Browsing by Author "Ossakow, S. L."
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Item Restricted Evolution of equatorial ionospheric bubbles during a large auroral electrojet index increase in the recovery phase of a magnetic storm(American Geophysical Union, 2006-02-10) Keskinen, M. J.; Ossakow, S. L.; Fejer, B. G.; Emmert, JohnWe present a model and observations of the evolution of equatorial ionospheric bubbles during a large auroral electrojet (AE) index increase in the recovery phase of a geomagnetic storm. Using a three‐dimensional time‐dependent numerical simulation model, we find, for the 19–21 October 1998 storm, that the equatorial bubble evolution is different during storm time as compared to quiet time conditions. We have found that the storm time vertical drift in conjunction with reduced off‐equatorial E region shorting is the primary mechanism that distinguishes the large AE increase recovery phase storm time evolution from the quiet time case. Comparison of the simulation model with ground‐based storm time radar observations is made.Item Restricted Three-dimensional nonlinear evolution of equatorial ionospheric spread-F bubbles(American Geophysical Union, 2003-08-26) Keskinen, M. J.; Ossakow, S. L.; Fejer, B. G.Using numerical simulation techniques, we present the first study of the three‐dimensional nonlinear evolution of an equatorial spread‐F bubble. The background ionosphere used to initialize the bubble evolution is computed using a time‐dependent first‐principles equatorial plasma fountain model together with a prereversal enhancement vertical drift model. We find that finite parallel conductivity effects slow down both the linear and nonlinear bubble evolution compared to the two‐dimensional evolution. In addition we find that bubble‐like structures with extremely sharp density gradients can be generated off the equator at equatorial anomaly latitudes in agreement with recent observations.