Characteristics of ionospheric bubbles determined from aspect sensitive scatter spread F observed with Alouette 1

Journal Article · Thu May 01 04:00:00 EDT 1980 · J. Geophys. Res.; (United States)

DOI:https://doi.org/10.1029/JA085iA05p02115· OSTI ID:5328629

Muldrew, D B

Aspect sensitive scatter from bubbles is observed on a large percentage of equatorial Alouette 1 ionograms. The occurrence frequency of bubbles increases sharply (from zero) after sunset and reaches a maximum at about 23--24 hours local time. Near midnight, bubbles are observed in the topside ionosphere on about 65% of American and African satellite passes and on about 50% of Asian passes. The frequency of occurrence decreases gradually throughout the postmidnight and morning periods and becomes almost zero near noon. Averaged over the whole day, the occurrence of bubbles at Asian logitudes is about one half that at American and African longitudes. The occurrence of bubbles peaks at the December solstice for American longitudes and at the June solstice for Asian longitudes. The above observations imply that bubbles are initiated by field-aligned currents at the steep density gradient at the bottom of the postsunset F layer by the mechanism proposed by K. D. Cole. After initiation the Rayleigh-Taylor instability takes over to raise the bubbles through the F layer. Alouette 1 observations indicate that the bubbles rise to a maximum height of about 600--1000 km near midnight. The height then decreases gradually until some time after sunrise. Ray tracing, assuming aspect sensitive scatter and a circular cross section for the field-aligned bubble, indicates that a particular, typical bubble was about 28 km in radius and intersected the vertical plane through the satellite in the magnetic east-west direction, about 550 km below and about 750 km to the east or west of the satellite. In the topside ionosphere below Alouette 1, bubbles never seem to occupy more than about 2% of the total space.

• Research Organization: Communications Research Centre, Department of Communications, Ottawa, Ontario, Canada K2H 8S2
• OSTI ID: 5328629
• Journal Information: J. Geophys. Res.; (United States), Journal Name: J. Geophys. Res.; (United States) Vol. 85:A5; ISSN JGREA
• Country of Publication: United States
• Language: English

Related Subjects

640201* -- Atmospheric Physics-- Auroral
Ionospheric
& Magetospheric Phenomena
71 CLASSICAL AND QUANTUM MECHANICS
GENERAL PHYSICS
DAILY VARIATIONS
EARTH ATMOSPHERE
F REGION
GEOGRAPHICAL VARIATIONS
INSTABILITY
ION DENSITY
IONOSPHERE
IONOSPHERIC STORMS
PLANETARY IONOSPHERES
RAYLEIGH-TAYLOR INSTABILITY
VARIATIONS