Radiation near 2f(p) and intensified emissions near f(p) in the dayside and nightside auroral region and polar cap

This paper reports the discovery in the DE 1 data of propagating radiation near 2f(p) (the H component) and relatively intense electromagnetic waves near f(p) with fields typically less than or similar to 1 mV m(-1) (the PF or plasma frequency component) on both the dayside and the nightside of Earth. These emissions are observed at auroral and polar cap latitudes for radial distances ranging from 2.5 to 4.5 R(E). The H component is unique in that no other 2f(p) emissions are known to be generated where the electron gyrofrequency f(g) exceeds 2f(p). Since existing theories for 2f(p) radiation assume f(g)/f(p) < 1, new theories will be required to explain the A component. The PF waves near f(p) are electromagnetic, but with large ratios E/cB similar to 20. On the basis of cold plasma theory, the wave frequencies and the ratios E/cB, the PF component plausibly consists of z-mode and/or whistler mode waves near f(p), presumably driven by an electron instability. The H emissions have modest bandwidths of similar to 50% at frequencies ranging from 5 to 20 kHz. Grounds for interpreting the A component as emissions generated near 2f(p) are provided by the very good frequency tracking of the PF and H components and typical frequency ratios near 2.0. Strong evidence exists that part of the A component is propagating, electromagnetic radiation, based on propagation effects and spin modulation patterns. However, no magnetic signals have yet been detected for the H component, so that it could be partly electrostatic. Cold plasma theory and the observed wave characteristics favor interpreting the H component as composed of o mode and/or a mode signals. Combining the DE 1 observations with rocket observations, it is predicted that the much more intense Langmuir-like fields observed in the low altitude auroral zones should also generate observable 2f(p) radiation. This prediction should be testable using Polar and future rocket flights. Directions for future research are also described.