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

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

movie of SOHO/MDI magnetogram

Birth & Evolution of NOAA 10798

emergence!

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

Soft X-Ray Lightcurve (GOES)

3 M-class flare occurred We focus on the first 2 flares on 2005-Aug-22

emergence

22-Aug

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

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

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

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

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

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

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

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)

Thank you!

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

SEPイベント

Coronal Features of NOAA 10798

SOHO/EIT (195A)

NOAA 10798

CH

10797

New AR appears in a small coronal hole