The K7RA Solar Update

FT WAYNE, IN, May 26, 2006--Carl Luetzelschwab, K9LA, is filling in this week for Tad Cook K7RA. With respect to space weather, the past week has been relatively quiet. Solar activity was very low--the largest flares were several Class B events--and geomagnetic field activity was quiet to unsettled--the planetary A index stayed below 10. There were some sunspots this week: Regions 884, 885, and 886 dotted the solar disk, but they weren't very active. There are also indications that old Region 882 may be coming around again.

The forecast for the next several days (Memorial Day weekend) is for continued low solar activity and quiet-to-unsettled geomagnetic field conditions. The probability of major flares or significantly elevated K indices is low. As a result, there shouldn't be any major propagation surprises. The 40, 30, 20, and 17-meter bands should provide the bulk of domestic and DX contacts, but keep an eye out for sporadic E!

This weekend is the CQ World Wide WPX Contest (CW). The format for this contest is everyone works everyone, with prefixes as multipliers. Although the QSO point structure favors DX contacts, the fact that prefixes are multipliers means domestic contacts can play an important role. This means domestic propagation can play an important role. Being at the end of May says the probability of sporadic E helping out on 10 and maybe even on 15 meters for domestic contacts is quite high. We've already had some good sporadic E propagation on 10 and 6 meters in the past week or two--hopefully it will continue.

Look for sporadic E openings around the late morning hours and then again in the early evening hours. For true DX contacts, though, 40 and 20 meters likely will be the bread-and-butter bands for this contest at solar minimum.

Propagation Tidbit: As we move into summer, we'll see a decrease in daytime F₂ region maximum usable frequencies (MUFs). This is due in large part to a change in the composition of the atmosphere at F₂ region altitudes. Summer brings decreased ratios of O (atomic oxygen) to O₂ (molecular oxygen) and of O to N₂ (molecular nitrogen). Since the electron production rate at F₂ region altitudes depends on the concentration of O, whereas the electron loss rate is controlled by O₂ and N₂, a decrease in O to O₂ and O to N₂ ratios leads to lower daytime MUFs in the summer.

For more information concerning propagation and an explanation of the numbers used in this bulletin see the ARRL Technical Information Service Propagation page. An archive of past bulletins is on the ARRL Web site.

Sunspot numbers for May 18 through 24 were 0, 15, 29, 30, 32, 48 and 44, with a mean of 28.3. 10.7 cm flux was 73.3, 75.3, 76.2, 77.5, 83.1, 84.2, and 83.7, with a mean of 79. Estimated planetary A indices were 16, 8, 7, 7, 8, 7 and 4, with a mean of 8.1. Estimated mid-latitude A indices were 11, 7, 5, 4, 6, 4 and 3, with a mean of 5.7.

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: ARRL to Rejuvenate Community Education Project, Thanks to Dayton ARA Gift

Next: Surfin': Virtually in Dayton