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ARRL Propagation Bulletin ARLP022 (2004)

ARLP022 Propagation de K7RA

QST de W1AW  
Propagation Forecast Bulletin 22  ARLP022
From Tad Cook, K7RA
Seattle, WA  May 28, 2004
To all radio amateurs 

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

For more information concerning propagation and an explanation of
the numbers used in this bulletin see the ARRL Technical Information
Service propagation page at,

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.


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