Archive | September 2012

New York to Rome in 2 seconds

This post is part of Citizen Science September at the Zooniverse.

Some of the fastest solar storms (coronal mass ejections or CMEs) that Solar Stormwatch volunteers measure have speeds of around 450 km/s. That’s a billion tonnes of plasma being blasted off the Sun at a million miles per hour. If it’s pointing at Earth the CME will arrive 3 days later. Not all CMEs are Earth bound though and any of the other planets in the solar system might be in the firing line.

On July 23 2012 the fastest CME recorded by STEREO blasted away from the sun at a staggering 3,400 km/s (7.6 million mph.) That’s New York to Rome in 2 seconds. This rates as Extremely Rare on NASA’s CME speed scale and we can expect one this fast to occur only once every 10 years. While CMEs might be big you won’t be able to see one if you look up. Solar spacecraft are fitted with very sensitive cameras to capture the tenuous outflow of particles. Here’s how STEREO Ahead’s Cor2 (coronograph) recorded the event.

click for video – published on YouTube 23 Jul 2012 by ve3en1

The source of the CME was sunspot Active Region 1520. An active region (AR) is an area with an especially strong magnetic field and is often associated with sunspots and solar activity. AR 1520 was very photogenic when it was on the Earth-side of the Sun earlier in July.

The Sun on 15 July 2012. AR 1520 is the feature at 5 o’clock.
(photo ©Julia Wilkinson)

Luckily AR 1520 unleashed the super-fast CME after it had rotated to the far-side and despite being an 80 degree wide CME all of the inner planets, including Earth, escaped its blast. A YouTube summary can be found here.

So what’s the big fuss about Earth-bound CMEs fast or otherwise? Well most of the time you wouldn’t even know one had hit us but just occasionally they can cause problems. If the direction of the CME’s magnetic field is southward, (opposite to the Earth’s magnetic field), the two magnetic fields interact producing a geomagnetic storm. Such storms enhance the activity in the Earth’s radiation belts which presents a radiation hazard to low-Earth orbit satellites and the ISS astronauts as they pass through the South Atlantic Anomaly. Geomagnetic storms also generate electric currents which can cause electrical surges through power lines and damage power grids. In 1989 a geomagnetic storm blacked-out most of Quebec as circuit breakers tripped on Quebec’s Hydro-electric power grid. The super-fast storm of 23 July might have missed Earth but the STEREO Ahead spacecraft took a battering from a very large proton storm associated with the CME. Proton storms can damage a spacecraft’s electronics.

This is how Solar Stormwatchers saw the CME in the STEREO Beacon mode (near real-time) feed. The effect on STEREO A is clear but it did survive to carry on its mission.

It’s pretty useful then to be able to predict the speed and direction of CMEs but there is still much to learn about what triggers them. This is where Solar Stormwatch comes in. Data from the project are being used to track and measure solar storms to learn more about how they begin and how they evolve. If you want to contribute to solar science, it’s easy, just click and join in!

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