Micropulsation Observations of the Auroral Oval Boundary.
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)
Document Details
- Document Type
- Technical Report
- Publication Date
- Jan 28, 1974
- Accession Number
- AD0779761
Entities
People
- Elwood Maple
Organizations
- Air Force Cambridge Research Laboratories