Coincident particle observations from AE‐C and ATS 6 during the October 28, 1977, geomagnetic storm

Abstract

Ion and electron energy spectra (<30 keV) were recorded simultaneously by the AE‐C (at ∼400‐km altitude) and ATS 6 (at 6.63 RE) spacecraft during the intense geomagnetic storm of October 28, 1977 (Kp → 7+). Observations were acquired in the evening sector, when the two spacecraft were nearly on the same L shell. The orbit of AE‐C provides wide longitudinal coverage of the auroral oval, whereas ATS 6 remains relatively stationary near the equatorial plane. An unusual particle injection event that was characterized by a series of periodic (∼12 min) bursts of electrons was observed by ATS 6. During this time a variety of phenomena could be identified in the AE‐C particle data, including a widespread low‐energy ‘inverted V’ that extended over 1‐1/2 hours of local time. Distinct from this region are precipitating electrons which have monoenergetic peaks of variable intensity. These electron spectra are similar to those normally observed coincident with discrete arc aurora. The coincident electron energy spectra acquired by AE‐C and ATS 6 match well above 5 keV. The spectra of electrons peak near 1 keV at ionospheric altitudes (typical of this event), whereas no peaks in energy appear at synchronous altitude.