Plasma Structure Decay Rates in the Equatorial Ionosphere are Strongly
Coupled by Turbulence
Abstract
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 plasma 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 in the
process that post-sunset turbulence in the F-region tends to decay with
a uniform, scale-independent rate at night, thereby confirming and
extending the results from earlier case studies. Our results should be
of utility for large-scale space weather modelling efforts that are
unable to resolve turbulent effects.