@PhDThesis{Chingarandi:2023:ChEqLo,
author = "Chingarandi, Frank Simbarashe",
title = "Characterization of the equatorial and low-latitude ionosphere
during the deep solar minimum of solar cycle 24",
school = "Instituto Nacional de Pesquisas Espaciais (INPE)",
year = "2023",
address = "S{\~a}o Jos{\'e} dos Campos",
month = "2023-06-28",
keywords = "deep solar minimum, high speed streams, co-rotating interaction
regions, space weather, profundo m{\'{\i}}nimo solar, fluxos de
vento solar de alta velocidade, regi{\~o}es de
intera{\c{c}}{\~a}o corotantes, cl{\'{\i}}ma espacial.",
abstract = "The aim of this work is to characterize the equatorial and
low-latitude ionosphere and the influence of high-speed solar wind
streams (HSSWSs) over Brazil during the deep solar minimum of
solar cycle 24 (SC24). Multiple ground-based and spacebased
instruments {{namely;}} ground-based GNSS receivers, magnetometers
as well as NASA Global-scale Observations of Limb and Disk (GOLD)
and SWARM satellites were employed for the first time. Total
electron content (TEC) obtained from GNSS receivers was used to
derive multiple ionospheric parameters namely: (1) percentage
deviation from quiet time {{(\δTEC);}} (2) the rate of TEC
{{(ROT);}} (3) the rate of TEC index (ROTI) and (4) spatial
gradients {{(\∇TEC).}} This was done to characterize
gradients associated with irregularities and to quantify
ionospheric response to geomagnetic storms. GOLD OI 135-6 nm disk
measurements brought new insights into the structure of plasma
bubbles and the post-sunset EIA over South America while ROTI
facilitated the continuous monitoring of irregularities at a high
temporal resolution. Analysis of the solar wind and interplanetary
space showed that during the deep solar minimum, solar activity
was weak, with low solar flux, solar flares and fewer intense
geomagnetic storms. Coronal holes were the main source of
recurring, long-duration, weak-moderate geomagnetic storms that
periodically impacted solar wind and the thermosphere-ionosphere
over South America. Long-duration CIR-driven storms (days) had
remarkable effects on the thermosphere composition as well as
plasma density while shorter-duration CIRs (hours) also produced
unexpected changes in the thermosphere-ionosphere system. Our
results showed that the minor CIR/HSS-driven storms caused
positive ionospheric storms of over 20 TECU (+300%) and negative
storms of 20 TECU (80%) over the South crest of the equatorial
ionization anomaly (EIA). Thus, weaker HSS/CIR-driven storms have
a larger impact than intense, CME-driven storms. In addition, the
amplitude of ionospheric storms and irregularities was maximum in
the recovery phase. Ionospheric storms revealed seasonal
differences in response due to changes in the thermosphere
background conditions. The amplitude of ionospheric irregularities
and spatial gradients in TEC showed a strong correlation with the
magnitude of TEC. For the first time, GOLD 135.6 nm images, GNSS
TEC and ROTI maps reveal periodic separation of EPBs and
small-scale irregularities during very low solar activity.
Geomagnetic activity during solar minimum is significant and can
no longer be ignored. Understanding Sun-Earth interactions and
monitoring of the thermosphere-ionosphere is of great interest for
Space Weather forecasting and GNSS applications. RESUMO: O
objetivo do trabalho foi caracterizar a ionosfera equatorial e de
baixa latitude sobre o Brasil e a influ{\^e}ncia das correntes de
vento solar de alta velocidade (HSSWSs) do m{\'{\i}}nimo solar
profundo do ciclo solar 24 (SC24). Varias instrumentos foram
utilizados, incluindo receptores GNSS terrestres,
magnet{\^o}metros, {{sat{\'e}lites;}} o GOLD da NASA e o SWARM.
O conte{\'u}do total de el{\'e}trons (TEC) obtido dos receptores
GNSS foi usado para derivar m{\'u}ltiplos par{\^a}metros
ionosf{\'e}ricos, a saber: (1) desvio percentual do tempo calma
{{(\δTEC);}} (2) a taxa de TEC {{(ROT);}} (3) a taxa do
{\'{\i}}ndice TEC (ROTI) e (4) gradientes espaciais em TEC
{{(\∇TEC).}} Isso foi feito para caracterizar gradientes
associados a irregularidades e quantificar a resposta
ionosf{\'e}rica a tempestades geomagn{\'e}ticas. As
observa{\c{c}}{\~o}es do GOLD OI 135-6 nm trouxeram novos
conhecimentos sobre a estrutura das bolhas de plasma e a anomalia
equatorial. O ROTI tornou poss{\'{\i}}vel o monitoramento
cont{\'{\i}}nuo de irregularidades em alta resolu{\c{c}}{\~a}o
temporal. A an{\'a}lise do vento solar e do espa{\c{c}}o
interplanet{\'a}rio mostrou que a atividade solar era fraca, com
baixo fluxo solar, erup{\c{c}}{\~o}es solares e menos
tempestades geomagn{\'e}ticas intensas. Os buracos coronais (CHs)
foram a principal fonte de tempestades geomagn{\'e}ticas fracas a
moderadas recorrentes e de longa dura{\c{c}}{\~a}o que
impactaram periodicamente o vento solar e a termosfera-ionosfera
sobre a Am{\'e}rica do Sul. A magnitude das tempestades
geomagn{\'e}ticas impulsionadas pelo HSSWS era semelhante. Um
total de 28 tempestades geomagn{\'e}ticas fracas a moderadas (30<
SymH < 60nT), incluindo uma intensa tempestade geomagn{\'e}tica
(SymH = 205nT) foram examinadas. Os tempestades induzidas por CIR
de longa dura{\c{c}}{\~a}o (dias) tiveram efeitos not{\'a}veis,
enquanto CIRs de curta dura{\c{c}}{\~a}o (horas) tamb{\'e}m
produziram mudan{\c{c}}as inesperadas no TI. Os resultados
mostraram que as tempestades menores causadas por CIR/HSS causaram
tempestades ionosf{\'e}ricas positivas de mais de 20 TECU em
magnitude (+300%) e tempestades negativas de 20 TECU (80%) sobre a
crista sul da anomalia equatorial de ioniza{\c{c}}{\~a}o (EIA).
Al{\'e}m disso, a amplitude das tempestades e irregularidades
ionosf{\'e}ricas foi m{\'a}xima na fase de
recupera{\c{c}}{\~a}o. As tempestades ionosf{\'e}ricas
revelaram diferen{\c{c}}as sazonais em resposta devido a
mudan{\c{c}}as nas condi{\c{c}}{\~o}es de fundo da termosfera.
Grandes varia{\c{c}}{\~o}es diurnas no EIA e irregularidades
foram observadas sob a influ{\^e}ncia de campos el{\'e}tricos de
penetra{\c{c}}{\~a}o imediata (PPEF) e ventos perturbadores. A
amplitude das irregularidades e gradientes apresentaram um forte
correla{\c{c}}{\~a}o com o TEC. Pela primeira vez, os mapas de
ROTI revela uma separa{\c{c}}{\~a}o peri{\'o}dica de
irregularidades durante a baixa atividade solar. Tempestades
geomagn{\'e}ticas fracas podem causar dist{\'u}rbios
ionosf{\'e}ricos mais significativos do que tempestades intensas
e, portanto, n{\~a}o podem mais ser ignoradas.",
committee = "Martins, Maria Paulete Pereira (presidente) and Guedes, F{\'a}bio
Becker (orientador) and C{\^a}ndido, Cl{\'a}udia Maria Nicoli
(orientadora) and Jonah, Olusegun Folarin (orientador) and
Correia, Emilia and Takahashi, Hisao and Oliveira, Virginia
Klausner de and Krause, Linda Habash",
englishtitle = "Caracteriza{\c{c}}{\~a}o da equatorial e ionosfera de baixa
latitude durante o solar profundo m{\'{\i}}nimo de ciclo solar
24",
language = "en",
pages = "197",
ibi = "8JMKD3MGP3W34T/497SGP5",
url = "http://urlib.net/ibi/8JMKD3MGP3W34T/497SGP5",
targetfile = "publicacao.pdf",
urlaccessdate = "28 abr. 2024"
}