摘要:

The properties of minor ions in the low solar corona are studied on the basis of a quasi‐hydrostatic equilibrium model suitably modified to account for the combined effects of Coulomb friction and Alfven wave acceleration in dragging minor ions out of the corona against the binding solar gravitational force. The analysis therefore generalizes the work of Hollweg (1981) to include the effect of waves which become important in the upper corona and the results, which must be treated with some caution, indicate that provided the proton flux is sufficiently large, the ions are evicted from the corona into the wind at the same speed as the protons with relative abundances which reflect their flux relative to protons in the low coron

ISSN:0148-0227    

DOI:10.1029/JA092iA01p00001

年代:1987

数据来源: WILEY

摘要:

We present correlated particle and magnetic field measurements by the ISEE 3 spacecraft for the loop structure behind the interplanetary traveling shock event of November 12, 1978. Following the passage of the turbulent shock region, we observe strong bidirectional streaming of low‐energy protons for approximately 6 hours, corresponding to a loop thickness of about 0.07 AU. This region is also characterized by a low relative variance of the magnetic field, a depressed proton intensity, and a reduction in the magnetic power spectral density. Using quasi‐linear theory applied to a slab model, we derive a value of 3 AU for the mean free path during the passage of the closed loop. We infer from this observation that the proton régime associated with the loop structure is experiencing scatter‐free transport and that either the length of the loop is approximately 3 AU between the sun and the earth or else the protons are being reflected at both ends of a smalle

ISSN:0148-0227    

DOI:10.1029/JA092iA01p00006

年代:1987

数据来源: WILEY

摘要:

The Pioneer Venus Orbiter measurements of the plasma and magnetic environment of the near tail of Venus show that the ionosphere becomes increasingly filamentary with increasing altitude, apparently forming cometlike tail rays that extend several thousand kilometers behind the planet. We call this region the ionotail of Venus. The tail rays are envisioned as plumes of high‐beta plasma of ionospheric origin that are surrounded by regions of low‐density, low‐beta plasma. The ionotail appears to be in quasi‐equilibrium, with the plasma pressure in the rays approximately balanced by the magnetic pressure of the region surrounding the rays. The magnetic field in this region is approximately sunaligned as we assume are the tail rays. Magnetic field reversals observed in the tail ray boundaries suggest the presence of strong current sheets there. Unlike the lower ionosphere whose major ion is thermal O+, a detailed study of tail ray plasma between 2000 and 2500 km altitude shows that the major ions are superthermal O+, with energies in the range of 9‐16 eV. The electrons are much cooler, with energies of about 1 eV. A minor, more energetic ion component, having energies exceeding 40 eV is also observed within the tail rays and occasionally between the rays as well. These Pioneer Venus Orbiter measurements reveal an ionotail that is highly dynamic, a region in which solar wind induced magnetic fields configure the ionospheric structures and accelerate the ions beyond the planetary escape velocity. We estimate a total planetary O+escape rate of 5 × 1025ions/s, and we infer an H+escape rate of about half that value, about a factor of 2 below the hydrogen escape rate due to H+charge exchange with the hydrogen exospher

ISSN:0148-0227    

DOI:10.1029/JA092iA01p00015

年代:1987

数据来源: WILEY

摘要:

Because of a lack of readily usable information pertaining to the polarization of the Voyager 1 and 2 high‐frequency band data, a technique has been developed that aids the identification of Io‐dependent decametric radiation originating from the southern hemisphere of Jupiter. This technique compares the results of model ray tracing calculations with the Planetary Radio Astronomy (PRA) observations. A large portion of the Voyager 1 and 2 PRA observations are sorted into bins (±3° wide) centered on a specific Io central meridian longitude. When the data are plotted (as a frequency‐longitude spectrogram) in this coordinate system, Io‐dependent features can be identified and compared with ray tracing calculations performed in a model Jovian magnetosphere where it is assumed that the decametric emissions are generated in theRXmode from low‐altitude source regions along the instantaneous Io flux tube. Two different magnetic field models are used, and the results are contrasted. In this study, we compare the observations for constant sub‐Io longitudes of 260° and 300° with the corresponding model ray tracings. The results permit the identification of decametric spectral features from source locations in both the northern and southern hemispheres: (1) The emission traditionally designated “Io‐B” originates at the Io flux tube footprint in the northern hemisphere when the sub‐Io system III longitude λIIIis equal to 260°. (2) The component traditionally designated “Io‐C” is a combination of emissions emanating from the Io flux tube footprints in both northern and southern hemispheres when Io is located at longitudes 260° and 300°. (3) The traditional “non‐Io‐A” emission is, in fact, Io related at both Io configurations studied. When Io is located at λIII= 260°, this emission originates in the southern hemisphere flux tube footprint. When Io is at λIII= 300°, this component (“non‐Io‐A”) originates fr

ISSN:0148-0227    

DOI:10.1029/JA092iA01p00027

年代:1987

数据来源: WILEY

摘要:

The observations by the ion composition instrument (ICI) on the ICE spacecraft made during the encounter with comet P/Giacobini‐Zinner (Ogilvie et al., 1986) are discussed in detail. Solar wind4He++kinetic temperatures, densities, and velocities before, during, and after the encounter are presented. These data combined with4He++velocity distributions provide evidence for the existence of a thick diffuse shock. Relative abundances of water group ions and CO+are derived along with an estimate of the abundance of an ion withM/Q= 24 ± 1 amu/e. The ICI data are compared with electron data from two other experiments (Bame et al., 1986; Meyer‐Vernet et al., 1986) and found to be in reasonable agreement in the region outside the tail. Spectroscopic data for several neutral and ionic species are compared with the ICI results for the water group ions and CO+. The spectroscopic data are also used to eliminate Mg+and CN+as candidates for theM/Q= 24 peak. The two most likely candidates are C2+and Na+, but neither photoionization of parent neutrals nor sputtering from dust grains is sufficient to explain the observed abundance relative to

ISSN:0148-0227    

DOI:10.1029/JA092iA01p00039

年代:1987

数据来源: WILEY

摘要:

Analysis of previously reported observations of the solar wind‐barium interaction associated with the AMPTE artificial cornet release of December 27, 1984, is presented. On the basis of these results we argue that the solar wind couples momentum (and energy) to the barium ions through both laminar and turbulent processes. The laminar forces acting on the particles are the laminar electric and magnetic fields; the turbulent forces are associated with the intense electrostatic wave activity. This wave activity is shown to be caused by a cross‐field solar wind proton‐barium ion streaming instability. The observed wave frequencies and saturated amplitudes are consistent with our theoretical ana

ISSN:0148-0227    

DOI:10.1029/JA092iA01p00047

年代:1987

数据来源: WILEY

摘要:

Propagation of a quasi‐neutral plasma beam or cloud across a magnetic field is considered for the case where the transverse dimension of the beam or cloud is sufficiently small compared to ion gyroradii. This situation commonly arises for active experiments in near‐earth space. Two mechanisms are presented for transverse deflection of a beam or cloud in the ‐v0×B0direction wherev0is the velocity relative to the ambient medium. In the first, asymmetric escape of ions from an electrically polarized beam or cloud causes transverse deflection by means of a rocket effect. The transverse deflection distance is estimated to be a few times the initial transverse dimension of the beam or cloud. Dissipation occurs within a few times the thermal ion transverse crossing time. In the second mechanism, asymmetric charging results from localized accumulation of incident ions from the ambient medium. This excess positive charge distorts electric equipotentials and drives electron Hall currents that maintain an asymmetric compressed magnetic field region. The asymmetry of the magnetic stress contributes to transverse deflection with the same sign as the rocket effect. The asymmetric magnetic field also focuses incident ions to yield the localized charge accumulation. These ideas are qualitatively consistent with observations of the Active Magnetospheric Particle Tracer Explorers artificial comet re

ISSN:0148-0227    

DOI:10.1029/JA092iA01p00055

年代:1987

数据来源: WILEY

摘要:

This paper presents a representative example of an enhancement in energetic ion flux associated with the International Sun‐Earth Explorer 3 (ISEE 3) spacecraft's encounter with a traveling compression region (TCR). Data from the energetic particle anisotropy spectrometer (EPAS) instrument on ISEE 3 are studied, along with magnetic field data from the vector helium magnetometer. It is concluded that the ion enhancements seen are spatial in nature, thus supporting the idea that TCRs are the lobe signatures of plasmoids moving along the magnetotail, away from eart

ISSN:0148-0227    

DOI:10.1029/JA092iA01p00064

年代:1987

数据来源: WILEY

摘要:

Examination of many individual event periods in the ISEE 3 deep tail data set collected in 1982–1983 has suggested that magnetospheric substorms produce a characteristic pattern of effects in the distant magnetotail. ISEE 3 data are appropriate for the study of these effects, since the spacecraft remained relatively fixed within the nominal tail location for long periods. Using auroral electrojet indices (AEandAL) and geostationary orbit particle data to time substorm onsets at earth, we have performed superposed epoch analyses of ISEE 3 and near‐earth data prior to and following substorm expansive phase onsets. Individual events illustrate the wide range of variations possible throughout the magnetosphere, while epoch‐averaged results illustrate the general properties of the deep tail pattern of response to global substorm‐induced dynamical effects. During the growth, or tail energy storage, phase of substorms the distant magnetotail appears to grow diametrically in size, often by many earth radii. Subsequently, about 20–40 min after the substorm expansive phase onset at earth the distant tail undergoes a repeatable sequence of plasma, field, and energetic particle variations as large‐scale plasmoids move rapidly down the tail following their disconnection from the near‐earth

ISSN:0148-0227    

DOI:10.1029/JA092iA01p00071

年代:1987

数据来源: WILEY

摘要:

A detailed study of the plasma parameters and magnetic field measured using instrumentation aboard ISEE 2 during the recovery phase of a substorm on April 24, 1979, is presented. The purpose of this study was to determine the nature and structure of the lobe‐plasma sheet boundary layer. The analysis shows that the lobeward edge of the boundary is consistent with a freestanding slow mode shock. This shock is followed by a slow compression wave containing a trailing ion cyclotron wave which also stands in the flow. Measurement of the cross‐tail current in the shock and the current system within the wave gives a shock thickness and wavelength comparable to but larger than both the upstream ion inertial length and the downstream proton gyroradius. Equality of the shock thickness with the standing ion cyclotron wavelength suggests that the steepness of the front is limited by dispersion rather than current‐driven anomalous resist

ISSN:0148-0227    

DOI:10.1029/JA092iA01p00083

年代:1987

数据来源: WILEY