ARRL

News

The K7RA Solar Update

09/17/2010

The average daily sunspot numbers dropped nearly 23 points to 15.6 this week, and geomagnetic indices were quiet. The average daily solar flux was 78.1, but the latest prediction from USAF and NOAA calls for rising solar flux values. The September 17-23 projection has solar flux values at 85, 85, 86, 86, 86, 87 and 88, which is well above last week’s average. Solar flux hasn’t been to 88 or higher since August 7 (90.5), and before that July 21 (89.1). Sunspot numbers for September 9-15 were 0, 11, 11, 26, 17, 24 and 20, with a mean of 15.6. The 10.7 cm flux was 73.7, 75.3, 78, 78.3, 79.5, 80.7 and 81.2, with a mean of 78.1 The estimated planetary A indices were 4, 2, 1, 1, 2, 9 and 7, with a mean of 3.7. The estimated mid-latitude A indices were 4, 2, 1, 1, 1, 7 and 4, with a mean of 2.9.

The same forecast shows planetary A index for the same period at 8, 5, 5, 5, 18, 18 and 15, indicating rising geomagnetic activity, along with the increased solar activity. Geophysical Institute Prague predicts quiet to unsettled conditions September 17, quiet September 18-19, quiet to unsettled September 20 and unsettled conditions September 21-23.

The autumnal equinox occurs Wednesday, September 22 at 11:09 PM EDT (0309 UTC on September 23). With the northern and southern hemispheres bathed in equal amounts of light, expect better worldwide HF propagation, although solar activity continues at a low level that does not support an MUF into the higher frequencies over most paths.

By the way, the bulletin didn’t mention this at the beginning of September, but the monthly averages of daily sunspot numbers have risen the past few months. For June, July and August, the average daily sunspot numbers for each month were 18, 23.1 and 28.2; so far in September, the average for the first 16 days is 29.6.

Last Saturday, September 11, Pete Rosenberg, AC7SB, Doug Phillips, W7RDP, and Rod Johnson, WE7X, went to the Suntop forest fire lookout station in the Cascade Mountains in Washington State (GPS 47.041 degrees N, 121.5965 degrees W). While there, they used a telescope and filter to view an emerging sunspot. Phillips and Johnson operated the ARRL VHF Contest, and Rosenberg worked 40 meter CW using a tape-measure dipole. Check out this photo album of their adventure.

Scott Bidstrup, TI3/W7RI, in Costa Rica sent an article about tsunami waves disrupting the ionosphere.

Mike Downing, KC0Y, of Broomfield, Colorado, is getting back on 6 meters after many years and wonders how things have changed regarding TVI? He mentioned that most people are using cable TV and the broadcasters have left channel 2, which had a lot of the problems in the past. According to what I’ve heard, the situation is much better than it was decades ago, for the reasons that Mike mentioned.

All times listed are UTC, unless otherwise noted.

Amateur solar observer Tad Cook, K7RA, of Seattle, Washington, provides this weekly report on solar conditions and propagation. This report also is available via W1AW every Friday, and an abbreviated version appears each Thursday in The ARRL Letter. You can find a guide to articles and programs concerning propagation here. Check here for a detailed explanation of the numbers used in this bulletin. An archive of past propagation bulletins can be found here. You can find monthly propagation charts between four USA regions and 12 overseas locations here. Readers may contact the author via e-mail.



Back