Geophysical Effects of the March 29, 2006, Solar Eclipse
Academician of the RAS
V. V. Adushkin, B. G. Gavrilov, K. I. Gorelyi,
Yu. S. Rybnov, and V. A. Kharlamov
Received June 14, 2007
This paper presents results of comprehensive infrasonic,
radiophysical, and electromagnetic measurements
during the March 29, 2006, solar eclipse. Investigations
were carried out in the territory of the Mikhnevo
geophysical observatory (Institute of Geosphere
Dynamics, Russian Academy of Sciences) located
80 km away from Moscow in the Serpukhov area of the
Moscow region.
We obtained the following results:
(i) excitation of acoustic-gravitational waves at a
frequency close to the Brent–Väsälä frequency (1.7·10^–3 Hz)
was recorded in the atmosphere during the
maximum phase of the solar eclipse;
(ii) variations were recorded in the total ionospheric
electron content (TEC);
(iii) variations in the geomagnetic field, magnetic
declination, and inclination were recorded during the
maximum phase of the eclipse;
(iv) the spectral density pattern of variations in the
near-earth electric field (hereafter, EF) at a frequency of
about 10^–2 Hz coincided in time with variations in
the TEC; and
(v) variations were recorded in radiowave propagation
along paths intersecting the lunar shadow trajectory.
Geophysical effects accompanying a solar eclipse
have always attracted the attention of researchers,
because such processes provide insight into the nature
and mechanism of perturbations in the Earth’s ionosphere
and atmosphere related to the influence of the
Sun. This issue is discussed in many publications [1–7].
However, comparison of data based on various methods
in different geographic zones and heliographic conditions
is a difficult task. In this connection, analysis of
diverse geophysical data obtained simultaneously at
one observation point can undoubtedly provide interesting
results.
In the Moscow region, where the measurements
were made, the solar eclipse started on March 29, 2006,
at 10:10 UT and terminated at 12:18 UT. The maximum
phase was recorded at 11:15 UT, and the total duration
of the eclipse was ~2 h.
Infrasonic oscillations were recorded by a infralow-frequency
microbarometer, which makes it possible to
record weak oscillations of atmospheric pressure with
an amplitude of 0.1·10^2 Pa in the frequency range of
10^–4 – 20 Hz. The state of the atmosphere was controlled
by a transducer of absolute atmospheric pressure.
Figure 1 shows records of infrasonic and atmospheric
pressure variations. One can see that the pressure
begins to fall virtually with the onset of the eclipse.
Based on the frequency analysis, the infrasonic record
can be divided into three characteristic periods:
(i) the pre-eclipse period characterized by background
oscillations in the frequency range from 3·10^–4
to 5·10^–2 Hz related to turbulence of the near-Earth atmosphere
(their spectrum corresponds to the relation
f^–5/3);
(ii) the period from the onset of the eclipse to its
maximum phase characterized by the disappearance of
low frequencies in the range of (3–5)·10^–4 Hz and the
appearance of intense infrasonic oscillations in the frequency
range of (1.5–1.7)·10^–3 Hz as the maximum
phase of the eclipse is approached; and
(iii) the period after the maximum phase of the eclipse
characterized by the appearance of oscillations in the frequency
range of (3–4)·10^–4 and (7–8)·10^–4 Hz.
Thus, analysis of infrasonic oscillations showed that
low-frequency acoustic-gravitational waves, including
those in the Brent–Väsälä frequency, are excited as the
maximum phase of the solar eclipse is approached and
for half an hour after its passage in the atmosphere.
Such phenomena are typical of atmospheric fronts and
convective thunderstorm cells [8]. Thereby, the maximum
effect is shifted to long periods (20–50 min) outward
from the lunar shadow.
We also carried out measurements of the TEC with
the GPS receiver of the Trimble 5600 type during the
solar eclipse. The spectral density pattern of TEC variations
(Fig. 2a) shows that strong TEC variations
appeared at approximately 07:30 UT, i.e., 2.5 h before
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Institute of Geosphere Dynamics, Russian Academy of Sciences,
Leninskii pr. 38/1, Moscow, 117334 Russia;
e-mail:
ushkin@idg.chph.ras.ru
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