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Dust devils and dust storms | Thunderstorms, lightning and tornadoes Hurricanes and great spots | Space weather and solar winds
From Earth, space weather is very hard to spot. But now and again you can witness its strange effects: the amazing colours of the Northern and Southern Lights; sudden blackouts of mobile phone and other radio communications; total breakdown of power supply and distribution systems. All are signs of dramatic changes in the space weather that originate in the Sun, the stormiest place in the solar system. The outer region of the Sun's dense atmosphere constantly releases a huge stream of charged particles which blast into space in every direction at a million miles per hour, reaching the edge of the solar system and perhaps beyond. The Earth, all the planets, and any orbiting moons and spacecraft are constantly bathed in this solar wind, which travels through space at more than a million miles per hour (1.6mkph). From once a week to as often as three times a day, a coronal mass ejection or solar flare throws out an extra ten billion tons of ionised gas - the biggest and most violent weather event in the solar system. Each one equal to a billion hydrogen bombs going off at once. Like a shock wave travelling through the solar wind, the gas travels outwards, posing a threat to anything in its path. As it hurtles through space, it sets off geomagnetic storms that can damage satellites and spacecraft. Sometimes the Earth is in the direct line of fire. Normally the solar wind is deflected around the Earth's atmosphere. But geomagnetic storms distort the Earth's magnetic field and some of the particles are funnelled into the polar regions where they collide with air molecules just 25 miles (40km) from the ground, creating the weird visual effects we know as Aurora Borealis (the Northern Lights) and Aurora Australis (the Southern Lights). The magnetic interactions also cause radio and TV interference, and magnetic surges which can shut down mobile phone networks and electric power grids. The Earth's atmosphere and magnetic field protect us from the worst effects of the solar wind and geomagnetic storms. But, on our moon, there's no protection at all. The thin atmospheres and tiny magnetic fields on Mars and Mercury provide very little protection; Pluto and Venus have no protection at all. The outer planets - Jupiter, Saturn, Uranus and Neptune - have dense atmospheres and strong magnetic fields which offer much better protection. |
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