The Halo CMEs’ Speeds and Energy of Their Related Active Regions

1. The Halo CMEs’ Speeds and Energy of Their Related Active Regions Yang Liu¹, and CDAW Source Identification Team² ¹Stanford University ² Including: E. Cliver, N. Gopalswamy, J. Kasper, N. Nitta, I. Richardson, B. Thompson, D. Webb, C. Wu, S. Yashiro, J. Zhang, A. Zhukov, etc.

2. Motivations • CMEs and active regions (large-scale and local fields): • Observation has shown some CMEs are associated with solar flares in active regions; • Studies further demonstrate correlation between the soft X-ray flux of flares and the speeds of the CMEs (Moon et al. 2002; Zhang et al. 2004); and also show relationship of the inferred magnetic reconnection rate and the acceleration of the CMEs (Qiu et al. 2004); • It is generally believed that the energy released during the events is primarily the free energy stored in the magnetic field in the corona. • Thus, it is reasonable to search for relationship between the magnetic energy of active regions and the related CMEs’ energy.

3. Purpose of this work • We are seeking for indexes from magnetograms that can describe the energy of solar active regions, and also seeking for possible correlation between the indexes and the related CMEs’ speeds; • We are seeking for advancing our understanding on underlying link between the local field of active regions and global phenomenon of CMEs.

4. Energy indexes of active regions From Fisher et al (2000) • Potential field energy of active regions. • Free energy of active regions (assuming single flux tube). • Index of free energy (single flux tube). Where L is self-inductance and I is electric current that can be computed assuming the field is force free. But we need to estimate force-free alpha. Two parameters to be calculated: tilt angle, and force free alpha (alpha).

5. Samples • We choose events from CDAW (Coordinate Data Analysis Workshop held in 2005) event list based on two criteria: • Halo-CMEs; • Solar source is associated with active regions.

6. List of the events

7. Potential field energy versus CMEs’ speeds • No correlation is found.

8. Properties of active regions versus CMEs’ speeds • No correlation was found between sizes of active regions and CMEs’ speeds; • No correlation was found between net flux of active regions and CMEs’ speeds.

9. Free energy in active regions versus CMEs’ speeds • Weak correlation was found between E_free/length and CMEs’ speed.

10. Energy index of active regions versus CMEs’ speeds • Weak correlation was found between the parameter ε×E_potential and CMEs’ speed.

11. Summary • Potential field energy of active regions versus CMEs’ speed: NO CORRELATION. • Free energy of active regions versus CMEs’ speed: WEAK CORRELATION. • Index of free energy of active regions versus CMEs’ speed: WEAK CORRELATION.

12. Conclusions • We have examined here two measures of free energy of solar active regions; we found weak correlations between such measures and related halo CMEs’ speed; • These correlations imply that, although magnetic field of active regions is localized and a CME is a global phenomenon, active regions make a significant contribution in energizing the active region-associated CMEs. It suggests again, from energy perspective of active regions and CMEs, that local and global fields are coupled each other.

13. Free energy of active regions versus CMEs’ kinetic energy • No correlation was found between total free energy of active regions and CMEs’ kinetic energy; • No correlation was found between proxy of total energy (ε×E_potential) of active regions and CMEs’ kinetic energy.