A geomagnetic storm G2 category (therefore “moderate” according to the official Noaa classification) has invested the earth, producing the show of the Boreal Aurore In high latitudes with sightings in Scotland, Canada and New Zealand between 1st and 2 September. Curiously, the geomagnetic storm took place on the occasion of the anniversary of theCarrington eventthe most intense geomagnetic storm of which we testify, which took place in 1859. That of recent days was a much weaker event, which did not produce particular consequences. The terrestrial magnetic field disorder was not intense enough to create aurore sightings in Italy; However, the digital eyes of panoramic webcams have observed auroral phenomena along the Alpine arc. Here for example aAurora Rossa observed in Austria at 1:30 on 1 September.
However, the peculiarity of the boreal aurore observed is another: the color. As reported by the reference portal Spaceweather.comin fact, a large part of the sighted boreal aurores was violaa color that we typically do not associate with this atmospheric phenomenon, which is generally green with higher latitudes and red in our latitudes.
The color of a polar god It depends on which chemical element in the atmosphere interacts with the “fired” particles from the sun that the earth’s magnetic field deflects towards the poles thus giving rise to the polar lights. It works pressed like this: solar particles arrive in our atmosphere at very high speed, then bringing with them a considerable amount of energy. When one of these particles “clashes” with an atom of our atmosphere, it can overflow to this latter part of its energy, which the atom then release in the form of light. Which is precisely the light we observe during a northern lights.
Typically to interact with the plasma arriving from the sun is theoxygenin its version atomic (i.e. individual atoms) or molecular (i.e. in the form of a molecule of O2). Atomic oxygen, if excited, emits light red (from which the red lights), while the molecular one emits light green. But as we know, the most abundant element in the atmosphere is thenitrogenpresent above all in the form of a biatomic molecule (N2). Well, this molecule once excited responds by emitting light blue/purple. Compared to oxygen, nitrogen is much less inclined to interact with the charged particles that come from the sun, therefore the purple lights are rather rare. So why have so many be spotted in the last two nights?
The answer is that we don’t know. Generally the purple aurores are associated with very energetic geomagnetic storms, precisely for the relative “laziness” of nitrogen with respect to oxygen to be stimulated by the sun wind. But the geomagnetic storm of 1-2 September it was not particularly intense (It was in category G2 on a staircase ranging from G1 to G5), therefore theoretically it should not have produced so much purple. This little mystery reminds us how much there is still to be understood on the subject of Space meteorology.
