Study of the electron density in the high latitude ionosphere with incoherent scatter radars and Swarm satellites
Date
2023-09-14
Authors
Journal Title
Journal ISSN
Volume Title
Publisher
ORCID
0009-0003-3688-7109
Type
Thesis
Degree Level
Masters
Abstract
Despite century-long efforts in assessing the electron density distribution in the Earth’s ionosphere
and significant progress in identification of its major features, there are still many uncertainties
with respect to the solar cycle’s seasonal and diurnal trends at various latitudes. Knowledge of
these variations is needed for robust forecasting of the state of the ionosphere for the operation of
practical radio systems, for example communication via high frequency radio waves.
This thesis utilizes data from the incoherent scatter radar (ISR) at Poker Flat (Alaska, USA)
to assess the diurnal and seasonal variations of three parameters of the ionospheric F2 region, the
peak density, the height of the peak, and the thickness of the layer. These parameters are assessed
for relatively high solar activity in 2014, and relatively low solar activity in 2016. Daytime electron
densities were found to be largest during winter and spring and nighttime electron densities were
found to be smallest in winter. Electron densities during the higher solar activity year were found
to be greater than those during the lower solar activity year by a factor of 2-5, depending on the
time of day, as expected. Details of the diurnal variations in electron density for various seasons
are further discussed.
ISR electron density data are also used for the validation of electron density measurements
from Langmuir probes onboard the Swarm satellites in the topside ionosphere (~500 km). This
work is an expansion of previous studies that use a different mode of ISR operation and a different
approach to both ISR and Swarm satellite data handling. In addition to observations over Poker
Flat (geographic latitude of ~60° N), observations over Resolute Bay, Canada at extreme high
latitudes of ~80° are also considered. It is shown that, overall, the ratio of Swarm electron density
measurements to those measured by ISRs is ~0.5-0.6 and that smaller ratios are observed at larger
electron densities, usually during the daytime. At low electron densities less than 3∙1010 m-3
, the
ratios are typically greater than 1, indicating an overestimation effect. The overestimation effect is
stronger at night and at higher altitude. It is also more evident during lower solar activity when the
electron density in the topside ionosphere is smaller. The conclusions on the electron density
underestimation and overestimation by the Swarm Langmuir probes are overall consistent with
previous reports, but this thesis confirms that these effects also occur at high latitudes.
Description
Keywords
Ionosphere, Incoherent scatter radar, Swarm, Electron density
Citation
Degree
Master of Science (M.Sc.)
Department
Physics and Engineering Physics
Program
Physics