The distribution of ion beams and conics below 8000 km

Measurements from electrostatic analyzers aboard the polar‐orbiting S3‐3 satellite have been tabulated to form a synoptic picture of the occurrence of upgoing 90eV to 3.9keV auroral ions. In this survey, a distinction is made between ion distributions having peak fluxes along B (beams) and those exhibiting flux maxima that are not field‐aligned (conics). It is shown that both beams and conics are common auroral phenomena, whose frequencies of occurrence in latitude, local time, and altitude have a marked dependence on magnetic activity. During quiet conditions ( Kp ≲3) conical ion distributions are observed with constant frequency in altitude above 1000 km and appear to be associated with the daytime polar cusp region. In contrast, quiet time ion beams have a maximum occurrence frequency in the premidnight sector. Ion beams are observed primarily above 5000 km, with a frequency increasing with altitude up to the satellite apogee at 8000 km. During disturbed times, ion beams are a persistent phenomenon, mainly confined to the dusk sector, while conical distributions are observed uniformly in local time with a frequency that increases steadily in altitude. The results of this study, which are shown to be consistent with previous surveys of upward flowing ions if no distinction is made between conical and field‐aligned distributions, provide information relating to auroral ion acceleration processes.