Fine structure of the ionospheric plasma bubbles observed by the OI 6300 and 5577 airglow images Original Research Article

Simultaneous measurements of the ionospheric airglow OI 630.0 nm and OI 557.7 nm emissions have been carried out by means of an all-sky CCD imager system at Cachoeira Paulista, since October 1998. During a developed phase of plasma depletion (bubble) in the equatorial anomaly region, both emissions show intensity depletions along the geomagnetic North—South direction, and also bifurcation of the bubbles. It is frequently observed that the OI 557.7 image shows more fine structure of the bubble than the OI 630.0. The amplitude of the intensity depletion was also larger for OI557.7 than OI630.0. This might be due to the difference in life time between the O(1D) and O(1S) states, which are responsible for the OI 630.0 and OI 557.7 emissions, respectively. The O(1D) might be affected by thermal relaxation and diffusion processes before the radiative transition.