From there, they periodically are violently ejected into the northern and southern polar regions of the atmosphere along the Earth's magnetic field and are accelerated to high speeds by a process not yet fully explained. The magnetotail is in effect a reservoir of particles that is periodically refilled. When the Sun is active during maximum sunspot years, this process is especially intense and frequent, and the aurorae are brighter and move closer to the equator. Northern lights, a gift from the Sun. This brilliant green display of the aurora borealis, photographed from Fairbanks, Alaska, resembles a huge curtain with a circular fold.
Colors range from white through green, blue, and red.
Other planetary magnets Space probes have discovered that three other planets besides the Earth have magnetic fields strong enough to form magnetospheres around them. The magnetospheres of these planets, tiny Mercury, giant Jupiter, and ringed Saturn, are as different as the planets themselves. Mercury's magnetosphere is much smaller and weaker than the Earth's, while Jupiter's very strong magnetic field has trapped particles in a violently active magnetosphere so large that, if visible from Earth, it would appear as big as the full Moon. Saturn's magnetosphere is intermediate between those of the Earth and Jupiter. Comparative studies of the magnetic fields and magnetospheres of the planets should help us interpret the origin of the Earth's magnetosphere and its as sociated phenomena, and to understand why some planets apparently do not generate their own magnetic fields.