Tag: magnetic field

Unfurled aurora

By Phil Plait | October 29, 2012 7:00 am

Every time I think I’ve posted just the most sensational aurora picture I’ve seen, another one comes along that has me scraping my jaw off the floor. Check out this shot by photographer David Cartier:

[Seriously, click to enbirkelandate.]

I know, right? That spiral shape is fascinating. Aurorae are formed when charged particles from the Sun slam into the Earth’s magnetic field and interact with it. They’re channeled down into our atmosphere, guided by the Earth’s field, and the shape of the aurora reflects the underlying magnetic field lines. They take on fantastic shapes, including spirals like this, but I don’t think I’ve ever seen curled in a way so well-defined and crisp.

If you look carefully at the bigger version, you’ll see some familiar stars like those forming the constellation Auriga in the center, while the Pleiades are visible nestled in the spot right where the aurora starts to wind up. The bright "star" which is also reflected in the water is actually Jupiter. I had a hard time distinguishing it from the bright star Aldebaran in Taurus, but I think that’s lost in the brightest part of the spiral (though you can see it better in the water to the right of the stretched-out Jupiter reflection).

David lives in the Yukon Territory, not far from the southeast corner of Alaska, and I imagine aurorae are a fact of life there. He has quite a few devastating shots of the northern lights in his Flickr stream. Treat yourself and take a look. His shots of atmospheric phenomena are also incredible.

Related Posts:

Aurora, in the pink (explaining aurora colors, and this followup)
The rocket, the laser, and the northern lights (still one of the best aurora pix ever)
Shimmering purple aurora after a powerful solar storm
Up, up, and aurora!

CATEGORIZED UNDER: Cool stuff, Pretty pictures

The song of killer electrons

By Phil Plait | October 1, 2012 12:15 pm

Light and sound are two fairly different things. They’re both waves, but their similarity ends there. Sound is a compression wave: something happens (like a tree falling in a forest) that compresses air a little bit, and that wave travels outward at – shockingly – the speed of sound. Your ears detect it, and your brain translates it into sound.

Light is an electromagnetic wave. The whole story is fairly complicated, but it’s an oscillation of electric and magnetic fields, and doesn’t need a medium (like air or water) through which to travel.

But because they’re both waves, light and sound have a frequency and an amplitude. If you’re clever – and we humans are – you can convert one to the other… well, more like translate one to the other. It’s not like it’s a real conversion, with physical meaning (like converting feet to meters). But it can make for an interesting, and lovely, experience.

In August 2012, NASA launched a pair of satellites called Radiation Belt Storm Probes. They are designed to detect the electromagnetic radiation (also called EM for short) emitted as charged particles bip and bop around Earth’s magnetic field, high above the surface. Various phenomena in the geomagnetic field produce radio waves – which are a form of light, but too low energy for our eyes to detect. These waves can have the same frequency as sound waves we can hear – a few Hertz, or oscillations per second – so they can be directly translated into sound. Scientists did that using RBSP data, and it sounds eerie and beautiful.

Here’s the sound file of these waves. It’s… odd. Like birdsong, but unearthly. You can understand why scientists call these waves "chorus".

And they’re handy, too. Translating light to sound in this way can be helpful in understanding it, much like creating color pictures helps astronomers understand data better. The folks at NASA put together this video to explain all this:

This is actually pretty important stuff. Electrons blown from the Sun in the solar wind get trapped in Earth’s magnetic field, like bugs in a net. Usually these are low energy particles, which eventually follow the magnetic field lines to the Earths poles, where they are deposited safely into our atmosphere. But sometimes, something caffeinates these electrons, pumping them up to very high energies. They travel so quickly that if they hit one of our satellites, they can damage the electronics! The reasons benign particles can turn into "killer electrons" isn’t well understood, but it may have to do with these chorus waves. Understanding them better means we can protect our satellites better, and since we spend trillions of dollars on satellites, there’s some decent motivation to make sure they work well.

Also? It’s just cool. If you like the killer electron song, then you’ll get a kick out of other sounds created the same way, from the aurora to meteors burning up in our atmosphere! You’ll find links to those listed in Related Posts below.

Image of my good friend Dr. Nicole Gugliucci, aka Noisy Astronomer, used totally without her permission. Won’t she be surprised?

Related Posts:

Hear the Sun’s roar
Listen in on the Perseid meteor shower
Saturn, the Forbidden Planet
Phoenix sings
Laying down the pulsar beat

Desktop Project Part 21: Dancing in the dark filaments

By Phil Plait | April 15, 2012 7:00 am

[My Desktop Project — clearing off the cool astropix from my computer’s desktop by posting one each day — is getting close to being done soon; I’m down to my last few pictures!]

It’s funny how different the Sun looks at different wavelengths of light. In visible light, you can see all sorts of surface features like sunspots, granules (rising and falling packets of gas convecting like a pot of water on a stovetop), and more.

But when you have eyes sensitive to the ultraviolet, the Sun takes on an entirely new appearance. That’s where the effects of the Sun’s active and crazy magnetic field claim dominion, and you see vast arcs, loops, and towers of incredibly hot plasma. To be fair, you can see this in visible light too, but it’s not quite so… dynamic. Cue NASA’s Solar Dynamics Observatory, and its UV detectors:

This image was taken by SDO on March 28, 2012, and shows the limb of the Sun at a wavelength of 19.3 nanometers — well into the UV. What you’re seeing is plasma — gas so energetic it’s had electrons ripped right off its atoms, putting it under the sway of the Sun’s fierce magnetism. The plasma flows along the magnetic field lines, arcing high off the surface into space before coming back down.

Usually, those arcs are hot and bright, like the tight loops you can see on the left (within hours, those loops got bigger and brighter, making dozens of well-defined glowing coils). But you can also see a dark arc in the center, going from just below the center of this picture, curving to the upper left, then heading up and over to the right, off the face of the Sun. For some reason, the plasma there wasn’t quite as hot, and so instead of glowing at this wavelength it appears dark, absorbing the light from material behind it.

I took this shot using Helioviewer.org — if you click the picture it will take you there. You can then play with the controls on the left and watch this dark filament change, grow, dance, and playfully flow from one arc base to the other. It’s mesmerizing. SDO has a page with some pre-made animations, too.

I love how we see the Sun pretty much every day, but in many ways it is as unfamiliar as any distant star. Happily, though, our drive to explore and understand has led us to the point where we can investigate our nearest star, and learn more about it. Given that it’s the main driver of life on Earth, this is probably a smart idea.

Image credit: NASA/SDO/Helioviewer.org

Related Posts:

Desktop Project Part 8: From filament to prominence
The Sun’s angry red spot
HUGE sunspots turning toward Earth
The comet and the Coronal Mass Ejection

CATEGORIZED UNDER: Astronomy, Pretty pictures

Mesmerizing, towering loops of solar magnetism

By Phil Plait | January 29, 2012 7:02 am

I know I’ve been writing about the Sun quite a bit lately, but I have a followup to yesterday’s cool video of the big solar flare… and you’re gonna like it.

I was fooling around with helioviewer.org, watching the flare in different wavelengths of light detected by NASA’s Solar Dynamics observatory, when I switched to 17.1 nanometers — in the far ultraviolet. At that wavelength, the glowing plasma that flows along the Sun’s magnetic field lines is very bright. The images were so beautiful, so incredible, I made a video animation of them, covering the time range of January 26, 2012 at midnight to January 28 at noon (UTC), which includes the huge X2 solar flare that erupted on the 27th. The video shows huge loops of magnetism on the Sun’s surface, glowing plasma flowing along them… and then 48 seconds in the flare changes everything. Watch:

Holy wow! Isn’t that awesome? Make sure you watch in in HD, and make it full screen to get the whole effect.

What you’re seeing is Active Region 1402, a sunspot cluster. This is a tangled collection of magnetic field lines piercing the surface of the Sun. Like a bar magnet, there are two poles to each loop, a north and a south pole. The gas on the surface of the Sun is so hot it has electrons stripped off, so it’s strongly affected by the intense magnetic field, and flows along these towering loops, which can reach heights of 300,000 km (180,000 miles) in this region.

The loops are tied to the plasma, too, and this material is twisting and roiling as it rises and sinks. The lines get tangled, and like a short circuit they can snap and reconnect. When they do, they release vast amounts of energy as a solar flare. In the video you can see the messy, disorganized loops getting more and more tangled up. Then KABLAM! The flare itself is not visible because it happened too quickly to be seen on this timescale (see the video yesterday for that). But you can see the effect on the magnetic field loops! They suddenly become far more organized, tight, and calm.

The Sun is fiendishly complex, and astonishingly beautiful. Clearly, to our brains, these things are connected. Remember, too: this beauty, this magnificence, is brought to you by science. Without our curiosity and our need to understand the Universe better, you would never have been able to watch in awe as superheated plasma arcs dwarfing the Earth itself grew and collapsed on the surface of a star one hundred fifty million kilometers away.

Think of that the next time someone says science takes away the beauty and mystery of life.

Credit: NASA/SDO/Helioviewer.org

Related posts:

The Sun’s still blasting out flares… BIG ones
The Sun aims a storm right at Earth: expect aurorae tonight!
Awesome X2-class solar flare caught by SDO
Gorgeous flowing plasma fountain erupts from the Sun

CATEGORIZED UNDER: Astronomy, Cool stuff, Pretty pictures

Gorgeous flowing plasma fountain erupts from the Sun

By Phil Plait | October 10, 2011 7:00 am

On September 24th, Active Region 1302 — a cluster of enormous sunspots — popped off an X-class flare, a powerful event that caused some beautiful aurorae here on Earth.

But the flares don’t have to be so powerful to generate ethereal, magnificent beauty. A day after that biggish event, those sunspots burped again, this time with a lower-power M-class flare. Now, when I say "low power", it’s not like a firecracker or a car backfiring: the total energy released would still dwarf the combined nuclear might of every country on Earth! By a lot. But for the Sun, that’s considered to be "meh".

Still, if you get a good view of it, well, it’s still gorgeous. The Solar Dynamics Observatory, orbiting the Earth, has what is essentially a box seat to the Sun, and got this footage of the flare:

[Make sure to set it to at least 720p and make it full screen!]

The flare and prominence — the arcing tower of material — lasted about three hours, and this video shows it at a rate of one frame every minute of real time. Read More

CATEGORIZED UNDER: Astronomy, Cool stuff, Pretty pictures

Uranus got double-tapped?

By Phil Plait | October 7, 2011 9:37 am

One of the enduring mysteries of our solar system is why Uranus is tilted over on its side. If you measure the angle of a planet’s rotation axis (the location of its north pole) compared to the plane of its orbit, you find that all the planets in the solar system are tipped. Jupiter is only 3°, but Earth is at a healthy 23° angle; Mars is too. Venus is tipped so far over it’s essentially upside-down (we know this because it spins the wrong way).

Uranus, weirdly, is at 98°, like it’s rolling around the outer solar system on its side. The best guess is that it got hit hard by something planet-sized long ago, knocking it over (though there are other, more speculative, ideas). The problem with that is that its moons and rings all orbit around its equator, meaning their orbital planes are tipped as well. It’s hard to see how that might have happened, even if you assume the moons formed in that collision (as, apparently, our Moon formed in an ancient grazing impact with Earth by a Mars-sized body).

Well, a team of astronomers have come up with a new idea: maybe Uranus wasn’t hit by one big object. Maybe it was hit by two smaller ones.

Read More


A fiery angel erupts from the Sun

By Phil Plait | July 28, 2011 12:27 pm

When you build and launch a high-resolution solar observatory that stares at the Sun 24 hours a day, you’re bound to catch some pretty cool stuff. As proof, check out this video of a stunning prominence erupting from the Sun’s surface on July 12, 2011, as seen by NASA’s Solar Dynamics Observatory:

[Make sure you set the resolution to at least 720p.]

That’s really graceful, especially considering that tower reached the staggering height of about 150,000 km (90,000 miles) above the Sun in just a few minutes!

The gas on the Sun is ionized, which means it’s had one or more electrons ripped away from its atoms. Technically called a plasma, this makes it sensitive to the Sun’s strong magnetic forces. That becomes really obvious after it starts to collapse; it doesn’t follow a ballistic trajectory like you’d expect (the path a ball thrown up in the air would follow), but instead flows along the Sun’s magnetic field lines. This video is in the ultraviolet, where such a plasma glows brightly.

For a moment there, just at its peak, it coincidentally looks like a classic angel with wings spread. Of course, once the angel dissolves it forms more of an arc… so I guess this makes it an archangel. I’m glad no one heard a trumpet playing when this happened. That could’ve been awkward.

Credit: NASA/SDO

Related posts:

The Sun lets loose a HUGE explosion
Followup: Sunspot group’s loopy magnetism
Incredible solar flare video
kaBLAM! Footage of the X-class flare


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