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| NOAA Space Weather Scale for Geomagnetic Storms |
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| Category | | | |
-------------------| | Physical | Avg. Frequency |
|Scale | Descriptor| Effect | Measure |(cycle=11 years)|
|------|-----------|---------------------------|----------|----------------|
| | | number of |
| | Planetary| storm events |
| Geomagnetic Storms | K Index | (number of |
| | (Kp) | storm days) |
|------|-----------|---------------------------|----------|----------------|
| G5 | Extreme | HF (high frequency) radio | Kp = 9 | 4 per cycle |
| | | propagation may be | | (4 days/cycle) |
| | | impossible in many areas | | |
| | | for one to two days, | | |
| | | satellite navigation may | | |
| | | be degraded for days. | | |
|------|-----------|---------------------------|----------|----------------|
| G4 | Severe | HF radio propagation | Kp = 8 | 100 per cycle |
| | | sporadic, satellite | | (60 days/cycle)|
| | | navigation degraded for | | |
| | | hours. | | |
|------|-----------|---------------------------|----------|----------------|
| G3 | Strong | HF radio may be inter- | Kp = 7 | 200 per cycle |
| | | mittent, intermittent | |(130 days/cycle)|
| | | satellite navigation. | | |
|------|-----------|---------------------------|----------|----------------|
| G2 | Moderate | HF radio propagation can | Kp = 6 | 600 per cycle |
| | | fade at higher latitudes. | |(360 days/cycle)|
| | | latitudes. | | |
|------|-----------|---------------------------|----------|----------------|
| G1 | Minor | Minor impact on HF radio | Kp = 5 | 1700 per cycle |
| | | propagation at higher | |(900 days/cycle)|
| | | latitudes. | | |
|------|-----------|---------------------------|----------|----------------|
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| NOAA Space Weather Scale for Solar Radiation Storms |
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| Category | | | |
-------------------| | Physical | Avg. Frequency |
|Scale | Descriptor| Effect | Measure |(cycle=11 years)|
|------|-----------|---------------------------|----------|----------------|
| | | number of |
| |Flux level| storm events |
| Solar Radiation Storms | >= 10 MeV| (number of |
| | (ions)* | storm days) |
|------|-----------|---------------------------|----------|----------------|
| S5 | Extreme | Complete blackout of HF | 10^5 | Fewer than |
| | | communications possible | | 1 per cycle |
| | | through the polar regions,| | |
| | | and position errors make | | |
| | | satellite navigation | | |
| | | extremely difficult. | | |
|------|-----------|---------------------------|----------|----------------|
| S4 | Severe | Blackout of HF communi- | 10^4 | 3 per cycle |
| | | cations through the polar | | |
| | | regions and increased | | |
| | | navigation errors over | | |
| | | several days are likely. | | |
|------|-----------|---------------------------|----------|----------------|
| S3 | Strong | Degraded HF radio propa- | 10^3 | 10 per cycle |
| | | gation through the polar | | |
| | | regions and navigation | | |
| | | position errors likely. | | |
|------|-----------|---------------------------|----------|----------------|
| S2 | Moderate | Small effects on HF radio | 10^2 | 25 per cycle |
| | | through the polar regions | | |
| | | and navigation at polar | | |
| | | caps possibly affected. | | |
|------|-----------|---------------------------|----------|----------------|
| S1 | Minor | Minor impact on HF radio | 10^1 | 50 per cycle |
| | | in the polar regions. | | |
|------|-----------|---------------------------|----------|----------------|
*Flux levels are 5 minute averages. Flux in particles x s-1 x ster-1 x cm-2.
Based on this measure, but other physical measures are also considered.
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| NOAA Space Weather Scale for Radio Blackouts |
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| Category | | | |
-------------------| | Physical | Avg. Frequency |
|Scale | Descriptor| Effect | Measure |(cycle=11 years)|
|------|-----------|---------------------------|----------|----------------|
| | | number of |
| |GEOS X-ray| events |
| Radio Blackouts | by class | (number of |
| | and flux*| storm days) |
|------|-----------|---------------------------|----------|----------------|
| R5 | Extreme | Complete HF radio blackout| X20 | Fewer than |
| | | on the entire sunlit side | (2x10^-3)| 1 per cycle |
| | | of the Earth lasting for | | |
| | | several hours. Increased | | |
| | | satellite navigation | | |
| | | position errors on the | | |
| | | sunlit side of the Earth. | | |
|------|-----------|---------------------------|----------|----------------|
| R4 | Severe | HF radio communication | X10 | 8 per cycle |
| | | blackout on most of the | (10^-3) | (8 days/cycle) |
| | | sunlit side of Earth for | | |
| | | one to two hours. Minor | | |
| | | disruptions of satellite | | |
| | | navigation possible on | | |
| | | sunlit side of the Earth. | | |
|------|-----------|---------------------------|----------|----------------|
| R3 | Strong | Wide area blackout of HF | X1 | 175 per cycle |
| | | radio communication, loss | (10^-4) |(140 days/cycle)|
| | | of radio contact for about| | |
| | | an hour on sunlit side of | | |
| | | the Earth. | | |
|------|-----------|---------------------------|----------|----------------|
| R2 | Moderate | Limited blackout of HF | M5 | 350 per cycle |
| | | radio communication on | (5x10^-5)|(300 days/cycle)|
| | | sunlit side, loss of radio| | |
| | | contact for tens of | | |
| | | minutes. | | |
|------|-----------|---------------------------|----------|----------------|
| R1 | Minor | Weak or minor degradation | M1 | 2000 per cycle |
| | | of HF radio communication | (10^-5) |(950 days/cycle)|
| | | on sunlit side, occasional| | |
| | | loss of radio contact. | | |
|------|-----------|---------------------------|----------|----------------|
*Flux, measured in the 0.1-0.8 nm range, in W x m-2.
Based on this measure, but other physical measures are also considered.
.
