Dropping to a fraction of its normal density and to half its normal speed, the solar wind died down enough to allow physicists to observe particles flowing directly from the Sun’s corona to Earth. This severe change in the solar wind also changed the shape of Earth’s magnetic field and produced an unusual auroral display at the North Pole.
Starting late on May 10 and continuing through the early hours of May 12, NASA’s ACE and Wind spacecraft each observed that the density of the solar wind dropped by more than 98%. Because of the decrease, energetic electrons from the Sun were able to flow to Earth in narrow beams, known as the strahl. Under normal conditions, electrons from the Sun are diluted, mixed, and redirected in interplanetary space and by Earth’s magnetic field (the magnetosphere). But in May 1999, several satellites detected electrons arriving at Earth with properties similar to those of electrons in the Sun’s corona, suggesting that they were a direct sample of particles from the Sun.
“This event provides a window to see the Sun’s corona directly,” said Dr. Keith Ogilvie, project scientist for NASA’s Wind spacecraft and a space physicist at NASA’s Goddard Space Flight Center, Greenbelt, MD. “The beams from the corona do not get broken up or scattered as they do under normal circumstances, and the temperature of the electrons is very similar to their original state on the Sun.”
From (via digg)
