Plasma Structure Decay Rates in the Equatorial Ionosphere Are Strongly Coupled by Turbulence

Equatorial plasma irregularities in the ionospheric F‐region proliferate after sunset, causing the most apparent radio scintillation “hot‐spot” in geospace. These irregularities are caused by plasma instabilities, and appear mostly in the form of under‐densities that rise up from the F‐region's bottomside. After an irregularity production peak at sunset, the amplitude of the resulting turbulence decays with time. Analyzing a large database of irregularity spectra observed by one of the European Space Agency's Swarm satellites, we have applied a novel but conceptually simple statistical analysis to the data, finding that turbulence in the F‐region tends to decay with a uniform, scale‐independent rate, thereby confirming and extending the results from an earlier case study. We find evidence for two regimes, one valid post‐sunset (1.4 hr decay rate) and one valid post‐midnight (2.6 hr). Our results should be of utility for large‐scale space weather modeling efforts that are unable to resolve turbulent effects.