ZCZC AP22
QST de W1AW
Propagation Forecast Bulletin 22 ARLP022
From Tad Cook, K7RA
Seattle, WA May 28, 2004
To all radio amateurs
SB PROP ARL ARLP022
ARLP022 Propagation de K7RA
Conditions weren't bad this week. Average daily sunspot numbers were down about 13 points and average daily solar flux was off about 6 points. There were no major geomagnetic disruptions. Last Friday, May 21, we were within a solar wind stream, but this was not enough to cause any geomagnetic storms.
Sunspot group 618 was just emerging from the sun's eastern limb. 618 continued to grow, and was in the center of the solar disk on Wednesday, May 26. Eventually it grew to about 120,000 km (almost 75,000 miles) across. There is a small chance it may cause a geomagnetic disturbance, but day by day it will rotate off the sun's western limb.
This weekend is the CQ World Wide WPX CW Contest. I had a lot more fun in this contest back when I held KT7H, a far less common prefix than K7RA, the current call sign. This weekend shouldn't be too bad. Solar flux is expected to remain around 100. The predicted planetary A index for Friday through Monday, May 28-31 is 10, 10, 12 and 15. Predicted solar flux for the same days is 100, 100, 105 and 105. Currently holographic helioseismic imaging reveals another sunspot group on the sun's far side, so perhaps activity will remain at the current moderate levels.
One cautionary note from the Australian Space Weather Agency was issued at 2236z on May 27. It warns of possible increased geomagnetic activity due to a solar wind stream from a coronal hole around Jun 1-3. Of course, HF operators want lots of sunspots and quiet geomagnetic conditions, which often don't appear at the same time.
For more information concerning propagation and an explanation of the numbers used in this bulletin see the ARRL Technical Information Service propagation page at, http://www.arrl.org/tis/info/propagation.html.
Sunspot numbers for May 20 through 26 were 109, 82, 79, 127, 118, 101 and 89 with a mean of 100.7. 10.7 cm flux was 104.6, 106.9, 102.4, 104, 105.2, 102.4 and 103.3, with a mean of 104.1. Estimated planetary A indices were 13, 10, 11, 12, 11, 8 and 6, with a mean of 10.1. Estimated mid-latitude A indices were 11, 6, 7, 9, 8, 5 and 3, with a mean of 7.