Peak‐Height Distribution of Equatorial Ionospheric Plasma Bubbles: Analysis and Modeling of C/NOFS Satellite Observations.

We present the first observational determination of statistical limits on the rise of equatorial plasma bubbles as a function of solar flux. We analyzed in situ electron density data collected onboard the Communications/Navigations Outage Forecasting System (C/NOFS) satellite to characterize the distribution of peak altitudes of equatorial ionospheric plasma bubbles. We first describe our algorithm for detecting ionospheric irregularities within the observations and then use a series of statistical simulations to identify and compensate for the sampling biases inherent in observations from a single satellite in a low‐inclination elliptical orbit. The simulations also confirmed that space‐based orbital platforms such as the C/NOFS satellite undersample the existing irregularities in the ionosphere and provide a measure of the satellite's inefficiency in observing those naturally occurring irregularities. In deducing the variation of the peak‐height distributions of the irregularities with solar activity, we find that the median maximum height of the bubbles increases linearly from about 490 km at the solar minimum (2008) to 740 km during the (2014) solar maximum in the longitude sector 80°W–10°E. The results will be valuable for the development of improved scintillation mapping models for both real‐time and postprocessing applications. We also confirm our observational findings with modeling results from a physics‐based model, allowing us to identify field‐line‐integrated Pedersen conductance as the key determinant of terminal bubble altitude: a bubble will cease to rise further when the conductance inside the bubble is equal to that of the background ionosphere. Plain Language Summary: In this study, we take a new approach of data analysis in determining the peak heights at the magnetic equator, or the peak apex heights, of the equatorial ionospheric irregularities from the ion‐density observations made by a sensor onboard Communications/Navigations Outage Forecasting System (C/NOFS) satellite. The variation of these peak‐height distributions with solar activity is studied over the years of operation of C/NOFS mission (2008–2014). We use numerical simulations to confirm the approach used in determining the peak‐height distributions from the observed height distributions and, in the process, discovered that the efficiency of C/NOFS for detecting equatorial irregularities was less than 50% throughout the solar cycle. We find that the median maximum height of the equatorial ionospheric irregularities increases linearly from about 490 km at the solar minimum to 740 km during solar maximum in the longitude sector 80°W–10°E. The results will be valuable for the development of space‐weather forecasting models. We also confirm the observational findings presented in this paper with modeling results from a physics‐based model. In the model, we identify conductance as the key parameter controlling the peak heights of the equatorial irregularities. Key Points: Quantitative distributions of equatorial plasma bubble peak apex heights as a function of solar fluxField‐line‐integrated Pedersen conductance as the key determinant of terminal bubble altitude of the equatorial plasma bubbles using the physics‐based modelEstimation of the meridional extent of scintillation activity as a function of solar flux [ABSTRACT FROM AUTHOR]