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1
Coronal Mass Ejections: Kinematic Evolution
Jie Zhang
George Mason University
August 3, 2006 Sci. & Tech. Univ. China Hefei
2
Outline
1. Space Weather Program at GMU
2. Overview of Space Weather
3. CMEs: kinematic evolution
4. CMEs, Flares and Magnetic Reconnection
5. Discussion
Space Weather Program at GMUSpace Weather Program at GMUSpace Weather Program at GMUSpace Weather Program at GMU
1. George Mason University: 30,000 students, the largest in Virginia
2. Suburb of Washington D.C., close to NASA/GSFC, NRL, APL, UMD
GMU
CapitalHill GSFC
APL
NRL
Space Weather Program at GMUSpace Weather Program at GMUSpace Weather Program at GMUSpace Weather Program at GMU
•Strategy: a system approach to address the integrated Sun-Earth connected system, and heliospher at large.
•Initiated in 2003
•Faculty– Dr. Ken Dere (Sun) – Dr. Bob Meier (Ionosphere)– Dr. Merav Ophere (Heliosphere, Sun)– Dr. Art Poland (Sun)– Dr. Bob Weigel (Magnetosphere)– Dr. Jie Zhang (Sun, Heliosphere)– Postdoctoral and Graduate Students
Research HighlightsResearch HighlightsResearch HighlightsResearch Highlights
•Sun-Earth Connection: CME, ICME and Geomagnetic Storms (Jie Zhang)
•CME Initiation and Acceleration (Jie Zhang)
•SEEDS (Solar Eruptive Event Detection System) (Jie Zhang)
Research HighlightsResearch HighlightsResearch HighlightsResearch Highlights
•Heliospheric Modeling (Merav Opher)
•ICME and Shock propagation Modeling (Merav Opher)
Research HighlightsResearch HighlightsResearch HighlightsResearch Highlights
•Coronal heating -- Art Poland– Measurements from SOHO data– Modeling
Research HighlightsResearch HighlightsResearch HighlightsResearch Highlights
•CHIANTI database (Ken Dere)
•CME
Research HighlightsResearch HighlightsResearch HighlightsResearch Highlights
•ViRBO (Virtual Radiation Belt Observatory) (Bob Weigel)
•CISM-DX
•TSDS
Research HighlightsResearch HighlightsResearch HighlightsResearch Highlights
•Ionosphere and Thermosphere (Bob Meier)– I-T system responds to solar &
geomagnetic forcing– Develop methods to image the global
system– Improve empirical and first principles
models
Space Weather: the EffectsSpace Weather: the EffectsSpace Weather: the EffectsSpace Weather: the Effects
Human Space Exploration
Satellite Operation
Imagination Communication and Navigation
Aviation
Power
Space Weather: Physical SystemsSpace Weather: Physical SystemsSpace Weather: Physical SystemsSpace Weather: Physical Systems
Space Weather: the ConnectionSpace Weather: the ConnectionSpace Weather: the ConnectionSpace Weather: the Connection
Courtesy of Odstrcil
Courtesy of Manchester
Space Weather: the DriverSpace Weather: the DriverSpace Weather: the DriverSpace Weather: the Driver
Eruptions caused by magnetic activities
Credit: NASA
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Evolution: Outer Corona
Outer corona, ~ constant speed e.g., > 2 Rsun by LASCO C2/C3
Time
Hei
gh
t
Time
Vel
oci
ty
18
Evolution: Inner Corona
Inner corona: fast acceleration e.g., < 2 Rs by LASCO C1 or MK4
Time
Hei
gh
t
Time
Vel
oci
ty
19
Example: 1998 June 11 event
C1: 15 imagesC2: 3 imagesC3: 8 imagesGOES X-ray Flare: C1.1
(Zhang Jie et al., 2001, 2004)
21
Example: 1996 Oct. 05 event
C1: 3 imagesC2: 3 images Flare: Not in NOAA catalog; A1.2 C3: 7 image
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Time
CM
E V
elo
city
Fla
re S
oft
X-r
ay
Flu
x
CME Flare (Soft X-ray) Phase 1 ---- Initiation Phase ---- Pre-flare Phase Phase 2 ---- Acceleration Phase ---- Rise Phase Phase 3 ---- Propagation Phase ---- Decay Phase
Phase 1
Onset 1 Onset 2
Peak
Phase 2 Phase 3
Complete Kinematic Evolution
Zhang et al. 2001Zhang et al. 2004
Gallagher et al. 2003Qiu et al. 2004
Kundu et al. 2004Sterling & Moor 2005
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Statistical Study: Accelerations
Main
Acceleration
Residual Acceleration
Inner Corona Outer Corona
Strong Almost zero
Zhang Jie et al. 2006 (ApJ Oct. Issue)
24
Event Selection
• We have systematically examined all LASCO C1 images, about 100,000 images in total from 1996 January to 1998 June
• Online event catalog at http://solar.scs.gmu.edu/research/cme_c1/index.html
• 50 events in this study, showing evolution in both inner and outer corona
• Calculating main acceleration:• Direct method• Indirect method: using flare rise time as proxy of
CME main acceleration time
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Main and Residual Acceleration Distribution
Main
(m/s2)
Residual
(m/s2)
median 170.01 3.1
average 330.9 0.9
St. dev. 664.8 25.4
minimum 2.8 -131
maximum 4464.9 52.0
Main
Residual
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Duration of Main Acceleration
Duration
(min)
median 54.0
average 180.0
St. dev. 285.9
minimum 6.0
maximum 1200.0
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Inverse Correlation Between Magnitude and Duration
A = 10000 X T-1
(m/s2) (min)
The fitting line corresponds to the equal velocity of 600 km/s
Duration
Ma
gn
itu
de
30
Discussion: 1
• CME main acceleration in the inner corona has a broad distribution, from several m/s2 to several thousand m/s2, with a median value at 170 m/s2.
•Continuous distribution of CME acceleration and velocity, which does not support the idea of two distinct classes of CMEs
•Description of two classes is only a convenience to refer to different events (Sheeley et al. 1999, Andrew & Howard 2000, Moon et al. 2002, Zhang Mei et al. 2002)
CME, Flare and Magnetic Reconnection
1996 to 2005
CME: 10507
Flare: 21347
X-class: 122 M-class: 1418C-class: 12922B-class: 6872A-class: 7
•Most CMEs (~90%) are accompanied by flares
•Except extremely gradual CMEs
•75% flares are confined, not associated with CMEs
• 5% X-class• 40% M-class (Andrews 2004)
32
CME, Flare and Magnetic Reconnection
•Flares are believed to be caused by magnetic reconnection
•Almost all impulsive CMEs are associated with flare
•What is the role of magnetic reconnection in CME:
• acceleration phase ? and• initiation phase ?
33
•In CME initiation phase, there is no X-ray flare, or very weak enhancement at best
•Magnetic reconnection plays an insignificant role in this phase, if any.
Magnetic Reconnection
34
•In acceleration phase, magnetic reconnection plays an active role.
•The temporal coincidence, between CME acceleration and flare energy release, suggests an active role
•The reconnection is not merely the consequence of the catastrophic loss of equilibrium of large scale eruption of coronal magnetic field
Magnetic Reconnection
35(Gallagher et al 2003)
•The acceleration of CME-associated TRACE EUV ejector also coincides with the GOES X-ray flare rise phase.
Magnetic Reconnection
36
(Qiu et al 2004)
•CME-associated filament acceleration, two-ribbon separation also temporally correlate with the flare main phase
Magnetic Reconnection
37 (Harrison 1986)
CME-flare spatial relation
•There were strong arguments against that flare-reconnection drives CME, based on
•Temporal disparity (proven wrong due to inappropriate linear extrapolation)
•Spatial disparity, flare not underneath the center of CME span
38
CME-flare spatial relation
•The asymmetric super-expansion of CME in the inner corona explains the spatial disparity in the outer corona
39
Role of Magnetic Reconnection
•In 2-D flux rope model, serves as tether cutting, allowing flux rope to escape
(Lin et al. 2004)
40
Role of Magnetic Reconnection
•In 3-D flux rope model, serves as poloidal flux injection, increasing self-Lorentz force (“hoop” force, and gradient force), and expulsing the flux. (Note, Chen & Krall model flux injection from sub-photosphere).
Chen & Krall 2003
41
Role of Magnetic Reconnection
•In break-out simulation•Breakout reconnection at the top removes the overlying field•Flare reconnection underneath forms the closed flux rope
(Lynch et al. 2004)
42
A Conceptual ProcessPhase of Energy Building-Up
And closing to critical point of instability
CME Initiation Phase
Flare-producing magnetic reconnection
CME Main Acceleration
Strengthening current sheetDriving magnetic inflow
CME Propagation Phase
Days, weeks
Tens of minutes,
Hours
minutes,Tens of minutes
days to affect the
Earth
43
Conclusion & Discussion•Broad and continuous distribution of CME acceleration
•A scaling law of CME acceleration: inverse linear correlation between acceleration and magntiude
•CME initiation is due to catastrophic loss of equilibrium; possible start of breakout reconnection
•CME fast acceleration is due to the flare-related magnetic reconnection
•What triggers the initiation? Accumulation of helicity? (Zhang Mei et al. 2006)
•Why most flares are confined?