@Article{NegretiPaulCand:2017:ToElCo,
author = "Negreti, Patr{\'{\i}}cia Mara de Siqueira and Paula, Eurico
Rodrigues de and Candido, Cl{\'a}udia Maria Nicoli",
affiliation = "{Instituto Nacional de Pesquisas Espaciais (INPE)} and {Instituto
Nacional de Pesquisas Espaciais (INPE)} and {Instituto Nacional de
Pesquisas Espaciais (INPE)}",
title = "Total electron content responses to HILDCAAs and geomagnetic
storms over South America",
journal = "Annales Geophysicae",
year = "2017",
volume = "35",
number = "6",
pages = "1309--1326",
month = "Dec.",
abstract = "Total electron content (TEC) is extensively used to monitor the
ionospheric behavior under geomagnetically quiet and disturbed
conditions. This subject is of greatest importance for space
weather applications. Under disturbed conditions the two main
sources of electric fields, which are responsible for changes in
the plasma drifts and for current perturbations, are the
short-lived prompt penetration electric fields (PPEFs) and the
longer-lasting ionospheric disturbance dynamo (DD) electric
fields. Both mechanisms modulate the TEC around the globe and the
equatorial ionization anomaly (EIA) at low latitudes. In this work
we computed vertical absolute TEC over the low latitude of South
America. The analysis was performed considering HILDCAA
(high-intensity, long-duration, continuous auroral electrojet (AE)
activity) events and geomagnetic storms. The characteristics of
storm-time TEC and HILDCAA-associated TEC will be presented and
discussed. For both case studies presented in this work (March and
August 2013) the HILDCAA event follows a geomagnetic storm, and
then a global scenario of geomagnetic disturbances will be
discussed. Solar wind parameters, geomagnetic indices,
O\ \∕\ N2 ratios retrieved by GUVI instrument
onboard the TIMED satellite and TEC observations will be analyzed
and discussed. Data from the RBMC/IBGE (Brazil) and IGS GNSS
networks were used to calculate TEC over South America. We show
that a HILDCAA event may generate larger TEC differences compared
to the TEC observed during the main phase of the precedent
geomagnetic storm; thus, a HILDCAA event may be more effective for
ionospheric response in comparison to moderate geomagnetic storms,
considering the seasonal conditions. During the August HILDCAA
event, TEC enhancements from
\ \∼\ \ 25 to 80\ % (compared
to quiet time) were observed. These enhancements are much higher
than the quiet-time variability observed in the ionosphere. We
show that ionosphere is quite sensitive to solar wind forcing and
considering the events studied here, this was the most important
source of ionospheric responses. Furthermore, the most important
source of TEC changes were the long-lasting PPEFs observed on
August 2013, during the HILDCAA event. The importance of this
study relies on the peculiarity of the region analyzed
characterized by high declination angle and ionospheric gradients
which are responsible for creating a complex response during
disturbed periods.",
doi = "10.5194/angeo-35-1309-2017",
url = "http://dx.doi.org/10.5194/angeo-35-1309-2017",
issn = "0992-7689",
language = "en",
urlaccessdate = "19 mar. 2024"
}