Quiet-time intensifications along the poleward auroral boundary near midnight

Journal Article · Sat Jan 01 04:00:00 EST 1994 · Journal of Geophysical Research; (United States)

DOI:https://doi.org/10.1029/93JA01947· OSTI ID:6701586

Beaujardiere, O de la ^[1]; Lyons, L R ^[2]; Ruohoniemi, J M; Newell, P T ^[3]; Friis-Christensen, E; Danielsen, C ^[4]; Rich, F J ^[5]

---

1. SRI International, Menlo Park, CA (United States)
2. Aerospace Corp., Los Angeles, CA (United States)
3. Johns Hopkins Univ., Laurel, MD (United States)
4. Hollandervaenget, Dragoer (Denmark)
5. Phillips Lab., Hanscom Air Force Base, MA (United States)

Radar and optical measurements from Sondrestrom are combined with satellite and Goose Bay data in a study of the poleward edge of the nightside auroral oval during a quiet period. The B[sub y] and B[sub z] components of the interplanetary magnetic field were close to zero, and the B[sub x] component was [approximately]8 nT for more than 24 hours. On a large scale, the convection and precipitation patterns remained almost constant during this period; on a small scale, however, the conditions were quite dynamic. At 10- to 20-min intervals the arc that marked the poleward auroral boundary intensified, and a new arc appeared poleward of it. About once per hour, stronger intensifications were observed. One such event is examined in detail. The auroral arcs first appeared to dim, and then they brightened, with a factor of 10 increase in E region electron density. At the time of the brightening a new arc formed poleward of all the arcs. The arcs then drifted southward at velocities of [approximately]270 m/s. A plasma drift disturbance, characterized by a doubling of the southward velocity and a reversal in the east-west component, propagated westward at 900 m/s through the fields of view of the Sondrestrom and Goose Bay radars. A simultaneous satellite overpass close to the radars revealed the presence of an energetic ion event similar to the [open quotes]velocity dispersed ion structures[close quotes] observed on the Aureol satellite and presumed to be the signature of fast ion beams within the plasma sheet boundary layer. The stronger arc intensification events observed by the Sondrestrom radar are associated with an increase in plasma flow across the boundary between open and closed magnetic field lines. The authors interpret this increased flow as the ionospheric signature of abrupt, localized increases in the reconnection rate in the midnight sector. 41 refs., 11 figs.

• OSTI ID: 6701586
• Journal Information: Journal of Geophysical Research; (United States), Journal Name: Journal of Geophysical Research; (United States) Vol. 99:A1; 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 OVAL
CHARGED-PARTICLE PRECIPITATION
MODULATION
PLASMA DRIFT