共查询到20条相似文献，搜索用时 31 毫秒
1.
Auroral precipitating electrons pass through an acceleration region before entering the atmosphere. Regardless of what produces it, a parallel electric field is assumed to cause the acceleration. It is well known that from kinetic theory an expression for the corresponding upward field-aligned current can be calculated, which under certain assumptions can be linearized to j = KV. The K constant, referred to as the Lyons-Evans-Lundin constant, depends on the source density and thermal energy of the magnetospheric electrons; it is an important parameter in magnetosphere-ionosphere coupling models. However, the K parameter is still rather unknown, and values are found in a wide range of 10–8–10–10Sim–2. In this study, we investigated how the type of auroral structure affects the K values. We look at onset and westwards-travelling surge (WTS) events and make comparisons with earlier results from observations of more stable auroral arcs. A new analysis technique for studying those magnetospheric parameters using ground-based measurements is introduced. Electron density measurements are taken with the EISCAT radar, and through an inversion technique the flux-energy spectra are calculated. Source densities, thermal energies and potential drops are estimated from fittings of accelerated Maxwellian distributions. With this radar technique we have the possibility to study the changes of the mentioned parameters during the development of onsets and the passage of surges over EISCAT. The study indicates that the linearization of the full Knight formulation holds even for the very high potential drops and thermal temperatures found in the dynamic onset and WTS events. The values of K are found to be very low, around 10–11Sm–2 in onset cases as well as WTS events. The results may establish a new technique where ionospheric measurements are used for studying the ionosphere-magnetosphere coupling processes. 相似文献
2.
A kinetic theory is necessary to explain the electron flows forming strong field-aligned currents in the auroral region. Its construction in this paper is based on the following propositions. (a) In the equatorial region, the arrival of electrons through the lateral surface of the magnetic flux tube is compensated for by their escape along the magnetic field. This is provided by action of the pitch-angle diffusion mechanism in the presence of plasma turbulence concentrated in this region. (b) Outside the equatorial region, the distribution functions of trapped and precipitating particles become “frozen.” The distributions and particle concentrations are calculated there in a model with conservation of the total energy and the magnetic moment. (c) The quasi-neutrality condition yields a large-scale parallel electric field, which contributes to the conserved total energy. In this field, the electron acceleration occurs, causing strong field-aligned currents directed upward from the ionosphere. 相似文献
3.
Further analysis of energetic electron precipitation at the evening sector of magnetosphere is performed. In the framework of the quantitative model of cyclotron wave-particle interactions developed in the previous Pasmanik et al. paper, the case of finite spread over energies of initial energetic electron distribution is studied. The solution for distribution function of energetic electron is found. The energetic spectrum of trapped and precipitating electrons and whistler wave spectrum are analysed. 相似文献
4.
E. E. Titova T. A. Yahnina A. G. Yahnin B. B. Gvozdevsky A. A. Lyubchich V. Yu. Trakhtengets A. G. Demekhov J. L. Horwitz F. Lefeuvre D. Lagoutte J. Manninen T. Turunen 《Annales Geophysicae》1997,16(1):25-33
Specific type of energetic electron precipitation accompanied by a sharp increase in trapped energetic electron flux are found in the data obtained from low-altitude NOAA satellites. These strongly localized variations of the trapped and precipitated energetic electron flux have been observed in the evening sector near the plasmapause during recovery phase of magnetic storms. Statistical characteristics of these structures as well as the results of comparison with proton precipitation are described. We demonstrate the spatial coincidence of localized electron precipitation with cold plasma gradient and whistler wave intensification measured on board the DE-1 and Aureol-3 satellites. A simultaneous localized sharp increase in both trapped and precipitating electron flux could be a result of significant pitch-angle isotropization of drifting electrons due to their interaction via cyclotron instability with the region of sharp increase in background plasma density. 相似文献
5.
6.
在极区电离层模式中,考虑了软电子沉降引起的电离,并对差分方法的应用提出了改进意见.模拟了不同特征的沉降电子对极区电离层的影响,发现平均能量低的电子束能够形成明显的电离层F层,平均能量较高的电子束能使得最大电离的高度下移,形成明显的E层,甚至其电子浓度高于F层.将电子沉降的卫星测量结果作为电离层模型的输入,所得F层临频与观测结果符合较好.通过分析中山站电离层统计结果,综合电子沉降在极隙区的分布特征和上述模拟结果,认为中山站磁中午现象主要由电子沉降所致. 相似文献
7.
《Journal of Atmospheric and Solar》2003,65(2):211-217
Multi-instrument experimental data are analyzed to determine the main processes forming a deep trough in the electron density at F-peak altitudes during a strong magnetic storm (Kp⩾5). Previous attempts to explain the observations were not successful. The model we use to interpret the data includes production of vibrationally excited N2 in the region poleward of the trough and its transport into the trough region by a southward wind. The main source of the vibrationally excited N2 is secondary electrons created by precipitating electrons. Joule heating and dissipation of precipitating electron energy create a pressure gradient and induce the southward wind. According to the model calculations, such a system of processes can cause the very strong electron density depletion observed by the Millstone Hill incoherent scatter radar on April 20, 1985. An important additional condition for such a deep trough is a decrease in the [O]/[N2] ratio. The total energy flux and average energy of precipitating electrons just poleward of the trough is also a factor. 相似文献
8.
《Journal of Atmospheric and Solar》2000,62(10):889-900
The polar ionospheric X-ray imaging experiment (PIXIE) and the UV imager (UVI) onboard the Polar satellite have provided the first simultaneous global scale views of the patterns of electron precipitation through imaging of the atmospheric X-ray bremsstrahlung and the auroral UV emissions. While the UV images in the Lyman–Birge–Hopfield-long band used in this study respond to the total electron energy flux which is usually dominated by low-energy electrons (<10 keV), the PIXIE images of X-ray bremsstrahlung above ∼2.7 keV respond to electrons of energy above ∼3 keV. Comparison of precipitation features seen by UVI and PIXIE provides information on essentially complementary energy ranges of the precipitating electrons. In this study an isolated substorm is examined using data from PIXIE, UVI, ground-based measurements, and in situ measurements from high- and low-altitude satellites to obtain information about the global characteristics during the event. Results from a statistical study of isolated substorms, which has reported a significant difference in the patterns of energetic electron precipitation compared to the less energetic precipitation are confirmed. A localized maximum of electron precipitation in the morning sector delayed with respect to substorm onset is clearly seen in the X-ray aurora, and the time delay of this morning precipitation relative to substorm onset strongly indicates that this intensification is caused by electrons injected in the midnight sector drifting into a region in the dawnside magnetosphere where some mechanism effectively scatter the electrons into the loss cone. In this study, we also present the results from two low-altitude satellite passes through the region of the localized maximum of X-ray emission in the morning sector. Measured X rays are compared with X-ray fluxes calculated from the electron spectral measurements. By fitting the electron spectra by a sum of two exponentials we obtain fairly good agreement between calculated and directly measured X-ray flux profiles. 相似文献
9.
L. V. Tverskaya B. V. Marjin M. V. Teltsov T. A. Ivanova 《Geomagnetism and Aeronomy》2009,49(6):750-754
The simultaneous measurements of the boundary of the trapped radiation region, where auroral electrons precipitate, on the
Meteor-3M satellite (the circular polar orbit at an altitude of ∼1000 km) and the westward electrojet dynamics during the
main phase of a strong (Dst = −263 nT) magnetic storm that occurred on May 15, 2005, are analyzed. At the end of the first
hour of the storm main phase, the nightside boundary of the trapped radiation region and the peak of the precipitating electron
fluxes with a energies of ∼1 keV shifted toward the Earth to L ∼ 3. The westward electrojet center approached the same L shell.
Near the boundary of the trapped radiation region, the auroral electron spectrum had the shape of typical inverted V. The
differential spectrum maximum shifted to an energy of ∼100 eV, when the latitude decreased by ∼1°. The nightside boundary
of the trapped radiation region, the electron precipitation equatorward boundary, and the westward electrojet center are compared
with the known empirical dependences of the position of these structures on the Dst variation amplitude. 相似文献
10.
Thirteen events of high-latitude ionospheric travelling convection vortices during very quiet conditions were identified in the Greenland magnetometer data during 1990 and 1991. The latitudes of the vortex centres for these events are compared to the energetic electron trapping boundaries as identified by the particle measurements of the NOAA 10 satellite. In addition, for all events at least one close DMSP overpass was available. All but one of the 13 cases agree to an exceptional degree that: the TCV centres are located within the region of trapped, high energy electrons close to the trapping boundary for the population of electrons with energy greater than > 100 keV. Correspondingly, from the DMSP data they are located within the region of plasmasheet-type precipitation close to the CPS/BPS precipitation boundary. That is, the TCV centres map to deep inside the magnetosphere and not to the magnetopause. 相似文献
11.
S. I. Musatenko A. V. Agapitov E. V. Kurochka A. S. Slipchenko V. V. Fomichev A. K. Markeev S. M. Kutuzov 《Geomagnetism and Aeronomy》2006,46(5):667-675
Results of the spectral measurements of ionospheric noise in the meter band are presented. The events lasting several milliseconds (the emission maximum of which drifts upward (in frequency), is reflected (stops), and drifts downward) have been distinguished. Moreover, multiple harmonics are observed. The frequency-time structure of such events have been considered from the viewpoint of registration of the electron beam synchrotron emission harmonics at ionospheric altitudes in the geomagnetic field. The model calculations of the frequency-time structure of ionospheric radio noise bursts drifting in frequency have been performed taking into account the measurement conditions. It has been indicated that the model electron radio noise bursts agree with the measured bursts reflecting from the ionosphere at altitudes of 100–180 km. The model of the monoenergetic beam of electrons precipitating from the radiation belt (L ～ 2.0–2.8) into the ionosphere has been proposed. 相似文献
12.
本文利用中国北极黄河站多波段全天空极光观测数据,选取稳定的日侧极光弧,统计研究了极光强度比I_(557.7)/I_(630.0)与极光发光强度I_(557.7)的相关关系.发现I_(557.7)在午前暖点和午后热点区附近出现极大值,分别为2.2kR和2.9 kR;而I_(630.0)在磁正午出现极大值,为1.5kR.当I_(557.7)从0.1kR增加到10kR时,极光强度比I_(557.7)/I_(630.0)也由0.2增加到9.结合DMSP卫星探测的沉降粒子能谱数据,找到17个DMSP卫星穿越黄河站上空极光弧的事件,共穿越40条极光弧.得到了沉降电子的平均能量正比于极光强度比I_(557.7)/I_(630.0),沉降电子的总能通量正相关于极光强度I_(557.7)的关系式.利用该关系式反演所有极光弧的电子能谱,发现在午前和午后扇区,产生极光弧的沉降电子主要来源于等离子体片边界层;在高纬出现强度较弱的弧,对应等离子体幔区域.在磁正午附近,沉降电子的平均能量较低,极光弧处于低纬一侧,粒子源区主要是低纬边界层. 相似文献
13.
Results of an analysis of the double layer kinetic characteristics in the case of kappa distributions are presented. The direct and classical double layers and double layers in a trap have been considered. It has been indicated that the restrictions imposed by the Bom-Block criteria are removed if trapped particle populations between the ionosphere and the electrostatic potential jump and between conjugate potential jumps are considered. The dependence of particle fluxes through the double layer in a trap, replacing the Langmuir criterion of a classical double layer, has been obtained. The applicability of the obtained results to the solution of the problem of particle acceleration in the auroral plasma has been discussed. The dependence of the current carried by precipitating magnetospheric electrons on the field-aligned potential jump and kappa distribution characteristics has been obtained. 相似文献
14.
Measurements of solar cosmic ray (SCR) protons in the magnetosphere can be used to verify models of the Earth’s magnetic field.
The latitudinal profiles of precipitating SCRs with energies of 1–90 MeV were measured on the CORONAS-F low-orbiting satellite
during a strong magnetic storm on October 29–30, 2003. A flux of precipitating protons can remain equal to the interplanetary
flux only due to a strong pitch angle diffusion that originates when the radius of the field line curvature is close to that
of the particle rotation Larmor radius. The observed boundaries of the strong diffusion region can be compared with the boundaries
anticipated according to the models of the magnetic field of the Earth’s magnetosphere. The adiabaticity parameter values,
calculated for several instants of the CORONAS-F satellite pass based on the TS05 and parabolic models, do not always correspond
to measurements. How possible changes in the model configurations of the magnetic field can allow us to eliminate discrepancies
with the experiment and to explain why solar protons with energies of several megaelectronvolts penetrate deep in the Earth’s
inner magnetosphere is considered here. 相似文献
15.
Increase in the nighttime high-latitude nonthermal emissions in the mesosphere and lower thermosphere in the 4.3 and 15 μm
CO2 bands during solar proton events has been estimated for the first time. The estimations have been performed for protons with
energies not lower than 1 MeV precipitating into the atmosphere. A strong increase in the 4.3 μm emission can be anticipated
during the above events; however, a substantial increase in the 15 μm emission is improbable. The 4.3 μm emission can increase
only above approximately 80 km regardless of the energy of precipitating protons. The excitation of CO2 vibrational states, transitions from which generate the 4.3 μm emission, is caused by the vibrational excitation of N2 molecules due to collisions with secondary electrons, produced during solar proton events, and the following transfer of
this excitation to CO2(0001) molecules during N2-CO2 collisions.
Original Russian Text ? V.P. Ogibalov, S.N. Khvorostovskii, G.M. Shved, 2006, published in Geomagnetizm i Aeronomiya, 2006,
Vol. 46, No. 2, pp. 159–167. 相似文献
16.
This paper presents the development of a seismological model for the Tehran area. This modelling approach, which was originally developed in Eastern North America, has been used successfully in other parts of the world including Australia and China for simulating accelerograms and elastic response spectra. Parameters required for input into the model were inferred from seismological and geological information obtained locally. The attenuation properties of the earth crust were derived from the analysis of accelerogram records that had been collated from within the region in a previous study. In modelling local modifications of seismic waves in the upper crust, shear-wave velocity profiles have been constructed in accordance with the power law. Information inferred from micro-zonation studies (for near-surface conditions) and from measurements of teleseismic P-waves reflected from the deeper crusts as reported in the literature has been used to constrain parameters in the power-law relationships. This method of obtaining amplification factors for the upper crust distinguishes this study from earlier studies in the Tehran area (in which site amplification factors were inferred from the H/V ratio of the recorded ground motions). The regional specific seismological model so constructed from the study enabled accelerograms to be simulated and elastic response spectra calculated for a series of magnitude–distance combinations. Importantly, elastic response spectra calculated from the simulated accelerograms have been compared with those calculated from accelerograms recorded from earthquakes with magnitudes ranging between M6.3 and M7.4. The peak ground velocity values calculated from the simulated accelerograms have also been correlated with values inferred from macro-seismic intensity data of 17 historical earthquakes with magnitudes varying between 5.4 and 7.7 and with distances varying between 40 and 230 km. This paper forms part of the long-term strategy of the authors of applying modern techniques for modelling the attenuation behaviour of earthquakes in countries which are lacking in instrumental data of earthquakes. 相似文献
17.
《Journal of Atmospheric and Solar》2008,70(10):1281-1288
Simultaneous and complete temperature profiles from near ground to about 100 km are essential for studying the dynamical coupling between different atmospheric layers. They are acquired by combining three different lidar techniques at Wuhan, China (30.5°N, 114.4°E). The atmospheric temperatures from about 3 to 25 km are calculated from the nitrogen molecule density profiles obtained from the N2 vibrational Raman backscatter, while the atmospheric temperatures between 30 and ∼75 km are calculated by the standard Rayleigh scattering method. The temperatures in the 80–100 km altitude region are derived from the Fe Boltzmann technique. The temperature profiles measured by our lidar systems exhibit good agreement when compared with the radiosonde and satellite data, as well as the model. A Lomb–Scargle spectral analysis of the normalized temperature perturbations in the altitude range from 4 to 60 km shows that the spectral slopes of the vertical wave number spectra tended to −3 for large vertical wave numbers. This is consistent with the model predictions of saturated gravity wave spectra. 相似文献
18.
Adsorption isotherms of various low-biodegradable aromatic compounds on two different activated carbons were determined experimentally and described by FREUNDLICH-type isotherm equations. The equilibrium solid loadings derived from the measurements correlate reasonably well with the adsorbent surface areas and show decreasing values in the order 3-nitro-aniline ～ 4-chloroaniline > 3.5-dinitrobenzoic acid < phenylurea. Kinetic experiments in a differential column batch reactor were conducted in order to evaluate liquid-phase mass transfer and intraparticle diffusion parameters. The homogeneous surface diffusion model could be successfully applied for calculating surface diffusivities and predicting experimental concentration/time profiles. 相似文献
19.
The electron cyclotron waves that originate at low altitudes (<0.5 RE) and observed by ground facilities have been studied in the presence of a weak parallel electric field in auroral magnetoplasma consisting of trapped energetic auroral electrons and cold background electrons of ionospheric origin. The model distribution for auroral trapped electrons is taken as Maxwellian ring distribution. An expression for the growth rate has been obtained in the presence of parallel electric field assuming that the real frequency in the whistler mode is not affected by the presence of the electric field. The results show that waves grow (or damp) in amplitude for a parallel (or antiparallel) electric field. The influence of the electric field is more pronounced at a shorter wavelength spectrum. An increase in population of energetic electrons increases the growth rate and thus, plays a significant role in the wave excitation process in the auroral regions. 相似文献