Auroral Radio Emissions: A Window Into Electron Acceleration Processes

点击翻译按钮获取中文摘要

The Northern Lights or aurorae result when energetic particles interact with the atmosphere ? producing a colorful sight in the night sky. The Arctic region near the North Pole is a prime location for viewing aurorae. This project is a follow-on to an NSF funded program that deployed and calibrated a receiver array in Toolik Lake, Alaska. This instrumentation will be used to view the aurorae and make new discoveries about how they are created. Graduate and undergraduate students will be trained and the scientific datasets will be shared with the public.A significant manifestation of high-latitude electromagnetic energy and particle flows is the terrestrial aurora which involves many acceleration processes affecting electrons and ions. These processes occur in both the magnetosphere and the ionosphere and are a key component of magnetosphere-ionosphere (M-I) coupling. Radio emissions from the accelerated auroral electron beams, with their complicated temporal and spatial variations, provide a window into the accelerated electron distributions and the processes that produce them. Auroral Medium Frequency Burst (MFB) emissions are especially promising in this regard because they are associated with substorm expansion arcs and exhibit structure on a range of time scales overlapping with those of Alfvenically accelerated suprathermal electron bursts and other phenomena such as flickering aurora. MFB is, however, relatively poorly understood: its source altitudes is not known, and although a mechanism has been proposed that suggests a connection to Alfvenic aurora, it has not been conclusively confirmed by observations. The proposed experiments, which will answer these and other outstanding questions about MFB and auroral radio emissions, are critical steps toward using MFB and its time and frequency structure as a diagnostic of auroral acceleration and nonlinear wave processes, to answer key questions about the temporal and spatial dynamics of these processes in the ionospheric context as well as their relation to larger dynamical processes such as storms and substorms.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.