ARRL

News

The K7RA Solar Update

01/09/2009

On Wednesday, January 7, a sunspot appeared very briefly in the lower right portion of the Sun's image. It was so brief that NOAA did not record it on the Space Weather Prediction Center's daily solar data chart for that day. Spaceweather.com reported a sunspot number of 11 for the day, and the magnetic polarity was consistent with a new Solar Cycle 24 spot. Today, January 9, there is another Solar Cycle 24 appearance, this time on the upper left of the image. Sunspot numbers for January 1-7 were 0, 0, 0, 0, 0, 0 and 0 with a mean of 0. The 10.7 cm flux was 68.9, 69.9, 69.5, 68.8, 69.2, 68.7 and 69 with a mean of 69.1. The estimated planetary A indices were 6, 3, 9, 4, 4, 3 and 3 with a mean of 4.6. The estimated mid-latitude A indices were 5, 3, 8, 5, 3, 2 and 1 with a mean of 3.9.

In the past couple of weeks, we hoped for a return of sunspots since activity was detected on side of the Sun opposite from Earth. The Sun rotates relative to Earth about every 27-28 days (although the rotation varies somewhat with latitude), and so unless it fades quickly away, far side activity may come into view. Until recently, astrophysicists could only guess on far side events, but some modern methods have extended the view.

Helioseismology is the study of pressure waves in the Sun, and can be used to detect sunspots on the far side by looking for magnetic variations corresponding to sunspots. Pressure waves bounce around inside the Sun, and the echoes change when they reflect off of magnetically complex areas. Stanford University has a Web page devoted to acoustic imaging of the Sun's far side, as does Wikipedia.

NASA's STEREO Mission (Solar TErrestrial RElations Observatory) can provide views around the sides of the Sun: It uses two identical satellite observatories, one leading Earth's orbit, and the other trailing. It can also provide three-dimensional images. For details, see the NASA STEREO mission page here and here. You can also see the satellite's current positions.

Herbie Feichtinger, DC1YB, wanted everyone to take a look at these STEREO images that show both current ahead and behind images. Also check out the projects on Herbie's Web site.

Besides the spot indications from the far side, the NOAA/US Air Force daily forecast predicted a rise in daily solar flux, which could correlate with sunspot appearance. You can check the daily forecasts going back three weeks. Note on December 23, they first predicted a rise of solar flux to 71, running from December 31-January 5. The next day, December 24, their prediction changed to December 27-January 5. This remained until the December 29 forecast, when it changed to 70 for December 30-January 7, and below 70 after that. The latest forecast on January 8 had solar flux remaining below 70 until January 15, then rising to 70 for January 16-February 5, but never rising above 70.

Last week's bulletin reported that the ionosphere is now at a lower elevation than in the past, but Carl Luetzelschwab, K9LA, wrote in suggesting that this isn't really true, and our misunderstanding is probably due to some poor science reporting. The data reported is only accurate for equatorial latitudes. An explanation is on Carl's Web site. Just click on Timely Topics toward the top, then the January 3 report, titled "Is the ionosphere really lower?"

Michael Mona, KD0ZW, of Clive, Iowa, wrote about his QRP experiences, and said that even with no sunspots, he is having fun running 5 W and only batteries powered by a solar cell. Read about it on his web site.

Flavio Archangelo, PY2ZX, wrote to tell us about an interesting experiment he is participating in with the Japy DX Group. They are travelling north in Brazil to Bahia to experiment with transatlantic tropospheric ducting propagation with Africa. An English language Web page describing the trip can be found here; find a Portuguese page here You can paste that last URL into a translation tool under the "Translate a Web Page" heading. Just select Portuguese for the first language option, and English or any other language for the second option.

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.



Back