# Homework Help: Determine the number of times the magnetic field has wound around the Sun

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1. Feb 26, 2016

### Imagin_e

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

Hi,
I know that this probably is easy to calculate, but I have the ability to thing the opposite about problems, therefore I'm stuck with this one. The question is

Determine the number of times the magnetic field has wound around the Sun by a heliocentric distance of 70 AU.

2. Relevant equations

I guess that I have to find a relation between the circumference of the Sun (or a circle generally) and the length of something, in this case L=70 AU. But as I mentioned, I really don't know what to do.

Is it relevant to determine where the magnetic field source is located? If yes, then R=10Rs (Rs = radius of the Sun).

3. The attempt at a solution

2. Feb 26, 2016

### Staff: Mentor

You'll want to do some investigation on the topic of the interplanetary magnetic field. Find out where its base is "locked" to the rotation of the Sun, and how the field lines are carried outwards (what entrains the field lines?). Hint: find the radial speed.

3. Feb 26, 2016

### Imagin_e

I assume that the angular velocity for a charged particle in a magnetic field is:
T=2*π*m/qB ; m should be the mass of an electron (?) , q=the charge , B = magnetic field strength, which I have. And where it is "locked", isn't it the 10*Rs that I mentioned?
Thanks btw!

4. Feb 26, 2016

### Staff: Mentor

Take a look here to begin with.