Onset conditions of bubbles and blobs: A case study on 2 March 2009

摘要

The onset conditions for bubbles and blobs are investigated by analyzing the Communication/Navigation Outage Forecasting System satellite/Coupled Ion-Neutral Dynamics Investigation instrument data on 2 March 2009. A series of bubbles and blobs are detected in the longitude regions 180°-240°E and 240°-295°E, respectively. Bubbles are detected at low latitudes before midnight. Blobs are detected at 14°-25° magnetic latitude, between 2300 and 0500 LT in the altitude range of 400-480 km. The distinguishing feature in the longitude region where bubbles are detected is an enhancement in background plasma density with respect to that in the longitude region where bubbles are absent. Blobs are detected in a longitude region where fluctuations in the plasma density exist over a broad latitude range. The total ion density (and O~+ density) and H~+ density perturbations are in-phase at the locations of bubbles and out of phase at the locations of blobs. Bubbles are not detected in the longitude region where blobs are detected. The different characteristics of bubbles and blobs and their creation under different geophysical conditions indicate that creation of blobs need not be associated with bubbles.