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HERE ARE SOME MORE fantastic short videos of Earth at night, taken by cameras aboard the International Space Station. Visible in many of them are the aurora and lightning below. Enjoy!

Adapted from information issued by NASA.

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Solar storm reaches Earth

Illustration of space weather

Artist's illustration of events on the Sun changing the conditions in Near-Earth space

THIS WEEK SAW A HUGE solar disturbance that sent a storm of energy on a collision course with our planet.

The Sun erupted with one of the largest solar flares of this solar cycle on March 6. The flare was categorised as an X5.4, making it the second largest flare—after an X6.9 on August 9, 2011—since the Sun’s activity moved into a period of relatively low activity called solar minimum in early 2007. The current increase in the number of X-class flares is part of the Sun’s normal 11-year solar cycle, during which activity ramps up to solar maximum, which is expected to peak in late 2013.

About an hour later, the same region let loose an X1.3 class flare. An X1 is 5 times smaller than an X5 flare.

Space weather starts at the Sun. It begins with an eruption such as a huge burst of light and radiation called a solar flare or a gigantic cloud of solar material called a coronal mass ejection (CME). But the effects of those eruptions are felt at Earth, or at least near-Earth space. Scientists monitor several kinds of “space weather” events—geomagnetic storms, solar radiation storms, and radio blackouts—all caused by these immense explosions on the Sun.

Geomagnetic storms

One of the most common forms of space weather, a geomagnetic storm refers to any time Earth’s magnetic environment, the magnetosphere, undergoes sudden and repeated change. This is a time when magnetic fields continually re-align and energy dances quickly from one area to another.

Geomagnetic storms occur when certain types of CMEs connect up with the outside of the magnetosphere for an extended period of time. The solar material in a CME travels with its own set of magnetic fields. If the fields point northward, they align with the magnetosphere’s own fields and the energy and particles simply slide around Earth, causing little change. But if the magnetic fields point southward, in the opposite direction of Earth’s fields, the effects can be dramatic. The Sun’s magnetic fields peel back the outermost layers of Earth’s fields changing the whole shape of the magnetosphere. This is the initial phase of a geomagnetic storm.

The next phase, the main phase, can last hours to days, as charged particles sweeping into the magnetosphere accumulate more energy and more speed. These particles penetrate closer and closer to the planet. During this phase viewers on Earth may see bright aurora at lower latitudes than usual. The increase—and lower altitude—of radiation can also damage satellites travelling around Earth.

The final stage of a geomagnetic storm lasts a few days as the magnetosphere returns to its original state.

The movie below shows the March 6, 2012 X5.4 flare, captured by the Solar Dynamics Observatory (SDO) spacecraft. One of the most dramatic features is the way the entire surface of the Sun seems to ripple with the force of the eruption. This movement comes from something called EIT waves—because they were first discovered with the Extreme ultraviolet Imaging Telescope (EIT) on the Solar Heliospheric Observatory (SOHO).

Since SDO captures images every 12 seconds, it has been able to map the full evolution of these waves and confirm that they can travel across the full breadth of the Sun. The waves move at over a million miles per hour, zipping from one side of the Sun to the other in about an hour. The movie shows two distinct waves. The first seems to spread in all directions; the second is narrower, moving toward the southeast. Such waves are associated with, and perhaps trigger, fast coronal mass ejections, so it is likely that each one is connected to one of the two CMEs that erupted on March 6.

Geomagnetic storms do not always require a CME. Mild storms can also be caused by something called a co-rotating interaction region (CIR). These intense magnetic regions form when high-speed solar winds overtake slower ones, thus creating complicated patterns of fluctuating magnetic fields. These, too, can interact with the edges of Earth’s magnetosphere and create weak to moderate geomagnetic storms.

Geomagnetic storms are measured by ground-based instruments that observe how much the horizontal component of Earth’s magnetic field varies. Based on this measurement, the storms are categorized from G1 (minor) to G5 (extreme). In the most extreme cases transformers in power grids may be damaged, spacecraft operation and satellite tracking can be hindered, high frequency radio propagation and satellite navigation systems can be blocked, and auroras may appear much further south than normal.

Solar radiation storms

A solar radiation storm, which is also sometimes called a solar energetic particle (SEP) event, is much what it sounds like: an intense inflow of radiation from the Sun. Both CMEs and solar flares can carry such radiation, made up of protons and other charged particles. The radiation is blocked by the magnetosphere and atmosphere, so cannot reach humans on Earth. Such a storm could, however, harm humans travelling from Earth to the Moon or Mars, though it has little to no effect on airplane passengers or astronauts within Earth’s magnetosphere. Solar radiation storms can also disturb the regions through which high frequency radio communications travel. Therefore, during a solar radiation storm, airplanes travelling routes near the poles—which cannot use GPS, but rely exclusively on radio communications—may be re-routed.

Photo of an aurora

Aurorae occur primarily near Earth's poles. They are the most common and the only visual result of space weather. This aurora image associated with solar flares and CMEs on February 23-24, 2012 was taken over Muonio, Finland before sunrise on February 27, 2012.

Solar radiation storms are rated on a scale from S1 (minor) to S5 (extreme), determined by how many very energetic, fast solar particles move through a given space in the atmosphere. At their most extreme, solar radiation storms can cause complete high frequency radio blackouts, damage to electronics, memory and imaging systems on satellites, and radiation poisoning to astronauts outside of Earth’s magnetosphere.

Radio blackouts

Radio blackouts occur when the strong, sudden burst of X-rays from a solar flare hits Earth’s atmosphere, jamming both high and low frequency radio signals. The X-rays disturb a layer of Earth’s atmosphere known as the ionosphere, through which radio waves travel. The constant changes in the ionosphere change the paths of the radio waves as they move, thus degrading the information they carry. This affects both high and low frequency radio waves alike. The loss of low frequency radio communication causes GPS measurements to be off by feet to miles, and can also affect the applications that govern satellite positioning.

Radio blackouts are rated on a scale from R1 (minor) to R5 (extreme). The strongest radio blackouts can result in no radio communication and faulty GPS for hours at a time.

More information: Space Weather Frequently Asked Questions

Adapted from information issued by NASA. Images courtesy NASA and Thomas Kast. Video courtesy NASA / GSFC / SDO.

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Northern Lights put on a show

THE NORTHERN LIGHTS have been in the news lately, with some impressive displays reported this week. Here’s a plain-language Q&A on the Lights and when and where they can be seen.

Also called the “aurora borealis”, the Northern Lights are big patches of glowing air molecules high up in our atmosphere. The Southern Hemisphere equivalent is the “aurora australis” or Southern Lights.

To see the Northern Lights you have to be located in far northern latitudes, eg. UK, Scandinavia, northern Europe. Likewise, to see the Southern Lights you have to be located in far southern latitudes, eg. Tasmania, New Zealand and the tip of South America. The best view of the Southern Lights is to be had in Antarctica.

The Northern Lights get their name from the Roman goddess of dawn, Aurora, and the Greek name for the north wind, Boreas.

The video above shows what the aurora looks like from space.

What causes them?

They’re caused by an interaction between particles from the Sun, Earth’s magnetic field and Earth’s atmosphere.

The Sun sends out waves of electrically charged particles, sometimes in big clumps. Those particles get caught in Earth’s magnetic field and are funnelled downward from space and toward our north and south poles.

When they hit the molecules in our upper atmosphere, those molecules give off light—a bit like a giant fluorescent tube in the sky.

They occur very high up, in the upper layer of Earth’s atmosphere called the “thermosphere”—essentially, right on the edge of space

The different colours are caused by the different molecules in the air: oxygen produces a green or brownish glow, nitrogen produces a red or blue glow. The glows from oxygen and nitrogen can combine to produce a pink glow.

Here’s a very good video that explains how the aurora is produced:

Can we see them from Australia?

Yes, but you have be far south and away from city lights. During the time of solar maximum (see below), they’re often seen from Tasmania, southern Victoria and southern Western Australia. In the past, I’ve even heard reports of sightings from the Blue Mountains west of Sydney.

Because the Southern Lights occur down near Antarctica, from Australian latitudes they will be seen way down toward our southern horizon (if at all).

I understand that the next 12 months should be good to see them?

Yes. The Sun has an 11-year cycle of activity, and we’re coming up to “solar maximum” sometime in the next 12-18 months. So we can expect many more auroral reports.

Apart from a pretty light show, do they have any other effects on us?

The aurorae themselves don’t have any other effect, but the space weather that causes them can.

Those charged particles from the Sun, and the effect the solar wind can have on Earth’s magnetic field, can cause:

  • Damage or disruption to satellites, eg. GPS, communications, weather, military
  • Disruption to radio communications networks
  • Damage or disruption to electricity grids (due to currents induced into the grid by the changing magnetic field)
  • Damage or disruption to long pipeline systems (ditto)
  • Disruption to mineral exploration (which often relies on magnetic field information)

More information:

Space Weather.com

Aurora Watch

Aurora Alert

Aurora Forecast

Space Weather Prediction Centre

Ionospheric Prediction Service (Australian Government)

Story by Jonathan Nally.

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Exoplanets have unearthly light shows

Artist's concept of a 'hot Jupiter' planet

Artist's concept of a 'hot Jupiter' planet with two moons and a Sun-like star. The planet is cloaked in brilliant aurorae—100-1000 times brighter than Earth's—triggered by stellar storms.

BEINGS LIVING ON ‘HOT JUPITER’ PLANETS could be treated to a dazzling nightly light show a thousand times better than Earth’s Northern and Southern Lights.

Earth’s aurorae provide a dazzling light show to people living in the polar regions, with shimmering curtains of green and red undulating across the sky like a living creature.

But new research shows that aurorae on ‘hot Jupiter’ planets closely orbiting distant stars could be 100-1000 times brighter than Earthly aurorae. They also would ripple from equator to poles (due to the planet’s proximity to any stellar eruptions), treating the entire planet to an otherworldly spectacle.

“I’d love to get a reservation on a tour to see these aurorae!” said lead author Ofer Cohen, a SHINE-NSF postdoctoral fellow at the Harvard-Smithsonian Centre for Astrophysics (CfA).

Gigantic stellar blasts

Earth’s aurorae are created when energetic particles from the Sun slam into our planet’s magnetic field. The field guides the particles toward the poles, where they smash into Earth’s atmosphere, causing air molecules to glow like a neon sign.

The same process can occur on planets orbiting distant stars, known as exoplanets.

Aurora Australis seen from the International Space Station

The Southern Lights or Aurora Australis seen from the International Space Station on July 14, 2011.

Particularly strong aurorae result when Earth is hit by a coronal mass ejection or CME—a gigantic blast that sends billions of tonnes of solar plasma (electrically charged, hot gas) into the Solar System.

A CME can disrupt Earth’s magnetosphere—the bubble of space protected by Earth’s magnetic field—causing a geomagnetic storm. In 1989, a CME hit Earth with such force that the resulting geomagnetic storm blacked out huge regions of Quebec.

Planets in the firing line

Cohen and his colleagues used computer models to study what would happen if a gas giant planet in a close orbit, just a few million kilometres from its star, were hit by a stellar eruption.

He wanted to learn the effect on the exoplanet’s atmosphere and surrounding magnetosphere.

The alien gas giant would be subjected to extreme forces. In our Solar System, a CME spreads out as it travels through space, so it’s more diffuse once it reaches us.

Aurora planet animation

In this animation, stunning aurorae (pink/purple) ripple around a 'hot Jupiter' planet.

A ‘hot Jupiter’ would feel a stronger and more focused blast, like the difference between being 100 kilometres from an erupting volcano or one kilometre away.

“The impact to the exoplanet would be completely different than what we see in our Solar System, and much more violent,” said co-author Vinay Kashyap of CfA.

Yet despite the extreme forces involved, the exoplanet’s magnetic field would shield its atmosphere from erosion.

Too close for comfort

This work has important implications for the habitability of rocky worlds orbiting distant stars. Since red dwarf stars are the most common stars in our galaxy, astronomers have suggested focusing on them in the search for Earth-like worlds.

However since a red dwarf is cooler than our Sun, a rocky planet would have to orbit very close to the star to be warm enough for water to exist as a liquid. There, it would be subjected to the sort of violent stellar eruptions Cohen and his colleagues studied.

Their future work will examine whether rocky worlds could shield themselves from such eruptions.

Adapted from information issued by the Harvard-Smithsonian Centre for Astrophysics. Images courtesy David A. Aguilar (CfA). Animation produced by Hyperspective Studios.

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Amazing aurora videos