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1.
A. I. Efimov N. A. Armand L. A. Lukanina L. N. Samoznaev I. V. Chashei M. K. Bird 《Geomagnetism and Aeronomy》2009,49(8):1165-1169
The two-position radio sounding of the solar wind by the Galileo and Cassini spacecraft has been first performed. These spacecraft
followed the Sun from east to west from May 12 to 24, 2000 and sounded the regions spaced in radial directions by several
millions of kilometers. Stable correlation has been revealed between fluctuation effects detected in spatially spaced radio-sounding
paths of disturbed plasma structures of the coronal mass ejection (CME) type. The radio effects have been found to correlate
also with the data on the solar wind density near the Earth orbit. It has been shown that the two-position radio-sounding
method together with the data on solar radiation in the X-ray and optic ranges and with the results of local plasma measurements
provides information on the structure and velocity of the propagation of CMEs from the photosphere to the Earth orbit. In
the most powerful event recorded on May 13, 2000, the CME velocity at the heliocentric distances of about 15R
⊙ (R
⊙ is the solar radius) reached 1200 km/s. At (15–25) R
⊙, the velocity was about 1300 km/s. At distances larger than 25R
⊙, disturbance was decelerated from 1300 to 450 km/s near the Earth orbit. 相似文献
2.
The structure of the averaged plasma pressure distribution in the plasma ring around the Earth at geocentric distances of
∼6–10R
E
has been determined. The distribution function moments measured on the international THEMIS mission satellites have been
used. The plasma pressure distribution in the equatorial plane at 15R
E
> XSM > −15R
E
and 15R
E
> YSM > −15R
E
has been statistically studied. The radial dependence of the plasma pressure at the day-night and morning-evening meridians
has been analyzed. It has been indicated that the plasma ring around the Earth has a structure, which is close to being azimuthally
symmetric. The achieved results have been compared with the pressure distributions obtained previously. It has been indicated
that in the overlapping regions, the achieved results agree with the previously obtained data within the pressure determination
errors. 相似文献
3.
V. G. Fainshtein 《Geomagnetism and Aeronomy》2006,46(3):339-349
A method for determining the parameters of halo-type coronal mass ejections (full halo CMEs)—direction of motion, angular size, CME velocity along the Sun-Earth axis, etc.—has been proposed and tested. The method is based on the found empirical dependence between the angular sizes of CMEs located near the sky plane and angular sizes of associated eruptive prominences or post-eruptive arcades as well as on the relationships between the halo CME parameters derived in a simple geometrical CME model. Using this method and the SOHO/LASCO C3 and SOHO/EIT data, the parameters of 33 full halo CMEs have been determined. It is concluded that (1) the trajectories of all considered full halo CMEs deviate with recession of the CME front to R F > (2–5)R 0 toward the Sun-Earth axis; (2) the majority of full halo CMEs recorded by LASCO C3 coronagraphs have relatively large angular sizes, 2α > 60°. 相似文献
4.
Features and physical process of the dynamic evolution pattern of ground resistivity precursor front
IntroductionSincethe1960′s,thedevelopmentofmodernscienceandtechnologyhasgradualymadeitposibletopredictearthquakesandhaspromot... 相似文献
5.
Tunnel effect of fractal fault and transient S-wave velocity rupture (TSVR) of in-plane shear fault 总被引:1,自引:0,他引:1
ntroductionTransientSwavevelocityrupture(TSVR)meansthevelocityvoffaultruptureisbetweenSwavevelocityβandPwavevelocityα.Itse... 相似文献
6.
The studies are based on the experimental mass sounding of the interplanetary plasma near the Sun at radial distances of R = 4−70 R
S, performed at Pushchino RAO, Russian Academy of Sciences, and on the calculated magnetic fields in the solar corona based
on the magnetic field strength and structure measured on the Sun’s surface at J. Wilcox Solar Observatory, United States.
The experimental data make it possible to localize the position of the boundary closest to the Sun of the transition transonic
region of the solar wind in the near-solar space (R ≈ 10−20 R
S) and to perform an interrelated study of the solar wind structure and its sources, namely, the magnetic field components
in the solar corona based on these data. An analysis of the evolution of the flow types in 2000–2007 makes it possible to
formulate the physically justified criterion responsible for the time boundaries of different epochs in the solar activity
cycle. 相似文献
7.
In this paper, we examine the nature of the main source of the sporadic solar wind on the Sun: coronal mass ejections (CMEs).
Analysis of data from Mark 3 and Mark 4, the Digital Prominence Monitor (MLSO), and STEREO (EUVI) spacecraft has revealed
the existence of two types of CMEs: gradual and impulse. They differ in the place, velocity, and angular size at the instant
of their emergence. The source of gradual CMEs is located in the corona, at a distance of 1.1 R
0 < R ≤ 1.7 R
0 from the center of the Sun. They start moving from a state of rest, having an angular size ≈15–65° (in the heliographic coordinate
system). Impulse CMEs are probably formed under the Sun’s photosphere. This may be due to the supersonic emergence of magnetic
tubes (ropes) from the convective zone. The possibility of this phenomenon has been demonstrated earlier in theory. The radial
velocity of such tubes at the photospheric level may be 100 km/s or higher; the minimum angular size is ∼1°. 相似文献
8.
On the basis of fault’s dynamic model of Knopoffet al. (1973), this paper has finally obtained a simple approximate formula to be able to estimate the recurrence time intervalT
R
of earthquake on strike-slip fault. Preliminary result holds thatμ andδ
s
— δ
f
have not much effect onT
R
. Leta is the ratio of the coseismic displacementD
s
to the total displacementD
t
in whole event course, i.e.,a =D
s
/D
t
, thena = 1/3 may represent the standard theoretical state in whichT
R
is independent onμ andδ
s
— δ
f
. At this time,T
R
is the arithmetic average ofs
0/v andkd/β, wheres
0 is the long-term preseismic accumulated slippage,v is fault’s average displacement rate,d is the fracture length on the fault of seismic focal region andβ is shear wave velocity. In addition,k =υ
0/aυ, whereυ
0 is the initial fracture velocity of actual structure at the coseismic instant.
The Chinese version of this paper appeared in the Chinese edition ofActa Seismologica Sinica,14, 187–194, 1992.
This paper is a part of contracted item of State Seismological Bureau — Tectonic Physical Study of Earthquake Recurrence Period
and Characteristic Magnitude. 相似文献
9.
Based on the long period surface wave data recorded by the China Digital Seismograph Network (CDSN), theQ
R
of fundamental mode Rayleigh wave with periods from 10 s to 146 s is determined for the eastern Sino-Korean paraplatform
in this paper. TheQ
β
models of the crust and upper mantle are respectively obtained for the 4 paths, with the aid of stochastic inverse method.
It shows that in the eastern Sino-Korean paraplatform, the average crustalQ
β
is about 200, and that there exists a weak attenuation layer in the middle crust (about 10–20 km deep) which is possibly
related to earthquake-prone layer. A strong attenuation layer (lowQ) of 70 km thick extensively exists in the uppermost mantle, with the buried depth about 80 km. The averageQ
R
of fundamental mode Rayleigh wave is between the value of stable tectonic region and that of active tectonic region, and
much close to the latter.
Contribution No. 96A0001, Institute of Geophysics, SSB, China.
Funded by the Chinese Joint Seismological Science Foundation. 相似文献
10.
A new modified magnitude scale M
S
(20R) is elaborated. It permits us to extend the teleseismic magnitude scale M
S
(20) to the regional epicenter distances. The data set used in this study contains digital records at 12 seismic stations
of 392 earthquakes that occured in the northwest Pacific Ocean in the period of 1993–2008. The new scale is based on amplitudes
of surface waves of a narrow range of the periods (16–25 s) close to the period of 20 s, for distances of 80–3000 km. The
digital Butterworth filter is used for processing. On the basis of the found regional features concerning distance dependence
for seismic wave attenuation, all the stations of the region have been subdivided into two groups, namely, “continental” and
“island-arc.” For each group of stations, its own calibration function is proposed. Individual station corrections are used
to compensate for the local features. 相似文献
11.
Takehiro Koyaguchi 《Bulletin of Volcanology》1994,56(1):1-9
The relationships among the thickness and grain-size of tephra-fall deposits and the volumetric flow rate of their source
umbrella clouds are analytically obtained. The logarithm of the ratio of the probability distribution function based on grain
size (ln R
f) in fall deposits at two localities from the vent (r
1 and r
2, respectively) has a linear relationship with the particle-settling velocity, v, as:
where Q is the volumetric flow rate of the umbrella cloud and A is a constant for a given pair of localities. The volumetric flow rate of the umbrella cloud can be estimated from granulometric
data using this formula. Generally, the thickness–distance relationship of tephra-fall deposits depends on the initial grain-size
distribution and the volumetric flow rate of the umbrella cloud. The empirical relationship of the exponential thinning behaviour
can be extrapolated towards infinite distance only for a specific initial grain size which is similar to a log-normal distribution
with σ
φ=2.5, otherwise it holds only in a limited range of distances. In applying these results to the 1991 eruption of Mt. Pinatubo,
it is shown that the volumetric flow rate of the umbrella cloud during the climactic phase of 15 June was approximately 5×1010 m3/s, which is fairly consistent with the expansion rate of the umbrella cloud observed in the satellite images.
Received March 20, 1993/Accepted September 11, 1993 相似文献
12.
Shear flow instability is studied in the Earth’s magnetotail by treating plasma as compressible. A dispersion relation is derived from the linearized MHD equations using the oscillating boundary conditions at the inner central plasma sheet/outer central plasma sheet (OCPS) interface and OCPS/plasma-sheet boundary layer (PSBL) interface, whereas the surface-mode boundary condition is used at the PSBL/lobe interface. The growth rates and the real frequencies are obtained numerically for near-Earth (\midX\mid\sim10-15 RE) and far-Earth (\midX\mid\sim100 RE) magnetotail parameters. The periods and wavelengths of excited modes depend sensitively on the value of plasma-sheet half thickness, L, which is taken as L=5 RE for quiet time and L=1 RE for disturbed time. The plasma-sheet region is found to be stable for constant plasma flows unless MA3>1.25, where MA3 is the Alfvén Mach number in PSBL. For near-Earth magnetotail, the excited oscillations have periods of 2–20 min (quiet time) and 0.5-4 min (disturbed time) with typical transverse wavelengths of 2–30 RE and 0.5-6.5 RE, respectively; whereas for distant magnetotail, the analysis predicts the oscillation periods of \sim8-80 min for quiet periods and 2–16 min for disturbed periods. 相似文献
13.
The speedv, especially the problem whether super S-wave velocity in the classical model (linear elasticity fracture mechanics) exists,
of spontaneous propagation of a shear fault is investigated theoretically. An in-plane shear crack propagating in the crack
plane is taken as the model of the shear fault. The results obtained firstly by Kostrov (1975) is extended from sub-Rayleigh
wave velocity to super S-wave velocity, and the analytical expression for the stress intensity factorK
2 in the case ofα>v>β is derived. It is proved that for Poisson mediumK
2 is positive and real in the velocity range (β, 1.70β). This demonstrates that (β, 1.70β) is the velocity range which fulfils the conditions for spontaneous crack propagation. The existence, convergence and positiveness
or negativeness ofK
2 forv in individual sections are examined, and it is found that for an in-plane shear crack: 1. There are three sections forv, i.e., [0.v
R], (β, 1.70β), andα, respectively, and 2. There are two physically reasonable sections forv, the first is [v
R, β], and the second is [1.70β, α]. These two forbidden sections behave as barriers to fault propagation.
The analytical expressions derived in this paper are not only suitable to classical model, but also to the other derivative
models (e. g., the slip-weakening model and the renomalization model etc.). The model considered in this paper is more realistic
than the static model employed by previous authors.
The Chinese version of this paper appeared in the Chinese edition ofActa Seismologica Sinica, 15, 9–14, 1993. 相似文献
14.
Peak and integral seismic parameters of L��Aquila 2009 ground motions: observed versus code provision values 总被引:1,自引:1,他引:0
A. Masi L. Chiauzzi F. Braga M. Mucciarelli M. Vona R. Ditommaso 《Bulletin of Earthquake Engineering》2011,9(1):139-156
The M
w 6.3 L’Aquila earthquake of April 6, 2009 hit a wide area of the Abruzzo region (Central Italy). The epicentre of the main
shock was very close to the urban centre of L’Aquila, the regional capital, with an epicentral distance less than 10 km. It
was the strongest earthquake ever recorded in Italy which has provided ground motion recordings from accelerometric stations
located in close proximity to the epicentre. Because of this, several remarkable results can be achieved by analysing the
strong motion recorded signals in terms of peak (PGA, PGV and PGD) and integral (Housner Intensity, I
H) seismic parameters. Additionally, an alternative time-domain representation of recorded signals has been used to furnish
a rapid comparison of traces recorded at different stations and along different directions. Some comparisons between the response
spectra derived from the recordings and the elastic demand spectra provided in the new seismic Italian code have also been
performed. PGA recorded values are very high and generally higher than code values for seismic actions with return period
T
R = 475 years. In some cases, this also happens for seismic actions with T
R up to 2,475 years. With regard to I
H, recorded values are generally higher for T
R = 475 years, whilst they are remarkably lower for T
R = 2,475 years. Accurate analyses have been carried out in the article to better understand the above differences and their
significance and implications. 相似文献
15.
We studied broadband digital records of the M
W
= 7.6 Olyutorskii earthquake of April 20, 2006 and its aftershocks at local and regional distances. We have made a detailed
analysis of data on peak ground motion velocities and accelerations due to aftershocks based on records of two digital seismic
stations, Tilichiki (TLC) and Kamenskoe (KAM). The first step in this analysis was to find the station correction for soil
effects at TLC station using coda spectra. The correction was applied to the data to convert them to the reference bedrock
beneath the Kamenskoe station. The second step involved multiple linear regression to derive average relationshis of peak
amplitude to local magnitude ML and distance R for the Koryak Upland conditions. The data scatter about the average relationshis is comparatively low (0.22–0.25 log units).
The acceleration amplitudes for M
L
= 5, R = 25 km are lower by factors of 2–3 compared with those for eastern Kamchatka, the western US, or Japan. A likely cause of
this anomaly could be lower stress drops for the aftershocks. 相似文献
16.
We present observations of electric and magnetic field variations from proton (about few Hz) to electron cyclotron frequencies
(about few kHz) obtained by STAFF instrument on Cluster satellites during two cusp crossings, at ∼6 R
E
altitude, in September 2002. The cusp was identified by the presence of intensive fluxes of counter streaming electrons with
low energies and broadband wave activity which is typical for this region.
Special attention is given for the interval of measurements when the waveform of the magnetic field fluctuations was taken
in this region by CLUSTER satellites. The wave has been processed using the wavelet and bispectral analysis. Results showing
the cascade of turbulence and wave-wave interactions are presented in this paper. A three wave process can be responsible
for the broadening of the wave spectra in the polar cusp. 相似文献
17.
I. B. Boikov M. V. Kravchenko V. I. Kryuchko 《Izvestiya Physics of the Solid Earth》2010,46(4):339-349
Numerical algorithms are suggested for reconstructing the potential field in the region Ω = {0 ≤ R
0 ≤ ρ ≤ R, 0 ≤ θ ≤ π, 0 ≤ φ ≤ 2π} from its values on the surface Γ1 = {R,0 ≤ α1 ≤ θ ≤ α2 ≤ π, 0 ≤ β1 ≤ φ ≤ β2 ≤ π}. 相似文献
18.
Tsunami generated by submarine slumps and slides are investigated in the near-field, using simple source models, which consider the effects of source finiteness and directivity. Five simple two-dimensional kinematic models of submarine slumps and slides are described mathematically as combinations of spreading constant or slopping uplift functions. Tsunami waveforms for these models are computed using linearized shallow water theory for constant water depth and transform method of solution (Laplace in time and Fourier in space). Results for tsunami waveforms and tsunami peak amplitudes are presented for selected model parameters, for a time window of the order of the source duration.The results show that, at the time when the source process is completed, for slides that spread rapidly (cR/cT≥20, where cR is the velocity of predominant spreading), the displacement of the free water surface above the source resembles the displacement of the ocean floor. As the velocity of spreading approaches the long wavelength tsunami velocity
the tsunami waveform has progressively larger amplitude, and higher frequency content, in the direction of slide spreading. These large amplitudes are caused by wave focusing. For velocities of spreading smaller than the tsunami long wavelength velocity, the tsunami amplitudes in the direction of source propagation become small, but the high frequency (short) waves continue to be present. The large amplification for cR/cT1 is a near-field phenomenon, and at distances greater than several times the source dimension, the large amplitude and short wavelength pulse becomes dispersed.A comparison of peak tsunami amplitudes for five models plotted versus L/h (where L is characteristic length of the slide and h is the water depth) shows that for similar slide dimensions the peak tsunami amplitude is essentially model independent. 相似文献
19.
The characteristics of dayside auroras during the large (16–24 nT) positive values of the IMF B
z
component, observed on January 14, 1988, during the interaction between the Earth’s magnetosphere and the body of the interplanetary
magnetic cloud, have been studied based on the optical observations on Heiss Island. A wide band of diffuse red luminosity
with an intensity of 1–2 kilorayleigh (kR) was observed during 6 h in the interval 1030–1630 MLT at latitudes higher than
75° CGL. Rayed auroral arcs, the brightness of which in the 557.7 nm emission sharply increased to 3–7 kR in the postnoon
sector immediately after the polarity reversal of the IMF B
y
component from positive to negative, were continuously registered within the band. Bright auroral arcs were observed at the
equatorward edge of red luminosity. It has been found out that the red auroral intensity increases and the band equatorward
boundary shifts to lower latitudes with increasing solar wind dynamic pressure. However, a direct proportional dependence
of the variations in the auroral features on the dynamic pressure variations has not been found. It has been concluded that
the source of bright discrete auroras is located in the region of the low-latitude boundary layer (LLBL) on closed geomagnetic
field lines. The estimated LLBL thickness is ∼3 R
e
. It has been concluded that the intensity of the dayside red band depends on the solar wind plasma density, whereas the position
of the position equatorward boundary depends on the dynamic pressure value and its variations. 相似文献
20.
Luiz Bruner de Miranda Alessandro Luvizon Bérgamo Belmiro Mendes de Castro 《Ocean Dynamics》2005,55(5-6):430-440
Observations of thermohaline properties and currents were undertaken in the Curimataú River estuary (6°18′S), Rio Grande do
Norte state (RN), Brazil, during consecutive neap–spring tidal cycles in the austral autumn rainy season. Highly asymmetric
neap tide along channel velocities (−0.4 to 0.9 m s−1) and highly stratified conditions were generated by an increase of the buoyancy energy from the freshwater input (R
iE≈5.6). During the spring-tidal cycle the river discharge decreased and the longitudinal velocity components were higher, less
asymmetrical (−0.8 to 1.1 m s−1) and semidiurnal, associated with moderately stratified conditions (R
iE≈0.1) due to the increase of the kinetic tidal energy forcing mechanism. The overall salinity variation from surface to bottom
during two tidal cycles was from 20.5 to 36.3 and 29 to 36.7 in the neap and spring tide experiments, respectively; in the
last experiment, the tropical water (TW) mass intrusion was enhanced. The net salt transport reversed from down to up estuary
during the neap and spring tide experiments, respectively, varied from 6.0 to –2.0 kg m−1 s−1, an indication of changes in the main forcing of the estuary dynamics. Evaluation of a classical steady analytical model,
in comparison with nearly steady experimental vertical profiles of velocity, shows an agreement classifiable as reasonably
fair. 相似文献