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)