A model of the magnetospheric substorm
IT is generally recognised that the Earth's magnetic tail and the plasma sheet play a vital role in the processes responsible for the observational phenomenon known as the magnetospheric substorm. Many different models1–5 of substorm behaviour have been described with differing degrees of success, and to propose another requires some justification. A new model, if it is to be useful, must do two things. It must be specific enough to make quantitative theoretical analysis possible, and it must fit the morphological features more completely or in a more elegant way than other models. In addition, it should be distinctive enough from other models to be separated from them by observational tests. I believe the model presented here has those properties.
Plasma-sheet structure and the onset of magnetospheric substorms
Abstract A model is presented in which the plasma sheet is not confined by a closed magneticfield configuration. Instead, the plasma-sheet particles continually leak down the tail along open field lines; the loss rate is controlled by particle scattering with magnetic-field irregularities and waves, and the length of the plasma sheet is determined by loss of plasma-sheet particles to the neutral sheet. The escaping particles are replaced by continuous injection of magnetosheath plasma entering the magnetosphere through the demarcation lines on the dayside magnetopause. According to the model, plasma-sheet particle fluxes at the lunar distance in the tail should normally be less than fluxes observed at the Vela orbital distance by a factor of two or more. The substorm onset in this model is the result of a depletion of the near-Earth plasma sheet owing to enhanced downstream escape. Thus the plasma-sheet ‘drop-out’ observed at the Vela distance should be accompanied by a temporary enhancement of plasma-sheet flux at the lunar distance. Rapid magnetic merging then proceeds in the near-Earth neutral sheet by a simple ‘vacuum merging’ process until the merging is slowed by the reappearance of the plasma sheet near the peak of the substorm.
The REX-ISOLDE project
The Radioactive Beam Experiment REX-ISOLDE [1–3] is a pilot experiment at ISOLDE (CERN) testing the new concept of post acceleration of radioactive ion beams by using charge breeding of the ions in a high charge state ion source and the efficient acceleration of the highly charged ions in a short LINAC using modern ion accelerator structures. In order to prepare the ions for the experiments singly charged radioactive ions from the on-line mass separator ISOLDE will be cooled and bunched in a Penning trap, charge bred in an electron beam ion source (EBIS) and finally accelerated in the LINAC. The LINAC consists of a radiofrequency quadrupole (RFQ) accelerator, which accelerates the ions up to 0.3 MeV/u, an interdigital H-type (IH) structure with a final energy between 1.1 and 1.2 MeV/u and three seven gap resonators, which allow the variation of the final energy. With an energy of the radioactive beams between 0.8 MeV/u and 2.2 MeV/u a wide range of experiments in the field of nuclear spectroscopy, astrophysics and solid state physics will be addressed by REX-ISOLDE.