Investigation of Ionospheric Small-Scale Plasma Structures associated
with Particle Precipitation
Abstract
We investigate the role of auroral particle precipitation in small-scale
(below hundreds of meters) plasma structuring in the auroral ionosphere
over the Arctic. To the scope, we together analyse data recorded by an
Ionospheric Scintillation Monitor Receiver (ISMR) of Global Navigation
Satellite System (GNSS) signals and by an All-Sky Camera located in
Longyearbyen, Svalbard (Norway). We leverage on the raw GNSS samples
provided at 50 Hz by the ISMR to evaluate amplitude and phase
scintillation indices at 1 s time resolution and the Ionosphere-Free
Linear Combination at 20 ms time resolution. The simultaneous use of the
1 s GNSS-based scintillation indices allows identifying the scale size
of the irregularities involved in plasma structuring in the range of
small (up to few hundreds of meters) and medium-scale size ranges (up to
few kilometers) for GNSS frequencies and observational geometry.
Additionally, they allow identifying the diffractive and refractive
nature of the found fluctuations on the recorded GNSS signals. Six
strong auroral events and their effects on plasma structuring are
studied. Plasma structuring down to scales of hundreds of meters are
seen when strong gradients in auroral emissions at 557.7 nm cross the
line of sight between the GNSS satellite and receiver. Local magnetic
field measurements confirm small-scale structuring processes coinciding
with intensification of ionospheric currents. Since 557.7 nm emissions
primarily originate from the ionospheric E-region, plasma instabilities
from particle precipitation at E-region altitudes are considered to be
responsible for the signatures of small-scale plasma structuring
highlighted in the GNSS scintillation data.