Historical astronomy has documented numerous phenomena that allow us to understand the relationship between the Sun, the Earth, and its magnetosphere.
One of the most significant of the 19th century was the geomagnetic storm of February 4, 1872, recorded in Japan, China, and Korea, which produced auroras visible at mid and low latitudes—something extremely rare.
This event is now considered one of the most intense solar storms known, comparable in magnitude to the Carrington event of 1859.
Documents from the era—diaries, scientific reports, and official chronicles—describe skies illuminated by intense red, green, and purple colors for several hours.
In regions where auroras had never been observed, the population and astronomers were bewildered, which prompted meticulous documentation of the phenomenon.
Causes of the geomagnetic storm
The storm was caused by extreme solar activity, likely a coronal mass ejection generated after several days of an intense sunspot presence.
These eruptions released enormous quantities of charged particles that, upon reaching Earth, interacted violently with the magnetosphere.
When those particles collided with the Earth's magnetic field, they produced severe geomagnetic disturbances and triggered auroras in unusual regions of the planet.
This link between sunspots, geomagnetic storms, and auroras was first solidly confirmed thanks to this event.
Observations in Japan, China, and Korea
In Japan, observatories and scholars recorded the phenomenon with precision, describing auroras so intense that they illuminated the landscape as if it were daylight.
In China and Korea, imperial and scientific chronicles recount curtains of reddish light and luminous arcs that moved across the sky for hours.
These Asian data points were especially valuable because they originated from much lower latitudes than typical auroras, proving that the storm had been truly global.
Technological impact
The storm was not only visible but also measurable.
Telegraph systems of the time—already widely used in East Asia—experienced interference, induced currents, and temporary failures, confirming that solar storms directly affect human technology.
This reinforced the idea, already suspected since 1859, that the Sun could disturb electrical communications, which is fundamental to the development of modern engineering and navigation.
Scientific impact
After 1872, the study of terrestrial magnetism and solar physics gained momentum in Asia.
Observatories were expanded, more precise magnetometers were installed, and Asian data began to be integrated into international scientific networks.
The data collected in Japan, China, and Korea were compared with those from Europe and America, helping to build the first global model of Sun-Earth interaction, the basis of modern space weather.
A legacy that influences the present day
The geomagnetic storm of 1872 proved that solar activity can simultaneously affect the atmosphere, the magnetic field, and human technology.
It is one of the best-documented events of the 19th century and a key historical piece of evidence for understanding the risks of modern-day solar storms.
Today, scientists use it as a reference to evaluate the potential impact of future extreme storms on satellites, power grids, and global communication systems.
