Reader Question – Orival Silva, Sao Jose dos Campos, SP
It happens when plasma waves from solar storms travel through space and interact with Earth’s magnetic field and atmosphere. The phenomenon can occur day and night at the two poles of the planet, although it is more easily seen in the north between August and April. When it occurs there, the phenomenon is called the aurora borealis (in the south, it is called the aurora australis). The more energy the Sun releases, the greater the chance of solar storms forming. However, the frequency with which they occur is unpredictable, and so it takes some luck to witness this beautiful spectacle of nature.
The journey of solar gases
All this beauty begins with the formation of large gas bubbles inside the Sun.
1. Can come hot
Inside the Sun, temperatures and pressures are so high that hydrogen atoms fuse and form helium gas (H2), a reaction that emits a lot of energy. All this energy is released in the form of light and heat, which push gas to the surface, forming huge eddies called convection cells. Inside them, the hottest gas rises, and the coldest gas sinks.
2. Magnetic bubbles
This charged gas inside the Sun is called plasma, and its movement generates strong magnetic currents. In some places on the Sun these currents are so strong that they make their way to the surface, break through the convection cells and “escape” into space with the plasma. It’s what we call a solar storm – a kind of cosmic fart
3. Travel with limited time
During storms, billions of tons of plasma are released from the astro-king and travel through space at about 8 thousand km per hour! In six hours they reach Mercury; after 12 hours, Venus; and finally, in 18 hours, Earth. This time does not vary, so we know precisely when we will be hit
4. During the day
Upon arriving here, the storm’s magnetic field collides with Earth’s. This union forms a kind of magnetic funnel through which solar plasma flows towards the poles of our planet. This is the diurnal aurora, visible only from space, as sunlight overshadows the colors formed in the atmosphere.
5. Night Aurora
When the storm is strong, these magnetic fields stretch further around the globe and come together again on the other side (the dark side of the planet). This «magnetic rubber band» breaks, and the plasma starts flowing again towards the poles, only now over a dark sky. It’s the nocturnal aurora, visible here from Earth
sky in color
AuroraPhenomenon tones vary with air and altitude
When electrons from solar plasma penetrate the Earth’s atmosphere, they encounter oxygen and nitrogen atoms in the air. This encounter releases energy in the form of colored lights. The colors vary according to the type of atom that collides with the electron and the altitude at which this collision occurs.
SOURCES: Exploratorium.edu, NASA and Department of Physics at the University of Oslo
Read too:
– How do the polar auroras occur?
– What is solar wind?