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 Previous: Life in Space Fun, Challenging, Astronaut Tells Pennsylvania Students |  Next: Hurricane Net, WX4NHC Continue Helping Forecasters Track Frances |
SEATTLE, WA, Sep 3, 2004--My thanks to Carl Luetzelschwab, K9LA, for doing an excellent job filling in for me last week. Sunspot numbers and solar flux values declined this week compared to last. The average daily sunspot number dropped by nearly 50 to 27.7, and the average daily solar flux was down more than 23 points. Geomagnetic activity increased on August 30 and 31, sparked by a moderate solar wind stream.
Returning Sunspot 649 has begun to transit across the solar surface. It has shrunk in size, but--along with returning Sunspot 656--is expected to increase sunspot numbers and solar flux over the near term. Solar flux is rising, and the predicted values for Friday, September 3, through Monday, September 6, are 100, 105, 110 and 115. Solar flux is expected to peak around 130 on September 9.
The planetary A index for September 3-6 is predicted at 15, 10, 10, and 10. The planetary A index may rise higher around September 5 due to a solar wind stream from a coronal hole. This could produce unsettled to active geomagnetic conditions.
The rising flux and sunspot numbers this weekend should be good news for the All Asian DX Phone Contest this weekend, especially if geomagnetic activity is quiet.
The days are getting shorter as Earth moves toward the autumnal equinox on September 22. The long days in the far northern latitudes are receding, so when there is geomagnetic activity, auroras are more visible in the north at nighttime. The start of fall is a great time for HF propagation--even past the peak of the cycle.
Let's look at the latest monthly averages for daily sunspot numbers and solar flux, and compare them with data from the past year. August's average daily sunspot number was 69.6, and the average daily solar flux was 110. These monthly averages show the steady decline of solar cycle 23.
The monthly average of daily sunspot numbers for October 2003 through August 2004 were 118.9, 103.0, 75.7, 62.3, 75.6, 81.0, 59.3, 77.3, 77.0, 87.8 and 69.6. The monthly averages of solar flux for the same period were 155.5, 140.8, 116.1, 114.1, 107.0, 112.1, 101.2, 99.8, 97.4, 119.8 and 110.0.
For more information concerning propagation and an explanation of the numbers used in this bulletin see the ARRL Technical Information Service Propagation page.
Sunspot numbers for August 26 through September 1 were 44, 33, 28, 36, 30, 11 and 12, with a mean of 27.7. The 10.7 cm flux was 97.5, 90.5, 87.2, 86.1, 89.9, 88.1 and 89.9, with a mean of 89.9. Estimated planetary A indices were 7, 8, 12, 8, 34, 28 and 9, with a mean of 15.1. Estimated mid-latitude A indices were 4, 4, 6, 5, 27, 14 and 5, with a mean of 9.3.
Amateur solar observer Tad Cook, K7RA, Seattle, Washington,
provides this weekly report on solar conditions and propagation. This report
also is available via W1AW every Friday and an abbreviated version also appears
in The ARRL Letter. Readers may
contact the author via e-mail.
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