ARRL

ARRL Propagation Bulletin ARLP016 (2003)

SB PROP @ ARL $ARLP016
ARLP016 Propagation de K9LA

ZCZC AP16
QST de W1AW  
Propagation Forecast Bulletin 16  ARLP016
From Carl Luetzelschwab, K9LA
Fort Wayne, IN  April 17, 2003
To all radio amateurs 

SB PROP ARL ARLP016
ARLP016 Propagation de K9LA

Carl Luetzelschwab, K9LA is filling in for Tad Cook, K7RA this week.
This report is one day earlier than usual because of Good Friday.

Geophysical activity during the period ran the full gamut - from
quiet early in the period to some minor to major storminess later in
the period. The minor to major storminess was caused by high-speed
solar wind that was induced by a coronal hole.

Solar activity during the period was low to very low. The largest
flare was a C7 event last Friday.

For the next several days, geophysical activity is forecasted to
decrease to unsettled conditions. Thus propagation should generally
improve as the weekend approaches. Additionally, solar activity is
forecast to be low for the next several days, so flares shouldn't
cause any problems.

Your reporter noted many 6-meter spots on PacketCluster early this
week. This is a reminder that the summer Es (sporadic E) season is
underway, and Es can provide a link to trans-equatorial propagation
(TEP) for stateside stations. Jon, N0JK reports southwest, south,
and east coast stations working into South America on Monday and
Tuesday afternoon and into the evening. Be sure to keep an eye on
6-meters, as historical data shows that the 6-meter Es season begins
around April, peaks around July, and tapers off by October (there is
also a minor secondary peak in December). The best times for summer
6-meter Es are from late morning to early afternoon, and then again
from early evening to late evening.

If you found the higher bands better early in the period (before the
minor to major storminess occurred) than the 10.7 cm solar flux
predicted, the reason was probably due to the F region being more
ionized than the 10.7 cm flux indicated. During the entire reporting
period, the 10.7 cm solar flux hovered around 100, and that equates
to a sunspot number of about 50. But the effective sunspot number
(SSNe), which is the sunspot number that forces a best worldwide fit
between the model of the F region and real-time ionosonde data, was
substantially higher--it varied between 75 and 90 during the
reporting period.

Sunspot numbers for April 10 through 16 were 66, 49, 60, 61, 63, 54,
and 40, with a mean of 56.1. 10.7 cm flux was 103.7, 102.6, 102.1,
102.4, 102, 100.5, and 98.5 with a mean of 101.7. Estimated
planetary A indices were 26, 14, 7, 10, 16, 22, and 31, with a mean
of 18.
NNNN
/EX