Ground-based Detection of Ionospheric Density Modulations due to Alfven waves using AMISR and Ground-Based Optics at Poker Flat, Alaska

Sri International, Menlo Park CA

Investigators

Abstract

An emerging explanation for the highly dynamic and very small-scale structure observed in the aurora is that it results from feedback between ionospheric density modulations and resonant Alfven waves. This model is founded on the combination of two mechanisms: the ionospheric Alfven resonator (IAR) and the ionospheric feedback instability (IFI). Definitive observational confirmation of the model has not yet been possible. This is a four-year project to provide unprecedented experimental evidence related to these mechanisms in the ionosphere. It will utilize the advanced capabilities of the Advanced Modular Incoherent Scatter Radar (AMISR) at the Poker Flat Rocket Range (PFRR) to overcome the space-time ambiguities prevalent in existing experimental data. Specifically, the full pulse-by-pulse beam steering capability of AMISR together with advanced signal processing techniques will be used to obtain vertically and horizontally resolved frequency domain measurements of perturbations in ion velocity and electron density, with a Nyquist frequency of 100 Hz. Additional measurements of ion drift velocities at a larger spatial scale will be provided by the SuperDARN radar network and video rate intensified imaging at PFRR will be used to determine the morphology of prompt emitting auroral forms associated with Alfvenic activity. The observations will be compared with IAR/IFI simulations tuned to the prevailing conditions, in order to test for association with Alfven waves. The research project will focus on answering the following three specific science questions: What are the observed vertical and horizontal profiles of periodic ion velocity and density modulations in the frequency domain, and are these compatible with the IAR/IFI model? Does the thin slab model of the conducting ionosphere significantly distort modeling of the IFI? In the event that the IAR/IFI model signatures are not present, which of the model assumptions are not realized? In addition, to answering these important science questions, the project has significant broader impacts as well. It will develop and test advanced techniques for the AMISR facility and will demonstrate its use as a plasma structure spectrum analyzer, covering the ELF frequency range. In addition, it represents a good example of interdisciplinary science: testing a theoretical model popular in the magnetospheric community with the techniques and detailed observations of the ionospheric community.