Coronal Mass Ejections: Kinematic Evolution

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Coronal Mass Ejections: Kinematic Evolution

Jie Zhang

George Mason University

August 3, 2006 Sci. & Tech. Univ. China Hefei

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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)


•Heliospheric Modeling (Merav Opher)

•ICME and Shock propagation Modeling (Merav Opher)


•Coronal heating -- Art Poland– Measurements from SOHO data– Modeling


•CHIANTI database (Ken Dere)

•CME


•ViRBO (Virtual Radiation Belt Observatory) (Bob Weigel)

•CISM-DX

•TSDS


•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

Coronal Mass Ejections: Coronal Mass Ejections:

Kinematic EvolutionKinematic Evolution

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Tracking Evolution

EIT: disk to 1.5 Rs

C1: 1.1 to 3.0 Rs

C2: 2.0 to 6.0 Rs

C3: 4.0 to 30 Rs

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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

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Evolution: Inner Corona

Inner corona: fast acceleration e.g., < 2 Rs by LASCO C1 or MK4

Time

Hei

gh

t

Time

Vel

oci

ty

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Example: 1998 June 11 event

C1: 15 imagesC2: 3 imagesC3: 8 imagesGOES X-ray Flare: C1.1

(Zhang Jie et al., 2001, 2004)

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Example: 1997 Sep. 20 event

C1: 8 imagesC2: 3 images C2.3 flareC3: 7 image

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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)

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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

http://solar.scs.gmu.edu/research/cme_c1/index.html

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Source Regions

All close to the limb

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Main and Residual Acceleration Distribution

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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

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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)

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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 ?

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•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

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•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


35(Gallagher et al 2003)

•The acceleration of CME-associated TRACE EUV ejector also coincides with the GOES X-ray flare rise phase.


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(Qiu et al 2004)

•CME-associated filament acceleration, two-ribbon separation also temporally correlate with the flare main phase


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

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CME-flare spatial relation

•The asymmetric super-expansion of CME in the inner corona explains the spatial disparity in the outer corona

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Role of Magnetic Reconnection

•In 2-D flux rope model, serves as tether cutting, allowing flux rope to escape

(Lin et al. 2004)

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•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

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•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)

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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

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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?

Coronal Mass Ejections: Kinematic Evolution

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