The Earth is enveloped by the ionosphere, a layer of ionized gas that acts as a dynamic boundary between the atmosphere and outer space. This region has several key functions for humanity, ranging from protecting us against solar radiation (it absorbs ultraviolet radiation and X-rays) to functioning as a conductive medium for radio waves and satellite signals.
But the ionosphere has a problem when night falls on the magnetic equator: a phenomenon occurs that can destabilize GPS, air communications and telecommunications. Although science has been studying it for decades in other equatorial parts, the African Atlantic sector has been a historical blind spot. Tenerife is right in that void and the German Aerospace Center (DLR) has been looking at the sky from there for more than ten years.
The discovery. The DLR team has confirmed the presence of equatorial plasma bubbles (EPB) over Tenerife in a poster at the 17th International Equatorial Aeronomy Symposium (ISEA-17). The phenomenon is not new, but it is the first time that it has been recorded continuously and systematically in this strip of the Atlantic. For this monitoring, they have used two instruments at the same time: a GNSS receiver and an atmospheric luminescence detector, a combination that allows studying the bubbles on both a small and large scale, essential to thoroughly understand their structure.
The bubbles that the DLR has documented form exclusively at night, reach their peak of activity at the equinoxes and can extend vertically up to 1,700 kilometers above the geomagnetic equator, with structures between 40 and 100 kilometers wide that move towards the east at about 100 meters per second, as reported in the Geophysical Research Letters. Whether or not it appears on a given night remains difficult to predict even in the most studied regions.
Why is it important. Beyond an atmospheric curiosity, plasma bubbles have direct consequences on critical technologies. As they ascend, they generate ionospheric scintillation: rapid, unpredictable fluctuations in radio signals that degrade GPS, disrupt air communications, and affect satellite telecommunications. And it is not something theoretical: in the geomagnetic storm of April 2023 the European navigation system EGNOS suffered it.
But the phenomenon is also unpredictable: the spatial gradient induced by EPBs is a challenge for aircraft guidance systems in precision approaches, according to Satellite Navigation. Knowing how they behave in the African Atlantic sector is a problem with direct consequences for aviation safety and the digital infrastructure of the region.
Context. As explained in this study by the Complutense of Madrid in collaboration with the ICTP of Trieste, plasma bubbles are decreases in electronic density generated by the Rayleigh-Taylor instability mechanism in the equatorial night sector. When the Sun falls, the ionosphere loses stability: the lower layer becomes denser than the upper one, so the light plasma rises, leaving holes empty of electrons. The bubbles.
This same phenomenon was recently detected in the pyramids of Gizah, another area in North Africa. In November 2023, in the midst of a geomagnetic storm, a radar station on the Chinese island of Hainan detected an ionospheric disturbance over the pyramids of Giza, almost 9,500 kilometers to the west, using a super radar LARID (Low Latitude Long Range Ionospheric Radar) developed at the Institute of Geology and Geophysics of the Chinese Academy of Sciences and which was independently validated by GPS receivers in Africa. And they are not the only ones: there are satellites such as COSMIC-2, GOLD and Swarm that make specific observations.
How they do it. The GNSS receiver, which has been operational for more than a decade, detects the flickering that bubbles cause on satellite signals, capturing small-scale irregularities, but without showing their actual shape or size. That is what the second instrument is for: the atmospheric luminescence detector captures the faint light emission that ionospheric oxygen emits at night: where there is a bubble, that light disappears, revealing the actual shape and size of the structure. A decade of GNSS data plus large-scale images: that combination is the methodological novelty of the work.
The philosophy is completely opposite to that followed in Egypt: the DLR observes in situ with high resolution and structural detail, the LARID observes at a distance with enormous range but less geometric precision.
Yes, but. The DLR research at the moment is a poster and not a scientific paper, with everything it entails: peer review, complete data or conclusions that are more than preliminary. On the other hand, and although the study of the Giza pyramids analyzes the same phenomenon, the detection of plasma bubbles was carried out by an independent Chinese team and with different technology. In addition, many open questions remain, such as how often they occur over Tenerife, how it changes with the seasons, when the scintillation is intense enough to affect navigation systems.
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Cover | ESA (Sentinel-2) and ESA (Proba-V)
