We just saw 15 straight days with visible sunspots, but it ended on Wednesday, August 29 with a sunspot number of zero. There were also no sunspots seen on Thursday, the following day.
According to Spaceweather.com, in 2018 so far, we’ve seen 134 days (55 percent) with no sunspots. For all last year, in 2017 there were 104 days (28 percent overall) with no sunspots. During the last solar minimum, there were 528 days with no sunspots in 2008-2009, or about 72.2 percent of the days over the entire two years with no activity.
The past reporting week (August 23-29) saw the average daily sunspot number rise to 17.7, from 13 over the prior week. Average daily solar flux rose from 67.5 to 70.6. Average daily planetary A index rose from 10.1 to 19.9, while average mid-latitude A index rose from 10.4 to 13.4.
For HF operations, we want to see high solar flux and sunspot numbers, and low A index, a measure of geomagnetic instability. On Sunday, August 26 we saw high A index numbers from an unexpected crack, opening in Earth’s magnetic field. Solar wind spewed forth and the planetary A index rose to 76. During this period the planetary K index (a component of the A index) rose to 7 over a six-hour period. Seven is a big K index number.
The middle latitude A index for the day was 34. But Alaska felt the full force of the geomagnetic storm, with an A index in Fairbanks (the College A index) of 90, a very high number. The College A index hasn’t been that high since September 8, 2017 when it reached 110.
Spaceweather.com reported new sunspot group 2720 is the first large spot of the next solar cycle, Cycle 25. The magnetic polarity is reversed from the polarity of sunspots in Cycle 24.
Carl Luetzelshwab, K9LA, noted that the latest spot was not a high latitude event, which would be expected for a new cycle spot. Carl said there was a new spot possibly from the new cycle on April 10, but it was very short duration. Way back on December 20, 2016 the first spot from the new cycle appeared.
Predicted solar flux is 68 on August 31 through September 7, 67 on September 8-9, 68 on September 10-11, 69 on September 12, 70 on September 13-22, 69 on September 23-25, 67 and 68 on September 26-27, 67 on September 28 through October 6, then 68, 68 and 69 on October 7-9, and 70 on October 10-14.
Predicted planetary A index is 5 on August 31 through September 2, 8 on September 3-4, 5, 5, and 8 on September 5-7, 5 on September 8-10, then 15 on September 11-12, 12 on September 13-14, then 10, 12 and 8 on September 15-17, 5 on September 18-21, then 12, 18, 12, 10, 8 and 5 on September 22-27, 8 on September 28-29, 5 on September 30 through October 3, 8 on October 4, 5 on October 5-7, then 18 on October 8, 15 on October 9-10, 12 on October 11, 10 on October 12-13, and 8 on October 14.
Geomagnetic activity forecast for the period August 31 to September 26, 2018 from F.K. Janda, OK1HH.
Geomagnetic field will be:
Quiet on September 2, 9, 17, 26
Quiet to unsettled on September 5-6, 10, 18, 24-25
Quiet to active on August 31, September 1, 8, 13-16, 18-20,
Unsettled to active on September 3-4, 7, 11-12, 23,
Active to disturbed on September 21-22
Solar wind will intensify on September (10-11,) 14-17, (21,) 22-24, (25)
Remarks:
- Parenthesis means lower probability of activity enhancement.
- Reliability of predictions remains low.
Comment:
I was asking around why no one (myself, though I hesitated) foresaw an immediate massive disturbance roughly one week ago. The answer is simple. In the analysis I neglected the freshest evolution on the Sun, especially the development in the active area 2720, which was much closer to the southern prick of north coronal polar hole than the previously dominant group 2719.
F.K. Janda, OK1HH
Here is an interesting article on the possible transition to Cycle 25: https://bit.ly/2wt0WEe
I found a possible source of confusion in the fourth paragraph of that article, “the transition period from Solar Cycle 24 to Solar Cycle 25 was deep and profound" should say Cycle 23 to Cycle 24. I believe we are currently about to enter the transition to Cycle 25.
The latest from Dr. Skov: “It comes as no surprise that I have mixed feelings about the collision of Space Weather and terrestrial weather this past week. On the one hand, aurora photographers got an unforgettable show over the weekend, with aurora views that rivaled the best from the biggest solar storms of this solar cycle. Indeed, the pictures are mesmerizing. On the other hand, however, I find myself squirming when I return to the moment I realized this solar storm was going to be worse than my worst-case predictions. The radio communications blackouts and poor GPS reception were painful to watch unfold during the largest hurricane to threaten Hawaii in more than 25 years.
“In the end, everyone seems to agree that Hurricane Lane was a close call. Luckily, it didn’t make landfall, but it’s slow speed and intensity was enough to cause massive flooding on the big island, leaving some people stranded and without the comforts of home. Had the situation been worse, amateur radio operators would have been a life line of communications, while GPS-enabled search and rescue drones would have done life-saving reconnaissance. Thank goodness that was not necessary. I remember last year when Hurricane Irma hit Puerto Rico, a set of extreme Space Weather events made amateur radio communications and satellite phones nearly inoperable for a week! We dodged a bullet this time. But we cannot count on that. With hurricanes and cyclones on the rise, there is little doubt that a ‘perfect storm,’ in which Space Weather exacerbates an already bad situation, will return sooner than we think.
“In this week's forecast, I do my best to highlight the beauty of this recent solar storm, but also the danger. As the weather quiets down again and things return to "business as usual," I hope the memory of this perfect storm remains. It may not be all that often that Space Weather and Earth weather conspire like this, but when they do, we need to be sure we're ready.”
Here is her latest video: https://youtu.be/7qs2RLdHDqU
For more information concerning radio propagation, see the ARRL Technical Information Service at http://arrl.org/propagation-of-rf-signals. For an explanation of numbers used in this bulletin, see http://arrl.org/the-Sun-the-earth-the-ionosphere.
An archive of past propagation bulletins is at http://arrl.org/w1aw-bulletins-archive-propagation. More good information and tutorials on propagation are at http://k9la.us/.
Monthly propagation charts between four USA regions and twelve overseas locations are at http://arrl.org/propagation.
Instructions for starting or ending email distribution of ARRL bulletins are at http://arrl.org/bulletins.
Sunspot numbers for August 23 through 29, 2018 were 15, 29, 31, 26, 12, 11, and 0, with a mean of 17.7. 10.7 cm flux was 69.5, 72.4, 71.6, 71.1, 69.6, 69.8, and 70.5, with a mean of 70.6. Estimated planetary A indices were 5, 5, 11, 76, 26, 10, and 6, with a mean of 19.9. Estimated mid-latitude A indices were 5, 7, 12, 34, 20, 9, and 7, with a mean of 13.4.
