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The K7RA Solar Update

04/24/2009

Teased again, on Wednesday, April 22 we saw sunspot 1015 fade away, just as it was about to slip over our Sun's western limb. It emerged only briefly, late on April 21, and by Thursday it had disappeared. Sunspot numbers for April 16 through 22 were 0, 0, 0, 0, 0, 0, and 11 with a mean of 1.6. The 10.7 cm flux was 69.9, 69.8, 69.9, 70.1, 69.8, 71, and 71.1 with a mean of 70.2. The estimated planetary A indices were 6, 5, 8, 4, 4, 5 and 4 with a mean of 5.1. The estimated mid-latitude A indices were 3, 4, 8, 4, 3, 3 and 2 with a mean of 3.9. The outlook for the near term is more of the same, quiet conditions. Geophysical Institute Prague predicts quiet conditions for April 24-30. The US Air Force and NOAA predict a nice quiet planetary A index of 5 until May 6-9, when they expect to see a planetary A index of 15, 8, 8 and 8.

The 10.7 cm solar flux (2.8 GHz radio energy, measured in Penticton, British Columbia with a parabolic antenna that tracks the Sun) rose slightly with the sunspot appearance to 71 and 71.1. The average solar flux for the week increased slightly over the previous week, from 69.3 to 70.2. Both planetary and mid-latitude average A index declined from 6.6 to 5.1 and 4.6 to 3.9, respectively.

Sunspots have become so rare that many of us were happy to see anything at all, and of course a low geomagnetic index is welcome. One thing about this extended solar minimum: With solar wind declining and not much to upset our Earth's magnetosphere, it is great for 160 meters.

Calvin Branch, KA1WOR, of Hudson, Florida, sent a link to an interesting BBC item about the extended solar minimum. Some interesting observations in the article include the assertion that the 20th century saw high solar activity, and perhaps that is now quieting down. Many of us were hoping that the activity 50 years ago during Solar Cycle 19 was normal, and had hoped that it might return, but that doesn't seem to be the case. This is too bad, because most of us get to experience only a few solar cycles. I was licensed as a Novice when I was a pre-teen, so I've seen four complete cycles, and I will probably see five, but six, or seven? One can hope.

The BBC seems to do a good job of science reporting, but I'm still seeing lots of confusion about what the solar cycle is actually doing. Tonight I read a blog post making fun of climatologists that claimed the current solar minimum has been ongoing for nine years now. Of course, this is nonsense. The average daily sunspot number for each year since 1999 is:

1999 146.3
2000 173
2001 170.3
2002 176.7
2003 109.2
2004 68.6
2005 48.9
2006 26.1
2007 12.8
2008 4.7

These numbers were derived by adding up each year's daily sunspot data presented in this bulletin, then diving by 365, or 366 in the case of 2000, 2004 and 2008. I queried the blogger for more info on his data, but haven't seen anything yet.

We are beginning to receive reports for the spring sporadic-E season. Mike Schaffer, KA3JAW, in grid square EL87 (Tampa, Florida area) looks for Central American and Caribbean television signals, and on April 18, he sent his first sporadic-E observation since February 22, when he last received a Guatemala station. At 2113 UTC, he copied WKAQ in San Juan, Puerto Rico, and at 2145 UTC, he copied WIPM in Mayaguez.

He wrote, "The distance to both stations is 1232 miles, with a heading of 118 degrees from Tampa, Florida. I noticed on AccuWeather.com that a satellite that measures water vapor content had shown dry air over the Bahamas at 2145 UTC. The half-way point was 616 miles, 45 miles east-northeast from Clarence Town, Bahamas, the same general area where there was dry air overhead. The event lasted a total of 45 minutes before the plasma cloud drifted out of range, with no further signals being detected".

On April 19 at 1146 and 1200 UTC, he picked up an unidentified station broadcasting music on channel 2, and on channel 3 the Mexican TV network Televisa. He wrote, "I believe that springtime E-s has officially arrived. I say this because this is when Mexican, Central American and South American stations are detected during the early morning hours at my location. During the winter months, it's the reverse, late afternoon or early evening hours. While I was recording various programming, the logo from El Super Canal, TGV, Guatemala City, Guatemala showed itself with a white number three at the top/right of the screen multiple times. At 1300 UTC (9 AM EDT), the last program that was seen before it vanished was a Spanish religious service".

Vince Varnas, W7FA, of Aloha, Oregon, reported lots of 10 meter activity on April 23 from 0100-0330 UTC (April 22 his local time). At 0108 UTC, he worked LU7KAT, he thinks on trans-equatorial propagation, and shortly after worked KH7XS in Hawaii, he believes on sporadic-E. He also worked New Mexico and Arizona on sporadic-E. At 0325 UTC, he worked ZL1BYZ, he thinks on F2 propagation. He said he was most surprised by the last contact, 7000 miles at 8:25 PM his local time.

Charles Preston, KL7OA, of Anchorage, Alaska, sent along information on WSPRnet, the Weak Signal Propagation Reporter Network. I don't know the details, but it appears to be an automated network that tells users which bands are open between a number of locations. On their interactive map, you can restrict the display by time or to a particular band. Charles also mentioned using the network for comparing antenna performance. He has a paper on this here.

Doug Wetzel, K7IP, of Everett, Washington, sent in a link to a page of propagation info that his friend KG7HQ maintains. The map shows overhead foF2 MUF, based on real-time data from ionospheric sounders, or ionosondes. The data originates at the Australian Space Weather Agency.

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 email.



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