1. Solar Flares: What the Sun Sent Out When the Aurora Appeared
The trouble started with explosions on the sun’s surface called solar flares. According to a summary by NICT (the National Institute of Information and Communications Technology), 13 large X-class flares (the largest class) occurred between May 8 and 15, 2024. Having seven X-class flares or higher within 72 hours was a first for the GOES satellite observations, which began in 1975 [1].
The gas from the sun, known as corona gas, reached the area around Earth around 1:30 AM Japan time on May 11. The solar wind speed jumped to 770 km per second, and the magnetic field strength rose to 72 nT [1]. When Earth’s magnetic field is disturbed, it is called a magnetic storm. At the Kakioka magnetic observatory, the K-index, which measures disturbance size on a scale of 10, recorded a "8" four times. This was the first time a K-index of 8 had been observed since August 2005, marking a gap of about 19 years [1].
NICT’s table also notes many reports of auroras being seen in various parts of the world, including mid-latitudes like Japan [1]. However, at that moment, it was not yet clear if the disturbance in the sky would affect daily life on the ground.
2. Why Smartphone Location Errors Increased During the Magnetic Storm
It was not that location services stopped working completely. Instead, there were time periods when errors may have increased. The Geospatial Information Authority of Japan reported that for common positioning systems used in car navigation and smartphones, there were time periods when errors may have increased from around 9:00 AM on May 11 to around 6:00 AM on May 12, based on data from Tsukuba [2].
The path of the radio waves was disturbed. NICT explains that from the night of May 11 to the dawn of May 12, disturbances in the ionosphere passed over Japan. The ionosphere is a layer of the upper atmosphere that carries electric charge. Positioning errors increased during this time [1]. Radio waves from artificial satellites pass through this layer to reach the ground.
This is a bit like seeing the scenery shimmer on hot asphalt in summer, known as "kagerou." However, that is about visible light, while ionosphere disturbance affects invisible radio waves. The mechanisms are not the same.
The disturbance in the ionosphere may have also affected RTK positioning, which uses ground reference stations to find precise locations [1]. In the United States, there were reports of impacts on planting with GPS-guided farm machinery. However, this was secondary information from US news reports, and the detailed situation is not known [1]. Yet, during the same storm, some positioning methods kept their accuracy.
3. How Surveying Kept Its Positions Accurate Despite the Storm
Surveying often uses a two-frequency method. This method uses radio waves of two different frequencies at the same time to correct for ionosphere disturbances. In the first report by the Geospatial Information Authority of Japan, no significant drop in accuracy was confirmed for this method [2].
While general consumer methods saw increased errors, the surveying method held up thanks to its correction system. In this storm, the confirmed impact differed depending on the method used. This information comes from the first report and does not cover every surveying site. The detailed principles of the correction are not in the materials used here, so they are not discussed.
4. Did the Magnetic Storm Disrupt Shortwave Radio?
Shortwave radio is used for long-distance communication. NICT reports that the Dellinger phenomenon, where shortwaves are absorbed by the ionosphere, was observed about 12 times across Japan from May 8 to 15. During these times, shortwave communication likely dropped out [1]. There are also reports of impacts on amateur radio shortwave communication.
It is important to note that the Dellinger phenomenon is caused by X-rays from the flare, which is different from the magnetic storm that shakes Earth’s magnetic field. Even with the same solar explosion, the light arrives at a different time than the gas, and the effects are different.
For aviation, there were alert statuses and route changes, but no reports of flight suspensions [1]. So far, we have looked at radio waves on the ground. What about satellites in space?
5. How the Magnetic Storm Affected Satellites in Low Orbit
Even at low orbits where satellites fly, there is very thin air. It is said that when a magnetic storm heats the upper atmosphere, atmospheric resistance at low orbits increases [3].
In May 2024, NICT’s table notes that for Sony’s satellite EYE, the altitude dropped by 400 m, and the attitude control function reset. However, the table description is brief, and it is not certain that the storm was the cause [1].
On February 3, 2022, 49 Starlink satellites were launched. Up to 40 of them re-entered the atmosphere due to the impact of a magnetic storm on the following day, February 4. SpaceX explained that atmospheric resistance was up to 50% higher than in previous launches, and the satellites could not exit safe mode to raise their altitude [3]. SpaceX also stated that the re-entering satellites had no collision risk with others and were designed to burn up in the atmosphere.
Note: According to SpaceX’s statement, atmospheric resistance was up to 50% higher than in previous launches, and the satellites could not exit safe mode to raise their orbits.
6. Do Magnetic Storms Cause Power Blackouts?
In May 2024, NICT reported no specific impacts on Japan’s power supply. In New Zealand, some transmission services were stopped in advance, but there was no impact. In the United States, NOAA reported impacts on power, shortwave communication, and GPS [1].
In March 1989, a strong magnetic storm caused the power grid in Quebec, Canada, to collapse in about 90 seconds. About 6 million people lost power for about 9 hours, according to NOAA. NOAA also writes that people lost power for several days [5]. The cause is said to be induced currents flowing in long power lines at high latitudes.
NOAA shows magnetic storms on a scale from G1 to G5. At the strongest level, G5, there is a possibility of power grid collapse, transformer damage, long interruptions in shortwave communication, and reduced satellite positioning accuracy for several days. G5 storms are said to occur about 4 times in an 11-year solar cycle [4]. These numbers are based on US locations and frequencies and do not directly show Japan’s situation.
7. How to Check the Sun's Current Status with NICT Space Weather Forecasts
NICT publishes the current status and forecasts of the sun using levels like "quiet" and "active" [6]. You can search for "NICT Space Weather Forecast" on a computer or tablet to see today’s conditions. If you write down the daily level in a notebook for a week, you can see the changes.
It is okay if today is "quiet." On a day when news of a large flare breaks, you can open the page again to check the sky’s condition with your own eyes. When reading numbers in news or forecasts, look at the source to see if it is based on US standards or Japanese observations. This can change how you understand the article.