NM-MT NETWORK AND SPACE DANGEROUS PHENOMENA, 2.
EXAMPLES OF COSMIC RAY USING FOR FORECASTING OF
MAJOR GEOMAGNETIC STORMS
L.I. Dorman 1,2, A V. Belov 2, E.A. Eroshenko 2, N. Iucci 3, M. Parisi 3, L.A. Pustil’nik 1, A. Sternlieb 1,
G. Villoresi 3, V.G. Yanke 2, and I.G. Zukerman 1
1
Israel Cosmic Ray Center and Emilio Segre’ Observatory, affiliated to Tel Aviv University, Technion and
Israel Space Agency, P.O.Box 2217, Qazrin 12900, ISRAEL
2
IZMIRAN, Russian Academy of Science, Troitsk 142092, Moscow Region, RUSSIA
3
Dipartimento di Fisica “E. Amaldi”, Università “Roma Tre”, Rome, Italy;
ABSTRACT
We present methods (e.g., Belov et al., 1995a,b; Dorman et al., 1995, 1999) for forecasting geomagnetic
storms of scales G5 (3-hour index of geomagnetic activity Kp=9), G4 (Kp=8) and G3 (Kp=7) (according to
NOAA Space Weather Scales), by using on-line 1-hour neutron monitor data (as well as on-line muon
telescopes hourly data from different directions). These geomagnetic storms are dangerous for people’s
technology and health (influence on power systems, on spacecraft operations, on HF radio-communications
and others). On the basis of data from several historical events, we show that for forecasting of especially
dangerous geomagnetic storms one can use the ring CR stations method (if on-line data from 10-15 stations
are available) and global-spectrographic method (if on-line data from 35-40 NM and muon telescopes are
available). In this case for each hour one can determine CR anisotropy vector, and the specifically behavior
of this vector before Sudden Storm Commencement (SSC) of geomagnetic storms G5, G4 or G3 (according
to NOAA Space Weather Scales) can be used as an important factor for forecast. The second factor what can
be used for SSC forecast is specifically behavior of CR density (CR intensity pre-decrease) for about 30-15
hours before SSC (caused mainly by galactic CR particles acceleration during interaction with shock wave
moved from the Sun). The third factor is effect of CR pre-decreasing, caused by magnetic connection of the
Earth with the region behind the shock wave with the lower CR intensity.
This research is partly supported by the EU INTAS Grant 00810.
INTRODUCTION
In the first paper (Dorman et al., 2003) we considered effects of strong geomagnetic storms,
accompanied by cosmic ray (CR) Forbush decreases (FD) on satellite and aircraft electronics, technology,
communications, and operations. We mention that in these periods there are also influences on people’s
health (increasing of probability of infarcts myocardial and brain strokes) and on car road accidents (with
increasing of car road accident traumas). It was suggested (Dorman, 2002, 2003a; Dorman et al., 2003) to
add these biological effects to the well known NOAA scale of space magnetic storms effects in space, in
atmosphere and on the ground. In Dorman et al. (2003) we considered also the short historical review of
many attempts of CR using for forecasting of this dangerous space phenomenon caused by the interaction of
strong geomagnetic shock wave with the Earth’s magnetosphere. This interaction is accompanied by the well
known Forbush decrease in CR intensity and several precursory effects as CR pre-increase, CR pre-decrease,
change in CR fluctuation frequency spectrum, and change in 3-D CR anisotropy. Here we will consider the
possibility to use the first two precursory effects (CR pre-increase and CR pre-decrease) by the method of
ring CR stations on examples of several historical events The method of ring CR stations was supposed by
McCracken et al. (1962, 1965), and then used and developed by many authors (see review in Dorman, 1974,
2003b).
EXAMPLES OF COSMIC RAY PRECURSORY EFFECTS: ASYMPTOTIC LONGITUDE 
UNIVERSAL TIME COSMIC RAY INTENSITY DISTRIBUTION
In Fig. 1 we show an
example of such estimation
done for the 25.05.1978
event
represented
as
asymptotic
longitudeuniversal time CR intensity
distribution.
The
dark
rhombs mark the CR
intensity pre-decrease and
decrease after SC, light
ones - the pre-increase. The
size of rhombs indicates the
magnitude of the effect.
The vertical line marks the
time of SSC.
Fig. 1. The event of 25 May
1978:
the
asymptotic
longitude  universal time
CR intensity distribution
according to 12 NM one
hour data.
From Fig. 1 it can be seen that CR intensity pre-increase starts about 10 hours before SC in the interval of
asymptotic longitudes between 12h and 20h and continues several hours after SC. Therefore the CR intensity
decrease starts not simultaneously: it starts about 10-15 hours before SC of geomagnetic storm in the
interval of asymptotic longitudes centered near 6h , and several hours after SC of geomagnetic storm in the
interval of asymptotic longitudes centered near 18h (the last is caused mainly by the continued CR intensity
increase),
The other example of analysis is shown in Fig. 2 for the geomagnetic storm of 9-th September 1992.
Fig. 2. Galactic CR
intensity
pre-increase
(yellow circles) and predecrease and Forbush decrease (red circles)
before and after the
Sudden
Storm
Commencement (SSC) of
great magnetic storm at 9th September 1992. The
bigger diameter of circle
means bigger amplitude of
CR intensity variation.
From Fig. 2 it can be
seen that the pre-increase,
as well as the pre-decrease,
occurs 15-20 hours before
the SSC of geomagnetic storm.
EXAMPLES OF COSMIC RAY PRECURSORY EFFECTS: BOTH ASYMPTOTIC LONGITUDE
UNIVERSAL TIME AND PITCH-ANGLEUNIVERSAL TIME CR INTENSITY DISTRIBUTIONS
Here for each event we present two pictures: longitudinal and pitch-angle distribution (yellow circles – for
positive variations, red ones – for negative). We used one-hour data of NM with Rc < 4 GV, and standard
pressure ho > 900 mb, i.e. high mountain stations were excluded; for longitudinal distribution the sub-polar
stations were also excluded. For longitudinal distribution we used the effective station locations for flat
rigidity spectrum of CR anisotropy, extracted from coupling coefficients technique. For pitch-angle
distribution we used the asymptotic directions of vertically arriving particles with 4.5 GV rigidity (i.e. the
soft spectrum was assumed). Pitch-angles are counted from sunward field direction. So the classical predecrease we have to search in the lower part (sometimes the anomalous pre-decrease is possible from the
opposite side)
Two geomagnetic storms on 28 and 29 September 1978
The results of analysis of both asymptotic longitude  universal time CR distribution and pitch-angle 
universal time CR intensity distribution are shown in Fig. 3.
Fig. 3. Event of two geomagnetic storms in 1978 at 28 September (SSC at 21h UT) and 29 September (SSC
at 3h UT). Yellow circles – for positive variations, red ones – for negative; the amplitude of variations is
proportional to the diameter of cycles.
From Fig. 3 one can see clear changes of CR anisotropy, and we see a good pre-increase already before the
first interplanetary shock wave (before the first SSC). Before the second SSC a classical precursor with wide
pre-increase and pre-decrease on the small pitch angles is observed.
Geomagnetic storm at 24 April 1979
(results are shown in Fig. 4).
Fig. 4. Event of geomagnetic storm at 24
April 1979 (SSC at 23.58 UT).
Changes of anisotropy are seen in the
pitch angle – universal time distribution
approximately 10 hours before the
shock, and in the last several hours
before SSC we see clear pre-decrease of
CR intensity on the small pitch angles.
Geomagnetic storm at 29 August 1979
(results are shown in Fig. 5).
Fig. 5. Event of geomagnetic storm at 29
August 1979 (SSC at 04.59 UT).
In this case long duration and wide density
increase is observed before the shock. A wide
decrease connected probably with loss-cone
exists also on this background.
Two geomagnetic storms at 11 April
1981 (results are shown in Fig. 6).
Fig. 6. The event of two geomagnetic
storms at 11 April 1981 (SSC at 7.20
and 13.39 UT).
In this case enhancement CR
variations are observed all time
between two shocks. Small precursor
also can be seen before the first shock.
Geomagnetic storm at 1 March 1982
(results are shown in Fig. 7).
Fig. 7. The event of geomagnetic storm
at 1 March 1982 (SSC at 11.38 UT).
In this case CR intensity pre-decrease
and pre-increase are observed at about 5
hours before SSC (before the shock
wave front) – a classical example of
precursor. The effect was observed also
on many mid-latitudinal stations.
Geomagnetic storm at 13 July 1982
(results are shown in Fig. 8)
Fig. 8. The event of geomagnetic storm
at 13 July 1982 (SSC at 16.17 UT).
In this case there is no classical
predictor, but in enhanced CR intensity
variation the decreasing of CR intensity
is seen 5 hours before the shock.
Unfortunately, pitch angles are not
small. There is strongly disturbed
background (high Kp) before this
shock. Clear predictor exists probably,
but it has not been possible to calculate
right pitch-angles because of the strong
geomagnetic disturbances before SSC.
Geomagnetic storm at 6 August
1982 (results are shown in Fig. 9).
Fig. 9. The event of geomagnetic
storm at 6 August 1982 (SSC at 18.36
UT).
In this case the situation is not clear:
enhanced variation in CR intensity
seems to be observed, but stations
with small pitch angles are almost
absent.
Geomagnetic storm at 5 September
1982 (results are shown in Fig. 10).
Fig. 10. The event of geomagnetic storm
at 5 September 1982 (SSC at 22.50 UT).
In this case enhanced variation of CR
intensity appears to be at the last 3-4
hours before the shock as pre-decrease.
CONCLUSION
From the results discussed above it
follows that the strong geomagnetic
storm accompanied with Forbushdecrease in CR intensity has clear precursor effects which can be used for
forecasting about 10-15 hours before SSC on geomagnetic storm. The results obtained are in agreement with
those obtained previously by Belov et al. (1995a,b), Dorman et al. (1995, 1999), Munakata et al. (2000). As
it was shown by Munakata et al. (2000), the CR pre-increase and pre-decrease effects can be observed very
clearly also by multidirectional muon telescope world network. They investigated 14 “major” geomagnetic
storms characterized by K p  8  and 25 large storms characterized by K p  7  observed in 1992-1998.
It was shown that 89% of “major” geomagnetic storms have clear precursor effects, which can be used for
forecasting (the probability of exact forecasting increases with increasing storm strength).
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E-mail address of Lev I. Dorman: lid@physics.technion.ac.il, lid1@ccsg.tau.ac.il
Manuscript received
; revised
, accepted