FEATURES OF STEADY MAGNETOSPHERIC CONVECTION

The large-scale patterns of ionospheric convection and particle precip itation are described during two intervals of steady magnetospheric co nvection (SMC) on November 24, 1981. The unique data set used in the a nalysis includes recordings from the worldwide network of magnetometer s and all-sky cameras, global auroral images from the DE 1 spacecraft, and particle precipitation data from low-altitude NOAA 6 and NOAA 7 s pacecraft. The data show that intense magnetospheric convection contin ued during more than 10 hours under the steady southward interplanetar y magnetic field without any distinct substorm signatures. All data se ts available confirmed the stable character of the large-scale magneto spheric configuration during this period. In particular, the magnetic flux threading the polar cap was stable (within 10%) during 3.5 hours of continued DE 1 observations. The dayside cusp was located at an unu sually low latitude (70-degrees CGL). The nightside auroral pattern co nsisted of two distinct regions. The diffuse aurora in the equatorward half of the expanded (10-degrees wide) auroral oval was well-separate d from the bright, active auroral forms found in the vicinity of the p oleward boundary of the oval. The twin-vortex convection pattern had n o signature of the Harang discontinuity; its nightside ''convection th roat'' was spatially coincident with the poleward active auroras. This region of the auroral oval was identified as the primary site of the short-lived transient activations during the SMC intervals. The energe tic particle observations show that the auroral precipitation up to it s high-latitude limit is on closed field lines and that particle accel eration up to > 30-keV energy starts close to this limit. The isotropi c boundaries of the > 30-keV protons and electrons were found close to each other, separating regions of discrete and diffuse precipitation. This suggests that these precipitation types originate on the very ta illike and very dipolelike field lines, respectively.