# Calculating the upward and downward plasma speeds

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1. Jan 21, 2016

### Tom-Physics

1. The problem statement, all variables and given/known data
Hi!

I have trouble with calculating the upward and downward plasma speeds. I have the necessary data and an equation that is useful (I think), but I'm stuck.

2. Relevant equations
The shock jump number Zs=3 in this case , and I've calculated the shock wave speed (555 km/s), which was calculated from the plasma density. The densities are n1=30 cm^-3 and n2=90 cm^-3 if you want to know.
And now, I need the upstream and downstream plasma speeds.

3. The attempt at a solution
I know that one equation that can be used is:
u'1/u'2==B2/B1=n2/n1Zs

Here, u'1 is the upward speed and u'2 the downward.
But this doesn't give me any solutions because we have two unknowns .I know that the answers should be -285 km/s and -95 km/s respectively.

2. Jan 27, 2016

### Staff: Mentor

Could you add some context? This thread is literally the only google hit where "shock jump number" is used as an expression. What is that?

Shock wave of what, and how did you calculate its speed? What do the two different densities represent?