Details

Autor(en) / Beteiligte

• Ahmed, M.
• Sagalyn, R. C.

Titel

Thermal positive ions in the outer ionosphere and magnetosphere from Ogo 1

Ist Teil von

• Journal of Geophysical Research, 1972-03, Vol.77 (7), p.1205-1220

Ort / Verlag

Blackwell Publishing Ltd

Erscheinungsjahr

1972

Link zum Volltext

Beschreibungen/Notizen

• Thermal positive ion densities measured with a spherical electrostatic analyzer aboard Ogo 1 on approximately 25 orbits between September and December 1964 have been studied. The charged‐particle distributions exhibit a highly variable character within and beyond the plasmapause boundary. The presence of the plasmapause, though quite evident in most cases, is not obvious in some, whereas on a few orbits more than one steep density decrease is observed. The density gradient at the plasmapause varies between 3 × 10−2 and 6.0 ions/cm³/km. The magnitude of the density gradient is inversely related to the plasmapause L position and is consistently about an order of magnitude higher for the afternoon sector orbits than for the nightside orbits. Within the plasmasphere irregularities are observed on the density distributions in the form of troughs and humps, whereas beyond the plasmapause the irregularities exhibit ‘wavelike’ structures with wavelengths in the range of 0.1‐0.3 L. The amplitude of these fluctuations is most commonly about a factor of 2 relative to background magnetospheric density; however, excursions from 20% to a factor of 20 are observed. These irregularities do not show any correlation with the level of magnetic activity. A delay of 3–9 hours is found in the movement of the plasmapause following an increase in the level of magnetic activity on the nightside. Similar studies in the afternoon sector show that the plasmapause location correlates best with the magnetic activity that existed when the sampled plasma was in the formative nightside region rather than with the magnetic activity immediately preceding the plasmapause measurement.