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Space weather in the solar system

Space weather is a term that describes the dynamic and unpredictable conditions in the space environment that can affect human technology and infrastructure.

Space weather includes the effects of solar activity and high-energy radiation on a planet’s magnetic field and atmosphere. We are usually interested in the space weather near the Earth, because it affects satellites and other activities in orbit, as well as aviation, power grids, and communication systems on the ground.

Space weather effects and hazards. Credit: ESA/Science Office

Near other planets and moons, space weather “feels different”, depending on the distance from the Sun and the existence or absence of a magnetic field and an atmosphere.

Let us look at distance from the Sun first. Astronomers measure distances in the solar system in astronomical units (AU). The Earth-Sun distance is 1 AU. The Moon is at about the same distance from the Sun, also 1 AU, while Mars is at 1.5 AU, and Jupiter and its moons are at 5.2 AU.

Solar wind, solar flares and solar coronal mass ejections are all phenomena that originate in the Sun, travel through space and potentially impact other objects. The further from the Sun, the weaker their effects. In theory, Jupiter is safer than Mars, which is safer than the Earth-Moon system.

Image: L. Han (International Atomic Energy Agency)

But then we have to consider magnetic fields. The Earth, and Jupiter and its moons Ganymede, Europa and Callisto all have magnetic fields. while the Moon and Mars do not. The magnetic field envelops each planet and moon in a sort of bubble called magnetosphere. This bubble acts as a big fishing net, which can grab the “stuff” coming from the Sun. The “stuff” consist of electrons, protons, and other charged particles which can get trapped in donut-shaped radiation belts around each planet, and travel along the magnetic field lines and land near the poles. This causes beautiful auroras (good) and geomagnetic storms which can cause lots of damage (bad).

Jupiter’s magnetic field is tremendous — 10,000 times larger and 20,000 times stronger than the Earth’s. The magnetospheres of Jupiter’s moons are like small bubbles inside the big bubble, which combine to create a really complex system. So, even though Jupiter is further from the Sun, it “catches” much more of the solar weather coming from the Sun. This leads to a violent environment of charged particles that can hit anything in the Jupiter system.

This will be the environment that the JUICE spacecraft will have to face. On one hand, it will be a wonderful opportunity to map out the properties of the radiation. On the other hand, the spacecraft, instruments and electronics need suitable protection from radiation damage.

Complex magnetosphere of the Jupiter system.

The last factor is the presence of atmospheres, which act as a shield, not only from the charged particles, but from radiation from the Sun and from outside the solar system. The Moon and Mars have little or no protection, and neither do Ganymede, Europa and Callisto. The Earth’s atmosphere protects us on the surface.

Effective management of space weather risks requires a combination of monitoring, prediction, and mitigation strategies, as well as the development of resilient technology and infrastructure. Satellites in Earth’s orbit must be properly shielded for space weather, and must keep watching it and activate protection modes when it gets really aggressive.

Furthermore, If we are ever to live on the surface of the Moon or on Mars, we need to find ways to protect ourselves and our technology from space weather.

At Jupiter, where the JUICE spacecraft will be carrying its mission, space weather is extremely violent. Radiation is intense and extra care was put into protecting the solar panels and some of the instruments, such as the GALA altimeter.

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