Luis Eduardo Antunes Vieira

This study develops and evaluates a hybrid, data-driven pipeline for total solar irradiance (TSI) forecasting from solar disk imagery. TSI, the spectrally integrated solar radiative flux at 1 au, ≈1361 W m ⁻² , is a primary boundary condition for climate models, yet existing physics-based reconstructions (SATIRE-S, EMPIRE) map concurrently observed magnetic proxies onto irradiance and carry no intrinsic forecast horizon. We address this with a three-stage architecture: a self-organizing map (SOM) performs unsupervised, pixel-wise segmentation of coregistered Helioseismic and Magnetic Imager (HMI) / Solar Dynamics Observatory (SDO) continuum images, unsigned magnetograms, and the heliocentric-angle ( μ ) map; a convolutional autoencoder (AE) compresses the segmentation into a 32-dimensional descriptor of the instantaneous disk state; and a long short-term memory (LSTM) network maps the descriptor sequence, together with lagged TSI, onto future TSI. Models are trained on the ascending phase of Solar Cycle 24 and tested on an independent 82 day interval (≈328 samples at 6 hr cadence) at six horizons (6–72 hr), benchmarked against persistence, three ablated variants, and the SATIRE-S and EMPIRE reconstructions. An ablation study identifies the SOM as the dominant source of forecast skill: the simpler SOM-LSTM performs best at short horizons and retains useful skill to 24 hr, outperforming the full SOM-AE-LSTM at five of six horizons. Forecast skill collapses between 24 and 48 hr, a limit we show to be a physical consequence of solar rotation, which carries surface features through substantial changes in μ and onto the unobserved hemisphere. We conclude that ≈24 hr is the operational ceiling of single-disk, image-based TSI forecasting.

The auroral‐like sporadic E‐layer is typically observed at altitudes between 100 and 150 km within the South American Magnetic Anomaly region. However, the occurrence of an unusual layer event detected above this altitude range on 18 July 2017 has raised intriguing questions regarding the physical processes responsible for the substantial vertical displacement of this layer. The interplanetary medium conditions during the event exhibited characteristics consistent with the recovery phase of a geomagnetic storm driven by a complex solar wind structure, occurring after substorm activity. To address this atypical layer occurrence, we examined the magnetospheric conditions using the BATS‐R‐US model with two experiments: one including the actual geomagnetic dipole inclination and another omitting it. These configurations allow for a discussion of the energy deposition processes under the prevailing interplanetary medium conditions. Also, the dynamics of the inner radiation belt were investigated through analysis of the magnetic field power spectral density and low‐energy electron flux measurements from the Van Allen Probes mission to verify electron precipitation. Plasma wave observations and their characterization also revealed atypical behavior, in which a non‐standard confinement of hiss waves (200 and 500 Hz) occurred simultaneously with an electron flux decrease (<1 keV), an integrated ionization rate between 250 and 300 km, and the formation of a peculiar layer. Finally, although this magnetic storm was moderate, we demonstrate that particle precipitation significantly impacted the atmosphere, as evidenced by pronounced ozone depletion in the mesosphere with magnitudes substantially stronger when compared to the extreme storm of May 2024.

Magnetic reconnection is a fundamental process in magnetized plasmas that accelerates charged particles at the expense of magnetic energy. This study examines 122 dayside magnetopause crossing events characterized by accelerated ion plasma flows consistent with magnetic reconnection. We use in situ observations from the Time History of Events and Macroscale Interactions during Substorms (THEMIS, 73 events) and Magnetospheric Multiscale (MMS, 49 events) missions, covering various positions near the magnetic equator. The observed ion outflow directions are compared with those predicted by the reconnection X‐line model proposed by Gonzalez and Mozer (1974, https://doi.org/10.1029/ja079i028p04186 ) and implemented by Sibeck and Lin (2011, https://doi.org/10.1029/2011ja016560 ). The model's performance is evaluated using an angular aperture criterion, whereby the observed jet direction must fall within a cone centered on the direction locally perpendicular to the X‐line. The model predictions were consistent with the observations in 63% of the THEMIS and 57.1% of the MMS events. When the aperture angle is reduced to , the prediction accuracy decreases to 53% and 43%, respectively. Most events occur during southward interplanetary magnetic field conditions, which favor magnetopause reconnection. Solar wind flow speeds exceeding 500 km/s indicate a potential interaction between solar wind structures and the reconnection events under investigation. We also conclude that most of the studied events occurred during High Speed Streams (HSS), 47% (THEMIS) and 82% (MMS), as compared with their occurrence during Interplanetary Coronal Mass Ejections (ICMEs), most probably because an HSS passage typically lasts much longer than that of an ICME.

Ground-based astronomical and solar observations are strongly influenced by atmospheric turbulence, a dynamic phenomenon that degrades optical resolution through refractive index fluctuations. This study evaluates daytime sky quality and the refractive index structure parameter ( C n 2 ) at the Pico dos Dias Observatory (OPD) in Brazil, integrating in situ meteorological data with the European Centre for Medium-Range Weather Forecasts Reanalysis version 5 product. Variables such as air temperature, wind speed, relative humidity, and cloud cover are analyzed across vertical and temporal scales, providing insights into diurnal, seasonal, and altitudinal atmospheric behaviors. The study highlights the distinct challenges posed by daytime turbulence, driven by solar heating and convection, on adaptive optics (AO) systems and high-precision solar spectropolarimetric instruments, such as the prototype of the Galileo Solar Space Telescope. To provide context for the atmospheric conditions at the OPD, this study characterizes several key meteorological variables. Typical daytime conditions feature median air temperatures of 15°C–20°C and surface winds of 1.0–4.0 m s ⁻¹ , predominantly from the north, while nighttime conditions are cooler (10°C–15°C) with weaker winds shifting south–southeast. Relative humidity generally remains below 70%, especially in the June–July–August months, making it favorable for astronomical observations. Cloud cover shows seasonality, with clear-sky fractions of about 32% at night and 28% by day, peaking in austral winter and minimizing in summer. Our quantitative analysis of refractive index variability underscores the necessity of advanced AO technologies. Seasonal and vertical profiles of C n 2 present pronounced variability, influenced by solar heating, terrain-induced airflow, and jet stream dynamics. These findings stress the importance of strategic scheduling and turbulence modeling to optimize performance. This comprehensive characterization advances understanding of atmospheric conditions for solar and nighttime astronomy, refining AO systems, and enabling progress in high-precision astrophysics.

This study investigates the feasibility of employing Volume Holographic Grating Filteras optical correlators in solar spectropolarimetry, a field that requires high-precision observations. VHGs, inscribed on photorefractivecrystals using a 633 nm wavelength laser, offer a unique method to simultaneously capture spatial and spectral data, a crucial advancement in observing solar phenomena. Despite challenges such as the fixed wavelength of the laser and the absence of thermal control during recording, the VHGs exhibit notable spectral and angular selectivity. The initial results demonstrate a spectral gradient in the VHG response, likely due to off-Bragg deviations. Future research directions include enhancing the laser capabilities to record VHGs with adjustable wavelengths, optimizing the optical setup, and conducting comprehensive field testing. These steps are aimed at refining the application of VHGs as optical correlators in solar observation, potentially expanding their capabilities in spectropolarimetry. By advancing VHG technology and adapting it for solar observation, the study contributes significantly to our understanding of solar magnetic activities and adds to the broader field of astrophysics. This research underscores the importance of continued innovation, collaboration, and the exploration of new applications in scientific technology.

A existência do campo geomagnético é amplamente conhecida pela comunidade, pois desde a infância há o contato com as bússolas e a rosa dos ventos, evidenciando sempre sua utilidade para a localização no Globo, especialmente nos meios marinhos e aéreos. Apesar de mapeado há séculos, suas propriedades de declinação e inclinação costumam ser negligenciadas por meio da afirmação de que o desvio da bússola para o meridiano costuma ser pequeno – e tende a ser nas regiões equatoriais. Já outras propriedades, como a Anomalia Magnética do Atlântico Sul (SAMA) são pouco conhecidas da população. Este trabalho apresenta um olhar de média profundidade sobre o geomagnetismo, e disponibiliza uma ferramenta computacional cujo objetivo é diminuir a distância entre aspectos pouco conhecidos acerca do campo geomagnético e os alunos dos anos iniciais dos cursos de graduação nas áreas de ciências exatas e da Terra.

The solar physics community is entering a golden era that is ripe with next-generation ground- and space-based facilities, advanced spectral inversion techniques, and realistic simulations that are becoming more computationally streamlined and efficient. With ever-increasing resolving power stemming from the newest observational telescopes, it becomes more challenging to obtain (near-)simultaneous measurements at high spatial, temporal and spectral resolutions, while operating at the diffraction limit of these new facilities. Hence, in recent years there has been increased interest in the capabilities integral field units (IFUs) offer towards obtaining the trifecta of high spatial, temporal and spectral resolutions contemporaneously. To date, IFUs developed for solar physics research have focused on mid-optical and infrared measurements. Here, we present an IFU prototype that has been designed for operation within the near-ultraviolet to mid-optical wavelength range, which enables key spectral lines (e.g., Ca ii H/K, H $\beta $ β , Sr ii, Na i D₁/D₂, etc.) to be studied, hence providing additional spectral coverage to the instrument suites developed to date. The IFU was constructed as a low-budget proof-of-concept for the upcoming $2\text{ m}$ 2  m class Indian National Large Solar Telescope and employs circular cross-section fibres to guide light into a Czerny–Turner configuration spectrograph, with the resulting spectra captured using a high quantum efficiency scientific CMOS camera. Mapping of each input fibre allows for the reconstruction of two-dimensional spectral images, with frame rates exceeding $20\text{ s}^{-1}$ 20  s − 1 possible while operating in a non-polarimetric configuration. Initial commissioning of the instrument was performed at the Dunn Solar Telescope, USA, during August 2022. The science verification data presented here highlights the suitability of fibre-fed IFUs operating at near-ultraviolet wavelengths for solar physics research. Importantly, the successful demonstration of this type of instrument paves the way for further technological developments to make a future variant suitable for upcoming ground-based and space-borne telescope facilities.

The high‐energy electron flux enhancement pattern in the outer radiation belt is observed under the influence of the Interplanetary Coronal Mass Ejections (ICMEs). Ten events were selected during the Van Allen Probes era, with the high‐energy electron flux enhancement starting close to L* = 4. A schematic diagram of the main physical processes responsible for this kind of high‐energy electron flux enhancement is presented, considering the energy deposited in the inner magnetosphere under the influence of ICMEs. Superposed Epoch Analysis is applied to the interplanetary medium parameters, the magnetopause standoff distance, the storm‐time geomagnetic activity indices, the Ultra‐Low Frequency (ULF) waves, and the whistler‐mode chorus waves. A compressed magnetopause, B_z component preferentially southward and storm indices considerably high are observed at the beginning of the electron flux enhancements. The modeled parameters of the chorus waves at the dayside/nightside sectors show the high acceleration efficiency at the beginning of the electron flux enhancement pattern II. These results suggest that the local acceleration driven by chorus waves is essential to these electron flux enhancements at low L*. In contrast, although the ULF waves are detected at the beginning of the studied electron flux enhancements, their contribution is insignificant.

Whitepaper #333 in the Decadal Survey for Solar and Space Physics (Heliophysics) 2024-2033. Main topics: space weather applications; basic research. Additional topics: space weather research/operations/research loop; space weather research/applications/operations pipeline; […]

The interaction and response of the magnetic cloud‐type structure with Earth's magnetosphere were modeled by the SWMF/BATS‐R‐US code. The conversion of magnetic (E_m), kinetic (E_k), and internal (E_i) energies was analyzed as well as the wave power integrated in the ultra‐low frequency (ULF) range of the poloidal (E_ϕ) and toroidal (E_r) electric field components in the equatorial region of the magnetosphere, in seven 2‐hr long intervals, namely, I1 through I7. The intensity of energy conversion and wave activity for I1 and I7 intervals was negligible. The energy conversion started in the I2 interval and extended to the I3, I4, and I5 intervals. The power of the E_ϕ and E_r components in the dayside and nightside regions is clearly observed. The I4 corresponds to interplanetary magnetic field (IMF) B_z mostly southward and the I5 has similar amplitudes of the B_z and B_y components, corresponding to the period of the high geomagnetic activity. The conversion rate for the I4 and I5 was similar, however, the integrated power spectral density (IPSD) of the E_ϕ and E_r components is more intense in I5. During the I6 interval, with predominant IMF B_y, the energy conversion rate is intensified mostly for inner radial distances R < 6 R_E, and the E_k component becomes close to zero for outer regions. The energy conversion regions are located spatially close to or overlapping with regions where the IPSD in the ULF range is intensified. The energy conversion in the inner magnetosphere occurred preferentially between E_m and E_i, with the E_k energy component always present but with lower intensities.