What parts of broadband spectra are responsible for ion conic production?

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Abstract
We investigate ion energization and ion conic production by broadband electric field fluctuations. The roles played by resonant fluctuations (which can satisfy the cyclotron resonance condition), and nonresonant fluctuations well removed from the ion gyrofrequency, are compared. We show that in the resonant case the mean ion energy increases essentially linearly with time, while in the nonresonant case this energy rapidly reaches a maximum. Using observed electric spectra we find that nonresonant energization due to high spectral densities at frequencies well below the ion gyrofrequency may be important for the generation of some heavy ion conics, but confirm that heating by resonant electric fluctuations is sufficient to explain most ion conics.