Abstract. We analyse reprocessed electron density profiles and total
electron content (TEC) profiles of the ionosphere in September 2008 (around
solar minimum) and September 2013 (around solar maximum) obtained by the
Constellation Observing System for Meteorology, Ionosphere, and Climate
(COSMIC/FORMOSAT-3). The TEC profiles describe the total electron content
along the ray path from the GPS satellite to the low Earth orbit as function
of the tangent point of the ray. Some of the profiles in the magnetic polar
regions show small-scale fluctuations on spatial scales <50 km. Possibly
the trajectory of the tangent point intersects spatial electron density
irregularities in the magnetic polar region. For derivation of the morphology
of the electron density and TEC fluctuations, a 50 km high-pass filter is
applied in the s domain, where s is the distance between a reference
point (bottom tangent point) and the tangent point. For each profile, the
mean of the fluctuations is calculated for tangent point altitudes between
400 and 500 km. At first glance, the global maps of ΔNe
and ΔTEC are quite similar. However, ΔTEC
might be more reliable since it is based on fewer retrieval assumptions. We
find a significant difference if the arithmetic mean or the median is applied
to the global map of September 2013. In agreement with literature,
ΔTEC is enhanced during the post-sunset rise of the equatorial
ionosphere in September 2013, which is associated with spread F and
equatorial plasma bubbles. The global map of ΔTEC at solar maximum
(September 2013) has stronger fluctuations than those at solar minimum
(September 2008). We obtained new results when we compare the global maps of
the quiet phase and the storm phase of the geomagnetic storm of 15 July 2012.
It is evident that the TEC fluctuations are increased and extended over the
southern magnetic polar region at the day of the geomagnetic storm. The
north–south asymmetry of the storm response is more pronounced in the upper
ionosphere (ray tangent points h = 400–500 km) than in the lower
ionosphere (ray tangent points h = 200–300 km).
Response of the total electron content at Brazilian low latitudes to corotating interaction region and high-speed streams during solar minimum 2008
