摘要:

The evolution of U‐shaped double layers in discrete auroral arcs occurs much faster than the global current in the arc flux tube can be redistributed. For asymptotic stality of the arc on MHD time scales, this implies that local transport mechanisms are required to charge the nearly field‐aligned flanks of the equipotential structure over an extended region along the magnetic field. The diversion of the uniform upstream current provides a constraint which limits the double‐layer pote

ISSN:0094-8276    

DOI:10.1029/GL013i009p00889

年代:1986

数据来源: WILEY

摘要:

The effect of the convection electric field in accelerating ions that escape from the polar ionosphere is investigated. It is shown that at high altitudes the velocity component of the ions along the magnetic field may be increased by more than an order of magnitude. The highest velocities are acquired by ions that escape from the region of the ionosphere that is connected along magnetic field lines to the dayside cusps. During disturbed times, ions from that region intercept the center plane of the magnetotail in one to two hours at radial distances exceeding about 6 RE. Investigation of the resulting O+properties in the center plane, viz., their locations, number densities, and energies, indicates that the polar ionosphere near the cusps is the principal source of the O+observed in the plasma sheet. Moreover, a study of the ion motion at quiet and disturbed times indicates that the increase of O+in the plasma sheet with increasing AE values [Lennartsson and Shelley, 1986] is due mainly to an increase in the source of O+rather than alteration of its transport path.

ISSN:0094-8276    

DOI:10.1029/GL013i009p00893

年代:1986

数据来源: WILEY

摘要:

Formation of large scale and large amplitude electrostatic potential along magnetic field lines due to a high‐speed plasma flow in auroral plasma is discussed. It is shown that the potential profile which is consistent with observations, i.e., which increases very slowly near the plasmasheet and abruptly near the topside ionosphere, can be obtained by introducing a population of electrons which are trapped between the magnetic mirror and the electrostatic potential

ISSN:0094-8276    

DOI:10.1029/GL013i009p00897

年代:1986

数据来源: WILEY

摘要:

We report observations of preferential heating of the ionospheric majority ion species O+. The heating took the form of a hot (few electron volts) tail in the upgoing thermal O+. No such hot tail was observed in the light ion distributions. An event observed at 700‐800 km altitude was highly anisotropic with a much hotter tail transverse to the local magnetic field. A series of events observed at 250‐375 km were more nearly isotropic with respect to the local magnetic field. Broadband plasma wave emission near the lower hybrid resonance was observed in conjunction with the high altitude event. The low altitude events were tightly correlated with auroral electron precipitation, but broadband lower hybrid emission was much reduced. The observed hot tail formation is sufficient to produce significant O+ion transport to higher altitude auroral acceleration regi

ISSN:0094-8276    

DOI:10.1029/GL013i009p00901

年代:1986

数据来源: WILEY

摘要:

Spectrograms of ULF waves in the 0 to 80 mHz frequency range have been prepared from magnetic field data obtained by the elliptically orbiting AMPTE/CCE satellite (with an apogee of approximately 8.8 Re. The most prominent feature of these spectrograms (which cover a full 15.6 hour orbit) is the presence of harmonically structured, azimuthally polarized pulsations in the outer magnetosphere during daytime hours. The frequencies of these pulsations decrease with increasing radial distance from the earth, indicating that they represent independent resonances of local magnetic flux tubes. The latitudinal structure of these harmonic pulsations, observed as AMPTE/CCE traveled to ± 16° magnetic latitude, is consistent with accepted field line resonance models. Correlations with IMP 8 satellite data confirm a close connection between appearance of these harmonic pulsations in the dayside magnetosphere and interplanetary magnetic field conditions favorable for the generation of upstream waves. Although we also observe pulsations associated with ring current injections, the monochromatic pulsations predicted by some theoretical models are extremely rare in the dayside AMPTE/CCE data se

ISSN:0094-8276    

DOI:10.1029/GL013i009p00905

年代:1986

数据来源: WILEY

摘要:

Observations are presented of short‐lived, highly structured bursts of rapid plasma flow observed with the EISCAT radar in the high latitude dayside ionosphere. It is shown that the properties of the bursts are consistent with ionospheric perturbations caused by impulsive, localized reconnection at the Earth's magnetopause, i.e. by flux transfer event

ISSN:0094-8276    

DOI:10.1029/GL013i009p00909

年代:1986

数据来源: WILEY

摘要:

Solar wind data from three‐station IPS (interplanetary scintillation) observations are analyzed in order to study solar wind features during the CDAW‐6 intervals (March 22 and March 31 ‐ April 1, 1979). The empirical model of the interplanetary shock wave disturbance relevant to the ssc of 0826 UT, March 22, 1979 is determined. The layer of enhanced density fluctuations is identified to have been the shocked plasma with highly fluctuating interplanetary magnetic

ISSN:0094-8276    

DOI:10.1029/GL013i009p00913

年代:1986

数据来源: WILEY

摘要:

The location of the Venus bow shock is found to be sensitive to both the angle of the interplanetary magnetic field (IMF) to the solar wind flow and the phase of the solar cycle. We attribute the former dependence to the effect of planetary ion pickup by the magnetosheath convection electric field analogous to cometary ion pickup by the solar wind electric field. We attribute the latter dependence to the solar‐cycle variation in the density of exospheric neutrals in the magnetosheath analogous to the cometary response to distance from the sun. We also find both a north‐south and a pole‐equator asymmetry in the location of the bow shock, controlled by the direction of the IMF in the plane perpendicular to the solar wind flow, for those data where the perpendicular component dominates. These observations suggest how the comet‐solar wind interaction should also respond to the combination of the IMF orientation and the intensity of the ionizing solar ra

ISSN:0094-8276    

DOI:10.1029/GL013i009p00917

年代:1986

数据来源: WILEY

摘要:

Basic uncertainties about the nature of the comet‐solar wind interaction have existed for decades, and even gross features of the interaction phenomena were poorly understood on theoretical grounds alone. The first discussions of measurements from the encounter of ICE (International Cometary Explorer) with Comet Giacobini‐Zinner did not provide immediate clarification of these issues. Here we analyze the nature of the interaction by examining the detailed evolution of the plasma wave spectra across the interaction region. It is shown that the cometary spectra are very similar to those detected at certain classes of interplanetary shocks and terrestrial bow sho

ISSN:0094-8276    

DOI:10.1029/GL013i009p00921

年代:1986

数据来源: WILEY

摘要:

The early time (t<300 s) interaction of the Ba+cloud with the solar wind during the AMPTE comet release is examined, with an emphasis on the issue of the Ba+ion magnetization. It is shown that the observed magnetic field profile is consistent with the Ba+ions being magnetized, in the sense that the cloud radius , is the Ba+gyroradius. As a consequence, any momentum coupling forceFbetween the Ba+cloud and the solar wind in their relative streaming direction will produce an acceleration drift in a direction consistent with the observations. The drift will cease when the cloud expands to the extent that the magnetic field inside the cloud is reduced to satisfy . The implications of the model to observables of the interaction are discussed.

ISSN:0094-8276    

DOI:10.1029/GL013i009p00925

年代:1986

数据来源: WILEY