Interaction of coronal mass ejections
with large-scale structures
N. Gopalswamy, S. Yashiro, H. Xie,
S. Akiyama, and P. Mäkelä
IHY – ISWI Regional meeting on Heliospheric Phenomena and Earth’s Environment
September 7 – 13, 2009 Šibenik, Croatia
Large-Scale Structures
•
•
•
•
CMEs
Coronal Holes
Global Field of the Sun
Heliospheric Current Sheet
CME Interactions
• Non-radial motion of CMEs during the
minimum phase
• CME – CME interactions during solar
maximum
• CME – Coronal hole interaction during the
declining phase
• CMEs tend to align with the heliospheric
current sheet: CME rotation
Non-radial motion: Toward Equator
Gopalswamy and Thompson, 2000
42 km/s
S30
Filippov et al., 2001
20 km/s
Gopalswamy et al., 2003 ApJ
Other Observations
White-light prominences (CME cores):
offset similar to Gopalswamy et al. 2003
Plunkett et al., 2001
Cremades et al. 2006 considered only
equatorward and poleward deflections
F ~ A/r
Cremades et al. 2006
Consequence of Equatorward Deflection:
More Magnetic Clouds during Solar Minimum
Phase
Rise:
Max:
Decl:
All:
Lat (N) Lat (S) CMD
25.6 -24.2 5.3
12.6 -20.0 9.7
8.2 -13.8 1.8
14.5 -19.7 6.1
Outstanding question:
Is the deflection due to
coronal-hole open field or the
global dipolar field?
Gopalswamy, 2006
Why driverless shocks from disk
center?
MAX
The limb sources are normal (geometrical
reason), but the
disk-center sources are anomalous
The anomaly seems to be due to the
presence of coronal holes near the source
region
DECLINING
The Solar Source of a “Driverless” Shock
CH
AR 0588
Compact AR 0588 to the
south of a large coronal hole
produced a 1368 km/s CME
from S18E15. CMEs from
such disk-center location
result in shock+ICME at
Earth. In this event only the
shock arrived. Why?
8
S1
S2
CME1
CME2
SHEATH
Disk-center CMEs, but only
shocks at 1 AU (S1, S2)
and no ejecta (No depressed Tp)
9
Open Field Lines on the Sun:
2004/04/06
The coronal hole (CH) influence
parameter (CHIP), viz.,
B2A/r2 = 26 G2
along PA = 137o due to the
NW CH [B = average photospheric
field inside CH; A = area of CH;
r = Distance of CH to the eruption
region]. CHIP is a vector pointing
from the CH centroid to the
eruption region
The smaller CH in the
south contributed very
little: the CHIP was
only 0.75 G2
The central position angle of
the CME was 167o, which is
close to the direction of the
CH influence
Red:
Negative
Blue:
Positive
CME
Coronal hole immediately to the north of AR 10588
10
Based on the east-west
orientation of the neutral
line and the location of the
large coronal hole to the
north, we expect the
northern leg of the flux
rope is negative, as is the
coronal hole. No
reconnection is possible
between the CME leg and
the CH field lines. The CH
influence parameter has a
value of 26 G2 which
pushes the CME below the
ecliptic, so the flux rope is
not observed at Earth. The
northern flank of the shock
is observed rendering it a
“driverless” shock
Magnetogram: white = +; black = MDI Magnetogram with extrapolated field lines
CH
Purple:
Open
White:
Closed
AR 0588
S18E15
2004/04/06 10:46 UT SOHO magnetogram
From: http://www.lmsal.com/forecast/TRACEview/images
courtesy: M. DeRosa & K. Schrijver
11
Coronal Hole Influence Parameter
Ai
ri
F
MPA
F = ∑ fi
fi = Ai<Bi>/ri
2
F = 14 G pointed along the PA (FPA) of 234o.
MPA
(Open field lines only shown)
Gopalswamy et al., 2009 JGR
The CME direction roughly coincides with the direction of F
Shocks
with ICMEs
CH have minimal effect:
CHs smaller and/or far
from the eruption
CH deflect CMEs toward
Sun-Earth line
F generally small (2.5 G
vs.5.8 G for driverless)
Why ‘driverless’ shocks from diskcenter CMEs?
Sun
Shock
Open field lines
from coronal hole
Shock ahead of the
deflected CME
Deflection
+
Observer
EUV Wave Reflection from CH: Higher
Alfven Speed in the CH
Gopalswamy, Yashiro, Temmer et al., 2009 ApJL
CME1 839 km/s
CME 2
1507 km/s
CME Cannibalism
Two CMEs from the same region AR
Only one shock and a merged ICME
CME interaction most common during the maximum phase
HCS affecting an ICME
Coronal field maps calculated for
CR2006 with CCMC/PFSS (top
and middle) and MAS models
(bottom).
Panels a, b and c show maps for
source surface radius of 1.6 R, d
and e show maps at 2.5 R, while
panel f shows MAS map at 16.5
R,. The thick black contour is
the coronal neutral line.
The red oval represents the halo
CME on Aug 14, 2003, which was
aligned with the coronal neutral
line at 1.6 R.
Yurchyshyn, 2008
Magnetic topology has changed
further outward from the solar
surface so that the neutral line
rotated by approx. 50 deg.
Summary
• CME propagation can be affected by global
solar field (min), CME interaction (max), and
coronal hole deflection (declining)
• The presence of coronal holes near the
eruption regions seem to make the CMEs
behave like limb CMEs
• When magnetic topology changes outward
from the solar surface, the neutral line seems
rotated and so does the CME axis.