Summer 2009 Issue

VHF Propagation

Solar Cycle 24 – Expectations

By Tomas Hood, NW7US

A helioseismic map of the solar interior. Tilted red-yellow bands trace solar jet streams. Black contours denote sunspot activity. When the jet streams reach a critical latitude around 22 degrees, sunspot activity intensifies. (Source: National Solar Observatory [NSO] in Tucson, Arizona)

How much credibility should we grant to the panel of solar researchers and scientists that again releases a speculative prediction of the new solar cycle (the 24th since accurate solar cycle records have been kept)? Panel chairman Doug Biesecker of the NOAA Space Weather Prediction Center states, “If our prediction is correct, solar Cycle 24 will have a peak sunspot number of 90, the lowest of any cycle since 1928 when solar Cycle 16 peaked at 78.”

NASA’s lead representative on the panel, Dr. Dean Pesnell of the Goddard Space Flight Center, adds, “It turns out that none of our models were totally correct.... The sun is behaving in an unexpected and very interesting way.”

What I find entertaining is the self-importance prevalent in the solar science community by both professional and some amateur participants. Pesnell states the obvious, “In our professional careers, we’ve never seen anything quite like it.”

Yes, how many solar cycles can one experience during one’s professional life? The average cycle lasts between 11 and 12 years. However, the sun is millions of years old. In my view, it is pretty arrogant to postulate that mankind has any real understanding of and handle on what the sun might do next. Pesnell, again: “Go ahead and mark your calendar for May 2013, but use a pencil.”

No one can postulate with any credibility just how intense the new cycle will be, because there’s no direct correlation between this solar minimum and any regular pattern of past minimums. In 2008 and 2009, the sun was quieter than during any period during the “Space Age” (again, a very short time of reference in relation to the millions of years of solar history). During the last two years we’ve seen low sunspot counts, weak solar wind, low solar irradiance, and a period without a significant solar flare.

If none of the models is totally correct, how are they making this current prediction with such dismal expectations? At this point, I’m not holding my breath in favor of supporting any of the predictions. With the slow, yet sure increase in solar activity during recent months as seen with the emergence of more frequent small sunspots (many of which are new cycle spots) and “proto-sunspots,” there is hope that the sun is finally awakening. Tiny but significant increases in solar radio emissions are being observed, as well. Further evidence that the sun is experiencing an increase in solar cycle activity is the “zonal flows” (enormous currents of plasma on the sun’s surface) that are gaining strength and slowly drifting toward the sun’s equator. All of these things are precursors of an awakening solar Cycle 24. The evidence is clear; we are seeing a real start of Cycle 24.

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