Midday auroral breakup events and related energy and momentum transfer from the magnetosheath

Journal Article · Thu Feb 01 04:00:00 EST 1990 · Journal of Geophysical Research; (United States)

DOI:https://doi.org/10.1029/JA095iA02p01039· OSTI ID:5027461

Sandholt, P E; Lybekk, B; Egeland, A ^[1]; Lockwood, M; Freeman, K S; Willis, D M ^[2]; Oguti, T ^[3]; Cowley, S W.H. ^[4]

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1. Univ. of Oslo (Norway)
2. Rutherford Appleton Lab., Chilton (England)
3. Geophysics Research Lab., Tokyo (Japan)
4. Imperial College, London (England)

Combined observations by meridian-scanning photometers, all-sky auroral TV camera and the EISCAT radar permitted a detailed analysis of the temporal and spatial development of the midday auroral breakup phenomenon and the related ionospheric ion flow pattern within the 71{degree} - 75{degree} invariant latitude radar field of view. The radar data revealed dominating northward and westward ion drifts, of magnitudes close to the corresponding velocities of the discrete, transient auroral forms, during the two different events reported here. The spatial scales of the discrete optical events were {approximately}50 km in latitude by {approximately}500 km in longitude, and their lifetimes were less than 10 min. Electric potential enhancements with peak values in the 30-50 kV range are inferred along the discrete arc in the IMF {vert bar}B{sub y}/B{sub z}{vert bar} {lt} 1 case from the optical data and across the latitudinal extent of the radar field of view in the {vert bar}B{sub y}/B{sub z}{vert bar} {gt} 2 case. Joule heat dissipation rates in the maximum phase of the discrete structures of {approximately} 100 ergs cm{sup {minus}2} s{sup {minus}1} (0.1 W m{sup {minus}2}) are estimated from the photometer intensities and the ion drift data. These observations combined with the additional characteristics of the events, documented here and in several recent studies are considered to be stong evidence in favour of a transient, intermittent reconnection process at the dayside magnetopause and associated energy and momentum transfer to the ionosphere in the polar cusp and cleft regions.

• OSTI ID: 5027461
• Journal Information: Journal of Geophysical Research; (United States), Journal Name: Journal of Geophysical Research; (United States) Vol. 95:A2; ISSN 0148-0227; 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
AURORAE
CAMERAS
DATA ANALYSIS
DISTRIBUTION
EARTH ATMOSPHERE
ELECTRIC HEATING
ELECTRIC POTENTIAL
ENERGY TRANSFER
HEATING
INTERACTIONS
INTERPLANETARY MAGNETIC FIELDS
ION DRIFT
IONOSPHERE
JOULE HEATING
MAGNETIC FIELDS
MAGNETIC RECONNECTION
MAGNETOPAUSE
MAGNETOSHEATH
MEASURING INSTRUMENTS
MOMENTUM TRANSFER
PHOTOMETERS
PLANETARY IONOSPHERES
PLASMA HEATING
POLAR CUSP
RADAR
RANGE FINDERS
RESISTANCE HEATING
SPATIAL DISTRIBUTION
TIME DEPENDENCE