The Northern Lights have long fascinated the public and experts. But the most surprising, perhaps, is that there are several different types of this atmospheric phenomenon. So, on January 29, the University of Helsinki announced that a group of amateur astronomers discovered a new form of the northern lights, which was called “dunes”. This form of oxygen atoms, which shine from a stream of charged particles emanating from the Sun, at an altitude of about a hundred kilometers. Outwardly, the radiance really resembles waves or sand dunes. The work can be found in the magazine AGU Advances.
What is the northern lights?
Aurora is called atmospheric phenomenon, which occurs at the moment when charged particles – for example, electrons – are emitted by the Sun and are sent to the poles of the Earth by the magnetic field of our planet. There they interact with gases in the atmosphere, including oxygen and nitrogen, increasing the energy of these gases. It is this energy that subsequently manifests itself in the form of light. Minna Palmrot, a professor of computational physics in space at the University of Helsinki, told The Guardian that the northern lights, in fact, are neon sky lamps.
The work of amateur astronomers who discovered a new form of this atmospheric phenomenon, scientists call an amazing discovery. The fact is that it is born quite high – about a hundred kilometers – and this area has not been practically explored in the past because it is very difficult to conduct observations of the area that separates the electrically neutral part of the atmosphere from the ionosphere. The distance between the waves, according to researchers, is about 45 kilometers. In total, “dunes” were recorded 7 times.
According to Palmrot, “dunes” are formed by analogy with ripples in the water when we throw a stone into a pond. The green glow appears due to the heterogeneity in the distribution of oxygen atoms in the mesosphere, which causes disturbances in the atmosphere. In the atmosphere, however, waves often move vertically upward – and there are many. Moreover, the waves have different frequencies, lengths and amplitudes, so observing something very uniform, such as dunes, means that there must be some kind of active mechanism that can make them like that. This mechanism may turn out to be the mesospheric channel, as a result of which a particular wave is filtered out and bent, which allows it to move horizontally between two layers in the atmosphere.
In general, an unusual atmospheric phenomenon of the “dune” can occur when the temperature of one layer of the atmosphere is slightly higher than the temperature of both layers above and below it. As the researchers write in their work, such an unusual appearance is caused by waves that create peaks and troughs in the density of oxygen.