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Do you know what is this?
Do you think it is harmless or dangerous?
Why it happens?
Where it happens?

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Aurora are colorful lights in the night time sky primarily appearing in Earth's polar regions. But what causes them? The culprit behind aurora is our own Sun and the solar plasma that is ejected during a magnetic event like a flare or a coronal mass ejection.

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The geographical North and South Poles, magnetic North and South Poles.
The Earth: a giant bar magnet: the top side of this magnet is South Pole (white), and the low part is North pole (red)!

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High energy charged particles rain in on the Earth from all directions, most of them produced by the Sun.  If it weren’t for the Earth’s magnetic field we would be subject to bursts of radiation on the ground that would be, at the very least, unhealthy.  The more serious, long term impact would be the erosion of the atmosphere.  Charged particles carry far more kinetic energy than massless particles (light), so when they strike air molecules they can kick them hard enough to eject them into space.  This would cause the erosion of the atmosphere.
A recent experiment that proved the importance of Earth's magnetic field.

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Earth's magnetic field provides vital protection

A chance alignment of planets during a passing gust of the solar wind has allowed scientists to compare the protective effects of Earth's magnetic field with that of Mars' naked atmosphere. The result is clear: Earth's magnetic field is vital for keeping our atmosphere in place.

The alignment took place on 6 January 2008. Using ESA's Cluster and Mars Express missions to provide data from Earth and Mars, respectively, scientists compared the loss of oxygen from the two planets' atmospheres as the same stream of solar wind hit them. This allowed a direct evaluation of the effectiveness of Earth's magnetic field in protecting our atmosphere.

They found that while the pressure of the solar wind increased at each planet by similar amounts, the increase in the rate of loss of martian oxygen was ten times that of Earth's increase.

Such a difference would have a dramatic impact over billions of years, leading to large losses of the martian atmosphere, perhaps explaining or at least contributing to its current tenuous state.

The result proves the efficacy of Earth's magnetic field in deflecting the solar wind and protecting our atmosphere.

"The shielding effect of the magnetic field is easy to understand and to prove in computer simulations, thus it has become the default explanation," says Yong Wei from the Max-Planck-Institut für Sonnensystemforschung, Germany, who led the study.

Now, by making measurements during a planetary alignment when the two planets were being hit by exactly the same part of the solar wind, the team have proved it in reality.

They now hope to extend their work by incorporating data from ESA's Venus Express spacecraft, which also carries a sensor that can measure the loss of its atmosphere.

Venus will provide an important new perspective on the issue because like Mars, it has no global magnetic field, yet it is similar in size to Earth and has a much thicker atmosphere.

It will therefore provide unique data to help place the Earth and Mars results in context.

There are a number of upcoming planetary alignments that will provide good opportunities for such studies.

"For the next few months there is a good alignment between the Sun, Earth, Venus and Mars, and observations made by many spacecraft, including Mars Express, Venus Express and NASA's STEREO solar observatory, will be analysed together," says Olivier Witasse, ESA Mars Express Project Scientist.

Cluster will continue to play an important role in these studies, too. It is the only mission in near-Earth space capable of taking such measurements.

In addition, scientists are keen to observe how the increase in solar activity associated with the current solar cycle may affect the loss of atmospheric particles from all three planets.

"The European family of Solar System missions, with their unique observational capabilities, will play a vital role in studying this behaviour during the approaching maximum in solar activity," says Matt Taylor, ESA Cluster Project Scientist.

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Earth's magnetic field provides vital protection

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A chance alignment of planets during a passing gust of the solar wind has allowed scientists to compare the protective effects of Earth's magnetic field with that of Mars' naked atmosphere. The result is clear: Earth's magnetic field is vital for keeping our atmosphere in place.

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The Aurora is an incredible light show caused by collisions between electrically charged particles released from the sun that enter the earth’s atmosphere and collide with gases such as oxygen and nitrogen. The lights are seen around the magnetic poles of the northern and southern hemispheres.
Auroras that occur in the northern hemisphere are called ‘Aurora Borealis’ or ‘northern lights’ and auroras that occur in the southern hemisphere are called ‘Aurora Australis’ or ‘southern lights’.
Auroras are the result of collisions between gaseous particles (in the Earth’s atmosphere) with charged particles (released from the sun’s atmosphere). Variations in colour are due to the type of gas particles that are colliding. The most common aurora colour which is green, is produced by oxygen molecules located about 60 miles above the earth. The rarer red auroras are produced by high-altitude oxygen, at heights of up to 200 miles. Nitrogen produces blue or purple aurora.

When the charged particles (electrons and protons) are blown towards the earth by the solar wind, they are largely deflected by the earth’s magnetic field. However, the earth’s magnetic field is weaker at either pole and therefore some particles enter earth’s atmosphere and collide with gas particles. These collisions emit light that we perceive as the dancing lights of Auroras.
Because the phenomena occurs near the magnetic poles, getting as close to these poles as possible will rapidly increase the chances of viewing aurora. As the magnetic south pole is in Antarctica, unless your a scientist working there, it usually leaves the northern hemisphere the most sensible option of viewing aurora. It should be mentioned however that during strong solar storms, aurora australis are quite often visible in places south from Australia. But generally speaking, the best places to watch the aurora are usually are North America or Europe.

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Food for Thought: Magnetosphere also protects our atmosphere!

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Food for Thought: Magnetosphere also protects our atmosphere!

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What happens on the other planets on the Solar System?
Do they have a magnetic field?
What would learning about the magnetic field of other planets do for us?

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Earth has a magnetic field. If you imagine a gigantic bar magnet inside of Earth, you'll have a pretty good idea what Earth's magnetic field is shaped like. Of course, Earth DOESN'T have a giant bar magnet inside it; instead, our planet's magnetic field is made by swirling motions of molten iron in Earth's outer core.

Earth has two geographic poles: the North Pole and the South Pole. They are the places on Earth's surface that Earth's imaginary spin axis passes through. Our planet also has two magnetic poles: the North Magnetic Pole and the South Magnetic Pole. The magnetic poles are near, but not quite in the same places as, the geographic poles. The needle in a compass points towards a magnetic pole. When you are far away from a pole a compass is very helpful if you want to find your way around. The compass needle points pretty much due North (or South if you live in the Southern Hemisphere!). However, if you are near either pole, a compass becomes useless. It points towards the magnetic pole, not the true geographic pole. Those two poles could be quite far apart, and in different directions. Think how hard it must have been for early explorers to find their way around in the Arctic and Antarctic without being able to use a compass!

Earth's magnetic field is tilted a little bit. If we pretend that Earth's magnetic field is made by a giant bar magnet, that bar magnet would make an angle with Earth's spin axis. That angle is about 11°. That's why the magnetic poles and the geographic poles are not in the same place. If you were standing at one of the magnetic poles, the magnetic field lines would be straight up and down. If you were holding a compass and turned it sideways, its needle would aim straight up and down!

Earth's magnetic poles are actually pretty far from its geographic poles. In 2005, the North Magnetic Pole (NMP) was about 810 km (503 miles) from the Geographic North Pole. The NMP was in the Arctic Ocean north of Canada. The South Magnetic Pole (SMP) was about 2,826 km (1,756 miles) from the Geographic South Pole. The SMP was off the coast of Antarctica in the direction of Australia.

Did you notice how we said where the magnetic poles were in 2005? Guess what; the magnetic poles actually move around! Remember, swirling motions of molten metal in Earth's outer core make our planet's magnetic field. Those swirling motions are changing all the time. That means the magnetic field is changing, so the magnetic poles move! In the first part of the 20th century, the poles usually moved about 9 km (5.6 miles) per year. Then, around 1970, they started moving faster. In recent years they have been moving about 41 km (25 miles) per year!

Sometimes Earth's magnetic field even flips over! The North and South Magnetic Poles trade places. This doesn't happen very often; usually at least a few hundred thousand years pass between these flips.

Speaking of flipping, did you know that Earth's North Magnetic Pole is actually a south pole? Huh, what? When compasses were first invented, people noticed that one end of the compass pointed towards the North. They called the end of the compass needle that pointed North the "north end" of the needle (makes sense!). Later, people learned more about magnets. They learned that like ends (a north and a north OR a south and a south) push away from each other. They learned that opposite ends (such as a north and a south) pull toward each other. The needle of a compass is a tiny bar magnet. The north end of the needle is pulled toward Earth's North Magnetic Pole. So the North Magnetic Pole is actually the south pole of Earth's magnetic field. Doesn't that just make your brain ache!

The aurora (Northern and Southern Lights) mostly happen near the magnetic poles. That's because the charged particles (mostly electrons and protons) that cause the aurora follow along magnetic field lines towards the magnetic poles. When the particles run into air in Earth's atmosphere, the air glows in pretty colors - making the beautiful aurora!

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Properties of Magnets and Magnetic Fields - Mind Map

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Ferromagetism - Diamagmetism - Paramagnetism

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Ferromagetism - Diamagmetism - Paramagnetism

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Lectures by Walter Lewin. They will make you ♥ Physics.

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This channel contains the complete 8.01x (Physics I: Classical Mechanics), 8.02x (Physics II: Electricity and Magnetism) and 8.03 (Physics III: Vibrations an...