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The K7RA Solar Update

09/25/2009

This week we had a double-dose of good news: Right at the time of the autumnal equinox on Tuesday, September 22, sunspot 1026 -- a new Solar Cycle 24 sunspot -- came into view over the Sun's eastern horizon. We watched this emerge a week ago on the Sun's far side via the STEREO project.

STEREO is a fantastic tool because it gives us all a live view of nearly the whole Sun and it displays very recent images. It turns out that images from each craft -- the ahead (leading earth in its orbit) and the behind (trailing earth in its orbit) satellite -- are updated approximately every 15 minutes! No more guessing about activity on the other side of the Sun, since we can see it live in animated form based on real time data.

On that animated sun display you can see there are longitude lines every 30 degrees. Since there are 12 of them, and a rotation of the sun takes approximately 27.5 days (it varies by latitude), then on average it takes about .0764 days (1 hour, 50 minutes) for the Sun's rotation to progress one degree longitude. Therefore, when we saw the sunspot at -120 degrees longitude, we could estimate that it would take about 2.2917 days (2 days and 7 hours) for the spot to reach the Sun's eastern horizon (at -90 degrees) and first become visible.

On Monday, the daily sunspot number was 11. Then on Tuesday and Wednesday, a second Solar Cycle 24 spot (number 1027) emerged in the sun's northern hemisphere. Tuesday's daily sunspot number rose to 26, then on Wednesday it was 31 as the area of the spots grew. On Thursday, the sunspot number was 32. From Monday to Tuesday, the total sunspot area increased by seven times, then on Wednesday it doubled, then on Thursday rose about 29 percent over Wednesday's area. You can see the sunspot numbers, solar flux and sunspot area for each day here.

When we look here, it shows us that geomagnetic indices are extremely quiet and stable, so I suppose there are three pieces of great propagation news this week. Both sunspots have moved into their maximum geo-effective position (around zero degrees longitude, in the center of the solar disc as viewed from Earth), led by sunspot 1027.

Sunspot numbers for September 17-23 were 0, 0, 0, 0, 11, 26 and 31 with a mean of 9.7. The 10.7 cm flux was 69.1, 69, 70.5, 71.3, 71.9, 74.7 and 76.1 with a mean of 71.8. The estimated planetary A indices were 8, 3, 2, 4, 7, 4 and 2 with a mean of 4.3. The estimated mid-latitude A indices were 6, 2, 1, 3, 5, 2 and 1 with a mean of 2.9. The current prediction from NOAA/USAF is for continued quiet conditions today with a planetary A index of 5, then on Saturday some unsettled conditions and a planetary A index of 12. It drops to 8 on Sunday, then back to 5 for the foreseeable future. Solar flux is expected to continue at about the same level through the first few days of October. Geophysical Institute Prague has a similar prediction for geomagnetic values: Quiet to unsettled September 25, unsettled September 26, quiet to unsettled September 27 and quiet conditions September 28 through October 1.

Ken Tata, K1KT, of Warwick, Rhode Island (grid square FN41gs), reports that the Fall 144 MHz Sprint saw some great activity along the East Coast. This event, sponsored by the Southeastern VHF Society (SVHFS), lasted for just four hours, from 7-11 PM local time on Monday, September 21. Ken wrote: "From Rhode Island, the band was open from at least Central Virginia to Southern Nova Scotia. Overall, signals were stable with shallow, slow QSB. This was perhaps the most active 2 meter contest I've seen. At 8 PM local time, it sounded like an HF contest!"

Tim Hickman, N3JON, of Timonium (Baltimore area), Maryland, said, "Propagation is up!" after he worked VK4MA long path on September 23 at 2137 UTC. Tim was running barefoot with a small 2-element multi band beam, and received an S5 signal report. Unfortunately, he didn't say what band he was using, but I will bet it was 20 meters.

K4WY, KI4BXN and others tipped us off to a fascinating new story about solar wind during the cycle minimum. Dr Sarah Gibson, lead scientist on the study, found that solar wind may be much more active during cycle minima than previously thought. See the story here, here and here.

This weekend is the CQ World Wide RTTY Contest, and FT5GA, the Glorioso DXpedition, will be active. With the heightened solar activity, here are some rough propagation estimates for the path to Glorioso Island this weekend, which is off the East Coast of Africa, northwest of Madagascar (all times UTC):

  •  From Chicago: Best bet for 15 meters is 1600-2100; 1600-2300 for 17 meters; 1930-0030 on 20 meters; 2130-0400 on 30 meters; 40 meters from 2230-0030, and 80 meters from 2300-0300.

  •  From Cleveland, Ohio: Check 15 meters 1500-2030; 17 meters 1700-2230; 20 meters 1900-0030; 30 meters 2100-0400 with a possibly difficult period 0200-0230; 40 meters 2200-0330, and 80 meters 2300-0300.

  •  From Boston: 12 meters 1400-1830; 15 meters 1200-2130 with signals gradually increasing over that period; 17 meters also increasing signal strengths 1300-2300; 20 meters 1730-0030 with increasing signal strengths; 30 meters 1900-0430 with best chance 2130-0100; 40 meters 2130-0330, and 80 meters 2200-0230.

  •  From New York City: 12 meters 1430-1900; 15 meters 1200-2130; 17 meters 1330-2300; 20 meters 1800-0030; 30 meters 2200-0330; 40 meters 2100-0400, and 80 meters 2230-0300.

  •  From Philadelphia: 12 meters 1430-1900; 15 meters 1200-2200; 17 meters 1330-2300; 20 meters 2000-0030; 30 meters 2200-0400; 40 meters 2100-0400, and 80 meters 2230-0330.

  •  From Atlanta: 15 meters 1500-2130; 17 meters 1630-2300; 20 meters 2000-0030; 30 meters 2130-0400; 40 meters 2230-0400, and 80 meters 2330-0300.

  •  From Miami: 10 meters 1600-1730; 12 meters 1500-1800; 15 meters 1600-1930; 17 meters 1630-2230; 20 meters 2000-0030; 30 meters 2130-0430; 40 meters 2230-0330, and 80 meters 2230-0300.

  •  From Dallas: 15 meters 1430-2230; 17 meters 1600-2330; 20 meters 2100-0030; 30 meters 2200-0430; 40 meters 2330-0330, and 80 meters 0000-0300.

  •  From Omaha: 15 meters 1630-2100; 17 meters 1530-2330; 20 meters 2000-0030; 30 meters 2200-0400; 40 meters 2300-0330, and 80 meters 0000-0230.

  •  From Phoenix: 12 meters 1900-2100; 15 meters 1530-2300; 17 meters 1400-0000; 20 meters 2130-0030 and around 0330; 30 meters 0000-0330; 40 meters 0000-0300, and 80 meters 0100-0230.

  •  From Denver: 15 meters 1630-2200; 17 meters 1500-0000; 20 meters 2000-0030, and 30, 40 and 80 meters 0000-0300.

  •  From Salt Lake City, 15 meters 1730-2230; 17 meters 1500-0000' 20 meters 2000-0030, 30 meters 2130-0330; 40 meters 0030-0230, and 80 meters 0030-0230.

  •  From the middle of California: 15 meters 1730-2300; 17 meters 1530-0000; 20 meters 1430-0030 and also 0300-0400, with dropouts at 1600 and 2100; 30 meters 2330-0330; 40 meters 0130-0300, and 80 meters 0130-0230.

  •  From Seattle: 15 meters 1930-2230; 17 meters 1700-2330; 20 meters 1430-0300; 30 meters 2100-0300, and 40 meters 0000-0230.

  •  From Hawaii: 10 meters 0330-0600; 12 meters 0300-0700; 15 meters 0230-0830; 17 meters 1100-1230; 20 meters 1230-1500 and 1730-1930; 30 meters 1300-1800; 40 meters 1330-1730, and 80 meters 1430-1700.

On most of the above paths, signals gradually strengthen throughout the given time period.

Amateur solar observer Tad Cook, K7RA, of 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. Check here for a detailed explanation of the numbers used in this bulletin. An archive of past propagation bulletins can be found here. You can find monthly propagation charts between four USA regions and 12 overseas locations here. Readers may contact the author via e-mail.



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