On 10 May 2024, a severe geomagnetic storm coinciding with Mother's Day in Mexico lasted over 40 hr and produced polar auroras observable at low latitudes. This storm, the most intense since 2003, resulted from a series of solar flares and coronal mass ejections from active region 3664. The event was significant for space weather studies in Mexico, marking a milestone by enabling comprehensive measurements of its effects. The Mexico Space Weather Service (SCIESMEX) and the National Space Weather Laboratory (LANCE) had prepared for such an event since their inception. LANCE's instrument networks recorded solar chromospheric images, solar radio bursts, geomagnetic variations, Schumann resonances, ionospheric disturbances, and energetic particle flows. They also monitored Geomagnetically Induced Currents (GICs) in three strategic substations of the national electrical system. This provided unprecedented insights into the dynamics of severe space weather events at the North‐American low‐latitude environment. Citizen science efforts documented auroras and regional responses, capturing variations in geomagnetic indices, ionospheric disturbances, cosmic ray fluxes, GICs, and technological impacts. SCIESMEX worked with the National Civil Protection System (SINAPROC) to issue warnings, ensuring public awareness and preparedness. This coordination underscores the importance of effective communication and collaboration in mitigating impacts. The May 2024 geomagnetic storm demonstrated the critical role of preparedness, research, and public education in reducing the effects of future space weather events in Mexico.

A Global Navigation Satellite System (GNSS) receiver is, to some extent, a “black box” when its data is used for ionospheric studies. Our results based on Javad, Septentrio, Trimble, and Leica GNSS receivers have proven that the accuracy of the slant Total Electron Content (TEC) calculation can differ significantly depending on the GNSS receiver type/model, because TEC measurements depend on the carrier phase tracking technique applied in a receiver. The correlation coefficient between carrier phase noise in L1 and L2 channels is considered as a possible indicator that shows if the L1-aided tracking technique or independent tracking is applied inside a receiver. An empirical model of the TEC noise component was provided to determine the TEC noise value in different types/models of GNSS receivers.

Manifestations of two solar flares of March 2022 were studied over Mexico. The flare effects in the lower ionosphere had a ~3 min delay from the X1.3-flare onset and ~5 min from the M9.6-flare onset. The maximal impact on the HF signal amplitude was ~(14–15) min after the onset of both flares. The X1.3-flare provoked the shortwave fadeout during ~6 min. The effects in the lower ionosphere lasted longer than the flares and the effects at the F2 region and higher altitudes only during the flares. The interpretation of results showed the following. (1) Based on the absorption level estimated with minimum frequency and signal amplitude on ionograms, the major role of X-ray radiation in the electron concentration increase in the lower ionosphere was confirmed. At the same time, the EUV radiation impact on the lower ionosphere cannot be totally discarded. The lower ionosphere recovery began before and lasted after the X1.3-flare end, being more rapid at Eglin than in Mexico. During M9.6-flare, the responses at the two observation points were rather synchronized due to the more similar illumination conditions at the two meridians. (2) According to the dI variations characterizing the F2 region and higher, the M9.6-flare provoked medium-scale and the X1.3-flare provoked both medium- and small-scale ionospheric irregularities. The response duration corresponded to the dI series filtered with (10–20) min windows. The dI curve during the flares was characterized by the И-form and depended more on the active region position and the flare class than on the solar zenith angle. The available data do not allow us to unambiguously identify the reason for the negative dI: the applied filtering procedure or the physical effect. (3) During both flares, the major EUV impact on the lower ionosphere was by the flux at 133.5 nm and on the F2 region and higher altitudes at 25.6 nm. In addition, during the M9.6-flare, EUV 28.4, 30.4 and 121.6 nm spectral bands also played an important role in the F2 response. During the X1.3-flare, the EUV 25.6 nm flux and X-ray flux impacts on the F2 region were of the same level. The weakest impact was caused by the emission in the EUV 28.4 nm spectral band on the absorption in the lower ionosphere during both flares and on the electron density in the F2 region and higher during the X1.3-flare.

The present work is a comprehensive study of the ionospheric vertical total electron content (vTEC) variations during the nighttime, based on data collected by ground‐based Global Navigation Satellite System (GNSS) receivers over the Latin American region. We provide a qualitative and quantitative analysis of the ionospheric vTEC trend at 21:00, 00:00, and 03:00 local time (LT), during geomagnetically undisturbed days of 2011 (ascending phase) and 2014 (maximum phase), which encompassed (a) the response to the solar flux variation, (b) the seasonal trend in different latitudes and longitudes, and (c) the interhemispheric asymmetry. One significant result of this study is the development of TEC maps for the Latin American region, which are used for the monitoring and forecasting of the ionosphere for space weather purposes. The nighttime vTEC variations showed a strong latitudinal dependence, especially in the Northern Hemisphere. For 2011, the semiannual anomaly was similar to that observed in daytime; however, in 2014, the receivers at midlatitude presented asymmetric behavior. Similarly, the nighttime winter anomaly (NWA) was very weak in both years. The Equatorial Ionospheric Anomaly (EIA) signature was absent from June to August, a period in which the hemispheric disparity in the vTEC values became more evident, suggesting a feeble interhemispheric circulation. The Midlatitude Summer Nighttime Anomaly (MSNA) was also identified in the Southern Hemisphere, during January and February of 2011 (moderate solar activity). Model approximations suggest that the equatorward winds and the EIA were involved in the formation of the MSNA.

Natural hazards and geomagnetic disturbances can generate a combination of atmospheric and ionospheric waves of different scales. The carrier phase of signals of global navigation satellite system (GNSS) can provide the highest efficiency to detect and study the weak ionospheric disturbances in contrast to total electron content (TEC) and TEC-based indices. We consider the border between the informative part of the carrier phase spectrum and the uninformative noises—the deviation frequency—as the promising means to improve the GNSS-based disturbance detection algorithms. The behavior of the deviation frequency of the carrier phase spectra was studied under quiet and disturbed geomagnetic conditions. The results showed that the deviation frequency value increases under magnetic storms. This effect was revealed for all GNSS constellations and signals regardless the GNSS type, receiver type/make and data rate (50 or 100 Hz). For the 100 Hz data, the most probable values of the deviation frequency grouped within ~28–40 Hz under quiet condition and shifted to ~37–48 Hz during the weak geomagnetic storms. Additionally, the lower values of deviation frequency of ~18–25 Hz almost disappear from the distribution of the deviation frequencies as it becomes narrower during geomagnetic storms. Considering that the small-scale irregularities shift the deviation frequencies, we can use this indicator as a “red alert” for weakest small-scale irregularities when the deviation frequency reaches ~35–50 Hz.

Possible ionospheric effects of the Morelian meteoroid that passed and exploded over Mexico on 19 February 2020 (18 February 2020 local time) were estimated. The meteoroid trajectory, velocity and time of occurrence were calculated based on outdoor camera records. Modeling was used to estimate the meteoroid initial diameter, density, mass, velocity, energy and their change during its flight in the atmosphere. The ensemble of ionospheric scintillation indices calculated from the high-rate GNSS data and the filtered slant Total Electron Content data were used to reveal the presence of ionospheric disturbances generated by shock waves excited by the meteoroid flight and explosion. The first ionospheric responses to phenomena accompanying the meteoroid were detected (2.5–3.5) min after the explosion. The disturbances were attenuated quickly with distance from their source and were rarely recorded by GNSS receivers located more than 600 km from the meteoroid explosion site. The ionospheric disturbances of intermediate-scale, small-scale, shock-acoustic-wave-scale and sometimes medium-scale were revealed. The detected disturbances corresponded to the range of acoustic-gravity waves. An asymmetry of the disturbance manifestation in different directions was observed. The obtained results are in accordance with results of the observation of other meteoroids. Although the object was smaller and of less energy than other known meteoroids, it is an interesting case because, to the best of our knowledge, it isthe first known to us low-latitude meteoroid with the detected ionospheric effects.