# Presentation: 134390

## In Situ Observations of CMES in the Heliosphere

*Focusing STEREO vision on internal and contextual HCME complexity *

## Large-scale field rotation
Strong magnetic field
Temperature depression
Low magnetic field variance
Cosmic ray depression
Mismatched sector boundary signatures
Charge state and composition anomalies
Counterstreaming suprathermal electrons

- Strong magnetic field
- Temperature depression
- Low magnetic field variance
- Cosmic ray depression
- Mismatched sector boundary signatures
- Charge state and composition anomalies
- Counterstreaming suprathermal electrons

- Internal complexity:  Variability of HCME signatures

*Magnetic cloud*

- New!

- [e.g., *Gosling*, 1990; *Neugebauer and Goldstein*, 1997]

## Variability in counter-streaming electrons

- Each line represents one magnetic cloud
- Shaded bars indicate intervals of closed fields
- Clouds range from completely open to completely closed

*Shodhan et al.* [1999]

## “Plum Pudding” by Bame et al. [1979] remains appropriate

- “Plum Pudding” by Bame et al. [1979] remains appropriate

**LUMPY DISTRIBUTION OF HELIUM ENRICHED PLASMA** [Cf. *Lepri et al. *and *Zurbuchen et al.,* 2001]

## STEREO vision* focused on internal complexity can help determine

- shapes of
- charge-state and composition regimes
- magnetically open and closed regions
- solar counterparts to HCME types
- e.g., do magnetic clouds correspond to CMEs with 3-part structure?

- *two-point in situ measurements
-    combined with heliospheric imaging

## Contextual complexity:  Evolution of shape and compound streams

- HCME distention
- e.g., *Newkirk et al.*[1981], *Suess* [1988], *Odstrcil and Pizzo, Russell, Mulligan, et al.*
- Stream-HCME interactions
- e.g., *Crooker and Cliver* [1994], *Fenrich and Luhmann* [1998], *Odstrcil and Pizzo*
- Multiple HCME interactions
- e.g., *Gopalswamy et al., Cargill et al.*

*Burlaga et al.* [1987]

*Crooker and Intriligator* [1996]

## Improving global views

- IPS and multispacecraft analysis
- [*Behannon et al.,* 1991]

- Helios photometer tomography
- [*Jackson et al.,* 2002]

## Contextual complexity: Outflows at sector boundaries

- HCMEs often bring or carry the polarity reversal marking a sector boundary [e.g.,*Crooker et al.*, 1998]
- Newly identified signature suggests large-scale transient outflows at sector boundaries may be more common than previously thought
- Consists of mismatch between magnetic field reversals and polarity reversals incontrovertibly identified in electron data

## Suprathermal electrons as incontrovertible sensors of polarity

**Q** ll **B**  away polarity
**Q** anti-ll **B**  toward polarity
**Q•B** always gives correct polarity, independent of local **B** orientation
**Q•B** can distinguish fields turned back on themselves

**Q**

**B**

*Kahler et al.* [1996]

## Polarity reversal precedes field reversal

**AWAY**

**TOWARD**

- 21-hour mismatch

***Wind data, 29-30 May 1995***

- Electron pitch
- angle  spectrogram

- Magnetic longitude

## Topology of mismatched reversals

- Magnetic field does not change at polarity reversal because away field line coils back on itself.
- Magnetic reversal occurs between coiled and straight field lines of same polarity.
- Signature found at 8 of 28 successive sector boundary crossings in 1995.
- One was caused by an open magnetic cloud.
- Remaining have few other HCME signatures.
- Mismatch may be signature of more general class of HCME [cf. *Howard et al., *1995].

## STEREO vision focused on contextual complexity can help determine

- shapes of propagating HCMEs and dependence of shape on internal properties
- shapes and dynamics of multiple HCME and stream-HCME interaction regions
- characteristics of a more general class of HCMEs at sector boundaries

## Discussion

- What do we know about the range of HCME forms from existing coronograph measurements?
- Will STEREO be able to identify
- a range of forms in oncoming CMEs for correlation with in situ observations?
- three-part structure in oncoming CMEs?
- which forms give rise to
- magnetic clouds?
- magnetically closed HCMEs?
- mismatched polarity and field reversals?