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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• Compressible solutions – In general incompressibility will not always apply. – Usually this is approached by assuming that the system starts in equilibrium and that perturbations are small. • Assume uniform B 0 , perfect conductivity with equilibrium pressure p 0 and mass density ρ 0 ρ = ρ 0 + ρ p r B r u r J r E T T T T T T = p r = B r = u r = J r = E 0 0 + p r + b

– Continuity – Momentum – Equation of state ∇p = – Differentiate the momentum equation in time, use Faraday’s law and the ideal MHD condition where ∂ρ r = −ρ0( ∇ ⋅u) ∂t r ∂u 1 r r ρ0 = −∇p − ( B0 × ( ∇× b)) ∂t µ 0 ∂p ( ) 0 ∇ρ = Cs ∂ρ 2 ∇ρ r r r E = −u × B0 r ∂b r r r = −( ∇× E) = ∇× ( u × B0 ) ∂t 2 r ∂ u 2 r r r r − C ∇( ∇ ⋅ ) + × ( ∇× ( ∇× ( ∇× ( × 2 s u CA u C ∂t r r = C A B 1 0 ) 2 ( µ ρ A ))) = 0

– Continuity<br />

– Momentum<br />

– Equation <strong>of</strong> state ∇p<br />

=<br />

– Differentiate the momentum equation in time, use Faraday’s<br />

law and the ideal MHD condition<br />

where<br />

∂ρ<br />

r<br />

= −ρ0(<br />

∇ ⋅u)<br />

∂t<br />

r<br />

∂u<br />

1 r r<br />

ρ0 = −∇p<br />

− ( B0<br />

× ( ∇× b))<br />

∂t<br />

µ<br />

0<br />

∂p<br />

( ) 0<br />

∇ρ<br />

= Cs<br />

∂ρ<br />

2<br />

∇ρ<br />

r r r<br />

E = −u<br />

× B0<br />

r<br />

∂b<br />

r r r<br />

= −(<br />

∇× E)<br />

= ∇× ( u × B0<br />

)<br />

∂t<br />

2 r<br />

∂ u 2 r r<br />

r r<br />

− C ∇(<br />

∇ ⋅ ) + × ( ∇× ( ∇× ( ∇× ( ×<br />

2 s<br />

u CA<br />

u C<br />

∂t<br />

r r<br />

=<br />

C A<br />

B<br />

1<br />

0 ) 2<br />

( µ ρ<br />

A<br />

))) = 0

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