Midnight Simultaneous Observations of Spread-F and Multiple F-Layer Stratifications During the 11–12 May 2024 Geomagnetic Superstorm P. R. Fagundes, V. G. Pillat, C. M. Anoruo, G. A. S. Picanço, M. Pezzopane, J. B. Habarulema, K. Venkatesh, A. Tardelli, A. L. Christovam, F. Vieira Journal of Geophysical Research Space Physics, 2025 A geomagnetic superstorm occurred from May 10 to 12, 2024, producing significant spatial and temporal disturbances in the ionosphere. Ground‐based ionosonde and GPS‐TEC data enabled the identification, analysis, and possible interpretation of a unique event: the simultaneous occurrence of Spread‐F and multiple F‐layer stratifications during the local midnight hours of May 11. To the best of our knowledge, this is the first documented case of such a phenomenon occurring at local midnight. This study provides new insights into the dynamics of the equatorial and low‐latitude ionosphere under extreme geomagnetic conditions and highlights the critical role of coordinated, multi‐instrument observations in advancing our understanding of ionospheric electrodynamics.
Solar Flares and the Intricate Response of Earth's Outer Geomagnetic Field Variation P. R. Fagundes, V. G. Pillat, J. B. Habarulema, A. Tardelli, M. T. A. H. Muella Journal of Geophysical Research Space Physics, 2024 In this study, we investigate the intricate electrodynamics of the Earth's horizontal component of the geomagnetic field (ΔH) in response to two significant solar flares (SF) occurring on 03 July and 28 October 2021. These flares are classified as X1.59 and X1.0, respectively. It is noted that the ΔH follows the X‐ray variation during the SF, but there is a time lag of a few minutes between the X‐ray and ΔH. A possible explanation for the time lag is the neutral atmosphere and ionosphere coupling, via ion drag.
Pole-To-Pole Ionospheric Disturbances Due To Solar Flares, During Low Solar Activity P. R. Fagundes, V. G. Pillat, A. Tardelli, M. T. A. H. Muella Journal of Geophysical Research Space Physics, 2024 There are growing concerns about the effect of solar flares on the ionosphere, mainly due to possible deterioration or damage to our communication and navigation satellite systems. On 3 July 2021, and 28 October 2021, there were solar flares (SFs) classified as X1.59 and X1.0, respectively. These two SFs were the only ones of X‐class that occurred during the last low solar activity (LSA:2018–2021). Data from magnetometers and Global Positioning System (GPS)—Total Electron Content (TEC) are used to investigate the spatial‐temporal electrodynamics of the ionosphere from pole‐to‐pole in the American sector. Employing ∆H and vertical TEC, along with the ROT (rate of change of VTEC) parameter. Rapidly ∆H disturbances closely follow the X‐ray variation and the ∆H valleys and peaks are well‐synchronized during the SFs, indicating that they are linked. Major disturbances in the ∆H are noticed in the mid‐low‐equatorial latitudes. However, minor disturbances were seen at high latitudes. Also, |ROT| is a good indicator of the electron density changes during the SFs, especially when the X‐ray intensity rises to the peak.
