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 Previous: ISS Commander Tells West Coast Youngsters He Believes Life Exists on Other Planets |  Next: Central California Hams Respond to Earthquake |
SEATTLE, WA, Dec 24, 2003--Because of the holiday this week, W1AW will not transmit the propagation bulletin Friday, December 26. This is an interim bulletin for December 24. Look for another update Monday, December 29, which will contain seven days (Thursday through Wednesday) sunspot, solar flux and planetary A index data normally available each Friday.
After a short-term minimum around December 9-12, solar flux and sunspot numbers have been rising. The December 19 update reported sunspot numbers for December 11-17 of 35, 36, 40, 48, 42, 71 and 92. The upward trend continued with values of 114, 113, 104, 105, 152 and 142 for December 18-23. From a low flux value on December 11, daily solar flux through December 23 was 86, 87, 88, 92, 101, 106, 118, 123, 123, 130, 133, 138 and 142.
December 21 and 22 had the only geomagnetic disturbance of this week. This was from a solar wind originating in a coronal hole that Earth passed through beginning December 21. The solar wind did not cause big auroral displays, however.
At this time of the year, geomagnetic disturbances are less common than they are in fall or spring. This is due at least in part to a seasonal variation in the earthly magnetosphere as it relates to the sun's field. There's an explanation--including the geometry of this seasonal variation--on the Science@NASA Web site.
Solar flux is expected to peak over the next couple of days. Predicted solar flux for today through December 28 is 145, 150, 150, 145 and 140. More sunspots and higher solar flux combined with a quiet geomagnetic field are a great combination for HF propagation, and we shouldn't be disappointed over the next week. Predicted planetary A index is around 10 for every day until January 1, when recurring activity is expected to disturb conditions until January 10.
Now that the nights are longer, 160, 80, 60 and 40 meters should provide good propagation between sunset and sunrise. Compared to 11 weeks ago, for example, openings should come a bit earlier, and the low bands should close much later for paths throughout the northern hemisphere.
Bob Reed, W2CE, wrote to let us know that these propagation bulletins, NW7US Solar E-alerts and DX bulletins are posted automatically on the Ham Radio DX List.
For more information about propagation and an explanation of the numbers used in this bulletin see the Propagation page on the ARRL Web site.
Amateur solar observer Tad Cook, K7RA,
Seattle, Washington, provides this weekly report on solar conditions and
propagation. This report also is available via W1AW every Friday and an
abbreviated version also appears in The ARRL Letter. Readers may
contact the author via k7ra@arrl.net.
| Previous: ISS Commander Tells West Coast Youngsters He Believes Life Exists on Other Planets | Next: Central California Hams Respond to Earthquake |
