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A burst of X rays was observed at balloon altitude over Alaska with the onset of a sudden commencement geomagnetic storm at 0146 UT on June 27, 1960. The electron bombardment of the upper atmosphere that gave rise to the X rays occurred on a large scale, ionospheric absorption coincident with the X‐ray burst being observed by riometers in Alaska, Sweden, and Norway.

Statistical studies have been made of the diurnal and latitudinal occurrence and intensity patterns of ELF, VLF, and LF whistler‐mode noise emissions observed with the Alouette 2 satellite. The ELF emissions occur characteristically below 1 kHz, are peculiar to the daylight hours, and show a peak in average intensity in the invariant latitude range of 50°–70°. In the VLF range, broadband emissions extending upward from the LHR frequency show a maximum average intensity near local noon and a Λ of about 77°. Along the auroral oval toward earlier and later hours, they show a decreasing intensity. The apparent high‐frequency end of this emission band extends upward from 100 kHz to the local fN or fH frequency in the LF range. The LF emissions were studied at a fixed frequency of 200 kHz, and maximum intensities were found along the day and evening portions of the auroral oval. This type of noise also shows a latitude dependence on Kp similar to that of the auroral phenomena. A second region of peak intensity, at about the position of the nighttime plasmapause, appears in the LF statistical results, but a complete study has not been made of that region.

Cosmic noise absorption coinciding with the sudden commencement of geomagnetic storms has been studied for 71 SC events from the data recorded at 25 riometer stations at or near the auroral zone during the period July 1958‐December 1960. The greatest absorption was registered at stations near the central line of the auroral zone. The effect was observed simultaneously on the day and on the night side of the earth. This type of absorption was earlier found to be associated with bremsstrahlung X rays created by electrons entering the lower ionosphere. The source of these electrons has not been definitely established by the present study. Although the data tends to favor a source outside the earth's magnetosphere, no definite conclusion is possible because of the present uncertainties concerning the trapped radiation belts.

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