Dayside cusp auroral morphology related to nightside magnetic activity
Meridian-scanning photometer (MSP) measurements of atmospheric optical emissions made in Long-yearbyen, Svalbard, in the winter of 1978--1979 show two major types of daytime auroras associated with the magnetospheric cusp region. A steady, subvisual arc extending over 1.5 /sup 0/to 5 /sup 0/ of invariant latitude characterized by a predominance of 6300-A emission is a permanent feature of the cusp region. Additionally, short-lived, relatively narrow arcs and bands appear occasionally within this region; in these transient auroral forms the (O I) 5577-A line and the N/sub 2//sup +/ 1 NG bands are the strong optical emissions. Detailed correlation of the cusp optical emission and simultaneous geomagnetic measurements from both day and nightside stations show that the cusp, as defined by the 6300-A arcs, moves equatorward during magnetically disturbed conditions. This equatorward drift of the cusp region is directly proportional to the maximum negative excursion of the horizontal disturbance magnetic field in the meridian, which is approximately 180 /sup 0/ displaced in longitude from the dayside cusp; (while the local magnetic disturbance on Svalbard is remarkably similar to nightside observations, it is approximately a factor of 5 less intense, making it difficult to correlate cusp position with local magnetic activity during relatively weak magnetic substorms). From three days of simultaneous data it may be seen that an increase in cusp auroral activity is characterized by the appearance of discrete auroral arcs and bands that occur in the prenoon and post-noon periods. The most significant result from these measurements is the absence of any detectable delay between the enhancement in cusp auroral activity and the commencement of magnetic disturbance at a station situated under maximum electrojet current on the nightside.
- Research Organization:
- University of Tromso, 9000 Tromso, Norway
- OSTI ID:
- 5096312
- Journal Information:
- J. Geophys. Res.; (United States), Vol. 85:A8
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
GENERAL PHYSICS
MAGNETIC BAYS
VISIBLE RADIATION
MIDDAY AURORAE
MORPHOLOGY
POLAR CUSP
ALASKA
ANTARCTICA
EXPERIMENTAL DATA
GEOMAGNETIC FIELD
MAGNETIC STORMS
MAGNETOSPHERE
NITROGEN IONS
PHOTOMETRY
ANTARCTIC REGIONS
AURORAE
CHARGED PARTICLES
DATA
EARTH ATMOSPHERE
ELECTROMAGNETIC RADIATION
INFORMATION
IONS
MAGNETIC FIELDS
NORTH AMERICA
NUMERICAL DATA
PACIFIC NORTHWEST REGION
POLAR REGIONS
RADIATIONS
USA
640201* - Atmospheric Physics- Auroral
Ionospheric
& Magetospheric Phenomena