April 4, 2003

ZCZC AP14

QST de W1AW

Propagation Forecast Bulletin 14 ARLP014

From Tad Cook, K7RA

Seattle, WA April 4, 2003

To all radio amateurs

SB PROP ARL ARLP014

ARLP014 Propagation de K7RA

Unsettled geomagnetic conditions continued, with the average daily planetary A index increasing over the previous week. Only one day was mildly unsettled, April 1, with the planetary A index at 12. All other days of the week were more active. But the K index dropped all the way from 5 to 1 over the first six hours of that UTC day. (The daily A index is calculated from the K index, taken every three hours. A UTC day is the 24 hours after 0000z.) K index at 5 is very stormy, and if continued through a whole day would result in an A index of 48. You can see the relationship between K and A indices at http://www.ngdc.noaa.gov/stp/GEOMAG/kp_ap.html.

The predicted planetary A index for Friday through Monday, April 7 is 10, 12, 12 and 15. Geomagnetic conditions are expected to be active again April 10-15, with the rougher conditions toward the end of that period. The author has been operating mostly 17-meter HF mobile lately, and not getting on the air when the mid-latitude K index has been 4 or higher as reported by WWV. The K index is updated every three hours, and a convenient way to check it is to call 303-497-3235. Another way to check (other than listening to WWV at 18 minutes or WWVH at 45 minutes past the hour) is to point your web browser toward ftp://ftp.sel.noaa.gov/pub/latest/wwv.txt.

Solar flux is expected to drift down below 150 over the next few days, and may go to a low around 110 from April 17-21. It is not expected to dip below 100 as it did last month. This week average daily sunspot numbers rose nearly 108 points and average daily solar flux rose 52 points, when compared to the previous week.

We are currently in springtime propagation. As the days lengthen, 80-meter propagation will fade and worldwide 20-meter propagation will extend into the night. The sunspot count is still high enough that 10 and 12-meters should remain promising, much better this year than next spring.

Another quarter year has passed, and a daily average of sunspot numbers and solar flux with tell us about the trend of the solar cycle. The average daily sunspot number for the first quarter of this year was 120.3. The average for the previous eight quarters was 147.3, 164.8, 170.4, 198.1, 178.3, 165.3, 193.5 and 152.7. We haven't seen a quarter with an average daily solar flux as low as 120.3 since the first quarter of 1999, when it was 96.1.

The average daily solar flux for the first quarter of this year was 134.3. The average daily flux values for the previous eight quarters was 164.4, 166.7, 175.5, 219.1, 203.9, 156.4, 178.1 and 164.2. A quarterly flux value as low as 134.3 hasn't been seen since the third quarter of 1998, when it was 129.2. We are definitely on the other side of the current cycle and heading down. The rough thing for HF operators is that sunspot counts are lower as geomagnetic disturbances seem more frequent.

Of course unsettled and active geomagnetic conditions aren't bad for everyone. Tom, K4SUS of Miami is positively glowing about making 6-meter Worked All States on Sunday, March 30. He worked K6MIO in Hilo, Hawaii on SSB at 2211z, a distance of a little over 4,700 miles from Tom's QTH in southwest Miami. Tom uses a home made 4-element quad inside his HF quad antenna at 65 feet. The path was via backscatter skewed southwest of the direct path.

He said this is one of the greatest highlights of his 6-meter operation over 40 years, with 108 DXCC countries worked and 102 confirmed. On the day he worked Hawaii, the planetary K index indicated disturbed conditions, with numbers as high as 4 and 5.

Tom says 6-meters is open most afternoons and evenings via trans-equatorial propagation to South America with many 6-meter signals at S9-plus.

Sunspot numbers for March 27 through April 2 were 156, 189, 155, 176, 165, 161, and 189, with a mean of 170.1. 10.7 cm flux was 141.1, 146.9, 155.1, 154.5, 160.1, 153, and 157.5, with a mean of 152.6. Estimated planetary A indices were 27, 24, 27, 26, 31, 12, and 20, with a mean of 23.9.