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



y 30Re

x30Re


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.

Documents

Magnetic Reconnection in the Earth's Magnetosphere Tatsuki Ogino