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[1] Energy spectra of electron microbursts in the energy range 170-360 keV have been measured in the outer radiation zone by the low-altitude (680 km), polarorbiting Korean satellite STSAT-1. These electrons are the lower energy population of relativistic microbursts. Our observations show microburst energy spectra of precipitated electrons inside the loss cone (precipitated) have higher e-folding energies during disturbed times than quiet times. The loss cone at these energies is empty except when microbursts abruptly appear and fill the loss cone in less than 50 msec. This fast pitch angle diffusion requires diffusion coefficients larger than $3.5 Â 10 À2 rad 2 /sec, while $1.5 Â 10 À5 rad 2 /sec was proposed by a wave particle interaction theory. The source of microbursts remains unknown as our observations are not adequately explained by wave and particle resonant interaction models.

We carry out the linear viscous-irrotational analysis of capillary instability with heat transfer and phase change. We consider the cylindrical interface shared by two viscous incompressible fluids enclosed by two concentric cylinders. In viscous potential flow, viscosity enters the model through the balance of normal stresses at the interface. We write the dispersion relation from the stability analysis for axisymmetric disturbances in terms of a set of dimensionless numbers that arise in this phase change problem. For the film boiling condition, plots depicting the effect of some of these parameters on the maximum growth rate for unstable perturbations and critical wavenumber for marginal stability are presented and interpreted. Viscous effects of a purely irrotational motion in the presence of heat and mass transfer can stabilize an otherwise unstable gas-liquid interface.

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Previously, the pitch angle distribution of monoenergetic and broadband electron precipitation has been investigated mainly by case studies. The main focus of this study is quantitative comparison of pitch angle distributions between monoenergetic and broadband electron precipitations using long-term observations on board one platform. From December 2003 to October 2004, Science and Technology Satellite-I (altitude∼680 km) regularly observed auroral electron flux and cold ambient plasma parameters during quiet and moderately disturbed conditions. Monoenergetic electron precipitation has notable perpendicular anisotropy, while broadband electron precipitation is much more field aligned. As for other features of monoenergetic and broadband electron precipitation, the characteristic energy of precipitating electrons is slightly higher for monoenergetic (around 1 keV) than for broadband electron precipitation (from several hundred eV to 1 keV). For both monoenergetic and broadband types, the characteristic energy and energy flux do not show clear correlation with cold ambient plasma density/temperature.