun? Nope. See, for example, the discussion in NASA’s What’s Wrong With the Sun? (Nothing) from last July 11th.

For much more information on solar cycles, visit NASA’s Sunspot Cycle page among their Solar Physics web pages. You can find historical records for sunspot cycles with data going back to 1755 at Spaceweather.com’s
Sunspot Plotter (and incidentally check to see at what point in the solar cycle you were born).

For information on current and near term NASA explorations of the sun see NASA’s Solar Dynamics Observatory and the SOHO – Solar and Heliospheric Observatory pages, as well as (and especially) STEREO.

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Published in: on April 4, 2009 at 5:49 pm  Leave a Comment  

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