1. Corona Mass Ejection (CME) Solar Energetic Particle Events
CSI /PHYS Solar Atmosphere Fall 2004
Lecture Dec. 01, 2004
Corona Mass Ejection (CME)
And
Solar Energetic Particle Events

2. A Typical Coronagraph Image: Streamers

3. Streamer (cont’d)
A streamer is a stable large-scale structure in the white-light corona.
It has an appearance of extending away from the Sun along the radial direction
It is often associated with active regions and filaments/filament channels underneath.
It overlies the magnetic inversion line in the solar photospheric magnetic fields.
When a CME occurs underneath a streamer, the associated streamer will be blown away
When a CME occurs nearby a streamer, the streamer may be disturbed, but not necessarily disrupted.

4. CME: a transient phenomenon
A LASCO C2 movie, showing multiple CMEs

5. Measuring a CME H (height, Rs) PA (position angle) AW (angular width)
M (mass)

6. Measuring a CME (cont’d)
A typical measurement:
# HEIGHT DATE TIME ANGLE TEL FC COL ROW
/01/03 11:30: C
/01/03 11:54: C
/01/03 12:06: C
/01/03 12:30: C
/01/03 12:54: C
/01/03 13:31: C
/01/03 13:42: C
/01/03 13:54: C
/01/03 14:06: C
/01/03 14:18: C
/01/03 14:42: C
/01/03 15:18: C
/01/03 15:42: C
/01/03 16:18: C
/01/03 16:42: C
/01/03 17:18: C

7. CME Property: velocity
Velocity is derived from a series of CME H-T (height-time) measurement
A CME usually has a near-constant speed in the outer corona (e.g, > 2.0 Rs in C2/C3 field)
Note: such measured velocity is the projected velocity on the plane of the sky; it is not the real velocity in the 3-D space.

8. CME Property: velocity
CME velocity ranges from
50 km/s to 3000 km/s
Average velocity: 400 km/s
Peak velocity: km/s
Median velocity: km/s
6300 LASCO CMEs from 1996 to 2002

9. CME Property: size
AW = 80 degree AW = 360 degree, halo CME

10. CME Property: size Broad distribution of CME apparent angular width
Average width 50 degree
A number of halo CMEs (AW=360 degree), or partial halo CMEs (AW > 120 degree)
Halo CMEs are those likely impacting the Earth orbit

11. CME Property: mass CME mass distribution from 1013 to 1016 gram
Average CME mass about 1015 gram
Based on
2449 LASCO CMEs
From 1996 to 2000

12. CME Morphology

13. CME morphology (cont’d)
Three part CME structure
A bright frontal loop (or leading edge)
Pile-up of surrounding plasma in the front
A dark cavity (surrounded by the frontal loop)
possibly expanding flux rope or filament channel
A bright core (within the cavity)
Composed of densely filament remnant material

14. CMEs and Other Solar Activities
CMEs are often associated with flares; extremely fast CMEs (2000 km/s) are mostly associated with major flares (X class).
CMEs are also associated with filament eruptions.
CME are often associated with coronal dimmings
However, there are always exceptions in each type of association.

15. CMEs and Other Solar Activities (cont’d)
Exp. A CME associated with a flare

16. CMEs and Other Solar Activities (cont’d)
Exp. A CME associated with a filament
EIT movie of 2000/02/27 showing
filament eruption
C2 movie of 2000/02/27 CME

17. CMEs and Other Solar Activities (cont’d)
Exp. A CME associated with a (EIT) coronal dimming
Coronal dimming, often seen in EIT 195 Å images (1.5 MK), is caused by mass depletion following CME eruption

18. kinematic Evolution of a CME
A CME is strongly accelerated in the inner corona (<2 Rs); unfortunately, inner corona observations have been very poor.
A CME maintains a more or less constant speed when it travels in the outer corona (>2 Rs); it interacts with background solar wind in the interplanetary space.

19. Geo-effective CMEs: halo CMEs
Whether a CME is able to intercept the Earth depends on its propagation direction in the heliosphere.
A halo CME (360 degree of angular width) is likely to have a component moving along the Sun-Earth connection line
A halo is a projection effect; it happens when a CME is initiated close to the disk center and thus moves along the Sun-Earth connection line.
Therefore, a halo CME is possibly geo-effective.
2000/07/14 C2
EIT

20. CME models A model shall include many observational elements CME front
cavity
core
Flare
X-ray loop
EUV loop arcade
Hα flare ribbon
Magnetic reconnection
Current sheet
Reconnection inflow
Some Others
filament eruption
coronal dimming
timing relation
Energetic relation

21. Lin’s CME eruption model: MHD analytic solution
CME models (cont’d)
Lin’s CME eruption model: MHD analytic solution

22. Antiocs’s CME eruption model: MHD numeric solution
CME models (cont’d)
Antiocs’s CME eruption model: MHD numeric solution

23. Solar Energetic Particle (SEP) Events
SEP hit LASCO CCD, causing degrading of images.

24. Solar Energetic Particle (SEP) Events
Proton flux measured in-situ (at Geo-stationary orbit) by GOES satellite
SEP onset: 2001/11/04 17:00 UT, proton flux increases by 5 order of magnitude

25. Solar Energetic Particle (SEP) Events
Flare onset time: 2001/11/04 16:03 UT
CME onset time: 2001/11/04 16:35 UT
SEP onset time: /11/04 17:00 UT
Time delay from the Sun to the Earth is in the order of ten minute
SEP travels at near-relativistic speed

26. SEP Events SEP events are increases of energy particles.
They are observed in the near earth space environment, outside the magnetosphere and in the earth polar caps
They are also observed everywhere in the interplanetary medium.

27. SEP Events Impulsive Event Gradual Event
Observed by ACE/EPAM and IMP-8/CPME

28. SEP Events Two kinds: gradual and impulsive events Impulsive events
Impulsive short-duration events of hours
Relatively small proton flux
Mainly associated with flares, but not CMEs
From a narrow helio-longitude (~30 degree in western hemisphere), where magnetic field lines are well connected with the Earth
Gradual events
Have a duration of several days
Large proton flux
Associated with CMEs.
From a broad range of helio-longitudes (180 degree)

29. Particle Acceleration Mechanisms
SEP events are caused by flares and/or CMEs
Flare mechanisms
SEP caused by magnetic reconnection
Wave-particle resonance in flaring region
Direct electric field induced by reconnection
Source of impulsive SEP events
CME mechanism
SEP caused by CME-driven shock
Shock forms at the front if CME speed exceeds local Alfven speed
Shock waves can accelerate particles through by bouncing particles back and forth across the shock front gaining speed with each bounce
Source of gradual SEP events