Friday, September 11, 2015

Solar activity is very low at the moment.  I'm posting a copy of the American Radio Relay league  (ARRL) solar report from their September 10, 2015 news letter.

The K7RA Solar Update
Tad Cook, K7RA, in Seattle, reports: The Australian Space Forecast Centre issued a Geomagnetic Disturbance Warning at 0132 UTC on September 8: "The effect of a high-speed solar wind stream from a coronal hole is keeping geomagnetic activity enhanced."
The NOAA Space Weather Prediction Center (SWPC) Daily Geomagnetic Data show the resulting high numbers indicating geomagnetic instability. On HF we might see higher absorption rates, but on VHF, we might see some interesting propagation modes.
Note that there are no mid-latitude or high-latitude A index numbers for September 8, 9, and 10. This is probably because geomagnetic activity was strong enough to knock the respective magnetometers out of service.
Frank Donovan, W3LPL, shared a link to the American Astronomical Society Nova article, "Witnessing Solar Rejuvenation," which proposes that Cycle 25 may be similar to Cycle 24.
Weak solar activity continues. The average daily sunspot number for September 3-9 was only 37.3, down 11 points from the previous 7 days. Average daily solar flux was 85.3, compared to 97 for the previous week.
Geomagnetic activity was strong, with the average planetary A index up from 19.4 to 27.1. The most active day was September 9, when the planetary A index was 59.
The latest solar flux prediction from USAF/NOAA has readings of 85, 90, and 100 on September 10-12; 105 on September 13-14; 110 on September 15-17; 115 on September 18-22; 110, 105, 100, and 95 on September 23-26; 90 on September 27-October 1, and 85 on October 2-7. Flux values then rise to 115 for October 15-19.
Predicted planetary A index is 28, 16, and 27 on September 10-12; 16, 10, and 8 on September 13-15; 5 on September 16-17; then 8, 20, and 10 on September 18-20; 5 on September 21-23; 15 and 10 on September 24-25; 5 on September 26-29; 8 and 18 on September 30-October 1; 12 on October 2-4; 8 on October 5; 5 on October 6-7; 8, 12, and 8 on October 8-10, and 10 on October 11-13.
Sunspot numbers for September 3 through 9 were 27, 36, 24, 38, 47, 40, and 49, with a mean of 37.3. The 10.7 cm flux was 86.5, 89.9, 85.4, 85.6, 83.7, 83.5, and 82.3, with a mean of 85.3. Estimated planetary A indices were 9, 20, 13, 14, 46, 29, and 59, with a mean of 27.1. Estimated mid-latitude A indices were 9, 18, 10, 12, 27, 24, and 31, with a mean of 18.7 (the September 8 and 9 numbers are my own estimates).

The sunspot number is a computed number using a formula that includes sunspots, sunspot groups.  The sunspot number in this report is 37.3.  For an approximation of the number of sunspots divide the sunspot number by 15.   In this case 2.48.  A pretty low number.

Sunspot Number Computation - 

Bill

No comments: