Generation of energetic proton shells during substorms

Journal Article · Fri Feb 01 00:00:00 EST 1991 · Journal of Geophysical Research; (United States)

DOI:https://doi.org/10.1029/90JA02152· OSTI ID:5188351

Delcourt, D C ^[1]; Sauvaud, J A ^[2]

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1. European Space Agency/European Space Research and Technology, Noordwijk (Netherlands)
2. Centre National de la Recherche Scientifique, Toulouse (France)

The circulation of the terrestrial polar wind during dynamical reconfigurations of the geomagnetic field is systematically examined by means of three-dimensional single-particle codes. In these calculations the storm time collapse of the geomagnetic tail is simulated by a gradual evolution of the Mead and Fairfield (1975) model from disturbed to ground state geometry. The polar wind is considered to consist primarily of protons, distributed throughout the magnetosphere at substorm onset consistently with the large-scale plasma convection. The simulations clearly illustrate the convection surge accompanying the development of substorms, displaying an overall earthward compression of the H{sup +} populations. Among these, a dense and low-energy core can be identified at close L shells (within L{approximately}7), which appears as a persistent feature during the dipolarization process. Tailward of these inner regions, the simulations demonstrate a pileup of protons initiated in the mid-tail ({approximately}10-15 R{sub E}), which experience intense (several keV) accelerations and pitch angle diffusion owing to the transient breaking of their adiabatic invariants. Most notably, a detailed analysis of the trajectory results reveals a sharp earthward boundary for these newly created energetic H{sup +}, which corresponds to the postdipolarization image of the ion adiabatic threshold in the geomagnetic tail. Further nonadiabatic considerations suggest that this mechanism which supports the substorm injection boundary concept depends upon particle mass per charge and may consequently organize distinct ion layers at the inner edge of the plasma sheet.

• OSTI ID: 5188351
• Journal Information: Journal of Geophysical Research; (United States), Vol. 96:A2; ISSN 0148-0227
• Country of Publication: United States
• Language: English

Related Subjects

71 CLASSICAL AND QUANTUM MECHANICS
GENERAL PHYSICS
POLAR REGIONS
ION DRIFT
ACCELERATION
COMPRESSION
COMPUTERIZED SIMULATION
CONVECTION
DIFFUSION
EARTH MAGNETOSPHERE
GEOMAGNETIC FIELD
ION DENSITY
MAGNETIC BAYS
MAGNETOTAIL
PLASMA SHEET
PROTONS
TRAJECTORIES
BARYONS
EARTH ATMOSPHERE
ELEMENTARY PARTICLES
ENERGY TRANSFER
FERMIONS
HADRONS
HEAT TRANSFER
MAGNETIC FIELDS
MASS TRANSFER
NUCLEONS
SIMULATION
640201* - Atmospheric Physics- Auroral
Ionospheric
& Magetospheric Phenomena