Dayside observations of thermal-ion upwellings at 800-km altitude: An ionospheric signature of the cleft ion fountain

Technical Report · Wed Nov 01 04:00:00 EST 1989

OSTI ID:6903420

Tsunoda, R T; Livingston, R C; Vickrey, J F; Heelis, R A; Hanson, W B

There is a growing body of evidence that energetic heavy ions observed at one or more Earth radii over the polar cap originate from the dayside ionosphere in the vicinity of the dayside cleft. The ions, consisting mostly of O+, are often characterized by conic pitch-angle distributions, suggesting that they have undergone acceleration transverse to geomagnetic field lines. This process of ion injection from a latitudinally localized source region in the dayside auroral oval followed by dispersal throughout the entire polar cap has been called the cleft ion fountain. But, except for placement of the ion injection source somewhere in the vicinity of the dayside auroral oval, very little is known about the altitude regime in which the source operates and the nature of the process that transports ionospheric ions into the magnetosphere. Results are presented of upward thermal-ion flows measured at 800-km altitude in the dayside polar ionosphere by the Hilat satellite. The characteristics of these thermal ion upwellings (TIU) are described and shown to be closely associated with the cleft ion fountain. We show that TIU events are latitudinally confined and spatially collocated with cleft electron precipitation, upward field-aligned currents, and velocity gradients in magnetospheric convection.

• Research Organization: SRI International, Menlo Park, CA (USA). Geoscience and Engineering Center
• OSTI ID: 6903420
• Report Number(s): AD-A-218011/5/XAB
• Country of Publication: United States
• Language: English

Related Subjects

640201* -- Atmospheric Physics-- Auroral
Ionospheric
& Magetospheric Phenomena
71 CLASSICAL AND QUANTUM MECHANICS
GENERAL PHYSICS
ACCELERATION
ALIGNMENT
ALTITUDE
AURORAL OVAL
CHARGED PARTICLES
CHARGED-PARTICLE PRECIPITATION
CHARGED-PARTICLE TRANSPORT
CONVECTION
COUPLING
CURRENTS
EARTH ATMOSPHERE
EARTH MAGNETOSPHERE
EARTH PLANET
ELECTRIC CURRENTS
ELECTRON PRECIPITATION
ENERGY TRANSFER
GEOMAGNETIC FIELD
HEAT TRANSFER
HEAVY IONS
INJECTION
INTAKE
ION DENSITY
ION SOURCES
IONOSPHERE
IONS
MAGNETIC FIELDS
MASS TRANSFER
ORIGIN
OXYGEN IONS
PLANETARY IONOSPHERES
PLANETS
POLAR REGIONS
RADIATION TRANSPORT
VELOCITY