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1.
Results of Russian experiments dealing with the impact of powerful HF radiowaves on the high-latitude ionosphere using the EISCAT facilities 总被引：1，自引：0，他引：1
N. F. Blagoveshchenskaya T. D. Borisova M. T. Rietveld T. K. Yeoman D. M. Wright M. Rother H. Lühr E. V. Mishin C. Roth 《Geomagnetism and Aeronomy》2011,51(8):1109-1120
We present the results of complex experiments dealing with the impact of powerful HF radiowaves on the high-latitude ionosphere
using the European Incoherent Scatter Scientific Association (EISCAT) facilities. During the ionospheric F-region heating by powerful extraordinary (X-mode) polarized HF radiowaves under the conditions of heating near the critical
f
H frequency f
H ≈ f
x
F2 of the extraordinary wave of the F2-layer, we were first to detect the excitation of intense artificial small-scale ionospheric irregularities (ASIs), accompanied
by electron temperature increases by approximately 50%. The results of coordinated satellite and ground-based observations
of the powerful HF radiowave impact on the high-latitude ionosphere are considered. During ionospheric F-region heating by powerful HF radiowaves of ordinary polarization (O-mode) during evening hours, the phenomenon of ion outflow
accompanied by electron temperature increases and thermal plasma expansion was revealed. Concurrent DMSP-F15 satellite measurements
at a height of about 850 km indicate an O+ ion density increase. The CHAMP satellite observations identified ULF emissions at the modulation frequency (3 Hz) of the
powerful HF radiowave, generated during modulated emissions of the powerful HF radiowave of O-polarization and accompanied
by a substantial increase in the electron temperature and ASI generation. 相似文献
2.
This work is devoted to a numerical simulation of the equatorial ionosphere, performed using the GSM TIP model completed with
a new block for calculating the electric field. It has been indicated that the usage of the wind system calculated according
to the MSIS-90 model makes it possible to reproduce the electromagnetic drift velocities at the equator, the effect of the
F2-layer stratification, and the appearance of the F3 layer in the equatorial ionosphere. The calculations performed using the modified GSM TIP model made it possible to detect
a maximum in the electron density vertical profile at an altitude of ∼1000 km, formed by H+ ions, which we called the G layer. If this layer actually exists, it can be observed during sounding the low-latitude ionosphere from satellites during
dark time of day. 相似文献
3.
The paper is dedicated to the studies of formation mechanisms of additional layers in the equatorial ionosphere carried out using numerical simulations with use of the Global Self-Consistent Model of the Thermosphere, Ionosphere, and Protonosphere (GSM TIP) modified in the part of the solution of the electric field equation in the Earth’s ionosphere. Calculations were preformed for quiet geomagnetic conditions using the MSIS-90 model for the calculation of thermospheric parameters. The obtained spatio-temporal pattern of thermospheric circulation and the variations in the dynamo electric field obtained on its basis make it possible to reproduce the stratification effect of the F2 layer and the appearance of the F3 layer in the equatorial ionosphere due to the action of the nonuniform in height zonal electric field at the geomagnetic equator. On the basis of the earlier presented results of calculations using the modified GSM TIP model, the appearance of a maximum in the vertical profile of the electron density at a height of ∼1000 km formed by H+ ions, which we called the G layer, has been predicted. Numerical simulations showed that this layer is formed by the meridional component of the thermospheric wind and is related to the formation of the nighttime midlatitude maximum at heights of the ionospheric F region. 相似文献
4.
The expression for the increment of instability and decrement of diffusion damping of gradient drift waves for ionospheric
altitudes above the F
2 layer maximum is obtained. The gradient drift instability is used to interpret the observations of spread F in the region of large-scale horizontal irregularities of the electron density. Two types of such irregularities observed
on board the Intercosmos-19 (IC-19) satellite in the region of low latitudes (a peak of the density in the dusk ionosphere
and a trough of the density in the dawn ionosphere) are considered. It is shown that the observed gradients of the density
and electric field values in the dawn and dusk ionospheric sectors are quite sufficient for the instability development criterion
to be satisfied in both considered cases. 相似文献
5.
This paper presents more data on the properties of type-1 irregularities in the nighttime midlatitude E-region ionosphere. The measurements were made with a 50-MHz Doppler radar system operating in Crete, Greece. The type-1 echoes last from several seconds to a few minutes and are characterized by narrow Doppler spectra with peaks corresponding to wave phase velocities of 250–350 m/s. The average velocity of 285 m/s is about 20% lower than nominal E-region ion-acoustic speeds, probably because of the presence of heavy metallic ions in the sporadic-E-layers that appear to be associated with the mid-latitude plasma instabilities. Sometimes the type-1 echoes are combined with a broad spectrum of type-2 echoes; at other times they dominate the spectrum or may appear in the absence of any type-2 spectral component. We believe these echoes are due to the modified two-stream plasma instability driven by a polarization electric field that must be larger than 10 mV/m. This field is similar in nature to the equatorial electrojet polarization field and can arise when patchy nighttime sporadic-E-layers have the right geometry. 相似文献
6.
V. L. Khalipov A. E. Stepanov G. A. Kotova S. E. Kobyakova V. V. Bogdanov A. B. Kaisin V. A. Panchenko 《Geomagnetism and Aeronomy》2016,56(5):535-544
Vertical and horizontal plasma drifts are investigated during the polarization jet (PJ) detection in the F2 ionospheric layer based on the Doppler measurements at the Yakutsk meridian chain of subauroral ionospheric stations. It is shown that the velocities of vertical and horizontal drifts are significantly higher than the background motion during PJ observation periods. The ionospheric plasma motion direction changes from upward to downward on the polar edge of the main ionospheric trough. Doppler measurements on the DPS-4 ionosondes are compared with the simultaneous measurements of the plasma drift on the DMSP satellites during their passage near the Yakutsk meridian. The two kinds of measurements are in good agreement with each other. During the magnetic storm of June 23, 2005, by measurements of the DMSP satellites, the velocities of upward plasma flows were 1.0–1.4 km/s at a satellite altitude of 850 km. In the ionospheric F region, this speed corresponds to 150 m/s. According to satellite measurements, the westward drift velocity reached 2.5 km/s. The development of the polarization jet in the ionosphere was accompanied by a tenfold decrease in the electron density in 15–30 min. 相似文献
7.
Using data from ground-based ionospheric sounding stations, we studied the morphologic features of the disturbance pattern
of the electron concentration at the midlatitude F2-layer maximum (NmF2) in the period of a magnetic superstorm, which began on July 15, 2000. In the Southern (winter) Hemisphere in the latitudinal
sector, where the main storm phase began after sunrise, negative NmF disturbances were observed at quite high midlatitudes both day and night; whereas large positive NmF disturbances took place at lower midlatitudes in nighttime hours. In the Northern (summer) Hemisphere at latitudes where
the main storm phase occurred in the local evening, only long-term negative disturbances were observed in daytime and nighttime
hours; whereas at latitudes where the main storm phase began in the afternoon, NmF2 experienced both negative and positive disturbances. Based on analysis of data of KOMPSAT-l, ROCSAT-1, DMSP F13, F14, and
F15 satellites, we present clear arguments for the viewpoint of many authors that it is just the enhancement of the eastward
electric field in the evening sector that led to formation of the large-scale trough in the nighttime low-latitude upper ionosphere.
This field enhancement was due to penetration of the magnetospheric electric field to low latitudes, not to the dynamo action
of the disturbed neutral wind. It is also shown that, due to equatorward expansion of the magnetospheric convection system
during the main storm phase, the plasmapause and the main ionospheric trough were shifted to a magnetic latitude of 40° (L ∼ 1.7). 相似文献
8.
Prof. Dr. T. Nagata 《Pure and Applied Geophysics》1958,39(1):96-101
Summary Disturbances in the critical frequency of theF2-region of the ionosphere at Watheroo on international magnetically disturbed days are analyzed together with simultaneous geomagnetic data at the same station. The results show that the daily average disturbanceDm (foF2) becomes negative or positive according as the maximum of the disturbance daily variationSD (foF2) takes place in night time or in daytime respectively. This fact may show that bothDm (foF2) andSD (foF2) are due to the condition that the daytime increase in the daily variation of theF2-region is reduced or enhanced owing to vertical drift of the ionosphere caused by electric currents responsible for geomagneticSD. 相似文献
9.
This paper studies the role of magnetospheric factors, such as convection and energetic electron precipitation during the
formation of positive disturbances in the total electron content under the conditions of the summer evening ionosphere. à
numerical model of the ionosphere and plasmasphere, where time variations in the magnetospheric convection velocity and electron
precipitation parameters correspond to the main phase of a magnetic storm, has been used for this purpose. It has been indicated
that the total electron content sharply increases (the “dusk effect”) in the eastern and western sectors at approximately
the same geomagnetic latitudes corresponding to the subauroral zone provided that a sudden storm commencement is registered
in the morning hours. local time. This peak of the total electron content is formed as a result of joint reconstruction of
the magnetospheric convection pattern and energetic electron precipitation during the main phase of a storm. In this case,
magnetospheric convection plays the main role, raising the F2 layer by 40–80 km into the region with a lower recombination rate. 相似文献
10.
T. Ogawa 《Annales Geophysicae》1997,14(12):1454-1461
We briefly overview the radar observations that have been made for 30 years at Syowa Station, Antarctica for studying small-scale electron-density irregularities in the southern high-latitude E- and F-region ionosphere. Some observational results (i.e., long-term variations of radio aurora, Doppler spectra with narrow spectral widths and low Doppler velocities, and simultaneous observations of radar and optical auroras) from VHP radars capable of detecting 1.3- to 3-m scale irregularities are presented. A new 50-MHz radar system equipped with phased-antenna arrays began operation in February 1995 to observe two-dimensional behaviors of E-region irregularities. An HF radar experiment also began in February 1995 to explore decameter-scale E- and F-region irregularities in the auroral zone and polar cap. These two radars will contribute to a better understanding of the ionospheric irregularities and ionospheric physics at southern high latitudes. 相似文献
11.
Morphological analysis of variations of the critical frequency foF2 in the midlatitude ionosphere at various sectors of local time is carried out on the basis of data from ground-based stations
of vertical sounding of the ionosphere in the period when during use of the incoherent scatter radar at Saint-Santin an anomalously
strong increase in the electric field was observed at heights of the ionospheric F region in the period of enhanced geomagnetic activity (4+ < Kp < 6−). The obtained picture of the space-time distribution of disturbances in foF2 makes it possible to assume that they could be caused by penetration to middle latitudes of the large-scale electric field
of the magnetospheric convection directed westward in the nighttime and morning hours and eastward in the noon and evening
sectors. 相似文献
12.
N. V. Isaev V. M. Kostin G. G. Belyaev O. Ya. Ovcharenko E. P. Trushkina 《Geomagnetism and Aeronomy》2010,50(2):243-255
The measurements on board the Cosmos-1809 satellite of various parameters of the topside ionosphere plasma during more than
ten typhoons in various regions are analyzed. It is shown that specific zones of increased pressure of the electron gas, electric
field, and intense ion oscillations are formed during the intensification stage. In some cases the “typhoon eye” is formed
over the tropical depression zone in the ionosphere, that is, the region with sharply decreased plasma density and pressure
is observed a day and more prior to the moment when it happens in the atmosphere. 相似文献
13.
Using mass-spectrometric measurement data from the Dynamics Explorer 2 satellite, we investigated the distribution of medium-scale
acoustic gravity waves (AGWs) at altitudes of the F-region of the ionosphere. It is shown that the planetary field of AGWs contains a regular and a sporadic component. The regular
distribution of AGWs involves active polar areas (where the ionosphere is highly disturbed) and a relatively calm equatorial
area. Sporadic AGWs are isolated and spatially localized wave packets that are distinguished against the background of the
regular distribution of the wave field. We generated a directory containing observations of sporadic AGW for the period January–February
1983 and performed a statistical analysis of their relation to earthquakes. 相似文献
14.
The purpose of this paper is to study the effect of the main ionospheric trough location on the form of oblique sounding ionograms on the Murmansk-St. Petersburg subauroral radio path. Using a mathematical model of the high-latitude ionosphere, we have calculated four different distributions of electron density along the radio path. One of the distributions has been obtained when the trough is absent, and the remaining three distributions contain troughs of approximately identical depth and width but located at different distances from the ends of the radio path. Using the program of two-dimensional ray tracing, we numerically synthesized oblique-incidence ionograms for each of the four obtained distributions of electron density. The calculations have shown that the location of the main ionospheric trough affects considerably the shape of oblique-incidence ionograms. 相似文献
15.
A mathematical modeling method and the global numerical model of the Earth’s upper atmosphere were used to study nighttime enhanced electron density regions (EEDRs) in the ionospheric F2 layer and their possible manifestations at altitudes of the Earth’s plasmasphere. It has been established that EEDRs are formed owing to latitudinally nonuniform longitudinal (along the magnetic field) plasma flows from the plasmasphere into the nighttime ionosphere and the wind transport of ions along geomagnetic field lines. The specific features of the effect of ionospheric-plasmaspheric plasma transport processes, related to their three-dimensional character, on EEDRs have been revealed. 相似文献
16.
Complex ionograms from the Intercosmos-19 satellite with strongly delayed and sometimes multiple reflections from the Earth are considered. An analysis shows that these reflections are usually associated with sharp horizontal gradients of the ionospheric plasma. Such gradients are formed on the walls of the main ionospheric trough, at peaks of electron density, and on the inner and, especially frequently, on the outer slope of the crest of the equatorial anomaly. In one case, distant reflections from the Earth (DREs) formed near the equator, when the satellite in perigee was lower than the F2-layer maximum height. A quantitative interpretation of the most typical cases of DREs is given based on ray tracing. For this purpose, the model of the ionosphere under the satellite is developed, ray paths are calculated, and model ionograms are formed. The good agreement between experimental and model ionograms allows us to conclude that the task of interpreting complicated ionograms obtained by Intercosmos-19 with DRE has been solved successfully. 相似文献
17.
Experiments on the generation of artificial electromagnetic pulsations constitute an important part of investigations of the
magnetosphere-ionosphere system with the use of an active action. The investigation of the generation of magnetic pulsations
in the Pc1 frequency range has shown that the response of the ionosphere to heating is detected only in a few experiments.
Although the primary perturbed parameter is the electron temperature, the efficiency of the generation of pulsations is determined
by the perturbations of the ionospheric conductivity. The magnitude of these hertz perturbations depends complexly on the
electron density profile and the parameters of a pump wave. The numerical experiment demonstrates the determining effect of
the electron density in the D region on the magnitude of perturbations of the ionospheric conductivity. Under conditions of a low electron density, it
is impossible to create a large perturbation of the conductivity in the Pc1 frequency range, although perturbations of the
electron temperature can be large in this case. In view of a large number of electrons at altitudes of 70–90 km, which absorb
a considerable fraction of the energy of a high-frequency wave, the electron temperature in the E region of the ionosphere cannot be sharply increased, but the amplitude of the variations of the ionospheric conductivity
in this case is larger than that for the profiles with a low electron density. In the presence of the developed D region, the efficiency of the modification of the conductivity in the indicated frequency range can be increased by choosing
the optimal frequency and polarization of the pump wave. A low efficiency of the experiments on the generation of artificial
magnetic pulsations in the Pc1 frequency range is apparently explained by the fact that they were performed in winter in the
absence of a well-developed D region of the ionosphere. 相似文献
18.
The profiles of the plasma density in the topside ionosphere, according to the data of sounding on board the Intercosmos-19 satellite, are presented. It is shown that the large-scale fluctuations of the plasma density can be related to the propagation and attenuation of the atmospheric waves (e.g., acoustic gravity waves) in the dynamo region of the ionosphere. In the topside ionosphere, suprathermal particle fluxes can be formed and the plasma density can be modulated at an attenuation of small-scale electrostatic fluctuations of the plasma electron component in plasma pits. Plasma vortices can be formed when polarization fluxes of charged particles escape from regions of heating. The vortex field imparts stability to the inhomogeneous plasma structure, necessary for experimental detection of this structure. 相似文献
19.
The results of an analysis of the possible effect of auroral electron fluxes on the effective recombination coefficient αeff in the ionosphere are presented. It is shown that the αeff value in the E-region of the ionosphere is determined mainly by the physical-chemical properties of the medium. In the F1-layer of the ionosphere, the effective recombination coefficient becomes dependent on both the value of the energy flux and the type of the energy spectrum of the auroral electron flux. 相似文献
20.
Tamara L. Gulyaeva 《Acta Geophysica》2007,55(2):253-266
Variations of the upper boundary of the ionosphere (UBI) are investigated based on three sources of information: (i) ionosonde-derived
parameters: critical frequency foF2, propagation factor M3000F2, and sub-peak thickness of the bottomside electron density profile; (ii) total electron content (TEC) observations from signals
of the Global Positioning System (GPS) satellites; (iii) model electron densities of the International Reference Ionosphere
(IRI*) extended towards the plasmasphere. The ionospheric slab thickness is calculated as ratio of TEC to the F2 layer peak electron
density, NmF2, representing a measure of thickness of electron density profile in the bottomside and topside ionosphere eliminating the
plasmaspheric slab thickness of GPS-TEC with the IRI* code. The ratio of slab thickness to the real thickness in the topside ionosphere is deduced making use of a similar ratio
in the bottomside ionosphere with a weight Rw. Model weight Rw is represented as a superposition of the base-functions of local time, geomagnetic latitude, solar and magnetic activity.
The time-space variations of domain of convergence of the ionosphere and plasmasphere differ from an average value of UBI
at ∼1000 km over the earth.
Analysis for quiet monthly average conditions and during the storms (September 2002, October–November 2003, November 2004)
has shown shrinking UBI altitude at daytime to 400 km. The upper ionosphere height is increased by night with an ‘ionospheric
tail’ which expands from 1000 km to more than 2000 km over the earth under quiet and disturbed space weather. These effects
are interposed on a trend of increasing UBI height with solar activity when both the critical frequency foF2 and the peak height hmF2 are growing during the solar cycle. 相似文献