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

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• The fluid velocity must be along k r and perpendicular <strong>to</strong><br />

0<br />

B r<br />

0<br />

k r u r<br />

• These are magne<strong>to</strong>sonic waves<br />

– Case 2<br />

( k<br />

B r r<br />

1<br />

2<br />

2<br />

v<br />

ph<br />

= k ( ω ) = ± ( C<br />

s+<br />

C<br />

k<br />

k r B r<br />

0<br />

2 2 2 r<br />

r<br />

2 2 2 r r<br />

CA<br />

−ω<br />

) u + (( Cs<br />

CA)<br />

−1)<br />

k ( CA<br />

⋅u)<br />

CA<br />

= 0<br />

r<br />

• A longitudinal mode with u k<br />

r<br />

with dispersion relationship ω<br />

k<br />

(sound waves) r<br />

• A transverse mode with k ⋅u<br />

r<br />

ω<br />

= 0 and = ± C A<br />

(Alfvén<br />

waves)<br />

k<br />

2<br />

A<br />

)<br />

= ±<br />

C s

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