QST de W1AW
Propagation Forecast Bulletin 9 ARLP009
From Tad Cook, K7RA
Seattle, WA March 2, 2018
To all radio amateurs
We’ve seen many days with no sunspots over the past year, especially in more recent times. Periods with more than three days of blank Sun include January 4-11, 2017, March 6-20, 2017, May 9-15, 2017, June 9-12, July 18-24, October 8-14, October 16-20, November 1-13, November 19-24, December 1-5, December 13-19, December 28, 2017 through January 3, 2018, January 20-29, 2018, and February 18-25. Sunspots have been visible every day, starting on February 26.
This reporting week (February 22-28) the average daily sunspot number was 6, up slightly from 5.6 over the previous seven days. Average daily solar flux declined from 70.1 to 68.3.
Average planetary A index, a geomagnetic indicator calculated from values measured at multiple magnetometers around the world, rose marginally from 10 to 10.4, and mid-latitude A index which is measured by a single magnetometer on Wallops Island, Virginia changed from 7.7 to 7.4. All of these values are moderate, or quiet. The most active day was February 27, when planetary A index was 19 and the mid-latitude A index was 14.
Spaceweather.com reports that Earth is exiting a solar wind stream which produced brief G-1 class geomagnetic storms (see February 27 in the previous paragraph). NOAA says (according to Spaceweather.com) that the chance of additional storms is 25% on March 1, declining to 15% on March 2. A new solar wind could appear on March 3.
How does this prediction figure from other sources?
From the NOAA 45-day forecast on March 1, predicted planetary A index is 7 on March 2, 5 on March 3-5, 8 on March 6, 5 on March 7-13, then 10, 8, 12, 15 and 18 on March 14-18, 5 on March 19-20, then 12, 15, 10, 8, 24, and 12 on March 21-26, then 5 on March 27 through April 9, then 10, 8, 12, 15 and 18 on April 10-14 and 5 on April 15.
So if any solar wind appears by March 3, the only correlation with the NOAA 45-day forecast would be the brief rise in planetary A index to 8 on March 6.
You can read daily updates of the NOAA forecast every afternoon (USA time) at ftp://ftp.swpc.noaa.gov/pub/forecasts/45DF/ .
Predicted solar flux from the same 45-day forecast is 68 and 70 on March 2-3, and 72 on March 4-8, then 73, 75, 76, 77, 75, 72, and 70 on March 9-15, 68 on March 16-26, then 70 and 75 on March 27-28, then 78 on March 29 through April 8, then 75, 72 and 70 on April 9-11, and 68 on April 12-15.
Considering the source, here is an excellent article on solar activity:
“Solar flares, intense bursts of radiation and light emitted from the Sun, are usually followed by a coronal mass ejection, which is a massive amount of solar material and the magnetic field energy being blown into space. Both of these phenomena can be dangerous under the right conditions. They can cause radiation poisoning, damage electronics on Earth and in orbit, and they can be a serious threat to the safety of astronauts. In an effort to better understand solar flares and CMEs, NASA created the Solar Dynamics Observatory to constantly watch the Sun. Launched back in 2010 the SDO is equipped with a suite of instruments that observe ultraviolet light, Doppler shifts, magnetic fields and more. In 2014, they were watching a large sunspot group in hopes of seeing an eruption, but it never happened and now three and a half years later, they think they know why.
“Back on October 24, 2014, they were keeping an eye on a sunspot group the size of Jupiter known as Active Region 12192. This complex grouping of magnetic fields was pegged as a site that had a high potential for solar activity and was the largest grouping of the last two solar cycles. The region did produce an X-class flare but never produced a CME, which usually follows a flare. Scientists wanted to know why so they looked at the data and found that there was a battle between two magnetic structures that ended up containing the eruption. The structures are being referred to as a twisted magnetic rope and a dense magnetic cage. The magnetic rope built up energy in the sunspot region and became unstable. It was able to lash through part of the magnetic cage and trigger a solar flare but in the end, it was not strong enough to break through the cage entirely and cause an eruption. This event has given scientists a wonderful opportunity to learn more about the Sun and how these events work. The data collected by SDO will be invaluable in expanding our knowledge of the Sun.”
Here is the geomagnetic activity forecast for March 2-27, 2018 from F.K. Janda, OK1HH. “Geomagnetic field will be:
- Quiet on March 3, 6-7, 10, 12-13, 20
- Mostly quiet on March 11
- Quiet to unsettled on March 2, 5, 19, 23-24, 27
- Quiet to active on March 4, 8-9, 14-16, 21-22, 25
- Active to disturbed on March 17-19, 26
“Amplifications of the solar wind from coronal holes: cannot be predicted for the period before March 10, but I do not expect any significant upsurge. Then solar wind will intensify on March (10,) 16-18, (19-20, 25-26).
- Parenthesis means lower probability of activity enhancement.
- With regard to ongoing changes, current forecasts remains less reliable especially in the first half of March.”
“F. K. Janda, OK1HH”
Don’t forget, the ARRL International SSB DX Contest is this weekend.
Here is the March 1 report from Dr. Tamitha Skov:
If you would like to make a comment or have a tip for our readers, email the author at, email@example.com .
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 February 22-28, 2018 were 0, 0, 0, 0, 16, 15, and 11, with a mean of 6. 10.7 cm flux was 68.4, 67.6, 68.2, 67.2, 69.8, 67.9, and 68.8, with a mean of 68.3. Estimated planetary A indices were 11, 16, 9, 4, 7, 19, and 7, with a mean of 10.4. Estimated mid-latitude A indices were 9, 11, 6, 2, 6, 14, and 4, with a mean of 7.4.