The earth resides in a flow of ionized and magnetized gases emanating from the sun called the Solar Wind. The earth and its magnetic field divert the flow of this supersonic wind, and the confined space in which the earth's magnetic field and ionized gases reside is called the magnetosphere, that extends 10-12 earth radii in the direction of the sun, and a hundred or more earth radii in the antisolar direction. At the magnetosphere boundary the interaction with the solar wind generates electric potential differences of hundreds of kilovolts, and currents of millions of amperes flow down magnetic field lines, through the polar ionosphere, and back out to the solar wind boundary. The currents deposit large amounts of energy in the ionosphere, and set up large waves in the ionosphere itself (hydromagnetic waves) and in the neutral atmosphere (atmospheric gravity waves). Using the incoherent scatter radar at Sondestromfjord, Greenland, and auxillary magnetometer and riometer measurements and auroral images, basic studies of both hydromagnetic and gravity waves and their relationship to ionospheric currents, particle precipitation and ionospheric heating will be carried out. These studies will provide data on the physics of the coupling of the solar wind to the magnetosphere-atmosphere in the polar regions.
