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What makes the northern lights dance discovered

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  • George Lessard
    [image: canada, canadian search engine, free email, canada news] Friday » July 25 » 2008
    Message 1 of 1 , Jul 25, 2008
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      Friday » July
      25 » 2008

      <
      http://www.canada.com/montrealgazette/news/story.html?id=b4203bcd-0130-4569-b40f-c8ea3f7d56ca
      >

      When Earth's rubber band snaps
      Canadian and U.S. Scientists say they have discovered what makes the
      northern lights dance
      MARGARET MUNROCanwest News Service
      Friday, July 25, 2008

      [image: The northern lights dance across a starry night sky at the
      Yellowknife boat launch on Great Slave Lake in the Northwest
      Territories.]CREDIT:
      LARRY WONG, CANWEST NEWS SERVICEThe northern lights dance across a starry
      night sky at the Yellowknife boat launch on Great Slave Lake in the
      Northwest Territories.

      An international team has discovered that when Earth's magnetotail snaps out
      in space, the northern lights start dancing across Canada's skies.

      One explosive release in February - which occurred about 127,000 kilometres
      away, or one-third of the way to the moon - sent enormous amounts of energy
      hurdling toward Earth. A minute-and-a-half later, a spectacular aurora
      display lit up the skies, say the scientists, whose work with five NASA
      satellites and 20 ground stations across Canada and Alaska is
      revolutionizing our understanding of space weather.

      "We discovered what makes the northern lights dance," lead investigator
      Vassilis Angelopoulos of the University of California (Los Angeles) said in
      announcing the discovery yesterday.

      Scientists have been trying to figure out for decades what makes the aurora
      swirl and undulate through the northern and southern skies.

      The $200-million system of satellites and ground stations has, in effect,
      allowed them to "fly into the eye of the storm," said space physicist Ian
      Mann of the University of Alberta, a member of the team that has published
      its new findings online in the journal Science.

      They say explosive short-circuits, or reconnections, in Earth's magnetic
      field lines, trigger the onset of so-called "substorms" which cause the
      aurora to suddenly brighten and dance.

      Earth's magnetic field, which protects the planet from harsh solar
      radiation, absorbs energy from the solar wind, which is constantly buffeting
      the planet. The wind stretches Earth's magnetic field lines far off into
      space, producing the magnetotail, NASA scientist David Sibeck said.

      (A magnetotail is the narrow and elongated region of the magnetosphere of
      Earth that extends in the direction away from the sun.)

      But Sibeck said the magnetic field lines can only be stretched so far before
      they snap "like rubber bands."

      "You build up these big currents, you store lots of energy and then suddenly
      bang!, they snap," Sibeck told a media teleconference. Vast amounts of
      energy are then flung back toward Earth, powering up the aurora in both the
      northern and southern hemispheres.

      Such "substorms" typically occur several times a day. They vary greatly in
      intensity, with some dumping so much energy into Earth's atmosphere that
      they can damage satellites, endanger astronauts and disrupt power lines and
      communications on the ground, said the scientists, who hope their work will
      lead to better space weather forecasts.

      To try to find out what causes the spectacular light shows, NASA and its
      partners launched a flotilla of five identical satellites, the size of
      washing machines, in February 2007.

      The satellites line up on the same side of Earth once every four days and
      can pinpoint where and when substorms begin. They can also track the
      corresponding disturbances "spreading like wildfires in space," Sibeck said.

      The satellites are coupled with 20 ground stations, which have magnetometers
      and sophisticated cameras pointing skyward. They measure the currents and
      aurora swirling through the heavens during substorms.

      "We're talking about million-amp currents pumped into Earth's atmosphere,"
      Sibeck said.

      The cameras snap pictures every three seconds, enabling the scientists to
      follow aurora shows across the continent from Alaska to Newfoundland.

      The system was perfectly aligned to catch the Feb. 26 substorm.

      One satellite was on the far side of the magnetic field lines that snapped,
      or reconnected, 127,000 kilometres from Earth. The other four were closer to
      Earth and measured the resulting power surge as it raced back toward the
      planet. The ground stations caught the aurora lighting up about 11/2 minutes
      after the initial explosion, Angelopoulos said.

      "It's a quite a beautiful sequence of cause and effect," Mann said.

      "We can pinpoint where the action was right at the beginning of the boom,
      and then we can see the effect twang down toward the planet and release
      energy in the form of the northern lights over Canada and Alaska."

      It's "pretty wild" to think reconnecting magnetic field lines more than
      100,000 kilometres away can get the aurora dancing overhead, says Eric
      Donovan of the University of Calgary, who heads the Canadian component of
      the project.

      He said the finding is just "a taste of what's to come" from the mission,
      which is revolutionizing understanding of the aurora.

      "It is going to change the field of space physics forever," said Donovan,
      noting there are all kinds of strange and mysterious features in the
      northern lights. "What we don't know outnumbers what we do know."
      (c) The Gazette (Montreal) 2008


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