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ARRL Propagation Bulletin ARLP040 (2000)

ARLP040 Propagation de K7VVV

QST de W1AW  
Propagation Forecast Bulletin 40  ARLP040
From Tad Cook, K7VVV
Seattle, WA  October 6, 2000
To all radio amateurs 

ARLP040 Propagation de K7VVV

Average solar flux and sunspot numbers were off for the week, while
geomagnetic indices were up, the result of coronal mass ejections
and the subsequent solar wind. Average sunspot numbers were off by
nearly 43 points and solar flux was down nearly 28 points.

A series of coronal mass ejections kept things lively, with two days
(Saturday and Wednesday) when the planetary A index reached 45. This
is an indication of a geomagnetic storm. Until daybreak on Thursday,
October 5, auroral lights were spotted as far south as latitude 43
degrees. This was probably the result of a solar coronal mass
ejection on October 2. The NASA ACE spacecraft recorded an
interplanetary shock wave at 0240z on October 5.

Effects are expected to fade over the next few days, with the
planetary A index predicted for Friday through Wednesday at 35, 15,
10, 10, 12 and 12. Solar flux is expected to reach a minimum during
this period with a 10.7 cm flux value at 150. Predicted flux values
for Friday through Wednesday are 170, 160, 150, 150, 150 and 160.
Solar flux is expected to rise above 200 again after October 16, and
peak around 215 from October 18-22.

Because September 30 marked the end of the third calendar quarter of
2000, it is time to review quarterly averages of solar flux values.

The average daily solar flux for July 1 through September 30 was
181.9, one point lower than the earlier quarter, 182.9. The first
quarter of this year had an average daily solar flux value of 180.5.
This seems to indicate a fairly flat average solar flux value for
this year, which was predicted to be the peak year for this solar
cycle. These values are higher than the solar flux levels for 1999.

Average solar flux for September was 182.1, which is an improvement
over August, which was 163.1. Average monthly solar flux values
since the beginning of this year were 159, 174.1, 208.2, 184.2,
184.5, 179.8, 200.5, 163.1, and 182.1.

Readers who use Scott Craig's Solar Data Plotting Utility noticed
that it would not suck up data from last week's Propagation Forecast
Bulletin ARLP039. This is because of wording in the bulletin that
confused the automatic data gathering feature in the software. Scott
is writing a revision to the code so that it will not have that
problem in the future, if ever that particular sequence of words
that caused the problem is used again. Of course you can manually
edit the data file to update the solar flux and sunspot numbers. You
can also check or specifically for an update. Look for something
beyond the current version, which is 3.08w.

G3LDI wrote to inquire about a source for solar flux, A index and K
index data over the past year. To get this data, go to the Space
Environment Center's FTP server at ,
then click on the Indices, Events and Region Data line, then click
on Solar, Particle and Geomag Indices beginning Jan 1994.

Sunspot numbers for September 28 through October 4 were 211, 164,
155, 157, 190, 196 and 216 with a mean of 184.1. 10.7 cm flux was
202.3, 192, 193.6, 201.6, 202.6, 192 and 184.1, with a mean of
195.5, and estimated planetary A indices were 12, 7, 45, 13, 11, 37
and 45 with a mean of 24.3.


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