Anemone Structure of AR NOAA 10798 and Related GeoEffective Flares and CMEs

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

COSPAR2006-A-02406 D2.1-0023-06 COSPAR 2006,
Beijing, China 2006-July-19
2
Todays Topic
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
8/23 24 25 26 27
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Birth Evolution of NOAA 10798
emergence!
movie of SOHO/MDI magnetogram
4
Feature of NOAA 10798
Emerged pair violates the Hales 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

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2 M-Class Flares
flare2 M5.6
flare1 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)
7
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
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Interplanetary Disturbance
50
n cm-3
V km/s
700

• ACE data
• shock 8/24 0530UT
• 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
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Event Summary

• 2 LDE flares occurred on 2005 August 22
• NOAA 10798 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

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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
N
S
SOHO/MDI
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Anemone Structure
anemone structure
sea anemone
CH
SOHO/EIT 195A image

• anemone structure active region that appears
  inside a coronal hole
• nest of (gigantic) jets (not so active)

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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

AR active region CH coronal hole
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Summary

• NOAA 10798
• has a potentially complex structure (violating
  the Hales 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 2223),
• followed by Halo-type CMEs
• CMEs are very fast, and are widely spread
• strong southward magnetic field (2 CMEs / CIR
  shock)
• ?big magnetic storm (2005 August 24)

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Thank you!
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Longitudes of Storm-related CMEs
N
37/55 67
18/55 33
15W
SEP
W
E
S
East-West Asymmetry of solar sources is
confirmed (Wang et al. 2002 Zhang et al.
2003) Larger storms (Dst lt -200 nT) seem to occur
Close to the disk center (15 deg)
O Dst lt - 200 nT O - 300nT lt Dst lt - 200
nT O Dst lt - 300 nT
16
SEP????
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Coronal Features of NOAA 10798

• SOHO/EIT (195A)

NOAA 10798
10797
CH
New AR appears in a small coronal hole