The K7RA Solar Update

SEATTLE, WA, Feb 25, 2005--Average daily geomagnetic indices for the week were slightly higher, and the average daily sunspot numbers and solar flux were down markedly. Average daily sunspot numbers dropped nearly 30 points to 45.4, and average daily solar flux slipped nearly 19 points to 97.3. This is compared to the seven days reported at the end of last week's Solar Update.

A week ago, we mentioned that conditions for last weekend's ARRL International DX Contest (CW) should be fair to good, but there was a worry about geomagnetic activity. Mid-latitude geomagnetic activity wasn't bad, but polar paths were affected more. The planetary A index for February 18-20 was 25, 14 and 12, and the high-latitude college A index (from Alaska) was 37, 40 and 16. Mid-latitude A index was moderate, at 14, 8 and 6.

Jeff Hartley, N8II, in West Virginia mentioned that he had a blast on 20 meters, despite somewhat disturbed conditions. The beam heading from his QTH to Japan is 330 degrees, which puts it right through the auroral zone. JA stations were weak and fluttery. Propagation to Europe was much better (Germany has a 47 degree beam heading for Jeff), and he worked about 1500 European stations.

Disturbed conditions on HF often portend good propagation on VHF. Jon Jones, N0JK, in Kansas mentioned sporadic E skip on 6 meters from February 18-23. He and Ken Neubeck, WB2AMU, are working on a paper on the subject of geomagnetic disturbances and 6 meter E-layer propagation. Jon writes, "While aurora activity usually dampens regular mid-latitude Es, the day(s) after the aurora subsides may see increased Es activity." WB2AMU has written extensively on VHF, and has published the books, Six Meters-A Guide to the Magic Band and VHF Propagation--A practical guide for radio amateurs.

N0JK mentioned that the 6 meter opening on February 20 lasted from 1900 to 0100 UTC, and it extended across much of the Eastern US and southern Canada. He worked two stations in Mexico that day. "From Kansas, stations in Georgia and Florida were booming in for hours," he wrote. He noted that E-layer openings in late February are rare.

This weekend is the CQ World Wide 160 Meter Contest (SSB), and for 160 meters we hope for quiet geomagnetic conditions. The latest forecast for February 25-27 is for a planetary A index of 15, 20 and 20. The Prague Geophysical Institute projects active geomagnetic conditions for February 26, and unsettled to active for February 25 and 27. This is because Earth is moving into a solar windstream coming from a coronal hole. Sunspot numbers and solar flux should remain quite low. Predicted solar flux for February 25-27 is 80, and flux values are not expected to rise above 100 until around March 9, and then only slightly.

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

Sunspot numbers for February 17 through 23 were 51, 46, 51, 60, 33, 23 and 54, with a mean of 45.4. The 10.7 cm flux was 111.3, 104.2, 98.5, 95.7, 94.5, 92.3 and 84.6, with a mean of 97.3. Estimated planetary A indices were 6, 25, 14, 12, 8, 4 and 4 with a mean of 10.4. Estimated mid-latitude A indices were 7, 14, 8, 6, 4, 3 and 2, with a mean of 6.3.

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 appears in The ARRL Letter. Readers may contact the author via e-mail.

Previous: Ham Radio Saves a Ham in Alaska

Next: ARRL Hopes Consent Decree will Reduce Interference Complaints