Dynamics of plasma, energetic particles, and fields near synchronous orbit in the nighttime sector during magnetospheric substorms

Journal Article · Thu May 01 00:00:00 EDT 1980 · J. Geophys. Res.; (United States)

DOI:https://doi.org/10.1029/JA085iA05p02043· OSTI ID:5234869

Sauvaud, J h; Winckler, J R

We discuss two phases of substorm-associated magnetospheric dynamics in terms of the particles and fields at synchronous orbit. The first phase corresponds to the 'decreases' of energetic particle flux first identified by Erickson and Winckler (1973) and discussed by Walker et al. (1976) and Erickson et al. (1979). This phase begins one-half hour to one hour before the substorm onset and is characterized by (1) a distortion of the magnetosphere to a more taillike configuration caused by (2) an intensification and/or motion toward the earth of the cross-tail current and of its earthward part, the partial ring current, (3) a shift of trapped particle trajectories closer to the earth on the nightside following contours of constant B causing the particle 'decreases' accompanied by a change in the pitch angle distributions from 'pancake' to 'butterfly' as observed at geostationary orbit, (4) an initiation of a response of the auroral electrojet (AE) index. The decreases of energetic particle flux can correspond to the substorm growth phase as defined initially by McPherron (1970) or the growth or precursor phase of Erickson et al. (1979). Plasma motions and current during decreases tend to be variable, but the description above nevertheless characterizes the large-scale trend. It is suggested that the electric field induced by the increasing tail current near the earth acts opposite to the cross-tail convection field and can temporarily inhibit convection near the geostationary orbit. The second phase is the conventional expansion phase.

• Research Organization: School of Physics and Astronomy, University of Minnesota, Minneapolis, Ninnesota 55455
• OSTI ID: 5234869
• Journal Information: J. Geophys. Res.; (United States), Vol. 85:A5
• Country of Publication: United States
• Language: English

Related Subjects

71 CLASSICAL AND QUANTUM MECHANICS
GENERAL PHYSICS
MAGNETOSPHERE
CHARGED-PARTICLE PRECIPITATION
ELECTROJETS
INCLINATION
MAGNETIC BAYS
MAGNETIC FIELD CONFIGURATIONS
MAGNETOTAIL
PLASMA EXPANSION
RADIATION BELTS
TRAPPED ELECTRONS
CURRENTS
EARTH ATMOSPHERE
ELECTRIC CURRENTS
ELECTRONS
ELEMENTARY PARTICLES
EXPANSION
FERMIONS
LEPTONS
640203* - Atmospheric Physics- Magnetospheric Phenomena- (-1987)