Zero, zero, zero sunspots for 18 straight days now. A single sunspot appeared briefly October 6-7, no sunspots for four days prior, one sunspot for the final few days of September, and none for the three whole weeks prior to that. Until recently, many of us thought the solar cycle minimum occurred in March of this year. You can see a table of projected smoothed numbers with a minimum in March 2007 here. Sunspot numbers for October 18-24 were 0, 0, 0, 0, 0, 0 and 0 with a mean of 0.The 10.7 cm flux was 68.2, 67.3, 66.9, 67.2, 66.7, 67.1 and 67.5 with a mean of 67.3. Estimated planetary A indices were 10, 15, 12, 4, 5, 7 and 3 with a mean of 8. Estimated mid-latitude A indices were 11, 11, 8, 5, 3, 6 and 2 with a mean of 6.6.This year we began looking at a table of 3-month sunspot number averages, and for a while the data seemed to support a March minimum. But then we hit this longer period of no sunspots, and the 3-month average dropped again. You can see the most recent table in ARLP041 here. Note the 10.2 average assigned to August (which is the middle of the July-September period the 3-month average is based on) is lower than March, which was 11.2. With such a long period of so few sunspots, at the beginning of November we might see a much lower 3-month average. This is because the sum of all the daily sunspot numbers from August 1 until now is only 492, and if we still see no sunspots through next Wednesday, that total divided by the number of days for August-September-October (92) is only 5.4.
So how low is 5.4, compared to the last solar minimum? I looked at averages between December 1995-April 1997, and the only time the 3-month average of sunspot numbers dipped below 10 was in 1996, with 9.9 in March and 8.7 in September:
Dec 95 16.7
Jan 96 14.7
Feb 96 13.1
Mar 96 9.9
Apr 96 10.9
May 96 13.0
Jun 96 14.6
Jul 96 17.5
Aug 96 12.4
Sep 96 8.7
Oct 96 10.2
Nov 96 14.2
Dec 96 16.4
Jan 97 11.7
Feb 97 11.3
Mar 97 16.4
Apr 97 22.6
But this doesn’t really tell us when solar activity will increase, just that we are currently seeing lower overall sunspot activity than we did at the last solar minimum 11 years ago.
With no sunspots, it is sometimes amazing what hams can work on the air. Geomagnetic activity increased on October 25 due to solar wind, and just ahead of that Dick Hanna, K3VYY, of Beaver Falls, Pennsylvania, worked two Florida stations on 28.37 MHz at 0100 UTC, two and a half hours after his local sunset. This is an unusual time for propagation over this path, which would normally occur during the middle of the day with the sunspot number over 100.
Jon Jones, N0JK, of Wichita, Kansas, reported some good E skip on 6 meters for around 2 hours on October 20, beginning at 0115 UTC. He worked VE3DXP/W7 in Las Vegas, and K7ICW was also loud from New Mexico. He also heard some double-hop E-skip from Washington State and Florida. Jon commented that E-skip is rare in October.
During an hour at lunch on October 25, Chip Margelli, K7JA, reported from Southern California: “Ten meters opened up from California to Europe and Africa for the first time in a very long time. Besides the loud Caribbean stations — CT1CJJ, CU2AF, GM3POI, MM0SJH, CU3EQ, C52C, 5H3EE — were great finds on 28 MHz between 1900-2000 UTC”. Dan Eskenazi, K7SS, in Seattle reported that mid-day West Coast time, he heard C52C on 10 meters and heard Tom Owens, K7RI, work him.
This weekend is the CQ World Wide DX Phone Contest, and geomagnetic activity should calm by the start of the event. Predicted planetary A index for October 26-31 is 20, 12, 10, 15, 10 and 8. Geophysical Institute Prague predicts unsettled to active conditions October 26, unsettled October 27, quiet to unsettled October 28, unsettled October 29-30, quiet to unsettled October 31 and quiet conditions on November 1.
You can get 45 day planetary A index and solar flux predictions here. A new one is issued daily after 2100 UTC, but often there is a delay before the link to the new forecast is posted. To get around this, after 2100 UTC if the link to that day’s forecast hasn’t appeared, try changing the URL for the previous day’s forecast to what it would be for the current date. For instance, the URL for the October 25 forecast was www.swpc.noaa.gov/ftpdir/forecasts/45DF/102545DF.txt. After 2100 UTC on October 26, if the link to the latest forecast hasn’t appeared, change the URL to www.swpc.noaa.gov/ftpdir/forecasts/45DF/102645DF.txt and see if it is available yet.
Thomas Giella, KN4LF of Lakeland, Florida reports that he has a propagation forecast available to paid subscribers. You can learn about it here.
For more information concerning radio propagation, see the ARRL Technical Information Service. A detailed explanation of the numbers used in this bulletin can be found here. An archive of past propagation bulletins can be found here. Monthly propagation charts between four USA regions and 12 overseas locations are available at here.
Amateur solar observer Tad Cook, K7RA, 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. Readers may contact the author via e-mail.