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Anemone Structure of AR NOAA 10798 and Related
Geo-Effective Flares and CMEs
A. Asai1( 浅井 歩 ), T.T. Ishii2, K. Shibata2, N. Gopalswamy3
1: Nobeyama Solar Radio Observatory, NAOJ2: Kyoto University3: NASA/GSFC
COSPAR2006-A-02406; D2.1-0023-06COSPAR 2006, Beijing, China 2006-July-19
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Today’s Topic
A magnetic storm (2005 August 24) and the related eventsBirth and evolution of A
R NOAA 10798Flares and CMEs (2005
August 22)Magnetic storm (2005 A
ugust 24)Focusing on the featur
es of the sun (photosphere and corona)
8/23 24 25 26 27
Dst Index
nT
Dst ~ 216 nT
FlareCME
magnetic storm
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movie of SOHO/MDI magnetogram
Birth & Evolution of NOAA 10798
emergence!
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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
highly twisted magnetic structure lies beneath the photosphere!?generate X17 flare in the next rotation
NOAA 10798
NSNS
N S
NS
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Soft X-Ray Lightcurve (GOES)
3 M-class flare occurred We focus on the first 2 flares on 2005-Aug-22
emergence
22-Aug
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2 M-Class Flares
Near southwest limb flare1: (S11 W54) flare2: (S12 W60)
Both are long duration events (LDEs)
Clear arcade structure can be seenMovie of SOHO/EIT (195A)
flare1M2.6
flare2M5.6
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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
ACE datashock: 8/24 05:30UT
very complex structure
strong southward magnetic field: –50 nT
merging of 2 CMEs?CIR + shock?
n [cm-3]
V [km/s]
|B| [nT]
50
700
50
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 CMEsThe 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 mor
e detail
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Southward Magnetic Field?
From H images, we can identify a filament whose axial field directs south
N
S
on 2006 August 21
H image obtained with SMART of Kyoto Univ.
SOHO/MDI
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Anemone Structure
anemone structure: active region that appears inside a coronal hole
nest of (gigantic) jets (not so active)
sea anemone
SOHO/EIT 195A image
anemone structure
CH
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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 expandHalo CMEsHigh speed CMEs AR: active region
CH: coronal hole
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Summary
NOAA 10798 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 southwardgenerated 3 M-class flares (2005 August 22–23), followed by Halo-type CMEsCMEs are very fast, and are widely spreadstrong southward magnetic field (2 CMEs / CIR + shoc
k)
big magnetic storm (2005 August 24)
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Thank you!
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Longitudes of Storm-related CMEs
15W
N
S
WE
O Dst < - 200 nTO - 300nT < Dst < - 200 nT
O Dst < - 300 nT
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)
37/55 = 67%18/55 = 33%
SEP
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SEPイベント
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Coronal Features of NOAA 10798
SOHO/EIT (195A)
NOAA 10798
CH
10797
New AR appears in a small coronal hole