ARRL

Secure Site Login

News

The K7RA Solar Update

04/21/2017

This just in from the Australian Space Forecast Centre at 2349 UTC on April 20, 2017:

Recurrent coronal hole is expected to be geoeffective.

INCREASED GEOMAGNETIC ACTIVITY EXPECTED
DUE TO CORONAL HOLE HIGH SPEED WIND STREAM
FOR 23 APRIL 2017

GEOMAGNETIC ACTIVITY FORECAST
23 Apr:  Active to Minor Storm


Spaceweather.com reported old sunspot AR2644 returned after a 2-week trip around the Sun, and exploded on April 18. The resulting CME should miss Earth, but as this active region moves into a geo-effective position we could see some geomagnetic disturbance in the next few days.

Average daily sunspot numbers declined from 16.6 last week to 8.6 in this reporting week, April 13-19. Average daily solar flux increased from 73.8 to 76.5.

Geomagnetic indicators were lower this week. Average planetary A index declined from 10.6 to 8, while average mid-latitude A index was 6.3, down from 9.3 the previous seven days.

Predicted solar flux is 85 on April 21-27, 80 on April 28 to May 1, 75 on May 2-13, 83 and 88 on May 14-15, 90 on May 16-18, 85 on May 19-24, 80 on May 25-28, and 75 on May 29 through June 4.

Predicted planetary A index is 12, 8, 40 and 30 on April 21-24, 20 on April 25-27, then 15, 10, 5 and 20 on April 28 through May 1, 10 on May 2-4, 15 on May 5-6, then 5 and 8 on May 7-8, 5 on May 9-13, 20 on May 14, 15 on May 15-16, 10 on May 17, 5 on May 18-19, then 35, 25, 18, 20 and 25 on May 20-24, then 12, 8, 5 and 18 on May 25-28, and 10 on May 29 through June 4.


František K. Janda, OK1HH, of the Czech Propagation Interest Group sent us his geomagnetic activity forecast for the period April 21-May 17, 2017. 2017 marks the 40th year Franz has been writing these bulletins.

Geomagnetic field will be:
Quiet on April 22, 30, May 13
Mostly quiet on April 29, May 8
Quiet to unsettled April 21, May 3, 7, 10-12, 14-15
Quiet to active on April 24-25, 27-28, May 1-2, 4-5, 8, 16
Active to disturbed on April 23, 26, May 6, 17

Increasing solar wind from coronal holes are expected on April (21-22,) 23-28, May (1-4,) 7-8, (9-11,) and 18-19.

Remark:
- Parenthesis means lower probability of activity enhancement and/or lower reliability of prediction.



And from another Czech resource, a near term geo-forecast from Thomas Bayer of the Budkov Observatory:

Geomagnetic activity forecast for the period April 21-April 27, 2017

Quiet: Apr 21-22
Unsettled: Apr 22-23, 25-27
Active:   Apr 23-25
Minor storm: possible Apr 23-24
Major storm: 0
Severe storm: 0

Geomagnetic activity summary:

Until the nearest Saturday, April 22, we expect quiet to unsettled conditions. Between Sunday, April 23, and Monday, April 24, we expect active episode arrival caused by present equatorial coronal hole. During these two days, storming effect is possible.

The following days, we expect at most unsettled conditions only with isolated active episodes. The last day of the forecast period, we expect geomagnetic activity decrease to quiet to unsettled level.

Tomas Bayer
RWC Prague
Institute of Geophysics of the ASCR, Prague
Department of Geomagnetism
Budkov observatory (BDV)

 

According to this, we are due for more low solar activity, but there is a chance of C-class and M-class flares: http://www.spaceref.com/news/viewsr.html?pid=50058


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 April 13 through 19, 2017 were 12, 11, 11, 0, 0, 12, and 14, with a mean of 8.6. 10.7 cm flux was 73.5, 72.9, 73, 74.5, 75.2, 85.6, and 80.9, with a mean of 76.5. Estimated planetary A indices were 5, 14, 7, 4, 4, 7, and 15, with a mean of 8. Estimated mid-latitude A indices were 4, 10, 5, 4, 3, 6, and 12, with a mean of 6.3.



Back