Transcript Document

Magnetic Reconnection
in the Earth's Magnetosphere
Tatsuki Ogino
Solar-Terrestrial Environment Laboratory,
Nagoya University
3-13 Honohara, Toyokawa, Aichi 442-8507, Japan
Solar-Terrestrial Environment
Coronal Mass Ejections
d
ic Fiel
gnet
ry Ma
The
The Sun’s
Sun’s magnetic
magnetic field
field is
is propagated
propagated far
far
beyond
our
planetary
system
by
beyond our planetary system by the
the solar
solar wind.
wind.
The
The interaction
interaction between
between this
this interplanetary
interplanetary
magnetic
magnetic field
field (IMF)
(IMF) and
and Earth
Earth’s
’s own
own
magnetic
field
is
a
significant
component
magnetic field is a significant component of
of
Space
Space Weather.
Weather.
laneta
Interp
Magnetosphere
X-rays
Satellite
Satellite anomalies
anomalies related
related
to
Space
Weather
are
on
to Space Weather are on the
the
rise
rise due
due to
to the
the increased
increased use
use
of
of composite
composite materials
materials
instead
instead of
of metal,
metal, and
and smaller,
smaller,
faster
chip
designs.
faster chip designs. The
The three
three
principle
principle anomaly
anomaly types
types are:
are:
surface
surface charging,
charging, internal
internal
charging,
charging, and
and Single
Single Event
Event
Effects
Effects (SEE).
(SEE).
Solar Wind
The
The Sun
Sun powers
powers both
both the
the space
space weather
weather and
and the
the
terrestrial
weather
machines.
Solar
events,
i.e.,
terrestrial weather machines. Solar events, i.e.,
explosions
explosions of
of charged
charged particles
particles and
and the
the dynamics
dynamics
of
of magnetic
magnetic and
and electric
electric fields,
fields, cause
cause huge
huge
changes
changes in
in the
the near-Earth
near-Earth space
space environment.
environment.
Satellites
and
communication
Satellites and communication signals
signals must
must
traverse
traverse this
this electric
electric space.
space.
Flares
Geosynchronous
Ionosphere
Polar
The
The Ionosphere
Ionosphere is
is aa layer
layer of
of the
the Earth’s
Earth’s
upper
atmosphere
that
contains
free
upper atmosphere that contains free electrons
electrons
and
and ions
ions produced
produced by
by solar
solar UV
UV radiation.
radiation.
Disruptions
Disruptions of
of the
the ionosphere
ionosphere can
can
significantly
significantly affect
affect radar,
radar, and
and radio
radio
communication.
communication.
Y. Kamide
複合系の物理
太陽地球システムの特徴
開放系
磁気圏
直接作用
対流（Poynting Flux）
外への流出
外からの作用
窓
磁気リコネクション
窓
磁気リコネクション
循環
蓄積
蓄積作用
プラズマ
磁場（電流）
太陽からの作用
エネルギーと物質
光・電磁波
太陽風
惑星間磁場（IMF）
結合系
エネルギー
消費
内部自立系
電磁圏・熱圏
（オーロラ）
渦度
沿磁力線電流
降下粒子
重イオン流出
光・電磁波の反射・放射
太陽風
地球起源イオン流出
磁気圏と電離圏の結合
極域ポテンシャルの飽和
極域ポテンシャル
 pc
磁気圏と電離圏の
大域的と局所的な
関係を調べる
J 11
E ysw
E yg

磁気圏
昼側リコネクションレートの飽和
リージョン１沿磁力線電流の飽和
電離層電気伝導度の効果
磁気リコネクション
セパラトリックスの構造
電子慣性スケールは重要?
磁気圏エネルギー
輸送をマクロとミクロな
物理から調べる
流入
電子電流
電子慣性
J yion イオン電流
流出
J yelectron
イオン慣性
拡散領域
電子電流
Solar Wind and Magnetosphere Interaction
Two important mechanism
1. Magnetic reconnection
2. Viscous interaction
Kelvin-Helmholtz instability
magnetic reconnection >> viscous interaction
2. Viscous interaction
Kelvin-Helmholtz instability
(Miura)
1. Magnetic reconnection
Dungey (1961)
Magnetic Reconnection of Earth's Magnetosphere
1. Effect of IMF Bz component
southward IMF versus northward IMF
Southward IMF
Northward IMF
Magnetic reconnection may be the most dominant
mechanism.
1. How well the antiparallel field condition is satisfied.
2. How slow the relative velocity between the reconnection
magnetic field lines is.
How much can the reconnection process be understood by a
superposition of the IMF and geomagnetic field?
What are different from a simple superposition?
(1) Movement of the reconnection field lines (convection)
(2) Configuration of the reconnection region might change
remarkably
(3) Temporal variation of reconnection process (intermittency)
Simple Superposition of the Geomagnetic Field and IMF
Bx>0, By<0, Bz=0
Bx>0, By<0, Bz=-Bx
solar wind
Perpendicular flow to magnetopause
(normal flow to reconnection line)
V
Parallel flow along magnetopause
(convection)
V| |
MP
V
flow normal to MP
V| | flow along MP
Parallel flow along magnetopause
(Tailward convection)
normal flow to
reconnection line
solar wind
V
tailword flow
V
V
V| |
convection
Problems of dayside magnetic reconnection in the earth’s magnetosphere
1. Can the reconnection rate be understood by E y ?
• Where (movement of place, 3D structure)
• When (temporal variation)
2. Can the reconnection potential φMR be distinguished from
the polar cap potential φPC ?
• Length of reconnection line (?)
• φPC increases when the reconnected magnetic field lines are
carried with the solar wind
V , E
3. Total amount of reconnection rate
→ Total flux across the openclosed boundary
This measure is quite difficult
Where magnetic reconnection occurs in the magnetosphere
・ Antiparallel condition
Angle of reconnected field lines, θ
Magnitude of reconnected field lines

・ Relative velocity of reconnected field lines ( V )
Inclination of the magnetic dipole axis
Weakest place of magnitude along
 the field
 lines
Antiparallel field condition | BIMF |~| Bg |
Magnetic equator

Bg

reconnection line

BIMF

BIMF
magnetic equator
2. Effect of IMF By and Bz
Two important conditions
(1) Anti-parallel field condition
(2) Magnetosheath plasma flow
How far is the reconnection region from
the subsolar point.
コンピュータで見るジオスペース
名古屋大学太陽地球環境研究所
共同観測情報センター・教授
荻野竜樹
Southward IMF
Northward IMF
2. Effect of dipole tilt
Tilt angle is 30 degrees
Tilt Angle θ=30°
3D Magnetic Field Line
Z 15Re
Magnetic Equator
Southward
X
IMF Bz
15Re
-5nT
-60Re
-15Re
Z 15Re
Northward
X
IMF Bz
15Re
5nT
-60Re
-15Re
Tilt Angle θ=30°
Plasma Pressure
Z 30Re
Southward
X
IMF Bz
30Re
-5nT
-120Re
-30Re
Z 30Re
Northward
X
IMF Bz
30Re
5nT
-120Re
-30Re
Plasma Pressure
X=-15Re
Z 30Re
Z 30Re
Y
30Re
-30Re
-30Re
Southward
IMF Bz
-5nT
Y
30Re
-30Re
-30Re
Northward
IMF Bz
5nT
Comparison of Shape of the Neutral Sheet Between
Simulation and Observations by Fairfield and Gosling
Z 30Re
TAIL BOUNDARY
Y
30Re
-30Re
G
-30Re
Southward
IMF Bz
-5nT
(Gosling et al. 1986 )
F
･･･ Fairfield near –30Re
FS
･･･ Fairfield near –20Re
G
･･･ Gosling
near –15Re
3D visualization by VRML (Virtual Reality Modeling Language)
dipole tilt and southward IMF
Dipole Tilt
Southward IMF
Magnetic Axis
θ
Reconnection Point
Hinging Point (X=‐10～‐20Re)
Reconnection Point
dipole tilt and northward IMF
Northward IMF
Magnetic Axis
Dipole Tilt
Reconnection Point
Reconnection Point
Energy Flux
Energy
Kinetic
1
2
V
2
Kinetic
1
2
 V Vx
2
Thermal
3

2
Thermal
5
 Vx
2
Magnetic
1 2
B
2
Poynting
(E B) x
Energy
θ=30°
θ=0°
10-3
Energy
エネルギー [J/m]
Kinetic
0
30
Magnetic
0
X (Re)
Thermal
Energy
エネルギー [J/m]
10-3
0
30
Thermal
0
X (Re)
Energy Flux
θ=30°
θ=30°
10-4
poynting flux+
kinetic flux+
thermal flux+
poynting flux-
kinetic flux-
thermal flux-
10-4
poynting flux+
0.00016
0.00016
tailward
Poynting
0.00014
tailward
Kinetic
0.00012
エネルギーフラックス
[J/s]
Flux
Energy
0.00018
Flux
Energy
エネルギーフラックス
[J/s]
0.00018
θ=0°
θ=0°
kinetic flux+
thermal flux+
poynting flux-
kinetic flux-
thermal flux-
tailward
Thermal
0.00014
0.00012
0.0001
エネルギー
エネルギー
0.0001
0.00008
0.00008
sunward
Poynting
0.00006
0.00006
0.00004
0.00004
0.00002
0.00002
0
30
0
30.15 27.15 24.15 21.15 18.15 15.15 12.15 9.15
0
6.15
X (Re)
3.15
X座標 [Re}
0.15 -2.85 -5.85 -8.85 -11.9 -14.9 -17.9 -20.9
0
30
0
30.15 27.15 24.15 21.15 18.15 15.15 12.15 9.15
0
X (Re)
6.15
3.15
X座標 [Re}
0.15 -2.85 -5.85 -8.85 -11.9 -14.9 -17.9 -20.9
3. Effect of dipole Tilt and IMF By component
Tilt angle is 30 degrees
Northern hemisphere is smmer
  270
  300
  315
  0
  270
  315
  315
  300
  300
  0
  0
  315
  0
  45
  90
Configuration of 3D magnetic field lines for dipole tilt and IMF By-component
  315
  315
Reconnection for existence
of dipole tile and IMF By
Divergent flow
From the subsolar point
B
IMF
Geomagnetic
field
Anti-parallel
reconnection
Magnetic Equator
Figure 6. Ionospheric convection and potential in polar region
χ = 30 º, θ= 315 º
Comparison of throat regions in summer and winter
Convection pattern, Energy flux
12
Summer and
Northern
Hemisphere
Potential
12
A
18
06
Green line is
open-closed
boundary
Winter and
Southern
Hemisphere
06
18
00
00
 (KV)
Polar cap potential versus IMF angle
summer
100
 +-  +
winter
50
0
-50
270°
0°
90 °
Angle of IMF
( )
180 °
270 °
 +-  +
-
Summary
1. A almost closed magnetosphere is formed for pure northward
IMF and no dipole tilt because high latitude tail reconnection
simultaneously occurs in both hemispheres.
2. If there exists finite IMF By component, the earth's magnetosphere
becomes open.
3. When the IMF has small duskward component (Bz>0 and By>0),
magnetopause reconnection occurs in dusk side and high latitude
region in the northern hemisphere. Open field lines become rich in
the dawn polar region because reconnected open field lines convect
from dusk to dawn in the dayside polar region.
4. If the dipole tilt exists, the earth's magnetosphere becomes again
open even for pure northward IMF and a north-south asymmetry
appears. Dayside reconnection occurs near the magnetic equator
where the geomagnetic field is weakest along the field lines.
5. When the dipole tilt and IMF By and Bz components simultaneously
exist, a complicated structure without any symmetric plane is
formed in the magnetosphere.
6. Anti-parallel reconnection is the primary phenomenon at the
dayside magnetopause for a finite By component and southward
IMF when the dipole tilt exists.
7. This is because reconnection around the magnetic equator and
noon-midnight meridian is suppressed due to poor satisfaction of
anti-parallel field condition and increase of magnetosheath flow,
and it occurs in the split anti-parallel field regions.
8. Polar convection in throat region becomes more east-west direction
in summer hemisphere and that does more noon-midnight direction
in winter hemisphere.
4. Effect of IMF Bx component
Parker spiral
Earth
Sun
Duskward IMF B=15nT, Bx=-By and Bz=0 Bx<0
X
Y
B=15nT, Bx=-By and Bz=|Bx| Bx<0
X
Y
X
Duskward and southward IMF
B=15nT, Bx=-By and Bz= -|Bx| Bx<0
Y
Dawn-dusk asymmetry of the plasma temperature, B=12.2nT, Bx=-By and Bz= -|Bx|
Duskward IMF
B=12.2nT, Bx=-By
and Bz=-|Bx|
Ms=Vsw/Vth=4.04
Ma=Vsw/Val=3.08
M = Vsw/Vfms=2.45
z 30Re
x
30Re
z 30Re
-120Re
y
30Re
Duskward IMF
B=12.2nT, Bx=-By and Bz=-|Bx|
Ms=Vsw/Vth=4.04
Ma=Vsw/Val=3.08
x
30Re
M = Vsw/Vfms=2.45
y 30Re
z 30Re
z 30Re
x
30Re
y
30Re
Duskward IMF
B=12.2nT, Bx=-By and Bz=-|Bx|
Ms=Vsw/Vth=4.04
Ma=Vsw/Val=3.08
x
30Re
M = Vsw/Vfms=2.45
y 30Re
Duskward IMF
B=15.0nT, Bx=-By
and Bz=-|Bx|
Ms=Vsw/Vth=4.04
Ma=Vsw/Val=2.05
M = Vsw/Vfms=1.83
Duskward IMF
B=15.0nT, Bx=-By and Bz=-|Bx|
Ms=Vsw/Vth=4.04
Ma=Vsw/Val=2.05
M = Vsw/Vfms=1.83
Duskward IMF
B=15.0nT, Bx=-By
and Bz=-|Bx|
Ms=Vsw/Vth=4.04
Ma=Vsw/Val=2.05
M = Vsw/Vfms=1.83
x
30Re
y 30Re
Dawnward IMF
B=12.2nT, Bx=-By and Bz=-|Bx|
Dawnward IMF
B=12.2nT, Bx=-By
and Bz=-|Bx|
Ms=Vsw/Vth=6.39
Ma=Vsw/Val=3.08
M = Vsw/Vfms=2.78
Simulation Results
Parker spiral with IMF Bx component creates a transient phenomenon with
dawn-dusk and north-south asymmetries in the earth's magnetosphere, and
the asymmetric structure is kept well in a quasi-steady state even for
a small IMF Bx component.
When the IMF becomes large and the Alfven Mach number becomes less than
about two, the asymmetric structure appears even in the magnetosheath
and becomes remarkable in the magnetosphere.
Through the bow shock the IMF increases and the plasma flow decreases
according to the Rankine-Hugoniot relationship.
Therefore the plasma flow is easily influenced by the IMF in the magnetosheath
and asymmetry appears by the effect of IMF Bx.
Summary
For non-zero IMF Bx in Parker spiral, magnetopause magnetic reconnection
occurs differently on dawn and dusk sides. The reconnection sites shift sunward
on dawn and tailward on dusk. IMF lines on dusk are straighter than those on
dawn. This increases the magnetic pressure on dusk and pushes the plasma sheet
toward dawn.
On the other hand, the IMF lines on dawn are bent sharply. This decreases the
magnetic pressure. The dawn-dusk asymmetry and the related magnetospheric
convection are the main cawses that the plasma sheet shifts up/down from equator
and is inclined, and the magnetotail is rotated to the sun-earth line. This also
causes asymmetric plasma flows and the tendency is largely enhanced for smaller
Alfven Mach number (<2).
This dawn-dusk asymmetric occurrence of dayside reconnection and induced
magnetospheric convection become main causes to create inclination of plasma sheet,
rotation magnetotail and also asymmetric plasma flows in the tail. As the results, tail
reconnection favorably occurs in dusk side due to the effects of the IMF Bx component
namely, the Parker spiral effect.
MHD Simulation of
the Solar Wind-Magnetosphere Interaction of
the Shock Wave Event on October 24, 2003
Occurrence of Abnormal Operation in a Satellite for
Environment Observation Technology, ADEOS-II (Midori-II)
10/24
16:13-16:17 UT Lowering of the electric power generated
by the solar cell
(10/25 01:13-01:17 JST)
15:25 UT Occurrence of SC in the Kakioka geomagnetic data
15:40 UT The maximum of about 2000 nT in AE
00:00-24:00 UT Magnetic storm did not occur (Dst > -65 nT)
Relative Location of ISTP Constellation during
Sun-Earth Connection Event
220Re
100 Re
10 Re
ACE
Polar
SOHO WIND
Geotail
Interball-Tail
Sun
Earth
Bz
By
P
V
n
00
10:0012
17:00
24
15:40UT Oct. 2003
16:01 UT Oct. 2003
Simulation Results
Magnetopause approaches the geosynchronous orbit after the
shock wave arrives.
Plasma sheet goes around the dayside magnetosphere from the
magnetotail along magnetospheric convection. Hot plasma of the
plasma sheet fills the geosynchronous region by the
magnetospheric convection.
Inclination of the plasma sheet is reversed in y-z cross section as
the IMF By changes from negative to positive at 15:30 UT. In the
case, the plasma sheet is twisted, a plasma extension (or lobe
bifurcation) appears and the plasma sheet extension seems to
connect with the earth's ionosphere.