摘要:

Two barium plasma injection experiments were carried out during magnetically active periods in conjunction with the Skylab 3 mission. The high‐explosive shaped charges were launched from Poker Flat near dawn on November 27 and December 4, 1973, UT. In both cases theAEindex was near 400 γ, and extensive pulsating auroras covered the sky. The first experiment, Skylab Alpha, occurred in the waning phase of a 1000‐γ substorm, and the second, Skylab Beta, occurred in the expansive phase of an 800‐γ substorm. In both, the convection was generally magnetically eastward, with 100‐km‐level electric fields near 40 mV/m. However, in the Alpha experiment the observed orientation of the barium flux tube fitted with theoretical field lines having no parallel current, but the Beta flux tube orientation indicated a substantial upward parallel sheet current. The Skylab Alpha experiment was observed and photographed by the crew of Skylab

ISSN:0148-0227    

DOI:10.1029/JA081i025p04487

年代:1976

数据来源: WILEY

摘要:

Television observations of a barium plasma flux tube extending from near 4500 km to near 10,000 km during a magnetic substorm and dawn sector auroral display indicated several interesting anomalous events. Beyond 5500 km there was a rapid increase in brightness accompanied by flux tube splitting and diffusion, leaving behind a truncated single flux tube. From the orientation of the flux tube compared with theoretical field models the presence of a substantial field‐aligned current sheet is deduced. A suggested explanation of these phenomena is given in terms of a plasma potential double laye

ISSN:0148-0227    

DOI:10.1029/JA081i025p04495

年代:1976

数据来源: WILEY

摘要:

The dispersion relation of waves in a cold magnetoplasma can be given in the form ∑ı=0pAi(k)ωı≡ 0, where ω is the frequency and the coefficientsAıare functions of the wave vector k. The group velocity Vgcan be expressed as Vg= −∑i=0p(∂Ai/∂k)ωı/∑i=0piAiωı−1. This equation is used for numerical studies of the slow and fast mode propagation in a one‐ion plasma. The slow mode is always guided by the magnetostatic field B0, whereas the fast mode is guided only for frequencies in the ‘whistler band.’ The ‘nose frequency’ for the whistlers decreases a

ISSN:0148-0227    

DOI:10.1029/JA081i025p04503

年代:1976

数据来源: WILEY

摘要:

The average solar wind velocity and the level of geomagnetic activity (Kp) following central meridian passage of coronal weak and bright features identified from Oso 7 isophotograms of Fe XV (284 Å) are determined by the method of superposed epochs. Results are consistent with the concept that bright regions possess magnetic fields of closed configuration, thereby reducing particle escape, while coronal holes possess open magnetic field lines favorable to particle escape or enhanced outflow of the solar wind. Coronal holes are identified with Bartels'Mregions not only statistically but by linking specific long‐lived holes with individual sequences of geomagnetic storms. In the study of bright regions a subdivision by brightness temperature (Tb) of associated 9.1‐cm radiation was found to be significant, with the regions of higherTbhaving a stronger inhibiting power on the outflow of the solar wind when they were located in the solar hemisphere on the same side of the solar equator as the earth. Regions of highestTbmost strongly depress the outflow of solar wind but are also the most likely to produce flare‐associated great

ISSN:0148-0227    

DOI:10.1029/JA081i025p04508

年代:1976

数据来源: WILEY

摘要:

Physical properties of electron variations of periods in the range 2–12 min detected in the afternoon magnetosphere at synchronous altitudes by the University of Minnesota electron spectrometer on the ATS‐1 satellite are presented. We find that in the energy interval 50 keV to 1 MeV most of the electron variations are correlated with the intensity of the local magnetic field. This correlation exists down to a time scale of a few minutes. The pitch angle analysis shows that the enhancement of fluxes occurs primarily at large pitch angles. These characteristics can be accounted for by adiabatic causes. When it is assumed that the perturbed magnetic field is time dependent but homogenous in space along the dipole direction, an expression for the change of particle fluxes in the equatorial plane is derived in terms of measurable quantities. We show here that the derived expression agrees well with observed characteristics of trapped electron fluxes measured by the University of Minnesota electron spectrometer on ATS‐1. In particular, the quasi‐periodic modulation characteristics observed here are satisfactorily ex

ISSN:0148-0227    

DOI:10.1029/JA081i025p04517

年代:1976

数据来源: WILEY

摘要:

In the formulation of steady hydromagnetic flows of a viscous conducting fluid, continuous solutions in similarity form are obtained which exhibit the topology of field line reconnection without the inclusion of discontinuity fronts. The properties of the flow support the assertion that magnetic merging can be mainly controlled by distant boundary conditions.

ISSN:0148-0227    

DOI:10.1029/JA081i025p04524

年代:1976

数据来源: WILEY

摘要:

We have computed the path‐integrated gain of parallel propagating whistlers driven unstable by an anisotropic distribution of relativistic electrons in the stable trapping region of Jupiter's inner magnetosphere. The requirement that a gain of threeefoldings of power balance the power lost by imperfect reflection along the flux tube sets a stably trapped flux of electronsJ* = 4 × 1010L−4cm−2s−1, which is close to the nonrelativistic result. Comparison with measurements shows that observed fluxes are near the stably trapped limit, which suggests that whistler wave intensities may be high enough to cause significant diffusion of electrons accounting for the observed reduction of phase space densities. A crude estimate of fluctuation intensity ofIB= 1.5 × 10−18(Ωce/ω)²Lα−2W m−2Hz−1as a lower limit for a diffusion coefficient mode

ISSN:0148-0227    

DOI:10.1029/JA081i025p04531

年代:1976

数据来源: WILEY

摘要:

A comparison is made of magnetohydrodynamic waves observed near the equator on Explorer 45 and at an array of ground stations in the northern hemisphere and at their conjugate station at Siple, Antarctica. The data comparisons strongly support the notion that the observed waves can be considered odd mode standing waves in the magnetosphere. This conclusion has important implications for the interpretation of single‐point satellite and/or ground measurements of ULF plasma wave phenomena in the magnetosphere. Further, the data comparisons strongly suggest that the overall ULF (∼5–30 mHz) power levels are quite similar in the magnetosphere and on the ground, at least during the intervals st

ISSN:0148-0227    

DOI:10.1029/JA081i025p04537

年代:1976

数据来源: WILEY

摘要:

The annual variation of magnetic activity and its variation with universal time are analyzed separately for days sorted according to the polarity of the interplanetary magnetic field (IMF). A coherent interpretation of the observed effects is obtained (1) by taking into account the variations of the southward component of IMF in GSM (geocentric solar magnetospheric) coordinates, as was suggested by Russell and McPherron (1973) (the effect expected from this mechanism is calculated and compared to the observed ones), and (2) in the case ofAm, by taking into account the annual and diurnal variations of the angle between the dipole axis and the earth‐sun lin

ISSN:0148-0227    

DOI:10.1029/JA081i025p04546

年代:1976

数据来源: WILEY

摘要:

The radial diffusion equation with synchrotron losses is solved by the Laplace transform method for near equatorially mirroring relativistic electrons. The evolution of a power law distribution function is found, and the characteristics of synchrotron burn‐off are stated in terms of explicit parameters for an arbitrary diffusion coefficient of the formDLL=D0Lα. The peaking of the 10.4‐cm volume emissivity from Jupiter atL≃ 1.8 provides an estimateD0≃ 9 × 10−11s−1in the radiation belts; this value is suggested as the appropriate modification for an equatorial field strength of 4.2 G of the Birmingham et al. (1974) result. Nonsynchrotron losses are included phenomenologically, and from the phase space densities reported by McIlwain and Fillius (1975) the particle lifetime is estimated as τ ∼ 6 × 108L2−αs. Asymptotic forms for the distribution in the strong synchrotron loss

ISSN:0148-0227    

DOI:10.1029/JA081i025p04553

年代:1976

数据来源: WILEY