The K7RA Solar Update
A familiar sight appeared this week, as a sunspot emerged for one day, then was gone. Based on its magnetic polarity and high position in our Sun's southern hemisphere, sunspot 1003 was a new Solar Cycle 24 sunspot; like all the other recent sunspots, it was short lived.
For October 10-17, the US Air Force Space Weather Operation predicts the planetary A index at 5, 5, 15, 10, 5, 5, 5 and 5. Over the same period, Geophysical Institute Prague predicts quiet conditions today, October 10, unsettled October 11-12, quiet to unsettled October 13 and quiet again October 14 to 16. Sunspot numbers for October 2-8 were 0, 0, 12, 0, 0, 0 and 0 with a mean of 1.7. The 10.7 cm flux was 66.3, 67.2, 66.6, 67.4, 67.2, 66.7 and 67.7 with a mean of 67. The Estimated planetary A indices were 12, 13, 11, 4, 4, 3 and 2 with a mean of 7. The Estimated mid-latitude A indices were 11, 10, 8, 3, 3, 1 and 2 with a mean of 5.4.
Geomagnetic conditions were still quiet, except for a coronal hole wind stream on October 3 that caused unsettled conditions. The effect was slight at mid-latitudes, with middle-latitude A index for October 2-4 at 11, 10 and 8. Toward the poles, conditions were more active, as expected. In Fairbanks, the college A index for those days was 26, 32 and 17.
With northern hemisphere hours of darkness expanding and geomagnetic stability the norm, this is a good time to use the lower part of the HF spectrum -- 160, 80 and the relatively new 60 meter band.
Last week's bulletin mentioned Mike Reid, WE0H, and his experimental operation on 500 KHz. This week he mentioned that "LF and MF propagation seem to have inverted propagation from the HF bands." He notes that on October 2, 40 meters seemed dead, but 600 meters came alive. You can learn more about WD2XSH and the ARRL 600 Meter Experimental Group here.
Regarding noctilucent clouds and VHF/UHF propagation, Roger Swickis, VE7BZR, of Gibsons, British Columbia, recalls seeing them in Churchill, Manitoba in 1968 and being quite impressed at the time: "I saw them again in the early 1970s while working the midnight shift as a radio operator/weather observer in Kenora, Ontario. Early that morning, I heard Winnipeg Tower (at about 120 miles) testing on 121.5 and 243.0 MHz and we exchanged signal reports. I always wondered if the long propagation was related to the NLC."
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 in The ARRL Letter. 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.