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A Public Outreach Module:
Solar Wind, Genesis, and the Planets

Genesis collector is outside the Earth's magnetosphere

The interaction of the Earth’s magnetic field with the solar wind made it necessary to position the Genesis collector outside the Earth’s magnetosphere to obtain a “clean“ sample of the solar wind, one in which there has been no interaction between the solar wind and our strong magnetosphere. But this placement in space also makes the spacecraft subject to solar energetic particles (SEPs), produced when explosive events occur on the sun.

When flares, prominences, and coronal mass ejections (CMEs) occur on the sun, the flux of x-rays may increase several orders of magnitude, and the energy of this radiation increases. Electrons and protons may be ejected in large numbers, and in rare events some particles may be accelerated to very high energy. It is these solar energetic particles (SEP's), produced during Solar Max by the energetic environs of solar flares, that can cause damage to a spacecraft. These particles travel at nearly the speed of light and have enough energy to travel through the walls of spacecraft components. On Genesis they produce spurious "star" signals or even a "fog" of light in the star tracker, causing the spacecraft to temporarily lose its orientation.

The Genesis Electron Monitor (GEM ) sensors are also relatively sensitive to high energy particles. These particles go right through the instrument walls and hit the detector, causing a high background. This high background can be seen as a red featureless portion of the electron plots, for example, at times during August 18-20, as well as other times, in the online data. These energetic particle events caused the Genesis spacecraft to go into safe mode twice during the fall of 2001, when these events were most frequent and intense.

Find out: Do other planets have protective atmospheres?


For a more technical description, take a Closer Look at
The Structured Sun and Solar Max: At the Core of the Matter

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Curator: Aimee Meyer
Updated: November 2009

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