The K7RA Solar Update
We saw a string of zero-sunspot days over the past couple of weeks, but this week saw a brief but significant sunspot that lasted only a couple of days. Sunspot 990 emerged as a tiny speck over April 14-15, but it was definitely a Solar Cycle 24 spot. Not only was the polarity of this region correct for the new Cycle, but it was far north above the Sun's equator, which is what we expect for a sunspot from an emerging solar cycle. The only previous Cycle 24 activity was close to the solar equator.
Sunspot numbers for April 10-16 were 0, 0, 0, 0, 11, 12 and 0 with a mean of 3.3. The 10.7 cm flux was 67.9, 67.1, 68.2, 69.3, 68.5, 69.2 and 69.5 with a mean of 68.5. Estimated planetary A indices were 8, 4, 11, 7, 2, 5 and 15 with a mean of 7.4. Estimated mid-latitude A indices were 6, 3, 8, 6, 2, 3 and 9, with a mean of 5.3. Geophysical Institute Prague predicts quiet conditions April 18, quiet to unsettled April 19, quiet April 20, quiet to unsettled April 21, active April 22-23 and unsettled to active April 24.
For some unknown reason, there were no mid-latitude geomagnetic readings from the Fredericksburg, Virginia magnetometer on April 10, so I estimated the A index for that day as 6. This was done by looking at the Boulder Colorado readings for April 9-11 and the Fredericksburg readings for both April 9 and April 11.
Fredericksburg is about 1500 miles east of Boulder, and about 2.4 degrees south in terms of latitude. Each location produces a mid-latitude K and A index. The Fredericksburg numbers are reported at the end of each ARRL Propagation Bulletin, and the Boulder numbers are what you hear on WWV at 18 minutes after the hour when they give the Geophysical Alert Message. You can see the current message and browse the archives at the Space Weather Prediction Center's Web site. NOAA predicts quiet geomagnetic conditions over the next few days, with geomagnetic upset occurring on April 23. The chance of returning sunspots increases beginning April 20; the best bet for more spots is April 26-28.
Stan Whiteman, W1MDZ, of Danforth, Maine, wrote to say he has set up a telescope with the proper filters for viewing sunspots. Of course, now that he has it finally set up, there were no sunspots to see. Danforth is a community in East Central Maine, across Grand Lake from New Brunswick, Canada. Stan turns 87 this year. Stan didn't mention this, but I happen to know that he was stationed in Japan after World War II and got to meet Dr Hidetsugu Yagi, the originator of the Yagi antenna.
Last week we mentioned the storm brewing when, a couple of months ago, a daily business publication ran an article suggesting the Sun is on the verge of a Maunder Minimum, a many decades-long period with very few sunspots. They quoted Dr Kenneth Tapping of Canada's Dominion Radio Astrophysical Observatory (DRAO) in Penticton, British Columbia -- quotes that he says are incorrect and misleading.
Ken has produced a very good response, complete with graphs demonstrating that this minimum we are currently experiencing between Solar Cycles is nothing unusual. You can get a copy via e-mail by sending a request. Every e-mail sent to this address, no matter what the content, will receive a copy of Dr Tapping's report via return e-mail.
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.