Coronal Mass Ejections: from the Sun to the Earth

Coronal Mass Ejections: from the Sun to the Earth

Consuelo CidSpace Research Group-Space Weather

University of Alcala

Interdisciplinary Workshop on Plasma Physics, Madrid (Spain), June 6-7 2011

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Monthly Notices of the Royal Astronomical Society, Vol. 20, November 11, 1859

Interdisciplinary Workshop on Plasma Physics, Madrid (Spain), June 6-7 2011

3

Magnetic Observations at Kew

Two responses seen in the new photographic recordings of magnetic variations being made at Kew (London)• Prompt response (due to X-rays increasing ionospheric ionization)• Great Magnetic Storm begins 18 hours later (due to associated emission reaching Earth)

Interdisciplinary Workshop on Plasma Physics, Madrid (Spain), June 6-7 2011 4

Solar mass ejections• Unmagnetized material

(Lindenmann, 1919)• A plasma cloud including

frozen-in magnetic field loops• Plasma including turbulent

magnetic fields• A “tongue” of magnetic field

loops rooted at the Sun• A disconnected “plasmoid” or

“bubble”• Shock wave ahead of a region

of enhanced turbulence ….• Flux rope (Burlaga, 1988)


CMES AT THE SUNCoronal Mass Ejections: from the Sun to the Earth


The first CME observed in 1860?

This early observation was not confirmed convincingly. However...


The first CMEs observed in modern times: OSO 7 (1971) and Skylab (1973)

...the similarity with Skylab images obtained 113 years later is striking!


This was the first published

‘modern‘ CME event,

observed 1971 from OSO 7


CME? ...can’t tell what it is, but if I see it I know it...

What, actually, is a CME?Definition of terms: “A coronal mass ejection (CME) is … an observable change in coronal

structure that 1) occurs on a time scale of a few minutes and several hours and 2) involves the appearance (and outward motion) of a new, discrete, bright, white-light feature in the coronagraph field of view." (Hundhausen et al., 1984)

This definition is very fortunate in that• it emphasizes the observational aspect,• it stresses the transient event character,• it does not infer an interpretation of the "feature" and its potential origin,• in particular, it does NOT infer any conjunction with "coronal mass", • it restricts the applicability of the term to the Sun's proximity


Just an example of what a CME is


Some CMEs are spectacular, indeed!


Properties of CMEs


A unique observation by LASCO-C2.Note the helical structure of the prominence and filaments!


The most popular astronomical picture in history: a huge prominence seen in the He+ line (30.4 nm), from Skylab (1973)

From that time in 1973 on, CMEs were an issue!


The helical structure could just disappear because of 2D-projection on the plane of sky


Full halo CMEs: ejections towards or away the Earth


X-Ray or EUV images show coronal loops anchored in the photosfere


Reconnection and CMEs

• Above CME• Release mechanism in

“breakout” model • Fast CMEs

• Below CME• Release mechanism in

“emerging flux” model• Slow CMEs


Hight helicity: one of the clues for the “emerging flux” model


Checking the “breakout model”: dimming at solar disk


CMEs AT INTERPLANETARY MEDIUMCoronal Mass Ejections: from the Sun to the Earth


Solar wind …and solar wind transients

http://umbra.nascom.nasa.gov/istp/larson-1.gif


ICME signatures in solar wind


The first ‘magnetic cloud’Burlaga et al., 1991

… and the topology proposed


Note the 180º rotation of the

magnetic field direction through

the cloud!

Minimum Variance Analysis


Are all ICME MCs?...

…the answer is still on debate

Today: Magnetic cloud = flux rope


From 1D to 3D

… well, just 2D+1/2 D


Force-free model (Burlaga, 98)

a=cte Lundquist (1950)

BB

a

0 0

0 1

( )( )

0

axial

azth

r

B B J rB B HJ rB

aa

ar

0

B0

Baz

Beje

2.4 0

Boundary: Baxial=0 aR=2.4


http://umbra.nascom.nasa.gov/istp/lepping-5.gif

http://umbra.nascom.nasa.gov/istp/lepping-9.gif


MCs expand!Force-free?


First non-force free MC modelPlasma and magnetic field inside magnetic clouds: a global study (Cid et al., 2001)

• The starting point:(0, , ), with , cte

0y y

r

j j j j r j

B a

• Analytical expressions:

2 20

2yB R r

a

0

2 yB j r

0rB

022224

20

24Pr jRrP

aa


XGSE

YGSE

ZGSEXGSE

ZGSE

YGSE

y0

90ºq

f


The model reproduced properly experimental data…


.. but not for all MCs. Elliptical MCs

Elliptical cross-section model for the magnetic topology of magnetic clouds (Hidalgo, Nieves-Chinchilla and Cid, 2002)

It fits well... but many parameters need to be controlled


Reconstruction of the cross section using Grad-Safranov equation

But MC boundaries are

difficult to be established


Numerical simulations


From the Sun to L1

• Experimental data and models do not agree systematicaly: only a few cases have been reproduced nowadays

• Where is the problem to be solved?…In the magnetic topology?…In the propagation through the solar wind?

… more work needed!

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The problem is still harder!

Complex ejecta,

multiMC…


CMEs AT TERRESTRIAL ENVIRONMENT

Coronal Mass Ejections: from the Sun to the Earth


At solar wind (L1)

At the terrestrial surface


day of November 2003

1 6 11 16 21 26 31

Dst

(nT)

-500

-400

-300

-200

-100

0

100


Energy injected from solar wind (Dungey, 1961): proportional to convective electric field (Ey=VBz)

ICMEs present large

values of V and B z


* *( )dDst DstQ tdt

( ) 5.4t

Dst Q t dt Ey t

DPS relation: The decrease of the horizontal component of the geomagnetic field is proportional to the energy content of the ring current

From the energy balance in the ring current, it is possible to get the Dst index as a function of time

Neglecting losses (main phase):

Theoretical scenario


t (h)

0 5 10 15 20 25 30

Ey (m

V/m

)

0

200

400

600

800

1000

I (nT

)

-400

-300

-200

-100

0

t (h)

0 5 10 15 20 25 30

(B z

) (nT

)

0

5

10

15

20

25

Cumulated Ey is not enought to explain the terrestrial disturbance for small t

… but theoretical expectations do not fit properly experimental data

Soon appearing in GRL…

Bz standard deviation is large for those events

BE v B

t

Both, E convective and B/t, are related to the appearance of an induced E

Ey

Our results agree with Faraday law!


The phenomena are complicated and without limit as we look to finer and finer detail. It is not our goal to pursue the endless detail; instead, we are interested in understanding what we observe in terms of the basic laws of physics. We want to know how the observed effects follow from Newton, Maxwell, Lorentz, Schorödinger, etc. We construct idealized and simplified theoretical models for the purpose of demonstrating how the basic laws of physics lead to a certain observed effect. We pursue detail only insofar as it leads to novel effects, in which the basic laws of physics interact in some new and hitherto unknown combination.”

Eugene N. Parker

Coronal Mass Ejections: from the Sun to the Earth

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