Showing papers by "Inez S. Batista published in 2022"

Global Monitoring of Ionospheric Weather by GIRO and GNSS Data Fusion

Abstract: Prompt and accurate imaging of the ionosphere is essential to space weather services, given a broad spectrum of applications that rely on ionospherically propagating radio signals. As the 3D spatial extent of the ionosphere is vast and covered only fragmentarily, data fusion is a strong candidate for solving imaging tasks. Data fusion has been used to blend models and observations for the integrated and consistent views of geosystems. In space weather scenarios, low latency of the sensor data availability is one of the strongest requirements that limits the selection of potential datasets for fusion. Since remote plasma sensing instrumentation for ionospheric weather is complex, scarce, and prone to unavoidable data noise, conventional 3D-var assimilative schemas are not optimal. We describe a novel substantially 4D data fusion service based on near-real-time data feeds from Global Ionosphere Radio Observatory (GIRO) and Global Navigation Satellite System (GNSS) called GAMBIT (Global Assimilative Model of the Bottomside Ionosphere with Topside estimate). GAMBIT operates with a few-minute latency, and it releases, among other data products, the anomaly maps of the effective slab thickness (EST) obtained by fusing GIRO and GNSS data. The anomaly EST mapping aids understanding of the vertical plasma restructuring during disturbed conditions.

Responses of intermediate layers to geomagnetic activity during the 2009 deep solar minimum over the Brazilian low-latitude sector

Abstract: Abstract. This work presents the daytime behavior of the intermediate layer (ILs) parameters (the virtual height – h'IL, and the top frequency – ftIL) over the low-latitude region of Cachoeria Paulista (CP, 22.42∘ S; 45∘ W, I: −34.59∘) during the 2009 deep solar minimum. Under such a unique condition, this research reveals the ILs' quiet state seasonal behavior as well as its responses to moderate changes in the geomagnetic activity. The main results show that even small variations of geomagnetic activity (quantified by the planetary Kp index) are able to modify the dynamics of the ILs parameters. For the first time, it was observed that during the summer, the h'IL decreases rapidly with the increase of geomagnetic activity, mainly in the early morning hours, while in the following hours, a smoothed rise of the IL was found in all seasons analyzed. Regarding the IL frequency, it was observed that after 12:00 LT, there is a tendency to decrease with the increase of magnetic disturbances, this characteristic being more intense after 16:00 LT for summer and winter. For the equinox, such variation was detected, however with half of the amplitude of the other seasons. In addition, the domain of the annual periodicity of the ftIL stands out, while the h'IL presents a semiannual component under the condition of geomagnetic quiet.

The role of the inner radiation belt dynamic in the generation of auroral-type sporadic E-layers over south American magnetic anomaly

Abstract: The dynamics of the electron population in the Earth’s radiation belts affect the upper atmosphere’s ionization level through the low-energy Electron Precipitation (EP). The impact of low-energy EP on the high-latitude ionosphere has been well explained since the 1960’s decade. Conversely, it is still not well understood for the region of the South American Magnetic Anomaly (SAMA). In this study, we present the results of analysis of the strong geomagnetic storm associated with the Interplanetary Coronal Mass Ejection (May 27-28, 2017). The atypical auroral sporadic E layers (Esa) over SAMA are observed in concomitance with the hiss and magnetosonic wave activities in the inner radiation belt. The wave-particle interaction effects have been estimated, and the dynamic mechanisms that caused the low-energy EP over SAMA were investigated. We suggested that the enhancement in pitch angle scattering driven by hiss waves result in the low-energy EP (≥10 keV) into the atmosphere over SAMA. The impact of these precipitations on the ionization rate at the altitude range from 100 to 120 km can generate the Esa layer in this peculiar region. In contrast, we suggested that the low-energy EP (≤1 keV) causes the maximum ionization rate close to 150 km altitude, contributing to the Esa layer occurrence in these altitudes.

Disconnection and Reconnection in Plasma Bubbles Observed by OI 630 nm Airglow Images From Cariri Observatory

Abstract: We use OI 630 nm airglow images obtained with the All‐sky imager installed at São João do Cariri (7.4°S, 36.5°W) to report the very rare phenomenon of disconnection and reconnection between adjacent plasma bubbles. We report here for the first time observations of the phenomenon at Cariri. These observations show that the phenomenon is independent of the solar flux and occurs between September and December in the Brazilian sector. The phenomenon consists first in separating a part of the bubble followed by its capture by other adjacent bubbles via electrostatic potential fields. Statistically, the phenomenon is of very low occurrence and its probability varies between 1/120 and 1/165 per year, and on certain occasions it is zero.

Ionospheric Variability over the Brazilian Equatorial Region during the Minima Solar Cycles 1996 and 2009: Comparison between Observational Data and the IRI Model

Abstract: The behavior of the Brazilian equatorial ionosphere during the solar minimum periods, 1996 and 2009, which cover the solar cycles 22/23 and 23/24, respectively, is investigated. For this, the F2 layer critical frequency (foF2) and peak height (hmF2) registered by a Digisonde operated at São Luis (2.33° S; 44° W) are carefully analyzed. The results show that the seasonal mean values of the foF2 and the hmF2 in the equinoxes and winter during 2009 were lower than in 1996. In the summer, an anomalous response to solar variability was observed. In this case, the hmF2 in 2009 is higher than in 1996 during a specific daytime interval. Besides that, it was verified that the prereversal enhancement of the zonal electric field (PRE) during the equinoxes in 2009 occurred a few minutes earlier than in 1996. Additionally, a Fast Fourier Transform (FFT) analysis was used to investigate the impacts of solar atmospheric tides (amplitude, diurnal, semidiurnal, and terdiurnal modes) on foF2 and hmF2 parameters with respect to its seasonality. Significant differences were observed between their values during the two minima, mainly in the amplitude of hmF2, which was higher in 1996 than in 2009 for all days analyzed. Moreover, the seasonality in the diurnal and semidiurnal modes for both periods presented an annual variability, while the terdiurnal mode exhibited annual and semiannual components. The results are compared with the International Reference Ionosphere (IRI) model, and the main differences between the observation and the model results are discussed in this work.

Solar Flare and Radio Burst Effects on GNSS Signals and the Ionosphere During September 2017

Abstract: Strong solar flare events can occur even during the decay phase of the solar cycle. During these events concurrent increases in the X‐ray and Enhanced UV (EUV) fluxes and solar radio bursts (SRBs) can be observed. The SRBs cover a large range of frequencies including the L band, giving rise to signal fades in the GNSS carrier‐to‐noise ratio and fluctuations in its amplitude and phase. The increases in the X‐ray, UV, and EUV fluxes cause increase in the ionospheric D, E, and F region electron densities. The aim of this work is to analyze the effects in the GNSS signal, in the ionosphere and in the magnetic field H component of the X9.3 and X1.3 solar flares that occurred on 06 and 07 September 2017, respectively. Data from a network of six GNSS receivers, two magnetometers, and four Digisondes are used in the analysis. Fades of about 5 and 10 dB were observed in the signals of GNSS L1 and L2/L5 frequencies, respectively. Significant positioning errors, were observed for the strongest X9.3 flare. A sudden increase in Total Electron Content with the rates of 2.5–5.0 TECU/min was observed. An increase in the E layer density gave origin to an increase in the Equatorial Electrojet intensity, whose signatures were observed in the H component of two magnetometers. Another observed effect was the ionospheric D region density increase that caused disruption in the Digisonde signal. As a consequence of the described effects, GNSS receivers may fail to produce accurate navigation solution.