Voyager 1 Animation
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In August 2002, the APL-built Low-Energy Charged Particle instrument on Voyager 1 began encountering higher-than-normal levels of charged particles (shown by the yellow line), indicating the spacecraft had penetrated the heliosheath. After experiencing high flux levels for more than six months, within a couple of hours the flux suddenly returned to pre-August levels. As this animation shows, the termination shock is not a fixed line, but a boundary that may change in relation to the degree of the Sun's influence. The instrument science team's current theories predict a shift in the termination shock. (2.07 MB).
The LECP instrument on Voyager 1 scans 360 degrees — in 45-degree increments — to measure the composition, charge and direction of space particles. Before reaching the termination shock, the LECP instrument detected most of these particles were flowing away from the Sun. However, once in the heliosheath (beyond the shock), the particles flowed toward the spacecraft from all directions. In that same region, the LECP instrument saw dramatically fewer carbon ions and more of the lighter ions such as oxygen, helium and hydrogen. (2.02 MB).