# Presentation: 862795

## The Geometric Localization

**of STEREO CMEs**
**GRL Vol. 31, No. 21, L21802, Nov 2004**
**V.J. Pizzo and D.A. Biesecker**
**NOAA Space Environment Center**

## Geometric Localization Technique

- What ‘Geometric Localization’ (GL) does
- Given observations of any structure from 2 different places
- at the same time if a transient structure
- It works on ‘any’ structure for which an ‘edge’ is visible
*GL defines a volume which circumscribes that structure*

## WHY Concentrate upon CMEs?

-  currently use single observatory (halo/non-halo)
-  Estimate – if Earth impact; when; how strong?

**WHY Concentrate upon CMEs?**

-  STEREO can improve this
-  Vastly improved estimate of Earth-directed CME properties  geomagnetic disturbances
-  Improved knowledge of coronal and interplanetary structures along E/S line

## Geometric Localization Technique

- How will this be implemented for STEREO?
- Start by simulating STEREO data
- 2 views of CME’s don’t yet exist
- We generate CME model
- Parameterized coronal background and transient
- Apply our ‘geometric’ technique
- Results in a set of stacked quadrilaterals that bound the CME
- Compare results to input model

## STEREO Beacon Data

- 24/7 real-time beacon data
- See Biesecker and Webb poster SH21B-0412
- Low-cadence, low resolution
- in-situ
- imaging
- 5-minute latency
- SECCHI/COR2 images
- 4x per hour
- 1/8 resolution (256x256 pixels ~ 120”)

## Schematic of ‘Geometric Localization’ Technique

- Need location of 2 spacecraft
- Defines a plane
- Need location of ‘edges’ of CME
- Defines a quadrilateral circumscribing CME

## Applying the technique

- Mark one edge – LA1
- s/c – s/c – Sun plane: defines a line
- Mark LA2; and then in other s/c image mark LB1 & LB2
- Choose a succession of starting points – thin slices

*e.g. *STEREO Leading +35°

*e.g. *STEREO Lagging -35°

## The Resulting Localization

- Comparison of localization model to input CME
- 3 perspectives
- Geometric Localization circumscribes input CME

## How well does it work?

- One measure of error
- Ratio of area determined by GL to area of input CME ~ *f(**Χ**)*
- Quantifiable – critical for forecasters
- Ideal separation 90°
- Two years into mission
- Reasonable uncertainty (<50%)
- Year 1 to Year 3

- 	Comparing area of cross-section of model to cross-section of CME

## Planned additional work

- Explore much broader range of examples
- Vary CME shape, density distribution
- Making it an operational product
- Improve/refine error analysis
- Automated CME detection & edge detection
- Apply to successive SECCHI COR2 images
- Location, extent, velocity
- If CME will arrive and when
- How much of the CME Earth will see (strength and duration)
- Streamline and document software
- Relate to polarization analysis (Moran and Davila 2004; Dere *et al*.)
- GL removes plane of sky ambiguity
- Polarization analysis provides info. on internal structural

## Science/understanding
 Major boost to correlation studies
 Improved understanding of response of
		interplanetary environment to solar drivers
 Input/boundary condition for other 3-d
		techniques

-  Major boost to correlation studies
-  Improved understanding of response of
- 		interplanetary environment to solar drivers
-  Input/boundary condition for other 3-d
- 		techniques

- Additional work - continued

## Summary

- Geometric localization provides a ‘simple to use’ technique
- Potential for automation
- Application to CME’s aids in forecasting geomagnetic storms
- From length of cut through CME on Sun-Earth line
- Improved prediction of if/when CME will hit Earth
- Information on storm strength/duration
- Quantifiable error estimates
- Adding a 3rd view helps significantly (*e.g. *SOHO/LASCO)
- Implementation in time for start of STEREO mission expected
- Therefore, ideal for forecasting!
- Useful for collaborative scientific investigation
*e.g.* Polarization Analysis

## Backup slides

## Polarization Analysis

- On a pixel by pixel basis – finds C.O.M. along a line of sight
- Collapses a 3-d structure into ~2.5-d
- Gives spatial information

## Polarization Analysis +Geometric Localization

- Polarization Analysis and Geometric Localization are complementary
- Geometric Localization resolves plane-of-sky ambiguities inherent in polarization analysis
- Polarization analysis can provide more  information about CME structure (*i.e.* mass distribution)

## Slide 16

## Slide 17

## SOHO/LASCO CMEs