A study of F2 region night-time vertical ionization fluxes at millstone hill     

J. V. Evans 《Planetary and Space Science》1975,23(12):1611-1619

Vertical fluxes of ionization in the F2 region have been measured by the incoherent scatter technique over Millstone Hill in 1969. The results obtained near midnight for the region above h_maxF2 have been examined to determine whether there is a significant flux of ionization from the magnetosphere to the ionosphere that serves to maintain the F-layer. It is found that H⁺ ions are a minor constituent over the altitude range in which useful measurements can be made, so that any conclusion must rest upon properly interpreting the observed O⁺ fluxes. By selecting periods when the layer did not appear to be decaying rapidly it was hoped to find cases where the O⁺ flux did not vary with altitude in the range 500 h 800 km (i.e. where losses are unimportant), since this would imply that the flux is of magnetospheric origin.

While three cases exhibited this behaviour, the majority exhibited a decrease in the O⁺ flux with height, indicating that the layer was descending. Attempts to correct for this were made, and the average flux from the magnetosphere was estimated as 3 × 10⁷ el/cm²/sec. This is in fair agreement with other recent estimates, and implies that at this latitude the ionosphere is not maintained solely by the magnetospheric flux. Moreover, large increases in flux that could give rise to nocturnal increases in the total content of the layer do not appear to have been seen.  相似文献   

A theoretical study of the time-dependent behaviour of O in the mid-latitude plasmasphere     

J. A. Murphy  A. A. Naghmoosh 《Planetary and Space Science》1984,32(12):1591-1603

The behaviour of O²⁺ at L = 3 in the plasmasphere is studied. Starting with a low O²⁺ flux-tube content to characterize post-magnetic-storm conditions the time-dependent equations of continuity and momentum for O²⁺ are solved to give densities and fluxes for a period of several days using both sunspotmaximum and sunspot-minimum parameters. Our results show large amounts of O²⁺ near the equator at sunspot maximum but relatively little at sunspot minimum, and emphasize the key role of the collisional process between O²⁺ and O⁺. It is the combined effects of O²⁺---O ⁺ collisions and thermal diffusion that lead to the large O²⁺ densities near the equator at sunspot maximum. Both of these mechanisms have less influence at sunspot minimum. At sunspot maximum the O⁺ layer acts as a collisional barrier below the O²⁺ production region preventing O²⁺ from sinking towards regions of high recombination rate. In this production region the effects of thermal diffusion are small and upward flow of O²⁺ results from the action of the O²⁺ pressure gradient and the polarization electric field. When the upward flowing O²⁺ reaches regions in which thermal diffusion has a strong influence it is accelerated to even higher altitudes. The O ⁺ barrier is so effective that the diurnal variation of the O⁺ layer is reflected in the diurnal variation of O²⁺ near the equator at sunspot maximum. Our sunspot maximum results also indicate that certain types of temperature profiles are more likely to enhance equatorial O²⁺ densities. The existence of large temperature gradients below 1000 km altitude does not help the flow of O²⁺ towards the equator. The associated changes in the O⁺ layer lead to more O²⁺-O ⁺collisions and a smaller O²⁺ thermal-diffusion coefficient, the latter being sensitive to the ratio n(H⁺)/n(O⁺).  相似文献   

A modelling study of satellite beacon measurements of protonospheric replenishment     

E. M. Poulter  J. K. Hargreaves  G. J. Bailey  R. J. Moffett 《Planetary and Space Science》1981,29(12):1281-1286

Recent satellite beacon derived measurements of the recovery of protonospheric ionization following periods of increased geomagnetic activity show that the recovery takes longer than is indicated by whistler measurements. Realistic plasmasphere models have been used to determine whether satellite beacon measurements are reliable indicators of this recovery. It is found that the recovery time of the protonospheric content is similar to that of the minimum L-value flux tube intersected by the slant raypaths. Satellite beacon results are therefore useful indicators of protonospheric recovery after a storm provided any unrepresentative diurnal variations are eliminated.  相似文献   

Chemistry of the nightside ionosphere of Venus     

J. L. Fox 《Planetary and Space Science》1992,40(12):1663-1681

We have constructed a one-dimensional model of the nightside ionosphere of Venus in which it is assumed that the ionization is maintained by day-to-night transport of atomic ions. Downward fluxes of O⁺, C⁺ and N⁺ in the ratios measured on the dayside at high altitudes are imposed at the upper boundary of the model (about 235 km). We discuss the resulting sources and sinks of the molecular ions NO⁺,CO⁺,N₂⁺,CO₂⁺ and O₂⁺. As the O⁺ flux is increased, the peak density of O⁺ increases proportionally and the altitude of the peak decreases. The O₂⁺ peak density is approximately proportional to the square root of the O⁺ flux and the peak rises as the O⁺ flux increases. NO⁺ densities near the peak are relatively unaffected by changes in the O⁺ flux. If the ionosphere is maintained mostly by transport, the ratio of the peak densities of O⁺ and O₂⁺ indicates the downward flux ofO⁺, independent of the absolute magnitudes of the densities. The densities of mass-28 ions are, however, still considered to be the most sensitive indicator of the importance of electron precipitation. We examine here the inbound and outbound portions of six early nightside orbits with low periapsis and use data from the Pioneer Venus orbiter ion mass spectrometer, the retarding potential analyzer and the electron temperature probe to determine the relative importance of ion transport and electron precipitation. For most of the orbits, precipitation is inferred to be of low to moderate importance. Only for orbit 65, which was the first nightside orbit published by Taylor et al. [J. geophys. Res. 85, 7765 (1980)] and for the inbound portion of orbit 73 does the ionization structure appear to be greatly affected by electron precipitation.  相似文献   

Hydrogen atoms and ions in the thermosphere and exosphere     

D. R. Bates  T. N. L. Patterson 《Planetary and Space Science》1961,5(4):257-273

The distribution of atomic hydrogen in the thermosphere and exosphere is computed taking into account the upward flow which balances the escape flux. Because of the upward flow the number-density gradient is much steeper than it would be in a static atmosphere. Attention is drawn to the fact that the ratio of the amount of hydrogen above the 100 or 110km levels to the amount of hydrogen above the 200 or 300 km levels is a sensitive measure of the temperature of the exosphere. The evidence on the absolute abundance of atomic hydrogen is examined. It is concluded that the number density at the 120km level is probably about 5 × 10⁵/cm³. The Ly. absorption line at this level is beyond the linear part of the curve of growth.

Consideration is also given to the steady-state distributions of O⁺ and H⁺ ions. In the lower part of the exosphere the number density of O⁺ ions falls with increase in altitude (the associated scale height being twice that of the O atoms) and the number density of H⁺ ions rises at the same rate (as was first pointed out by Dungey). The altitude at which the number densities of O⁺ and H⁺ ions become equal is calculated on various assumptions regarding the temperature and hydrogen content of the exosphere. It is found to be about 1200 km when the temperature is 1250° K and the hydrogen content corresponds to the number density cited near the end of the preceding paragraph. The gradient of the predicted electrondensity distribution at several Earth radii is much less than that deduced from whistler studies.

The passage from charge transfer to diffusive equilibrium is discussed in an Appendix.  相似文献   

Ionospheric scale height from the refraction of satellite signals     

M. L. Heron  J. E. Titheridge 《Planetary and Space Science》1972,20(12):2015-2028

Accurate observations of the elevation angle of arrival of 20 MHz signals from the polar orbiting satellite Beacon-B for a 20 month period have provided transmission ionograms which may be reduced to give H_p, the scale height at the peak of the ionosphere. Noon seasonal averages of H_p are 1.35 (in winter) to 1.55 (in summer) times greater than the scale height obtained from bottom-side ionograms. A comparison of scale height at the peak with routine measurements of total content and peak electron density indicates that the O⁺/H⁺ transition level is above 1000 km during the day but comes down to about 630 km on winter nights. A predawn peak in the overall scale height (∝ total content/peak density) is caused by a lowering of the layer to a region of increased recombination and is magnified in winter by low O⁺/H⁺ transition levels. After sunrise in winter and equinoxes the overall scale height is less than the scale height at the peak, implying an outwards flux of ionisation which lasts for about three hours. The summer evening increase in ƒ₀F2 requires both a cooling and a raising of the layer for its occurrence.  相似文献   

Helium ions in the mid-latitude plasmasphere     

J.A. Murphy  G.J. Bailey  R.J. Moffett 《Planetary and Space Science》1979,27(12):1441-1449

An initial study of the behaviour of He⁺ ions in the mid-latitude plasmasphere is carried out by solving the time-dependent equations of continuity and momentum. Starting with a low He⁺ tube content, results are obtained for a period of 8 days. In the topside ionosphere there is an upflow of He⁺ during the day and downflow at night, for the sunspot maximum conditions considered. The downflow at night differs from the behaviour of H⁺ for these atmospheric conditions. However, little of the He⁺ produced in the daytime is lost by recombination at night; it is suggested that the supply of He⁺ to the mid-latitude plasmasphere is, in effect, an escape process for neutral helium.  相似文献   

Effects of greatly increased O loss in the ionospheric F-region     

R. J. Moffett  G. J. Bailey  B. Jenkins 《Planetary and Space Science》1992,40(12):1631-1637

A model of the ionosphere and plasmasphere is used to study some of the signatures of an idealized SAID (subauroral ion drift) event in the nightside ionosphere. A closed subauroral tube of plasma is considered under solar maximum atmospheric conditions and the westward velocity of 3 km s⁻¹ persists for 30 min. By pursuing, in turn, calculations in which plasma diffusion is suppressed and in which chemical loss of O⁺ is suppressed, the signatures of O⁺ chemistry alone and of field-aligned diffusion alone during the SAID event can be elucidated. Both chemical loss and transport contribute to the decay of the F-layer. Results from full calculations (including both chemistry and transport) demonstrate strong chemical-transport interaction.  相似文献   

Electron content modelling: The significance of protonospheric contents     

E.M. Poulter  J.K. Hargreaves  G.J. Bailey  R.J. Moffet 《Planetary and Space Science》1981,29(8):869-883

The principal advance of the ATS-6 satellite beacon experiment was the ability to deduce continuously the electron content along the entire slant path from ground-based measurements of the signal group delay. This feature has been exploited in conjunction with the more usual Faraday rotation technique to separate the total electron content into ionospheric and protonospheric components. The physical validity of the deduced quantities is investigated using a mathematical model of the plasmasphere in which integration of the time-dependent continuity and momentum equations for oxygen and hydrogen ions along selected L shells yields the ion concentrations and field-aligned fluxes. The ion concentrations are then integrated along the propagation path to various ground stations from ATS-6 to give computed values for comparison with observations. The mathematical model is used with different sets of atmospheric parameters to investigate the significance of ionospheric and protonospheric contents as derived from beacon data.The calculated electron concentrations are able to reproduce mid-latitude equinoctial electron content observations. The shape parameters τ and F can also be simulated by day, but night-time values do not match the observations well, a greater protonospheric content being required. The calculations show that the quantity N_p, which is readily derived from ATS-6 observations, may be interpreted as the slant H⁺ content above some fixed height in the case of some stations (but not others) if the plasmasphere is reasonably full. The total slant content of H⁺ is approx. twice the value of N_p, though it appears that for the Lancaster raypath a closer relationship exists between N_p and the H⁺ tube content at L = 1.8. In general,N_p is most closely related to the tube content for an L value slightly greater than the minimum L intersected along the raypath.  相似文献   

An auroral F-region study using in situ measurements by the Atmosphere Explorer-C satellite     

Marsha R. Torr  D. G. Torr   《Planetary and Space Science》1975,23(12):1669-1679

On 14 July 1974 the Atmosphere Explorer-C satellite flew through an aurora at F-region altitudes just after local midnight. The effects of the particle influx are clearly evident in the ion densities, the 6300 Å airglow, and the electron and ion temperatures. This event provided an opportunity to study the agreement between the observed ion densities and those calculated from photochemical theory using in situ measurements of such atmospheric parameters as the neutral densities and the differential electron energy spectra obtained along the satellite track. Good agreement is obtained for the ions O₂⁺, NO⁺ and N₂⁺ using photochemical theory and measured rate constants and electron impact cross sections. Atomic nitrogen densities are calculated from the observed [NO⁺]/[O₂⁺] ratio. In the region of most intense electron fluxes (20 erg cm⁻² sec⁻¹) at 280 km, the N density is found to be between 2 and 7 × 10⁷ cm⁻³. The resulting N densities are found to account for approx. 60% of the production of N⁺ through electron impact on N and the resonant charge exchange of O⁺(²P) with N(⁴S). This reaction also provides a significant source of O(¹S) in the aurora at F-region altitudes. In the region of intense fast electron influx, the reaction with atomic nitrogen is found to be the main loss of O⁺(²P).  相似文献   

Ionospheric conditions     

Marcel Nicolet  William Swider  Jr. 《Planetary and Space Science》1963,11(12):1459-1482

A general analysis of ionospheric conditions has been made in the light of possible ionic reactions occurring in the upper atmosphere. Data obtained on various parameters, such as ionic production and recombination, show that precise knowledge of the spectral distribution of solar radiation is needed and that other experimental determinations on dissociative recombinations are required.

The ionic complexity of the ionosphere is underlined by describing how the atomic ions O⁺ and N⁺ react with N₂, O₂ and NO molecules. The behavior of the molecular ions N⁺₂, O⁺₂and NO⁺depends on a group of simultaneous processes involving charge transfers and ionatom interchanges which are more important than dissociative recombinations. The altitude distribution of ions is exemplified by discussing the relative importance of various loss coefficients in the D-, E- and F-regions. It is seen that molecular nitrogen ions are subject to important charge transfer processes, that nitric oxide ions are always final products destroyed only by dissociative recombination. Additionally, the entire production of atomic oxygen ions is related to the photoionization of molecular nitrogen. Some information is also given on possible anomalies in the ratio of O⁺₂ and NO⁺ densities in the lower ionosphere. From the lack of sufficient experimental information on ionic processes it is shown that a precise analysis of ionospheric behavior remains highly speculative.  相似文献   

Twilight effects of solar ionizing radiation     

A. Dalgarno

Michael B. McElroy 《Planetary and Space Science》1966,14(12):1321-1329

The absorption of solar ionizing radiation during twilight is investigated. Ion production rates are obtained as a function of altitude and twilight intensities and altitude profiles of emissions arising from the fluorescence of solar ionizing radiation are calculated for various solar depression angles. For an atmosphere with an exospheric temperature of 750°K, the predicted overhead intensity from fluorescence of the O⁺(²P — ²D) lines at 7319–7330 diminishes from 175 R at dusk to 10 R at a solar depression angle of 10°. The predicted overhead intensities from fluorescence of the N₂⁺ Meinel and first negative systems are respectively about 175 R and 20 R at dusk diminishing to respectively 1.5 R and 0.1 R at a solar depression angle of 10°.

It is suggested that a charge transfer reaction of O⁺²D in N₂ is a significant source of N₂⁺ ions. This reaction offers a possible explanation for the high apparent rotational temperatures in the first negative system observed by Broadfoot and Hunten. Other excitation and ionization mechanisms are briefly discussed.  相似文献   

N₂ emission in the twilight     

A. L. Broadfoot  D. M. Hunten 《Planetary and Space Science》1966,14(12):1303-1319

About a year's observations of the N₂⁺ band (3914 Å) at Kitt Peak (latitude 32°) are reported. Morning intensities are the same throughout the year, but there is a strong winter maximum in the evening. It is suggested that the additional ionization is produced by photoelectrons from the magnetic conjugate point. Heights are estimated by the zenith-horizon method, which gives 235 km for the constant component and 350 km during the evening enhancement. The intensity variation through twilight is therefore entirely due to changes of the N₂⁺ concentration; each ion scatters light at a constant rate. The rotational distribution resembles that for a temperature of 1600°K, much higher than the temperature of the atmosphere. It is suggested that part of the ions may be produced by charge transfer from metastable O⁺(²D). N₂⁺ concentrations resulting from photoionization are calculated; they give a fair account of the observed horizon intensities, but not the zenith. Non-local electrons from higher in the atmosphere are suggested as a possible extra source; alternatively, the zenith measurements may be perturbed by scattered horizon light. The band intensity in the nightglow cannot be measured; the upper limit is 1 R.  相似文献   

Interpreting vertical plasma drift in the mid-lattitude ionosphere using ionosonde measurements     

R. J. Sica

R. W. Schunk 《Planetary and Space Science》1990,38(12):1567-1571

Measurements of the density at the F₂ peak (N_mF₂) were obtained by the Boulder, Colorado, ionosonde as part of the SUNDIAL-86 campaign. The measurements were made during a period of low to moderate geomagnetic activity following a “disturbed” day. These measurements were then used to estimate the height of the F₂ peak (h_mF₂). A three-dimensional time-dependent model of Earth's ionosphere was used to calculate N_mF₂ and h_mF₂ using the vertical plasma drift as a free parameter. Since the plasmasphere-ionosphere exchange flux can remain upward during the night for these conditions, different feasible flux scenarios were inputed to the ionospheric model. These different flux scenarios had a large effect on the “induced” vertical plasma drifts required to match the measurements (i.e. at times greater than a factor of 2 in speed or a difference in direction). Futhermore, uncertainty in the O⁺---O collision frequency changes the required vertical plasma drift at night. Despite knowledge of h_mF₂, interpretation of the vertical plasma drifts as meridional neutral winds is compromised by a lack of knowledge of the plasmasphere-ionosphere exchange flux following disturbed days.  相似文献   

Neutral and ion-exospheres in the solar wind with applications to mercury     

R.E. Hartle  K.W. Ogilvie  C.S. Wu 《Planetary and Space Science》1973,21(12):2181-2191

A model of planetary neutral and ion-exospheres in the solar wind is formulated for weak or lunar like solar-wind interaction with a planet. The neutral exosphere model allows for density and temperature variations and for rotation at the exobase. The ion-exosphere is produced by ionization of the neutral exosphere in the solar wind and its density distribution is obtained by solving the continuity equation in the drift approximation. Applying to Mercury a surface temperature distribution inferred from infra-red data and a vanishing bound neutral flux at the base, He and He⁺ density distributions are found. When the He atmosphere of Mercury is due entirely to the surface bombardment by solar wind He⁺⁺, the resulting He⁺ density is found to vary from 1.5 × 10⁻¹ to 10⁻³ cm⁻³ over the range 1.5–5 planetocentric radii on the dayside. These densities are found to be detectable by typical solar-wind plasma instruments. The possible effects of cyclotron-resonant scattering by interplanetary magnetic field fluctuations are examined and shown to be negligible. An electromagnetic plasma instability, triggered by the birth of ions in the exosphere, is shown to be important for the thermalization of the energy mode transverse to the interplanetary magnetic field, allowing more ions to be detected by solar-wind ion probes.  相似文献   

Pc 1–2 observations of heavy ion effects by synchronous satellite ATS-6     

B. J. Fraser 《Planetary and Space Science》1982,30(12):1229-1238

Ion cyclotron waves generated in the magnetosphere by the ion cyclotron instability of protons are thought to be the origin of Pc 1–2 geomagnetic pulsations. Propagation characteristics of these waves have been measured using ATS-6 synchronous satellite magnetometer wave data. Of particular interest are the wave spectra, polarization properties, and wave diagnostics; all are characteristic of propagation in a cool ambient magnetospheric plasma containing He⁺ and O⁺ heavy ions.  相似文献   

A combined optical and radio study of the solar ejection of 1982 January 22     

Wang Jia-long  Kong Fan-xi 《Chinese Astronomy and Astrophysics》1984,8(4):335-339

The limb event 1982 Jan 22 with Type III + V and Type II bursts and Ha mass ejection is described. The bursts in short dm and cm waves are discussed in terms of the flux rate — time curve. For one main ejection, we find a magnetic field of ~12 G, a mass of ~10³⁸ electrons or ~10¹⁴g and an energy of 8 × 10²⁹ erg. We estimate the total energy of this event to be 10³⁰ erg.  相似文献   

Measurements of radio noise at 0.700 mc and 2.200 mc from a high-altitude rocket probe     

G. R. Huguenin  A. E. Lilley  W. H. McDonough  M. D. Papagiannis 《Planetary and Space Science》1964,12(12):1157-1167

Radio noise observations at frequencies of 0·700 Mc and 2·200 Mc were made at altitudes between 3000 and 11,000 km from a Blue Scout Jr. high-altitude rocket probe on 30 July 1963. A steady background flux of (7·5₋₃⁺⁶) × 10⁻¹⁹ W m⁻²)(c/s)⁻¹ at 0·700 Mc and (1·8^+1.0_−0.5 × 10⁻¹⁹ W m⁻² (c/s)⁻¹ at 2·200 Mc was observed. Assuming a galactic origin of the observed fluxes at both frequencies, the averaged sky brightnesses are b(0·700 Mc) = (6₋₃⁺⁵) × 10⁻²⁰ W m⁻² (c/s)⁻¹ sr⁻¹b(2·200 Mc) = (1.4^+1.0_−0.5 × 10⁻²⁰ W m⁻² (c/s)⁻¹ sr⁻¹ The observed brightness at 2·200 Mc is in reasonable agreement with the results of other observers. The apparent brightness at 0·700 Mc is, however, greater than was expected from previous observations. An alternative source of the 0·700 Mc flux in the terrestrial exosphere, as well as characteristics of several noise bursts observed during the flight, is briefly discussed.  相似文献   

Properties of energetic water-group ions in the extended pick-up region surrounding comet Giacobini-Zinner     

I. G. Richardson  S. W. H. Cowley  R. J. Hynds

P. W. Daly

T. R. Sanderson  K. -P. Wenzel 《Planetary and Space Science》1988,36(12):1429-1450

The properties of energetic (65–95 keV) cometary water-group ions in the extended solar wind pick-up region surrounding comet Giacobini-Zinner are examined using data from the EPAS instrument on the ICE spacecraft. In the outer part of this region, extending from cometocentric distances of several hundred thousand to a few million kilometres (the limit of pick-up ion detectability), it is found that large modulations of the ion flux occur (with J_MAX/J_MIN 10²-10³) which are related to the direction of the magnetic field. It is also found that the ions stream in a direction which is intermediate between the directions of the solar wind flow and the E × B drift, and that ions are present at energies somewhat above the local pick-up energy. These properties indicate that the waves which are excited by the unstable “ring-beam” pick-up ion velocity distributions do result in significant scattering of the ions in this region, both in pitch angle and in energy, but that they have insufficient amplitude to scatter the ions into near isotropy in the solar wind frame. Closer to the comet (but still upstream from the bow shock), the ion flux modulations are considerably reduced in amplitude and the ions respond less to the E × B drift, indicating that the ions are scattered nearer to isotropy in this region. Inbound, this transition takes place relatively abruptly at a distance of 4 × 10⁵ km in association with an increase in the solar wind speed, after which the ion flux increases, and ceases to be modulated by the field direction, while the streaming direction is continuously antisolar and unmodulated by the direction of the E × B drift. Outbound, weak vestiges of the ring-beam ion anisotropy are present in the region immediately upstream from the bow shock (at −1 × 10⁵ km), but these become more marked at distances in excess of t4 × 10⁵ km, increasing gradually with increasing distance from the comet. It is shown that the evolution of the ion properties is qualitatively consistent with expectations based on quasi-linear diffusion of the ions by the magnetosonic waves observed during the encounter.  相似文献   

Measurements of low energy auroral ions     

A. Urban 《Planetary and Space Science》1981,29(12):1353-1365

This paper summarizes ion meaurements in the energy range 0.1–30keV observed during the campaigns “Substorm Phenomena” and “Porcupine”. For a clear survey of the physical processes during extraordinary events, sometimes ion meaurements of higher energies are also taken into account. Generally, the pitch angle distributions were isotropic during all flights except some remarkable events. In general the ion and electron flux intensities correlated, but sometimes revealed a spectral anti-correlation.

Acceleration of the ions by an electrostatic field aligned parallel to the magnetic field could be identified accompanied by intense electron precipitation. On the other hand deceleration of the ions was observed in other field-aligned current sheets which are indicated by the electron and magnetic field measurements. Temporal successive monoenergetic ion variations pointed to energy dispersion and to the location of the source region at 9 R_E. Furthermore, ion fluxes higher than those of the electrons were measured at pitch angles parallel to the magnetic field. Each of the examples was observed during different flights. The integral down-going number and energy flux of the ions contributed to the total particle or energy influx between 65% and less than 7% and did not clearly characterize the geophysical launch conditions or auroral activities.  相似文献