Accession Number:

AD0779761

Title:

Micropulsation Observations of the Auroral Oval Boundary.

Descriptive Note:

Environmental research papers,

Corporate Author:

AIR FORCE CAMBRIDGE RESEARCH LABS L G HANSCOM FIELD MASS

Personal Author(s):

Report Date:

1974-01-28

Pagination or Media Count:

35.0

Abstract:

At the sub-auroral-zone latitude 54 degrees geomagnetic of the AFCRL field station, geomagnetic micropulsations associated with the auroral oval are observed only during large nighttime disturbances. Hourly amplitudes of the horizontal component of the micropulsations in octave period bands in the 0.5 to 1024 sec period range are used as measures of the activity. Near local midnight, consistently small values are observed with local K indices or 5. The southern boundary of the expanding oval approaches the station as the K index increases to 7, and large amplitudes appear. The A-O auroral oval micropulsations are attributed to hydromagnetic waves that propagate in the guided mode from the plasma sheet in the magnetospheric tail. The diurnal variations of the A-O amplitudes, which depend upon the micropulsation periods, are attributed to variations of the source strength in the plasma sheet. Author

Subject Categories:

  • Atmospheric Physics
  • Geomagnetism

Distribution Statement:

APPROVED FOR PUBLIC RELEASE