2. Experimental Results
[3] Our investigations have shown that when the IMF polarity
near the Earth changes, the Earth's crust is subjected to the action
of the IMF inhomogeneities, which gives rise to the neutron
emission from the Earth's surface in the form of short-term bursts.
The mechanism of neutron production in this case can be
supposed to be similar to that of the gravitational influence of the
Moon and the Sun on the Earth at the new Moon and the full
Moon, i.e., it is associated with deformation of the Earth's crust
with a subsequent release of radioactive gases of radon isotopes.
Then the interaction of alpha particles resulting from the decay of
radon isotopes with nuclei of the constituents of air and the
Earth's crust gives rise to neutron production
[Volodichev et al., 1997, 2003\linkvolo03].
It can be believed in this case that when the IMF
polarity changes, the Earth's crust is subjected to deformation and
experiences, for instance, the electrostriction and magnetostriction
influences of the IMF, which gives rise to minor changes in the
linear sizes and volume of the Earth
[Frish and Timoreva, 1953].
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Figure 1
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Figure 2
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Figure 3
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[4] We have analyzed information for 14 months: August,
October, and November of 1999, January, February, March, and
April of 2000, February of 2001, March, May, and December of
2002, and January, February, and March of 2003
[Kuzhevskij et al., 2003].
During this period the IMF polarity near the Earth
varied 70 times. As a rule (in 95% of the cases), the change in the
IMF polarity was accompanied by variations in the IMF strength,
the field strength changing in several times, and sometimes by an
order of magnitude. The neutron instrument at the Institute of
Nuclear Physics
[Kuzhevskij et al., 1996]
detected 40 bursts of
neutron emission intensity during this time. Eighteen of these
bursts coincide in time with the time of the IMF polarity reversal
and onset of the IMF strength variations. Figures 1, 2, and 3 show
examples of detection of neutron bursts during the IMF polarity
reversal and strength variations in Moscow in October of 1999
and February of 2000 and simultaneous detection of neutron
bursts in Tien Shan and Moscow in August of 1999. In addition to
neutron emission bursts, the figures schematically show the IMF
polarity and the strength of the full field and its components
(http://www.srl.caltech.edu).
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Figure 4
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Figure 5
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Figures 4 and 5 present the events of
October of 1999 (Figure 1) and February of 2000 (Figure 2)
mentioned above, but in contrast to these figures, Figures 4 and 5
give the solar wind parameters for these time periods, i.e., solar
wind velocity, density of solar wind protons, and temperature of
solar wind protons (http://www.srl.caltech.edu). Neutron channels
1 and 2 (the first instrument) give information about the counting
rate of the neutrons detected by two independent instruments,
analogous information is provided by channels 0 and 4,
respectively, of the second instrument. The onset of the neutron
emission burst on 20 October 1999 is close in time to the
beginning of crossing of the high-speed solar wind stream by the
Earth (Figures 1 and 2), and this can be the reason for the IMF
polarity change at that time. The same is true for neutron bursts
on 11 and 23 February 2000 (Figures 3 and 4). The investigations
have shown that the burst of 24 February 2000 (Figure 4) is due to
electrical interference. The neutron emission bursts on 6 August
1999 (Figure 5) can be caused by the change of the IMF polarity
at crossing of "small" IMF sectors by the Earth. Therefore it can
be concluded that when the Earth enters the inhomogeneous IMF,
it experiences the electrostriction and magnetostriction influences
of the IMF, and emission of neutrons by the Earth's crust is one
of the responses to this influence.
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