Imaging of USTEC-derived field of velocity of TEC redistribution

Study of ionosphere dynamics is one of the key issues of geophysics. During geomagnetic storms intense disturbance electric fields originating from the magnetosphere-ionosphere interaction lead to drastic changes in the ionosphere vertical total electron content. Here we propose a method for calculation of regional maps of velocities of total electron content isolines movement (TECIM) using USTEC maps (http://www.ngdc.noaa.gov/stp/IONO/USTEC/home.html) with a high temporal and spatial resolution. Using this technique allows us to obtain additional information about the ionosphere plasma redistribution. This is of particular interest during storms. Our results illustrate significant distinctions of the dynamics of the ionization redistribution under geomagnetically quiet and disturbed conditions. During quiet time periods the velocity of the night ionization changes far from the terminator is much smaller than the velocity of the terminator. On the contrary, during geomagnetically disturbed periods fast changes of the spatial TEC distribution essentially exceed the terminator velocity value. Thus, during the main phase of geomagnetic storm on 8 November 2004 (maximum level Kp = 9), when during local nighttime a large-scale ionization redistribution was observed, the velocity of TECIM reached 1000 m/s. Such changes are determined by the spatial configuration and the intensity of the electric field.