In an unprecedented multi-institutional study, an international team of researchers has uncovered extraordinary ionospheric disturbances linked to the super geomagnetic storm that struck Earth from May 10 to 12, 2024. This event, often termed the “Mother’s Day magnetic storm,” represents the most intense geomagnetic storm witnessed in the past two decades. Utilizing a combination of ground-based ionospheric measurements and spaceborne observations, the team revealed dramatic reductions in ionospheric electron density, with direct implications for radio communications and satellite navigation systems across the Northern Hemisphere.
At the heart of this investigation was an extensive data set derived from the Chinese Meridian Project (CMP) monitoring network, supplemented by records from multiple satellites and sophisticated numerical models. These instruments captured a stunning decline of up to 98% in total electron content (TEC) over China and large portions of the Northern Hemisphere, persisting for more than 48 hours. Such depletion levels represent a remarkable departure from typical ionospheric behavior during geomagnetic storms, wherein electron density often fluctuates but rarely plunges to such extremes.
The depletion was most pronounced in the low-latitude zones of the East Asian sector, where researchers noted a loss of approximately 100 TEC units—a metric indicating severe deprivation of free electrons in the ionosphere. This decline was accompanied by the suppression and eventual disappearance of the northern crest of the equatorial ionization anomaly (EIA), a normally robust feature that signifies elevated electron densities roughly 15 degrees north and south of the magnetic equator. This anomaly’s disruption signals a profound alteration of ionospheric dynamics triggered by the geomagnetic storm.
Compounding these observations, multiple key ionosondes within the CMP network recorded a complete loss of backscatter echoes during the event. Ionograms, which ordinarily show stratified electron density layers by measuring returned radio pulses, indicated ‘blanketing’ or interruptions, consistent with critically depleted electron densities. These disruptions in high-frequency (HF) radio signals underscore the practical consequences of such ionospheric disturbances for communications reliant upon ionospheric reflection, including aviation, marine navigation, and emergency responder systems.
To dissect the underlying physical mechanisms, the team scrutinized vertical plasma drift measurements and the ratio between atomic oxygen (O) and molecular nitrogen (N₂), denoted ΣO/N₂. Changes in these parameters provided crucial clues: the extreme electron density depletion was primarily driven by compositional perturbations in the neutral atmosphere—specifically, a relative increase in N₂ at the expense of O—propagating equatorward from high-latitude regions. This neutral composition disturbance, compounded by east-west electric field modifications associated with phenomena known as overshielding penetration and disturbance dynamo electric fields, effectively suppressed plasma uplift and replenishment in the low-latitude ionosphere.
Moreover, the research unveiled a pronounced hemispheric asymmetry in ionospheric responses to the storm. While the Northern Hemisphere exhibited severe electron density depletion, the Southern Hemisphere, particularly its mid- to low-latitude ionosphere, displayed marked enhancements in electron concentration. This divergence, revealed through coordinated observational data and Thermosphere-Ionosphere-Electrodynamics General Circulation Model (TIEGCM) simulations, was primarily driven by seasonal differences—in particular, the summer-to-winter neutral winds and hemispheric variations in ΣO/N₂ ratios. These findings challenge previous assumptions of more uniform storm impacts on the Earth’s ionosphere and stress the complexity of coupled magnetosphere-ionosphere-thermosphere interactions.
The implications of this study extend beyond theoretical advances, touching upon the operational vulnerabilities of modern technology. Many satellite navigation and communication systems rely on consistent ionospheric electron densities to accurately transmit signals. The observed reductions in TEC and the resulting HF radio blackouts compromise this signal propagation, potentially leading to navigation errors and communication failures over affected regions. Such space weather-induced disruptions underscore the necessity for improved forecasting and monitoring capabilities.
First author Yanhong Chen highlights the rarity of such an event and its profound impacts: “The magnitude and extent of the reduction in ionospheric electron density are very unusual, and we have also observed interruptions in HF radio signals, resulting from critically low electron density that prevents effective signal reflection.” This statement reflects the grave challenges faced by radio technologists and space weather forecasters when unexpectedly extreme ionospheric conditions arise.
The involvement of cutting-edge numerical modeling helped decode these observations. By integrating multi-instrument measurements into TIEGCM simulations, the researchers could simulate the complex dynamical coupling whereby neutral atmospheric disturbances propagate downward and equatorward, modulating plasma densities. These models, combining physics-based descriptions of neutral composition changes, electric fields, and ionospheric plasma drifts, reproduced the observed phenomena with unprecedented fidelity, confirming the multi-faceted nature of storm-time ionospheric variability.
Furthermore, this research contributes substantively to the fundamental understanding of the magnetosphere-ionosphere-thermosphere coupling system—a triad of interlinked geospace domains whose interactions govern near-Earth space weather phenomena. By characterizing how extreme geomagnetic storms can distort this equilibrium, the study sets a new standard for anticipating space weather impacts, especially during superstorm conditions that strain the resilience of satellite, communication, and navigation infrastructures.
From an observational standpoint, the pivotal role of the CMP network cannot be overstated. Comprising a dense array of ionosonde and GNSS receivers across China, CMP provided unparalleled spatial and temporal coverage during the storm. The strategic placement of these instruments, along with ground- and space-based complementary sensors, allowed for detailed mapping of the ionospheric electron content changes and facilitated the identification of ionogram interruptions across multiple stations, reflecting the regional severity of the ionospheric collapse.
Notably, the multi-instrument approach revealed the timing and geographical patterns of ionospheric interruption onset and recovery phases, offering insights into the storm’s evolving dynamics. Instances of ionogram blanketing occurred at varying universal times at distinct stations, underscoring the spatiotemporal complexity of the ionospheric response. Such findings emphasize the importance of coordinated global ionospheric monitoring and data sharing to effectively capture the nuances of space weather events.
In summary, this groundbreaking study elucidates the profound ionospheric perturbations resulting from one of the strongest geomagnetic storms in recent history. It highlights a near-total depletion of ionospheric electron density and the consequential degradation of radio wave propagation over the Northern Hemisphere, accompanied by a dramatic hemispheric asymmetry in ionospheric response. These results prompt a reassessment of current models and forecasting capabilities while emphasizing the pressing need to safeguard technological systems vulnerable to space weather extremes.
As society becomes increasingly reliant on space-based and radio-dependent technologies, understanding and anticipating ionospheric disruptions during geomagnetic storms becomes ever more crucial. This work not only advances scientific knowledge but also paves the way for enhanced mitigation strategies, ensuring the resilience of critical communication and navigation networks in the face of future space weather threats.
Subject of Research: Ionospheric response to extreme geomagnetic storms and impacts on radio wave propagation
Article Title: Extreme Ionospheric Electron Density Depletion and Radio Wave Interruptions during the May 2024 Mother’s Day Super Geomagnetic Storm
Web References: http://dx.doi.org/10.1093/nsr/nwaf307
References: National Science Review article, DOI 10.1093/nsr/nwaf307
Image Credits: © Science China Press
Keywords: Super geomagnetic storm, ionosphere, electron density depletion, total electron content, ionogram interruptions, equatorial ionization anomaly, space weather, Thermosphere-Ionosphere-Electrodynamics General Circulation Model (TIEGCM), high-frequency radio blackout, magnetosphere-ionosphere-thermosphere coupling, Chinese Meridian Project (CMP)
