Main Theme: Three Worlds of Super-CMEs● At home

Birth, development, and release

● At playAcceleration, propagation, in-

transit evolution● At work

Making superstorms

Subtheme: Super-CMEs are rare and weird like natural wonders

● At home Epitomes of explosive phenomena

in the local cosmos● At play

Hurricanes of space weather● At work

Radical transformers of magnetosphere coupling from solar wind dominated to ionosphere dominated

The Terrestrial System under Super-CME Conditions

George SiscoeBoston University

Continuum Magnetogram H alpha Soft X-ray Composite

Super-CMEs at HomeBirth, Development, and Release

Relation to active region, prominences, and “sigmoids”Illustrated by event on November 4, 2001

upperseparatrix

lowerseparatrix

upperseparatrix

upperseparatrix

lowerseparatrix

Photospheric Field Topology of Titov & Démoulin 1999 Model

Relation to magnetic arcadesIllustrated by Bastille Day event

Release Mechanisms

Terry Forbes

Breakout

Spiro Antiochos

Flux Cancellation

Conditions at Eruption

Observable Implication of CME Models (Crooker, 2005)

• Taken at face value, imprint of dipolar component on leading field and leg polarity favors streamer over breakout model by ~80%.

• FLUX-CANCELLATION MODEL• Dipolar fields reconnect• Leading field matches dipolar

component

• BREAKOUT MODEL• Quadrupolar fields reconnect• Leading field opposes dipolar

component

Super-CMEs at PlayAcceleration, propagation, in-transit evolution

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Jie Zhang data

Sun

Pre-CMEGrowthPhase

InflationaryPhase

CME

Geometrical Dilation + Radial Expansion Phase

MHD simulationPete Riley

Three Phases of CME Expansion

Information on Interplanetary CME Propagation

Gopalswamy et al., GRL 2000: statistical analysis of CME deceleration between ~15 Rs and 1 AU

Reiner et al. Solar Wind 10 2003: constraint on form of drag term in equation of motion

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drag Cd ρ (V-Vsw)2 Standard Form

Observed

Information on CME Parameters at 1 AU

Vršnak and Gopalswamy, JGR 2002: velocity range at 1 AU << than at ~ 15 Rs

Owen et al. 2004: expansion speed CME speed; B field uncorrelated with speed; typical size ~ 40 Rs

Lepping et al, Solar Physics, 2003: Average density ~ 11/cm2; average B ~ 13 nT

Accelerate

Decelerate

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40

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80

Vexp = 0.266 Vcme – 71.61

Analytical model of CME Acceleration and Propagation

Generalized buoyancy

Elliptical cross section

Variable drag coefficient

Satisfies Gopalswamy template

Satisfies Reiner template

Virtual mass

Comparison with MHDsimulation

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1400 Gopalswamy et al.

Variable CD

Fixed CDV

elo

cit

y (

km

/s)

Distance from the Sun (Rs)

Circular CME

1.5 2 2.5 3 3.5 4 4.5 5

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1000

Ac

ce

lera

tio

n (

m/s

/s)

Distance from Sun Center (Rs)

Virtual Mass

No Virtual Mass

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Ve

loc

ity

(k

m/s

)

Distance from Sun (Rs)

MHD Simulation

Analytical

drag Cd ρ (V-Vsw)2 Standard Form

Observed

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Predictability(Crooker)

from Crooker, 2004

• Cloud axis – Aligns with filament

axis (low) and HCS (high)

– Directed along dipolar field distorted by differential rotation

• Leading field– Aligns with coronal

dipolar field (high)• Application

– First part predicts the rest (Chen et al., 1997)

• Cloud axis orientation, Fair

– 28/50 (56%) align within 30° of neutral line [Blanco et al., 2005]

• Leading field, Good

– 33/41 (80%) match solar dipolar component with 2-3 year lag [Bothmer and Rust, 1997]

– 28/38 (74%) from PVO match [Mulligan et al., 1998]

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CME Propagation Models

• Empirical model of CME deceleration (Gopalswamy et al., 2000)

• Analytical model of CME propagation (Siscoe, 2004)

• Numerical simulation 0.5 to 50 AU (Odstrcil et al., 2001)

• Numerical simulation 1 Rs to 1 AU with two codes (Odstrcil et al., 2002)

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Gopalswamy Template

• Psw distributions in CIRs and CMEs (Lindsay et al., 1995)

• Ey distributions in CIRs and CMEs (Lindsay et al., 1995)

• GeoImpact of CMEs (Gosling, 1990)

Super-CMEs at WorkMaking Superstorms

Dynamic Pressure (nPa)

IonosphereDominated

Solar WindDominated

The Terrestrial System under Super-CME Conditions

● Vasyliunas Dichotomization Solar wind dominated Ionosphere dominated

● Solar wind dominated Global force balance via Chapman-Ferraro current system Dst responds to ram pressure

● Ionosphere dominated Global force balance via region 1 current systemNeutral flywheel effectNo (direct) Dst response to ram pressure Magnetopause erosion

● Transpolar potential saturation (TPS) Equivalent to ionosphere dominated regime

Evidence for TPS and the Hill model parameterization

oPVAε ~ 1

P = ionospheric Pedersen conductanceVA = Alfvén speed in the solar wind ε = magnetic reconnection efficiency

Key Point

By this criterion, the standard magnetosphere is solar wind dominated; the storm-time magnetosphere, ionosphere dominated.

Vasyliunas Dichotomization

Vasyliunas (2004) divided magnetospheres into solar wind dominated and ionosphere dominated depending on whether the magnetic pressure generated by the reconnection-driven ionospheric current is, respectively, less than or greater than the solar wind ram pressure.

The operative criterion is

Midgley &Davis, 1963

x

z

Chapman &Ferraro, 1931

Chapman-Ferraro Current System

ICF = BSS Zn.p./o

3.5 MA

Pertinent Properties of the Standard Magnetosphere

C-F compression= 2.3 dipole field

2x107 N

Ram Pressure Contribution to Dst

April 2000 storm

Huttunen et al., 2002

GOES 8

A Chapman-Ferraro property

Psw compresses the magnetosphere andIncreases the magnetic field on the dayside.

Chapman-Ferraro Compression

V

BE

Interplanetary Electric Field DeterminesTranspolar Potential

A magnetopause reconnection property

● Magnetopause reconnection

● Equals transpolar potential

● Transpolar potential varies linarly with Ey (Boyle et al., 1997)

● Magnetosphere a voltage source as seen by ionosphere

IMF = (0, 0, -5) nT

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Tra

ns

po

lar

Po

ten

tia

l (k

V)

Ey (mV/m)

Solar Wind Dominated MagnetosphereSummary

● Psw compresses the magnetospheric field and increases Dst.

● Ey increases the transpolar potential linearly.

● Magnetosphere a voltage source

Field compression and linearity of response to Ey hold foronly one of the two modes of magnetospheric responsesto solar wind drivers—the usual one.

Key Point

Then Came Field-Aligned Currents

Iijima &Potemra, 1976

Region 1

Region 2

Atkinson, 1978

R 1

C-F Tai

l

Total Field-Aligned Currentsfor Moderate Activity

(IEF ~1 mV/m)

Region 1 : 2 MARegion 2 : 1.5 MA

3.5

MA

5.5 MA

1 MA/10 Re

Question: How do you self-consistentlyaccommodate the extra 2 MA?

Answer: You Don’t. You replace the Chapman-Ferraro current with it.

IMF = (0, 0, -5) nT

Region 1 Current Contours

Region 1 Current Streamlines

IMF = (0, 0, -5) nT

Region 1 Force on Earth

5x

10

6 N

Impact of Region 1 Currents on Understanding Solar Wind-Magnetosphere Coupling

Summary

● Ionosphere and solar wind in “direct” contact

● Solar wind can pull on ionosphere as well as push on earth.

● Region 1 currents can usurp Chapman-Ferraro currents.

● Influence of ionosphere coupling increases relative to Chapman-Ferraro coupling as interplanetary electric field (Ey) increases.

During major magnetic storms, this leads to an ionosphere dominated magnetosphere

Key Point

What does this mean?

It means that whereas the standard magnetosphere interacts with the solar wind mainly by currents thatflow in and on the magnetosphere,

the storm-time magnetosphere interacts with the region 1 current system that links the ionosphere to the solar wind in the magnetosheath and the bow shock.

IMF = 0

Chapman-Ferraro

Region 1

IMF Bz = -30

Baseline (PSW=1.67, Σ=6)

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Ey (mV/m)

Tra

nsp

ola

r P

ote

nti

al (

kV)

PSW=10

Σ=12

Transpolar Potential Saturation

o

swP

H

/

314608

Saturation regime (big ESW)Linear regime (small ESW)

61

6.57/

swPswE

H

And most important

● Region 1 current gives the J in the JxB force that stands off the solar wind

● And communicates the force to the ionosphere

● Which communicates it to the neutral atmosphere as the flywheel effect

Bow Shock

Streamlines

Region 1Current

ReconnectionCurrent

RamPressure

Cusp

Richmond et al., 2003

Evidence of Two Coupling Modes

• Transpolar potential saturation

Instead of this

You have this• No dayside compression seen at synchronous orbit

Instead of this

You have this

Hairston et al., 2004

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ns

po

lar

Po

ten

tia

l (k

V)

Ey (mV/m)April 2000 storm

Huttunen et al., 2002

GOES 8

Cahill & Winckler, 1999

Dipole Field

To Resume

• Transpolar potential saturation

• No dayside compression seen at synchronous orbit

• No compression term (b) in the Burton-McPherron-Russell equation: dDst*/dt = E – Dst*/ Dst* = Dst - b√Psw

Instead of this

You have this

• Ring current model fits storm main phase better without pressure correction

• Possibly related:

Large parallel potential drops

Sawtooth events

b = 11.7

McPherron, 2004

Lee et al., 2004

Jordanova, 2005

Quiet Magnetosphere

1. Dominant current system Chapman-Ferraro (Region 1 lesser)

2. Magnetopause current closes on magnetopause

3. Magnetopause a bullet-shaped quasi-tangential discontinuity

4. Transpolar potential proportional to IEF

5. Solar wind a voltage source for ionosphere

6. Compression strengthens dayside magnetic field

7. Minor magnetosphere erosion8. Main dynamical mode: substorms9. Force transfer by dipole

Interaction

Superstorm Magnetosphere

1. Dominant current system Region 1 (no Chapman-Ferraro)

2. Magnetopause current closes through ionosphere and bow shock

3. Magnetopause a system of MHD waves with a dimple

4. Transpolar potential saturates

5. Solar wind a current source for ionosphere

6. Stretching weakens dayside magnetic field

7. Major magnetosphere erosion8. Main dynamical mode: storms9. Force transfer by ion drag

Summary

Dichotomization, transpolar potential saturation, no Dst responseto ram pressure, magnetopause erosion, neutral flywheel effect

all part of one story.

The Bimodal Magnetosphere

0o 5 nT45o 5 nT

90o 5 nT

180o 2 nT 180o 10 nT 180o 20 nT

180o 30 nT

Cahill & Winckler, 1999

Dipole Field

You have this

Region 1 Current System Fills Magnetopause

Region 1 CurrentContours

Properties of Ionosphere-Dominated Magnetosphere