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1.
Pulses in electron intensity, occurring during the expansion phase of an auroral substorm, were studied using a Skylark sounding rocket launched from Kiruna, Sweden at 2226:50 UT on 2 March 1972. The pulses were typically of 5 s duration and occurred sporadically with a typical interval of 15 s. The rocket carried main and ejected payloads, and the pulses, occurring simultaneously at both, are found to be temporal rather than spatial in origin. Pitch-angle distributions changed little during a pulse, remaining slightly peaked towards larger pitch-angles. Precipitation is thought to be caused by pitch-angle diffusion under conditions where scattering angles are large compared with the opening angle of the loss cone. Enhanced scattering and variations in the temperature of the source plasma are both considered as possible causes of the pulse-like modulation. A dispersion in the times of occurrence of the pulses at different electron energies (3·8, 5·7, 9·0, > 18 and > 48 keV) indicates that the pulses originated at distances which varied between 41,000 ± 4000 km and 90,000 ± 7000 km during the flight. The larger distances are seen as evidence for temporary distortion of the local (L = 5·4) geomagnetic field lines whereby they are stretched to twice their normal (near-dipole) length. It appears that over a period of 100 s the field lines expanded and contracted at a speed of approximately 1000 km s?1. The further observation that the electron energy spectra were approximately Maxwellian, with a temperature equivalent to ～3 keV, helps to confirm the indications that the precipitation and its modulation were controlled directly by processes taking place in the plasma sheet. Other possible causes of the variable dispersion are considered, but found to be inconsistent with the present results. 相似文献
2.
W. Köhnlein 《Planetary and Space Science》1981,29(1):47-56
The electron temperature variations are investigated above Arecibo, Jicamarca, Millstone Hill, St. Santin and a polar area—located at the meridian of Millstone Hill. The data analyzed represent quiet geomagnetic conditions (Kp ≤ 3) during a solar maximum (1967–1970). Between 200 and 600 km the electron temperature data stem from incoherent scatter measurements and above 600 km from the ISIS-1 observations. A simple analytical model which includes Fourier terms and cubic splines (for approximating the height dependence of the coefficients) describes the diurnal and seasonal pattern of the electron temperature in the altitude interval 200–3500 km. Three height regions are particularly striking, i.e. near 200 km where the diurnal variations show a sinusoidal pattern, the altitude interval up to approximately 1000 km which exhibits strong temperature gradients and a complex diurnal and seasonal structure, and the upper region beyond 1000 km which reflects again sinusoidal pattern but with a very pronounced latitudinal dependence. 相似文献
3.
The energy distribution of thermal electrons in the ionospheric plasma was measured by means of a glass-sealed Langmuir probe. Second derivatives of the v-i curves were obtained electrically by using the second harmonic method. The height of the measurement was from 103 to 360 km.Above 130 km the energy distribution of thermal electrons were Maxwellian enough to evaluate electron temperature. Below 130 km the electrons appeared to consist of two groups of electrons of different temperatures. Because of the bi-Maxwellian energy distribution, the apparent electron temperature obtained from the above method differed from that of an electron temperature probe. 相似文献
4.
By means of an inversion of H and K Ca ii line profiles the temperature and electron density in the chromosphere above the umbrae of two sunspots have been estimated. The temperature gradient 5 K km–1 exceeds the corresponding values in both quiet regions and plages. At a height of about 1500 km the umbra becomes hotter than the quiet region. At a temperature of about 10000 K the temperature gradient increases sharply. The electron density at 1500 km is approximately the same as that in the quiet chromosphere at the same height. 相似文献
5.
《Planetary and Space Science》1999,47(10-11):1347-1354
Cosmic ray radiation is the main mechanism for ionizing the lower atmosphere of Titan. Their higher penetration power, in comparison with solar photons, allows cosmic rays to penetrate deep into the atmosphere of Titan, ionizing the neutral molecules and generating an ionosphere with an electron density peak, placed at around 90 km, similar in magnitude to the ionospheric peak produced by solar radiation in the upper atmosphere. In the lower atmosphere, the electron density profile, in the absence of a magnetic field, depends mainly on the modulation of cosmic rays by the solar wind and on the nature of the ionizable particles. We present here the first results of a new numerical model developed to calculate the concentration of electrons and most abundant ions in the Titan lower atmosphere. The present knowledge of Titan’s atmosphere permits us to include new neutral and ionic species, such as oxygen derivates, in a more detailed ion-chemistry calculation than previous lower ionospheric models of Titan. The electron density peaks at 90 km with a magnitude of 2150 cm−3. The ion distribution obtained predicts that cluster cations and hydrocarbon cations are the most abundant ions below and above the electron density peak, respectively. We also discuss the effect of solar activity at the distance of the Saturn orbit on the spectrum of the cosmic particles. We obtain that from solar minimum to solar maximum the ionization rate at the energy deposition peak changes by a factor of 1.2 at 70 km, and by a factor of 2.6 at altitudes as high as 400 km. The electron density at the concentration peak changes by a factor of 1.1 at 90 km, and by a factor of 1.6 at 400 km. 相似文献
6.
The thermal response of the Earth's ionospheric plasma is calculated for various suddenly applied electron and ion heat sources. The time-dependent coupled electron and ion energy equations are solved by a semi-automatic computational scheme that employs Newton's method for coupled vector systems of non-linear parabolic (second order) partial differential equations in one spatial dimension. First, the electron and composite ion energy equations along a geomagnetic field line are solved with respect to a variety of ionospheric heat sources that include: thermal conduction in the daytime ionosphere; heating by electric fields acting perpendicular to the geomagnetic field line; and heating within a stable auroral red are (SAR-arc). The energy equations are then extended to resolve differential temperature profiles, first for two separate ion species (H+, O+) and then for four separate ion species (H+, He+, N+, O+) in addition to the electron temperature. The electron and individual ion temperatures are calculated for conditions within a night-time SAR-arc excited by heat flowing from the magnetosphere into the ionosphere, and also for typical midlatitude daytime ionospheric conditions. It is shown that in the lower ionosphere all ion species have the same temperature; however, in the topside ionosphere above about 400 km, ion species can display differential temperatures depending upon the balance between thermal conduction, heating by collision with electrons, cooling by collisions with the neutrals, and energy transfer by inter-ion collisions. Both the time evolution and steady-state distribution of such ion temperature differentials are discussed.The results show that below 300km both the electrons and ions respond rapidly (<30s) to variations in direct thermal forcing. Above 600 km the electrons and ions display quite different times to reach steady state, depending on the electron density: when the electron density is low the electrons reach steady state temperatures in 30 s, but typically require 700 s when the density is high; the ions, on the other hand, reach steady state in 700 s when the density is high, and 1500–2500 s when the density is low. Between 300 and 600 km, a variety of thermal structures can exist, depending upon the electron density and the type of thermal forcing; however steady state is generally reached in 200–1000 s. 相似文献
7.
The thermal balance of the plasma in the night-time mid-latitude F2-region is examined using solutions of the steady-state O+ and electron heat balance equations. The required concentrations and field-aligned velocities are obtained from a simultaneous solution of the time-dependent O+ continuity and momentum equations.The results demonstrate the systematic trend for the O+ temperature to be 10–20 K greater than the electron temperature during the night at around 300 km, as observed at St. Santin by Bauer and Mazaudier. It is shown that frictional heating between the O+ and neutral gases is the cause of the O+ temperature being greater than the electron temperature; the greater the importance of frictional heating in the thermal balance the greater is the difference in the O+ and electron temperatures. A study is made of the roles played in the thermal balance of the plasma by the thermal conductivity of the O+ and electron gases; collisional heat transfer between O+ electrons and neutrals; frictional heating between the O+ and neutral gases; and advection and convection due to field-aligned O+ and electron motions. The results of the study show that, at around 300 km, electron cooling by excitation of the fine structure of the ground state of atomic oxygen plays a major role in the thermal balance of the electrons and, since the temperature of the ions is little affected by this electron cooling process, in determining the difference between the ion and electron temperatures. 相似文献
8.
We analyzed the spectrum of a coronal condensation observed during the total eclipse of 1983 June 11. Under the assumption of rotational symmetry we found the distributions of the electron density and the temperature. The electron density was higher in the centre of the condensation than on the edge. From different line pairs the maximum electron density was found to be between 1.7 3.5×109cm−3 while the temperature was found to be basically uniform at 1.7 2.7×106K. The turbulence velocity was 15 35km/s. The systematic flow of the condensation region with respect to the quiet corona was not more than 15km/s. Discussion of the instrumental profile showed that its effect was small on lines that were much wider than the profile. 相似文献
9.
Low and mid-latitude lower E-region electron temperature profiles which were obtained by means of an insitu probe were collected. Profiles which are discussed here cover the heights of 90–120 km and measurement reliability at these heights is discussed mainly in terms of electrode contamination and aerodynamical heating.Although measurement errors might exist in some of the electron temperature profiles, it is conclusively described that daytime electron temperature is very often much higher than the possible neutral temperature and Te ≈ Tn is rarely seen. 相似文献
10.
Three ionospheric probes were carried on the ESRO-4 satellite, a spherical gridded probe with swept potential collecting positive ions, a Langmuir probe measuring electron temperature and vehicle potential, and a fixed potential gridded probe measuring fluctuations in total ion density. ESRO-4 was placed in a polar orbit of apogee 1177 km, perigee 245 km on 22 November 1972 and ionospheric data of excellent quality were obtained until the spacecraft's re-entry on 15 April 1974. The instrumentation is described and early results are presented. 相似文献
11.
Measurements of thermospheric electron temperatures at altitudes in the range 250–1100 km, made with a Langmuir probe carried on the polar-orbiting satellite ESRO-4, have been used to derive model functions of electron temperature in terms of altitude, magnetic latitude and local time for the periods November 1972 to June 1973 and March to October 1973. The technique used to compute the coefficients of the model functions is described, and the model electron temperatures are compared with those obtained from similar instruments on the Ariel-1 satellite in 1962 and the ESRO-1A satellite in 1968–1969, and from ground-based observatories. The models reproduce the major features of topside electron distributions viz. mid-day temperatures exceeding midnight temperatures by about 500 K, dawn enhancement leading to peak temperatures greater than mid-day values particularly around 50° magnetic latitude, and temperatures increasing with altitude at all latitudes and with latitude at all altitudes. The daytime mid-latitude temperature is used to complete a series of observations by various techniques over a solar cycle and thereby to confirm the sense and degree of solar cycle control on the thermospheric electron temperature predicted by theoretical considerations. 相似文献
12.
A stationary two-dimensional isothermal flow parallel to the magnetic lines of force is studied in connection with the hydrodynamic support of a spicule. Observed large extension into the corona (～ 6000 km) and high velocities (～ 25 km s-1) can be explained consistently if the effective kinetic temperature within a spicule could be about 104 K in the chromospheric region (z < 2000 km) and increase to about 2.5 × 104 K or more in the coronal region (z > 2000 km). In a special simple case, an analytic solution of equations of motion is obtained and is used for explaining why the pressure in a spicule can be higher than the normal surrounding pressure in upper levels.
Comparison between the effective kinetic temperatures for the spicule support and the empirical electron temperatures shows that they are about the same in lower levels (z < 2000 km) but contributions to the effective kinetic temperature other than the electron temperatures are necessary in higher levels (z > 2000 km). Thus, we postulate the role of acoustic waves that are enhanced by the presence of the magnetic field and are practically undamped in the accelerated flow in a spicule. The coupling between the acoustic waves and the outward expanding motion initiated at the foot of a spicule by the magnetic buoyancy and the solar oscillation is thought to be similar to the mechanism of a geyser in which the bubble formation in an ascending flow is fundamental. The magnetic field strength adequate to provide an appropriate circumstance for the occurrence of a spicule is considered to be about 200 G at the base of the chromosphere. Observational implications are briefly discussed.
相似文献13.
14.
Electron spectra obtained during the flight of Black Brant VB-31 on August 17, 1970 through a stable aurora to a height of 268 km have been analyzed in detail to obtain the pitch angle distributions from 25 to 155° and the electron energy distributions over an energy range of 18 keV to 20 eV through the region of atmospheric interaction down to 97 km. Backscatter ratios for 140° pitch angle range from 0.065 for 18 keV electrons to 0.22 for 1 keV electrons. Backscatter of lower energy electrons decreases with atmospheric depth below 200 km. The effect of the interactions between auroral electrons and the atmosphere is such as to give a peak in electron flux which moves progressively to higher energies with penetration depth. The secondary electron flux increases monotonically with height up to 200 km. The secondary electron spectrum can be approximated by an energy power over small energy ranges but its form is somewhat dependent on height and on the primary electron spectrum. 相似文献
15.
G. D. Parker 《Solar physics》1973,31(1):259-269
The coronal green line intensity is inappropriate for correlation studies of galactic cosmic ray variations. Being a non-monotonic function of coronal temperature, the green line intensity is a good index of neither coronal temperature nor solar wind speed. A more appropriate measure of coronal activity is the intensity of the electron corona. Two-dimensional observations of the K-corona trace changes in coronal morphology during the solar cycle. An index based on four years of K-coronal measurements made in Hawaii shows that activity in the lower corona is not better correlated than sunspot number with long-term modulation. Correlation analysis defines the time lag of modulation much too poorly to permit its use in estimating the size of the heliosphere. 相似文献
16.
William J. Burke Hans J. Braun J.W. Münch Rita C. Sagalyn 《Planetary and Space Science》1979,27(9):1175-1185
The relationship between the simultaneously observed positions of the maximum omnidirectional flux of the quiet-time ring current positive ions (Λφ) and the maximum electron temperature ΛT in the trough is studied in the midnight sector of the topside ionosphere. Λφ maps to the inner edge of the plasma sheet where ring current fluxes change from nearly isotropic to trapped. At altitudes near 2500 km, the electron temperature at trough latitudes were always sharply peaked. Although Λφ varied with the level of geomagnetic activity, (Λφ ? ΛT) did not. These observations support the hypothesis that the quiet-time ring current is the source of elevated electron temperatures found near the plasmapause. Below 1300 km, peaked electron temperature distributions in the trough were not consistent features of the data. It is shown that (Λφ ? ΛT) increased with decreasing altitude. The possible influences of a westward component to the convective electric field and ionospheric refraction of ion cyclotron waves are discussed. 相似文献
17.
Investigation of nonlinear wave modulation of electron-acoustic solitary wave packets in planar as well as nonplanar geometry is carried out for an unmagnetized two temperature plasma composed of cold and hot (featuring q-nonextensive distribution) electrons with stationary ions. It is shown that in such plasma, propagation of EA wave packets is governed by a modified NLSE which accounts for the geometrical effect and the nonextensivity of the hot electron species. It is found that the nature of the modulational instabilities would be significantly modified due to the geometrical effects, density ratio α of the hot-to-cold electrons species as well as their temperature ratio θ. Also, there exists a modulation instability period for the cylindrical and spherical envelope excitations, which does not exist in the one-dimensional case. Furthermore, spherical EA solitary wave packets are more structurally stable to perturbations than the cylindrical ones. The relevance of the current study to EA wave modulation in auroral zone plasma is highlighted. 相似文献
18.
Rocket results are presented on the OI 6300 Å line and on the N2+ 3914 Å band in the dayglow. An altitude range of 78–335 km is covered. Theoretical interpretations are given, using results of simultaneous measurements of electron density and electron temperature. The apparent brightness of the 6300 Å line at the base of the emitting region is found to be 13 kR, of which 5.5 kR are ascribed to excitation through the Schumann-Runge dissociation of O2 by the solar UV radiations, 0.55 kR to the dissociative recombination of O2+ and NO+ ions, and 0.03 kR to the excitation of O by thermal electrons. An additional source of excitation above 280 km is suggested. The deactivation of O(1D) by O2(X3Σg−) is found to be appreciable below 200 km, and its rate coefficient is estimated to be 2 × 10−10 cm3/sec. The apparent brightness of the 3914 Å band at the base of the emitting region is found to be 6.5 kR, decreasing to 3.2 kR at 330 km. Assuming that fluorescent scattering of solar radiation is the mechanism involved the distribution of N2+ ions is calculated. The rate coefficients for the loss of these ions are hence calculated. 相似文献
19.
Gary A. Chapman 《Solar physics》1970,14(2):315-327
Semi-empirical models of solar faculae, cospatial with strong photospheric magnetic fields, have been constructed from continuum observations. The center-to-limb contrast of the various models was computed taking into account their geometrical shape. The adopted model whose horizontal size was taken to be 750 km, indicates that, in field regions, the temperature begins to rise outwards at z -125 km (above 5000 = 1) and that the extrapolated temperature at z -400 km is about 1500 K above that of the undisturbed atmosphere; the electron density is higher by a factor of about 30. 相似文献
20.
The thermal balance of the plasma in the day-time equatorial F region is examined. Steady-state solutions of electron and ion temperatures are obtained, assuming the ions are O+ and H+. The theoretical concentrations of O+ and H+ and the field-aligned velocity were obtained following Moffett and Hanson (1973), while theoretical photoelectron heating rates of the electron gas were taken from Swartz et al. (1975).The results demonstrate the gross features in the electron and ion temperatures as observed at the Jicamarca Observatory and in the ion temperatures observed on the OGO-6 satellite. The rapid increase in electron temperature above 500 km at the magnetic equator is due to heating by photoelectrons created at higher latitudes and travelling up along the field lines. The rapid increase in ion temperature is due to good thermal contact with the electrons rather than the neutrals. It is shown that field-aligned interhemispheric thermal plasma flows appreciably affect these temperatures, and that, with a net plasma flow from the summer hemisphere to the winter hemisphere, the temperatures are higher in the winter hemisphere. These effects are related to the character of the ion temperature minimum observed by OGO-6 near the magnetic equator. 相似文献