Co-rotating Interactive Regions (CIRs) are regions within the solar wind
where streams of material moving at different speeds collide and interact with each other.
The speed of the solar wind varies from less than 300 km/s (about half a million miles per
hour) to over 800 km/s depending upon the conditions in the corona where the solar wind
has its source. Low speed winds come from the regions above helmet streamers while high speed winds come from
coronal holes. As the Sun rotates these various
streams rotate as well (co-rotation) and produce a pattern in the solar wind much like
that of a rotating lawn sprinkler. However, if a slow moving stream is followed by a fast
moving stream the faster moving material will catch-up to the slower material and plow
into it. This interaction produces shock waves that can accelerate particles to very high
The chemical composition of the solar wind has several interesting aspects
that hint at physical processes that occur in the solar wind source regions. The solar wind
composition is different from the composition of the solar surface and shows variations
that are associated with solar activity and solar features.
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