Statistical Comparison of Auroras in Northern and Southern Hemispheres

Johns Hopkins University, Baltimore MD

Investigators

Abstract

Auroral displays are an optical manifestation of the Sun-Earth connection, and studying the aurora provides understanding of this connection and their coupling. Owing to geophysical constraints (~2/3 of aurora in the southern hemisphere are above the ocean), there is a lack of information on the southern hemisphere aurora. Current knowledge of the aurora is based primarily on observations made in the Northern Hemisphere. This has prevented full understanding of the magnetosphere-ionosphere as a whole system. With the advent of satellite-based particle and optical imaging and more observations made in the southern polar regions, there is mounting evidence suggesting that auroras are not always hemispherically symmetric and/or conjugate, especially under certain conditions and certain types of aurora. Therefore, studying the aurora from both hemispheres can provide much more information about the polar wind-magnetosphere-ionosphere coupling than any single hemisphere does. This type of approach is essential because past studies have either relied on global auroral images from a single hemisphere or on combined particle data from both hemispheres. The expected results will be made available through the JHU/APL (Johns Hopkins University Applied Physics Laboratory) Auroral Particles and Images Team web site, which serves up a variety of auroral data and models, including the OVATION Prime, to the space physics community. Furthermore, the expected result can be used to update the OVATION Prime auroral model. The goal of this proposal is to study hemispheric symmetries and asymmetries of the large-scale north and south auroral intensity to improve current knowledge of the solar wind-magnetosphere-ionosphere coupling. Specifically, the following questions are to be addressed as science objectives: (1) Are there relationships between the IMF (Interplanetary Magnetic Field) and the north-south asymmetry of the aurora? (2) Does the southern aurora respond to sunlight in a similar manner as the northern aurora does? and (3) Is there a relationship between the geomagnetic field and auroral intensity? This project consists of analyzing FUV (far-ultraviolet) auroral images acquired by NASA's TIMED/GUVI from both hemispheres. It will be carried out using (1) a large number (~6 years' worth) of near-global auroral images in the FUV band with unprecedented spectral and spatial resolution not only from the Northern Hemisphere but also from the lesser-known Southern Hemisphere and (2) the quantitative inversion of images made at certain wavelengths which can reveal characteristics of these precipitating particles such as their energy and the power they deposit in the upper atmosphere. This method has been tested in recent case studies involving GUVI data and have demonstrated the accuracy and utility of these inversions. 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.