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1.
A close synoptic relationship has been found, on the one hand, between the sector structure of the solar and interplanetary
magnetic fields and, on the other hand, the structure of tropospheric parameters (the near-Earth pressure and temperature)
in Central Russia during an anomalously hot anticyclonic weather in June–August 2010. It has been stated that the Earth crossed
the magnetic sector boundaries in full agreement with the boundaries of meteorological parameters, structuring the formation,
stabilization, and decay dynamics of anticyclones according to observations performed at IZMIRAN (Troitsk, φ = 55°, λ = 37°). 相似文献
2.
3.
V. V. Zharkova N. S. Meshalkina L. K. Kashapova A. T. Altyntsev A. A. Kuznetsov 《Geomagnetism and Aeronomy》2011,51(8):1029-1040
The kinetics of beam electron precipitation from the top of a loop into the solar atmosphere with density gradients and an
increasing magnetic field have been generally described. The Fokker-Planck equations are solved with regard to Coulomb collisions
and the effect of the electric field induced by this beam. The photon spectra and polarization degree in hard X-ray (10–300
keV) and microwave (1–80 GHz) emissions are simulated under different assumptions regarding the beam electron distribution
function. The simulation results are compared with the flare observations on March 10, 2001, and July 23, 2002, visible at
different position angles. It has been indicated that the coincidence of the theoretical photon spectra with simultaneous
observations of the hard X-ray and microwave emissions of these flares is the best for models that not only take into account
collisions, but also the electric field induced by electron fluxes propagating in flare loops with very weakly or moderately
converging magnetic fields. 相似文献
4.
Scaling properties of variable electric fields in the topside ionosphere have been investigated on scales s from ∼30 m to 2 km by FAST electric field observations with sample rate of 512 s−1, in sixteen events of the broadband ELF turbulence. It is shown that down to scales of a few hundred meters, the power of turbulent electric fluctuations is a power law, ∼s α. Scaling index α derived from the slope of logarithmic diagrams (LD) constructed by the discrete wavelet transform of data can be estimated as α = 2.2 ± 0.3, which is close to α estimate earlier reported for scales 1–30 km by electric field observations of the Dynamics Explorer 2 satellite. The behavior of α index is analyzed near the scale of the order of electron inertial length λe = c/ω0 (ω0 being the electron plasma frequency). At altitudes considered (700–2500 km), λe makes 100–900 m. We demonstrate that at scales ≤λe, a decrease of LD slope and deviation from the power law are typically observed. As pointed out in the discussion, this feature cannot be identified as a transition to the diffusion range, where dissipation of the turbulence occurs. 相似文献
5.
A. V. Roldugin V. G. Vorobjev V. C. Roldugin S. A. Chernouss 《Geomagnetism and Aeronomy》2010,50(1):34-40
The results of the ground-based optical observations of sunlit auroras, performed at Lovozero and Apatity observatories on
April 10 (event 1) and April 27, 2007(event 2), are presented. The observations were performed in the (OI) 557.7 nm emission,
using a new equipment based on a Fabry-Pérot interferometer connected to a PhotonMAX CCD camera. During event 1, the observations
were performed in the Harang discontinuity region at a low magnetic disturbance. It has been indicated that an auroral arc
was located in the polar part of the eastward electrojet, and the arc position coincides with the equatorward boundary of
structured precipitation (b2e). During event 2, auroras were observed within the average statistical boundaries of the auroral
oval and the region of structured precipitation under the conditions of rather high geomagnetic activity. However, during
the period of low geomagnetic activity, discrete auroras were registered at a geomagnetic latitude of ~64° on that day, which
is 3°—4° equatorward of the structured precipitation region. Such a low latitudinal position of auroras can be explained by
the effect of a high solar wind velocity, which was ~580 km/s during the period of observations. 相似文献
6.
R. T. Gushchina A. V. Belov V. N. Obridko B. D. Shelting 《Geomagnetism and Aeronomy》2010,50(4):436-442
Based on observations of long-term variations in galactic cosmic rays (CRs) on Earth and in the near-Earth space, we have
determined, using our own semiempirical model, modulation of galactic CRs during solar cycles 19–23. The modulation model
relates CR variations to the characteristics of the solar magnetic field obtained for the surface of the solar wind source
at distances of 2.50 and 3.25 solar radii. The main focus is CR behavior at the minimums of cycles 19–23 and specific features
of CR modulation at a prolonged (as compared to previous cycles) minimum of cycle 23, which is still ongoing. CR modulation
at minimums related to a change in the solar field dipole component during this period of the cycle has been considered. It
is indicated that the long-term variations in CRs are better described if the last two years (2007 and 2008) of cycle 23 with
anomalously low solar activity (SA) are included in the model. The role and value of the contribution of the cyclic variations
in each index used in the proposed CR modulation model to the observed CR modulation have been estimated. 相似文献
7.
The mesopause kinetic temperature at an altitude of 87 km measured with a SABER broadband radiometer installed on the TIMED
satellite and the hydroxyl molecule rotational temperature measured with a ground-spectrograph installed in high-latitude
eastern Siberia (Maimaga optical station; φ = 63°N, λ = 129.5°E) are compared. The data of the observations performed from
2002 to 2006 have been analyzed. The temperatures measured during the satellite passes at distances not larger than 300 km
from the intersection of the spectrograph sighting line with the hydroxyl emitting layer (∼87 km) have been compared. An analysis
of 130 cases of coincident measurements indicated that the average hydroxyl molecule rotational temperatures are systematically
lower than the average kinetic temperature at an altitude of the hydroxyl layer measured with SABER by 4.4 K (with a standard
deviation of 11.4 K). A seasonal dependence is observed regarding the difference between the ground-based and satellite measurements.
The difference decreases from 10 K in January to zero towards March. However, the time variations in the temperature obtained
with the ground-based device and on the satellite are similar. Based on the performed analysis, it has been concluded that
a series of hydroxyl rotational temperatures can be used to study temperature variations on different time scales, including
long-term trends at the temperature emission altitude (∼87 km). 相似文献
8.
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
9.
O. A. Ozhogina 《Geomagnetism and Aeronomy》2009,49(7):879-883
The method for measuring solar limb darkening has been proposed, and the formulas, describing the law of solar limb darkening
in the wings of the CaII H (396.849 nm) and K (393.369 nm) lines, have been derived. To operate at arbitrary points on the
Sun’s surface, it is necessary to know the law of solar limb darkening, which is specific in different spectral regions. The
procedure of spectrum correction for a flat field, proposed in our previous works, is based on comparing line-free spectral
regions with the solar center reference spectrum from the atlas by Brault and Neckel [1994]. 相似文献
10.
The response of the thermobaric characteristics of the high-latitude troposphere to short-term events attributed to solar
activity (solar cosmic rays and geomagnetic storms) has been investigated. The spatial manifestation of these disturbances
in the troposphere is shown to be of a “focal” character. It is found that the manifestation is most evident in the cold period
and depends on the properties of the underlying surface (land, ocean). The properties of the variations of the troposphere
air temperature in the manifestation “foci” on the standard isobaric surfaces, as well as the variations of the altitude profile
of temperature and the long-wave radiation flux at the upper boundary of the atmosphere, have been considered. The variations
of the heat content of the high-latitude troposphere after solar flares have been analyzed. The variation of the thermobaric
field is shown to be accompanied by the rearrangement of circulation forms in moderate and polar latitudes. The revealed properties
are completely explained within the mechanism proposed here for the solar activity effect on the climatic characteristics
of the troposphere. 相似文献
11.
Estimate of seasonal changes in the intensity of the infrared atmospheric system of molecular oxygen
A. I. Semenov V. I. Perminov K. V. Lipatov V. Yu. Khomich 《Geomagnetism and Aeronomy》2011,51(3):415-420
On the basis of measurements of the intensity of 1.58-μm emissions of the Infrared Atmospheric System of molecular oxygen
(IRAO2) conducted at the Zvenigorod scientific station of the Institute of Atmospheric Physics of the Russian Academy of Sciences
(φ = 55.7°N, λ = 36.8°E), seasonal variations are estimated for various solar zenith angles. Their amplitude has the maximum
value at the solar zenith angles χ
S
∼ 105–110°. It decreases at χ
S
∼ 125–130° and tends to zero at χ
S
∼ 80–85°. The comparison of currently measured values of the 1.58-μm emission intensity of the Infrared Atmospheric System
of molecular oxygen with published data on the intensity of this emission obtained in 1961–1966 reveals their decrease over
approximately 50 years. This fact is in good agreement with similar behavior of the emission intensity of atomic oxygen (557.7
nm) over the period considered. 相似文献
12.
Matthieu Kretzschmar Thierry Dudok de Wit Jean Lilensten Jean-Francois Hochedez Jean Aboudarham Pierre-Olivier Amblard Frederic Auchère Said Moussaoui 《Acta Geophysica》2009,57(1):42-51
The knowledge of solar extreme and far ultraviolet (EUV) irradiance variations is essential for the characterization of the
Earth’s upper atmosphere. For a long time, this knowledge has been based on empirical models, which are themselves based on
proxies of the solar activity. However, the accurate modeling and prediction of the Earth’s upper atmosphere necessitate to
improve the precision on the irradiance and its variations below about 200 nm. Here, we present a review of recent works made
by the authors that aim at quantifying the irradiance variability at these wavelengths, and that lead to new way of monitoring
the solar EUV/FUV irradiance spectrum. In more details, it is shown that the quantification of the high level of redundancy
in the solar spectrum variability allows to envisage measuring only a small portion of the spectrum without losing essential
knowledge. Finally, we discuss what should and could be measured in order to retrieve the solar extreme and far ultraviolet
spectrum. 相似文献
13.
The measurements of the critical frequencies of the ionospheric F2 layer based on vertical radiosounding, which was performed with a CADI digital ionosonde at the Voeykovo magnetic–ionospheric observatory in February 2013, have been considered. The observations have been compared with the upper atmosphere numerical model (UAM) data for three days that differ in the amplitude and the character of solar and magnetic activity and correspond to quiet and moderately disturbed states of the ionosphere. The work was performed in order to improve the methods for determining the ionospheric state by vertical sounding ionograms. The time variations in the F2 layer critical frequency, electric field vector zonal component, and thermospheric wind velocity meridional component have been analyzed. Calculations were performed with three UAM variants. The UAM version providing the best agreement with the CADI ionosonde data was the version in which the neutral temperature, neutral composition, and pressure gradients are calculated according to the MSIS empirical model and the horizontal neutral wind velocity is determined by the equation of motion with pressure gradients from MSIS. The calculated values corresponded to the measurements, except those for the evening, because the electron density at the ionospheric F2 layer maximum depends more strongly on electric fields and thermospheric wind velocities during this period. Thus, the indicated UAM version with the above limitations can be used to determine the state of the subauroral ionosphere. 相似文献
14.
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
15.
Results of studying the ionospheric response to solar flares, obtained based on the incoherent scatter radar observations
of the GPS signals and as a result of the model simulations, are presented. The method, based on the effect of partial “shadowing”
of the atmosphere by the globe, has been used to analyze the GPS data. This method made it possible to estimate the value
of a change in the electron content in the upper ionosphere during the solar flare of July 14, 2000. It has been shown that
a flare can cause a decrease in the electron content at heights of the upper ionosphere (h > 300 km) according to the GPS data. Similar effects in the formation of a negative disturbance in the ionospheric F region
were also observed during the solar flares of May 21 and 23, 1967, at the Arecibo incoherent scatter radar. The mechanism
by which negative disturbances are formed in the upper ionosphere during solar flares has been studied based on the theoretical
model of the ionosphere-plasmasphere coupling. It has been shown that an intense ejection of O+ ions into the above located plasmasphere under the action of a sharp increase in the ion production rate and the thermal
expansion of the ionospheric plasma cause the formation of a negative disturbance in the electron concentration in the upper
ionosphere. 相似文献
16.
K. G. Ivanov 《Geomagnetism and Aeronomy》2010,50(6):695-710
A more detailed scenario of one stage (August–November 2004) of the quasibiennial MHD process “Origination ... and dissipation
of the four-sector structure of the solar magnetic field” during the decline phase of cycle 23 has been constructed. It has
been indicated that the following working hypothesis on the propagation of an MHD disturbance westward (in the direction of
solar rotation) and eastward (toward the zone of active longitudes) with the displacement of the large-scale open solar magnetic
field (LOSMF) from this zone can be constructed based on LOSMF model representations and data on sunspot formation, flares,
active filaments, and coronal ejections as well as on the estimated contribution of sporadic energy release to the flare luminosity
and kinetic energy of ejections: (1) The “explosion” of the LOSMF singularity and the formation in the explosion zone of an
anemone active region (AR), which produced the satellite sunspot formation that continued west and east of the “anemone,”
represented a powerful and energy-intensive source of MHD processes at this stage. (2) This resulted in the origination of
two “governing” large-scale MHD processes, which regulated various usual manifestations of solar activity: the fast LOSMF
along the neutral line in the solar atmosphere, strongly affecting the zone of active longitudes, and the slow LOSMF in the
outer layers of the convection zone. The fronts of these processes were identified by powerful (about 1031 erg) coronal ejections. (3) The collision of a wave reflected from the zone of active longitudes with the eastern front of
the hydromagnetic impulse of the convection zone resulted in an increase in LOSMF magnetic fluxes, origination of an active
sector boundary in the zone of active longitudes, shear-convergent motions, and generation and destabilization of the flare-productive
AR 10696 responsible for the heliospheric storm of November 3–10, 2004. 相似文献
17.
The zone of anomalous diurnal variations in foF2, which is characterized by an excess of nighttime foF2 values over daytime ones, has been distinguished in the Southern Hemisphere based on the Intercosmos-19 satellite data.
In English literature, this zone is usually defined as the Weddell Sea anomaly (WSA). The anomaly occupies the longitudes
of 180°–360° E in the Western Hemisphere and the latitudes of 40°–80° S, and the effect is maximal (up to ∼5 MHz) at longitudes
of 255°–315° E and latitudes of 60°–70° S (50°–55° ILAT). The anomaly is observed at all levels of solar activity. The anomaly
formation causes have been considered based on calculations and qualitative analysis. For this purpose, the longitudinal variations
in the ionospheric and thermospheric parameters in the Southern Hemisphere have been analyzed in detail for near-noon and
near-midnight conditions. The analysis shows that the daytime foF2 values are much smaller in the Western Hemisphere than in the Eastern one, and, on the contrary, the nighttime values are
much larger, as a result of which the foF2 diurnal variations are anomalous. Such a character of the longitudinal effect mainly depends on the vertical plasma drift
under the action of the neutral wind and ionization by solar radiation. Other causes have also been considered: the composition
and temperature of the atmosphere, plasma flows from the plasmasphere, electric fields, particle precipitation, and the relationship
to the equatorial anomaly and the main ionospheric trough. 相似文献
18.
A. R. Breen W. A. Coles R. R. Grail M. T. Klinglesmith J. Markkanen P. J. Moran B. Tegid P. J. S. Williams 《Annales Geophysicae》1997,14(12):1235-1245
EISCAT observations of interplanetary scintillation have been used to measure the velocity of the solar wind at distances between 15 and 130R (solar radii) from the Sun. The results show that the solar wind consists of two distinct components, a fast stream with a velocity of 800 km s–1 and a slow stream at 400 kms–1. The fast stream appears to reach its final velocity much closer to the Sun than expected. The results presented here suggest that this is also true for the slow solar wind. Away from interaction regions the flow vector of the solar wind is purely radial to the Sun. Observations have been made of fast wind/slow wind interactions which show enhanced levels of scintillation in compression regions. 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.
Bogusław M. Domański 《Acta Geophysica》2007,55(3):267-287
An analysis of source parameters of the two unexpected earthquakes from the Kaliningrad (Russia) area is presented. The earthquakes
occurred on 21 September 2004 at 11:05:01 and 13:32:31 UT, respectively. The first event was located at the latitude φ = 54.924°N and the longitude λ = 20.120°E, with a depth h = 16 km, and the second event at φ = 54.876°N, λ = 20.120°E and h = 20 km.
Magnitudes Mw of the two events were very similar: 5.1 and 5.2. The magnitude values reported by various international data centers have
been meaningfully different. The reason is the presence of high-frequency components in Z velocity component of the S wavefield.
They were observed along the direction defined by two stations, BLEU in Sweden and SUW in Poland, located in opposite sides
of the source. Along the direction perpendicular to it, the effects are relatively very small. The high-frequency waves are
understood to mean components in the 6–8 Hz band for event 1 and 2-4 Hz for event 2. The effects in question are also clearly
visible on displacement spectrograms. The magnitude values calculated at such stations from S-wave amplitudes or from seismic
spectra are clearly overestimated and are close to 6. Therefore, we made a careful selection of channels in order to determine
the spectral parameters and, on this basis, the source parameters.
The size of the source is relatively small, of about 2 km. The closest seismic station is at 100 source radii from the source.
One can clearly see the effect of the TT zone which markedly reduces the seismic moment value for seismic stations laying
on the opposite sides of the source. Both events have very similar spatial distributions of the source parameters: magnitude,
seismic moment and radius. 相似文献