Polar Aurora

Article

July 5, 2022

The polar aurora or northern lights is an optical phenomenon of the earth's atmosphere, mainly characterized by light bands of a wide range of shapes and colors rapidly changing over time and space, typically red-green-blue in color, called auroral arcs , caused by the interaction of charged particles (protons and electrons) of solar origin (solar wind) with the terrestrial ionosphere (atmosphere between 100-500 km): these particles excite the atoms of the atmosphere which, de-energizing later, emit light of various wavelengths. It is called "Northern Lights" or "Southern" depending on whether it occurs in the Northern (Boreal) or Southern (Southern) hemisphere respectively.

History

On August 28, 1859, some auroras were sighted along a large area of ​​American territory. In scientific centers around the world, the instrumentation underwent strong and inexplicable variations and spurious currents formed in the telegraph lines. The following day, the English astronomer Richard Christopher Carrington noticed a group of sunspots of unusually large size, from which a flash of whitish light emanated, which after a few hours produced a second wave of auroras of great intensity. With the "Great Aurora" of 1859, the models of explanation of the phenomena of solar activity evolved rapidly and the ancient hypotheses of flashes at high altitudes, or of light reflected from icebergs were replaced by those more related to solar events and perturbation. Storms of this intensity are estimated to occur every 500 years. The last event of half the intensity of 1859 occurred in 1960 causing radio outages across the planet. Experts believe that the costs of a possible super storm could be comparable to those of a major earthquake, should the appropriate countermeasures be lacking, such as postponing some delicate activities carried out by satellites, moving air routes, identifying vulnerable elements in advance. networks. The solar magnetic activity, and therefore also the formation of sunspots, varies cyclically every eleven years. The new cycle began in January 2008, so it is reasonable to expect an increase in activity over the next few years. Over the past eleven years, scientists have detected about 21,000 flares and 13,000 clouds of plasma escaping from the solar surface. In Italy the visibility of the northern lights is quite rare, but in the night between 17 and 18 November 1848 the phenomenon was so intense and extensive that it was visible even at low latitudes. In Naples it was observed by the astronomers of the Capodimonte Astronomical Observatory and by Mario Patrelli, director of the Marina Observatory; in addition, the painter Salvatore Fergola created two paintings from the Capodimonte Observatory. In Rome the phenomenon had great echo, as evidenced by the article published in the magazine L'bum which describes in detail the astronomical event and the surprise of the Romans.

Description

How it's made

The shape of a polar aurora is very diverse. Arcs and brilliant rays of light begin from above the earth's surface and extend upwards along the magnetic field for hundreds of kilometers. Arches can be very thin, even as little as 100 meters, while extending from horizon to horizon. They can be almost motionless and then, as if a hand has passed over a long curtain, begin to move and twist. After midnight, the aurora can take a speckled shape and each of the spots often flashes roughly every 10 seconds, and is a greenish yellow, but sometimes the rays can turn red (at most yellow) at the top and along the bottom edge. On very rare occasions, sunlight can hit the top of the rays creating a faint blue color. Even more rarely (once every 10 years or more) the aurora can be blood red. This is