Vr: A New Index to Represent the Regional Geomagnetic Activity

1. Vr: A New Index to Represent the Regional Geomagnetic Activity Dongmei Yang, Yufei He, Chuanhua Chen, Yahong Yuan 2010-9-21 Changchun

2. Outline • Introduction • Data Processing • Results and Discussion • Conclusion

3. Outline • Introduction • Data Processing • Results and Discussion • Conclusion

5. The disturbances revealed by the first differences could be seen in all the observatories simultaneously which reminded us that the source for the disturbances was in the magnetosphere.

6. The first differences also showed 27 solar-cycle recurrences. The feature was quite similar with the Kp’s.

8. There are some disturbances that Kp could not describe. Another new index might be needed for people to understand the change of the magnetic field.

9. Outline • Introduction • Data Processing • Results and Discussion • Conclusion

10. Data • Minute data for the year 2008 from the following observatories • Chinese observatories • Global observatories • CLF, MMB, HON and SJG • Data downloaded from INTERMAGNET website

11. Method • Vr index calculation: • Calculating the first differences of the minute values of the geomagnetic horizontal component (H D/X Y). • calculating the hourly standard deviations of the above first differences. • Subtracting background noises (0.1nT) from the hourly standard deviations • In case that the hourly standard deviation was less than 0.1nT, the Vr value was assigned to be 0.

12. Noise level of 1s data • Noise Level achieved • D 0.06nT • H 0.07nT • Z 0.07nT • F 0.04nT

13. Outline • Introduction • Data Processing • Results and Discussion • Conclusion

14. Results and Discussion • Relationship between Vr and other indices • Temporal Change of Vr • Changes with the 27 solar rotation cycle • Seasonal change • Spatial change of Vr • Latitudinal dependences (not talked today) • Longitudinal dependences (Local time dependences)

15. Correlation between Vr and other indices

17. The first differences also showed 27 solar-cycle recurrences. The feature was quite similar with the Kp’s.

18. Monthly Means for H/X Component 按月排 按时段排

19. Monthly Means for D/Y Component 按月排 按时段排

20. Local time dependence of Vr

21. Observatories used in the study

22. Annual Means

23. H/X component D/Y component

26. Outline • Introduction • Data Processing • Results and Discussion • Conclusion

27. Conclusion • Vr is an index that can be used to detect geomagnetic disturbances from the magnetosphere. Vr has clear physical meaning. • Vr can detect geomagnetic disturbances not only those Kp and ap detect but also some small disturbances that Kp and ap can not detect. So Vr is more sensitive to the geomagnetic activities than Kp and ap. • Vr can be easily calculated by individual observatory so it can be used as a regional index and can serve people in quasi real time.

28. ENDThanks for your attention