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 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 Capital Hill GSFC APL NRL

Space 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 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 Highlights Heliospheric Modeling (Merav Opher) ICME and Shock propagation Modeling (Merav Opher)

Research Highlights Coronal heating -- Art Poland –Measurements from SOHO data –Modeling

Research Highlights CHIANTI database (Ken Dere) CME

Research Highlights ViRBO (Virtual Radiation Belt Observatory) (Bob Weigel) CISM-DX TSDS

Research 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 Effects Human Space Exploration Satellite Operation ImaginationCommunication and Navigation Aviation Power

Space Weather: Physical Systems

Space Weather: the Connection Courtesy of Odstrcil Courtesy of Manchester

Space Weather: the Driver Eruptions caused by magnetic activities Credit: NASA

Coronal Mass Ejections: Kinematic Evolution

16 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

17 Evolution: Outer Corona Outer corona, ~ constant speed e.g., > 2 Rsun by LASCO C2/C3 Time Height Time Velocity

18 Evolution: Inner Corona Inner corona: fast acceleration e.g., < 2 Rs by LASCO C1 or MK4 Time Height Time Velocity

19 Example: 1998 June 11 event C1: 15 images C2: 3 images C3: 8 images GOES X-ray Flare: C1.1 (Zhang Jie et al., 2001, 2004)

20 Example: 1997 Sep. 20 event C1: 8 images C2: 3 images C2.3 flare C3: 7 image

21 Example: 1996 Oct. 05 event C1: 3 images C2: 3 images Flare: Not in NOAA catalog; A1.2 C3: 7 image

22 Time CME Velocity Flare Soft X-ray Flux CME Flare (Soft X-ray) Phase Initiation Phase ---- Pre-flare Phase Phase Acceleration Phase ---- Rise Phase Phase Propagation Phase ---- Decay Phase Phase 1 Onset 1 Onset 2 Peak Phase 2Phase 3 Complete Kinematic Evolution Zhang et al Zhang et al Gallagher et al Qiu et al Kundu et al Sterling & Moor 2005

23 Statistical Study: Accelerations Main Acceleration Residual Acceleration Inner CoronaOuter Corona StrongAlmost zero Zhang Jie et al (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 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

25 Source Regions All close to the limb

26 Main and Residual Acceleration Distribution

27 Main and Residual Acceleration Distribution Main (m/s 2 ) Residual (m/s 2 ) median average St. dev minimum maximum Main Residual

28 Duration of Main Acceleration Duration (min) median54.0 average180.0 St. dev minimum6.0 maximum1200.0

29 Inverse Correlation Between Magnitude and Duration A = X T -1 (m/s 2 ) (min) The fitting line corresponds to the equal velocity of 600 km/s Duration Magnitude

30 Discussion: 1 CME main acceleration in the inner corona has a broad distribution, from several m/s 2 to several thousand m/s 2, with a median value at 170 m/s 2. 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: Flare: X-class: 122 M-class: 1418 C-class: B-class: 6872 A-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 Process Phase of Energy Building-Up And closing to critical point of instability CME Initiation Phase Flare-producing magnetic reconnection CME Main Acceleration Strengthening current sheet Driving 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?