Engineering topics

Sibeck, David G.

Publications and source records attributed to Sibeck, David G..

39 records · Page 3

NASA NTRS1990

The AMPTE program's contribution to studies of the solar wind-magnetosphere-ionosphere interaction

The Active Magnetospheric Particle Tracer Explorers (AMPTE) program provided important information on the behavior of clouds of plasma artificially injected into the solar wind and the earth's magnetosphere. Now that the releases are over, data from the satellites are being analyzed to investigate the processes by which the ambient solar wind mass, momentum, and energy are transferred to the magnetosphere. Work in progress at APL indicates that the solar wind is much more inhomogeneous than previously believed, that the solar wind constantly buffets the magnetosphere, and that ground observers may remotely sense these interactions as geomagnetic pulsations.

Sibeck, David G.↗

NASA NTRS1990

Evidence for flux ropes in the earth's magnetotail

Magnetic field reconnection is a fundamental process that occurs in the magnetotail during geomagnetic substorms. Some 2D reconnection models predict the formation of a plasmoid, or closed loop of magnetic field lines, in the noon-midnight meridional plane at those times. When the 3D magnetotail magnetic field is considered, it becomes clear that reconnection produces a flux rope with an axis transverse to the earth-sun line. Three signatures mark both 2D plasmoids and 3D flux ropes: (1) a bipolar magnetic field signature, (2) tailward flow of a hot plasma, and (3) convecting isotropic energetic particle distributions. Plasmoids and flux ropes may be distinguished by (4) the axial magnetic field that only flux ropes possess. All four signatures have been identified in near-earth, middle, and distant magnetotail observations, but their interpretation is disputed. Thus, the existence of magnetotail flux ropes remains a controversial subject.

Sibeck, David G.↗

NASA NTRS1989

Some low-altitude cusp dependencies on the interplanetary magnetic field

The low-altitude cusp dependencies on the interplanetary magnetic field (IMF) were investigated using the algorithm of Newell and Meng (1988) to identify the cusp proper. The algorithm was applied to 12,569 high-latitude dayside passes of the DMSP F7 spacecraft, and the resulting cusp positioning data were correlated with the IMF. It was found that the cusp latitudinal position correlated reasonably well (0.70) with the Bz component when the IMF had a southward component. The correlation for the northward Bz component was only 0.18, suggestive of a half-wave rectifier effect. The ratio of cusp ion number flux precipitation for Bz southward to that for Bz northward was 1.75 + or - 0.12. The statistical local time widths of the cusp proper for the northward and the southward Bz components were found to be 2.1 h and 2.8 h, respectively.

Newell, Patrick T.↗