Almost everyone has heard of or seen photographs of the Northern Lights. Some have been lucky enough to see them in person. But many are unaware. how they are formed and because.
An aurora borealis begins with a fluorescent glow on the horizon. Then it diminishes and an illuminated arc arises, sometimes closing in a very bright circle. But how is it formed and what is its activity related to?
Formation of the Northern Lights
The formation of the northern lights is related to the solar activity, the composition and characteristics of the Earth's atmosphere. To better understand this phenomenon, it is interesting to read about space hurricanes and how these influence the generation of northern lights.
The northern lights can be observed in a circular area above the poles of the Earth. But where do they come from? They come from the Sun. There is a bombardment of subatomic particles from the Sun formed in solar storms. These particles range from purple to red. The solar wind alters the particles and when they meet the Earth's magnetic field they deviate and only part of it is seen at the poles.
The electrons that make up solar radiation produce a spectral emission when they reach the gas molecules found in the magnetosphere, part of Earth's atmosphere that protects Earth from the solar wind, and cause excitation at the atomic level that results in luminescence. That luminescence spreads throughout the sky, giving rise to a spectacle of nature.
Studies on the Northern Lights
There are studies that investigate the auroras when solar wind is produced. This occurs because, although it is known that solar storms have an approximate period of 11 years, it's not possible to predict when the Northern Lights will appear. For all those who want to see the Northern Lights, this is a nuisance. Traveling to the poles isn't cheap, and not being able to see the aurora is very depressing. In addition, it can be helpful to know the northern lights in Spain for those who cannot travel far.
To understand how the northern lights form, it is essential to understand the two key elements involved in their creation: the solar wind and the magnetosphere. The solar wind is a stream of electrically charged particles, primarily electrons and protons, emitted from the solar corona. These particles travel at impressive speeds, which can reach up to 1000 km/s, and are transported by the solar wind into interplanetary space.
The magnetosphere, for its part, acts as a shield, protecting the Earth from most particles in the solar wind. However, in the polar regions, the Earth's magnetic field is weaker, allowing some particles to penetrate the atmosphere. This interaction is most intense during geomagnetic storms, when the solar wind is strongest and can cause disturbances in the magnetosphere.
Interaction of particles with the Earth's atmosphere
When charged particles from the solar wind penetrate the Earth's atmosphere, they interact with the atoms and molecules present therein, primarily oxygen and nitrogen. This interaction gives rise to the aurora borealis, generating the colors and shapes we see in the sky. Solar particles transfer energy to the atoms and molecules in the atmosphere, exciting them and bringing them to a higher energy state.
Once atoms and molecules reach this excited state, they tend to return to their ground state, releasing the additional energy in the form of light. This process of light emission is what produces the characteristic colors of the northern lights. The wavelength of the emitted light depends on the type of atom or molecule involved and the energy level reached during the interaction, which can be explored further in the layers of the Earth's atmosphere.
Oxygen is responsible for the two primary colors of the auroras. Green/yellow occurs at an energy wavelength of 557,7 nm, while the redder and purpler color is produced by a less frequent length in these phenomena, 630,0 nmIn particular, it takes almost two minutes for an excited oxygen atom to emit a red photon, and if one atom collides with another during that time, the process can be interrupted or terminated. Therefore, when we see red auroras, they are most likely to be found in the highest levels of the ionosphere, approximately 240 kilometers high, where there are fewer oxygen atoms to interfere with each other.
Colors and gases: oxygen and nitrogen
The colors of the aurora borealis are the result of the interaction of solar particles with different gases in the Earth's atmosphere. Oxygen and nitrogen are primarily responsible for the variety of hues we observe in the sky during an aurora borealis. Oxygen, when excited by solar particles, can emit green or red light, depending on the altitude at which the interaction occurs. At lower altitudes, around 100 kilometers, oxygen emits green light, while at higher altitudes, around 200 kilometers, it emits red light. For a more complete understanding of this phenomenon, it is recommended to read about the cold on clear nights, which is when these auroras are most visible.
Nitrogen, for its part, contributes to the blue and purple hues of the aurora borealis. When solar particles excite nitrogen molecules, they can emit blue or purple light, creating a contrast with the colors produced by oxygen. The combination of these colors gives rise to the impressive multi-colored auroras that illuminate the night sky in the polar regions.
The colors of the northern lights
Although the aurora borealis is commonly associated with a bright green color, it can actually occur in a variety of colors. Green is the most common due to the excitation of oxygen atoms at about 100 kilometers above the surface. However, At different altitudes and with different types of gases, other colors may appear:
- Green color: produced by the excitation of oxygen at 100 km altitude.
- Red color: generated by oxygen at higher altitudes, around 200 km.
- Blue color: caused by the interaction of solar particles with nitrogen.
- Purple color: also a result of nitrogen excitation, which adds contrast to green and red lights.
Auroras on other planets
Auroras are not exclusive to Earth. Thanks to observations made by the Hubble Space Telescope and space probes, we have been able to detect auroras on other planets in the solar system, such as Jupiter, Saturn, Uranus, and Neptune. Although the basic mechanism for formation of auroras is similar on all these planets, there are notable differences in their origin and characteristics. To better understand these differences, one can research spectacular weather phenomena.
On Saturn, the auroras are similar to those on Earth in terms of their origin, as they also result from the interaction between the solar wind and the planet's magnetic field. However, on Jupiter, the process differs due to the influence of the plasma produced by the moon Io, which contributes to the formation of intense and complex auroras. These differences make the study of auroras on other planets a fascinating field of research, allowing us to better understand the physical processes occurring in the solar system.
The auroras on Uranus and Neptune also exhibit distinctive features, due to the tilt of their magnetic axes and the composition of their atmospheres. These divergences in the structure and dynamics of these planets' magnetic fields influence the shape and behavior of the auroras, offering an opportunity to explore how these phenomena change in different planetary environments.
In addition, auroras have been detected on some of Jupiter's satellites, such as Europa and Ganymede, suggesting the presence of complex magnetic processes on these celestial bodies. In fact, auroras were observed on Mars by the Mars Express spacecraft during observations conducted in 2004. Mars lacks a magnetic field analogous to Earth's, but it does possess local fields, associated with its crust, which are responsible for the auroras on this planet.
This phenomenon has also recently been observed on the Sun. It involves auroras produced by electrons accelerating through a sunspot on the surface. There is also evidence of auroras on other stars. This highlights the importance of the auroras beyond our planet, as they provide vital information about the magnetic fields and atmospheres of other celestial bodies.
Observing the Northern Lights
Witnessing the Northern Lights is an unforgettable experience, although it requires planning and patience. To improve your chances of seeing them, it is essential to choose the favorable time and locationBetween mid-August and April, nights are longer and darker in polar regions, increasing the likelihood of seeing this phenomenon. For those interested in the subject, it is useful to review Information about Kiruna, the city of the Northern Lights.
The best regions for observing the Northern Lights include Norway, Iceland, Finland, Sweden, Canada, and Alaska, where clear skies and weather conditions favor the spectacle. It is advisable to look for places away from cities to avoid light pollution and enjoy better vision. If you'd like to learn more, check out The spectacular Northern Lights storm in Canada.
In addition, it's crucial to prepare for the cold and wear appropriate clothing for low temperatures. Patience plays an important role, as auroras can appear and dissipate quickly. Staying informed about geomagnetic activity forecasts and having a suitable camera help capture this phenomenon in all its splendor.
However, climate change has also begun to affect the visibility of the auroras. Rising temperatures and melting polar ice can impact the density and composition of the atmosphere, potentially altering how the auroras are seen from Earth's surface. Furthermore, increasing light pollution in urban areas makes viewing this natural phenomenon difficult, making it necessary to travel to remote areas to fully enjoy the experience.
The Northern Lights are a reminder of the majesty and complexity of our universe. As we advance in our understanding of these phenomena, a range of opportunities opens up to explore their mesmerizing beauty and the physical processes behind them.
