Summary form only given, as follows. When magnetic field lines aresufficiently stretched during the substorm growth phase the earthwardE×B ion drift velocity can become comparable to the gyrationvelocity. Under these conditions inertial currents can become quiteimportant. Using the Rostoker-Skone magnetic field model and a crosstail electric field the authors find that cold (<=200 eV) O+ ions injected from the ionosphere into the equatorial plane athigh latitudes will drift eastward at radial distances less than -10 RE, due to inertial effects and westward at distanced closerto the Earth due to magnetic drift. The inertial eastward drift givesrise to a current which in terms of J×B is consistent with theconvective deceleration of the earthward drift velocity due to highervalues of B. Similarly momentum balance also requires that theconvective acceleration of the westward drift velocity consistent with atailward inertial current. Therefore, an equatorial current wedge systemwith an eastward and tailward current naturally arises from the iondynamics and a simple, yet realistic magnetic field model. Morecomplicated current systems can be modelled by adding a radial electricfield structure. For example, a weak electric field gradient leads to anearthward inertial current that may dominate the tailward current justdiscussed. These current structures will be examined for different crosstail electric field values and magnetic field configurations in order tohopefully shed some light on the substorm onset process. Small scalestructures related to the phase effects of the oxygen ions will also bediscussed
展开▼
