1. Ejection of cool plasma into the corona - comparison of 1D and 3D coronal loop models
P.Zacharias1, S. Bingert2 & H. Peter2
1ISSI, Bern, Switzerland
2MPS, Katlenburg-Lindau, Germany
Fifth Solar Orbiter Workshop
September 10-14, Brugge, Belgium

2. Ejection of cool plasma in 3D MHD model
OVI 1032Å, log T=5.5
MgX 625Å, logT=6.0
box extension: 50 Mm x 30 Mm
time covered: 60 min
normalized currents
current fluctuations
Zacharias, Bingert & Peter 2011, A&A 532, A112
➜ blob follows magnetic field lines
➜ cool compared to coronal plasma
➜ thermal pulse

3. Overview
Our 3D MHD model blob-like structure following magnetic field lines result of heating event above chromosphere/thermal pulse
Comparison with 1D loop model confirm that thermal pulse leads to ejection of cool plasma into corona investigate loop flows during heating phase compare results to other 1D and 3D models
Comparison with observations search for similar features in Hinode/EUV imaging spectrometer (EIS) & SDO/Atmospheric Imaging Assembly (AIA) data
synthesized images from 3D MHD model
as AIA would observe the simulation in the
He II 304 (left) and FeIX/X 171A (right) channel on the solar limb.

4. Blob characteristics in 3D MHD model
moves along magnetic field lines (L=60 Mm)
diameter: 4-5 Mm (depending on LOS)
velocities: km/s ≈ sound speed
internal energy density: 1.5 mW m-3 ≈ HOhm ➜ pressure increase
kinetic energy density: 0.1 mW m-3 ≈ -v grad p ➜ pushes plasma upward

5. Blob characteristics in 3D MHD model
moves along magnetic field lines (L=60 Mm)
diameter: 4-5 Mm (depending on LOS)
velocities: km/s ≈ sound speed
internal energy density: 1.5 mW m-3 ≈ HOhm ➜ pressure increase
kinetic energy density: 0.1 mW m-3 ≈ -v grad p ➜ pushes plasma upward

6. Blob characteristics in 3D MHD model
moves along magnetic field lines (L=60 Mm)
diameter: 4-5 Mm (depending on LOS)
velocities: km/s ≈ sound speed
internal energy density: 1.5 mW m-3 ≈ HOhm ➜ pressure increase
kinetic energy density: 0.1 mW m-3 ≈ -v grad p ➜ pushes plasma upward

7. (Zacharias et al., in prep.)
3D MHD model
(Bingert et al. 2011)
1D loop model
(Zacharias et al., in prep.)
Pencil code (Brandenburg & Dobler 2002)
semi-circular loop: L=60 Mm
energy equation incl. heat cond., rad. losses & background heating term
heating pulse: variation of amplitude, width, duration & position along loop
Pencil code (Brandenburg & Dobler 2002)
small AR simulation: 50x50x30 Mm3
energy equation incl. heat cond. & rad. losses
heating mechanism: braiding of magnetic fieldlines (Parker 1972; 1983) by photospheric driver (Gudiksen & Nordlund 2002)

8. Temporal evolution of 1D coronal loop
temperature profile
space-time plot of temperature
thermal pulse ➜ ejection of cool plasma into the corona

9. Comparison of different ejection heights
space-time plot of temperature
injection height increases by
≈ 10 km/image

10. Variation of heating pulse length and width
space-time plot - temperature
non-localized
localized
long
short
space-time plot - velocity
v(tmax.heat)=22 km/s
v(tstart)=5 km/s
exclusively blueshifts during heating phase!

11. Comparison with other 1D and 3D models
3D MHD model (Hansteen et al. 2010): L≈7 Mm (network loops) rapid heating of material in place results in overpressure material is pushed upward into corona and downward towards chromosphere > blueshifts in coronal lines & redshifts in TR lines
1D loop model (Spadaro et al. 2003): L≈5-10 Mm (network loops) upflows during heating phase & downflows during cooling phase but also redshifts during transient heating near loop footpoints
Our 3D & 1D loop models: L≈60 Mm (AR loops) thermal pulse leads to ejection of cool plasma into corona only upflows during heating phase (so far) > might be due to different loop lengths

12. Comparison with observations

13. Hinode / EIS observations
HeII 256Å (logT=4.7)
“sit and stare” observation: 1h - 2 min cadence
movie courtesy David Williams (MSSL)

14. Hinode / EIS sit and stare observations
snapshots - time lag: 4 min - He II 256Å (logT=4.7)
➜ bullet-like feature that presumably follows the magnetic field lines
- visible in HeII 256Å channel of EIS
- not visible in higher-T channels
estimates:
- diameter: ≈7-10 Mm
- flight time: ≈30-35 min
- velocity: ≈100 km/s

15. SDO / AIA observations ➜ bright blob in HeII 304Å (logT=4.9)
➜ no detection in FeIX 171Å (logT=5.9)
FOV ≈ 49 Mm x 56 Mm
diameter: ≈2-3 Mm
flight time: ≈5 min
velocity: ≈ km/s
thanks to Eamon Scullion!

16. Conclusions
observational evidence of cool plasma ejecta in EIS & AIA data
1D loop model results:
successful reproduction of ejection following injection of heating pulse -> confirms proposed mechanism in 3D model
parameter study shows that whether or not ejection takes place depends on heating pulse injection height
exclusively blueshifts during heating phase (preliminary)
3D model
1D model
SDO/AIA 304Å