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Table 1 Estimation of scale of space weather events with occurrence probabilities of daily to several times per year, once per year, and once per 10, 100, and 1000 years

From: Space weather benchmarks on Japanese society

Phenomena Parameter Daily–several per year Once per year Once per 10 years Once per 100 years Once per 1000 years
Solar flare X-ray peak flux M1–X1 X7.6 X12 X44 X101
Energy [erg]  < 2.0 × 1030 1.0 × 1031 1.0 × 1032 1.0 × 1033 1.0 × 1034
Coronal mass ejection (CME) Velocity [km/s] 250–450 2000 3000 3800–4500 4700–6600
Kinetic energy [erg]     4.4 × 1033 9.8 × 1033
Solar energetic particles (SEPs) Fluence (≥ 10 MeV) [1010 cm−2] at GEO    ~ 0.1  ~ 1.0  ~ 2.4–5.1  ~ 3.8–14
EII [%・h]     ~ 190  ~ 6600  ~ 223,000
Solar radio burst [sfu] Very high frequency (VHF, 30–300 MHz)      < 2.8 × 109  
Ultra-high frequency (UHF, 300–3000 MHz)      < 1.2 × 107  
GPS (1176–1602 MHz)      < 1.2 × 107  
F10.7 (2800 MHz)      < 1.3 × 107  
Microwave (4000–20,000 MHz)      < 3.7 × 107  
Variations of relativistic electron flux of the outer radiation belt Electron fluence (> 2 MeV)[1010 cm−2sr−1] at GEO  ~ 0.1  ~ 0.6  ~ 3.0  ~ 10  ~ 26
Magnetic storm Dst index [nT]    ~  − 220  ~  − 450 ± 30  ~  − 650 ± 110  ~  − 930
Substorm AL index [nT]    ~  − 3700  ~  − 4100  ~  − 4100  ~  − 4200
SML index [nT]  − 460  − 3000  − 4000  − 5000  − 5900
Total electron content (TEC) @Tokyo [TECU]    ≥ 90  ≥ 130  ≥ 190  
@Kagoshima [TECU]    ≥ 110  ≥ 160  ≥ 230  
@Hokkaido [TECU]    ≥ 70  ≥ 105  ≥ 150  
Dellinger phenomenon Absorption [dB] @6.6 MHz (long-circuit)    ~ 71  ~ 83  ~ 93  ~ 100
Event duration [h]   0.6–1.3 1.8–3.6 4.0–6.8 7.4–11.9
Sporadic
E-layer
Frequency propagating 1,000 km [MHz]   100 110  ≥ 130  
Frequency propagating 2,000 km [MHz]   130  ≥ 180  ≥ 180  
Duration for foEs > 13.3 MHz [h]    ~ 3  ~ 5   
Duration for foEs > 18 MHz [h]    ~ 1–2  ~ 3   
Plasma bubble Event duration [h]   4–5 6   
Polar cap absorption (PCA) Invariant latitude, day
@6.6 MHz 10 dB
65° 57° 53° 51° 50°
Invariant latitude, night @6.6 MHz 10 dB 65° 60° 56° 53° 53°
Minimum duration [h] 22 46 71 83 89