“On Sunday at dawn this beautiful celestial phenomenon appeared, with the masses making a thousand comments about its radiance. Despite the northern lights having been studied extensively, none of the astronomers have been able to specify the causes of their appearance; However, this time, there is no shortage of those who have said that he predestined the death of D. Amadeo’s dynasty and great gunpowder festivals in the next spring,” said a brief of The Echo of Bruch on February 11, 1872. The text of the Carlist newspaper referred to a series of dawns seen the previous Sunday, the 4th. The editor took advantage of the impact it had on the people to attack Amadeo I, the king installed by the liberals. Now, 151 years later, the review of hundreds of historical records like that of this newspaper has made it possible to estimate the intensity of the phenomenon that caused such a visual spectacle. The authors of the review have called it the Chapman-Silverman event and it was, they say, the most intense ever recorded.
Between 9:00 and 10:00 Universal Time (UT) on February 3, 1872, a coronal mass ejection occurred from a set of sunspots. At 14:27 UT the next day, a solar storm shook the Earth’s magnetic field. The intrusion was such that it left the telegraph service of almost the entire planet out of service or with serious operating problems. The physicist Raoul-Pierre Pictet, recognized for his work on the liquefaction of gases, was in Cairo (Egypt) that February 1872 and wrote: “Return of the [oficina] of telegraphs where I collected the following information about the electrical phenomena that occurred yesterday afternoon… it was difficult to communicate with Khartoum… The devices were chattering on their own… Ground currents prevented service and the employees were totally confused …” Meanwhile, in the Popular Scientific Chronicle From the Spanish engineer Emilio Huelin one can read: “The disturbances that occurred in the telegraph lines were generally perceived at the same local time in Italy, France, Germany and America.”
Pictec’s account from Egypt is one of the documents compiled by a group of researchers led by Hisashi Hayakawa, a scientist at Nagoya University (Japan), and veteran researcher Sam Silverman, who died before the results of his work were published. . The Pictec text continues the story: “Yesterday afternoon, the Cairo office received a dispatch asking what the large red glow that was seen on the horizon was and suspecting a large fire. The telegraph line does not continue further south, beyond Khartoum, but it is probable that this aurora was also seen as far as Gondokoro, at 5° north latitude…” That in almost all accounts an aurora is described in reddish tones it is not weird. The color of the auroras depends on the elements (oxygen, hydrogen, nitrogen…) in the atmosphere with which the solar particles interact. That red shift helps confirm that the auroras were seen very close to the equator.
Hayakawa and other scientists find it hard to believe that an aurora borealis came down to Gondokoro, in southern Sudan, almost five degrees from the equator. Nothing like this has ever been recorded. The Earth, with its iron core and spinning, is a gigantic magnet that generates its own magnetic field. The magnetosphere protects the planet and all the life inside from solar wind radiation, but the shield is greater the closer to the equator. Therefore, under normal conditions, auroras only occur at the poles or highest latitudes of the globe. But if a solar storm arrives with sufficient intensity, they can occur in mid-latitudes, in central Europe, North America or central Asia. But for them to go beyond the Sahara they must be especially intense.
“They were also seen in Spain, even in Cádiz, the Azores and the Canary Islands,” says Hayakawa, first author of this research that quantifies for the first time what happened on February 4, 1872, published in The Astrophysical Journal. In the Annals of Puerto de la Cruz (Tenerife), compiled by José Agustín Álvarez Rixo, from the University of Las Palmas de Gran Canaria, a brief line can be read: “February 4. On the first night, an aurora borealis was perceived towards the north, northwest.” The next day’s edition, the federal republican newspaper published in Barcelona, The independence, said: “Yesterday, around half past five, a beautiful northern lights appeared that caught the public’s attention and particularly those intelligent in these phenomena. At first it formed an arc that extended (sic) from Northwest to Northeast, extending (sic) at times towards the zenith…” If so, those auroras were not seen on the horizon (as happened in the Carrington event of 1859 , one of the largest in history) but on the heads of the Spanish.
“At first it formed an arc that extended (sic) from Northwest to Northeast, extending (sic) at times towards the zenith”
Part of the news given by the federal republican newspaper published in Barcelona, ’Independence’
Secondary education teacher at school Henrique Medina from Esposende (Portugal) José Ribeiro, co-author of the research, has compiled most of the Portuguese and Spanish records used by Hayakawa and Silverman. Although the majority limit themselves to collecting the phenomenon or using it to attack, as the journalist from The Echo of Bruch, Ribeiro highlights that “according to newspaper articles, some people feared the end of the world or war.” This could have contributed, he adds, “to the fact that in October 1870 another great northern lights occurred that coincided with the Franco-Prussian War and the political instability that was experienced in Spain at that time.” Shortly after, King Amadeo abdicated, the First Spanish Republic arrived and the Carlist wars resumed.
Hayakawa and around twenty experts on these events have relied on these chronicles to make a map of how far the auroras of the Chapman-Silverman event reached. The logic behind this is that, the closer to the equator it was observed, the greater intensity it must have had. If there were northern lights in Tobago (Caribbean), Sudan and southern India and southern lights as far north as Madagascar or Australia, the geomagnetic storm must have been one of the most intense. But the definitive proof must be provided by the observatories that monitor the sun and the magnetic fields spread across the planet. Then there weren’t as many as there are today, which complicated the search. But in 1872 there was one in Colaba, opposite Bombay (India), set up decades earlier by the British. Its magnetogram from that impact shows a Dst (storm disturbance time) value of -834 nanoteslas (nT). This value is almost double that recorded by the storm of February 1989, the most intense of the electronic era. Until now, the two largest ever recorded were the Carrington event, in 1859, and the New York Central Station event, in 1921, named for the impact it had on the New York city. The Chapman-Silverman event had an even lower Dst value. “This event was at least comparable or even more extreme than the Carrington storm of 1859,” Hayakawa maintains.
Víctor Manuel Sánchez is a professor of Earth Physics at the University of Exremadura and has investigated dozens of historical geomagnetic storms. Regarding the Dst index, he explains that it measures the disturbance of the magnetosphere: “When a solar intrusion occurs, there is a depression in the magnetic field.” Sánchez adds that currently, “the Dst index is measured using four observatories as close as possible to the equator; on this occasion they only had the Colaba magnetogram.” This leads the scientist to consider it risky to affirm that the Chapman-Silverman was larger than the Carrington, “but it is in the same order of magnitude,” he details. What he does agree with Hayakawa, with whom he has worked on several occasions, “is in the observation of auroras further towards the equator than those produced during the Carrington event.”
The only electromagnetic-based technology that humans had invented in both 1859 and 1872 was the telegraph. Electric lighting, telephone, radio networks and electronics were yet to come. Not to mention television, satellites or the Internet. “A storm as intense as those would disrupt power grids, communications systems and satellite operations. As they form the basic infrastructure of our civilization, our lives can become a little more uncomfortable than usual,” Hayakawa recalls. Earlier this year, “a minor geomagnetic storm disabled about forty Starlink satellites.” [la constelación de Elon Musk]the Chapman-Silverman storm was at least an order of magnitude larger than the latter,” recalls the Japanese scientist.
The expert in space meteorology from the University of Alcalá de Henares, Mª Elena Sáiz, details what happens during an event of these characteristics: “Three types of things occur in a solar storm. One is electromagnetic radiation, which takes between seven and eight minutes to reach the Earth.” Its impact, in the ionosphere, affects radio waves, which use this layer for their propagation. “Another element is solar energetic particles. When the flare occurs, one of its products are very energetic particles.” They are different from the solar wind that constantly arrives from the star. “And then there are what we call coronal mass ejections. In addition to the flare, solar plasma is expelled and that is what impacts the Earth’s magnetosphere, entering particles into the magnetosphere.” A document from NOAA, the National Oceanic and Atmospheric Administration of the United States, estimated the amount of plasma ejected during a storm of this class at more than one billion tons.
“When the magnetic field changes and the faster it changes, the more important the effect is,” says Sáiz. During the storm, “currents that we call geomagnetically induced are produced and the entire Earth is a conductor,” he recalls. These currents can enter through the neutrals of all types of electrical transformers. “There are more harmonics, instabilities occur in the system and since it is a connected network, it is transferred to high voltage stations and substations. At a given moment, collapse may occur.” Beyond electricity (although almost everything depends on whether it always exists) there would be problems in communications, the propagation of radio waves or the connection with satellites. And beyond humans, there is increasing evidence of the impact of these events on animal life, especially in species that use the magnetic field to orient themselves, such as birds or cetaceans. In fact, some works have already linked events such as Chapman-Silverman with some of the strandings of whales and dolphins.
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