Table 2
Magnitudes of largest GLEs in solar cycles 17–23 (in %) over the pre-event GCR level.
| Rank | Date | IC/Station | MT/Station | NM/Station | Estimate/Reference |
|---|---|---|---|---|---|
| 1 – GLE05 | 23 Feb. 1956 | 300%, 2.05 GV, Moscow, 15-min | 280%, 2.32 GV, London, 15-min | 4554%, 1.70 GV, Leeds, 15-min | 9000%, Duggal (1979) |
| 2 – GLE69 | 20 Jan. 2005 | N.O. | 13%, 1.89 GV, GRAND- project, 1-min D’Andrea & Poirier (2005) | 5500%, 0.02 GV, SOPO NM64, 1-min http://cosrays.izmiran.ru | No Duggal’s estimate |
| 3 – GLE04 | 19 Nov. 1949 | 40%, 2.19 GV, Cheltenham, 15-min | 70%, 0.64 GV, Ottawa, 15-min | 563%, 1.70 GV, Manchester, 60-min | 2000%, Duggal (1979) |
| 4 – GLE03 | 25 Jul. 1946 | 22%, 2.19 GV, Cheltenham, 15-min | 13%, 1.70 GV, Manchester, 60-min | N.O. | 1100%, Duggal (1979) |
| 5 – GLE02 | 07 Mar. 1942 | 15%, 2.19 GV, Cheltenham, 15-min | 27%, Friedrichshafen, 60-min | N.O. | 750%, Duggal (1979) |
| 6 – GLE01 | 28 Feb. 1942 | 15.5%, 0.03 GV, Godhavn, 15-min | 00%, 4.06 GV – no increase, Friedrichshafen, 60-min | N.O. | 600%, Duggal (1979) |
| 7 – GLE42 | 29 Sep. 1989 | N.O. | 41%, 0.07 GV, Inuvik, 5-min Smart & Shea (1991) | >400%, 0.72 GV, Calgary, 5-min http://cosrays.izmiran.ru | No Duggal’s estimate |
Notes.
-
For technical reasons, when registering the early GLEs, the averaging time intervals (given after the name of CR station) were different for different detectors and may be changed from 1 h (60 min) to 1 min.
-
Maximum amplitudes of the first 4 GLEs have been reduced to a 15-minute averaging time interval (Dorman, 1957).
-
Ionization chamber (IC) events have been normalized to correspond to the increase that a high-latitude neutron monitor (NM) would have observed at sea level (Duggal, 1979).
-
Neutron component records for the GLE04 in Manchester were not obtained with the help of a “classical” NM, but with the help of the neutron detector that consisted of boron-trifluoride filled counters embedded in a “pile” built of high purity graphite (Adams, 1950).
-
The effective vertical cutoff rigidities of the neutron monitors (in GV units) are indicated for the CR stations with maximal observed amplitude of the corresponding GLEs.
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