The evolution of pearls in the earth's magnetosphere

Propagation and amplification of the pearls are analysed, with diffusion of wave trains in the k-space taken into account. The competition between the instability-induced amplification and the diffusion determines the values of magnetospheric parameters at which the appearance of pearls is possible. Diffusion is particularly large under conditions of a thin plasmapause and generation of pearls there is hindered or is not possible at all.     

On solar wind interaction with the earth's magnetosphere

Hydrodynamic and electrodynamic problems of solar wind interaction with the Earth's magnetosphere on the day-side are investigated.The initial fact, well established, is that the density of the magnetic field energy in the solar wind is rather small. Magnetic field intensity and orientation are shown to determine the character of the solar wind flow around the magnetosphere. For mean parameters of the wind, if the tangential component of the magnetic field is more or equal 5γ, the flow in the magneto-sheath will be laminar. For other cases the flow is of a turbulent type.For turbulent flow, typical plasma parameters are estimated: mean free path, internal scale of inhomogeneities and dissipated energy. The results obtained are compared with experimental data.For the case of laminar flow, special attention is paid to the situation when magnetic fields of the solar wind and Earth are antiparallel. It is suggested, on the basis of solid arguments, that the southward interplanetary field diffuses from the magnetosheath into the Earth's magnetosphere. These ideas are used for the estimation of the distance to the magnetopause subsolar point. A detailed comparison with results of observation is made. The coincidence is satisfactory. Theoretical investigation has been made to a great extent for thin magnetopause with thickness δ ～ R_He-gyroradius of an electron.It is shown that during magnetospheric substorms relaxation oscillations with the period τ = 100–300 sec must appear. A theorem is proved about the appearance of a westward electrical field during the substorm development, when the magnetosphere's day-side boundary moves Earthward and about the recovery phase, when the magnetopause motion is away from the Earth, when there is an eastward electrical field.In the Appendix, plasma wave exitation in the magnetopause is considered and conductivity magnitudes are calculated, including the reduction due to the scattering by plasma turbulence.     

Nonlinear hydrodynamic VLF wave scattering in the earth's magnetosphere

The paper deals with a nonlinear instability of quasi-monochromatic VLF signals and whistlers in the Earth's magnetosphere due to induced scattering. The instability growth rates and the threshold values of the signal amplitude at which the instability occurs have been found. The instability is shown to be more effectively excited when the initial transverse VLF wave transforms into plasma oscillations at the lower hybrid resonance (LHR) frequency and may be responsible for the phenomena such as trigger LHR emission, the amplitude and phase modulation of artificial VLF signals and be the origin of some types of discrete VLF signals.     

The Moon's zonal tidal effect in the variation of the earth's spin rate

Using the time observations obtained by 8 instruments in the Chinese Joint System during the years 1966–1980, we analyse the Moon's zonal tidal effect. The results show that the effects of the M_f and M_m waves are obvious. From this, the parameters $\text{K}\text{C}$ of the zonal tide are estimated and the weighted averages of the 8 instruments are $\text{(}\text{K}\text{C}\text{)}\text{M}{}_{\mathrm{f}}\text{= 0.909 ± 0.114}\text{and}\text{(}\text{K}\text{C}\text{)}\text{M}{}_{\mathrm{m}}\text{= 0.905 ± 0.083}$ respectively.     

Io's interaction with the magnetosphere

Jupiter's innermost Galilean satellite Io is regarded as a fairly good conductor ($\text{σ > 10}{}^{\mathrm{?5}}\text{Ω}{}^{\mathrm{?1}}\text{m}{}^{\mathrm{?1}}$). The trapping of magnetic field lines by Io and their deformation is described. A neutral point forms in the vicinity of the satellite. The magnetic field annihilation in the neutral point is enhanced by the emission of low frequency hmd waves. The power carried away by these waves may be as high 10¹⁵ W. The characteristic frequency of the wave and its variation while Io orbits around Jupiter is determined.     

Terrestrial myriametric radiation from the earth's plasmapause

Terrestrial myriametric radiation (non-thermal continuum) observed by the GEOS 1 spacecraft is used to determine the radial profile of plasma density at the equatorial plasmapause. The method utilises the properties of a radio window through which the radiation propagates. The radial density profile obtained by remote sensing is compared with that implied from natural electrostatic emissions as the spacecraft approaches the equatorial source region. The TMR profile appears to be that of the cold plasma whereas the frequencies of the intense non-equatorial emissions beyond the plasmapause are governed by the hot and cold components. Ray-tracing and polarisation computations indicate that a simplistic interpretation of direction-finding measurements using the spinning dipole technique could lead to erroneous source directions under certain circumstances. In such cases if the spacecraft orientation is known corrections can be applied to yield the true direction.     

Ion-ion recombination rates in the earth's atmosphere

The temperature dependence of the binary recombination coefficient, α₂, for the reaction NO⁺+NO₂^? → products has been obtained over the range 185–530 K. It is found that the corresponding mean cross section $\text{σ}$ is described by the power law $\text{σ}\text{? A · T}{}^{\mathrm{?0.9}}$, and that α₂ ? B · T^?0.4. Data has also been obtained for two cluster ion recombination reactions which indicate that their recombination cross sections are only about 40% larger than for the parent ions at a given temperature, the cross sections for these reactions also apparently increasing with decreasing temperature. In the light of this data and by considering the most probable positive and negative ions existing at various altitudes up to 90km in the atmosphere, the most appropriate ionic recombination coefficients in various altitude ranges are deduced. Thus, between 30 and 90 km, where the recombination process is two-body, the coefficient varies over the narrow range 5–9 × 10^?8 cm³s^?1, while below 30 km the process is predominantly three-body with an effective two-body rate increasing rapidly to a maximum value ≈3 × 10^?6 cm³s^?1 in the troposphere, these deductions being based on published laboratory determinations of three-body recombination coefficients.     

Jupiter's ionosphere and magnetosphere

The distribution of ionization and the temperature variation in the Jovian ionosphere is determined by simultaneously solving the momentum and chemical equations for electrons, ions and neutrals together with their respective heat transport equation. The boundary conditions at the bottom of the ionosphere are chosen in accordance with recent infra-red and occultation measurements. The ionosphere is hotter than previously thought. The electron temperature may be as high as 1500 K. A considerable flux of particles can escape from the ionosphere. These particles are trapped in the Jovian magnetosphere by a two-stream instability. A Gledhill disk will form. The variation of plasma density along Io's orbit is calculated.     

The effect of the earth's bow shock and magnetosheath on the interaction of a discontinuity in the solar wind with the magnetosphere

A theoretical model is proposed for the interaction of a plane discontinuity in the solar wind with the magnetosphere. The presence of the bow shock and magnetosheath are taken into account, the calculation being based on the Spreiter et al. (1966) gas-dynamic model for a solar wind Mach Number M = 5. The model proposed predicts the manner in which the shape of the interplanetary discontinuity is distorted in its passage through the magnetosheath; it is found that the point of first impact with the magnetopause makes an angle of 56° with the Sun-Earth line for relatively quiet solar wind conditions.     

The viscous-like magnetospheric convection and the length of the earth's magnetotail

An estimate of an upper bound on the length of the Earth's magnetotail has been made under the assumptions that (1) the flux of open magnetic field lines in the polar caps never vanishes and (2) the annihilation of the open field line flux is extremely low during magnetically quiet periods. These two basic assumptions are discussed and justified. It is found that the tail may be as long as 6000 Re (0.25 a.u.) after a prolonged quiet time period. On the other hand, the length of the shortest tail, which would result from a sequence of strong magnetospheric substorms, is estimated to be ～ 600 Re. These events are thus capable of shortening the tail by an order of magnitude.     

On the interaction of auroral protons with the earth's atmosphere

The interaction of energetic auroral protons with the atmosphere is investigated. The results of a random number algorithm that describes the proton-hydrogen interconversion reactions as the beam loses energy are adopted to construct an energy deposition curve applicable over a wide range of initial proton energies. lonization rates and production rates of ejected electrons are computed and emission rates of hydrogen Balmer alpha and beta lines are evaluated using recently available low energy cross-sections.     

Electric fields and currents in the earth's polar caps

A model for solar wind flow around the magnetopause incorporating a stagnation line at the frontside magnetopause is used to derive a formula for the electric field intensity and polar cap potential drop. These relationships are compared to experimental data from polar orbiting satellites. The relation between solar wind parameters and auroral arc velocity is also studied.     

Concerning the planetary system of Barnard's star

The data pertaining to the proper motion of Barnard's Star are reanalyzed, It is shown that at least two dark compan ions are required to explain the observations. It is found that the orbits of the two companions (B1 and B2) are not coplanar, but have relative inclination ?50°.     

Interpretation of magnetic field perturbations in the earth's magnetopause boundary layers

Studies of the boundary layers in the vicinity of the Earth's dayside magnetopause are important in determining the nature of the processes which couple the magnetosphere to the flowing solar wind, thereby driving magnetospheric convection. In this paper we examine theoretically the magnetic field and plasma properties expected in the boundary regions for various models involving either diffusion or reconnection at the boundary. For diffusion models the transport of magnetosheath momentum across the magnetopause will result in field shears on either side of the boundary, the field rotations being in opposite senses on either side relative to the undisturbed fields. The directions of these rotations depend upon location at the magnetopause relative to the momentum transfer region and to the noon meridian. In reconnection models the effect of the tension of the open boundary layer field lines must be taken into account in addition to the magnetosheath flow, but on the super-Alfvénic flanks of the magnetosphere the latter still dominates, so that qualitatively similar effects will occur in the two models. More detailed, quantitative or statistical studies are then required to distinguish the two models in this regime. In the sub-Alfvénic dayside region, however, open field tension effects will dominate in reconnection models such that boundary layer field and plasma properties will then be determined mainly by the magnetosheath magnetic field configuration. In particular the East-West flow in the magnetospheric boundary layer will be controlled largely by the East-West field in the magnetosheath, leading to flow reversals across the magnetopause in some quadrants of the magnetopause. This behaviour is directly related to the Svalgaard-Mansurov effect and is a signature unique to reconnection models. The boundary layer fields are also expected to tilt towards the field on the opposite side of the boundary in these models on the dayside. “Toward” tilting can also occur in this regime in diffusion models, but “away” tilting, a signature unique to dayside diffusion, should also occur equally frequently. Finally, we briefly discuss previously published high-resolution ISEE 1 and 2 data from the boundary regions in the light of our results. We find that “toward” tilting generally occurs in boundary region crossings previously identified as being reconnection-associated and we present some examples in which the above unique reconnection signature has been observed. During impulsive FTE-like events, however, the field may tilt in either direction, possibly as a result of field line twists, thus complicating our simple picture in this case. We also show that the “reverse draping” observations presented by Hones et al. (1982) approximately satisfy the open magnetopause stress balance conditions.     

Model studies of nitric oxide fluorescence in the earth's backscattered spectrum

Fluorescent emissions from nitric oxide appear imposed upon the Rayleigh backscattered spectrum of the earth's atmosphere between 250 and 300 nm in wavelength. Satellite instruments designed to monitor the global ozone distribution can routinely observe these signals although techniques for exploiting the data are not yet available. Application of a radiative transfer equation developed for an atmosphere including absorption by ozone, molecular scattering, and nitric oxide fluorescence shows the three most prominent NO emissions relative to the 250–300 nm backscattered sunlight to be the (1,4), (1,6), and (0,3) gamma bands. Analysis of the contribution function for each emission band indicates that the fluorescent signals can provide useful information on the magnitude and variability of nitric oxide between 40 and 140 km in altitude.     

Distribution functions for energetic oxygen atoms in the earth's lower atmosphere

Direct photolysis of O₃ and quenching of $\text{O}\text{(}{}^1\text{D}\text{)}$ by N₂ provide abundant sources of fast oxygen atoms for the Earth's lower atmosphere. The concentration of atoms with energy above 0.7 eV may exceed the concentration of $\text{O}\text{(}{}^1\text{D}\text{)}$ for all altitudes below 18 km and these atoms may play an important role in lower atmospheric chemistry. Distribution functions for $\text{O}\text{(}{}^3\text{P}\text{)}$ are given for the energy interval 0.1-1.3 eV, for a range of altitudes from 0 to 62 km.     

Electrostatic wave noise in the neutral sheet in the earth's geomagnetic tail

Numerical solutions are obtained from analytic dispersion relations for electrostatic waves in a self-consistent, one-dimensional magnetic neutral sheet. The dispersion relations are solved in the real wave number and complex frequency domain. The properties of wave modes will be described, with special emphasis on instability. Several regimes of instability are identified which may generally be divided into two classes. Wave growth is associated firstly with counterstreaming between ions and electrons, giving rise to low frequency waves similar to the usual electrostatic two-stream mode. In addition, high frequency growing waves occur, associated with harmonics of the electron oscillation frequency across the neutral plane.     

Electron distribution function and ion concentrations in the earth's lower ionosphere from Boltzmann-Fokker-Planck theory

Using the Boltzmann-Fokker-Planck method and the local approximation we derive coupled non-linear equations for the electron and ion concentrations and the energy-dependent electron distribution function in the Earth's lower ionosphere. These equations are new and give the appropriate generalization of the standard electron-ion continuity equations in the local approximation when electron-neutral particle impact ionization is treated rigorously. We report stable, numerical solutions to these equations and compare our calculated electron concentration to the experimentally determined result for a rocket experiment where the electron concentration and solar EUV spectral flux were measured simultaneously.     

Relaxational dissipation in atmospheric waves—II. Application to earth's upper atmosphere

A dispersion relation is derived for acoustic-gravity waves propagating in a multiconstituent gas whose atoms and molecules are subject to relaxational exchanges of thermal energy between translational and internal forms. The relation employs a complex thermal capacitance, derived in a companion paper, which incorporates the relaxational effects. Approximations to this relation permit ready assessment of the attenuation of wave amplitude and energy that relaxation produces, both in absolute amount and relative to viscous attenuation.In Earth's upper atmosphere, relaxational attenuation is found to be of greatest potential consequence in the middle and upper E region. Both electronic relaxation in atomic oxygen and vibrational relaxation in molecular oxygen and nitrogen appear to be capable of playing a significant role, but it is found that the actual significance of their roles cannot be assessed adequately because of present uncertainties of governing parameters (and, in the case of vibrational relaxation, of governing collisional interactions). Similar uncertainties are found to surround the role that relaxation, notably in atomic oxygen, may play in the termination of turbulence near the 110 km level.     

The formation of saturn's satellites and rings,as influenced by saturn's contraction history

We have used Pollack et al.'s 1976 calculations of the quasi-equilibrium contraction of Saturn to study the influence of the planet's early high luminosity on the formation of its satellites and rings. Assuming that the condensation of ices ceased at the same time within Jupiter's and Saturn's primordial nebulae, and using limits for the time of cessation derived for Jupiter's system by Pollack and Reynolds (1974) and Cameron and Pollack (1975), we arrive at the following tentative conclusions. Titan is the innermost satellite at whose position a methane-containing ice could condense, a result consistent with the presence of methane in this satellite's atmosphere. Water ice may have been able to condense at the position of all the satellites, a result consistent with the occurrence of low-density satellites close to Saturn. The systematic decrease in the mass of Saturn's regular satellites with decreasing distance from Saturn may have been caused partially by the larger time intervals for the closer satellites between the start of contraction and the first condensation of ices at their positions and between the start of contraction and the time at which Saturn's radius became less than a satellite's orbital radius. Ammonia ices, principally NH₄SH, were able to condense at the positions of all but the innermost satellites.Water ice may bave been able to condense in the region of the rings close to the end of the condensation period. We speculate that the rings are unique to Saturn because on the one hand, temperatures within Jupiter's Roche limit never became cool enough for ice particles to form before the end of the condensation period and on the other hand, ice particles formed only very early within Uranus' and Neptune's Roche limits, and were eliminated by gas drag effects that caused them to spiral into the planet before the gas of these planets' nebula was eliminated. Gas drag would also have eliminated any rocky particles initially present inside the Roche limit.We also derive an independent estimate of several million years for the time between the start of the quasi-equilibrium contraction of Saturn and the cessation of condensation. This estimate is based on the density and mass characteristics of Saturn's satellites. Using this value rather than the one found for Jupiter's satellites, we find that the above conclusions about the rings and the condensation of methane-and ammonia-containing ices remain valid.