Duration of event (h) | Once per year | Once per 10 years | Once per 100 years | Once per 1000 years | Reference |
---|
dfmin ≥ 2.5 MHz | 1.6 | 3.6 | 6.8 | 11.9 | Figure 7 ionosonde |
dfmin ≥ 3.5 MHz | 1.1 | 2.9 | 6.1 | 11.5 | Figure 7 ionosonde |
“B”-event | 0.63 | 1.8 | 4.0 | 7.4 | Figure 7 ionosonde |