By Sabine Stanley, Ph.D., Johns Hopkins University
Magnetosphere is a magnetic cover stretching all over the Earth’s atmosphere, protecting it from being blown away by the solar wind. This shield has created a safe space on Earth for life to emerge. But what is around and beyond this protecting bubble?
Magnetosphere is the protective field that makes life on Earth and in its atmosphere possible. This layer begins on average around 60,000 kilometers above Earth’s surface, and its altitude depends on the Sun and the Earth’s magnetic effects. To know what exactly it does, we should first know what it protects and how the phenomena under this protection work.
Learn more about the Earth-Moon system.
Human Life in Space
The International Space Station orbits the Earth in the thermosphere at altitudes in between about 330 and 420 kilometers. The station has 90% of Earth’s gravity, but is at a free-fall state as it orbits the Earth 15 times per day. Hence, the astronauts inhabiting the station can float in it. The layer is far below the magnetosphere, so the station is safe from the high-energy solar particles.
Even though life in space can lead to bone loss and changes in chromosomes’ telomeres, it is not due to the magnetic effects or solar winds. Telomeres are located at the end of the chromosomes and keep them from fraying or fusing. They shorten through aging and even cancer, but in one case-study, the low-gravity exposure in the space station made them grow longer than usual. Nevertheless, they went back to their normal size two days after returning to Earth. What else is around at that altitude?
This is a transcript from the video series A Field Guide to the Planets. Watch it now, on Wondrium.
Satellites in the Atmosphere
All artificial satellites move somewhere in the low Earth orbit, higher than the International Space Station. GRACE satellites are an example of important satellites. GRACE stands for Gravity Recovery and Climate Experiment, and they monitor Earth’s gravity field, looking for small changes in mass occurring below the satellites. The aim is to track Earth’s climate changes.
Another example is the Hubble Space Telescope. Hubble orbits at around 540 kilometers altitude, which is usually in the thermosphere or the bottom of the exosphere. Satellites have three different orbits, ranging from a few hundred kilometers to around 35,000 kilometers in altitude: low Earth orbit, medium Earth orbit, and geostationary orbit.
Learn more about human futures in the Solar System.
Satellites in Low Earth Orbit
In low Earth orbit, one network is the Iridium satellite constellation. It has 66 satellites in polar orbits at an altitude of around 780 kilometers. One satellite takes about 100 minutes to realize an orbit. The orbits are spaced 30° apart in longitude, with 11 satellites along each longitude. Thus, an excellent global coverage is created for, for example, communication via satellite phone.
Satellites in Medium Earth Orbit
In the medium orbit, satellites are at an altitude of around 20,000 kilometers, far beyond the exosphere. They orbit the Earth once a day and a familiar example is the GPS satellites: the Global Positioning System. There are about 30 GPS satellites in orbit at any given time.
Satellites in Geostationary Orbit
At the altitude of about 35,000 kilometers, satellites have an orbital speed equal to the Earth’s rotational velocity. Thus, they have a fixed location above the surface. These satellites are useful for communication, weather, or other monitoring of a specific location. However, they can stand only above the equator. Do all of these satellites work?
Space Debris and the Kessler Syndrome
The estimated number of satellites in orbit, in 2018, was about 4900. However, only 40% of them actually worked. This means the remaining 60% are space debris. Other than aimless satellites, there are pieces of working ones and rockets wandering around. There is a significant hundreds of millions of debris pieces in Earth orbit.
The debris can be a threat to functioning satellites and the International Space Station, as well as to people on the surface. With more satellites, there will be a higher chance of collisions; and with more collisions, more objects can fall to Earth. If the limit is reached, everything in orbit will collide in a chain reaction, which is called the Kessler syndrome. However, the debris is not the only threat to orbiting objects.
Learn more about how the Solar System family is organized.
How Does the Magnetosphere Work?
The magnetosphere steps in when the solar wind does. As a result of Earth’s magnetic field, the magnetosphere deflects all the solar particles bombarding the Earth and its atmosphere. Even the highest satellites are also under the coverage of the magnetosphere, or they would be destroyed easily.
Even though the magnetosphere is about 60,000 kilometers above the surface, Earth’s magnetic field reaches far beyond that, affecting the solar wind. This is called the bow shock and is located about 90,000 kilometers from the surface.
Despite this thick magnetic shield, some solar particles penetrate the magnetosphere, creating Van Allen radiation belts. These ionized particles can immediately get accelerated by spiraling around Earth’s magnetic field lines, later creating aurora. The altitude of the inner radiation belt extends from about 600 to 6000 kilometers. As Earth’s magnetic field is weaker around the South Atlantic, these radiations can be most dangerous to satellites there.
Even though the magnetosphere is a strong shield, there are other threats orbiting and floating above the Earth.
Common Questions about the Magnetosphere
The magnetosphere is a high layer of the atmosphere. As the name suggests, Earth’s magnetic field lies here, acting as a shield to the solar and cosmic particle radiation, and solar winds. Solar winds can damage and somehow ‘blow away’ the Earth’s atmosphere, but the magnetosphere prevents that.
Earth’s magnetosphere is made up of three groups of charged particles, trapped in the Earth’s magnetic field. They deflect the solar wind and act as a protecting bubble around the Earth.
The altitude of the magnetopause varies a lot, because the solar wind varies in its intensity, but is on average around 60,000 kilometers above Earth’s surface. Where the layer ends is called the magnetopause. However, this is not where the magnetic influence of the Earth stops.
The magnetosphere is the magnetic influence of Earth’s magnetic field, deep inside the planet. The magnetic effect in this layer of the atmosphere is enough to deflect the solar wind and protect everything within Earth’s atmosphere.