Subject:
Re: palm springs
From:
Simon Walker <walker@acse.shef.ac.uk>
Date:
Wed, 23 Feb 2005 15:48:35 +0000 (GMT)
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pickett@uiowa.edu
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Simon Walker <walker@acse.shef.ac.uk>
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Hi Jolene,

I haven't left yet! I know Sheffield appears to be the back of
beyond, almost at the ends of the Earth but it doesn't take that
long to go anywhere. It just feels like it does. I plan to make my way
to Heathrow tomorrow afternoon weather permitting . Its currently
snowing and we have almost half an inch in Sheffield. This is usually
more than enough to bring all types of transport to a grinding halt.
We fly on Friday morning.



> Many thanks for the plots.  I finally got a chance to look at them at
> home last night.  Yes, they will do, but if you haven't left yet, could
> you answer a couple of questions.  What mode was EFW in to
> make these measurements (burst?, filter?) ?  


The data come from the internal burst memory available within
EFW. This memory stores data when some trigger condition is satisfied.
The data is unfiltered, and is sampled at 9000Hz.


> Also, what is the
> conclusion from the velocity plot?  Is it the case that the average
> velocity of the structures is about 1000 km/s, heading upstream,
> primarily in the direction of the ion foreshock?  If not, can you
> please et me straight.  It looks to me like these examples you
> sent all have time durations around 1 millisecond.  If I have more
> questions, I can probably catch you at the conference.


I agree with your conclusions about the velocity plot. 
These features appear to propagate away from the shock front in the
upstream direction. Perhaps this is due to the events analysed being
in the foot region of the shock ie infront of the ramp. It is also
interesting that the velocity vector appears to be neither perp
nor para to B (see attached figure) in the spin plane. 
The problem may be that B is
sampled at 22.*** Hz, and so small scale structures wil probably
not be seen. This could also do with more statistics.


Looking forward to seeing you and the Sun (in that order).


    Simon