LATITUDINAL STRUCTURE OF A CORONAL MASS EJECTION INFERRED FROM ULYSSES AND GEOTAIL OBSERVATIONS

We present the first observations of a CME by two spacecraft separated substantially in heliographic latitude. Ulysses and Geotail both see similar features in the plasma and magnetic field parameters during an interval in which Geotail is located in the deep magnetosheath (>150 R(E)) and Ulysses is located in the solar wind at 5 AU, similar to 20 degrees S of Geotail, and similar to 51 degrees W (in the direction of solar rotation) of Geotail. Based on the similarity in plasma and magnetic field parameters and similar inferred ejection times from the Sun for both features we argue that the same CME is observed by both spacecraft. The portion of the CME observed by Ulysses is traveling much faster than the portion observed by Geotail. Thus the CME has significant latitudinal structure since at any given time the high latitude portion of the CME extends much further out in radial distance. Furthermore, this implies that a simple calculation of the arrival time of a CME at the Earth may not be done if the observing spacecraft is located substantially away from the ecliptic plane.