Observational evidence of a magnetic flux rope eruption associated with the X3 flare on 2002 July 15 Liu Yu Solar Seminar, 2003 June 16

Huairou Solar Observing Station ( ) 60 km from Beijing center, 10 km from the Great Wall

Introduction  Magnetic flux rope eruption, relation to CME  Some observational evidence  Problem of the triggering mechanism

Flux rope driven mechanisms Twisted-flux-rope model (Amari et al. 2000) Flux injection-driven model (Krall et al. 2000, 2001) oCatastrophic loss of MHD equilibrium (Lin & Forbes 2000; Low 2001; references therein; Roussev et al. 2003)

Twisted-enhanced flux rope (krall et al. 2000) A rapid increase in poloidal flux A CME of 1997 Apr 13

Numerical simulation by Hu (2001) -- the jump amplitude depends on the extend to which the ambient field in open Descend < critical value Ascend >critical value

Catastrophic loss of MDH equilibrium Four agents confining a balanced flux rope 1.Weight of helmet dome 2.Weight of prominence 3.Magnetic force of field from helmet dome 4.Magnetic pressure of open field outside helmet streamer

Effect of magnetic reconnection  Lin and Forbes (2000) — reconnection in the vertical current sheet below jumped flux rope Result: flux rope can be allowed to escape with a fairly small reconnection rate

Effect of ambient fields partly opened (Aulanier et al. 2000)  TRACE EUV observations  1998 July 14 AR8270

Sling-shot model for fast CMEs Low and Zhang (2002)

Limited resolution of previous observations by SOHO, YOHKOH, Fulldisk-Ha Chen et al (LASCO, 1997/4/30) Foley et al (AR9415) Yurchyshyn 2002 (Ha, 2002/1/4)

They told us little physical information about the triggering mechanism for flux rope eruption at the initiating stage.

A well observed eruption event by TRACE 1600A  2002/07/15 AR0030 (N19W01)  Erupting from very low atmosphere

Observations  X3 flare (peak 20:08 UT)  Fast halo-CME (>1000km/s)

Data  TRACE 1600A T: 4,000-10,000K (Handy et al. 1999) cadence: 1frame/sec spatial: 0.5arcsec/pix  MDI (magnetograms and dopplergrams) mode: high resolution cadence: 1frame/min spatial: 0.63arcsec/pix

Data  TRACE 5000A 1. to find obvious changes on photosphere 2. to co-align TRACE and MDI data  Ha images from Global Ha network (Steinegger et al.2000) Unfortunately, no RHESSI and Ha observations during the eruption

Note the slender filament-like structure ‘p’ in different wavelenths

BBSO (before eruption)

HSOS (after eruption)

Movie Double compact flares successively broke out before the peak of SXR flux (20:08 UT)

Two successive flares  Before 20:04 UT ribbons 1 and 2  After 20:04 UT ribbons 3 and 4

Magnetic flux profile SXR flux profiles

SXR flux profile TRACE flux profiles

Results from last image--  Coinciding with the impulsive rise of SXR flux, positive magnetic flux impulsively fell down with 10% loss, while the negative flux almost kept the same  The second flare (ribbons 3, 4) mainly contributed to the impulsive rise of the SXR flux.  The flux of the second flare reached its peak at 20:06 UT, while the first flare had already fallen down to its lowest level after peaked at 20:03 UT

Changes in WL morphology

Results from last image--  Structure ‘p’ was cut to be two parts from middle after the eruption  Its south-western half gradually disappeared in one hour

Summary The complicated eruption (19:59-20:08UT) can be divided into two short stages: (1)before 20:04, a flare broke out at the west side of the AR. (2) soon after 20:04, another flare broke out with its two ribbons running along the magnetic neutral line

Main observational results  The erupting plasma was in a rapidly rising rope-like structure  The eruption occurred just preceding the onset of its driven flare (the second flare)  Morphology and magnetic flux of one slender structure ‘p’ (-one footpoint ? ) developed rapidly on the photosphere

No breakout in high atmosphere seen from other space instruments ( EIT, LASCO), so the source region of the eruption should be low

Conclusions  The observational evidence strongly support the erupting flux rope model  A catastrophic loss of MHD equilibrium can be the primary driving mechanism  The conclusion is based on the judgment that the ambient fields of the flux rope were partly opened due to magnetic reconnection

‘p’ was one of the foot-points to drag the flux rope at the coronal base Initially, the flux rope should be confined by the overlying fields of the bipolar ‘P1-F1’

A cartoon for a possible model Before eruption, the twisted flux rope was in a relatively stable equilibrium

A strong current sheet was generated for the expansion of the delta- configuration ‘P-f’

A loss of MHD equilibrium was due to the decrease of the confining force

Discussion 1: CME Twisted flux rope should play an important role in current theories of CMEs More such observations should be examined in more detail, and its ramifications with respect to various theories of CMEs should be explored

Discussion 2: magnetic cancellation By modifying the line-tying condition for the flux rope, magnetic cancellation may trigger the eruption of a flux rope and help to transport magnetic complexity upward (Martin & Livi 1992…)

Puzzle Why fail to find the corresponding negative flux change for ‘p’ ?

Possible cause Maybe due to the limited resolution of magnetic field observation, i.e., the opposite flux for ‘p’ could exist in wider area with weaker intensity

Fine structure of ‘p’ Scharmer et al p f P

-The end- Thanks !