Is T_e equal to T_nm at the heights of 100 to 120 km?     

K.I. Oyama  K. Hirao  P.M. Banks  P.R. Williamson 《Planetary and Space Science》1980,28(3):207-211

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 T_e ≈ T_n is rarely seen.  相似文献   

Thermal balance of the mid-latitude F2-region at night     

G.J. Bailey  R.I. Footitt  R.I. Moffett 《Planetary and Space Science》1979,27(8):1063-1073

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   

On determining magnetohydrodynamic shock parameters θ_Bn and M_A     

J.K. Chao  K.C. Hsieh 《Planetary and Space Science》1984,32(5):641-646

In a collisionless plasma, the magnetohydrodynamic shock structure, the associated waves and turbulence depend strongly on the shock parameters θ_Bn and M_A, where θ_Bn is the angle between the upstream magnetic field and the shock normal and M_A is the upstream Alfvén Mach-number. A method is given to determine θ_Bn and M_A and their estimated errors for all types of shocks without knowing the shock normals. The only measured quantities needed to determine θ_Bn and M_A are the plasma density and magnetic field on both sides of the shock. The estimated error of θ_Bn using our method can be obtained in a straightforward manner and is more reliable than that based on the calculated shock normal and the upstream magnetic field. Its simplicity and ability to handle parallel shocks as well as perpendicular and oblique shocks are illustrated by examples. This method should be useful for characterizing the types of shocks from analyzing the copious amount of data on magnetohydrodynamic (MHD) shocks found in space.  相似文献   

Disappearence of equatorial E_s, associated with magnetic field depressions     

B.V.Krishna MurthyK. Sen Gupta 《Planetary and Space Science》1972

The phenomenon of the sudden disappearance of equatorial sporadic E at two stations, namely, Trivandrum and Kodaikanal is studied. It is established that whenever there is a sudden disappearance of E_s, there is a depression in the horizontal magnetic field (H) range. Electron velocities during the presence and absence of sporadic E have been estimated. These results show that the irregularities responsible for sporadic E are present even when the electron velocities are less than the ion thermal velocity.  相似文献   

The 6300 Å O^1D airglow and dissociative recombination     

V.B. Wickwar  L.L. Cogger  H.C. Carlson 《Planetary and Space Science》1974,22(5):709-724

Measurements of night-time 6300 Å airglow intensities at the Arecibo Observatory have been compared with dissociative recombination calculations based on electron densities derived from simultaneous incoherent backscatter measurements. The agreement indicates that the nightglow can be fully accounted for by dissociative recombination. Thecomparisons are examined to determine the importance of quenching, heavy ions, ionization above the F-layer peak, and the temperature parameter of the model atmosphere. Comparable fits between the observed and calculated intensities are found for several available model atmos- pheres (e.g. CIRA, Jacchia). The least-squares fitting process, used to make the comparisons, produces comparable fits over a wide range of combinations of neutral densities and of reaction constants. Yet, the fitting places constraints upon the possible combinations: these constraints indicate that the latest laboratory chemical constants and densities extrapolated to a base altitude are mutually consistent. However, by imposing an additional constraint, an aero- nomically derived preference is given for about one O(^1D) per combination. A preference is also given for the lower base densities of O₂ derived from rockets rather than from models. Altitude profiles for the 6300 Å and 5577 Å emissions are deduced. In the early evening, there are no large discrepancies in the fits that might indicate an effect from elicited states of O₊, vibrational excitation of O₂, or both. The technique of comparing observed and cal- culated 6300 Å intensities has considerable potential as an aeronomical tool for examination of other possible sources of emission and for determination of relative changes in the neutral atmosphere.  相似文献   

Some aspects of mid-latitude spread-E_s, and its relationship with spread-F     

G.G. Bowman 《Planetary and Space Science》1985,33(9):1081-1089

After discussing some examples of mid-latitude spread-E_s this paper presents distributions showing the diurnal, annual and sunspot-cycle variations of this phenomenon. The variations are very similar to those found for mid-latitude spread-F. Also, a superposed-epoch analysis involving an investigation of spread-F occurrence relative to controls consisting of nights of high spread-E_s occurrence showed a relationship of high significance. A similar analysis using spread-F occurrence relative to daytime spread-E_s controls also suggested a relationship between these parameters. The results presented in this paper together with results from previous work suggest strongly that the two phenomena (spread-E_s and spread-F) are produced by the same or similar disturbances. Also it seems likely that the disturbances responsible for spread-F during night hours are also present during daylight hours.  相似文献   

Ground-based observations of O₂ (b¹Σ⁺_g−X³Σ⁻_g) atmospheric bands in high latitude auroras     

K. Henriksen  G.G. Sivjee  C.S. Deehr  H.K. Myrabø 《Planetary and Space Science》1985,33(1):119-125

Analysis of observed spectrograms is based on comparison with synthetic spectra. The O₂(b¹Σ⁺_g?X³Σ^?_g Atm. (1,1) band in high latitude auroras observed from the ground is found to be the strongest in the Δv = 0 sequence. It is enhanced with altitude relative to the N₂ 1P(2, 0)and N⁺₂ M(2,0) bands, but the O₂ Atm. (2, 2) band has an unexpected low intensity. The range of rotational temperatures of the O₂ Atm. bands varies from approx. 200 to above 500 K which indicates that the altitude of the centroid of the emission region varies from about 100 km to the F-region. The highest temperature is found in the midday aurora associated with the magnetospheric cusp. Conspicuous relative variations between the intensities of N₂ and O₂ spectra are documented, but a satisfactory explanation of the variety is not given. Deviations of the observed O₂ Atm. band intensities from the vibrational intensity distribution predicted by Franck-Condor factors indicate that the excitation of the O₂ Atm. bands in aurora is not mainly due to particle impact on O₂, and the contribution due to energy transfer from hot O(¹D) atoms has to be found in future research.  相似文献   

The spatial extent of aurorae in O(5577) and Na₂(4278) emissions     

S.B. MendeR.H. Eather 《Planetary and Space Science》1971

An investigation of the spatial extent of aurorae was undertaken from College, Alaska, by the ground based Lockheed two channel (5577 and 4278 Å) image intensifier TV system and with a multichannel boresighted tilting filter photometer. The measurements indicate that even on clear nights the extinction due to scattering in the 4278 Å is significant unless the measurements are taken at small zenith angles. To confirm the results and to avoid the low altitude scattering problem, measurements were made on a quite arc with the Lockheed 6 channel tilting filter zenith photometer during the NASA CV 990 expedition. These results show that in the cases observed there was no significant difference between the latitude profiles of O(5577) and N₂⁺(4278) emissions.  相似文献   

Concerning the electron temperature discrepancy between in situ and remote probes in the E-region     

R.J. D&#x;Arcy  J. Sayers 《Planetary and Space Science》1974,22(6):961-966

Rocket borne Langmuir probe measurements of electron temperature in the E-region are examined in relation to recent laboratory investigations of surface drift effects which can lead to erroneously high and time-dependent electron temperature measurements. The rocket data is consistent with the laboratory expectations thus supporting the suggested importance of surface effects in rocket measurements and in relation to the E-region discrepancy with simultaneous incoherent radar scatter measurements.  相似文献   

The semiannual variation in the magnetic activity indices A_a and A_p     

C.A. Green 《Planetary and Space Science》1984,32(3):297-305

The technique of Complex Demodulation is used to examine the long-term modulation of the semiannual variation in planetary magnetic activity as characterised by the A_a index for 1868–1980 and the A_p index for 1932–1980. From the phase results, strong support is found for an “equinoctial” mechanism for the semiannual variation. The amplitude shows a quasi 11 -year modulation for most of the period of analysis and a pronounced increase over the years 1938–1966 approximately. Comparison of the long-term modulation of the semiannual variation in activity, with that of the occurrence of stormy days suggests that the semiannual modulation is energy dependent, being more effective with increasing energy.  相似文献   

Millstone Hill Thomson scatter results for 1966 and 1967     

J.V. Evans 《Planetary and Space Science》1973,21(5):763-792

Thomson (incoherent) scatter radar measurements of F-region electron densities and temperatures were made approximately twice per month throughout 1966 and 1967 at Millstone Hill for periods of 24 hr. Owing to the increase in sunspot activity the results display a rich variety of different types of behaviour. Geomagnetically quiet days tended to follow patterns observed near sunspot minimum. Thus in winter there is typically a marked diurnal variation in electron density with a peak near noon and often a smaller secondary maximum between 02 and 04 EST. In summer there is less day-to-night variation and the peak density is encountered near ground sunset. Usually h_maxF2 is higher in summer than winter and the layer thickness is larger also.Some magnetically disturbed days follow a distinct pattern in which N_max and h_max are normal during the first day of the storm until afternoon when they both increase to very high values. There is then a corresponding decrease in electron temperature. During the night the electron temperature often reaches abnormally high values, providing evidence of nocturnal heating. On the following day N_max and h_max are abnormally low.During 1967 instances in which the trough of low electron density moved south to occupy a position over Millstone became frequent. The electron temperature rose to particularly high values on these occasions. These morphological features are discussed in terms of current theoretical ideas. The results are also employed to derive seasonal variations of electron temperature and protonospheric heat flux. It is shown that since 1964 the protonospheric heat flux has been larger in winter than summer and displays a clear sunspot cycle variation.  相似文献   

Production of vibrationally excited N₂ by electron impact     

L Campbell  D.C Cartwright 《Planetary and Space Science》2004,52(9):815-822

Energy transfer from electrons to neutral gases and ions is one of the dominant electron cooling processes in the ionosphere, and the role of vibrationally excited N₂ in this is particularly significant. We report here the results from a new calculation of electron energy transfer rates (Q) for vibrational excitation of N₂, as a function of the electron temperature T_e. The present study was motivated by the development of a new cross-section compilation for vibrational excitation processes in N₂ which supercedes those used in the earlier calculations of the electron energy transfer rates. We show that the energy dependence and magnitude of these cross sections, particularly in the region of the well-known resonance in N₂, significantly affect the calculated values of Q. A detailed comparison between the current and previous calculated electron energy transfer rates is made and coefficients are provided so that these rates for transitions from level 0 to levels 1-10 can be calculated for electron temperatures less than .  相似文献   

Changes in the frequency distribution of f₀E_s and f_bE_s over two solar cycles     

W.J. Baggaley 《Planetary and Space Science》1985,33(4):457-459

The dependence of the occurrence probabilities of ionosonde sporadic-E parameters f₀E_s and f_bE_s on probing frequency is analyzed for wintertime for day and night for two Southern Hemisphere stations. The ionosonde data indicate that significant changes have taken place over the period 1958–1983 suggesting that E_s has become increasingly dense and also less patchy.  相似文献   

Rocket measurements of ULF electric fields and precipitating particles in the aurora     

C. Reeve  U. Fahleson  B. Maehlum  A. Pedersen  P. Rothwell 《Planetary and Space Science》1978,26(9):833-845

The electric component of ULF waves with a characteristic period of 1.5-3 s and an amplitude of tens of $\text{mV}\text{m}$ has been observed with a double probe on a rocket launched from Andöya in Norway into an aurora. The polarization of the waves was right and left handed nearly circular as well as nearly linear during different intervals of the flight. These measurements are compared with ELF and energetic electron measurements on the rocket and ULF measurements on the ground.Possible interpretations involving generation of the ULF waves by proton cyclotron resonance in the magnetotail or by streaming ions or electrons in the magnetosheath are outlined.  相似文献   

The excitation of O₂(b¹Σ_g⁺) in the nightglow     

R.G.H. Greer  E.J. Llewellyn  B.H. Solheim  G. Witt 《Planetary and Space Science》1981,29(4):383-389

It is proposed that the available measurements of the O₂(b¹Σ_g⁺ ?X³Σ_g^?) atmospheric bands both in the nightglow and in the laboratory indicate that the excitation mechanism is a two-step process rather than the direct three body recombination of atomic oxygen. It is shown that such a two-step mechanism can explain observations of the atmospheric bands both in altitude and intensity.  相似文献   

Distortions of the energy distribution of ionospheric thermal electrons near the focus of S_q current vortex     

Koh-Ichiro Oyama  Kunio Hirao 《Planetary and Space Science》1979,27(2):183-192

Energy distributions of the thermal electrons in the ionospheric plasma were measured on 16 January 1974 and 16 September 1976 by two Japanese rockets, K-9M-45 and K-9M-55 respectively near the focus of S_q current vortex. The main effort was to investigate the energy state of the thermal electrons in a localized hot electron layer which occurs at a height of around 105 km in winter.The results obtained on 16 January 1974 showed that the thermal electrons in the hot electron layer had not a pure Maxwell distribution. While on 16 September 1976, the energy distribution of the electrons was found to be almost Maxwellian in the dynamo region as well as the F-region.  相似文献   

Does IMF B_y induce the cusp field-aligned currents?     

F. Primdahl  F. Spangslev 《Planetary and Space Science》1983,31(4):363-367

A well established correlation exists between the IMF B_y and the cusp field-aligned and horizontal currents (Wilhjelm et al., 1978). The northern and southern cusp currents may be parts of one large scale current system (D'Angelo, 1980) flowing mainly at the magnetopause and driven by the z-component of the solar wind electric field. Primdahl and Spangslev (1981) suggested that the large scale current system seems to shield out the IMF B_y from the interior of the magnetosphere. This paper proposes that the currents are induced by the change of sign of B_y at the IMF sector boundary crossings, and argues that the time constant for decay of the currents may well be one week or larger. The percentage errors in inferring the IMF sector polarity from the Godhavn H magnetogram increases with increasing time since the last sector boundary crossing. This is in accordance with a steady decay of the induced currents. Finally experimental tests are proposed to demonstrate the feasability of and possibly distinguish between the mechanisms.  相似文献   

Latitudinal gradients in the electron temperature of the lower F-region at mid- to low latitudes     

G.J. Bailey  R.J. Footitt  R.J. Moffett 《Planetary and Space Science》1981,29(2):171-184

In this paper we present the results of a study of the thermal balance of the lower F-region at mid- to low latitudes. By using a mathematical model with input data based on in situ measurements along AE-C orbits 457, 666 and 677 (26 January, 1974, 14 February, 1974 and 15 February, 1974, respectively) we demonstrate that electron heat conduction along the magnetic field lines has to be included in the model if good agreement between the calculated and observed electron temperatures is to be achieved. This gives support to the suggestion made by Hoegy and Brace (1978), that the discrepancy in the shape of the electron heating and electron cooling rate distributions reported by Brace et al. (1976) resulted mainly from neglecting heat conduction in the electron gas. In addition, our results indicate that the currently used plasma heating and plasma cooling rates and the photoelectron heating rates calculated by Brace et al. (1976) for the orbits used in this study are consistent with the AE-C in situ measurements.  相似文献   

Solar Wind Electron Parameters from Ulysses/URAP Quasi-Thermal Noise Measurements at Solar Maximum     

K. Issautier  M. Moncuquet  S. Hoang 《Solar physics》2004,221(2):351-359

We present the solar wind plasma parameters obtained from the Ulysses spacecraft during its second pole-to-pole fast latitude scan near the 2001 solar maximum. We study the solar wind properties from the electron density and core temperature measurements made by the radio receiver on Ulysses using the method of quasi-thermal noise spectroscopy. We analyze these parameters as functions of heliographic latitude and distance. We present their histograms normalized to 1 AU and find a bimodal distribution for the electron core temperature. The cooler population can be associated with the fast wind flow emanating from coronal holes present at various latitudes. We discuss a slight north/south asymmetry found for the electron density. Finally, we compare the present results to those obtained during the 1996 solar minimum and 1991 solar maximum.  相似文献   

Quenching of O⁺(²D) by electrons in the thermosphere     

Marsha R. Torr  D.G. Torr  P. Richards 《Planetary and Space Science》1980,28(6):581-584

A major loss process for the metastable species, O⁺(²D), in the thermosphere is quenching by electrons .To date no laboratory measurement exists for the rate coefficient of this reaction. Thermospheric models involving this process have thus depended on a theoretically calculated value for the rate coefficient and its variation with electron temperature. Earlier studies of the O⁺(²D) ion based on the Atmosphere Explorer data gathered near solar minimum, could not quantify this process. However, Atmosphere Explorer measurements made during 1978 exhibit electron densities that are significantly enhanced over those occurring in 1974, due to the large increases that have occurred in the solar extreme ultraviolet flux. Under such conditions, for altitudes ? 280 km, the electron quenching process becomes the major loss mechanism for O⁺(²D), and the chemistry of the N⁺₂ ion, from which the O⁺(²D) density is deduced, simplifies to well determined processes. We are thus able to use the in situ satellite measurements made during 1978 to derive the electron quenching rate coefficient. The results confirm the absolute magnitude of the theoretical calculation of the rate coefficient, given by the analytical expression k(T_e) = 7.8 × 10^?8 (T_e/300)^?0.5cm³s^?1. There is an indication of a stronger temperature dependence, but the agreement is within the error of measurement.  相似文献