The quiet time polar cap: DE 1 observations and conceptual model

Journal Article · Tue Dec 01 04:00:00 EST 1992 · Journal of Geophysical Research; (United States)

DOI:https://doi.org/10.1029/92JA01537· OSTI ID:6788654

Burch, J L ^[1]; Saflekos, N A ^[2]; Gurnett, D A; Frank, L A ^[3]; Craven, J D ^[4]

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1. Southwest Research Inst., San Antonio, TX (United States)
2. Univ. of Texas, San Antonio (United States)
3. Univ. of Iowa, Iowa City (United States)
4. Univ. of Alaska, Fairbanks (United States)

Auroral activity increases over the polar caps during quiet times, which are associated with northward interplanetary magnetic field (IMF) components. Polar cap auroras (Sun-aligned arcs, theta auroras, and horse collar auroras) occur under these conditions. DE 1 data have provided partial characterization of these events. A conceptual northward IMF merging model containing lobe cells, merging cells, and viscous cells is shown to be consistent with the observations. As the IMF becomes more northward, the polar arc configuration changes from the horse collar pattern to the theta aurora pattern in the model, and this is shown to be generally true for the set of published data on these phenomena. The model involves dayside merging both at high latitudes on open field lines and at lower latitudes on closed field lines. The ratio between the merged flux produced by the high-latitude merging to that produced by the lower-latitude merging increases as the IMF becomes more northward. Two types of open field lines, equator-crossing and non-equator-crossing, are produced by the higher- and lower-latitude merging, respectively. The equator-crossing field lines have a strong azimuthal component of convection as they flow around the magnetopause, while the non-equator-crossing field lines can convect more or less directly across the polar cap, leading to an antisunward flow channel across the central polar cap. This antisunward flow region grows as the IMF becomes less northward, causing dual polar cap arcs to spread out into the horse collar configuration.

• OSTI ID: 6788654
• Journal Information: Journal of Geophysical Research; (United States), Journal Name: Journal of Geophysical Research; (United States) Vol. 97:A12; ISSN JGREA2; ISSN 0148-0227
• Country of Publication: United States
• Language: English

Related Subjects

661320* -- Auroral
Ionospheric
& Magnetospheric Phenomena-- (1992-)
71 CLASSICAL AND QUANTUM MECHANICS
GENERAL PHYSICS
AURORAE
AURORAL HISS
AURORAL OVAL
CONVECTION
ELECTROMAGNETIC RADIATION
ENERGY TRANSFER
GEOGRAPHICAL VARIATIONS
HEAT TRANSFER
INTERPLANETARY MAGNETIC FIELDS
LATITUDE EFFECT
MAGNETIC FIELDS
MAGNETIC RECONNECTION
MAGNETOPAUSE
MASS TRANSFER
ORIENTATION
POLAR-CAP AURORAE
RADIATIONS
SOLAR ACTIVITY
SOLAR WIND
VARIATIONS