Deflected Propagation of CMEs:
One of the Key Issues in Space Weather Forecasting
Yuming Wang
University of Science and Technology of China, Hefei, China
Contributors: Chenglong Shen, Bin Zhuang, and SEPC@NSSC, CAS
AOSWA, Jeju, Korea 2016.10
Major drivers of hazardous space weather
• 2003.10.30 “Halloween” event
-383 nT
Vcme=2460 km/s, V1AU≈1500 km/s
• 2000.07.16 “Bastille Day” event
-301 nT
Vcme=1670 km/s, V1AU>1000 km/s
• 1989.03.13 “Quebec” event
-589 nT
V1AU>1000 km/s
• 1859.09.01 “Carrington” event
-1760 nT (Tsurutani et al., 2003)
V1AU≈2000 km/sProbability: once per 150 years
Lucky in solar cycle 24
• The fastest CME over 28 years NOT facing on the Earth (e.g., Russell et al., 2013) STB STA
SOHO
Event Vcme(km/s) V1AU(km/s) B(nT) Dst(nT)
2012.7 3400 >2000 >100 ?
2003.10 2460 1500
The largest geomagnetic storm in solar cycle 24
2015.3.17 “St. Patrick’s Day” event (e.g., Kataoka et al. GRL, 2015, Wang Y. et al. JGR, 2016)
-223 nT
• March 14, ~12:36 UT
Preceding CME: slow,
toward the south
• March 15, ~01:36 UT
Main CME: fast,
toward the west
• Forecasting by SWPC of NOAA: G1 level,
minor geomagnetic disturbance
• The fact: G4 level, a major storm, unexpected
Another example: a limb CME hit the Earth (Wang Y. et al. 2014)ST-A SOHO ST-B
• Initially facing
to ST-B
• Actually
encounter the
Earth
Two long-standing puzzles
1. Not all of frontside CMEs can encounter the Earth (e.g.,Webb et al., 2001;Wang Y. et al., 2002; Zhao & Webb, 2003; Yermolaev et al., 2005; Shen C. et al., 2014)
• Only about 60 – 70% of frontside halo CMEs can arrive at the Earth
• Only about 50% of frontside halo CMEs have geoeffectiveness
2. Not all of nonrecurrent geomagnetic storms or ICMEs can be tracked
back to a frontside CME (e.g., Cane et al., 2000; CaneandRichardson, 2003; Yermolaev et al., 2005; Zhang et
al., 2007)
• Problem storms: no solar source can be identified (e.g., Webb et al., 2003; Schween et al.,
2005)
What control the likelihood of a CME hitting the Earth?
Size & Direction
• Size: roughly radial expanding, angular width is almost constant (e.g., Schween et al., 2005)
• Direction: may change due to
• Interaction with ambient solar wind and magnetic field (e.g., Wang Y. et al., 2002, 2004, 2006, 2014;
Gopalswamy et al., 2003; Cremades et al., 2006; Shen C. et al., 2011; Gui et al., 2011; Isavnin et al. 2013, 2014)
• Interaction with other magnetized structures (e.g., Wang Y. et al., 2011; Lugaz et al., 2012; Shen C. et al., 2012)
• Change in both latitude and longitude
• How to measure or estimate the trajectory of a CME:
• multiple view angles (SOHO, STEREO)
• reconstruction/modeling for CME (GCS, triangulation, etc.) and background solar wind
The largest geomagnetic storm in solar cycle 24
• Fitted by
velocity-
modified
Lundquist flux
rope model
• Implying a 12°
deflection
toward the east
B0 = 32 nT
R = 0.09 AU
Theta = -45 deg
Phi = 348 deg
H = +1
d = -0.82 R
v_x = -540 km/s in GSE
v_y = 59 km/s
v_z = -27 km/s
v_exp = 51 km/s
v_pol = 45 km/s
Sun 1AUIP Space
?GCS reconstruction
Wang Y. et al. JGR, 2016
Reconstruct the trajectory of the CME
• Background solar wind from 3D numerical MHD simulation (Shen F. et al., 2007, 2011)
• CME speed from drag-based model (DBM, Vrsnak et al., 2013)
Online tool: http://oh.geof.unizg.hr/DBM/dbm.php
• CME trajectory from DIPS model (Wang Y. et al., 2004, 2014)
Online tool: http://space.ustc.edu.cn/dreams/dips
• Deflected toward the east by about 12° , increasing the geoeffectiveness of the CME
The 2008 September limb CME event
• The slow CME was deflected toward the west by about 30°
Wang Y. et al., JGR, 2014
Deflection is a key issue in space weather forecasting
Three possible mechanisms
Deflection in corona due to magnetic energy density gradient (e.g., Gopalswamy et al., 2003; Cremades et al., 2006; Wang et al., 2011; Shen et al. 2011; Gui et al., 2011 )
Deflection in IP space due to interaction with solar wind (e.g., Wang et al., 2002, 2004, 2006, 2014; Lugaz et al., 2010; Isavnin et al., 2013)
Deflection due to CME-CME collision/interaction (e.g., Wang et al., 2011; Lugaz et al., 2012; Shen et al., 2012)
Model for the CME Deflection in IP Space (DIPS, Wang Y. et al., 2004, 2014)
Available at http://space.ustc.edu.cn/dreams/dips, also available at CCMC
Integrated CME Arrival Forecasting (iCAF) System
• Completely automated (See poster P-07 by B. Zhuang et al. for iCAF)
Coronagraph images
Projected 2D parameters:Position angle, speed, width
CME detection
Cone model
DIPS model
3D parameters:direction, speed, width
Trajectory: CME arrival prediction
Solar wind speed
Tested at Space Environment Prediction Center (SEPC)
of National Space Science Center (NSSC), Chinese Academy of China (CAS)
Performance of iCAF: Preliminary statistics
Test prediction of CME arrival
• Sample: 37 full halo CMEs (38% missing the Earth)
• Prediction: 81% correct, 19% false
CME scoreboard @ CCMC
• 2015 August 14
CME did not hit
the Earth
iCAF
In-situ Obs.Y N
Y 20 3
N 4 10
Predicted Shock Arrival Time
Confidence (%)
Method
08-18T12:00Z (-7.0h, +7.0h)
10.0 WSA-ENLIL + Cone (GSFC SWRC)
08-18T05:00Z----
WSA-ENLIL + Cone (NOAA/SWPC)
08-19T12:00Z (-12.0h, +12.0h)
20.0 Other (SIDC)
08-18T18:00Z (-12.0h, +8.0h)
40.0 WSA-ENLIL + Cone (Met Office)
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