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Mauk 1982
Mauk, B.H. (1982). Helium resonance and dispersion effects on geostationary Alfven/ion cyclotron waves. Journal of Geophysical Research 87: doi: 10.1029/JA080i011p09107. issn: 0148-0227.

To understand observed structure and growth patterns of geostationary Alfven/ion cyclotron waves, the properties of the hot proton cyclotron instability within a helium rich plasma are explored here. This exploration proceeds with an examination of the net linear wave amplifications that result as a wave propagates through the magnetic gradients of a realistic magnetic field model (linearity is discussed and justified). By taking care in generalizing a single pass model to a multiple pass system, the following conclusions have been reached: (1) The basic structure of the frequency gap that is observed close to the helium cyclotron frequency can be explained by the 'stop-gap' dispersion effect; however, the helium cyclotron resonance effect contributes to the gap formation leading to He+ ion energization. (2) The presence of the magnetic gradients virtually insures that helium ion energization. (by means of the low frequency wave branch only) is the inevitable consequence of the wave generation process. (3) The energized helium ions will sparsely populate a broad range of geomagnetic latitudes (¿15 degrees) but will be concentrated strongy within several (2--4) degrees of the geomagnetic equator. (4) The presence of low percentages of helium ions is most likely to suppress the wave generation process (ATS 6 satellite observations support this conclusion for a portion of the wave spectrum).

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Journal
Journal of Geophysical Research
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American Geophysical Union
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