The Sun’s corona, the outer atmosphere of the Sun, is the source of the solar wind, where charged particles flow steadily from the Sun. These particles contain enough energy to spread throughout the entire heliosphere (a region extending beyond Pluto’s orbit). As these particles stream past Earth’s orbit, they travel at an average speed of 400 kilometres per second. The Sun can lose more than a million tons of particles per second, but that amount is tiny compared to the Sun’s total mass.
The solar wind consists primarily of roughly equal numbers of protons and electrons, as well as a few heavy ions. The velocity of these particles is greater when they pass above the solar coronal holes, and regions near the Sun’s poles, where “open” magnetic field lines exist, allowing these particles to flow easily into space. These particles flow out very slowly near the Sun’s equator, where the magnetic field lines extend only between its poles, causing the particles (coronal material) to become trapped.
Earth’s magnetic field shields our planet from the solar wind, and this magnetosphere deflects the solar wind away from us. Due to the pressure exerted by the solar wind on our magnetic field, the Earth’s magnetic field is compressed on the side facing the Sun. On the opposite side, it extends as a magnetotail.
In some cases, these charged particles of the Sun enter the Earth’s magnetic field (magnetosphere) and spiral along the Earth’s magnetic field lines and near the poles, interacting with particles in the Earth’s upper atmosphere to create auroras.
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