Scientific Colloquium
April 27, 2007

"Global Auroral Imaging During the Polar Mission Era "

The northern and southern lights or auroras are the most evident and arguably most beautiful manifestation of Space Weather on our Earth.  Auroral current flowing into and through Earth’s upper atmosphere generates large voltage spikes on long transmission lines that impact the operation of electrical power and telephone companies for example.  In addition to aiding our understanding of the physics of auroral generation, the auroral ovals magnetically map to the critical regions of our near Earth space or ‘magnetosphere’ that is dominated by Earth’s magnetic field.  In effect, the Earth’s atmosphere can be used as a global sized detector revealing what is happening in these far-flung regions of space.  The pattern of auroral luminosities or morphology is used to determine the auroral phases of growth, onset, expansion, and recovery signaling the release of energy stored in Earth’s magnetic tail and originally acquired from the solar wind.  Brightenings near local noon in the dayside auroral oval signal the arrival of dynamic pressure shocks in the solar wind at the interface to the magnetosphere.  The intensities and ratios of the visible or far ultraviolet auroral emissions are used to determine the energy flux and characteristic energy of the precipitating auroral particles.  Thus a complete temporal history of the energy flow from the solar wind to storage in the magnetosphere and eventual deposition in the atmosphere is obtained helping in our understanding of the complete solar wind, magnetosphere, ionosphere and atmosphere as a complete system.  The paper will present our new understanding of the auroras acquired during the more than 11 year mission of the Polar spacecraft.

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