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 Previous: Dean of ARRL Section Managers Steps Down |  Next: Surfin': You Are in Good Company |
SEATTLE, WA, Jul 4, 2003--Average daily solar flux and sunspot numbers rose slightly last week, by 24.6 for sunspots and 11.3 for solar flux. Geomagnetic indices were about the same, with average A index for the week just two points higher.
The second quarter of 2003 ended on Monday, so let's examine quarterly averages of daily sunspot and solar flux numbers to try to confirm a trend.
The average of the daily sunspot numbers during April 1 through June 30, 2003 was 107.3. The average for the previous eight quarters was 164.8, 170.4, 198.1, 178.3, 165.3, 193.5, 152.7 and 120.3.
The average daily solar flux for the same period was 124.2 and averages for the previous eight quarters were 166.7, 175.5, 219.1, 203.9, 156.4, 178.1, 164.2 and 134.3
The drop from 193.5 to 152.7, 120.3 and 107.3 for sunspot averages and 178.1 to 164.2, 134.3 and 124.2 for solar flux shows a definite and continuing decline of cycle 23. The monthly sunspot averages for May through June were 114.3, 89.6 and 118.4, and the solar flux averages for the same period were 126.8, 116.6 and 129.4. So, for the short term May was down, but June activity was back up.
Looking at the daily A index over the past week, Saturday--the first day of ARRL Field Day--was the most active day. I operated Class C mobile on 20 and 15-meter phone and CW while parked in a cemetery west of my home in Seattle. Sunday seemed more difficult to me, with the only stations worked during the last hour of Field Day being Class D stations operating from home.
On both weekend days Earth was awash in a fast solar wind that has continued, making HF conditions dicey. June 28 saw the return of a large sunspot, which is now almost squarely aimed at earth. This sunspot, number 375, released several powerful solar flares in early June. Another solar wind stream is flowing from a coronal hole and it should reach Earth by July 4.
The predicted planetary A index for the next few days is 20 to 25. Solar flux values are expected to continue to rise, perhaps peaking around 160 to 170 from July 7 to July 9. A hopeful prediction shows a low planetary A index of 10-12 around July 9 or 10. We were fooled before when a low A index of 8 was predicted, with the forecast value revised upward due to changing conditions just prior to the expected date, so don't count on low A index predictions too much. I have no idea when the generally active geomagnetic conditions will cease.
The 60-meter amateur allocation opened for use July 3 for amateurs in the United States. I'm eager to hear reports from that band.
Some possibly confusing prose in our June 20 Solar Update concerning the relationship between A and K indices and geomagnetic conditions resulted in further confusion in our June 27 report. Each index relates to a basic measure of geomagnetic disturbance called nT. The A index is a linear scale referenced to nT and the K index is a semi-logarithmic scale referenced to nT. Thanks to Ward Silver, N0AX, and Carl Luetzelschwab, K9LA, for helping to straighten all this out.
For more information on propagation and an explanation of the numbers used in this bulletin see the Propagation page on the ARRL Web site.
Sunspot numbers for June 26 through July 2 were 122, 128, 151, 112, 159, 138 and 153, with a mean of 137.6. The 10.7-cm flux was 118.9, 123.9, 123.9, 127.3, 128.2, 131.1 and 134.8, with a mean of 126.9. Estimated planetary A indices were 19, 28, 32, 26, 20, 13 and 15, with a mean of 21.9.
Amateur
solar observer Tad Cook, K7VVV 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 k7vvv@arrl.net.
| Previous: Dean of ARRL Section Managers Steps Down | Next: Surfin': You Are in Good Company |
