NASA: Cracks in Earth's Magnetic Field Stay Open to Let in Solar Wind

Solar wind emanates from the sun to Earth's magnetic field. [NASA Image]

NEWINGTON, CT, Dec 16, 2003--NASA says it appears that immense cracks in Earth's magnetic field remain open for hours, allowing the solar wind to gush through and power stormy space weather. The space agency is basing that conclusion on observations from its IMAGE (Imager for Magnetopause to Aurora Global Exploration ) spacecraft and the joint NASA/European Space Agency (ESA) Cluster satellites. Scientists have known about the cracks for some time but didn't know until recently that they can remain open for long periods. The phenomenon can affect radio propagation.

"We discovered that our magnetic shield is drafty, like a house with a window stuck open during a storm," said Harald Frey of the University of California-Berkeley, the lead author of a paper on this topic published December 4 in Nature. "The house deflects most of the storm, but the couch is ruined. Similarly, our magnetic shield takes the brunt of space storms, but some energy continually slips through its cracks, sometimes enough to cause problems with satellites, radio communication and power systems."

Where the solar wind's magnetic polarity is opposite that of Earth's magnetic field, some electrically charged particles of the solar wind enter Earth's magnetosphere (represented by red lines) through a crack (represented by the white flash) formed during the interconnection of the sun and Earth's magnetic field lines. [NASA Image]

Data from NASA's IMAGE spacecraft show a spot the ultraviolet proton aurora (blue ring) created as solar material falls through crack in magnetosphere onto Earth's ionosphere. [NASA Image]

Co-author of the Nature paper Tai Phan, also of UC Berkeley, says scientists can incorporate their new knowledge into space weather-forecasting computer models to more accurately predict how violent solar events influence space weather.

The solar wind, a stream of electrons and ions that blow constantly, transfers energy from the sun to Earth through the magnetic fields it carries and its high speed--hundreds of miles per second. NASA says the solar wind can get gusty during violent solar events such as coronal mass ejections (CMEs), or solar flares, which can shoot a billion tons of electrified gas into space at millions of miles per hour.

Earth's magnetic field extends into space for tens of thousands of miles and forms a protective barrier to the particles and snarled magnetic fields of a solar flare. Scientists learned in the 1970s that the magnetic field was not impenetrable.

In more recent observations, IMAGE revealed an area almost the size of California in the ionosphere above the Arctic, where a 75 MW "proton" aurora flared for hours. Ions striking the upper atmosphere caused it to emit ultraviolet light, which IMAGE can see but humans cannot. While IMAGE recorded the UV aurora, the four-satellite Cluster constellation flew directly through the crack and detected solar wind ions streaming through in precisely the same region as the proton aurora.

There's more information, images and animations on NASA's Goddard Space Flight Center Web site.--NASA

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