The goal of this work is to explain the formation of the quiet‐time electron slot, which divides the radiation belt electrons into an inner and an outer zone. We quantitatively investigate the pitch‐angle diffusion of radiation belt electrons resulting from resonant interactions with the observed plasmaspheric whistler‐mode wave band. The effects of wave propagation obliquely to the geomagnetic field direction with the resulting diffusion at all cyclotron‐harmonic resonances and the Landau resonance are evaluated along with the effects of interactions occurring at all geomagnetic latitudes. Our results account for the long‐term stability of the inner radiation zone, the location of its outer edge as a function of electron energy, and the removal of electrons to levels near zero throughout the slot. Computed pitch‐angle distributions and precipitation decay rates are in good agreement with slot‐region observations.

General relations for quasi-linear diffusion coefficients in pitch angle and energy are applied to resonant particle interactions with ion–cyclotron and whistler waves. Expressions for the diffusion coefficients, valid for any distribution of wave energy with frequency and wave normal angle, are derived and normalized to be independent of the ambient magnetic field intensity and the electron density. The results illustrate how resonant particle diffusion rates vary with pitch angle and energy, and how the diffusion rates depend upon the distribution of wave energy.

Abstract. Poleward boundary intensifications are nightside geomagnetic disturbances that have an auroral signature that moves equatorward from the poleward boundary of the auroral zone. They occur repetitively, so that many individual disturbances can occur during time intervals of-1 hour, and they appear to be the most intense auroral disturbance at times other than the expansion phase of substorms. We have used data from three nightside conjunctions of the Geotail spacecraft in the magnetotail with the Canadian Auroral Network for the OPEN Program Unified Study (CANOPUS) ground-based array in central Canada to investigate the relation between the poleward boundary intensifications and bursty plasma sheet flows and to characterize the bursty flows associated with the disturbances. We have found a distinct difference in plasma sheet dynamics between periods with, and periods without, poleward boundary intensifications. During periods with identifiable poleward boundary intensifications, the plasma sheet has considerable structure and bursty flow activity. During periods without such poleward boundary intensifications, the plasma sheet was found to be far more stable with fewer and weaker bursty flows. This is consistent with the intensifications being the result of the mapping to the ionosphere of the electric fields that give rise to bursty flows within the plasma sheet. Two different types of plasma sheet disturbance have been found to be associated with the poleward boundary intensifications. The first consists of plasma sheet flows that appear to be the result of Speiser motion of particles in a localized region of thin current sheet. The second, seen primarily in our nearest-to-the-Earth example, consists of energy-dispersed ion structures that culminate in bursts of low-energy ions and isotropic low-energy electrons and are associated with minima in magnetic field and temperature and maxima in ion density and pressure. Both types of plasma sheet disturbance are associated with localized regions of enhanced dawn-to-dusk electric fields and appear to be associated with localized enhanced reconnection. Our analysis has shown that poleward boundary intensifications are an important aspect of geomagnetic activity that is distinct from substorms. In addition to their very distinct auroral signature, we have found them to be associated with a prolonged series of ground magnetic Pi 2 pulsations and ground X component perturbations, which peak at latitudes near the ionospheric mapping of the magnetic separatrix, and with a series of magnetic B z oscillations near synchronous orbit. Like substorms, the tail dynamics associated with the poleward boundary intensifications can apparently extend throughout the entire radial extent of the plasma sheet. Color versions of figures are available at http ://www' atmøs'ucla'edu/-larry/geøtail'html'

Abstract. We present direct evidence that transient Earthward flow bursts in the magnetotail can produce an observable signature in the optical aurora. This signature is noah-south aligned auroral structures that are extensions of transient intensifications near the poleward boundary of the auroral oval. Our study focuses on the period from 0500 to 0700 UT on January 7, 1997, during which five distinct flow bursts are observed in the Geotail data. At that time, the spacecraft was located approximately 30 RE downtail on field lines that project down to the CANOPUS array of ground based instruments. We find that each of the flow bursts seen in the Geotail data is associated with an auroral poleward boundary intensification (PBI) observed in the CANOPUS meridian scanning photometer (MSP) data, which appears as a noah-south aligned auroral structure in the CANOPUS allsky imager (ASI) data. Based on these observations we estimate that the fast flows originated between 50 and 100 RE downtail.

The diffusion of electrons in resonance with the intense electrostatic waves recently observed on auroral lines of force is quantitatively investigated. Diffusion coefficients for scattering in both energy and pitch angle are presented as a function of electron energy and equatorial pitch angle. The results show that the waves should generally cause strong pitch angle diffusion and significant energy diffusion for electrons of energies between a few tenths and a few keV. During periods of the most intense waves observed, electrons of energies up to 100 keV can be put on strong diffusion. Measurements of 1‐ to 20‐keV precipitating electrons made during a postbreakup aurora are found to be consistent with the pitch angle anisotropy as a function of electron energy that is predicted to result from interactions with these waves. Additional effects of the waves on the pitch angle and energy distributions of electrons are also discussed.