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Click on image for full size (578K GIF) Courtesy of the Solar and Heliospheric Group

The picture here helps us analyze the CME material that passed by ACE. Put one finger near the number 4 on the picture. Put another finger on the number 16. Now everytime a white bar shows up above the number 4, that means that the CME material is cold. Everytime a white bar shows up above the number 16, that means the CME material is really hot!

So overall the movie shows us that the CME that passed ACE wasn't made up of material that is all the same temperature. This discovery could change what scientists know about CMEs and about how CMEs affect the Earth.

Click on image for full size (578K GIF) Courtesy of the Solar and Heliospheric Group

This animation shows the iron charge state distribution, which has been measured once per hour during time the CME material was passing ACE. The important thing to know here is that when a bar shows up above the Fe3+ charge state (where the number 3 would be on the x-axis between the 2 and the 4), that means the surrounding CME plasma is very cold. When a bar shows above the Fe16+ charge state (where the number 16 is on the x-axis), that means the surrounding plasma is extraordinarily hot.

So overall the movie shows us that the CME that passed ACE wasn't made up of material that is all the same temperature. Instead, it was found that the CME was made of an extremely hot region, followed by a cooler region and then another hot region of solar material. This discovery could change what scientists know about CMEs and about how CMEs affect the Earth's environment.

Click on image for full size (578K GIF) Courtesy of the Solar and Heliospheric Group

Here, we concentrate on the iron charge state distribution, which has been measured once per hour during the entire CME period. These distributions are imprints of the electron temperature distribution function within a few solar radii from the solar surface where the ejecta were accelerated. During this event the observed charge states range from the very rare Fe3+, during phases of very cold plasma, to Fe16+, when the plasma is extraordinarily hot, indicating an enormous range in electron temperatures from 10⁵ K to several 10⁶ K.

The movie shows the time history of this event: After a period of standard slow solar wind, a very hot charge state distribution arrives just after the begining of Day 122. This very hot component is followed near the end of Day 122 by one of the coldest components ever measured in situ, including what is (to our knowledge) the first observation of Fe3+ in solar wind. After about 12 hours of this cold plasma, the "hot" Fe16+ shows up again for a short time. Notice, that the transitions between "hot" and "cold" components are not abrupt: there are clearly time-periods where very "cold" Fe6+ and very "hot" Fe16+ co-exist.

These data provide a unique view of a CME associated with a cold plasma component, perhaps originating from an erupted filament. They provide valuable information about the CME between the time of solar observations with imaging instruments on SOHO and in situ plasma observations at 1 AU, i.e. electron and proton distributions measured by ACE/SWEPAM.

Text contributed by S. Hefti and T. H. Zurbuchen, University of Michigan.