1. Anemone Structure of AR NOAA 10798 and Related Geo-Effective Flares and CMEs
A. Asai1, T.T. Ishii2, K. Shibata2, N. Gopalswamy3
1: Nobeyama Solar Radio Observatory, NAOJ
2: Kyoto University
3: NASA/GSFC

2. Today’s Topic A magnetic storm (2005 August 24) and the related events
Flare
A magnetic storm (2005 August 24) and the related events
Birth and evolution of AR NOAA 10798
Flares and CMEs (2005 August 22)
Magnetic storm (2005 August 24)
Focusing on the features of the sun (photosphere and corona)
CME
Dst Index
magnetic storm nT
Dst ~ 216 nT 8/

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

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

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

6. 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!
SOHO/LASCO C3

7. Interplanetary Disturbance50
n [cm-3]
Interplanetary Disturbance
700
V [km/s]
ACE data
shock: 8/24 05:30UT
very complex structure
strong southward magnetic field: –50 nT
merging of 2 CMEs?
CIR + shock? 50
|B| [nT]
Bx [nT]
By [nT]
Bz [nT]
–50
Dst

8. Event Summary 2 LDE flares occurred on 2005 August 22
NOAA was close to the west limb (W60)
Halo-type CMEs
The 2nd CME is especially fast (2400 km/s)
Strong southward magnetic field region
What was the origin of the southward magnetic field?
Why did halo-type CMEs occur regardless of the near-limb position?
Why were so fast CMEs?
Examine the features of the active region in more detail

9. 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
highly twisted magnetic structure lies beneath the photosphere!
generate X17 flare in the next rotation N S N
NOAA 10798 N S S N

10. Southward Magnetic Field?
Ha image obtained with SMART of Kyoto Univ.
From Ha images, we can identify a filament whose axial field directs south
on 2006 August 21
(previous day) N S
SOHO/MDI

11. Anemone Structure
anemone structure
sea anemone CH
SOHO/EIT 195A image
(sea-) anemone structure: active region that appears inside a coronal hole
nest of (gigantic) jets, not so active

12. 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 magnetic pressure above the AR
Easy for ejections to expand
Halo CMEs
High speed CMEs
collimate
expand
AR: active region
CH: coronal hole

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

14. Thank you!

15. Longitudes of Storm-related CMEs
18/55 = 33% N
37/55 = 67%
15W
SEP E W S
East-West Asymmetry of solar sources is confirmed
(Wang et al. 2002; Zhang et al. 2003)
Larger storms (Dst < -200 nT) seem to occur
Close to the disk center (±15 deg)
O Dst < nT
O nT < Dst < nT
O Dst < nT

16. SEPイベント

17. Coronal Features of NOAA 10798
SOHO/EIT (195A)
NOAA 10798
10797 CH
New AR appears in a small coronal hole