Transcript Chapter 2 The nterplanetary Space

輔仁大學 太空物理
(Space Physics)
Chapter 2 The Interplanetary Space
(行星際太空)
2.1 Physical parameter
2.2 The Solar Wind
2.3 Interplanetary Magnetic Field
The interplanetary space
plasma
Gyro-motion
Gyro-radius
Gyro-frequency
帶電粒子在地球磁場中的運動方式
Mean free path(平均自由路徑)
http://abyss.uoregon.edu/
l >> rH (ν<<ω), Collision less plasma
l << rH (ν>>ω), Collision plasma
Scale height(標尺高)
Height
A
在溫度相同時，
物種A的質量___物種B的質量
在質量相同時，
物種A的溫度___物種B的溫度
B
Density, N
在電漿中，同時考慮電子與質子兩種不同的物質
經過簡化後可得到標尺高為：
Plasma frequency
E
ne ex
0
只考慮X方向
Debye Shielding
One dimension
D/2

D/2
0E2
D / 2
2 2 2
e
Z ni 3
2 2 2
2
dx  e Z ni / 2 0   x dx 
D
2
6 0
D / 2
ne k BTD e2 Z 2 ni23D

2
6 0
D 
 0 k BT
e 2 ne
k BT 1

.
m  pe
Debye length
Copyright
Debye Shielding
Plasma
Density
-3
ne(m )
16
Gas discharge
10
Tokamak
10
Ionosphere
10
Magnetosphere
10
Solar core
10
Solar wind
10
Interstellar medium
10
Intergalactic
medium
20
12
7
32
1
6
5
Electron temperature
T(K)
10
10
10
10
10
10
10
4
8
3
7
7
5
4
6
10
Magnetic field
B(T)
Debye length
λD(m)
--
10
10
10
10
10
−5
−8
-10
10
−9
−10
--
Source: Chapter 19: The Particle Kinetics of Plasma
http://www.pma.caltech.edu/Courses/ph136/yr2002/
10
−4
−4
−3
10
10
2
−11
10
10
10
5
Frozen in magnetic field
Magnetic flux
 
   B  ds


 d (s )
 d (s )

 

d d
B 

B  ds  
 ds   B 
    (u  B)  ds   B 
dt dt 
t
dt
dt



 d (s )
  
 

 
d
   (u  B)  ds   B 
  (u  B)  dl   B  (u  dl )  0
dt 
dt

d
0
dt

2.2 Solar wind
The solar wind is a continuous flow of charged particle
Slow solar wind: 250-400 km/s, 8ions/cm3 at 1AU
Fast solar wind: 400-800 km/s, 3ions/cm3 at 1AU
Laval’s nozzle
Low speed flow
High speed flow
Subsonic
flow
 dv
dA  v
  2  1
A  cs
 v
2
p
2k BT
cs 


m
Supersonic
flow
Equation of motion:
Continuity Equation:
 v  dv
 rc  dr
  1  21  
 r r
 vc  v
GM 

2cs
終極震波
日球層頂
~70AU
~100AU
High solar activity, high solar magnetic strength, but small heliosphere!
2.3 Interplanetary Magnetic Field
(IMF)
4.3.1 β-parameter
4.3.2 Spiral structure
 gas dynamic pressure
 magnetic pressure
gas dynamic pressure
magnetic pressure
β<<1, magnetic pressure >> dynamic pressure
β >>1, magnetic pressure << dynamic pressure
In rotating frame :
Plasma moving parallel to magnetic field
Normalize to solar surface magnetic field
Heliospheric Current Sheet