By Sabine Stanley, Ph.D., Johns Hopkins University The magnetosphere is what protects the Earth and everything in its orbit from high-energy solar particles that can destroy the atmosphere. (Image: IRINA SHI/Shutterstock)

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 Earths surface, and its altitude depends on the Sun and the Earths 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.

The InternationalSpace Station orbits the Earth in the thermosphereat altitudes in between about 330 and 420 kilometers. The station has 90% ofEarths gravity, but is at a free-fall state as it orbits the Earth 15 timesper day. Hence, the astronauts inhabiting the station can float in it. Thelayer is far below the magnetosphere, so the station is safe from thehigh-energy solar particles.

Even though lifein 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 atthe end of the chromosomes and keep them from fraying or fusing. They shortenthrough aging and even cancer, but in one case-study, the low-gravity exposurein the space station made them grow longer than usual. Nevertheless, they wentback to their normal size two days after returning to Earth. What else isaround at that altitude?

This is a transcript from the video series A Field Guide to the Planets. Watch it now, on The Great Courses Plus.

All artificialsatellites move somewhere in the low Earth orbit, higher than the InternationalSpace Station. GRACEsatellites are an example of important satellites. GRACE stands for Gravity Recovery and Climate Experiment, and they monitor Earthsgravity field, looking for small changes in mass occurring below thesatellites. The aim is to track Earths climate changes.

Another example is the Hubble SpaceTelescope. Hubble orbits at around 540 kilometers altitude, which is usually inthe 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.

In low Earth orbit, onenetwork is the Iridium satellite constellation. It has 66 satellites in polarorbits at an altitude of around 780 kilometers. One satellite takes about 100minutes to realize an orbit. The orbits are spaced 30 apart in longitude, with11 satellites along each longitude. Thus, an excellent global coverage is createdfor, for example, communication via satellite phone.

In the medium orbit, satellites are atan altitude of around 20,000 kilometers, far beyond the exosphere. They orbitthe Earth once a day and a familiar example is the GPS satellites: the GlobalPositioning System. There are about 30 GPS satellites in orbit at any giventime.

At the altitude of about 35,000kilometers, satellites have an orbital speed equal to the Earths rotationalvelocity. Thus, they have a fixed location above the surface. These satellitesare useful for communication, weather, or other monitoring of a specificlocation. However, they can stand only above the equator. Do all of thesesatellites work?

The estimatednumber of satellites in orbit, in 2018, was about 4900. However, only 40% ofthem actually worked. This means the remaining 60% are space debris. Other thanaimless satellites, there are pieces of working ones and rockets wanderingaround. There is a significant hundreds of millionsof 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.

The magnetospheresteps in when the solar wind does. As a result of Earths magnetic field, themagnetosphere deflects all the solar particles bombarding the Earth and itsatmosphere. Even the highest satellites are also under the coverage of themagnetosphere, or they would be destroyed easily.

Even though themagnetosphere is about 60,000 kilometers above the surface, Earths magneticfield reaches far beyond that, affecting the solar wind. This is called the bowshock and is located about 90,000 kilometersfrom the surface.

Despite this thick magnetic shield,some solar particles penetrate the magnetosphere, creating Van Allen radiationbelts. These ionized particles can immediately get accelerated by spiralingaround Earths magnetic field lines, later creating aurora. The altitude of theinner radiation belt extends from about 600 to 6000 kilometers. As Earthsmagnetic field is weaker around the South Atlantic, these radiations can bemost dangerous to satellites there.

Even though themagnetosphere is a strong shield, there are other threats orbiting and floatingabove the Earth.

The magnetosphere is a high layer of the atmosphere. As the name suggests, Earths 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 Earths atmosphere, but the magnetosphere prevents that.

Earths magnetosphere is made up of three groups of charged particles, trapped in the Earths 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 Earths 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 Earths 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 Earths atmosphere.

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Magnetosphere: Satellites, Space Debris, and What Else? - The Great Courses Daily News