On fourier-analysis of geomagnetic pulsations pc-1, “two-fold” and “three-fold” pulsations pc-1 and fundamental frequencies of the magnetospheric cavity—I

The paper gives the results of detailed studies of the frequency spectra $\text{S}{}_{\mathrm{s}}\text{(?)}$ of the chain of the wave packets F_s(t) of geomagnetic pulsations PC-1 recorded at the Novolazarevskaya station. The bulk of the energy of F_s(t) is concentrated in the vicinity of the central frequencies $\text{?}{}_{\mathrm{s0}}$ of spectra—the carrier frequencies of the signals. The velocity $\text{V}{}_0\text{≌ 6.10}{}^3\text{km s}{}^{\mathrm{?1}}$ of the flux of protons generating these signals correspond to them. The spectra of the signals have oscillations—“satellites” irregularly distributed in frequency. These satellites, as the authors believe, testify to the presence of the individual groups of protons of low concentration whose velocities vary within 10³–10⁴ km s^?1.Their energy is only of the order of 10^?2–10^?3 of the energy of the main proton flux. Clearly pronounced maxima on double and triple frequencies $\text{? = 2?}{}_{\mathrm{s0}}\text{and}\text{3?}{}_{\mathrm{s0}}$ are detected. They show that the generation of pulsations PC-1 is accompanied by the generation on the overtones of wave packets called in this paper “two-fold” and “three-fold” pulsations PC-1. Intensive symmetrical satellites of a modulation character have been discovered on frequencies $\text{?}{}^{\mathrm{\pm }}{}_{\mathrm{sK}}$. Frequency differences $\text{Δ?}{}_{\mathrm{sK}}{}^{\mathrm{\pm }}\text{=}\text{¦?}{}_{\mathrm{s0}}\text{? ?}{}_{\mathrm{sK}}{}^{\mathrm{\pm }}\text{¦}\text{= (0.011,0.022}\text{and}\text{0.035)}\text{Hz}$ correspond to them. The authors believe that the values of Δ?^±_sK are resonance frequencies of the magnetospheric cavity in which geomagnetic pulsations PC-1 are generated. It is established that the values of Δ?^±_sK coincide closely with the carrier frequencies of geomagnetic pulsations PC-3 and PC-4 generated in the magnetosphere. This leads to the conclusion that the resonance oscillations of the magnetospheric cavity are their source. Thus, the generation of geomagnetic pulsations of different types and resonance oscillations in the magnetosphere are integrated into a unified process. The importance of the results obtained and the necessity to check further their trustworthiness and universality, using experimental data gathered in different conditions, is stressed.     

On the photodissociation of water vapour in the mesosphere

The photodissociation of water vapour in the mesosphere depends on the absorption of solar radiation in the region (175–200 nm) of the O₂ Schumann-Runge band system and also at H-Lyman alpha. The photodissociation products are OH + H, OH + H, O + 2H and H₂ + O at Lyman alpha; the percentages for these four channels are 70, 8, 12 and 10%, respectively, but OH + H is the only channel between 175 and 200 nm. Such proportions lead to a production of H atoms corresponding to practically the total photodissociation of H₂O, while the production of H₂ molecules is only 10% of the H₂O photodissociation by Lyman alpha.The photodissociation frequency (s^?1) at Lyman alpha can be expressed by a simple formula

$\text{J}{}_{\mathrm{<mtext>Ly</mtext><mtext>\alpha </mtext>}}\text{H}{}_2\text{O=4.5 ×10}{}^{\mathrm{?6}}\text{1+0.2}\text{F}{}_{10.7}\text{?65}\text{100}\text{exp}\text{[?4.4 ×10}{}^{\mathrm{?19}}\text{N}{}^{0.917}\text{]}$

where F_{10.7 cm} is the solar radioflux at 10.7 cm and N the total number of O₂ molecules (cm^?2), and when the following conventional value is accepted for the Lyman alpha solar irradiance at the top of the Earth's atmosphere ($\text{Δλ = 3.5}\text{A}\text{?}$) q_Lyα,∞ = 3 × 10¹¹ photons cm^?2 s^1?.The photodissociation frequency for the Schumann-Runge band region is also given for mesospheric conditions by a simple formula

$\text{J}{}_{\mathrm{<mtext>SRB</mtext>}}\text{(}\text{H}{}_2\text{O}\text{) = J}{}_{\mathrm{<mtext>SRB</mtext><mtext>,\infty </mtext>}}\text{(}\text{H}{}_2\text{O}\text{) exp [?10}{}^{\mathrm{?7}}\text{N}{}^{0.35}\text{]}$

where J_SRB,∞(H₂O) = 1.2 × 10^?6 and 1.4 × 10^?6 s^?1 for quiet and active sun conditions, respectively.The precision of both formulae is good, with an uncertainty less than 10%, but their accuracy depends on the accuracy of observational and experimental parameters such as the absolute solar irradiances, the variable transmittance of O₂ and the H₂O effective absorption cross sections. The various uncertainties are discussed. As an example, the absolute values deduced from the above formulae could be decreased by about 25-20% if the possible minimum values of the solar irradiances were used.     

A self-consistent evaluation of the rate constants for the production of the OI 6300 Å airglow

The quenching rate k_N2 of $\text{O(}{}^1\text{D)}$ by N₂ and the specific recombination rate α_1D of O₂⁺ leading to $\text{O(}{}^1\text{D)}$ are re-examined in light of available laboratory and satellite data. Use of recent experimental values for the $\text{O(}{}^1\text{D)}$ transition probabilities in a re-analysis of AE-C satellite 6300 Å airglow data results in a value for k_N2 of 2.3 × 10^?11 cm³s^?1 at thermospheric temperatures, in excellent agreement with the laboratory measurements. This implies a value of J_O2 = 1.5 × 10^?6s^?1 for the O₂ photodissociation rate in the Schumann-Runge continuum. The specific recombination coefficient α_1D = 2.1 × 10^?7cm³s^?1 is also in agreement with the laboratory value. Implications for the suggested $\text{N}\text{(}{}^2\text{D) + O}{}_2\text{→ O(}{}^1\text{D) + NO}$ reaction are discussed.     

Residual mass from atmospheric ablation of small meteoroids

Numerical solutions of the equations of meteor ablation in the Earth's atmosphere have been obtained using a variable step size Runge-Kutta technique in order to determine the size of the residual mass resulting from atmospheric flight. The equations used include effects of meteoroid heat capacity and thermal radiation, and a realistic atmospheric density profile. Results were obtained for initial masses in the range 10^?7–10^?2 g, and for initial velocities less than 24 km s^?1 (results indicated no appreciable residual mass for meteors with velocities above 24 km s^?1 in this mass range). The following function has been obtained to provide the logarithm of the ratio of the residual mass following atmospheric ablation to the original preatmospheric mass

$\text{log r = 4.7 ?0.33v}{}_{\mathrm{\infty }}\text{?0.013v}{}_{\mathrm{\infty }}{}^2\text{+ 1.2 log m}{}_{\mathrm{\infty }}\text{+ 0.08 log}{}^2\text{m}{}_{\mathrm{\infty }}\text{?0.083v}{}_{\mathrm{\infty }}\text{log m}{}_{\mathrm{\infty }}\text{M}$

The pre-atmospheric mass and velocity are represented by m_∞ and v_∞.When the results are expressed in terms of the size of the residual mass following atmospheric ablation as a function of the initial mass and velocity, it is found that the final residual mass is almost independent of the original mass of the meteoroid, but very strongly dependent on the original velocity. For example, the residual mass is very nearly 10^?7 g for a meteoroid with velocity 18 kms^?1 for initial masses from 10^?7 to 10^?3 g. On the other hand, a slight change in the initial velocity to 20 km s^?1 will shift the residual mass to approx. 10^?8 g. This strong velocity dependence coupled with the weak dependence on the original mass has important consequences for the sampling of ablation product micrometeorites.     

Charge exchange of metastable D oxygen ions with N2 in the thermosphere

Measurements of N₂⁺ and supporting data made on the Atmosphere Explorer-C satellite in the ionosphere are used to study the charge exchange process

$\text{O}{}^{\mathrm{+}}\text{(}{}^2\text{D}\text{)+}\text{N}{}_2\text{→}\text{k}\text{N}{}^{\mathrm{+}}{}_2\text{+}\text{O}$

The equality k = (5 ± 1.7) × 10^?10cm³s^?1. This value lies close to the lower limit of experimental uncertainty of the rate coefficient determined in the laboratory. We have also investigated atomic oxygen quenching of O⁺(²D) and find that the rate coefficient is 2 × 10^?11 cm³s^?1 to within approximately a factor of two.     

Electric fields and potential patterns in the high-latitude ionosphere for different situations in interplanetary space

The potential ? of the electric field at high latitudes has been obtained by solving numerically the second order differential equation in spherical coordinates:

$\text{?}\text{1}\text{2}\text{(rσ}{}^{\mathrm{H}}\text{?}{}_{\mathrm{\theta }}\text{)}{}_{\mathrm{\theta }}\text{+}\text{1}\text{r}\text{(σ}{}^{\mathrm{H}}\text{?λ)}{}_{\mathrm{\lambda }}\text{+}\text{1}\text{r}\text{(σ}{}^{\mathrm{P}}\text{?}{}_{\mathrm{\lambda }}\text{)}{}_{\mathrm{\theta }}\text{?(σ}{}^{\mathrm{P}}\text{?}{}_{\mathrm{\theta }}\text{)}{}_{\mathrm{\lambda }}\text{=}\text{1}\text{r}\text{(rψ}{}_{\mathrm{\theta }}\text{)}{}_{\mathrm{\theta }}\text{+}\text{1}\text{r}{}^2\text{ψ}{}_{\mathrm{\lambda \lambda }}$

, where θ is colatitude, λ is longitude, σ^H and σ^P are the height-integrated Hall and Perdersen ionospheric conductivities, r = sinθ, and ψ is the current function. The boundary condition is ? = 0 on the geomagnetic parallel θ = 34°. Values of ψ are determined from geomagnetic field variations at the Earth's surface from geomagnetic field variations at the Earth's surface for various conditions in interplanetary space. σ^P and σ^H are taken to vary with season, local time, tilt of the geomagnetic dipole axis (UT), and intensity of corpuscular precipitation (the model proposed by Wallis and Budzinski, 1981). The model distributions of ?^M and E^M = -▽?^m so obtained are compared with observational results. The feasibility has been demonstrated of interpreting the statistical results and individual measurement data in terms of a unified dynamic model of ionospheric electric fields. The model makes allowance for the changes of electromagnetic “weather” in interplanetary space.     

Estimates of quasipolar absorption by methane in the atmosphere of Titan

The basis for “quasipolar” absorption (QPA) by CH₄ is the existence of a small electric dipole moment in its ground state. The integrated intensity α_QPA at a temperature of 90K is calculated to be between 4.8 × 10^?5 and 1.9 × 10^?2 cm^?2 atm^?1. With an assumed mean pressure of 0.1 atm and a relative abundance of $\text{[}\text{CH}{}_4\text{]}\text{[}\text{H}{}_2\text{]}\text{= 1}$, it is estimated that the ratio of quasipolar to pressure-induced absorption (PIA) is 0.05 ? α_QPA/α_PIA ? 18 for the spectral range from 0 to 300 cm^?1. This result suggests that quasipolar absorption may contribute to a weak, CH₄-induced greenhouse in the atmosphere of Titan.     

Possibility of the investigation of interplanetary shock interaction with the earth's bow shock,magnetopause and plasmapause by means of a non-coherent response method

The problem of interaction between the interplanetary shock of 8 March, 1970 and the Earth's bow shock, magnetopause and plasmapause is considered. Estimates are made using existing models of the moments of initial impulsive interaction of interplanetary shocks with the bow shock and of the secondary interaction of the resulting split discontinuities with the magnetopause, plasmapause and a modified bow shock. Using computed data on the plasma's concentration jumps at discontinuities and on the latters' velocities, estimates have been carried out of remote sounding and the response signals' phase difference change rates Δf (which were found to be of the order of ～ 10^?3?10^?2Hz) appearing on the radio path with a non-coherent response near the subsolar region. It has been ascertained that the non-coherent response method permits, by using generators with a stability of $\text{ε =}\text{δ}{}_{\mathrm{<mtext>r</mtext>}}\text{f}\text{f}{}_{\mathrm{<mtext>O</mtext>}}\text{= 10}{}^{\mathrm{?11}}\text{?10}{}^{\mathrm{?10}}$, effective investigation (with a good time resolution) of the impulsive interaction of interplanetary shocks with the plasma discontinuities of the bow shockmagnetopause-plasmapause system.     

Determination of magnetic field direction in a comet's head

The Stokes parameters of resonance radiation scattered by a Na atom with the angular momentum F aligned by directed unpolarized radiation in a magnetic field H ～ 10^?5?10^?1 Oe are presented. An influence of the orientation of the magnetic field on these parameters are studied; the intensity ratio $\text{I(D}{}_2\text{)}\text{I(D}{}_1\text{)}$ changes within ±5%, and the polarization degree P(D₂) within ±25%. Measurements of $\text{I(D}{}_2\text{)}\text{I(D}{}_1\text{)}$ and P(D₂), if the geometry of scattering is known, may give information on the direction of the magnetic field in the sodium atmospheres of comets, as well as Io's sodium cloud or man-made cosmic clouds.     

Numerical studies of the transport of solar protons in interplanetary space

Numerical solutions of the Fokker-Planck equation governing the transport of solar protons are obtained using the Crank-Nicholson technique with the diffusion coefficient represented by K_r=K₀r^b where r is radial distance from the Sun and b can take on positive or negative values. As b ranges from +1 to ?3, the time to the observation of peak flux decreases by a factor of 5 for 1 MeV protons when $\text{V}\text{K}{}_0\text{=}\text{3 AU}{}^{\mathrm{b?1}}$ where V is the solar wind speed. The time to peak flux is found to be very insensitive to assumptions concerning the solar and outer scattering boundary conditions and the presence of exponential time decay in the flux does not depend on the existence of an outer boundary. At $\text{V}\text{K}{}_0\text{? 15 AU}{}^{\mathrm{b?1}}$, 1 MeV particles come from the Sun by an almost entirely convective process and suffer large adiabatic deceleration at b?0 but for b=+1, large Fermi acceleration is possible at all reasonable $\text{V}\text{K}{}_0$ values. Implications of this result for the calculation and measurement of particle diffusion coefficients is discussed. At $\text{b?0}$, the pure diffusion approximation to transport overestimates by a factor 2 or more the time to peak flux but as b becomes more negative, the additional effects of convection and energy loss become less important.     

Damping of geomagnetic pulsations by the ionosphere

A significant sink of geomagnetic pulsation energy is due to Joule dissipation in the ionosphere. To investigate this we have computed the damping experienced by standing Alfvén waves in a dipole magnetic field. Both the uncoupled poloidal and toroidal modes are considered with Joule dissipation being introduced through a boundary condition which relates the electric and magnetic field strengths at the ionosphere, viz: $\text{4πΣ}{}_{\mathrm{p}}\text{E}\text{c}\text{= b,}\text{where}\text{Σ}{}_{\mathrm{p}}$ is the height integrated Pederson conductivity. The damping rates are strongly dependent on the ionospheric conductivity and we find that typically the normalized damping rate, $\text{γ}\text{ω}\text{,}\text{is}\text{～0.1}$ for nightside values of conductivity and ～0.01 for the dayside. This would account for the observed scale of bandwidths in pulsation signals. Away from regions of extreme damping we find γ ∝ L^?1Σ_p^?1.     

Small-scale turbulence in the atmosphere of Venus

Previous studies based on radio scintillation measurements of the atmosphere of Venus have identified two regions of small-scale temperature fluctuations located in the vicinity of 45 and 60 km. A global study of the fluctuations near 60 km, which are consistent with wind-shear-generated turbulence, was conducted using the Pioneer Venus measurements. The structure constants of refractive index fluctuations c_n² and temperature fluctuations c_T² increase poleward, peak near 70° latitude, and decrease over the pole; c_n² varies from 2 × 10^?15 to 1.5 × 10^?14m^{$\text{2}\text{3}$} and c_T² from 4 × 10^?3 to 7 × 10^?2°K²m^{$\text{?2}\text{3}$}. These results indicate greater turbulent activity at the higher latitudes. In the region near 45 km the refractive index fluctuations and the corresponding temperature fluctuations are substantially lower. Based on the analysis of one representative occultation measurement, $\text{c}{}_{\mathrm{<mtext>n</mtext>}}{}^2\text{= 2 × 10}{}^{\mathrm{?16}}\text{m}{}^{\mathrm{<mtext>?2</mtext><mtext>3</mtext>}}\text{and}\text{c}{}_{\mathrm{<mtext>T</mtext>}}{}^2\text{= 7.3 × 10}{}^{\mathrm{?4}}\text{°}\text{K}{}^2\text{m}{}^{\mathrm{<mtext>?2</mtext><mtext>3</mtext>}}$ in the 45-km region. The fluctuations in this region also appear to be consistent with wind-shear-generated turbulence. The turbulence level is considerably weaker than that at 60 km; the energy dissipation rate ε is 4.9 × 10^?5m²sec^?3 and the small-scale eddy diffusion coefficient K is 2 × 10³ cm² sec^?1.     

Further quantification of the sources and sinks of thermospheric O1D) atoms

In this paper we confirm an earlier finding that the reaction

constitutes a major source of OI 6300 Å dayglow. The rate coefficient for this reaction is found to be consistent with an auroral result, namely k₁ ≈ 6 × 10^?12cm³s^?1. We correct an error in an earlier publication and demonstrate that reaction (1) is consistent with the laboratory determined quenching rate for the reaction

where $\text{k}{}_2\text{= 2.3 × 10}{}^{\mathrm{?11}}\text{cm}{}^3\text{s}{}^{\mathrm{?1}}$. Dissociative recombination of O⁺₂ with electrons is found to be a major daytime source in summer above ～220 km.     

A dynamical effect in the ionospheric f1 layer

Incoherent scatter observations of the ionospheric F₁ layer above Saint-Santin (44.6°N) are analyzed after correction of a systematic error at 165 and 180 km altitude. The daytime valley observed around 200 km during summer for low solar activity conditions is explained in terms of a downward ionization drift which reaches ?30 m s^?1 around 180 km. Experimental determinations of the ion drift confirm the theoretical characteristics required for the summer daytime valley as well as for the winter behaviour without a valley. The computations require an effective dissociative recombination rate of $\text{2.3 × 10}{}^{\mathrm{?7}}\text{(}\text{300/}\text{T}{}_{\mathrm{e}}\text{)}{}^{0.7}\text{(}\text{cm}{}^3\text{s}{}^{\mathrm{?1}}\text{)}$ and ionizing fluxes compatible with solar activity conditions at the time when the valley is observed.     

Electron runaway in turbulent astrophysical plasmas

An astrophysical electron acceleration process is described which involves turbulent plasma effects: the acceleration mechanism will operate in ‘collision free’ magnetoactive astrophysical plasmas when ion-acoustic turbulence is generated by an electric field which acts parallel to the ambient magnetic lines of force. The role of ‘anomalous’ (ion-sound) resistivity is crucial in maintaining the parallel electric field. It is shown that, in spite of the turbulence, a small fraction of the electron population can accelerate freely, i.e. runaway, in the high parallel electric potential. The number density n^(B) of the runaway electron component is of order $\text{n}{}^{\mathrm{(B)}}\text{?}\text{n}\text{2}\text{(}\text{c}{}_{\mathrm{s}}\text{U}{}_{\mathrm{\parallel }}{}^{\mathrm{?}}\text{)}{}^2$, where n = background electron number density, c_s = ion-sound speed and U_∥^? = relative drift velocity between the electron and ion populations. The runaway mechanism and the number density n^(B) do not depend critically on the details of the non-linear saturation of the ion-sound instability.     

The locating of hydromagnetic whistler sources and determination of their generating proton spectra

Results are given of the calculations of the group delay time propagating τ(ω, φ₀) of hydromagnetic whistlers, using outer ionospheric models closely resembling actual conditions. The τ(ω, φ₀) dependencies were compared with the experimental data of τ_exp(ω, φ₀) obtained from sonagrams. The sonagrams were recorded in the frequency range $\text{? ? (0.5?2.5) Hz}$ at observation points located at geomagnetic latitudes φ₀ = (53?66)° and in the vicinity of the geomagnetic poles. This investigation has led us to new and important conclusions.The wave packets (W.P.) forming hydromagnetic whistlers (H.W.) are mainly generated in the plasma regions at L = 3.5?4.0. This is not consistent with ideas already expressed in the literature that their generation region is $\text{L ? 3?10}$. The overwhelming majority of the τ_exp values differ considerably from the times at which wave packets would, in theory, propagate along the magnetic field lines corresponding to those of the geomagnetic latitudes φ₀ of the observation points. The second important fact is that the W.P. frequency ω is less than $\text{Ω}{}_{\mathrm{H}}$ everywhere along its propagation trajectory, including the apogee of the magnetic force line ($\text{Ω}{}_{\mathrm{H}}$ is the proton gyrofrequency). Proton flux spectra $\text{E ? (30?120)}$ keV, responsible for H.W. generation, were determined. Comparison of the Explorer-45 and OGO-3 measurements published in the literature, with our data, showed that the proton flux density energy responsible for the H.W. excitation $\text{N}{}_{\mathrm{p}}\text{(}\text{MV}{}_6{}^2\text{2}\text{) ? (5 × 10}{}^{\mathrm{?3}}\text{?10}{}^{\mathrm{?1}}\text{)}\text{H}{}_{\mathrm{a}}{}^2\text{8π}$ where H_a is the magnetic field force in the generation region of these W.P. The electron concentration is $\text{N}{}_{\mathrm{a}}\text{? (10}{}^2\text{?10}{}^3\text{) cm}{}^{\mathrm{?3}}$. The values given in the literature are $\text{N}{}_{\mathrm{a}}\text{? (10}{}^{\mathrm{?10}}\text{?10}{}^3\text{) cm}{}^{\mathrm{?3}}$. The e data considered also leads to the conclusion that the generating mechanism of the W.P. studied probably always co-exists with the mechanism of their amplification.     

Cyclotron side-band emissions from ring-current electrons

VLF-emissions with subharmonic cyclotron frequency from magnetospheric electrons have been detected by the S³-A satellite (Explorer 45) whose orbit is close to the magnetic equatorial plane where the wave-particle interaction is most efficient. These emissions are observed during the main phase of a geomagnetic storm in the nightside of the magnetosphere outside of the plasmasphere around L = 3–5. The emissions consist essentially of two frequency regimes, one below the equatorial electron gyro-frequency, , and the other above . The emissions below are whistler mode and there is a sharp band of “missing emissions” along . The emissions above are electrostatic mode and the frequency ranges up to . It is concluded that these emissions are generated by the enhanced relativity low energy (1–5 keV) ring current electrons, penetrating into the nightside magnetosphere during the main phase of a magneto storm. Although the high energy (50–350 keV) electrons showed remarkable changes of pitch angle distribution, their associations with VLF-emissions are not so significant as those of low energy electrons.     

Low-frequency upstream wave as a probable source of low-latitude Pc 3–4 magnetic pulsations

Daytime Pc 3–4 pulsation activities observed at globally coordinated low-latitude stations [SGC (L = 1.8,λ = 118.0°W), EWA(1.15,158.1°W), ONW(1.3,141.5°E)] are evidently controlled by the cone angle θ_XB of the IMF observed at ISEE 3. Moreover, the Pc 3–4 frequencies ($\text{?}$) at the low latitudes and high latitude (COL; L = 5.6 and λ = 147.9°W) on the ground and that of compressional waves at geosynchronous orbit (GOES 2; L = 6.67 and λ = 106.7°W) are also correlated with the IMFmagnitude(B_IMF).The correlation of $\text{?}$ of the compressional Pc 3–4 waves at GOES 2 against B_IMF is higher than those of the Pc 3–4 pulsations at the globally coordinated ground stations, i.e., γ = 0.70 at GOES 2, and (0.36,0.60,0.66,0.54) at (COL, SGC, EWA, ONW), respectively. The standard deviation ($\text{σ}{}_{\mathrm{n}}\text{= ± Δ?}\text{mHz}$) of the observed frequencies from the form $\text{?}$ (mHz) = 6.0 × B_IMF (nT) is larger at the ground stations than at GOES 2, i.e., $\text{Δ? = ± 6.6}\text{mHz at}$GOES 2, and ±(13.9, 9.1, 10.7, 12.1) mHz at (COL, SGC, EWA, ONW), respectively. The correlations between the IMF magnitude B_IMF and Pc 3–4 frequencies at the low latitudes are higher than that at the high latitude on the ground, which can be interpreted by a “filtering action” of the magnetosphere for daytime Pc 3–4 magnetic pulsations. The scatter plots of pulsation frequency $\text{?}$ against the IMF magnitude B_IMF for the compressional Pc 3–4 waves at GOES 2 are restricted within the forms $\text{? = 4.5 × B}{}_{\mathrm{<mtext>IMF</mtext>}}\text{and}\text{? = 7.5 × B}{}_{\mathrm{<mtext>IMF</mtext>}}$. The frequency distribution is in excellent agreement with the speculation ($\text{<ω}{}_{\mathrm{sc}}\text{Ω}{}_{\mathrm{i}}\text{= 0.3 ～ 0.5}$) of the spacecraft frame frequency of the magnetosonic right-hand waves excited by the anomalous ion cyclotron resonance with reflected ion beams with V₆ = 650 ～ 1150 km s^?1 in the solar wind frame observed by the ISEE satellite in the Earth's foreshock. These observational results suggest that the magnetosonic right-handed waves excited by the reflected ion beams in the Earth's foreshock are convected through the magnetosheath to the magnetopause, transmitted into the magnetosphere without significant changes in spectra, and then couple with various HM waves in the Pc 3–4 frequency range at various locations in the magnetosphere.     

Pitch angle dependence of the charge-exchange lifetime of ring current ions

Previous work has parameterized the pitch angle dependence of the charge-exchange lifetime τ of ring current ions in terms of γ, the power of the cosine of the mirror latitude λ_m of the particles, such that $\text{τ(λ}{}_{\mathrm{m}}\text{)}\text{τ(0) ≌}\text{cos}{}^{\mathrm{\gamma }}\text{λ}{}_{\mathrm{m}}$ at given L. Using the atomic hydrogen density model of Johnson and Fish, previous authors have suggested values of γ = 5 or 6. We here evaluate γ as a function of λ_m and L using the more recent Chamberlain density models, and show that γ = 3?4 is more appropriate over most of the pitch angle and L range. Consequently, ion distributions in the ring current decay phase are expected to become rather less anisotropic in pitch angle due to chargeexchange than previously believed. We have also investigated the use of several other simple approximate analytic forms for $\text{τ(λ}{}_{\mathrm{m}}\text{)}\text{τ(0)}$, one of which gives far better agreement with the numerical results than the cos^γ λ_m, variation, and should hence be used in future studies.     

Localized auroral disturbance in the morning sector of topside ionosphere as a standing electromagnetic wave

An intense, localized auroral disturbance observed by Intercosmos-Bulgaria-1300 satellite in the morning sector at the altitude 850 km is analyzed in detail. The disturbance is characterized by strong “jumps” of electric and magnetic fields reaching ～ 80 mV/m and ～ 100 nT, fluctuations of ion density (Δn/n ～ 70%) and bursts of downward and upward energetic electron fluxes. Electric and magnetic disturbances display a distinct spatial-temporal relationship typical for the standing quasi-monochromatic wave ($\text{? ～ 1}\text{Hz}\text{, λ}{}_{\mathrm{x}}\text{～ 10}\text{km}$). The ratio of amplitudes of electric and magnetic fluctuations is equal to Alfvén velocity (ΔE/ΔB ～ v_A/c). However, a strong parallel component of the electric field (～ 30 mV/m) and large ion density fluctuations indicate significant changes of plasma properties (the effects of anomalous resistivity are possible).