The literature on values of the effective recombination coefficient α of electrons between heights of 50 and 150 km has been critically examined. It is found that, during auroral events at night, it may be represented by the expression α = 4.30×10−6 exp (−2.42×10−2h) + 8.16×1012 exp(−0.524 h), where α is in cm −3 s−1 and h is in kilometers. During a wide variety of phenomena, including polar cap absorption, sudden phase anomalies, solar proton events and solar flares, the expressions α = 652 exp(−0.234 h) (night) and α = 0.501 exp(−0.165 h) (day) are reasonably representative between 50 and 100 km. No values are available above 100 km. The above values are certainly not reliable to within a factor of 2, and in some cases not even to within an order of magnitude.

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Experimental and theoretical values for precipitated electron and proton fluxes in the area of the South Atlantic geomagnetic anomaly are reviewed. Observations of airglow which have been reported in the literature suggest that there is no enhancement in the Brazilian region, though there may be some in the southeastern part of the Atlantic area. There is evidence from various types of observations that the electron density in the ionosphere is greater over the South Atlantic than at comparable places elsewhere, especially during magnetic disturbances, and similarly the ion density shows enhanced values. Electron and neutral temperatures may also be higher than normal in the anomalous region. Observations are required in all these fields, coordinated with particle flux measurements from rockets and satellites in the area, to confirm the reality of the effects and their relationship to particle precipitation.

The high-energy background radiation in the South Atlantic Anomaly makes it difficult to measure the fluxes and spectra of the low-energy particles with any degree of certainty, and as a result no values for the energy range below 30 keV are to be found in the literature. We have found that the flux of lowenergy ions is much smaller than that of the electrons. This has enabled us to use the low-energy ion detector on AE-C to monitor the high-energy background and to correct the response of the low-energy electron detector for this. The electron spectra can be represented by a power law in the range 0.2-26 keV, with the spectral index close to -1. Maps are shown of downward energy flux in this range over the South Atlantic Anomaly. The mean energy flux carried by electrons in the middle of the anomaly is found to be about 3 x 10 -3 erg cm -2 s -• and may reach 5 times this value on occasions. A surprising result is that this energy flux decreases as Kp increases.

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