Engineering topics

Akasofu, S.

Publications and source records attributed to Akasofu, S..

4 records

NASA NTRS1972

Two substorm studies of relations between westward electric fields in the outer plasmasphere, auroral activity, and geomagnetic perturbations

Temporal variations of the westward component of the magnetospheric convection electric field in the outer plasmasphere were compared to auroral activity near L = 7, and to variations in the geomagnetic field at middle and high latitudes. The substorms occurred on July 29, 1965 near 0530 UT and on August 20, 1965 near 0730 UT. The results on westward electric field E(w) were obtained by the whistler method using data from Eights, Antarctica (L is approximately 4). All sky camera records were obtained from Byrd, Antarctica, (L is approximately 7), located within about 1 hour of Eights in magnetic local time. It was found that E(w) within the outer plasmasphere increased rapidly to substorm levels about the time of auroral expansion at nearby longitudes. This behavior is shown to differ from results on E(w) from balloons, which show E(w) reaching enhanced levels prior to the expansion. A close temporal relation was found between the rapid, substorm associated increases in E(w) and a well known type of nightside geomagnetic perturbation. Particularly well defined was the correlation of E(w) rise and a large deviation of the D component at middle latitudes.

Carpenter, D. L.↗

NASA NTRS1971

Geomagnetic storm particles in the high-latitude magnetotail.

Nearly monoenergetic positive ions flowing outward along magnetic-field lines in the high-latitude magnetotail, outside the plasma sheet, have been observed with Vela satellites. These ions, probably mainly protons, are detected only during geomagnetic storms. The ?storm particles' have average energies per charge ranging from about 0.3 to 3 kV, but at any instant the energy distribution is quite narrow, sometimes less than 10%. Their angular distribution is usually narrow, sometimes about 6 deg. Particles with storm-particle characteristics are not observed in the plasma sheet. Possible sources of the storm particles are considered, including the solar wind, magnetosheath, polar cusps, polar wind, or ionosphere, plasma sheet, solar neutral hydrogen streams, reconnection transfer of plasma into the magnetotail from the polar cusps, polar wind, or polar ionosphere, and parallel electric-field acceleration of the polar wind or ionosphere ions along the polar-cap magnetic-field lines. Of these possibilities, the electric-field acceleration is favored.

Bame, S. J.↗

NASA NTRS1971

Magnetospheric substorms in the distant magnetotail observed by Imp 3.

Study of variations of the magnetic field and plasma sheet in the distant magnetotail (20 to 40 earth radii) during magnetospheric substorms on the basis of the Imp 3 magnetic-field and particle data. Depending on the locations of the satellite with respect to the boundary of the plasma sheet, the variations differ greatly. However, the present results and the results of other workers give a clear indication of an increase of the magnitude of the field outside the plasma sheet and of the simultaneous ?thinning' of the plasma sheet during an early phase of substorms. At about the maximum epoch or during the recovery phase of substorms, the plasma sheet expands and appears to be inflated to at least the presubstorm level. Furthermore, a large excessive flux of the magnetic (approximately equal to Z component) field, as compared with the flux of the original dipole field, appears across the neutral sheet.

Meng, C. I.↗

NASA NTRS1971

Cosmic-ray variations and the interplanetary sector structures.

Fifteen passages of interplanetary sector structures that occurred between December 1967 and June 1968 are examined. A spherical harmonic analysis of cosmic ray intensity is performed to obtain cosmic ray intensity variations as a function of asymptotic latitude, longitude, and universal time. A clear north-south asymmetry of cosmic ray intensity, which depends on the sign of the interplanetary sector magnetic fields, is revealed.

Yoshida, S.↗