Abstract. This work presents an analysis of the ionospheric responses to the solar eclipse that occurred on 14 December 2020 over the Brazilian sector. This event partially covers the south of Brazil, providing an excellent opportunity to study the modifications in the peculiarities that occur in this sector, as the equatorial ionization anomaly (EIA). Therefore, we used the Digisonde data available in this period for two sites: Campo Grande (CG; 20.47∘ S, 54.60∘ W; dip ∼23∘ S) and Cachoeira Paulista (CXP; 22.70∘ S, 45.01∘ W; dip ∼35∘ S), assessing the E and F regions and Es layer behaviors. Additionally, a numerical model (MIRE, Portuguese acronym for E Region Ionospheric Model) is used to analyze the E layer dynamics modification around these times. The results show the F1 region disappearance and an apparent electronic density reduction in the E region during the solar eclipse. We also analyzed the total electron content (TEC) maps from the Global Navigation Satellite System (GNSS) that indicate a weakness in the EIA. On the other hand, we observe the rise of the Es layer electron density, which is related to the gravity waves strengthened during solar eclipse events. Finally, our results lead to a better understanding of the restructuring mechanisms in the ionosphere at low latitudes during the solar eclipse events, even though they only partially reached the studied regions.

The solar activity phenomena that originate the nonrecurrent geomagnetic storms involve sudden explosions of nonpotential magnetic field lines in active regions, which may or may not be accompanied by solar flares, and eruptive filaments outside the active regions (Abunin et al., 2020;Belov et al., 2014;Chen et al., 2019). One remarkable example of a nonrecurrent geomagnetic storm occurred in August 2018, the third strongest of the Solar Cycle 24. The complex space weather responses were generated by two interplanetary coronal mass ejections (ICME) and by the High-Speed Solar Wind Stream (HSS) that hit the Earth between 25 and 27 August 2018.In general, the disturbed magnetospheric electric fields cause large modifications in the ionosphere dynamics during geomagnetic storms. Several works have improved the understanding of these disturbed electric fields showing that they promptly penetrate to the equatorial latitudes oriented in dawn-to-dusk direction as soon as the interplanetary magnetic field (IMF) B z component turns southward, initiating a substorm, which, in turn, increase the activity of auroral electrojet (

Nighttime airglow images observed at the low-latitude site of São João do Cariri (7.4 • S, 36.5 • W) showed the presence of a medium-scale atmospheric gravity wave (AGW) associated with the 21 August 2017 total solar eclipse. The AGW had a horizontal wavelength of ∼1,618 km, observed period of ∼152 min, and propagation direction of ∼200 • clockwise from the north. The spectral characteristics of this wave are in good agreement with theoretical predictions for waves generated by eclipses. Additionally, the wave was reverse ray-traced, and the results show its path crossing the Moon's shadow of the total solar eclipse in the tropical North Atlantic ocean at stratospheric altitudes. Investigation about potential driving sources for this wave indicates the total solar eclipse as the most likely candidate. The optical measurements were part of an observational campaign carried out to detect the impact of the August 21 eclipse in the atmosphere at low latitudes. Plain Language Summary The Moon's shadow during a total solar eclipse introduces horizontal temperature gradients in the atmosphere and screens the ozone layer from solar heating. The shadow also travels supersonically, producing instabilities that can generate the so-called atmospheric gravity wave (AGW). AGWs associated with eclipses are expected to have periodic oscillations with periods ranging from just a few minutes to hours. Additionally, these AGWs can have horizontal wavelengths as large as thousands of kilometers. It is also possible to estimate the propagation path of the AGWs into the atmosphere by solving a system of equations that govern their propagation. This methodology is similar to that of tracing a ray of light that propagates in a varying environment. In the present work, an AGW in the northeast of Brazil was observed with spectral characteristics that indicate association with the 21 August 2017 total solar eclipse. In addition, the ray path matched the Moon's shadow in the stratosphere corroborating with the observational inferences. The AGW was observed by optical instruments during the nighttime, more than 3 h after the end of the eclipse and over 2,000 km away from the Moon's shadow. After a series of publications about the generation of gravity waves by solar eclipses in the beginning of the 1970s decade (Chimonas & Hines, 1970; 1971; Chimonas, 1974), several experiments were carried out to RESEARCH LETTER

Equatorial Plasma Bubbles (EPBs) over South America have been studied extensively over the years. The EPBs are defined as plasma depletion formed by Rayleigh-Taylor Instability (RTI) processes (Kelley, 2009). Different instruments and methodologies can be used to detect these EPBs, such as Ionosondes (

Abstract. This work uses the Disturbance Ionosphere indeX (DIX) to evaluate the ionospheric responses to equatorial plasma bubble (EPB) events from 2013 to 2020 over the Brazilian equatorial and low latitudes. We have compared the DIX variations during EPBs to ionosonde and All-Sky Imager data, aiming to evaluate the physical characteristics of these events. Our results show that the DIX was able to detect EPB-related TEC disturbances in terms of their intensity and occurrence times. Thus, the EPB-related DIX responses agreed with the ionosphere behavior before, during, and after the studied cases. Finally, we found that the magnitude of those disturbances followed most of the trends of solar activity, meaning that the EPB-related total electron content variations tend to be higher (lower) in high (low) solar activity.