Path of an electron from the Sun to the Earth

  • #1
mcastillo356
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Let's suppose a solar electron moving directly towards Earth's equator at a high speed. This electron meets Earth's magnetic field, which points to the north, at a distance ten times the Earth's radius, where magnetic field is almost uniform. Which will be the direction this electron describes?
Attempt to solution:
At the first moment, magnetic field yields the electron to the West. This is the result of the cross-product between two vectors: velocity and magnetic field. Eversince, where does it go?; why?
Thank
 

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  • #2
DaveC426913
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Your ultimate question was where does it go and why.
Did you not just answer that in the previous sentence?
Are you asking if we agree with your logic?
Or are you asking what the electron does once it's been deflected?
Can you clarify?

Also, is this homework?
 
  • #3
mcastillo356
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Hello, DaveC426913, forum. It's been a long time since my last post.
I'm asking what the electron does once it's been deflected. The text-book I am reading continues saying, in a brief text, that some of the electrons will be engaged to the magnetic field and sent to the poles. West at the first time, North and South at the end. The question is: what happens to the electron once deflected. Does it turn North, trapped in the magnetic field?; does it sorround west hemisphere before joining the magnetic field?; how can it end at the south, despite the magnetic field, that leads to the North?. The problem is that I've been given very few information. I know the first step, which consist in the cross-product and its inmediate consequence: a force with direction West: does it mean electron first goes West?; what must I understand by West?.
It's no homework. I am trying to finish to read the text-book, and understand it.
I am at the course before entering the University, the Grade in Maths, at spanish UNED (National University of Distance Education).
Hope to have been less implicit.
 
  • #4
DaveC426913
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Well I'll be darned. So it does.
e-view-portion-magnetopause-current-ecliptic-plane.gif


Read up on the Left Hand Rule of electromagnetics.
 
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  • #5
mcastillo356
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DaveC426913, thanks!
Watching the picture I can see the electrons and the protons are deflected, away from the Earth, by the magnetic field.
At the very first moment, the electron to the west of the magnetic field; and then (this is what I ignored until I've seen the picture) it describes a circle, to end up turning round and away from Earth.
Some of these particles get trapped in the magnetic field, and travel to the poles. The auroras seen near the Artic and Antartic latitudes.
Thanks again!
 
  • #6
vanhees71
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Well I'll be darned. So it does.
View attachment 262321

Read up on the Left Hand Rule of electromagnetics.
Then forget about it again, because it's confusing. Just use the right-hand rule all the time. If using it to deal with magnetic Lorentz forces, ##\vec{F}=q \vec{v} \times \vec{B}##, remember that for the electron ##q=-e<0##!
 
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  • #7
weirdoguy
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Then forget about it again, because it's confusing. Just use the right-hand rule all the time.

Amen to that. I say that all the time to all of my students. Don't make your life harder, there's enough things to remeber already!
 
  • #8
vanhees71
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I remember this "left-hand rule idea" as a completely failed didactic attempt of a well-meaning physics professor (experimental physics ;-)) to make live easier for biologists who usually struggle a lot with physics anyway. I had to take once a lab together with biologists, because I missed this lab for physicists. It was about the Hall effect. Usually if it comes to the Hall effect all the physicists present try to get the direction of the forces right using the right-hand rule. It's usually funny to see all your colleagues and yourself struggling to point the fingers in the correct directions.

Now these poor biologists learned that you "have to use the left-hand rule" for electrons. Some clever guys thought that they had to take into account the negative sign of the electron charge in addition, and the confusion was complete. I then just said, use the right-hand rule always and then you have to take into account the sign of the charge you are considering, i.e., flip the direction of the force, when this charge is negative. After that (the whole endeavor took about an hour) they understood the magnetic part of the Lorentz force much better.
 
  • #9
mcastillo356
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Ok, right-hand rule, and then take account of whether is a negative particle.
Thanks everybody!
 
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