The K7RA Solar Update


At 2336 UTC on June 1, the Australian Space Weather Forecast Centre issued a Geomagnetic Disturbance Warning for June 2.

“The solar wind is expected to be influenced by a High-Speed Solar Wind Stream over the next 1 or 2 days. The source of this stream is a small coronal hole centered over the equator. Geomagnetic activity may reach active levels.” June 2 geomagnetic conditions are expected to be unsettled to active.

A new video from Dr. Tamitha Skov:

Average daily sunspot number for the recent reporting week (May 25-31) was down from 31.7 to 15.6, compared to the previous seven days. There were no sunspots on Tuesday, May 30, but on May 31 sunspot region 2661 appeared, and the sunspot number was 11, the lowest non-zero sunspot number possible, due to the arcane method for counting sunspots. 10 is assigned for every sunspot group, and 1 for each spot within that group. So, a sunspot number of 11 means there was one sunspot region or group, with only one sunspot.

At 0112 UTC on June 2, issued this alert regarding sunspot 2661: “ACTIVE SUNSPOT: On June 1st, a small but surprisingly active sunspot rotated over the sun’s eastern limb. In less than 24 hours, it has unleashed nearly a dozen C-class solar flares and hurled a pair of CMEs into space–an impressive display of fireworks. So far, none of the explosions have targeted Earth, but this could change in the days ahead as the active region rotates toward our planet. Visit for more information and updates.”

On June 1 the sunspot number rose from 11 to 18, which means the number of sunspots increased from 1 to 8. The total area of the sunspots doubled over those two days.

Average daily solar flux increased from 74.1 to 77.2.

Average planetary A index increased from 11 to 13.3, and average mid-latitude A index went from 11.7 to 10.6.

Predicted solar flux is 77 on June 2-3, 78 on June 4-8, 75 on June 9-10, 78 on June 11, 80 on June 12-21, 75 on June 22-23, 72, 78 and 72 on June 24-26, 70 on June 27 through July 5, 75 on July 6-7, 78 on July 8 and 80 on July 9-16.

Predicted planetary A index is 10, 15, and 8 on June 2-4, 5 on June 5-9, 10 and 12 on June 10-11, 8 on June 12-13, then 10, 12, 25 and 10 on June 14-17, 8 on June 18-19, 5 on June 20-24, 12 on June 25, 5 on June 26 to July 6, then 10 and 12 on July 7-8, 8 on July 9-10, then 10, 12, 25, and 10 on July 11-14 and 8 on July 15-16.

F.K. Janda, OK1HH sent this:

“Geomagnetic activity forecast for the period June 2-28, 2017

Geomagnetic field will be:
Quiet on June 2, 7, 9, 20-21, 27-28
Mostly quiet on June 17, 19
Quiet to unsettled June 5-6, 14, 18, 22, 26
Quiet to active on June 3-4, 8, 10, 12-13, 23, 25
Active to disturbed on June 11, (15), 16, 24

Amplifications of the solar wind from coronal holes are expected on June (3, 5-6,) 12-19, 26-27

– Parenthesis means lower probability of activity enhancement and/or lower reliability of prediction.

Note: as I will be sailing along the Bata channel next week, the next geomagnetic activity forecast will be issued up to the second week, i.e. on June 15.

F.K. Janda, OK1HH”

The latest forecast from USAF Space Weather Squadron for ARRL Field Day weekend (June 24-25) has solar flux on June 23-25 at 75, 72 and 78 and predicted planetary A index at 5, 5, and 12.

Both the planetary A index forecast and solar flux prediction for Field Day weekend has not changed since May 29.

On Sunday, May 28 during the CW weekend of the CQ World Wide WPX contest there was a large geomagnetic disturbance. Planetary A index was 51, and the High Latitude College A index (Fairbanks, Alaska) was 84. Those are both huge numbers.

I received two reports of enhanced 10, 15, and 20-meter propagation on Sunday. The first was from Ken Miller, K6CTW, of Rancho Cucamonga, California:

“Had an interesting experience last night during the CQ WPX CW contest. Fifteen and 20 meters appeared to be wide open (according to the spotting sites) between 0440 and 0540 UTC during a major geomagnetic storm. Normally, when spots appear at times or during conditions that do not favor simple antennas and low power, it has not been worth it to even check it out. However, I did turn on the rig and was able to work Indonesia (YE1K), New Zealand (ZM1A), Japan (JF3BFS), and the Marianas Islands/Tinian (NH0J) with only the 40 watts to a window-line fed inverted V. I’ll bet lots of others had the same wonderful experience.

“It would be great to find out how this happened because isn’t it a given that major geomagnetic storms totally disrupt the higher bands?”

I decided to run this by Carl Luetzelschwab, K9LA. His response:

“This is an excellent example of how we take a very complicated process (the effect of a geomagnetic storm on the ionosphere) and try to simplify it with one general statement.

“Ken’s observations during CQ WPX CW on 15 and 20-meters simply tell us that this statement isn’t 100% true. Yes, in general, the high latitude F2 region is adversely affected by elevated K indices, but the low latitude F2 region can be enhanced. And the mid latitude F2 region could be anywhere in between depending on where we are in the geomagnetic storm. His paths to YB, ZL and KH0 are relatively low/mid latitude paths from his California home, and suggest what happened was an enhancement (or at least no change) for a short period. The JA contact gets to the highest latitude (about 50 degrees north geographic), but apparently it wasn’t affected too much for some of the time.

“Here is a prediction from SWPC’s STORM model ( for August 5 and 6 of 2011 based on the geomagnetic storm at that time. [Unfortunately that attachment is an image that K9LA saved back in 2011 from that same URL, and is not available there or anywhere else. If you want a copy, email me at [email protected] with the subject “K9LA attachment from ARLP022” –K7RA] This model integrates the last eleven Kp indices (the last eleven a-sub-p indices, which are the linear equivalents of the Kp index) to predict what the F2 region is doing compared to the quiet F2 region. Note that all latitudes of the northern hemisphere and the high latitudes of the southern hemisphere were predicted to be adversely impacted, while the mid latitudes of the southern hemisphere were predicted to be kind of a wash and the low latitudes of the southern hemisphere were predicted to be somewhat enhanced. Ionosonde data generally confirms this, but even the STORM model may not capture the very short-term dynamics of the entire real-world ionosphere.

“The bottom line is a major geomagnetic storm doesn’t necessarily totally disrupt the higher bands throughout the entire worldwide ionosphere. Two corollaries are that a single K index (as used by W6ELProp and ICEPAC) is inadequate to explain the entire real-world ionosphere under disturbed conditions, and even using the STORM model may not predict the short-term changes.

“These short-term events are why we don’t have a daily model of even the quiet ionosphere – our understanding is statistical in nature over a month’s time frame.”

Tim Goeppinger, N6GP of Tustin, California sent this note concerning this very same event:

“The West Coast had an interesting opening to Japan and Guam on 10 meters around 0400z on May 28 during the CQ WPX Contest. I recorded some audio and made this YouTube video about these unusual conditions.”

Carl, K9LA also commented on Tim’s report:

“That 10-meter opening in your other e-mail looks like it was about the same time as Ken’s observations on 20 and 15-meter. Always keep your ears open during a geomagnetic storm – you may be surprised. Right now we’re off to Seaside, Oregon for SeaPac. I’ll probably take a closer look at the 10-meter comments after we get back.”

For more information concerning radio propagation, see the ARRL Technical Information Service at For an explanation of numbers used in this bulletin, see

An archive of past propagation bulletins is at More good information and tutorials on propagation are at

Monthly propagation charts between four USA regions and twelve overseas locations are at

Instructions for starting or ending email distribution of ARRL bulletins are at

Sunspot numbers for May 25 through 31, 2017 were 19, 22, 21, 20, 16, 0, and 11, with a mean of 15.6. 10.7 cm flux was 76.1, 80.2, 81.9, 78.8, 75.8, 73.7, and 74.1, with a mean of 77.2. Estimated planetary A indices were 4, 3, 14, 51, 10, 7, and 4, with a mean of 13.3. Estimated mid-latitude A indices were 4, 3, 14, 32, 10, 6, and 5, with a mean of 10.6.


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