[PBARC] A index & K index and propagation

[WOLF, EARNEST G]

HF Shortwave Radio Propagation Information - A Index and K Index
(These numbers are given on WWV at 18 minutes after the hour)

A Index and K Index 
The Earth's magnetic field is continuously monitored by a network of
magnetometers. These readings are converted into the A and K index
values. 

The K index is computed once every three hours (eight times a day) and
the values can range from 0 to 9, with 0 being inactive, and 9
representing an extreme severe storm condition. The values are
quadi-logarithmic. 

K = 0 Inactive 
K = 1 Very quiet 
K = 2 Quiet 
K = 3 Unsettled 
K = 4 Active 
K = 5 Minor storm 
K = 6 Major storm 
K = 7 Severe storm 
K = 8 Very severe storm 
K = 9 Extremely severe storm 

The A index is linear, and is computed from the eight previous K index
values. It ranges from 0 (quiet) to 400 (severe storm). 

A = 0 - 7 Quiet 
A = 8 - 15 Unsettled 
A= 8 - 15 Unsettled 
A = 16 - 29 Active 
A = 30 - 49 Minor storm 
A = 50 - 99 Major storm 
A = 100 - 400 Severe storm 

Generally, propagation conditions are best when the A index is 15 or
lower, and the K index is 3 or lower. 

Besides causing auroral activity, high geomagnetic field conditions can
affect the electrons in the ionosphere, reducing the maximum usable
frequency (MUF). 

Thanks,
Glenn

Phone:
Internal: 8.760.3948
External: 870.541.3948

Address:
Internal: A-SOC-1
External: Entergy
          5201 W Barraque
          Pine Bluff, AR 71602

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