C/NOFS Satellite Observations of Traveling Ionospheric Disturbances and Associated Irregularities during the Start of the New Solar Cycle

The ambient equatorial ionosphere during the start of the new solar cycle is studied with the Communication/Navigation Outage Forecasting System (C/NOFS) satellite, which was launched in April 2008 into an equatorial orbit at altitudes between 400 and 850 km. The ionospheric F-region height increased as the solar cycle started, such that the satellite at perigee is sometimes below the peak. A longitudinal dependence is apparent in the height of the F-region peak close to the magnetic equator. We show agreement between the C/NOFS observations and the results from the Physics Based Model (PBMod). In addition, large scale horizontal waves with a wavelength of 700 to 1,000 km seem to appear more frequently than during the deep solar minimum. Relationship between these waves and the lower atmosphere is explored. Small scale irregularities, i.e. equatorial plasma bubbles (EPBs), are superposed on top of these large-scale waves. The EPBs periodicity is often the same as that of the underlying long wavelength structures, which leads us to conjecture that they are related, and that the EPBs are seeded by the long-scale waves as suggested by Tsunoda and other authors.