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Energetic electron precipitation as a source of ionization in the night-time D-region over the mid-latitude rocket range, South Uist

1973; Elsevier BV; Volume: 35; Issue: 5 Linguagem: Inglês

10.1016/0021-9169(73)90066-4

1878-593X

M. P. Gough, H. L. Collin,

Geomagnetism and Paleomagnetism Studies

Two Petrel rockets were launched from South Uist, Scotland, one at a magnetically quiet time and the other during a magnetic storm. At the quiet time only low precipitation fluxes ~4 electrons cm−2 ster−1 sec−1 >40 keV were observed while during the storm these fluxes rose to as high as 3 × 105 electrons cm−2 ster−1 sec−1 >40 keV. These precipitating energetic fluxes produced <25 per cent of the total night-time D-region ionization at the magnetic quiet time but the storm time precipitation accounted for 99 per cent of the total ionization. A clear correlation is found between particle flux and magnetic activity Kp summed over 24 hr for 13 rockets launched from South Uist. This is used with the abundance of the different levels of activity to show that precipitating energetic electrons become a dominant source of the night-time D-region on 15 ± 11 per cent of the nights at solar minimum rising to 35 ± 20 per cent of the nights at solar maximum. When the magnetic field line passing through South Uist lies inside the plasmasphere, the electron precipitation continues up to 312 days after magnetic storms, in agreement with measured trapping lifetimes in the ‘electron slot’ of the trapping region.