Magnetic Reconnection in the Earth's Magnetosphere Tatsuki Ogino
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Transcript of Magnetic Reconnection in the Earth's Magnetosphere Tatsuki Ogino
Magnetic Reconnection
in the Earth's Magnetosphere
Tatsuki Ogino
Solar-Terrestrial Environment Laboratory, Nagoya University
3-13 Honohara, Toyokawa, Aichi 442-8507, Japan
Satell ite anomalies relatedto Space Weather are on therise due to the increased useof composite materialsinstead of metal, and smaller,faster chip designs. The threeprinciple anomaly types are:surface charging, internalcharging, and Single EventEffects (SEE).
Satell ite anomalies relatedto Space Weather are on therise due to the increased useof composite materialsinstead of metal, and smaller,faster chip designs. The threeprinciple anomaly types are:surface charging, internalcharging, and Single EventEffects (SEE).
The Sun’s magnetic field is propagated farbeyond our planetary system by the solar wind.The interact ion between this interplanetarymagnetic field (IMF) and Earth’s ownmagnetic field is a significant component ofSpace Weather.
The Sun’s magnetic field is propagated farbeyond our planetary system by the solar wind.The interact ion between this interplanetarymagnetic field (IMF) and Earth’s ownmagnetic field is a significant component ofSpace Weather.
The Ionosphere is a layer of the Earth’supper atmosphere that contains free electronsand ions produced by solar UV radiation.Disruptions of the ionosphere cansignificantly affect radar, and radiocommunication.
The Ionosphere is a layer of the Earth’supper atmosphere that contains free electronsand ions produced by solar UV radiation.Disruptions of the ionosphere cansignificantly affect radar, and radiocommunication.
The Sun powers both the space weather and theterrestrial weather machines. Solar events, i.e.,explosions of charged particles and the dynamicsof magnetic and electric fields, cause hugechanges in the near-Earth space environment.Satelli tes and communication signals musttraverse this electric space.
The Sun powers both the space weather and theterrestrial weather machines. Solar events, i.e.,explosions of charged particles and the dynamicsof magnetic and electric fields, cause hugechanges in the near-Earth space environment.Satelli tes and communication signals musttraverse this electric space.
Solar-Terrestrial Environment
FlaresFlares
Solar WindSolar Wind
MagnetosphereMagnetosphere
Y. K ami de
X-raysX-rays
IonosphereIonosphere
Coronal Mass EjectionsCoronal Mass Ejections
PolarGeosynchronousGeosynchronous
複合系の物理複合系の物理
外からの作用
開放系磁気圏 直接作用
対流( Poynting Flux )
外への流出
蓄積作用プラズマ磁場(電流)
光・電磁波の反射・放射太陽風地球起源イオン流出
結合系渦度沿磁力線電流降下粒子重イオン流出
窓磁気リコネクション
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 )
循環
蓄積
エネルギー消費
窓磁気リコネクション
内部自立系電磁圏・熱圏(オーロラ)
太陽地球システムの特徴
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?
電子電流ionyJ
electronyJ
流出
拡散領域
流入
電子慣性
イオン慣性 電子電流
イオン電流
磁気圏と電離圏の結合
極域ポテンシャルの飽和
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
gy
swy
11J
pc
磁気圏
極域ポテンシャル
磁気圏と電離圏の大域的と局所的な関係を調べる
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
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
MP
V
| |V
V
| |V
flow normal to MP
flow along MP
Perpendicular flow to magnetopause (normal flow to reconnection line)
Parallel flow along magnetopause (convection)
solar wind
tailword flow
convection
Parallel flow along magnetopause (Tailward convection)
normal flow to reconnection line
V| |V
V
V
Problems of dayside magnetic reconnection in the earth’s magnetosphere
1. Can the reconnection rate be understood by ?• 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
3. Total amount of reconnection rate → Total flux across the open- closed boundary This measure is quite difficult
V , E
yE
Where magnetic reconnection occurs in the magnetosphere
・ Antiparallel conditionAngle of reconnected field lines, θMagnitude of reconnected field lines
・ Relative velocity of reconnected field lines ( )Inclination of the magnetic dipole axisWeakest place of magnitude along the field linesAntiparallel field conditionMagnetic equator
||~|| gIMF BB
V
gB
IMFB
reconnection linemagnetic equator
IMFB
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.
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
コンピュータで見るジオスペース
Southward IMF
Northward IMF
2. Effect of dipole tilt
Tilt angle is 30 degrees
SouthwardIMF Bz-5nT
NorthwardIMF Bz 5nT
Tilt Angle θ=30°Z
Z
X
X
15Re
15Re
-15Re
15Re
15Re
-15Re
-60Re
-60Re
3D Magnetic Field Line
Magnetic Equator
Tilt Angle θ=30°
Z
Z
X
X
30Re
30Re
-30Re
30Re
30Re
-30Re
-120Re
-120Re
Plasma Pressure
SouthwardIMF Bz-5nT
NorthwardIMF Bz 5nT
-30Re
30Re
-30Re
30ReY
Z
-30Re
30Re
-30Re
30ReY
Z
X=-15Re
SouthwardIMF Bz-5nT
NorthwardIMF Bz 5nT
Plasma Pressure
TAIL BOUNDARY
Comparison of Shape of the Neutral Sheet Between Simulation and Observations by Fairfield and Gosling
(Gosling et al. 1986 )
F ・・・ Fairfield near –30Re
FS ・・・ Fairfield near –20Re
G ・・・ Gosling near –15Re
G
-30Re
30Re
-30Re
30ReY
Z
SouthwardIMF Bz-5nT
3D visualization by VRML (Virtual Reality Modeling Language)
dipole tilt and southward IMF
Dipole Tilt
Magnetic Equator Hinging Point
θ
Reconnection Point(X=‐10 ~‐ 20Re)
Magnetic Axis
Reconnection Point
Hinging Distance(10Re)
Southward IMF
dipole tilt and northward IMF
Dipole TiltNorthward IMF
Magnetic Axis
Magnetic Equator Reconnection Point
Reconnection Point
Kinetic
Thermal
Poynting
Kinetic
Thermal
Magnetic
2
2
1V
2
3
2B2
1
xVV2
2
1
xV2
5
x)( BE
Energy Energy Flux
θ=30° θ=0°
X (Re) X (Re)
Kinetic
Magnetic
Thermal
Energy
30 00 300 0
10-3 10-3
エネ
ルギ
ー [
J/m
] Thermal
エネ
ルギ
ー [
J/m
]
Ene
rgy
Ene
rgy
θ =30°
0
0.00002
0.00004
0.00006
0.00008
0.0001
0.00012
0.00014
0.00016
0.00018
30.15 27.15 24.15 21.15 18.15 15.15 12.15 9.15 6.15 3.15 0.15 -2.85 -5.85 -8.85 -11.9 -14.9 -17.9 -20.9
X [Re}座標
エネ
ルギ
ー
poynting flux+ kinetic flux+ thermal flux+ poynting flux- kinetic flux- thermal flux-
θ =0°
0
0.00002
0.00004
0.00006
0.00008
0.0001
0.00012
0.00014
0.00016
0.00018
30.15 27.15 24.15 21.15 18.15 15.15 12.15 9.15 6.15 3.15 0.15 -2.85 -5.85 -8.85 -11.9 -14.9 -17.9 -20.9
X [Re}座標
エネ
ルギ
ー
poynting flux+ kinetic flux+ thermal flux+ poynting flux- kinetic flux- thermal flux-
tailwardThermal
Energy Fluxθ=30° θ=0°
tailwardPoynting
sunwardPoynting
10-4 10-4
00
X (Re) X (Re)3030 0 0
エネ
ルギ
ーフ
ラッ
クス
[J
/s]
tailwardKinetic
エネ
ルギ
ーフ
ラッ
クス
[J
/s]
Ene
rgy
Flu
x
Ene
rgy
Flu
x
3. Effect of dipole Tilt and IMF By component
Tilt angle is 30 degrees Northern hemisphere is smmer
0315
300270
0315
300270 300
315 0
315 0
45 90
315315
Configuration of 3D magnetic field lines for dipole tilt and IMF By-component
B IMF
Magnetic Equator
Reconnection for existence of dipole tile and IMF By
Geomagnetic field
Anti-parallelreconnection
Divergent flow
From the subsolar point
Figure 6. Ionospheric convection and potential in polar region
Green line is open-closed boundary
Comparison of throat regions in summer and winter
Summer and Northern Hemisphere
Winter and Southern Hemisphere
12
18
00
18
06
06
00
12Convection pattern, Energy flux Potential
χ = 30 º, θ= 315 º
A
100
50
0
-50
(KV)
90 ° 180 ° 270 °0 °270°
summer
winter
-+-+
-
-+-+
-
Angle of IMF )(
Polar cap potential versus IMF angle
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.
Earth
Sun
4. Effect of IMF Bx component Parker spiral
Duskward IMF B=15nT, Bx=-By and Bz=0 Bx<0
X
Y
B=15nT, Bx=-By and Bz=|Bx| Bx<0
X
Y
Duskward and southward IMFB=15nT, Bx=-By and Bz= -|Bx| Bx<0
X
Y
Dawn-dusk asymmetry of the plasma temperature, B=12.2nT, Bx=-By and Bz= -|Bx|
Duskward IMFB=12.2nT, Bx=-By and Bz=-|Bx|Ms=Vsw/Vth=4.04Ma=Vsw/Val=3.08M = Vsw/Vfms=2.45
x30Re
x30Re
y 30Re
z 30Re z 30Re
y30Re-120Re
Duskward IMFB=12.2nT, Bx=-By and Bz=-|Bx|
Ms=Vsw/Vth=4.04Ma=Vsw/Val=3.08
M = Vsw/Vfms=2.45
x30Re
x30Re
y 30Re
z 30Re z 30Re
y30Re
Duskward IMFB=12.2nT, Bx=-By and Bz=-|Bx|
Ms=Vsw/Vth=4.04Ma=Vsw/Val=3.08
M = Vsw/Vfms=2.45
Duskward IMFB=15.0nT, Bx=-By and Bz=-|Bx|Ms=Vsw/Vth=4.04Ma=Vsw/Val=2.05M = Vsw/Vfms=1.83
Duskward IMFB=15.0nT, Bx=-By and Bz=-|Bx|Ms=Vsw/Vth=4.04Ma=Vsw/Val=2.05M = Vsw/Vfms=1.83
y 30Re
x30Re
Duskward IMFB=15.0nT, Bx=-By and Bz=-|Bx|Ms=Vsw/Vth=4.04Ma=Vsw/Val=2.05M = Vsw/Vfms=1.83
Dawnward IMFB=12.2nT, Bx=-By and Bz=-|Bx|
Dawnward IMFB=12.2nT, Bx=-By and Bz=-|Bx|Ms=Vsw/Vth=6.39Ma=Vsw/Val=3.08M = 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
SOHO WIND
Geotail
Interball-Tail
Polar
10 Re
100 Re
220Re
EarthSun
ACE
Bz
By
P
V
n
00 12 2410:00 17:00
15:40UT Oct. 2003
16:01 UT Oct. 2003
Simulation ResultsMagnetopause approaches the geosynchronous orbit after the sh
ock 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 magnetosph
eric 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 bif
urcation) appears and the plasma sheet extension seems to conn
ect with the earth's ionosphere.