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SPRG Seminars - Archive
April 11, 2006
Particle acceleration at termination shock
Gang Li, UC Berkeley / Space Sciences Laboratory
Before the supersonic solar wind merges with interstellar medium, it slows down through the termination shock (TS) to become subsonic. The termination shock, which surrounds the entire solar system, is estimated to be around 100 AU and it has been long thought that the anomalous component of cosmic rays (ACR's) are accelerated to ~ 100 MeV/nuc at the termination shock.
On December 17th, 2004, Voyager I crossed the termination shock and entered the inner heliosheath, thus verified those earlier predictions of its existence.
However, contrary to all prior theoretical models, Voyager I did not observe the source of ACR's at the termination shock. The expected fully unfolded spectrum was not found. Instead, the spectrum kept unfolding after crossing the termination shock.
Why did not we see the ACR's at the TS? Can the well-acclaimed diffusive shock acceleration mechanism account for the observation? What will Voyager II see in the near future at its crossing of TS?
These will be discussed in my talk.