Earth’s MagnetosphereEarth’s Magnetosphere — — A very quick introductionA very quick introduction

Weichao TuWeichao Tu - LASP of CU-Boulder - LASP of CU-BoulderCEDAR-GEM Joint Workshop - Santa Fe, NM - 06/26/2011CEDAR-GEM Joint Workshop - Santa Fe, NM - 06/26/2011

Contents: Intro to Contents: Intro to MagnetosphereMagnetosphere• How is it formed?How is it formed?

• What does it look like?What does it look like?

• What’s inside?What’s inside?

• How does it vary?How does it vary?

• Why do we care?Why do we care?

How is it formed? How is it formed? – Sun-Earth Interaction– Sun-Earth Interaction

• Earth’s internal fieldEarth’s internal field– a tilted dipolea tilted dipole

• Solar windSolar wind– fast outflow of hot plasma: fast outflow of hot plasma:

charged particlescharged particles

– carry interplanetary magnetic carry interplanetary magnetic field (IMF)field (IMF)

• Charged particles in solar wind Charged particles in solar wind are swept by Earth’s magnetic are swept by Earth’s magnetic field, creating a cavity called field, creating a cavity called the the MagnetosphereMagnetosphere..– shelter the surface of Earth from shelter the surface of Earth from

energetic particles of the solar energetic particles of the solar windwind

NASA

What does it look like?What does it look like?– The Shape and Boundaries– The Shape and Boundaries

• An oval tear-drop shapeAn oval tear-drop shape

• MagnetopauseMagnetopause– outer boundary of the outer boundary of the

magnetospheremagnetosphere

– compressed in the dayside (10-compressed in the dayside (10-12 Re) and stretched in the 12 Re) and stretched in the nightside (magnetotail well past nightside (magnetotail well past 200 Re)200 Re)

• Bow shockBow shock– because solar wind is supersonicbecause solar wind is supersonic

• MagnetosheathMagnetosheath

• CuspsCusps

• Low-altitude boundary: Low-altitude boundary: IonosphereIonosphere

NASA

What’s inside?What’s inside?– Currents and Plasma – Currents and Plasma

PopulationsPopulations• Field-Aligned Field-Aligned

CurrentCurrent

• MagnetopausMagnetopause Currente Current

• MagnetotailMagnetotail– Tail currentsTail currents– PlasmasheetPlasmasheet– Tail LobesTail Lobes

• Trapped Particles Trapped Particles in in inner inner MagnetospheMagnetospherere

IRF web site

What’s inside?What’s inside?– Charged Particle Motions– Charged Particle Motions

• Gyromotion: ~ millisecond Gyromotion: ~ millisecond

• Bounce motion: ~ 0.1-1.0 Bounce motion: ~ 0.1-1.0 sec sec

• Drift motion: ~ 1-10 Drift motion: ~ 1-10 minutes minutes

Characteristic Characteristic timescales:timescales:

ESA

What’s inside?What’s inside?– Inner Magnetosphere– Inner Magnetosphere

• Ring CurrentRing Current– westward currentwestward current– southward magnetic field southward magnetic field

on ground, decreases the on ground, decreases the main field strengthmain field strength

– located at 3-5 Relocated at 3-5 Re– hot and tenuous plasmahot and tenuous plasma

• 10-200 keV, 1-10s cm10-200 keV, 1-10s cm--

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– contains the energycontains the energy

What’s inside?What’s inside?– Inner Magnetosphere– Inner Magnetosphere

• Ring CurrentRing Current– contains the energycontains the energy

• PlasmaspherePlasmasphere– considered an extension considered an extension

of ionosphere that co-of ionosphere that co-rotates with Earthrotates with Earth

– cold and dense plasmacold and dense plasma• <1-10s eV, 100s-1000 <1-10s eV, 100s-1000

cmcm-3-3

– contains the masscontains the mass– sharp outer boundary: sharp outer boundary:

plasmapause (3-5 Re)plasmapause (3-5 Re)

What’s inside?What’s inside?– Inner Magnetosphere– Inner Magnetosphere

• Ring CurrentRing Current– contains the energycontains the energy

• PlasmaspherePlasmasphere– considered an extension considered an extension

of ionosphere that co-of ionosphere that co-rotates with Earthrotates with Earth

– cold and dense plasmacold and dense plasma• <1-10s eV, 100s-1000 <1-10s eV, 100s-1000

cmcm-3-3

– contains the masscontains the mass– sharp outer boundary: sharp outer boundary:

plasmapause (3-5 Re)plasmapause (3-5 Re)

Model from Carpenter and Anderson [1992] Model from Carpenter and Anderson [1992]

Radial distance at equator (Re)

What’s inside?What’s inside?– Inner Magnetosphere– Inner Magnetosphere

• Ring CurrentRing Current– contains the energycontains the energy

• PlasmaspherePlasmasphere– considered an extension considered an extension

of ionosphere that co-of ionosphere that co-rotates with Earthrotates with Earth

– cold and dense plasmacold and dense plasma• <1-10s eV, 100s-1000 <1-10s eV, 100s-1000

cmcm-3-3

– contains the masscontains the mass– sharp outer boundary: sharp outer boundary:

plasmapause (3-5 Re)plasmapause (3-5 Re)

[Kavanagh et al., 1968]

““Separatrix”: where co-rotational electric field Separatrix”: where co-rotational electric field balances convection electric fieldbalances convection electric field

What’s inside?What’s inside?– Inner Magnetosphere– Inner Magnetosphere

• Ring CurrentRing Current– contains the energycontains the energy

• PlasmaspherePlasmasphere– contains the masscontains the mass

• Radiation BeltRadiation Belt– co-locates with ring co-locates with ring

current and plasmaspherecurrent and plasmasphere– contains energetic contains energetic

particles particles – proton beltproton belt

• confined to inner regions confined to inner regions of magnetosphere, <3 Reof magnetosphere, <3 Re

• energies: >10 MeVenergies: >10 MeV

– electron beltelectron belt

[Elkington et al., 2004]

AP8MIN Proton Distribution

Energy (MeV)

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Electron Radiation BeltElectron Radiation Belt• Two distinct regionsTwo distinct regions

– Inner Belt: Inner Belt: centers ~ 1.5 Recenters ~ 1.5 Re– Outer Belt: Outer Belt: centers ~ 4-5 Recenters ~ 4-5 Re– Slot Region: Slot Region: a region of a region of

depleted fluxdepleted flux

• Energy: <10 MeVEnergy: <10 MeV

Energy (MeV)

AE8MIN Electron Distribution

[Elkington et al., 2004]

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NASA

• Magnetospheric Magnetospheric

ConvectionConvection – Dungey CycleDungey Cycle– Feifei Jiang (UCLA)Feifei Jiang (UCLA)

• Geomagnetic SubstormGeomagnetic Substorm– AuroraAurora– Christine Gabrielse Christine Gabrielse

(UCLA)(UCLA) and and Carl Andersen Carl Andersen (UAF)(UAF)

• Geomagnetic StormGeomagnetic Storm– Lauren Blum (U CO)Lauren Blum (U CO)

• Geomagnetic Indices Geomagnetic Indices – Matina Gkioulidou (UCLA)Matina Gkioulidou (UCLA)

How does it vary?How does it vary?

NASA

Variations of Plasmapause LocationVariations of Plasmapause Location

[Baker et al., 2004]EUV Imager of IMAGE

Outer Electron Belt VariationsOuter Electron Belt Variations• Outer electron belt is highly dynamicOuter electron belt is highly dynamic

– variable variable peak flux locationpeak flux location; ; slot regionslot region often filled often filled– inner boundaryinner boundary correlates with correlates with plasmapause plasmapause locationlocation– Variations Variations time scalestime scales: storm/solar rotation/season/solar cycle: storm/solar rotation/season/solar cycle

(Extended from Li et al., GRL, 2006)

• Color-coded: Color-coded: SAMPEXSAMPEX 2-6 MeV electron flux.• Black curveBlack curve:: plasmapause location from an empirical model [O’Brien and Moldwin, 2003]

Why do we care?Why do we care?

– Space Weather– Space Weather• Radiation beltRadiation belt is the is the

environmentenvironment– lots of commercial and military lots of commercial and military

satellites operatesatellites operate

– major space weather activity major space weather activity occursoccurs

• Energetic particlesEnergetic particles can lead to, can lead to, e.g., e.g., charge deposition in charge deposition in sensitive electronicssensitive electronics on board on board spacecraft.spacecraft.

• Several Several satellite ‘anomalies’satellite ‘anomalies’ have been associated with have been associated with variations in the variations in the energetic energetic particle environmentparticle environment..– e.g., e.g., Galaxy 15 failureGalaxy 15 failure

NOAA

Why do we care?Why do we care?

– Space Weather– Space Weather• Radiation beltRadiation belt is the is the

environmentenvironment– lots of commercial and military lots of commercial and military

satellites operatesatellites operate

– major space weather activity major space weather activity occursoccurs

• Energetic particlesEnergetic particles can lead to, can lead to, e.g., e.g., charge deposition in charge deposition in sensitive electronicssensitive electronics on board on board spacecraft.spacecraft.

• Several Several satellite ‘anomalies’satellite ‘anomalies’ have been associated with have been associated with variations in the variations in the energetic energetic particle environmentparticle environment..– e.g., e.g., Galaxy 15 failureGalaxy 15 failure

Observations and ModelsObservations and Models

• More and better More and better observations and observations and modelsmodels are needed for are needed for understanding understanding magnetosphere magnetosphere dynamics.dynamics.

• ObservationsObservations– Low Earth Orbit Low Earth Orbit

(SAMPEX, DMSP)(SAMPEX, DMSP)– Geosynchronous Orbit Geosynchronous Orbit

(GOES, LANL)(GOES, LANL)– Eccentric Orbit (IMAGE, Eccentric Orbit (IMAGE,

CLUSTER, THEMIS, CLUSTER, THEMIS, RBSPRBSP))– CubeSatsCubeSats

• Alex Crew (UNH)Alex Crew (UNH)

• GEM ModelsGEM Models – Matt Gilson (UNH)Matt Gilson (UNH)

[Friedel et al., 2005][Friedel et al., 2005]

NASA/RBSP mission

Thank you!

Current Systems in the Current Systems in the MagnetosphereMagnetosphere

• There are many current There are many current systems in the systems in the magnetospheremagnetosphere

• Some flow perpendicular to Some flow perpendicular to the field, others along the the field, others along the fieldfield

• The diagram schematically The diagram schematically shows the following:shows the following:

– Magnetopause currentMagnetopause current

– Tail currentTail current

– Ring currentRing current

– Region 1 currentRegion 1 current

– Region 2 currentRegion 2 current

– Substorm current wedgeSubstorm current wedge

– Partial ring currentPartial ring current

Perspective View of R-1 & R-2 Perspective View of R-1 & R-2 CurrentsCurrents

The Tail The Tail CurrentCurrent• The tail current is The tail current is

produced by two produced by two solenoids downstream of solenoids downstream of Earth with current Earth with current flowing in opposite sense flowing in opposite sense in each solenoidin each solenoid

• The effect is a fringing The effect is a fringing field in the vicinity of the field in the vicinity of the Earth that reduces the Earth that reduces the horizontal componenthorizontal component

• The effect is stronger on The effect is stronger on night and evening side night and evening side creating an asymmetry creating an asymmetry in the surface fieldin the surface field

Particle fluxes in near Earth Particle fluxes in near Earth spacespace

plasmasphereplasmasphere Radiation Belts

(Sandel et al., 2003)

(from the Extreme Ultraviolet Imager of IMAGE)(from the Extreme Ultraviolet Imager of IMAGE)

• Magnetospheric Magnetospheric

ConvectionConvection – Dungey CycleDungey Cycle

Tsyganenko web site

How does it vary?How does it vary?

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Radiation effects on Radiation effects on spacecraftspacecraft

• Single event upset (SEU)Single event upset (SEU)– change of state caused by change of state caused by

energetic ions striking a energetic ions striking a sensitive node in a micro-sensitive node in a micro-electronic deviceelectronic device

• Deep-dielectric chargingDeep-dielectric charging– Energetic electrons penetrate a Energetic electrons penetrate a

particular component and build particular component and build up chargeup charge

– Eventual discharge like “mini-Eventual discharge like “mini-lightning strike”lightning strike”

• Surface chargingSurface charging– Lower energy electrons can Lower energy electrons can

build up charge on spacecraft build up charge on spacecraft surfacesurface

– Resulting discharge can Resulting discharge can scramble satellite signalsscramble satellite signals

D. N. Baker, Science 297, 1486, 2002D. N. Baker, Science 297, 1486, 2002