1. Measurements of White-Light Images of Cometary Plasma as a Proxy for Solar Wind Speed J.M. Clover, M.M. Bisi, A. Buffington, B.V. Jackson, P.P. Hick Center for Astrophysics and Space Sciences, UCSD, USA

2. Scale: SMEI 100° cut. tail extends >45° from nucleus Differences between ground based and space based images of comets

3. Scale: Ground based 9° Differences between ground based and space based images of comets

4. Scale: ground based 0.3° Differences between ground based and space based images of comets

5. Scale: 0.3° image adjustment Differences between ground based and space based images of comets

6. Scale: 0.3° image superimposed over 9° image Differences between ground based and space based images of comets

7. Scale: 9° image superimposed onto smei cut. Differences between ground based and space based images of comets

8. from angle on the sky to distance using comet ephemerides and assuming a radial outflow of solar and cometary plasma, speed can be measured

9. C/2002 T7 Linear With and without perspective removal Top: with perspective Removed Bottom: without perspective removed

10. Assumptions and Pitfalls Beyond a certain distance, cometary plasma flows radially with the solar wind and is no longer heavily influenced by the comet’s wrapped magnetic field. Comets that move nearly parallel to the plane of observation are difficult to accurately measure. Comet must be bright and relatively close to the observing instrument for best results.

11. C/2001 Q4 NEat from 4-6 may 2004 radial velocities change frequently and are not necessarily associated with disconnection events

12. most visible tail motion correlates to decrease in velocity long straight tail indicates high velocity; tail bent indicates decrease in velocity

13. C/2002 T7 LINEAR from 17-20 may 2004 Measurements indicate large region of low velocity

14. C/2002 T7 LINEAR from 17-20 may 2004 Measurements indicate large region of low velocity

15. in-situ measurements at earth why in-situ instruments are unable to corroborate our measurements IN-SITU MEASUREMENTS REALLY ARE IN-SITU CHANGES IN MEASURED SPEED ARE LARGE SCALE COMPARED TO THE COMET, BUT VERY SMALL IN SCALE COMPARED TO THE HELIOSPHERE MEASURED CHANGES INDICATE THE AVERAGE VELOCITY OF THE SOLAR WIND IN WHICH THE ENTIRE COMET IS IMMERSED IN FLUX TUBE INTERACTION: REQUIRES MORE INVESTIGATION

16. SMEI is not the only instrument to see comets! SOHO/LASCO has observed and discovered numerous comets (mostly sun-grazers) STEREO/SECCHI has observed multiple comets

17. SMEI is not the only instrument to see comets! SOHO/LASCO has observed and discovered numerous comets (mostly sun-grazers) STEREO/SECCHI has observed multiple comets

18. both comets 2P/Encke left and 96P/Machholz right these movies give added perspective to the ‘big picture’ of what stereo sees

19. 2P/encke radial speed measured with stereo hi1a Radial speed measurements starting approximately april 20, 2007 (vertical scale in AU, sorry!)

20. comet 96p/machholz Very close to perihelion (~0.12 AU from sun) velocity gradient of 96p/machholz measured from stereo hi1a - 3-5 april 2007

21. Conclusions White-light imagers of all shapes and sizes each provide unique insights into the solar wind Measurements using this technique on dramatically different scales produce believable results These results may allow us to infer details about the small scale variations of the solar wind Results provide insight into the interaction of cometary plasma with the solar wind