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 radia tion near 2f(p) (the H component) and relatively intense electromagnet ic 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 t he nightside of Earth. These emissions are observed at auroral and pol ar cap latitudes for radial distances ranging from 2.5 to 4.5 R(E). Th e 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). Sinc e existing theories for 2f(p) radiation assume f(g)/f(p) < 1, new theo ries 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 t he 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 rang ing from 5 to 20 kHz. Grounds for interpreting the A component as emis sions generated near 2f(p) are provided by the very good frequency tra cking 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 modul ation patterns. However, no magnetic signals have yet been detected fo r the H component, so that it could be partly electrostatic. Cold plas ma theory and the observed wave characteristics favor interpreting the H component as composed of o mode and/or a mode signals. Combining th e DE 1 observations with rocket observations, it is predicted that the much more intense Langmuir-like fields observed in the low altitude a uroral zones should also generate observable 2f(p) radiation. This pre diction should be testable using Polar and future rocket flights. Dire ctions for future research are also described.