Periodic auroral events at the high-latitude convection reversal in the 16 MLT region

Journal Article · Mon Oct 01 04:00:00 EDT 1990 · Geophysical Research Letters (American Geophysical Union); (United States)

DOI:https://doi.org/10.1029/GL017i011p01877· OSTI ID:5514906

Sandholt, P E ^[1]; Lockwood, M ^[2]

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1. Univ. of Oslo (Norway)
2. Rutherford Appleton Lab., Chilton (England)

Combined optical and radar observations of two breakup-like auroral events near the polar cap boundary, within 74-76{degree} MLAT and 1,210-1,240 UT (roughly 1,540-1,610 MLT) on 9 Jan. 1989 are reported. A two-component structure of the auroral phenomenon is indicated, with a local intensification of the pre-existing arc as well as a separate, tailward moving discrete auroral event on the poleward side of the background aurora, close to the reversal between well-defined zones of sunward and tailward ion flows. The all-sky TV observations do not indicate a connection between the two components, which also show different optical spectral composition. The 16 MLT background arc is located on sunward convecting field lines, as opposed to the 12-14 MLT auroral emission observed on this day. Although the magnetospheric plasma source(s) of the 16 MLT events are not easily identified from these ground-based data alone, it is suggested that the lower and higher latitude components, may map to the plasma sheet boundary layer and along open field lines to the magnetopause boundary, respectively. The events occur at the time of enhancements of westward ionospheric ion flow and corresponding eastward electrojet current south of 74{degree} MLAT. Thus, they seem to be very significant events, involving periodic (10 min period), tailward moving filaments of field-aligned current/discrete auroral emission at the 16 MLT polar cap boundary.

• OSTI ID: 5514906
• Journal Information: Geophysical Research Letters (American Geophysical Union); (United States), Journal Name: Geophysical Research Letters (American Geophysical Union); (United States) Vol. 17:11; ISSN GPRLA; ISSN 0094-8276
• Country of Publication: United States
• Language: English

Related Subjects

640201* -- Atmospheric Physics-- Auroral
Ionospheric
& Magetospheric Phenomena
71 CLASSICAL AND QUANTUM MECHANICS
GENERAL PHYSICS
AURORAE
BOUNDARY LAYERS
CURRENTS
EARTH ATMOSPHERE
EARTH MAGNETOSPHERE
ELECTRIC CURRENTS
ELECTROJETS
GROUND LEVEL
HELMHOLTZ INSTABILITY
INSTABILITY
ION DRIFT
LAYERS
LEVELS
MAGNETIC RECONNECTION
MAGNETOPAUSE
MAGNETOTAIL
MEASURING INSTRUMENTS
MORPHOLOGY
PLASMA INSTABILITY
PLASMA MACROINSTABILITIES
POLAR REGIONS
RADAR
RANGE FINDERS
SHEAR
SPECTRA
VISIBLE SPECTRA