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

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 8/23 24 25 26 27

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

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

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)

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

Interplanetary Disturbance 50 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

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

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

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

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

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

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)

Thank you!

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 < - 200 nT O - 300nT < Dst < - 200 nT O Dst < - 300 nT

SEPイベント

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