Theoretical modeling reveals ion-acoustic instability links field-aligned current impulses to Pi1 noise bursts in the topside ionosphere, highlighting mechanisms driving pulsed electron precipitation.
The estimated densities of local field‐aligned currents related to nighttime substorm onset or magnetic impulse events at cusp latitudes may exceed the threshold for the excitation of high‐frequency turbulence in the topside ionosphere. The evolution of an ion‐acoustic instability is shown to lead to quasi‐oscillations around the saturation level. Consequent variations in anomalous conductivity will result in pulsed electron precipitation and noise generation in the Pi1 band. This proposed mechanism gives a natural interpretation to the experimentally observed coupling between localized magnetic disturbances, electron precipitation/acceleration, and bursts of high‐frequency ULF noise. The alternative interpretations based on mechanisms of ion cyclotron instability stimulation and ionospheric Alfven resonator excitation can be applied only under specific plasma conditions.
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Пилипенко et al. (1999) studied this question.
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