1. The Effect of Solar Wind on Pulsar Observations Xiaopeng YOU Southwest University, Chongqing, China

2. Outline Introduction Our solar wind model Solar wind effect 1: DM variations Solar wind effect 2: RM variations Conclusion

3. Introduction ---motivation Main goal of PPTA project –Detecting gravity wave Timing precision requirement –20 MSPs, 100 ns Removing annoying “noise” –ISM –Solar wind

4. Solar wind --- plasma with speed ~ 400 km/s, complex structure Quasi-static and transient component –quasi-static ： co-rotating with the Sun ； –Transient component ： changes very quickly ， coronal mass ejections Our model, concentrate on quasi-static component Introduction --The solar wind

5. The effect of ISM and solar wind:1 Dispersion Measure （ DM ）

6. DM variations from ISM 20 millisecond pulsars (You et al., 2007)

7. Why need more accurate model Previous model of electron density of solar wind, spherically symmetric, quadratic decrease Previous model not accurate (you et al, 2007) Need new model TEMPO: n 0 =10 cm -3 TEMPO2: n 0 = 4 cm -3

8. Fast wind ： lower density, originate in active regions at high latitude Slow wind ： relatively high density, originate in active regions at low or middle latitude Assume slow wind occupies the zone within 20 o of the magnetic neutral line and outside this is dominated by the fast wind and that both winds flow radially. Two-state model ： fast and slow wind

9. Method and Data Analysis The Sun B Pulsar C The Earth A The Sun B Pulsar C The Sun B Pulsar C The Earth A The Sun B The Earth A Pulsar C The Sun B The Earth A Pulsar C The Sun B The Earth A Position of pulsars relatively positions of the pulsar, the Sun and the Earth Observing time make sure the Carrington rotation (starting 1976, May) Data from Wilcox Solar Observatory According the data, determine the structure of slow and fast wind

10. Synoptic chart PSR J1022+100, Aug 25 th, 2006

11. The result of new model : DM PSR J1744-1134 ， from 2004 to 2006

12. Compare with Observed Data Left ： Our data (You et al. 2007) ； Right ： Nancay data (Cognard et al. 1996)

13. The effect on pulsar timing Simulating three years observing data of PSR J1744-1134

14. Summary of DM variation of solar wind Developed a new solar wind electron density model Our model is more accurate than previous one Use of the older solar wind models (or no correction) leads to systematic errors in measured pulsar parameters Our new model is important for high precession pulsar timing

15. The effect of ISM and solar wind:2 Rotation Measure （ RM ） |b| < 8 degree 63+223+477 RMs by Parkes +GBT (Han et al. 1999, 2006, 2009)

16. RM of PSR J1022+1001 from 2005 to 2008 by Parkes telescope 2. Observing data □： 2005 ☆： 2006 △： 2007 ⊕： 2008 RM from observation

17. Synoptic chart PSR J1022+100, Aug 25 th, 2006

18. The result of new model 2: RM RM of our model for PSR J1022+1001 in 2006

19. RM_sun from our model

20. Comparing with observed data

21. Summary of RM variations by solar wind We developed a model to predict the RM induced by solar wind PSR J1022+1001 shows significant RM variation by solar wind Comparing with observing data, it shows that observed RM variations can be predicted by our model

22. Conclusions Two-state solar wind model 。 predicting DM and RM variations by solar wind from our model 。 Comparing with observing data, it shows that our model is better than previous model