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SEATTLE, WA, Apr 15, 2005--This week saw an insignificant rise in average daily sunspot numbers and solar flux compared to the previous week. Average daily sunspot numbers were up by a little more 1 point to 40.6. Average daily solar flux rose by more than 5 points to 86.9.
There was a rise in geomagnetic activity due to a solar wind stream from a coronal hole. The planetary A index numbers for April 12, 13 and 14 were 30, 26 and 19. We have moved out of the solar wind, and the prediction is for quieter conditions. The predicted planetary A index for April 15, 16, 17 and 18 is 12, 10, 8 and 5. Sunspot counts and daily solar flux numbers are expected to stay about the same--perhaps declining slightly after April 19.
On the Web site for the Western Washington DX Club I spotted a number of links to presentations from past club meetings, either on technical topics or DXpeditions. One that might be of interest to “Solar Update” readers is a PDF of K9LA’s talk on 160 meter propagation at last summer’s Northwest DX Convention. This very interesting tutorial covers several aspects of 160-meter propagation, and it examines the notion that this band is better during the sunspot minimum.
For more information concerning radio propagation and an explanation of the numbers used in this bulletin see the ARRL Technical Information Service Propagation page.
Sunspot numbers for April 7 through 13 were 49, 56, 43, 42, 17, 32 and 45, with a mean of 40.6. The 10.7 cm flux was 87.8, 87.7, 88.4, 88.3, 87.5, 84.9 and 83.5, with a mean of 86.9. Estimated planetary A indices were 8, 4, 4, 4, 10, 30 and 26, with a mean of 12.3. Estimated mid-latitude A indices were 4, 2, 2, 2, 6, 23 and 18, with a mean of 8.1.
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