Stream interface slope near 1 AU and the configuration of the

heliospheric current sheet at 2.5 solar radii

K.D.C. Simunac

STEREO SWG

October 2009

Introduction

“… stream interfaces are offset from, but are aligned roughly parallel to, the heliospheric current sheet…because both arise from basically the same geometry back at the Sun”

Gosling and Pizzo, Formation and Evolution of Corotating Interaction Regions and Their Three Dimensional Structure, Space Science Reviews 89: 21 - 52, 1999.

Stream Interfaces:Quick Review

• The boundary marking a transition from slow to fast solar wind

• Speed increases

• Density drops

• Temperature increases

• Flow shears observedFigure 1 from Pizzo 1978.

Stream Interface: Example 1

1 hour averaged data from STEREO-A/

PLASTIC

28 June - 4 July, 2007

Bulk Speed [km/s]

Proton Density [cm-3]

Thermal Speed [km/s]

East/West Flow

[degrees]

North/South Flow

[degrees]

250

400

550

700

06/28/07 06/30/07 07/02/07 07/04/07 07/06/07

0

15

30

45

06/28/07 06/30/07 07/02/07 07/04/07 07/06/07

0

25

50

75

100

06/28/07 06/30/07 07/02/07 07/04/07 07/06/07

-12

-6

0

6

12

06/28/07 06/30/07 07/02/07 07/04/07 07/06/07

-8

-4

0

4

8

06/28/07 06/30/07 07/02/07 07/04/07 07/06/07

1

Lee 2000:Stream Interface Slope

“… the ratio of the N-S component to the E-W component of the transverse flow is -(e • n)/(e • n).”

Stream Interface 130 June 2007 06:48 to 07:09 UT

1 minute data from STEREO-A/

PLASTIC

1 minute averaged data

from STEREO-A/ IMPACT

-10

-5

0

5

10

30-Jun-200700:00

30-Jun-200706:00

30-Jun-200712:00

30-Jun-200718:00

01-Jul-200700:00

-10

-5

0

5

10

30-Jun-200700:00

30-Jun-200706:00

30-Jun-200712:00

30-Jun-200718:00

01-Jul-200700:00

250

350

450

550

30-Jun-200700:00

30-Jun-200706:00

30-Jun-200712:00

30-Jun-200718:00

01-Jul-200700:00

Bulk Speed [km/s]

East/West Flow

[degrees]

North/South Flow

[degrees]

B_R/B

-1.5

0

1.5

30-Jun-200700:00

30-Jun-200706:00

30-Jun-200712:00

30-Jun-200718:00

01-Jul-200700:00

QuickTime™ and aTIFF (Uncompressed) decompressor

are needed to see this picture.

Example 1

GONG line-of-sight ecliptic plane field model

Red: B_R < 0

Green: B_R > 0

∆East/West = -2.3º - 2.5º = -4.8º

∆North/South = 3.1º - 4.3º = -1.2º

slope = 0.25

Stream Interface 2

1 hour averaged data from

STEREO-A/ PLASTIC

28 June - 6 July, 2007

Bulk Speed [km/s]

Proton Density [cm-3]

Thermal Speed [km/s]

East/West Flow

[degrees]

North/South Flow

[degrees]

250

400

550

700

06/28/07 06/30/07 07/02/07 07/04/07 07/06/07

0

15

30

45

06/28/07 06/30/07 07/02/07 07/04/07 07/06/07

0

25

50

75

100

06/28/07 06/30/07 07/02/07 07/04/07 07/06/07

-12

-6

0

6

12

06/28/07 06/30/07 07/02/07 07/04/07 07/06/07

-8

-4

0

4

8

06/28/07 06/30/07 07/02/07 07/04/07 07/06/07

1 2

Stream Interface 24 July 2007 13:45 to 13:53 UT

1 minute data from STEREO-A/

PLASTIC

1 minute averaged data

from STEREO-A/ IMPACT

-10

-5

0

5

10

04-Jul-200700:00

04-Jul-200706:00

04-Jul-200712:00

04-Jul-200718:00

05-Jul-200700:00

-10

-5

0

5

10

04-Jul-200700:00

04-Jul-200706:00

04-Jul-200712:00

04-Jul-200718:00

05-Jul-200700:00

Bulk Speed [km/s]

East/West Flow

[degrees]

North/South Flow

[degrees]

B_R/B

275

375

475

575

04-Jul-200700:00

04-Jul-200706:00

04-Jul-200712:00

04-Jul-200718:00

05-Jul-200700:00

-1.5

0

1.5

04-Jul-200700:00

04-Jul-200706:00

04-Jul-200712:00

04-Jul-200718:00

05-Jul-200700:00

Example 2

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∆East/West = -5.2º - 1.4º = -6.6º ∆North/South = -1.3º - (-0.7º) = -0.6 slope = 0.09

Example 3

1 hour averaged data from

STEREO-A/ PLASTIC

4 - 13 July, 2007

-8

-4

0

4

8

07/04/07 07/06/07 07/08/07 07/10/07 07/12/07

-12

-6

0

6

12

07/04/07 07/06/07 07/08/07 07/10/07 07/12/07

0

25

50

75

100

07/04/07 07/06/07 07/08/07 07/10/07 07/12/07

0

15

30

45

07/04/07 07/06/07 07/08/07 07/10/07 07/12/07

250

400

550

700

07/04/2007 07/06/2007 07/08/2007 07/10/2007 07/12/2007

Bulk Speed [km/s]

Proton Density [cm-3]

Thermal Speed [km/s]

East/West Flow

[degrees]

North/South Flow

[degrees]

2

3

Stream Interface 311 July 2007 13:03 to 13:13 UT

1 minute data from STEREO-A/

PLASTIC

1 minute averaged data

from STEREO-A/ IMPACT

-1.5

0

1.5

11-Jul-200700:00

11-Jul-200706:00

11-Jul-200712:00

11-Jul-200718:00

12-Jul-200700:00

-10

-5

0

5

10

11-Jul-200700:00

11-Jul-200706:00

11-Jul-200712:00

11-Jul-200718:00

12-Jul-200700:00

-10

-5

0

5

10

11-Jul-200700:00

11-Jul-200706:00

11-Jul-200712:00

11-Jul-200718:00

12-Jul-200700:00

250

450

650

11-Jul-200700:00

11-Jul-200706:00

11-Jul-200712:00

11-Jul-200718:00

12-Jul-200700:00

Bulk Speed [km/s]

East/West Flow

[degrees]

North/South Flow

[degrees]

B_R/B

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are needed to see this picture.

Example 3∆East/West = -6.2º - 1.3º = -7.5º ∆North/South = -3.5º - (-7.8º) = 4.3 slope = -0.57

All 3 Examples and GONG Model

All 3 Examples and WSO Model

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WSO Radial 2.5 R_Sun model

All 3 Examples and ENLIL Model

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ENLIL model 0.1 AU

All 3 Examples and ENLIL Model

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ENLIL model 0.1 AU

QuickTime™ and aTIFF (Uncompressed) decompressor

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ENLIL model 0.1 AU

All 3 Examples and Predictive Science Model

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Predictive Science B_R at 2.5 Solar Radii

All 3 Examples and Predictive Science Model for 1 AU

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Predictive Science B_R at 215 Solar Radii

Example 4 -- More Recent

1 hour averaged data from

STEREO-A/ PLASTIC

28 Sept. - 6 Oct., 2009

-10

-5

0

5

10

28-Sep-2009 30-Sep-2009 2-Oct-2009 4-Oct-2009 6-Oct-2009

-10

-5

0

5

10

28-Sep-2009 30-Sep-2009 2-Oct-2009 4-Oct-2009 6-Oct-2009

0

20

40

60

80

28-Sep-2009 30-Sep-2009 2-Oct-2009 4-Oct-2009 6-Oct-2009

0

10

20

30

40

28-Sep-2009 30-Sep-2009 2-Oct-2009 4-Oct-2009 6-Oct-2009

250

350

450

550

28-Sep-2009 30-Sep-2009 2-Oct-2009 4-Oct-2009 6-Oct-2009

Bulk Speed [km/s]

Proton Density [cm-3]

Thermal Speed [km/s]

East/West Flow

[degrees]

North/South Flow

[degrees]

Stream Interface 41 October 2009 15:34 to 15:40 UT

-10

-5

0

5

10

01-Oct-200900:00

01-Oct-200906:00

01-Oct-200912:00

01-Oct-200918:00

02-Oct-200900:00

-10

-5

0

5

10

01-Oct-200900:00

01-Oct-200906:00

01-Oct-200912:00

01-Oct-200918:00

02-Oct-200900:00

250

350

450

550

01-Oct-200900:00

01-Oct-200906:00

01-Oct-200912:00

01-Oct-200918:00

02-Oct-200900:00

Bulk Speed [km/s]

East/West Flow

[degrees]

North/South Flow

[degrees]

Example 4

∆East/West = -2.9º - 1.7º = -4.6º ∆North/South = 0.3º - 0.7º = -0.4º slope = 0.09

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Summary and QuestionsAfter looking at about 30 cases with 1 hour time resolution, I conclude that the interfaces observed in connection with current sheet crossings do seem to be roughly parallel to the current sheet…somewhere.

I have looked at just a few interfaces with the 1 minute resolution data, but results are so far consistent with 1 hour averaged data.

In some cases the north/south and east/west flow shears are not exactly cotemporaneous -- what does this mean? How should I deal with it?

When the stream interface does not closely follow a current sheet crossing, what should we expect?

Thank you.

• PLASTIC team

• IMPACT team

• GONG consortium

• WSO

• Predictive Science

• CCMC