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Volume 42, Issue 12
Displaying 1-5 of 5 articles from this issue
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F. Curtis MICHEL1990 Volume 42 Issue 12 Pages 1341-1349
Published: 1990
Released on J-STAGE: September 14, 2010
JOURNAL FREE ACCESSIn the Michel-Dessler theory of pulsars, pulsar action is stimulated by the presence of a fossil Kepler disk. Pulsar extinction occurs when this disk is pushed beyond the corotation distance. Once pulsar action ceases, a thin disk will very slowly expand away from this very dense reservoir under internal viscous forces. When the inner edge approaches sufficiently close to the star, a runaway ionization instability that will cause this thin disk to become fully ionized and be precipitated onto the neutron star surface. Quite nominal estimates suggest that energies of 1039 ergs or more could be released with rise times as fast as 0.3 milliseconds. Because every extinct pulsar would be surrounded by such a disk, there should be a large number of such objects and we estimate that pulses could be produced at the rate of several a month from the nearby (few hundred parsecs) spherically distributed population of the otherwise inactive neutron stars. The mass of the reservoir (estimated to be about 10-5M_??_) would be adequate to supply one burst/year over the age of the universe. Our rough estimate, however, is that each source bursts only once in about 105 years. These numbers seem broadly consistent with observed properties of gamma-ray bursters.View full abstractDownload PDF (869K) -
H. O. RUCKER, M. D. DESCH1990 Volume 42 Issue 12 Pages 1351-1363
Published: 1990
Released on J-STAGE: September 14, 2010
JOURNAL FREE ACCESSPrevious studies on the periodicities of the Saturnian kilometric radiation (SKR) suggested a considerable solar wind influence on the occurrence of SKR, so it was obvious to investigate the relationship between parameters of the solar wind/interplanetary medium and this Saturnian radio component.
Voyager 2 data from the Plasma Science experiment, the Magnetometer experiment and the Planetary Radio Astronomy experiment were used to analyse the external control of SKR. Out of the examined quantities known to be important in controlling magnetospheric processes this investigation yielded a dominance of the solar wind momentum, ram pressure and kinetic energy flux, in stimulating SKR and controlling its activity and emitted energy, and confirmed the results of the Voyager 1 analysis.View full abstractDownload PDF (1434K) -
J. L. BURCH, J. D. MENIETTI, J. A. SLAVIN1990 Volume 42 Issue 12 Pages 1365-1378
Published: 1990
Released on J-STAGE: September 14, 2010
JOURNAL FREE ACCESSData from Dynamics Explorer hot-plasma and magnetic-field instruments have been used to investigate the characteristics of dayside electron acceleration regions, or inverted-V's, and the nature of the field-aligned currents that flow in their vicinity. The data set examined in this study was obtained in the pre-noon sector, where the region-1 field-aligned currents are typically flowing downward. Although not permanent features of the dayside auroral region, inverted-V events are commonly observed to occur just equatorward of the cusp or cleft in a region which contains trapped electrons and which is believed to map to the boundary layer. The downward region-1 currents are observed either just poleward of the trapping boundary in the equatorward part of the cleft or, at times, within the same flux tubes as the inverted-V events. In either location, the region-1 currents are carried by accelerated ionospheric electrons flowing out of the ionosphere. Therefore, when the region-1 currents flow through the inverted-V events, both upward electron beams and upward ion beams are observed together. Although the inferred potential drops associated with the dayside inverted-V events are about a factor of ten smaller than those observed on the night side, a downward field-aligned current is not consistent with common assumptions regarding the generation of auroral acceleration regions. Moreover, the existence of upward-accelerated ionospheric electrons within the inverted-V events is inconsistent with their acceleration by parallel potential drops.View full abstractDownload PDF (5212K) -
V. Yu. TRAKHTENGERTS, A. Ya FELDSTEIN1990 Volume 42 Issue 12 Pages 1379-1384
Published: 1990
Released on J-STAGE: September 14, 2010
JOURNAL FREE ACCESSThe interaction between ionosphere and neutral atmosphere at heights of the dynamo-region leads to the development of Alfven mode instability when the convection velocity exceeds the threshold value VΠ≈0.1km/s. The ionospheric Alfven resonator (IAR) plays an important role as an accumulator of turbulent energy. As a result, a turbulent boundary layer is formed consisting of anisotropic Alfven vortices captured in the IAR. Their anomalous dissipation contributes greatly to the substorm energy budget.View full abstractDownload PDF (447K) -
A. VALLANCE JONES, R. L. GATTINGER1990 Volume 42 Issue 12 Pages 1385-1410
Published: 1990
Released on J-STAGE: September 14, 2010
JOURNAL FREE ACCESSThe main features of the ultraviolet, visible and infrared spectra of aurora are described. Excitation processes by auroral primary particles are summarized. A simple approach is followed to provide an understanding of the main factors influencing the dependence of the relative intensity of features of the auroral spectrum on incident particle energy and atmospheric parameters. The status of the use of various optical measurements to infer average particle energies and total energy fluxes is reviewed including comments on precautions to be observed and limitations to be considered in the application and interpretation of optical measurements.View full abstractDownload PDF (2160K)
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