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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20
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
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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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Tra
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