A Brief Introduction to Space Plasma Physics.pdf - Institute of ...

A Brief Introduction to Space Plasma Physics.pdf - Institute of ... A Brief Introduction to Space Plasma Physics.pdf - Institute of ...

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10.02.2014 Views

– For a plane wave solution – The dispersion relationship between the frequency ( ) and the propagation vector ( ) becomes This came from replacing derivatives in time and space by – Case 1 r r r r r u r ~ exp[ i( k r ⋅ −ω t)] ω k r r r r r r r r r r r k )[( C ⋅ k ) u − ( C ⋅u) k − ( k ⋅u C ] = 0 2 2 2 − ω u + ( Cs + CA)( k ⋅u) k + ( CA ⋅ A A ) A k r ⊥ r B 0 2 r ω u ∂ → −iω ∂t r ∇ → ik r ∇⋅ → ik ⋅ r ∇× → ik × = ( C 2 s + C 2 A r r r )( k ⋅u) k

• The fluid velocity must be along k r and perpendicular to 0 B r 0 k r u r • These are magnetosonic waves – Case 2 ( k B r r 1 2 2 v ph = k ( ω ) = ± ( C s+ C k k r B r 0 2 2 2 r r 2 2 2 r r CA −ω ) u + (( Cs CA) −1) k ( CA ⋅u) CA = 0 r • A longitudinal mode with u k r with dispersion relationship ω k (sound waves) r • A transverse mode with k ⋅u r ω = 0 and = ± C A (Alfvén waves) k 2 A ) = ± C s

– For a plane wave solution<br />

– The dispersion relationship between the frequency ( ) and<br />

the propagation vec<strong>to</strong>r ( ) becomes<br />

This came from replacing derivatives in time and space by<br />

– Case 1<br />

r<br />

r<br />

r<br />

r<br />

r<br />

u<br />

r<br />

~ exp[ i(<br />

k<br />

r ⋅ −ω<br />

t)]<br />

ω<br />

k r r r r r r r r r r r<br />

k )[( C ⋅ k ) u − ( C ⋅u)<br />

k − ( k ⋅u<br />

C ] = 0<br />

2 2 2<br />

− ω u + ( Cs<br />

+ CA)(<br />

k ⋅u)<br />

k + ( CA<br />

⋅<br />

A<br />

A<br />

)<br />

A<br />

k<br />

r ⊥<br />

r<br />

B 0<br />

2 r<br />

ω u<br />

∂<br />

→ −iω<br />

∂t<br />

r<br />

∇ → ik<br />

r<br />

∇⋅ → ik ⋅<br />

r<br />

∇× → ik ×<br />

= ( C<br />

2<br />

s<br />

+<br />

C<br />

2<br />

A<br />

r r r<br />

)( k ⋅u)<br />

k

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