ARLP050 Propagation de K7RA:
December 5, 2003

Propagation Forecast Bulletin 50 ARLP050
>From Tad Cook, K7RA
Seattle, WA December 5, 2003
To all radio amateurs

ARLP050 Propagation de K7RA

Geomagnetic conditions have been quite stable this week, and as a result, HF propagation has been good. Right now the earth is entering a solar wind stream, which could trigger auroras. The interplanetary magnetic field is currently pointing south, which means earth is vulnerable to the effects of solar wind.

The current forecast is for geomagnetic indices to rise over the next few days. The predicted planetary A index for Friday through Monday, December 5-8 is 20, 35, 25 and 20. Predicted solar flux for those same days is 115, 110, 105 and 105. Solar flux values are predicted to run between 105 and 110 and then reach a slightly lower minimum around December 12, then rise again toward a short-term peak around December 18-22.

Petr Kolman, OK6MGW is predicting active geomagnetic conditions for December 10-11, unsettled to active on December 5 and 9, unsettled conditions on December 6 and quiet to unsettled conditions on December 7-8.

Conditions this weekend during the ARRL 160-Meter CW contest will be affected by any geomagnetic disturbance. Check WWV at 18 minutes after the hour (or check the WWV text at at 0018, 0318, 0618, 0918, 1218, 1518, 1818, and 2118z for the latest mid-latitude K index.

If the value is 3 or less, conditions should be good. Right now conditions don't look very promising, with the mid-latitude K index at 0600z on Friday, December 5 at 5. WWV is reporting an A index of 6, but that is really based on all the K indices for December 4. Otherwise, that would be quite good.

As an example of how different these values are, if the K value of 5 were measured during an entire UTC day, the resulting A index for that day would be 48. An A index of only 6 indicates K indices for the day between 1 and 2.

Diane Leveque, NH6HE sent in a news item from NASA this week concerning openings in the earth's magnetic field detected by NASA's IMAGE (Imager for Magnetopause-to-Aurora Global Exploration) satellite. You can read the story on the NASA.GOV web site at or at the SCIENCE.NASA.GOV web site at

This story is of interest to amateur radio operators because openings in the magnetic field allow solar wind to pass through, affecting earth. The IMAGE satellite is the first spacecraft dedicated to imaging the earth's magnetosphere, and NASA has a fascinating web page for IMAGE at

David Moore also sent an article from on outbursts of gas from the sun, which is at,

And finally, Stephane Burgoyne, VE2OWL of Drummondville, Quebec sent in a truly wonderful link recently at, which provides a unique view and forecast of geomagnetic conditions in northern latitudes.

Stephane's own web site is at,, in French.

For more information about propagation and an explanation of the numbers used in this bulletin see the Propagation page on the ARRL Web site at

Sunspot numbers for November 27 through December 3 were 154, 185, 177, 178, 159, 119 and 100 with a mean of 153.1. 10.7 cm flux was 174.7, 167.7, 165.9, 152.8, 143.3, 139.3 and 123.8, with a mean of 152.5. Estimated planetary A indices were 10, 10, 9, 10, 10, 9 and 7, with a mean of 9.3.