Relative flow of H⁺ and O⁺ ions in the topside ionosphere at mid-latitudes     

G.I. Bailey  R.J. Moffett  J.A. Murphy 《Planetary and Space Science》1977,25(10):967-972

Theoretical results on the daily variation of O⁺ and H⁺ field-aligned velocities in the topside ionosphere are presented. The results are for an L = 3 magnetic field tube under sunspot minimum conditions at equinox. They come from calculations of time-dependent O⁺ and H⁺ continuity and momentum balance in a magnetic field tube which extends from the lower F2 region to the equatorial plane (Murphy et al., 1976).There are occasions when ion counterstreaming occurs, with the O⁺ velocity upward and H⁺ velocity downward. The conditions causing this counterstreaming are described: the H⁺ layer is descending whilst O⁺ is supplied from below either to increase the O⁺ concentration at fixed heights or to replace O⁺ ions lost by charge exchange with neutral H. It is suggested that the results of observations at Arecibo by Vickrey et al. (1976) of O⁺ and H⁺ concentrations and counterstreaming velocities are significantly affected by $\text{E}\text{×}\text{B}$ drift.  相似文献   

Ion temperature troughs induced by a meridional neutral air wind in the night-time equatorial topside ionosphere     

G.J. Bailey  R.A. Heelis 《Planetary and Space Science》1980,28(9):895-906

A mathematical model has been developed to calculate consistent values for the O⁺ and H⁺ concentrations and field-aligned velocities and for the O⁺, H⁺ and electron temperatures in the night-time equatorial topside ionosphere. Using the results of the model calculations a study is made to establish the ability of F-region neutral air winds to produce observed ion temperature distributions and to investigate the characteristics of ion temperature troughs as functions of altitude, latitude and ionospheric composition. Solar activity conditions that give exospheric neutral gas temperatures 600 K, 800 K and 1000 K are considered.It is shown that the O⁺-H⁺ transition height represents an altitude limit above which ion cooling due to adiabatic expansion of the plasma is extremely small. The neutral atmosphere imposes a lower altitude limit since the neutral atmosphere quenches any ion cooling which field-aligned transport tends to produce. The northern and southern edges of the ion temperature troughs are shown to be restricted to a range of dip latitudes, the limiting dip latitudes being determined by the magnetic field line geometry and by the functional form of the F-region neutral air wind velocity. Both these parameters considerably influence the interaction between the neutral air and the plasma within magnetic flux tubes.  相似文献   

Thermal response properties of the Earth's ionospheric plasma     

R.G. Roble  J.T. Hastings 《Planetary and Space Science》1977,25(3):217-231

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   

Helium ion outflow from the terrestrial ionosphere     

W.J. Raitt  R.W. Schunk  P.M. Banks 《Planetary and Space Science》1978,26(3):255-268

Extensive calculations have been made of the behaviour of He⁺ for situations where ion outflow occurs from the topside ionosphere. For these circumstances, steady state solutions for the He⁺ continuity, momentum and energy equations have been obtained self-consistently, yielding density, velocity and temperature profiles of He⁺ from 200 to 2000 km altitude. To model the high latitude topside ionosphere, a range of background H⁺O⁺ ionospheres was considered with variations in the H⁺ outflow velocity, the presence of a perpendicular electric field and different peak O⁺ densities. In addition, the atmospheric density of neutral helium was chosen to model typical observed winter and summer densities. From our studies we have found that: (a) The outflowing He⁺ has density profiles of similar shape to those of H⁺, for basically different reasons; (b) The effect of the perpendicular electric field differs considerably for H⁺ and He⁺. This difference stems from the fact that an electric field acts to alter significantly the O⁺ density at high altitudes and this, in turn, changes the H⁺ escape flux through the O⁺+H charge exchange reaction. A similar situation does not occur for He⁺ and therefore the He⁺ escape flux exhibits a negligibly small change with electric field; (c) The fractional heating of He⁺ due to the He⁺O⁺ relative flow is not as effective in heating He⁺ as the H⁺O⁺ relative flow is in heating H⁺; (d) During magnetospheric disturbances when the N₂ density at the altitude of the He⁺ peak (600 km) can increase by a factor as large as 50, the He⁺ peak density decreases only by approximately a factor of 2; and (e) The He⁺ escape flux over the winter pole is approximately a factor of 20 greater than the He⁺ escape flux over the summer pole. Consequently, on high latitude closed field lines there could be an interhemispheric He⁺ flux from winter to summer.  相似文献   

Effect of diffusion-thermal processes on the high-latitude topside ionosphere     

R.W. Schunk  W.J. Raitt  A.F. Nagy 《Planetary and Space Science》1978,26(2):189-191

We have studied the extent to which diffusion-thermal heat flow affects H⁺ temperatures in the high-latitude topside ionosphere. Such a heat flow occurs whenever there are H⁺?O⁺ relative drifts. From our study we have found that at high-latitudes, where H⁺ flows up and out of the topside ionosphere, diffusion-thermal heat flow acts to reduce H⁺ temperatures by 500–600 K at altitudes above about 900 km.  相似文献   

The topside ionosphere above Arecibo at equinox during sunspot maximum     

G.J. Bailey 《Planetary and Space Science》1980,28(1):47-59

The coupled time-dependent O⁺ and H⁺ continuity and momentum equations and O⁺, H⁺ and electron heat balance equations are solved simultaneously within the L = 1.4 (Arecibo) magnetic flux tube between an altitude of 120 km and the equatorial plane. The results of the calculations are used in a study of the topside ionosphere above Arecibo at equinox during sunspot maximum. Magnetically quiet conditions are assumed.The results of the calculations show that the L = 1.4 magnetic flux tube becomes saturated from an arbitrary state within 2–3 days. During the day the ion content of the magnetic flux tube consists mainly of O⁺ whereas O⁺ and H⁺ are both important during the night. There is an altitude region in the topside ionosphere during the day where ion-counterstreaming occurs with H⁺ flowing downward and O⁺ flowing upward. The conditions causing this ion-counterstreaming are discussed. There is a net chemical gain of H⁺ at the higher altitudes. This H⁺ diffuses both upwards and downwards whilst O⁺ diffuses upwards from its solar e.u.v. production source which is most important at the lower altitudes. During the night the calculated O⁺ and H⁺ temperatures are very nearly equal whereas during the day there are occasions when the H⁺ temperature exceeds the O⁺ temperature by about 300 K.  相似文献   

Regions of He⁺ dominance in the high-latitude topside ionosphere     

S. Quegan  G.J. Bailey  R.J. Moffett 《Planetary and Space Science》1984,32(7):791-802

Observations of the occurrence of He⁺ dominance in the topside ionosphere are discussed. An earlier model of the behaviour of high-latitude H⁺ and O⁺ thermal plasma (Quegan et al., 1982) is extended to include He⁺ as a major ion. Calculations using the extended model show that plasma convection is likely to play a key rôle in producing regions of He⁺ dominance. Suggested conditions for He⁺ dominance are listed and their applicability to observed He⁺ behaviour is discussed.  相似文献   

Thermal ion flows in the topside auroral ionosphere and the effects of low-altitude,transverse acceleration     

M. Lockwood 《Planetary and Space Science》1982,30(6):595-609

Topside ionospheric profiles are used to study the upward field-aligned flow of thermal O⁺ at high latitudes. On the majority of the field lines outside the plasmasphere, the mean flux is approximately equal to the mean polar wind measured by spacecraft at greater altitudes. This is consistent with the theory of thermal light ion escape supported, via charge exchange, by upward O⁺ flow at lower heights. Events of larger O⁺ flow are detected at auroral latitudes and their occurrence is found to agree with that of transversely accelerated ions within the topside ionosphere and the magnetosphere. The effects of low altitude heating of O⁺ by oxygen cyclotron waves, driven by downward field-aligned currents, are considered as a possible common cause of these two types of event.  相似文献   

Diffusion coefficients for three major ions in the topside ionosphere     

S. Quegan  G.J. Bailey  R.J. Moffett 《Planetary and Space Science》1981,29(8):851-867

Published experimental data on ion composition in the topside ionosphere are examined. For certain features (the light ion trough, the high-latitude trough, the high-latitude hole and the mid-latitude total ion concentration trough) it is pointed out that the number of major ions present may be 3 or more. Transport equations derived by Schunk and co-workers are extended to include the case of three major ions in the topside ionosphere. Specific calculations are made for the O⁺, H⁺ and He⁺ ions and the behaviour of the diffusion coefficients is discussed. From a model of the high-latitude ionization hole, described by Heelis et al., representative concentration and temperature profiles are obtained. These profiles are used to demonstrate further the behaviour of the ion diffusion coefficients.  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   

The transient response of the topside ionosphere to precipitation   总被引：1，自引：0，他引：1  

J.H. Whitteker 《Planetary and Space Science》1977,25(8):773-786

A numerical time-dependent model of the topside and F-layer ionosphere is used to describe how the density of O⁺ ions and the plasma temperatures change as a result of transient electron precipitation with a soft energy spectrum (ca. 100 eV per electron). The response time for electron gas heating is about 2 min; for changes in topside scale height it is from 5 to 15 min, depending on altitude; and for changes in F-layer peak density, it is more than an hour. The low-density topside ion gas is thermally isolated on a short time scale; consequently the ion temperature responds almost adiabatically to volume changes. A transient precipitation event (of, say, 10 min duration) initiates a disturbance that propagates upward at approximately the sonic upeed in the plasma (ca. 2km/s), growing in amplitude with height. Such an event has little effect on the density at the peak of the F layer. An element of ionosphere that drifts horizontally in an antisunward direction through the magnetospheric cleft and into the polar cap recieves some ionization from the cleft, but not enough to be decisive in its survival. The collapse of the topside when heating is removed increases temporarily the density of the F layer.  相似文献   

A model of the terrestrial ionosphere in the altitude interval 50–4000 km I. Atomic ions (H+, He+, N+, O+)     

W. Köhnlein 《Earth, Moon, and Planets》1989,45(1):53-100

An empirical model of atomic ion densities (H⁺, He⁺, N⁺, O⁺) is presented up to 4000 km altitude as a function of time (diurnal, annual), space (position, altitude) and solar flux (F10.7) — using observations of satellites (AE-B, AE-C, AE-D, AE-E, ISIS-2, OGO-6) and rockets during quiet geophysical conditions (K _p 3). The numerical treatment is based upon harmonic functions for the horizontal pattern and cubic splines for the vertical structure.The ion densities increase with increasing height up to a maximum (depending roughly on the ion mass) and decrease beyond that with increasing altitude. Above 200 km, O⁺ is the main ionic constituent being replaced at approximately 800 km (depending on latitude, local time, etc.) by H⁺. Around polar regions the light ions, H⁺ and He⁺, are depleted (polar wind) and the heavier ones enhanced. During local summer conditions the ion densities increase around polar latitudes and correspondingly decrease during local winter, except He⁺ which reflects the opposite pattern. Diurnal variations are intrinsically coupled to the individual plasma layers: N⁺ and O⁺ peak, in general, during daytime, while the amplitudes and phases of H⁺ and He⁺ change strongly with altitude and latitude. Earth, Moon and Planets Review article.  相似文献   

Ion transition heights from topside electron density profiles     

J.E. Titheridge 《Planetary and Space Science》1976,24(3):229-245

Theoretical electron density profiles are calculated for the topside ionosphere to determine the major factors controlling the profile shape. Only the mean temperature, the vertical temperature gradient and the $\text{O}{}^{\mathrm{+}}\text{H}{}^{\mathrm{+}}$ ion transition height are important. Vertical proton fluxes alter the ion transition height but have no other effect on the profile shape. Diffusive equilibrium profiles including only these three effects fit observed profiles, at all latitudes, to within experimental accuracy.Values of plasma temperature, temperature gradient and ion transition height h_tT were determined by fitting theoretical models to 60,000 experimental profiles obtained from Alouette l ionograms, at latitudes of 75°S–85°N near solar minimum. Inside the plasmasphere h_T varies from about 500 km on winter nights to 850 km on summer days. Diurnal variations are caused primarily by the production and loss of O⁺ in the ionosphere. The approximately constant winter night value of h_T is close to the level for chemical equilibrium. In summer h_T is always above the equilibrium level, giving a continual production of protons which travel along lines of force to aid in maintaining the conjugate winter night ionosphere. Outside the plasmasphere h_T is 300–600 km above the equilibrium level at all times. This implies a continual near-limiting upwards flux of protons which persists down to latitudes of about 60° at night and 50° during the day.  相似文献   

Deuterium on Venus: Model comparisons with pioneer Venus observations of the predawn bulge ionosphere     

Shailendra Kumar  Harry A. Taylor 《Icarus》1985,62(3):494-504

A model of the predawn bulge ionosphere composition and structure is constructed and compared with the ion mass spectrometer measurements from the Pioneer Venus Orbiter during orbits 117 and 120. Particular emphasis is given to the identification of the mass-2 ion which we find unequivocally due to D⁺ (and not H₂⁺). The atmospheric D/H ratio of 1.4% and 2.5% is obtained at the homopause (～ 130 km) for the two orbits. The H₂⁺ contribution to the mass-2 ion density is less than 10%, and the H₂ mixing ratio must be <0.1 ppm at 130 km altitude. The He⁺ data require a downward He⁺ flux of ～2 × 10⁷ cm^?2 sec^?1 in the predawn region which suggest that the light ions also flow across the terminator from day to night along with the observed O⁺ ion flow.  相似文献   

Effects of photoelectron heating and interhemisphere transport on day-time plasma temperatures at low latitudes     

G.J. Bailey  R.J. Moffett  W.E. Swartz 《Planetary and Space Science》1975,23(4):599-610

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   

Coincident observations of ionospheric troughs and the equatorial plasmapause     

J.M. Grebowsky  N.C. Maynard  Y.K. Tulunay  L.J. Lanzerotti 《Planetary and Space Science》1976,24(12):1177-1185

Explorer 45 traversed the plasmapause (determined approximately via the saturation of the d.c. electric field experiment) at near-equatorial latitudes on field lines which were crossed by Ariel 4 (~600km altitude) near dusk in May 1972 and on field lines which were crossed by Isis II (~1400km altitude) near midnight in December 1971 and January 1972. Many examples were found in which the field line through the near-equatorial plasmapause was traversed by Explorer 45 within one hour local time and one hour universal time of Ariel and Isis crossings of the same L coordinate. For the coincident passes near dusk, the RF electron density probe on Ariel detected electron density depletions near the plasmapause L coordinates when Ariel was in darkness. When the Ariel passes were in sunlight, however, electron depletions were not discernable near the plasmapause field line. On the selected near-midnight passes of Isis II, electron density depressions were typically detected (via the topside sounder) near the plasmapause L coordinate. The dusk Ariel electron density profiles are observed to reflect O⁺ density variations. Even at the high altitude of Isis near midnight, O⁺ is found to be the dominant ion in the trough region whereas H⁺ is dominant at lower latitudes as is evident from the measured electron density scale heights. In neither local time sector was it possible to single out a distinctive topside ionosphere feature as an indicator of the plasmapause field line as identified near the equator. At both local times the equator-determined plasmapause L coordinate showed a tendency to lay equatorward of the trough minimum.  相似文献   

The calculated and observed diurnal variation of the ionosphere over Millstone Hill on 23–24 March 1970     

R.G. Roble 《Planetary and Space Science》1975,23(7):1017-1033

A numerical model of current F-region theory is use to calculate the diurnal variation of the mid-latitude ionospheric F-region over Millstone Hill on 23–24 March 1970, during quiet geomagnetic conditions. From the solar EUV flux, the model calculates at each altitude and time step primary photoelectron spectra and ionization rates of various ion species. The photoelectron transport equation is solved for the secondary ionization rates, photoelectron spectra, and various airglow excitation rates. Five ion continuity equations that include the effects of transport by diffusion, magnetospheric-ionospheric plasma transport, electric fields, and neutral winds are solved for the ion composition and electron density. The electron and ion temperatures are also calculated using the heating rates determined from chemical reactions, photoelectron collisions, and magnetospheric-ionospheric energy transport. The calculations are performed for a diurnal cycle considering a stationary field tube co-rotating with the Earth; only the vertical plasma drift caused by electric fields perpendicular to the geomagnetic field line is allowed but not the horizontal drift. The boundary conditions used in the model are determined from the incoherent scatter radar measurements of T_e, T_i and O⁺ flux at 800km over Millstone Hill (Evans, 1971a). The component of the neutral thermospheric winds along the geomagnetic field has an important influence on the overall ionospheric structure. It is determined from a separate dynamic model of the neutral thermosphere, using incoherent scatter radar measurements.The calculated diurnal variation of the ionospheric structure agrees well with the values measured by the incoherent scatter radar when certain restrictions are placed on the solar EUV flux and model neutral atmospheric compositions. Namely, the solar EUV fluxes of Hinteregger (1970) are doubled and an atomic oxygen concentration of at least $\text{10}{}^{11}\text{cm}{}^3$ at 120 km is required for the neutral model atmosphere. Calculations also show that the topside thermal structure of the ionosphere is primarily maintained by a flow of heat from the magnetosphere and the night-time F2-region is maintained in part by neutral winds, diffusion, electric fields, and plasma flow from the magnetosphere. The problem of maintaining the calculated night-time ionosphere at the observed values is also discussed.  相似文献   

On the origin of the hot ions in the disturbed dayside magnetosphere     

Bengt Hultqvist 《Planetary and Space Science》1983,31(2):173-184

On the basis of observations in the dayside magnetosphere of the O⁺ and H⁺ ion densities as function of radial distance under fairly undisturbed and under storm conditions it is argued that acceleration of the hot magnetospheric ions of ionospheric origin cannot be limited to the outer parts of the field tubes. The extraction process seems to work below 1000 km altitude in storm conditions and to have a fairly small extension in altitude. The acceleration mechanism(s) do(es) not affect only one ion species. Variation in the altitude of the extraction of ionospheric ions is the most likely reason for the observed variations in the n(O⁺)/n(H⁺) ratio. Extraction of ionospheric ions into the magnetosphere does not seem to be a main cause of the storm time density decrease of the ionosphere.  相似文献   

Thermal proton flow in the plasmasphere: The morning sector     

Peter M. Banks  Joe R. Doupnik 《Planetary and Space Science》1974,22(1):79-94

Vertical profiles of electron density obtained in the vicinity of the plasmapause using the Alouette-II topside sounder have been analyzed to assess the presence of H⁺ flow in the topside ionosphere. The observations in the midnight sector show clearly the presence of the plasmapause; i.e. there is a sharp boundary separating the poleward regions of polar wind H⁺ flow and the more gentle conditions of the plasmasphere where light ions are present in abundance. In contrast, in the sunlit morning sector upwards H⁺ flow is deduced to be present to invariant latitudes as low as 48° (L = 2·2) in the regions normally known to be well inside the plasmasphere. The upwards H⁺ flux is sufficiently large (3 × 10⁸ ions cm^?2 sec^?1) that the plasmapause cannot be seen in the latitudinal electron density contours of the topside ionosphere. The cause for this flow remains unknown but it may be a result of a diurnal refilling process.  相似文献   

A comparison of the temperature and density structure in high and low speed thermal proton flows     

W.J. Raitt  R.W. Schunk  P.M. Banks 《Planetary and Space Science》1975,23(7):1103-1117

The continuity, momentum and energy hydrodynamic equations for an H⁺-O⁺ topside ionosphere have been solved self-consistently for steady state conditions similar to those found outside the plasmasphere. Results are given for undisturbed and trough conditions with a range of H⁺ outflow velocities yielding subsonic and supersonic flow. In the formulation of the equations, account was taken of the velocity dependence of ion-neutral, ion-ion and ion-electron collision frequencies. In addition, parallel stress and the nonlinear acceleration term were retained in the H⁺ momentum equation. Results computed from this model show that, as a result of Joule (frictional) heating, the H⁺ temperature rises with increasing outflow velocity in the subsonic flow regime, reaching a maximum value of about 4000 K. For supersonic flow other terms in the H⁺ momentum equation become important and alter the H⁺ velocity profile such that convection becomes a heat sink in the 1000–1500 km altitude range. This, together with the reduced Joule heating resulting from the high-speed velocity dependence of the H⁺ collision frequencies, results in a decrease in the H⁺ temperature as the outflow velocity increases. However, for all outward flows the H⁺ temperature remains substantially greater than the O⁺ temperature. With identical upper boundary velocities, the H⁺ flow velocity is higher at low altitudes for trough conditions compared with non-trough conditions, but the H⁺ temperature in the trough is lower. The form of the H⁺ density profiles for supersonic flow does not in general differ greatly from those obtained with wholly subsonic flow conditions.  相似文献