Nonthermal components of low energy electrons in the ionospheric E and F region.

The energy distribution of very low energy electrons (0.16-1eV) in the ionospheric E and F region was measured during a rocket flight on 22 January, 1978 above a midlatitude station (Kagoshima Space Center, Japan). The experiment confirmed previous results obtained from a rocket observation made in 1976.Two ionospheric regions were found where there appeared an enhanced high energy tail of thermal electrons. One was in the midst of a region of the elevated Te which has been previously reported in conjunction with the Sq focus anomaly. Another region started at 135km and vanished at an altitude of ≈210km. In the first region, large electron temperature deviations from the neutral temperature were found and an enhanced high energy tail appeared in the electron energy distribution. The electron heating associated with this was most intense at the height of 107km, and gradually decreased toward the height of ≈130km where both the electron temperature and the excess high energy tail became small. In the second region, excess electrons in the high energy tail appeared starting at 135km, became most intense at the height of ≈150km and gradually decreased toward 210km.We suggest that the anomalously elevated electron temperature and the enhanced high energy tail in the first region was generated locally by some dynamo current-related mechanism which is different from Joule heating. We also suggest that excess high energy tail found in the second region is also related to ionospheric currents.