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
|