interplanetary coronal mass ejections from messenger...

Interplanetary Coronal Mass Ejections from MESSENGER Orbital Observations at MercuryReka M. Winslow1, Noé Lugaz1 , Lydia C. Philpott2 , Nathan A. Schwadron1 , Charles J. Farrugia1 , Brian J. Anderson3, and Charles W. Smith1

(1) Institute for the Study of Earth, Oceans, and Space, University of New Hampshire ([email protected]), (2) Earth, Ocean and Atmospheric Sciences, University of British Columbia, (3) John Hopkins University Applied Physics Laboratory.

Poster based on: Winslow, R. M. et al. (2015), Interplanetary coronal mass ejections from MESSENGER orbital observations at Mercury, J. Geophys. Res. Space Physics, 120, doi:10.1002/2015JA021200.

SH53A-2469AGU Fall Meeting 2015

1. Summary

• Used observations from MESSENGER in orbit around Mercury to study interplanetary coronal mass ejections (ICMEs) near 0.3 AU.

• Cataloged over 60 ICMEs at Mercury between 2011 - 2014.

• Investigated key ICME property changes from Mercury to 1 AU.

Find: • Good agreement with previous studies for magnetic field strength dependence on dis-tance, and evidence that ICME deceleration con-tinues past the orbit of Mercury.

• This ICME database useful for multipoint spacecraft studies of recent ICMEs, as well as for model validation of ICME properties.

2. ICME Identification

• ICMEs identified using magnetic field measure-ments only, due to lack of solar wind data with MES-SENGER.

• Strict selection criteria: a) interplanetary shock observedb) shock followed by sheath and magnetic ejectac) event lasted for the duration of at least 1 MES-SENGER orbit through Mercury’s magnetosphered) event caused a visible distortion of the magneto-sphere

• Selection criteria biases towards fast ICMEs that are shock-driving and ICMEs with magnetic cloud-like characteristics.

• Also determined corresponding CME counter-part at the Sun for each event.Example ICME:

3. ICME Properties at Mercury

• ICME speed estimated from CME ejection time at the Sun, arrival time at Mercury, and Mercury’s heliocentric distance. -> This average speed is likely a maximum speed of the ICME at MESSENGER.

• Maximum ICME |B| observed is 310 nT.

• Fastest transit time from Sun to Mercury was 6 hr, longest transit time 52 hr.

• Fastest transit speed 2350 km/s, slowest transit speed 325 km/s.

• Large spread in transit times and speeds indicates that due to proximity to Sun, MESSENGER observed a wide range of ICMEs, even ones that maybe too slow or small to be detected at 1 AU.

4. Differences in ICME Properties Between Mercury and 1 AU

• Used existing databases of ICMEs at 1 AU for the same time period.

Main Results: , in good agreement with previous studies.

• ICME deceleration continues beyond the orbit of Mercury: (1) Shallow speed decrease with distance, (2) Average transit time from Sun to Mercury 20% faster than expected based on average transit times to 1 AU, (3) Significantly shallower ICME transit time dependence on initial CME speed observed at 1 AU compared to predictions based on MESSENGER ICME catalog.

• ICME magnetic shock compression ratio higher at MESSENGER (1.97) than at STEREO (1.64). ICME deceleration may explain the lower mean shock compression at 1 AU compared to that at Mercury.

5. Example ICME: 12 July 2012 Event

• Observed by MESSENGER and ACE

• Illustrates that this ICME database can be used for both model validation and propagation studies of events observed in conjunction.

• Some of the large-scale structure is retained in propagation (B

R stongly negative at both distances)

• Non-dimensional expansion rate of the cloud con-firmed by two separate methods at Mercury and ACE to be:

• Compare to model predictions of Hess & Zhang [2014] for this event, which fit remote-sensing ob-servation a posteriori to the semi-empirical drag model of Vrsnak et al. [2013].

• Model does quite well at estimating sheath size and arrival time at Mercury:

0 50 100 150 200 250 3000

5

10

15

Max |B| in ME (nT)

No. o

f ICM

Es

Mean = 86.2±5.0

0 50 100 150 200 250 300 3500

5

10

15

Max |B| in Sheath (nT)

No. o

f ICM

Es

Mean = 84.6±5.8

0 10 20 30 40 50 600

5

10

15

Shock transit time (hours)

No. o

f ICM

Es

Mean = 23.0±1.1

0 10 20 30 40 50 600

5

10

15

ME transit time (hours)

No. o

f ICM

Es

Mean = 25.6±1.2

0 500 1000 1500 2000 25000

5

10

15

Shock Transit Speed (km/s)

No. o

f ICM

Es

Mean = 792±45

0 500 1000 1500 2000 25000

5

10

15

ME Transit Speed (km/s)

No. o

f ICM

Es

Mean = 706±41

0 0.2 0.4 0.6 0.80

5

10

15

ME radial size (AU)

No. o

f ICM

Es

Mean = 0.223±0.018

0 0.05 0.1 0.15 0.20

5

10

15

Sheath radial size (AU)

No. o

f ICM

Es

Mean = 0.0434±0.0036

a) b)

0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1 1.10

50

100

150

200

250

300

Heliocentric Distance (AU)

ME

Mean |B

(n

T)

|

MESSENGER+ACE data

<B> = 10.9 r−1.85

; Gulisano et al. (2010)

<B> = 18.1 r−1.64

; Leitner et al. (2007)

<B> = 8.3 r−1.52

; Wang et al. (2005)

<B> = e(2.01+/−0.15)

r(−1.95+/−0.19)

0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1 1.10

50

100

150

200

250

300M

E m

axim

um

|B

| (n

T)

MESSENGER+STEREO data

Bmax = e(2.5+/−0.06)

r(−1.89+/−0.14)

Bmax = 17.7 r−1.73

; Farrugia et al. (2005)


0 500 1000 1500 2000 25000

50

100

150

200

250

300

350

Shock transit speed (km/s)

Maxim

um

|B

| in

the IC

ME

(nT

)

MESSENGER data;

|B| = 0.03 v + 59.5

cc = 0.55

0.2 0.4 0.6 0.8 10

500

1000

1500

2000

2500

Ma

xim

um

Sh

ock S

pe

ed

(km

/s)


MESSENGER+ACE data

|v| = e(6.14+/−0.05)

r(−0.45+/−0.09)

0.2 0.4 0.6 0.8 10

500

1000

1500

2000

2500

Ma

xim

um

ME

Sp

ee

d (

km

/s)

MESSENGER+STEREO data

|v| = e(6.18+/−0.04)

r(−0.26+/−0.08)

a) b)


0 500 1000 1500 2000 25000

25

50

75

100

125

150

Coronal Speed (km/s)

ME

Tra

nsit T

ime

(h

rs)

Sun to Mercury

Predicted Sun to 1 AU

TT = e(9.37+/−0.79)

v(−0.78+/−0.12)

TT = e(7.92+/−1.2)

v(−0.71+/−0.17)

a) b)

0 500 1000 1500 2000 25000

25

50

75

100

125

150

Coronal Speed (km/s)

Shock T

ransit T

ime (

hrs

)

Sun to Mercury

Predicted Sun to 1 AU

TT = 441 v−0.29

; Vrsnak & Zic (2007)

TT = e(9.08+/−0.83)

v(−0.76+/−0.12)

TT = e(7.75+/−1.2)

v(−0.704+/−0.17)

0 5 10 15 20 25 30 35 40 45 500

25

50

75

100

125

150

175

200

225

Transit time (hours)

Rad

ial d

ista

nce

(RS

un)

Shock drag model − Hess & Zhang (2014)Ejecta drag model − Hess & Zhang (2014)MESSENGER shock transit timeMESSENGER ejecta transit time

0 5 10 15 20 25 30 35 40 45 500

5

10

15

20

25

30

35

40

45

50

Transit time (hours)

Sta

ndof

f dis

tanc

e (R

Sun

)

Drag model − Hess & Zhang (2014)MESSENGER standoff distance

a) b)

High ICME |B| -> high ICME speed?

UTC12/30 16:48 12/30 19:12 12/30 21:36 12/31 00:00 12/31 02:24 12/31 04:48 12/31 07:12

B Tota

l (nT)

01530456075

UTC12/30 16:48 12/30 19:12 12/30 21:36 12/31 00:00 12/31 02:24 12/31 04:48 12/31 07:12

B R (nT)

-75-50-25

0255075

UTC12/30 16:48 12/30 19:12 12/30 21:36 12/31 00:00 12/31 02:24 12/31 04:48 12/31 07:12

B T (nT)

-75-50-25

0255075

UTC12/30 16:48 12/30 19:12 12/30 21:36 12/31 00:00 12/31 02:24 12/31 04:48 12/31 07:12 12/31 09:36

B N (nT)

-75-50-25

0255075

1012

1011

1010 H+ (

Scan

Tot

al)

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