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THE HANDYMAN'S GUIDE TO SOLAR/GEOMAGNETIC CONDITIONS
by Paul Harden, NA5N

Geomagnetic Indices and Conditions  |  Solar Flare Classifications  |  Sunspot/Active Region Classifications
 Quick Guide:  HF Propagation & Solar Indices
 

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GEOMAGNETIC INDICES AND CONDITIONS  (Kp and Ap Indices)

Kp
Index
Ap
Index
GEOMAGNETIC
FIELD CONDITIONS
HF NOISE AURORA
0 0 - 2 Very Quiet S1-S2 None
1 3 - 5 Quiet S1-S2 Very Low
2 6 - 9 Quiet S1-S2 Very Low
3 12 - 18 Unsettled S2-S3 Low
4 22 - 32 Active S3-S4 Moderate
5 39 - 56 MINOR Storm S4-S6 High
6 67 - 94 MAJOR Storm S6-S9 Very High
7 111 -154 SEVERE Storm S9+ Very High
8 179 -236 SEVERE Storm Blackout Extreme
9 300 -400 EXTREMELY SEVERE Blackout Extreme
Kp Planetary K-index, averaged over past 3 hours and tends to be a measure of current conditions
Ap Planetary A-index, 24-hour average and represents overall geomagnetic field conditions for the UTC day
HF Noise Approximate "S-meter" noise level <10 MHz
Aurora Approximate level of auroral activity
  • High conditions usually extends to: Latitude 45 deg. 
  • Very High conditions extends to about: Latitude 35 deg. 
  • Extreme conditions can extend to below: Latitude 35 deg.
Solar Wind averages 350-450 km/sec and density <10 p/cm^3
>500 km/sec or high density can trigger geomagnetic activity
Shock Wave from a solar flare or Coronal Mass Ejection (CME) arrives at the Earth about 55 hours after the solar event.
 

SOLAR FLARE CLASSIFICATIONS

FLARE CLASS TYPE OF FLARE HF RADIO EFFECTS RESULTING GEOMAGNETIC STORM
A Very small None None
B Small None None
C Moderate * Low absorption * Active to Minor
M Large * High absorption * Minor to Major
X Extreme * Possible blackout * Major to Severe
*Conditions cited if Earth is in trajectory of flare emissions
Flare class further rated from 1-9, ex. M1, M2, M3 ... M9
The larger the number, the larger the flare within that class
An X7-X9 is considered a "Grand daddy" flare. Only a few have occurred over the past 30 years, causing total disruption to communications, huge aurora's, power grid failures, etc.
Radio and x-ray emissions from a flare effect the Earth for the duration of the solar event, usually 30 minutes or less.
Earth is 8 light-minutes from the Sun.

 

SUNSPOT/ACTIVE REGION CLASSIFICATIONS 

SUNSPOT CLASS DESCRIPTION OF THE ACTIVE REGION POTENTIAL FOR FLARE ACTIVITY
Alpha Unorganized, unipolar magnetic fields Little threat, but watched for growth
Beta Bipolar magnetic fields between sun spots C class flares and possible large M class
Delta Strong, compact bipolar fields between spots  High potential for a M or X class major flare Major Flare Alert issued

 


From an e-mail posting by Paul Harden, NA5N, to the "Low Power Amateur Radio Discussion E-mail List"
06 January 1999 (5:13:15 PM)

1999 by Paul Harden, National Radio Astronomy Observatory, Socorro, New Mexico
"Above information may be freely used in other newsgroups, ham radio reflectors, non-profit journals, etc., without permission, providing credit is cited."


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