1. Anemone Structure and Geo-Effective Flares/CMEs
A. Asai1, T.T. Ishii2, K. Shibata2,
N. Gopalswamy3, R. Kataoka4, M. Oka2
1: Nobeyama Solar Radio Observatory, NAOJ
2: Kyoto University
3: NASA/GSFC
4: STE-Lab., Nagoya University
CSWM
2006 November

2. 2005-August-24 Storm
2 M-class flares
Flares
CMEs
Focusing on the features of the sun (photosphere and corona)
strong geo-magnetic storm
Dst ~ -216 nT

3. Birth & Evolution of NOAA 10798
movie of SOHO/MDI magnetogram
emergence!

4. Feature of NOAA 10798 Emerged pair violates the Hale’s polarity law!
the order of N/S polarity regions with respect to the east-west direction is determined in a given hemisphere S N S N
highly twisted magnetic structure lies beneath the photosphere!?
generate X17 flare in the next rotation
NOAA 10798 N S S N

5. Soft X-Ray Lightcurve (GOES)
emergence
22-Aug
3 M-class flare occurred
We focus on the first 2 flares on 2005-Aug-22

6. Filament Formation
southward magnetic field
From Ha images, we can identify a filament whose axial field directs south

7. Anemone of NOAA 10798 NOAA 10798 is a large and complex AR
anemone structure CH
SOHO/EIT 195A image
NOAA is a large and complex AR
3 M-class flares, CMEs occurred

8. Anemone Structure
sea anemone
Shibata et al. (1994)
anemone is mainly an active region that appears inside a coronal hole
nest of (gigantic) jets (not so active)

9. 2 M-Class Flares flare2 flare1 M5.6 M2.6 Near southwest limb
flare1: (S11 W54)
flare2: (S12 W60)
Both are long duration events (LDEs)
Clear arcade structure can be seen
Movie of SOHO/EIT (195A)

10. 2 Halo-CMEs Associated with the flares, Halo-type CMEs occurred
08/22 01h (flare1: M2.6)
CME1: 1200 km/s
08/22 17h (flare2: M5.6)
CME2: 2400 km/s
very fast CME!
Time interval is ~16hours, but the 2nd CME may catch up the 1st one
SOHO/LASCO C3

11. LASCO/C2 – EIT
LASCO/C3 diff
CME 1
CME 2

12. Interplanetary Disturbances50
n [cm-3]
700
V [km/s]
ACE data
shock: 8/24 05:30UT
very complex structure
strong southward magnetic field: –50 nT
merging of 2 CMEs 50
|B| [nT]
Bx [nT]
By [nT]
Bz [nT]
–50
Dst

13. Event Summary 2 LDE flares occurred on 2005 August 22
NOAA was close to the west limb (~W60)
Halo-type CMEs occur regardless of the near-limb position
1st CME : 1200 km/s, 2nd CME : 2400 km/s
CME speeds were extremely fast
Strong southward magnetic field region
Ha filament whose axial field directs southward was formed

14. Anemone Structure and Flares/CMEs
For a small AR, CH works to collimate the ejections
In the case of NOAA 10798, a small CH and quite a big AR…
+ Low density above the AR
+ Guided by open field line
Easy for ejections to expand
Halo CMEs
High speed CMEs
Geo-effective CMEs
AR: active region
CH: coronal hole

15. Summary NOAA 10798 big magnetic storm (2005 August 24)
has a potentially complex structure (violating the Hale’s polarity law)
emerged in a small coronal hole  anemone structure
formed filaments, whose the axial field is southward
generated 3 M-class flares (2005 August 22–23),
followed by Halo-type CMEs
CMEs are very fast, and are widely spread
strong southward magnetic field (2 CMEs)
big magnetic storm (2005 August 24)