23 March, 2019
Following a month of no sunspots in February, solar
activity returned on March 5-12, then disappeared over five days,
returning last week on March 18-20.
But our reporting week (always Thursday through the
following Wednesday) ended with a bang when the daily sunspot number
rose to 28 on March 20, the first day of Spring. Sunspot numbers have
not been as high since last August, when the sunspot numbers were 29, 31
and 26 on August 24-26.
Thursday, March 21 saw the sunspot number rise to
49, and the sunspots cover 220 millionths of the solar hemisphere. The
last time the sunspot number was as high was on June 20, 2018 when it
was 54. Sunspot area hasn't been higher than 220 millionths hemisphere
since February 12, 2018, when it was 230 millionths.
There are now two visible sunspot groups, AR2735 and AR2736.
A coronal mass ejection exploded out of new sunspot
AR2736 on March 20, causing a temporary HF blackout in Southern Europe
and in Africa. Parts of this CME should arrive at Earth late on March 22
or 23.
Also on March 20 the solar flux was 76.8, a number
higher than any solar flux value since last June, when it was 77.1 on
June 23. On March 21 the solar flux was 80.1. Does this signal a
turnaround for Solar Cycle 24? Too early to tell, but those numbers are
certainly encouraging.
Average daily sunspot numbers declined slightly
from 9.9 in the previous seven days to 8 this week, March 14-20. Average
daily solar flux went from 70.9 to 70.7.
Average planetary A index rose from 5.1 to 8.1, and average middle latitude A index went from 3.9 to 6.3.
Predicted solar flux is 80 on March 22-23, then 77,
76, and 74 on March 24-26, 70 on March 27-29, 71 on March 30 through
April 9, 70 on April 10, 69 on April 11-24, 70 on April 25, and 71 on
April 26 through May 5.
Predicted planetary A index is 5 on March 22, then 24
and 25 on March 23-24, 8 on March 25-26, 15 and 12 on March 27-28, 8 on
March 29-30, 5 on March 31 and April 1, 8 on April 2-3, 5 on April 4-11,
15 on April 12, 5 on April 13-15, 10 on April 16, 5 on April 17-21,
then 10, 26, 24, 12 and 8 on April 22-26, 5 on April 27-28, 8 on April
29-30, and 5 on May 1-5.
At 0050 UTC on March 21, The Australian Space
Weather Forecast Centre issued a geomagnetic disturbance warning: "On 23
March a CME associated with a C4.8 flare occurred on 20 March is
expected to arrive at Earth. This may result in an increase in the
global geomagnetic activity up to Minor Storm levels. Isolated Major
Storm levels are also possible."
Just released on Wednesday from Dr. Tamitha Skov, WX6SWW:
https://youtu.be/AmUNgxcxvGg
Geomagnetic activity forecast for the period March 22-April 20, 2019 from F.K. Janda, OK1HH.
"Geomagnetic field will be:
Quiet on March 31, April 11, 16, 18-19
Quiet to unsettled on March 22, 25, April 1-4, 11-12
Quiet to active on March 26, 31, April 6-10, 15 Unsettled to active on
March 24, 27, 29-30, April 5, 13-14, 17 Active to disturbed on March 23,
28
"Solar wind will intensify on March (22,) 23-24, (25-30,) April (2, 12-13, 15-16).
"Parenthesis means lower probability of activity enhancement."
Steve Sacco, NN4X of Saint Cloud, Florida mentioned a big meteor blast last December. It released 173 kilotons on December 18:
https://cneos.jpl.nasa.gov/fireballs/
He checked his log, and found possible enhancement
over that path on 30 meters using FT8 mode to Japan, UA0, China and
United Arab Emirates. Later he worked BG2AUE on 80 meters at 1247 UTC.
If you would like to make a comment or have a tip for our readers, email the author at k7ra@arrl.net.
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 March 14 through 20, 2019 were
0, 0, 0, 0, 13, 15, and 28, with a mean of 8. 10.7 cm flux was 70.1,
69.6, 69.5, 69.3, 70, 69.7, and 76.8, with a mean of 70.7. Estimated
planetary A indices were 7, 7, 12, 16, 3, 7, and 5, with a mean of 8.1.
Middle latitude A index was 6, 5, 7, 14, 2, 5, and 5, with a mean of
6.3.
• All propagation reports can be found at:
http://www.southgatearc.org/propagation
