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1.
The launch of the P78-2 (SCATHA) satellite in January 1979 has provided a new opportunity to study the energetic ion composition in the high altitude equatorial regions of the earth's magnetosphere. In particular detailed pitch angle distributions were obtained as a function of ion species and energy. The energies measured range from ～ 90 to 250 keV/nucleon for Z ? 2. Data are presented which were acquired in late March and early April 1979. The relative abundance of He and CNO nuclei are found to be ～ 10?2 and 5 × 10?4 respectively at L ? 5.5. Only an upper limit on the relative abundance of Fe group nuclei of < 3 × 10?7 was obtained. The angular distributions of the heavy ions was found to be very steep for BB0 < 1.5 and then to flatten markedly.  相似文献   

2.
The plasmapause position is determined by the innermost equipotential surface which is tangent to the ‘Roche-Limit’ surface of the ionospheric plasma filling the magnetosphere. When the thermal particles corotate with the Earth's angular velocity, the ‘Roche-Limit’ equatorial distance is Lc=5.78 [RE]. When the angular convection velocity is evaluated from the quiet time electric field distribution E3 of McIIwain (1972), Lc depends on the local time. Its minimum value is then LC=4.5Near 2400 LT, and the plasmapause shape and position satisfactorily fit the observations. The diffusive equilibrium dnesity distribution appropriated inside the plasmasphere, becomes convectively unstable beyond L = Lc, where the collisions type of model satisfactorily represents the observations. In the intermediate region between the plasmapause and the last closed magnetic field line, contimues ionization fluxes are expected to flow out of the midlatitude ionosphere  相似文献   

3.
Energetic ion (E ? 290 keV) and electron (Ee ? 220 keV) burst intensities were simultaneously monitored at various regions of the plasma sheet and magnetosheath by the CPME JHU/APL instruments on board the IMP-7 and 8 s/c during an extended period from day 250, 1975 to day 250, 1976 when the two spacecraft were closely trailing each other in crossing the geomagnetotail. The energy spectra of the energetic particle populations of different regions in the magnetotail were also computed and monitored simultaneously at the positions of the two spacecraft. The results indicate that the energetic particle intensities are higher and the energy spectra in general considerably softer inside the plasma sheet than the adjacent magnetosheath. The spectral index γ of a power law fit in the computed energy spectrum inside the plasma sheet occasionally exceeds γ > 10 for the ions and γ > 6 for the electrons. Furthermore simultaneous monitoring of particle intensities in the vicinity of the neutral sheet and the high latitude plasma sheet shows higher intensities in the former region. The observations suggest that the energetic particles escape to the magnetosheath from their source inside the plasma sheet by a rigidity dependent process. A dawn-dusk asymmetry in the particle acceleration and escape processes is implied in the observations and discussed in detail.  相似文献   

4.
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5.
During August 1972, Explorer 45 orbiting near the equatorial plane with an apogee of ～5.2 Re traversed magnetic field lines in close proximity to those simultaneously traversed by the topside ionospheric satellite ISIS 2 near dusk in the L range 2.0–5.4. The locations of the Explorer 45 plasmapause crossings (determined by the saturation of the d.c. electric field double probe) during this month were compared to the latitudinal decreases of the H+ density observed on ISIS 2 (by the magnetic ion mass spectrometer) near the same magnetic field lines. The equatorially determined plasmapause field lines typically passed through or poleward of the minimum of the ionospheric light ion trough, with coincident satellite passes occurring for which the L separation between the plasmapause and trough field lines was between 1 and 2. Hence, the abruptly decreasing H+ density on the low latitude side of the ionospheric trough is not a near earth signature of the equatorial plasmapause. Vertical flows of the H+ ions in the light ion trough as detected by the magnetic ion mass spectrometer on ISIS were directed upward with velocities between 1 and 2 km s?1 near dusk on these passes. These velocities decreased to lower values on the low latitude side of the H+ trough but did not show any noticeable change across the field lines corresponding to the magnetospheric plasmapause. The existence of upward accelerated H+ flows to possibly supersonic speeds during the refilling of magnetic flux tubes in the outer plasmasphere could produce an equatorial plasmapause whose field lines map into the ionosphere at latitudes which are poleward of the H+ density decrease.  相似文献   

6.
We report observations of MeV heavy ions made with Explorer 45 in the earth's radiation belts during the 7-month period June–December 1972 when four major magnetic storms occurred. Significant fluxes of ions heavier than fluorine (i.e. with nuclear charge Z ? 9) were observed stably trapped in the interior of the radiation belts at L ～ 2–4. These energetic very heavy ions, were found to appear suddenly during the August 1972 magnetic storm period and their fluxes decayed during the following months on time scales typically several tens of days. Simultaneously, strong increases in the geomagnetically trapped MeV helium and CNO ion fluxes were observed, and the post-injection flux decay of these ions was found to be slower than that of the Z ? 9 ions. The relative enhancements in trapped fluxes during the storm increased with increasing ion mass and/or increasing ion energy.  相似文献   

7.
This paper discusses the experimental results on electron precipitation in a diffuse aurora obtained by a sounding rocket launched from ANDENES (L ～ 6·2) on 3 November 1968. A considerable increase in the intensity of low energy electrons, Ee ? 5 keV, followed a large precipitation of more energetic electrons Ee ? 5 keV. From the observation of angular distributions and an estimate of the diffusion coefficient (Dα ? 10?3 (sec)?2), it is suggested that this higher energy precipitation is induced by gyroresonant interactions of magnetospheric electrons with radiation in the whistler mode. The lower energy precipitation separated in time and/or space, shows quasi-periodic modulations in the 5–15 sec range with periods close to the bounce period. It is suggested that this precipitation is the result of bounce-resonance interactions with electrostatic waves in the equatorial plane. Finally, from a comparison between the experimental energy spectra and plasma sheet spectra it can be concluded that these electrons are injected from the plasma sheet during a substorm and are then diffused and precipitated by energy dependent mechanisms.  相似文献   

8.
Analytic treatments of a particle encountering a collisionless shock have commonly been based on the assumption that the shock surface is quasi-planar with length scales larger than the particle gyroradius. Within this framework, the particle distribution function width is supposed to be conserved in any shock reflection process. It is well known, however, that the thermal energy associated with backstreaming ions upstream of Earth's bow shock is significantly larger than the incident solar wind thermal energy. In a previous study, we found that non-thermal features of ions reflected quasi-adiabatically can be accounted for by considering the effect of small, normally distributed fluctuations of the shock normal over short temporal or spatial scales. The strong dependence of the particle acceleration on shock geometry leads to an increase in the temperature and to a non-thermal tail. Here, we conduct a similar analysis to investigate the effects of small, normally distributed fluctuations in the shock normal direction for specularly reflected ions. This later mechanism is considered of first importance in the dissipation process occurring at quasi-perpendicular shocks. We have derived the probability distribution functions f(v∥) and f(v⊥) of ions issued from a specular reflection of incident solar wind in the presence of normal direction fluctuations. These distributions deviate weakly from a Maxwellian, in agreement with the observations. In particular, a qualitative agreement with the ion thermal energy is obtained for fluctuations of the normal orientation in the 5-8° range about the nominal direction. Also, we have found that the shock θBn has a weak effect on the shape of the distribution. While, not a strong determinant of the reflected distribution characteristics, the dynamical shock structure at ion scales cannot be ignored when accounting for the shock-accelerated particle thermal energy.  相似文献   

9.
There is a magnetosonic waveguide under the arch of the plasmasphere. This channel, in the form of a ring with radius L～4, surrounds the Earth. It is shown that in this region of the magnetosphere the flute-like electromagnetic disturbances (k6 = 0) with frequencies ω = sωp can be excited by energetic protons, with non-monotonic dependence on transverse energy (??/?ε⊥ > 0). The interpretation of magnetic pulsations which have been observed in the equatorial vicinity of the plasmapause on the satellite OGO-3 in the frequency range ～102 cps (Russell et al., 1970) is given. In particular the origin of discrete structure of the observed spectra (narrow band spikes for a rather broad range of frequency) is discussed.  相似文献   

10.
Coordinated observations involving ion composition, thermal plasma, energetic particle, and ULF magnetic field data from GEOS 1 and 2 often reveal the presence of electromagnetic ion cyclotron and magnetosonic waves, which are distinguished by their respective polarization characteristics and frequency spectra. The ion cyclotron waves are identified by a magnetic field perturbation that lies in a plane perpendicular to the Earth's magnetic field B0 and propagate along B0. They are associated with the abundance of cold He+ in the presence of anisotropic pitch angle distributions of ions having energies E > 20 keV, and were observed at frequencies near the He+ gyrofrequency. The magnetosonic waves are characterized by a magnetic field perturbation parallel to B0 and thus seem to be propagating perpendicular to the Earth's magnetic field. They often occur at harmonics (not always including the fundamental) at the proton gyrofrequency and are associated with phase-space-density distributions that peak at energies E ～ 5–30 keV and at a pitch angle of 90°. Such a ring-like distribution is shown to excite instability in the magnetosonic mode near harmonics of the proton gyrofrequency. Magnetosonic waves are associated in other cases with sharp spatial gradients in energetic ion intensity. Such gradients are encountered in the early afternoon sector (as a consequence of the drift shell distortion caused by the convection electric field) and could likewise constitute a source of free energy for plasma instabilities.  相似文献   

11.
Using ion-electron fluid parameters derived from Cassini Plasma Spectrometer (CAPS) observations within Saturn's inner magnetosphere as presented in Sittler et al. [2006a. Cassini observations of Saturn's inner plasmasphere: Saturn orbit insertion results. Planet. Space Sci., 54, 1197-1210], one can estimate the ion total flux tube content, NIONL2, for protons, H+, and water group ions, W+, as a function of radial distance or dipole L shell. In Sittler et al. [2005. Preliminary results on Saturn's inner plasmasphere as observed by Cassini: comparison with Voyager. Geophys. Res. Lett. 32(14), L14S04), it was shown that protons and water group ions dominated the plasmasphere composition. Using the ion-electron fluid parameters as boundary condition for each L shell traversed by the Cassini spacecraft, we self-consistently solve for the ambipolar electric field and the ion distribution along each of those field lines. Temperature anisotropies from Voyager plasma observations are used with (T⊥/T∥)W+∼5 and (T⊥/T∥)H+∼2. The radio and plasma wave science (RPWS) electron density observations from previous publications are used to indirectly confirm usage of the above temperature anisotropies for water group ions and protons. In the case of electrons we assume they are isotropic due to their short scattering time scales. When the above is done, our calculation show NIONL2 for H+ and W+ peaking near Dione's L shell with values similar to that found from Voyager plasma observations. We are able to show that water molecules are the dominant source of ions within Saturn's inner magnetosphere. We estimate the ion production rate SION∼1027 ions/s as function of dipole L using NH+, NW+ and the time scale for ion loss due to radial transport τD and ion-electron recombination τREC. The ion production shows localized peaks near the L shells of Tethys, Dione and Rhea, but not Enceladus. We then estimate the neutral production rate, SW, from our ion production rate, SION, and the time scale for loss of neutrals by ionization, τION, and charge exchange, τCH. The estimated source rate for water molecules shows a pronounced peak near Enceladus’ L shell L∼4, with a value SW∼2×1028 mol/s.  相似文献   

12.
基于在^3He丰富事件中，高能^3He和重离子具有相似的幂律谱分布这一观测结果，通过数值求解Fokker-Planck方程，探讨经阿尔芬波湍动速后的离子分布随时间的演化特征。计算结果表明：加速源区的等离子体密度和阿尔芬波湍动能量密度对粒子能谱分布起主要作用，如果取加速源区等离子体密度n=(0.1-1)10^10cm^-3、磁场强度B=50-100Gs、湍动能量密度为0.4-2ergs cm^-3，则在1秒左右的时间内，湍动阿尔芬波能够将^3He和重离子加速到10MeV/nucleon量级，能谱指数为2.0-3.5。理论计算与观测结果基本一致。  相似文献   

13.
Omnidirectional intensities of electrons with energies Ee > 1·5 MeV detected by a low orbiting polar satellite (GRS-A/AZUR) in the outer radiation belt are examined during disturbed times including the main phase of a very strong geomagnetic storm on 8 March 1970. The particle intensity features are discussed in relationship with proposed magnetospheric processes. It is found that a superposition of the two following effects can explain the particle behavior in the trapping region:(A) Radial diffusion. After the southward turning of the interplanetary field an inward motion of both the energetic electron belt and the plasmapause took place. This effect was observed at L > 3 RE and we attribute it to enhanced magnetospheric electric field fluctuations. Later, a strong interplanetary shock impinged upon the magnetosphere which was related to the triggering of intense magnetospheric substorms; a further inward diffusion occurred at L ? 3 RE, accompanied by an inward movement of the electron slot. A rough estimation of the diffusion coefficient leads to a power spectrum of the electric field fluctuations which seems to be consistent with experimentally determined power spectra (Mozer, 1971).(B) Adiabatic response to ring current changes. Large energetic electron intensity decreases within the outer radiation belt are shown to be adiabatic changes due to ring current variations. The influence of the inflation of the magnetosphere due to the developing ring current is simultaneously observed by the decrease of the solar proton outoff (1·7-2·5 MeV).  相似文献   

14.
Chuan-Yi Tu 《Solar physics》1987,109(1):149-186
A new solar wind model has been developed by including in the model the Alfvénic fluctuation power spectrum equation proposed by Tu et al. (1984). The basic assumptions of the model are as follows: (1) for heliocentric distances r > 10 R ⊙, the radial variation of the power spectrum of Alfvénic fluctuations is controlled by the spectrum equation (1), (2) for heliocentric distances r < 10 R ⊙, the radial variation of the fluctuation amplitude is determined by the Alfvén wave WKB solution, (3) no energy cascades from the low-frequency boundary of the Alfvénic fluctuation power spectrum into the fluctuation frequency range, and the energy which cascades from the high-energy boundary of the spectrum into the higher frequency range is transported to heat of the solar wind flow. Some solutions of this model which, on one hand, describe the major properties of the Alfvénic fluctuations and the high-speed flow observed by Helios in the space range between 0.3–1 AU and, on the other hand, are consistent with the observational constraints at the coronal base have been obtained under the following conditions: (1) the spectrum index of the fluctuations is near to -1 for almost the whole frequency range at 10 R ⊙, (2) the particle flux density at 1 AU is not greater than 3 × 108 cm?2 s?1, (3) the solution is for spherically-symmetric flow geometry or the solution passes through the outermost of the three critical points of the rapidly diverging flow geometry with f max = 7. Some solutions passing through the innermost critical point of the rapidly diverging flow geometry with f max = 7 have been found, however, with too low pressure at the coronal base to compare with the observational constraints. Heat addition or other kind of momentum addition for r < 10 R ⊙ is required to modify this model to yield better agreement with observations. A cascade energy flux function which leads to Kolmogorov power law in the high-frequency range of Alfvénic fluctuations is presented in Appendix A. More detailed discussions about the characteristics, the boundary conditions and the solution of the spectrum equation (1) are given in Appendix B.  相似文献   

15.
Measured fractional abundances for stratospheric positive ions are reported for the first time. The measurements which were obtained from balloon-borne ion mass spectrometer experiments relied on recent simulation studies of electric field induced cluster ion dissociation conducted at our laboratory.The ion abundance data provide strong support for identifications of the observed ions as H+(H2O)n and Hx+xL(H2O)m proposed previously. Moreover, it is found that x most likely cannot be identified as NaOH or MgOH which implies that gaseous metal compounds do not exist in the middle stratosphere in significant abundances.Implications of the present findings for the composition and chemistry of stratospheric ions as well as for stratospheric aerosols are discussed.  相似文献   

16.
The dispersion relation for the near perpendicular propagation of the electromagnetic ion cyclotron wave, having a wavelength much larger than the ion Larmour radius rL and a frequency ω ≈ Ω+ (Ω+ is the ion cyclotron frequency), has been derived for a plasma consisting of a hot and a cold ion component. The hot ions and electrons have been described by loss-cone distribution functions; an ordering of the parameters was used to derive the cold ion contributions. Two modes, one with an increasing frequency and another with a constant frequency can propagate in the plasma. The two modes interact resulting in an instability of the former in the wavelength range k⊥r⊥ = 0.4?0.6 (for nC/nH = 0) and from k⊥rL = 0.5?0.8 (for nC/nH = 1.0) for a propagation angle of 70°. The instability of the mode is found to decrease with increasing cold ion densities and propagation angles.  相似文献   

17.
We present new and definitive results of Cassini plasma spectrometer (CAPS) data acquired during passage through Saturn's inner plasmasphere by the Cassini spacecraft during the approach phase of the Saturn orbit insertion period. This analysis extends the original analysis of Sittler et al. [2005. Preliminary results on Saturn's inner plasmasphere as observed by Cassini: comparison with Voyager. Geophys. Res. Lett. 32, L14S07, doi:10.1029/2005GL022653] to L∼10 along with also providing a more comprehensive study of the interrelationship of the various fluid parameters. Coincidence data are sub-divided into protons and water group ions. Our revised analysis uses an improved convergence algorithm which provides a more definitive and independent estimate of the spacecraft potential ΦSC for which we enforce the protons and water group ions to co-move with each other. This has allowed us to include spacecraft charging corrections to our fluid parameter estimations and allow accurate estimations of fluctuations in the fluid parameters for future correlative studies. In the appendix we describe the ion moments algorithm, and minor corrections introduced by not weighting the moments with sinθ term in Sittler et al. [2005] (Correction offset by revisions to instruments geometric factor). Estimates of the spacecraft potential and revised proton densities are presented. Our total ion densities are in close agreement with the electron densities reported by Moncuquet et al. [2005. Quasi-thermal noise spectroscopy in the inner magnetosphere of Saturn with Cassini/RPWS: electron temperatures and density. Geophys. Res. Lett. 32, L20S02, doi:10.1029/2005GL022508] who used upper hybrid resonance (UHR) emission lines observed by the radio and plasma wave science (RPWS) instrument. We show a positive correlation between proton temperature and water group ion temperature. The proton and thermal electron temperatures track each with both having a positive radial gradient. These results are consistent with pickup ion energization via Saturn's rotational electric field. We see evidence for an anti-correlation between radial flow velocity VR and azimuthal velocity Vφ, which is consistent with the magnetosphere tending to conserve angular momentum. Evidence for MHD waves is also present. We show clear evidence for outward transport of the plasma via flux tube interchange motions with the radial velocity of the flow showing positive radial gradient with functional dependence for 4<L<10 (i.e., if we assume to be diffusive transport then DLL∼D0L11 for fixed stochastic time step δt). Previous models with centrifugal transport have used DLL∼D0L3 dependence. The radial transport seems to begin at Enceladus’ L shell, L∼4, where we also see a minimum in the W+ ion temperature . For the first time, we are measuring the actual flux tube interchange motions in the magnetosphere and how it varies with radial distance. These observations can be used as a constraint with regard to future transport models for Saturn's magnetosphere. Finally, we evaluate the thermodynamic properties of the plasma, which are all consistent with the pickup process being the dominant energy source for the plasma.  相似文献   

18.
Observations of the equatorial lunar sodium emission are examined to quantify the effect of precipitating ions on source rates for the Moon’s exospheric volatile species. Using a model of exospheric sodium transport under lunar gravity forces, the measured emission intensity is normalized to a constant lunar phase angle to minimize the effect of different viewing geometries. Daily averages of the solar Lyman α flux and ion flux are used as the input variables for photon-stimulated desorption (PSD) and ion sputtering, respectively, while impact vaporization due to the micrometeoritic influx is assumed constant. Additionally, a proxy term proportional to both the Lyman α and to the ion flux is introduced to assess the importance of ion-enhanced diffusion and/or chemical sputtering. The combination of particle transport and constrained regression models demonstrates that, assuming sputtering yields that are typical of protons incident on lunar soils, the primary effect of ion impact on the surface of the Moon is not direct sputtering but rather an enhancement of the PSD efficiency. It is inferred that the ion-induced effects must double the PSD efficiency for flux typical of the solar wind at 1 AU. The enhancement in relative efficiency of PSD due to the bombardment of the lunar surface by the plasma sheet ions during passages through the Earth’s magnetotail is shown to be approximately two times higher than when it is due to solar wind ions. This leads to the conclusion that the priming of the surface is more efficiently carried out by the energetic plasma sheet ions.  相似文献   

19.
SAR arcs were observed from Southern Africa on 17/18 December 1971, 4/5 August 1972 and 1/2 April 1973 with the equatorwards edge at L = 1.8. Simultaneous with the latter event the intertropical arc was observed at an equatorial station. There was no apparent relationship. Calculations show that while the entire observed inter-tropical emission results from dissociative recombination of O2+ this process may, in some cases, account for only a fraction of a percent of the observed SAR arc emission. More than five years of geomagnetic storm data shows that Southern African SAR arcs are unlikely unless disturbances exceed 150 γ. For very severe 300 γ disturbances main phase SAR arcs may be observed. Estimates of the fraction of storm energy used in production of the present arcs indicate they are inefficient sinks for magnetic storms.  相似文献   

20.
Bob Abel  Richard M. Thorne 《Icarus》2003,166(2):311-319
Longitudinal variations of energetic charged particle precipitation into the jovian sub-auroral atmosphere are modeled based on weak diffusion scattering and variations in the local loss-cone size associated with asymmetries in the VIP-4 magnetic field model. Our scattering model solutions suggest that low latitude observations of enhanced H3+ and X-ray emissions are at least partially due to precipitating energetic particles. The correlation between model results and observations is best in the northern hemisphere at low L (1.5), where the surface magnetic field variation is largest and observations have the highest resolution. Weaker correlations in the southern hemisphere and at higher latitudes, particularly for H3+ emissions, are likely due to the presence of other energy sources, lack of resolution in the observations and limitations in the sub-auroral surface magnetic field model.  相似文献   

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