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Solar Flux ranges from 50 (low) to 300 (high). Sustained high values for SF indicates stronger ionization, hence higher MUF. Values above 150 (sustained) are prime for HF.
K values range from 0 (low) to 9 (high) indicating degree to which propagation will be disturbed / MUF depressed by geomagnetic factors. Low values are desirable.
Relationship between "K" and "a" Indices
| Ap Index | Kp Index | Comments |
| 0 | 0 | Quiet |
| 4 | 1 | Quiet |
| 7 | 2 | Unsettled |
| 15 | 3 | Unsettled |
| 27 | 4 | Active |
| 48 | 5 | Minor storm |
| 80 | 6 | Major storm |
| 132 | 7 | Severe storm |
| 208 | 8 | Very major storm |
| 400 | 9 | Very major storm |