Magnetic Reconnection When the Sun’s magnetic field overlaps and interacts with that of the Earth, their field lines can align in different ways [6]. Imagine pushing two magnets with the same poles against each other with tremendous force. What will happen when the oppositely pointing field lines approach each other? Based on the idea known as “magnetic reconnection”, suggested by the Australian physicist Ronald Giovanelli in 1946, scientists discovered that misaligned magnetic fields could cause the field lines to break apart and reconnect in a whole new configuration [7, 8]. Before the reconnection occurs, as the solar wind permeated with the Sun’s magnetic field approaches the Earth, our planet’s magnetic field will be twisted, building up magnetic energy just as a stretched rubber band stores elastic potential energy. When the two fields come so close that the reconnection finally occurs, the original field lines would break up and reconnect to form a new configuration. Like suddenly letting go of the stretched rubber band, the magnetic field releases a tremendous amount of energy, accelerating the plasma particles to extremely high speeds. Due to magnetic forces, the plasma particles travel toward the poles in helical motion along the magnetic field lines, and mirror back at the poles. They therefore bounce between the poles and are trapped in regions known as the Van Allen Radiation Belts [3, 9–11]. At the poles are two holes of the Earth’s donut-shaped magnetic field, called the polar cusps, where the charged particles will be funneled downward (Figure 3) [12]. While most particles will be mirrored back at the poles, some highly energized particles will leak out of the magnetic field through the cusps and interact with molecules in the upper atmosphere of the Earth [9]. Figure 2 Artistic representation of the deflection of solar wind (greenish yellow) by the Earth’s magnetic field (blue lines). The dayside (the side facing the Sun) of the Earth’s magnetic field is compressed, while the nightside is elongated into a tail [5]. Photo credit: NASA Electron Transition and Aurora Colors The plasma particles that have arrived at the poles can then interact with the gas particles present in the Figure 3 The Earth’s donut-shaped magnetic field with the northern and southern polar cusps where the plasma particles are funneled downward toward the poles. [13]. Photo credit: Andøya Space Center/Trond Abrahamsen
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