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I think the magnetosphere shields life for cosmic rays.

Magnetosphere

Earth’s magnetic field, predominantly dipolar at its surface, is distorted further out by the solar wind. This is a stream of charged particles leaving the Sun’s corona and accelerating to a speed of 200 to 1000 kilometres per second. They carry with them a magnetic field, the interplanetary magnetic field (IMF).[24]

The solar wind exerts a pressure, and if it could reach Earth’s atmosphere it would erode it. However, it is kept away by the pressure of the Earth’s magnetic field. The magnetopause, the area where the pressures balance, is the boundary of the magnetosphere.

Despite its name, the magnetosphere is asymmetric, with the sunward side being about 10 Earth radii out but the other side stretching out in a magnetotail that extends beyond 200 Earth radii.[25] Sunward of the magnetopause is the bow shock, the area where the solar wind slows abruptly.[24]

Inside the magnetosphere is the plasmasphere, a donut-shaped region containing low-energy charged particles, or plasma. This region begins at a height of 60 km, extends up to 3 or 4 Earth radii, and includes the ionosphere. This region rotates with the Earth.[25]

There are also two concentric tire-shaped regions, called the Van Allen radiation belts, with high-energy ions (energies from 0.1 to 10 million electron volts (MeV)).

The inner belt is 1–2 Earth radii out while the outer belt is at 4–7 Earth radii. The plasmasphere and Van Allen belts have partial overlap, with the extent of overlap varying greatly with solar activity.[26]

As well as deflecting the solar wind, the Earth’s magnetic field deflects cosmic rays, high-energy charged particles that are mostly from outside the Solar system. (Many cosmic rays are kept out of the Solar system by the Sun’s magnetosphere, or heliosphere.[27])

By contrast, astronauts on the Moon risk exposure to radiation. Anyone who had been on the Moon’s surface during a particularly violent solar eruption in 2005 would have received a lethal dose.[24]

Some of the charged particles do get into the magnetosphere. These spiral around field lines, bouncing back and forth between the poles several times per second. In addition, positive ions slowly drift westward and negative ions drift eastward, giving rise to a ring current.

This current reduces the magnetic field at the Earth’s surface.[24] Particles that penetrate the ionosphere and collide with the atoms there give rise to the lights of the aurorae and also emit X-rays.[25]

The varying conditions in the magnetosphere, known as space weather, are largely driven by solar activity. If the solar wind is weak, the magnetosphere expands; while if it is strong, it compresses the magnetosphere and more of it gets in. Periods of particularly intense activity, called geomagnetic storms, can occur when a coronal mass ejection erupts above the Sun and sends a shock wave through the Solar System.

Such a wave can take just two days to reach the Earth. Geomagnetic storms can cause a lot of disruption; the “Halloween” storm of 2003 damaged more than a third of NASA’s satellites. The largest documented storm occurred in 1859. It induced currents strong enough to short out telegraph lines, and aurorae were reported as far south as Hawaii.[24][28]

https://en.wikipedia.org/wiki/Earth%27s_magnetic_field#Magnetosphere