Tracing Geomagnetic Conjugate Points by means of Extremely Similar Interhemispheric Auroras N. Sato (1), A. Kadokura (1), Y. Ebihara (1), H. Deguchi (1), and T. Saemundsson (2) (1)National Institute of Polar Research, Tokyo, Japan (2)Science Institute, University of Iceland, Iceland National Institute of Polar Research (NIPR) IAGA 2005

Auroral Conjugate Observation at Syowa and Iceland Visualization of the conjugate foot prints of the geomagnetic field lines

Mapping of Northern/Southern hemispheres with geomagnetic coordinate

Conjugate point of Syowa Station (IGRF model) Station Glat (deg) Glon (deg) Inv.lat (deg) Mlon (deg) MLT (hr) at 0.0 UT L value D (deg) I (deg)B (nT) Tjornes Syowa Comparison of geomagnetic parameters (Epoch: 23:20:00 UT, 26 Sep, 2003)

All-Sky Image and Geomagnetic mesh at 120 km altitude TJORNES SYOWA at 23:23:00 UT on Sep. 26, 2003 Magnetic zenith

Projection on Geomagnetic plane at 120 km altitude TJORNES SYOWA at 23:23:00 UT on Sep. 26, 2003 (elevation > 10 ﾟ )

Abstract of the Syowa-Iceland Auroral Conjugate Observation, so far Starting from 1984 (20 years anniversary ） Executed every year in the equinox season, mainly in September, for about two weeks Simultaneous darkness for about 4 hours Only 2 ～ 3 nights of simultaneous observation in one season, mainly due to weather condition Good conjugate event is rare ★ September 26, 2003 event : The best conjugate event in the 20 year history

SYOWAIceland Fluxgate magnetometer ○ Induction magnetometer ○ Riometer ○ VLF receiver ○ Imaging Riometer ○ All-sky TV camera ○ (only equinox) All-sky monochromatic Imager ○ (from 2005) Meridian Scanning Photometer Fabry-Perot Imager SuperDARN radar ○ MF-radar Ionospheric vertical sounder VHF Doppler radar Instruments at conjugate stations

Iceland ～ UK SAMNET magnetic meridian

September 26, 2003 event HAD YOR UPS NUR HAD YOR UPS NUR H D SAMNET data Pi2 onset : 23:18 UT Onset occurred at westward of Iceland meridian

TJR SYW MN S W E N MS W E September 26, 2003 event all-sky TV data (23:19:30 ～ 23:23:50 UT, 10 sec interval)

TJR SYW September 26, 2003 event all-sky TV data (23:24:00 ～ 23:28:20 UT, 10 sec interval)

TJR SYW September 26, 2003 event all-sky TV data (23:28:30 ～ 23:32:50 UT, 10 sec interval)

September 26, 2003 event Total Intensity & E-W Keogram TIME (UT)

Finding one-to-one correspondence Tracing temporal variation of conjugate location

Tracing temporal variation of conjugate location of Syowa

IMAGE/FUV WIC and POLAR VIS Earth Camera Longitudinal displacement depending on the clock angle Satellite Observation Østgaard et al. (JGR, 2004)

(X, Y, Z)gsm = (29.0 ～ 28.6, 11.1 ～ 12.5, 2.4 ～ 1.9) Re ACE Vsw ～ 500 km/s IMF data Geotail Østgaard et al. (JGR, 2004) T – 8.3 min for X= -10 Re

Magnetic variation at Syowa and Tjornes TJR SYW TJR SYW H （ｎ T) TJR SYW D （ｎ T) Z （ｎ T) September, 2003

Equivalent current & Ionospheric potential H D Z equivalent current & ionospheric potential B ＋ TJR SYW TJR SYW

j || N j || S If B N < B S then N P could be located eastward of S P NPNP SPSP North-South asymmetry of magnetospheric configuration ? dB BNBN BSBS Why B N < B S ? IMF B x effect ? (B x < 0 in this case) IMF B x

Summary  The September 26, 2003 event is the best one in the 20 year history of the Syowa-Iceland conjugate auroral observation.  Extremely similar auroral activities were observed for more than 1 hour.  During the observation, the conjugate point moved about 200 km in longitude and about 50 km in latitude.  This movement cannot be explained only by the B y or clock angle effect of the IMF.  North-south asymmetry of magnetospheric configuration could be a cause of the movement.

Vsw (km/s) B (nT) By (nT) Bz (nT) ASY-D (nT) ASY-H (nT) SYM-H (nT) ACE Overview of the solar – geomagnetic condition September, 2003

September 26, 2003 event All-sky TV data (23:50:00 ～ 23:55:50 UT, 10 sec interval) TJORNES SYOWA MH ML W E