The Effect of Solar Wind on Pulsar Observations

Xiaopeng YOU

Southwest University, Chongqing, China

Outline

• Introduction

• Our solar wind model

• Solar wind effect 1: DM variations

• Solar wind effect 2: RM variations

• Conclusion

Introduction---motivation

• Main goal of PPTA project– Detecting gravity wave

• Timing precision requirement– 20 MSPs, 100 ns

• Removing annoying “noise”– ISM– Solar wind

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

The effect of ISM and solar wind:1

• Dispersion Measure

（ DM ）

21

22

12

0dDM

vv

ttKln

L

e

DM variations from ISM

20 millisecond pulsars

(You et al., 2007)

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: n0=10 cm-3

TEMPO2: n0= 4 cm-3

• 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 20o 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

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

Synoptic chart

PSR J1022+100, Aug 25th, 2006

The result of new model : DM

PSR J1744-1134 ， from 2004 to 2006

Compare with Observed Data

Left ： Our data (You et al. 2007) ； Right ： Nancay data (Cognard et al. 1996)

The effect on pulsar timing

Simulating three years observing data of PSR J1744-1134

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

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)

RM of PSR J1022+1001 from 2005 to 2008 by Parkes telescope

2. Observing data

□： 2005

☆： 2006

△： 2007

⊕： 2008

RM from observation

Synoptic chart

PSR J1022+100, Aug 25th, 2006

The result of new model 2: RM

RM of our model for PSR J1022+1001 in 2006

RM_sun from our model

Comparing with observed data

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

Conclusions

• Two-state solar wind model 。• predicting DM and RM variations by so

lar wind from our model 。• Comparing with observing data, it sho

ws that our model is better than previous model