On mass evolution of CMEs

ESMP-14 Dublin

Li Feng , Bernd Inhester , Yuming Wang , Fang Shen , Chenglong Shen , Weiqun Gan

1. Max Planck Institute for Solar System Research, Germany2. Purple Mountain Observatory, China3. University of Technology and Science,China4. National space science center, China

Mass evolution in coronagraph images Try to answer two questions: 1. Why the mass of a CME increases with time, physically does it come from the convected mass from the lower corona in the dimming region or the piled-up mass of solar wind? 2. When the mass is convected from the lower corona to the coronagraph FOV, how the flow speed is distributed in a CME?Conclusion and outlook

Thomson scattering

χ

b/bs: brightness in units of MSBσ: differential Thomson scattering cross sectionμ: limb darkening coefficientχ: scattering angleA, B, C, D: known functions of the distance of the scattering location

Column density + pixel size +He ： H=1 ： 10 mass in each pixel

base-difference image COR 1+2 B LASCO C2

COR1+2 A

GCS forward modeling

CME pro

pagation

Mass_A: total mass from COR A

Mass_B: total mass from COR B

Mass=0.5*(mass_A+mass_B)

Mass increase due to:1. occulter effect ： more mass enters the FOV of coronagraph? 2.solar wind plasma piled up in front of a CME? 3.continuous outflow from the low corona in the dimming region ?At what height the three possibilities are dominated, respectively?

Free parameters:hocc: the height of an effective occulter edgem0: a modeled initial mass below the occulter edgeΔm: mass increase per solar radius

True mass evolution model without an occulter: m(h)=m0+Δm(h-hocc)

Bein et al., 2013

at lower height

Apparent mass evolution with an occulter for a conic-cone CME

Red: true evolutionGreen: apparent evolution

Tappin et al. (2006)

Acme=Wface*Wedge*hfront2

ρSW (r) and vSW (r) around the CME: 3D MHD simulation: global 3D solar wind distribution (Shen et al., JGR, 2007, 2013)

distance (Rs)

1. dm/dt from snow plough model is lower and flatter2. Discrepancy between the measured and modeled dm/dt decreases with time3. Piled-up solar wind mass M_pile: M_pile/M_15Rs=30%4. An upper limit5. Results for eight CMEs with different speeds: M_pile/M_15Rs=10% ~ 33%

CME speed (km/s)

measurement

model

Mass= density depletion * dimming area * dimming depth* mi

304 171 193 211 335 94 131

Doppler velocity （ Tian et al., 2012)

before

after

difference

CME on 2011-06-21

Mass= density depletion (Δ N)* dimming area (S) * dimming depth (L) * m

i Tian et al. (2012)

DEM analyses (cheng et al. 2012)

S= sum of pixels whose EM is less than 85% of EM before the eruptionL= sqrt (S)N=sqrt(EM/L)

1. Mass from dimming: from 40% to 50 %.2. Lower limit: transition region outflows refill the coronal dimmings

coronagraph

dimming

Why does the apparent mass increase?1. The geometrical occulter effect plays its role at height below 7~8 Rs.2. The solar wind pileup can contribute up to 10%~33% of the mass in

coronagraph images 3. The mass loss in the dimming region is at least 40%~50% of the mass

in coronagraph images for the CME on 2011-06-21.

If the mass increase mostly comes from the dimming region, how is the mass convected from the lower corona accross the FOV of coronagraph?

Speed distribution in a slow CME (v < 500 km/s)

Under the assumption that the CME mass all comes from the lower corona

The mass change with time in shells from ri to rend is due to the mass flow at r=ri

ri

rend

m(ri, tj)

v(r, tj) increases with distance and it does not follow a linear pattern.

v(ri,t) decreases with time

Lagrangian trajectories of different shells

Subjective leading edge positions

1.When a CME is within the COR FOV, most of its mass come from the dimming region and the solar wind pileup has less contribution.

2.We derived the speed distribution of each shell in a slow CME, and it increases with distance and decreases with time.

backupslides

Lax-wendroff scheme is used to calculate the mass profile m(r, ti+1) in green from the measured m(r, ti) in white. Orange: measured m(r, ti+1)

ICME: Image noise, pre-CME image subtraction

Cplasma: in an average CME, the majority of the plasma is fully ionized

He composition: 6%~10%

Ce: convert brightness to mass in a pixel according to the Thomson Scattering Propagation

direction

CME width

Region definition

Region of interesting /Sector definition

3D MHD simulation: global 3D solar wind distribution (Shen et al., JGR, 2007, 2013)

B: Potential field extrapolated from photospheric synoptic mapV ： Parker’s solar wind solutionT : adiabatic process N: momentum conservation