NASA Goddard Space Flight Center
The Earth’s magnetosphere, immersed in the solar wind, compresses the side of the magnetosphere facing the Sun and stretches the opposite side, moving it away from the Earth, forming the magnetic tail (artistic concept)
According to some estimates, this “magnetotail” could even extend up to a thousand times the radius of the Earth — around 6.3 million kilometers.
Comets, like the infamous one roaming our solar system, are not the only cosmic objects that develop tails. Also the planets they can have it.
This is the case, for example, of our neighbor, whose origin can be explained by the properties of the planet’s own exosphere, rich in sodium, which, when dragged by the solar winds, takes on a faint orange glow.
And this raises the question: Does the Earth also have a? The short answer is simand that tail extends at least 2 million kilometers in spacebehind our planet.
Let’s start with the simplest case. Mercury has an extremely thin atmosphere, but there are small amounts of sodiumwhich can be pushed by the force of the Sunthere dangerously close.
“The sunlight scattersThe sodium gives an intense orange glow. This dispersion process also gives a ‘push’” to the sodium atoms, and this ‘radiation pressure’ is strong enough, at certain times of the year, to rip off part of the atmosphere and give the planet a long glowing tail“, a NASA.
“Someone standing on the night side of Mercury at the right time of year would see a faint orange glowsimilar to the sky of a city lit by sodium lamps.”
Returning to Earth’s tail. This one is a little less obvious than Mercury’s sodium tail, but it exists and stretches out behind us, on the night side of the planet.
All macroscopic objectsfrom magnets themselves to bizarre Antarctic animals that can live for more than 11,000 years, are a little magneticdue to the rotation of its electrons, which generates magnetic dipole moments, like micro-magnets, explains .
In most materials, these rotations are not aligned and end up canceling each other out, leaving a Practically zero net magnetization. But in magnetic materials, they can align in the same direction and the result is a magnetwith a magnetic field and north and south poles.
The Earth has its own magnetic fieldpowered by geodynamic processes in the outer core, through the movement of iron and nickel in a liquid state.
“The region traversed by the Earth’s magnetic field, called , dominates the behavior of electrically charged particles in space near the Earth and protects the planet from the solar wind“, explains NASA, adding that the magnetosphere traps plasma, or ionized gas.
It is precisely this trapped plasma in the Earth’s magnetosphere that forms the Earth’s “tail,” as some of this plasma is pulled in and flows away from the Sun.
Astrophysicists believe that the tail is a plasma return flow which occurs when the solar wind, a stream of plasma continually ejected from the solar surface, lashes the magnetosphere and distorts its shape.
For example, a falling raindrop It starts out being approximately spherical. As it falls and gains speed, air resistance causes the droplet to change shape as water is dragged from the bottom (head) to the top (tail).
Surface tension prevents most of the water from simply dispersing through the tail, forcing it to circulate within the droplet itself and returning to the head”, describes NASA.
“Solar wind distorts Earth’s magnetosphere in a similar way, compressing it on the day side, like the head of a raindrop. The region is stretched on the night side, like the tail of this drop, forming a teardrop-shaped structure.”
The Earth’s tail is known as magnetocauda. Although it is generally a permanent structure, is subject to the whims of the solar wind. In April 2023, for example, a particularly intense Coronal Mass Ejection (CME) “torn off” the tail of the Earth.
Despite variations in the size and shape of the magnetosphere, the solar wind is thought to drag our magnetotail for distances that can reach more than a thousand times the radius of the Earth — about 6.3 million kilometers. However, it remains difficult to know exactly how far it extends.
“Although our Earth’s tail has been explored by countless space probes in recent decades, many mysteries remain“, the European Space Agency, ESA.
