Looking for the CME Onset:

A 10 Year CDS Campaign

Richard Harrison, Rutherford Appleton Laboratory

• An example of a long-term CDS campaign

• An excuse to indulge in a bit of CDS history

OSO/Skylab – first CME observations did hint that there was NOT a one to one relationship.

SMM investigations from 1982 showed more inconsistencies - first real opportunity to explore flare-CME relationship with reasonable daily planning, resolutions, co-pointed instruments etc… Seemed straightforward enough, but opened a can or worms!!

SMM CME Onset Campaign

Using today’s images…

We are asking a very basic question. How do we relate one of these…

… to one of these? What is the relationship between the two major solar active phenomena?

Basic stuff! If CME is corona ‘blast’ from flare then:

Flare would sit under core of CME;

Onset of flare & CME launch would coincide;

Scale of flare & CME would be consistent;

Would expect near one to one flare-CME occurrence.

The flare-CME relationship

Didn’t turn out to be that simple…

There is a strong association between flares and CMEs – but not a one to one association;

The onset of a CME associated with a flare appears to occur at any time within several tens of minutes of the flare onset;

The scale sizes of CMEs and flares are very different (~45o and <10o, respectively). Since the footpoints of CMEs do not expand outward, this suggests that the flare site is too small – unless there is very early expansion;

The flare tends to lie within the span of the CME and may often lie to one side;

The CME source region is commonly much larger than an active region or flare, though it frequently encompasses an active region.

The flare-CME relationship - Pre-SOHO conclusions

“The flare and CME are both consequences of the same magnetic ‘disease’. They do not cause one another but are

closely related. Their characteristics are the results of local conditions, and thus we may witness a spectrum of flare and

CME properties which are apparently unrelated, even resulting in events without the flare or CME component.”

The flare-CME relationship - Pre-SOHO conclusions

Understanding the CME onset and the flare-CME relationship are critical for understanding the impact of solar activity on the Earth and of processes such as mass acceleration and reconnection, which are fundamental stellar processes. An ideal candidate for the new SOHO mission.

The flare-CME relationship

Enter SOHO….

December 1984 – ‘European Space Science Horizon 2000’

“… cornerstone consisting of two projects, an observatory at the L1 point and a multipoint space plasma physics mission.”

Solar and Heliospheric Observatory

The most sophisticated solar observatory ever built!

- ESA Cornerstone mission (with NASA)

- launched (Atlas rocket) - 2 Dec 1995

- 12 instruments to study:• solar interior• solar atmosphere• solar wind

- UK involvement: CDS, part of LASCO and scientific involvement in most of payload.

- 1.85 tonnes, 3-axis stabilized, Sun-pointed

Enter SOHO….

Orbit of Sun-Earth L1 Lagrangian point - 1.5 million km Sunward of the Earth - 1/100th of the way to Sun

• constant view of Sun - no eclipses

• no ‘contamination’ due to Earth environment

• sunward sentinel

Enter SOHO….

Enter CDS….

The CDS heritage at RAL:

- Alan Gabriel

- Bruce Patchett

- CHASE and MSSL

CDS Operations EJECT studies started in mid-1996, to be repeated many, many times over coming years – mainly as JOP67:

- Mosaic of three 4 arcmin fields

- 10 s exposures

- 4x240 arcsec slit (60 locations)

- Cadence 50 min(!)

- Six emission lines:

He I 584 Å (20,000 K)

O V 629 Å (250,000 K)

Mg IX 368 Å (1 million K)

Fe XVI 360 Å (2 million K)

Si X 347/356 Å (1.3 million K)

- Play off between cadence and plasma diagnostic tools! BUT, first real opportunity to obtain plasma diagnostics of CME source?

CDS Operations

CME Onsets

12:13 UT 13:03 UT 13:53 UT 14:43 UT 15:33 UT

The Events of September 23, 2001

2 million K Fe XVI 360 Å line

The flare-CME relationship – Sept 23 2001

12:13 UT 13:03 UT 13:53 UT 14:43 UT 15:33 UT

1 million K Mg IX 368 Å line

The flare-CME relationship – Sept 23 2001

The flare-CME relationship – July 25 1999

13:54 UT 14:06 UT 15:54 UT

The flare-CME relationship – July 25 1999

13:54 UT

- Pre-flare ascending loops

- Coronal dimming

- Pre-flare CME onset

- CME source larger than flare

The flare-CME relationship – July 25 1999

CME Onsets

Date Dimming mass CME Mass(DEM/Si X) [kg] [kg]

Jul 16 1997 4.3x1010/1.3x1011 5x1010

May 8 1999 1.1x1012/4.2x1012 3x1011

Jul 25 1999 7.4x1011/3.4x1012 3.5x1012

Feb 19 2000 1.1x1014/2.7x1014 1.1x1012

Aug 19 2000 6.4x1011/1.8x1012 4.7x1011

Onset of dimming and CME ‘coincident’. Location of dimming under ascending CME.

- Unique method for identification of CME source material.- Plasma diagnostic analyses of the source providing information on onset process.

The flare-CME relationship – Dimming Mass

CME Onsets

The flare-CME relationship – Dimming

• CME Onset Studies, Harrison, R.A., 1997, ESA SP-404 (proc. 5th SOHO Workshop), 85.

• A spectroscopic study of coronal dimming associated with a coronal mass ejection, Harrison, R.A. and Lyons, M., 2000, Astron. Astrophys. 358, 1097.

• Coronal Dimming and the Coronal Mass Ejection Onset, Harrison, R.A., Bryans, P., Simnett, G.M. and Lyons, M., 2003, Astron. Astrophys. 400, 1071.

• SOHO Observations Relating to the Association Between Flares and Coronal Mass Ejections, Harrison, R.A., 2003, Adv. Space Res. 32, No. 12, 2425.

• On the Coronal Mass Ejection Onset and Coronal Dimming, Howard, T.A. and Harrison, R.A., 2004, Solar Phys. 219, 315-342.

• CME-related dimming first seen using Skylab, also seen with Yohkoh as well as EIT and CDS – but only CDS has addressed this with detailed spectral analysis.

• Many studies identify patches of dimming within active regions - how does that relate to a 45 degree CME? The scale ‘problem’ must be addressed. Is there also a line-of-sight problem?

• If the dimming region identifies the critical low coronal source region then we can analyse the source plasma in the lead up to onset. We can also explore the possibilities of early CME prediction or on-disk CME prediction.

The flare-CME relationship – Dimming Mass

CME Prediction?

Can we predict a CME onset utilising an algorithm based on the number of pixels which show declining intensity in selected emission lines?

If we can do this successfully on the limb, we can do it on the disk.

Basic scheme scan Mg IX and Fe XVI EJECT mosaics from 1996 to date (several hundred) using automated procedure.

For each, if contiguous set of pixels (predefined minimum number) shows decrease in intensity beyond specified limit, define a CME alarm.

Compare CME alarms with LASCO event lists.

CME Prediction?

Preliminary results for 100 EJECT runs (1999-2003) –

Ω = CME alarm parameter (defined by number of contiguous pixels decreasing in intensity beyond specified limit)

• 47 CMEs in periods covered - BUT some will be from behind limb

• Even some behind limb will be seen as coronal depletion, so expect >50%.

• Thus, if we are catching over 50% of the CMEs, we are doing well.

• Need balance between false alarms (as low as possible) & fraction predicted.

CME Prediction?

Preliminary results for 100 EJECT runs (1999-2003) –

What if it was random?? • 47 CMEs in period. • 100 runs - equal chance YES/NO, would get 50 alarms. • Of 47 events, equal chance of alarm, expect to ‘catch’ 24. HIT RATE – successful prediction/total alarmsFALSE HIT RATE – false alarms/total alarms

  No. alarms

CME predicted

False alarms

CMEs not predicted

HIT RATE

FALSE HIT RATE

Fraction CMEs predicted

Fraction CMEs not predicted

Random Case

50 24 26 23 48% 52% 50% 50%

Ω > 0.25 23 18 5 29 78% 22% 38% 62%

Ω > 0.2 37 27 10 20 73% 27% 57% 43%

Ω > 0.15 54 37 17 10 69% 31% 79% 21%

CME Prediction?

Preliminary results for 100 EJECT runs (1999-2003) –  No.

alarmsCME predicted

False alarms

CMEs not predicted

HIT RATE

FALSE HIT RATE

Fraction CMEs predicted

Fraction CMEs not predicted

Random Case

50 24 26 23 48% 52% 50% 50%

Ω > 0.25 23 18 5 29 78% 22% 38% 62%

Ω > 0.2 37 27 10 20 73% 27% 57% 43%

Ω > 0.15 54 37 17 10 69% 31% 79% 21%

• Want high hit rate and low false hit rate – but note that some over the limb events you cannot see – but also few missed CMEs. What is OK? (>75%, <20%, <30% from limb obs.??)

• Need to do considerably better than random case!

• Is it better to predict few, but with confidence – i.e. issue less alarms but be sure that they achieve, say, better than 75% success, knowing you will miss some?

STEREO – Twin spacecraft out of the Sun-Earth line

Two NASA spacecraft, orbiting the Sun – one leading the Earth, one following, providing two views of the Sun and the space between the Sun and Earth. Due for launch in 2006.

First 3D views of a star

First views of solar ejected clouds impacting the Earth

UK involvement: (i) Novel CCD camera systems on all remote sensing systems aboard the spacecraft; (ii) Leadership of the unique Heliospheric Imager instrument, a wide-angle telescope system, to image solar clouds in interplanetary space

Future Missions for CME Research?

SDO – The Solar Dynamics ObservatoryNASA’s flagship of the Living with a Star programme – a large Earth-orbiting high-resolution solar observatory. Due for launch in 2008.

High-resolution imaging, helioseismology and magnetic mapping of the Sun, will allow detailed understanding of the complex solar atmosphere and its magnetic fields.

UK involvement: CCD camera systems, developed from the STEREO programme, are incorporated in the US-led instrument package.

Future Missions for CME Research?

Conclusions?

CDS has allowed a spectroscopic dimension which has enabled significant advances in understanding the dimming phenomenon – and is well suited to determining prediction algorithms… Next steps?

- Analysis of plasma prior to dimming (having identified the source?)

- Completion of dimming ‘alarm’

- SOHO, STEREO, Solar-B, SDO

Watch this space!