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ISTP News May 2000
Aurora Over the North Pole of Earth
NASA's Polar spacecraft took this series of images of the aurora over Earth's northern hemisphere. The images were collected by Polar's Visible Imaging System in February 2000, and they reveal the auroral oval around the polar regions in visible and ultraviolet light. The most intense auroral activity -- typically provoked by magnetic reconnection events in Earth's tail -- appears in bright red or white.
Credit: University of Iowa/NASA Scientific Visualization Studio
The Shape of Earth's Magnetosphere
This animation depicts how Earth's magnetosphere is stretched from a simple, symmetrical dipole field into a windsock- or jellyfish-shaped body. We start with a simple bar magnet, surrounded by iron filings that trace the invisible magnetic field lines of force. Like a bar magnet, Earth has a dipole magnetic field -- that is, a north and south magnetic pole (not to be confused with the geographic poles). If there were no solar wind, Earth's magnetosphere would make a near-perfect dipole. But as we see at the end of the animation, when the magnetized solar wind blows past the Earth, it compresses the day (or sunlit) side of Earth's field and stretches out the night side into a long tail.
Credit: Angela Cheyunski/Honeywell Max-Q Digital Group for NASA
Global View of Magnetic Reconnection
This animation depicts how the magnetic field of the Sun -- carried by the solar wind -- can be deflected by or attached to Earth's magnetosphere (yellow lines). As the animation begins, we see arrows moving around the Earth's magnetosphere, showing how it is naturally oriented to the north -- the field flows out of the south pole and into the north. When the solar wind is oriented to the north (red line, with arrows also pointing up), the solar wind and magnetosphere fields cannot connect, essentially repelling each other. The solar wind flows around the magnetosphere. But when the solar wind is oriented with a southward magnetic field (red line, with arrows also pointing down), it connects to the Earth's northward field (making orange field lines). This magnetic reconnection pulls field lines from the day side of Earth around to the night side, and allows electrified gas (plasma) to pour into the tail of the magnetosphere. As the field lines pile up on the night side, the system becomes unstable. Reconnection happens again -- this time in the middle of the tail. Particles and energy are shot down toward Earth's poles to make auroras, while a blob of plasma pinches off of the tail and flows downwind of Earth.
Credit: Angela Cheyunski/Honeywell Max-Q Digital Group for NASA
Data Visualization of Reconnection Based on real science observations from Polar, this web-based movie shows how magnetic field lines and particles from the Sun (red) march toward and reconnect with field lines and particles from the magnetosphere. Red dots depict electrons from the Sun, while green dots represnt protons (hydrogen ions) from the Sun. Blue dots are electrons naturally trapped in Earth's magnetosphere, and orange dots are trapped protons. Notice how after the field lines connect at the X in the middle, the new lines move off at right angles, and the electrons and protons from the Sun and Earth start to mingle.
Credit: University of Iowa/HYDRA Science Team
Closeup of reconnecting magnetic fields
This cartoon shows how magnetic field lines traveling in opposite directions (red and yellow lines, representing opposite polarities) can pinch together and reconnect to each other. The newly connected field lines move off at right angles from their orginal orientation, carrying bursts of magnetic energy and particles with them.
Credit: Angela Cheyunski/Honeywell Max-Q Digital Group for NASA
Reconnection affects activity in Earth's ionosphere 
As we look down on the north pole of Earth, the black pointers show the direction and speed of winds in the ionosphere. These electrified winds swirl at altitudes of 100-200 miles and speeds between 1000 to 2000 miles per hour. At the bottom of the screen, you see a two plots of the direction and intensity of the interplanetary magnetic field (IMF) carried by the solar wind. As the field switches from north to south, the wind patterns change -- showing the response of our atmosphere to reconnection events happening much further out in space. The red dots on the globe mark the locations of the magnetometers from which data are gathered. 
Credit: Boston University/MAACS Project

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