In the past couple of weeks we hoped for a return of sunspots because activity was detected on the 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 fairly 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 page devoted to acoustic imaging of the Sun’s far side at, http://soi.stanford.edu/press/ssu03-00/backside.html, and Wikipedia has a page at, http://en.wikipedia.org/wiki/Helioseismology.

NASA’s STEREO Mission (Solar TErrestrial RElations Observatory) can provide views around the sides of the Sun, because it employs 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 at, http://www.nasa.gov/mission_pages/stereo/main/index.html and also check http://stereo.gsfc.nasa.gov/gallery/gallery.shtml. You can see the satellite’s current positions at, http://stereo.gsfc.nasa.gov/where.shtml.

Herbie Feichtinger, DC1YB wanted everyone to take a look at the STEREO images at, http://stereo-ssc.nascom.nasa.gov/beacon/beacon_secchi.shtml that show both current ahead and behind images. Also check out his projects on his web site at, http://herwig.shamrock.de/hamradio.htm.

Besides the spot indications from the far side, the NOAA/USAF daily forecast predicted a rise in daily solar flux, which could correlate with sunspot appearance.

On the site, http://www.swpc.noaa.gov/ftpmenu/forecasts/45DF.html 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 through January 5. The next day, December 24, their prediction changed to December 27 through January 5. This remained until the December 29 forecast, when it changed to 70 for December 30 through 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 through February 5, but never rising above 70.

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 at http://www.swpc.noaa.gov/ftpdir/indices/DSD.txt, but Spaceweather.com reported a sunspot number of 11 for the day, and the magnetic polarity was consistent with a new Cycle 24 spot.

Today on January 9 there is another Cycle 24 appearance, this time on the upper left of the image.

See it at, http://www.spaceweather.com/images2009/09jan09/newsunspot.jpg.

Last week’s Propagation Forecast Bulletin ARLP001 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, http://mysite.verizon.net/k9la/. 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 watts, and only batteries powered by a solar cell. Read about it on his web site at, http://www.kd0zw.com/.

Flavio Archangelo, PY2ZX, wrote to tell us about an interesting experiment he is participating in with the Japy DX Group. They are traveling north in Brazil to Bahia to experiment with transatlantic tropospheric ducting propagation with Africa. An English language web page is at, http://www.japydx.org/ta/bahia2.html and http://japydx.org/ta/index.html is in Portuguese. You can paste that last URL into a translation tool at, http://www.google.com/language_tools?hl=en 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.

Of course, it is currently several weeks into Summer on that side of the equator.

If you would like to make a comment or have a tip for our readers, email the author at, [email protected].

For more information concerning radio propagation, see the ARRL Technical Information Service web page at, http://www.arrl.org/tis/info/propagation.html. For a detailed explanation of the numbers used in this bulletin see, http://www.arrl.org/tis/info/k9la-prop.html. An archive of past propagation bulletins is at, http://www.arrl.org/w1aw/prop/.

Monthly propagation charts between four USA regions and twelve overseas locations are at http://www.arrl.org/qst/propcharts/.

Sunspot numbers for January 1 through 7 were 0, 0, 0, 0, 0, 0, and 0 with a mean of 0. 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. Estimated planetary A indices were 6, 3, 9, 4, 4, 3 and 3 with a mean of 4.6. Estimated mid-latitude A indices were 5, 3, 8, 5, 3, 2 and 1 with a mean of 3.9.
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/EX

Source: W1AW Bulletin via the ARRL.