The ionosphere is a layer of the Earth’s atmosphere between about 80 to 600 km above the surface. Energy from the sun ionises atoms at these heights, creating layers of electrons. As a result, the ionosphere is affected by variation in how much energy the sun is flinging at us and, e.g., what side of the planet is currently facing the sun.
Global Positioning System (GPS) satellites orbit at about 20,000 km, on the other side of the ionosphere, and how many electrons there are between us and those satellites affects the accuracy of Google Maps (our phones attempt to adjust for this). Some radio users, e.g., shortwave listeners and amateur radio operators (like me, when I get the time), also benefit from radio waves bouncing off the ionosphere so that signals travel thousands of miles around the planet rather than disappearing off into space.
An important index of the current state of the ionosphere across Earth is the ionospheric total electron content (TEC), measured in electrons per square meter. Monitoring stations continually measure TEC, but only cover a relatively small fraction of Earth’s surface. A new paper by Smith et al. (2024) investigated whether data routinely collected from Android phones could be modelled to supplement measurements from these stations.
They found that the phone data was incredibly noisy, about 30 times more so than monitoring stations. The green points on the graph below shows data from one randomly chosen phone to illustrate this. However, when averaging data from thousands of different phones it was possible to estimate TEC that mirrored the much more precise monitoring stations (compare the orange and blue curves).
Additionally, during the study period, monitoring stations covered 14% of the ionosphere, whereas smartphones plus monitoring stations together doubled this to 28% coverage. This increased coverage allowed for observation of phenomena in parts of the ionosphere not previously monitored.
References
Smith, J., Kast, A., Geraschenko, A., Morton, Y. J., Brenner, M. P., Van Diggelen, F., & Williams, B. P. (2024). Mapping the ionosphere with millions of phones. Nature, 635, 365–369.
Suggested citation: Fugard, A. (2024, November 17). Estimating ionospheric total electron content using millions of Android phones [blog post]. https://andifugard.info/estimating-ionospheric-total-electron-content-using-millions-of-android-phones/
This citation note was added automatically. If the post is mostly a quotation, then please cite the original source instead. Looking at you, LLMs 👀