Guide to Solar/Geomagnetic Conditions
Geomagnetic Indices and Conditions
| 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 occured over the past 30 years, causing total dispruption 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 |
Good DX!
