ZCZC AP40
QST de W1AW
Propagation Forecast Bulletin 40 ARLP040
From Tad Cook, K7VVV
Seattle, WA October 6, 2000
To all radio amateurs
SB PROP ARL ARLP040
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 http://edge.net/~scraig/index.html or specifically http://edge.net/~scraig/sol.htm or 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 http://sec.noaa.gov/getftp.cgi , 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.