Quick Substorm Development during Initial 10 Minutes of Magnetic Storm M. Yamauchi, IRF-Kiruna T. Iyemori, WDC-C2, Kyoto (Geomagnetic) H. Frey, SSL/UCB (IMAGE-FUV) M. Henderson, LANL, Los Alamos (LANL) H. Singer, NOAA, Boulder (GOES) Many thanks to all teams that provided data

Acknowledgements Ground: Geomagnetic field data are provided partly through INTERMAGNET by British Geological Survey, Danish Meteorological Institute, Ecole et Observatoire des Sciences de la Terre, Finnish Meteorological Institute, Finnish Academy of Science, Geological Survey of Canada, Geological Survey of Sweden, Geoscience Australia, Institute of Geological and Nuclear Sciences, Institute of Solar- Terrestrial Physics at Irkutsk, The Irish Meteorological Service, Leirvogur geomagnetic station, Lviv Centre of Institute of Space Research, National Institute of Information and Communications Technology, Polish Academy of Sciences, Tromsoe Geophysical Observatory in Norway, and United States Geological Survey. Cutlass HF data and its interpretation is provided by Mark Lester at Leicester University. Satellites: ACE/Geotail/WIND/Polar/Cluster magnetic field data are provided by the ACE/MAG team (PI: N. Ness at Bartol Reseach Institute) through the ACE Science Center, Geotail/MGF team (PI: T. Nagai at Tokyo Institute of Technology) through ISAS/Geotail page, WIND/MFI team (PI: R. Lepping at NASA/GSFC) through NASA/WIND page, Polar/MFE team (PI: C.T. Russell at IGPP), and Cluster/FGM team (PI: A. Balogh at Imperial College) through Cluster data center. Shock arrival timing detected by Cluster is identified by T. Horbury at Imperial College. The Cluster and Polar particle data for shock identification are provided by Cluster CIS team (PI: H. Reme at CESR) and Polar HYDRO team (PI: J. Scudder at Univ. Iowa) through NASA CDAweb. DMSP convection data is provided by Center for Space Sciences at the University of Texas at Dallas and the US Air Force. GOES satellite project is managed by NOAA, and the data is prepared by A. Newman, LANL satellite project is managed by Los-Alamos National Laboratory, and IMAGE project is supported by NASA.

Outline * Focus on the initial 6 minutes of the Halloween magnetic storm starting on 29 October 2003 (sudden commencement at 0611 UT). * Observed three onsets of strong ionospheric westward electrojet (2000~4000 nT) in the inner magnetosphere region. (1) Clear substorm onset in the evening-midnight sector staring at 0612 UT, expanding poleward. (2) Substorm-like westward electrojet in the morning sector starting at 0612~0613 UT (rather that cusp-related activity), expanding west. (3) The strongest activity (~4000 nT) in post-midnight sector started where and when the above two expanding activities met each other. * Gather as much data as possible to demonstrate the development.

Data (1) Overview: Geomagnetic indices (2) Timing of shock arrival (∆B except LANL) (a) Interplanetary space: ACE, Geotail, WIND (b) Magnetosphere: LANL (p+,e-), GOES, Cluster, Polar (c) Earth: Ground geomagnetic field (1s value) (3) Substorm-like geomagnetic activity (a) ground:geomagnetic field (1 min values / Mlat) (b) magnetosphere: GOES (B), LANL (p+,e-) (c) auroral emission: IMAGE (FUV) (4) Not available: EISCAT did not operate Cutlass HF data has no signal due to disturbed condition FAST and DMSP satellites did not cover the region during this 10 minutes.

Geomagnetic indices Examine first 10 min after the SC AU & AL Dst ASM & SYM

ACE + Geotail (+ Wind) ACE: 0558:20 UT / +221 Re GTL: 0609:40 UT / +26 Re Wind: 0619:30 UT / -156 Re  1900 ~ 2000 km/s Geotail ACE Wind By<0

Geosynchronous (dayside) 07 LT 11 LT 13 LT 16 LT 19 LT 07 LT 11 LT 13 LT 16 LT 19 LT 04 LT 0610:50 UT LANL p keVLANL e keV

Geosynchronous (nightside) GOES & Polar 5s resolution data, geographic coordinate GOES-10 ≈ 21 LT (thin lines) GOES-12 ≈ 1 LT (thick lines) Polar ≈ 21 LT (dotted lines) SC = 0611:30~0611:40 UT

Ground ∆B (1 sec resolution) KRN ( Kiruna ) LT, 65° WMQ ( Urumq i) LT, 34° MMB ( Memanmetsu ) LT, 35° KNY (Kanoya ) LT, 22°

Summary of the shock propagation timing IMF B Y < 0

Ground ∆B (1 min resolution) Ground ∆B (∆X or ∆H) sub-auroralauroralpolar cap regionregionregion midnight morning evening midnight morning midnight IQA≈01 LT

GOES & Polar 5s resolution data, geographic coordinate GOES-10 ≈ 21 LT (thin lines) GOES-12 ≈ 1 LT (thick lines) Polar ≈ 21 LT (dotted lines) Onset = 0612:00 UT Extra onset = 0616:40 UT

IMAGE-FUV (southern hemisphere) 0611:40 UT 0613:40 UT 0615:40 UT 0617:40 UT

Ground ∆B + auroral image evening- midnight morning 0611:40 UT 0613:40 UT 0615:40 UT 0617:40 UT IQA≈01 LT

timings of events UT Magnetosphere / Ground ∆B / Aurora 0609:50Shock arrival at Geotail (26 Re upstream) 0610:50+40sShock arrival at geosynchronous satellites 0611:20Start of Sudden commencement (peak at 0612 UT) 0611:30Residual from the previous auroral arc 0612:00Dipolarization at GOES 0612Onset of westward electrojet in evening-midnight 0612~0613Onset of westward electrojet in morning 0613:30 Midnight spot & morning arc are suddenly intensified 0615:40 Both brightened regions expand 0616:40Sharp spike of B at GOES-12 (01 LT) 0617~0618 ∆Bx = nT/min at IQA (01 LT) 0617:40 Both brightened regions merged at post-midnight.

Summary : three onsets During initial 6 minutes of the magnetic storm on 29 October 2003, we observed three onsets of strong ionospheric westward electrojet (2000~4000 nT) in the inner magnetosphere region. (0a) 06:11 UT: The shock swept the magnetosphere 0.3 Re/sec ≈ upstream velocity. (0b) 06:11:21 UT: Global SC at both dayside mid-latitude & morning high-latitude. (1) 06:12 UT Onset of ordinary strong substorm (>1000 nT / 2 min) in the evening-midnight sector with a poleward expanding westward electrojet. * Most likely directly triggered by the shock arrival. * Maintained by direct energy pumping from the SW.

Summary (part 2) (2) 06:12~06:13 UT: Onset of strong westward electrojet + auroral emission in the morning auroral zone (around 65 MLat), eastward electrojet at poleward stations (> 70 Mlat). Activity expand steadily westward toward the night without vortex signature. * Trend (= westward electrojet) + oscillation  Not the cusp or KH-related phenomena. * Auroral & electrojet correspond to Region 2 FAC (J // )  Similar to a local substorm * Powered by SW dynamo via Region 1 J // at conv. reversal.

Summary (part 3) (3) 06:17 UT A localized sharp development (3000 nT / 2 min ∆B) only at 01 LT (IQA station) together with spiky increase of B by GOES-12 at 01 LT. The onset is when and where two previous activities met at high-latitude midnight. * High and sharp activity + localized + unusual spike at GOES  Difficult to understand. One possible scenario (speculation): a part of the dayside J// system is detached and swept tailward, briefly passing very close to the substorm current system, and that this passage triggered the third activity?

extra slides

Norway ∆B

Image / FUV (southern hemisphere)

timing UT MagnetosphereGround/Ionosphere 0609:50Shock arrival at Geotail (26 Re upstream) 0610:50Shock arrival at LANL-02A (11 LT) and LANL-97A (13 LT) 0611:10Shock arrival at LANL-01A (07 LT) 0611:20Shock arrival at (04 LT), (16 LT), Cluster (X=0 Re, Z=-10 Re) 0611:20Start of Sudden commencement 0611:30Residual from the previous auroral arc 0611:30Shock arrival at (19 LT) and Polar (21 LT, Z=0 Re) 0611:40Shock arrival at GOES-12 (01 LT) and GOES-10 (21 LT) 0612:00Start of dipolarization at GOES-12 (01 LT) and GOES-10 (21 LT) 0612 Peak of SC / Onset of westward electrojet in evening-midnight 0612~0613Onset of westward electrojet in morning 0613:30 Midnight spot and the morning arc were suddenly intensified 0615:40 Both brightening expanded 0616:40Sharp spike of B at GOES-12 (01 LT) 0617~0618 ∆Bx = nT/min at IQA (01 LT) 0617:40 The two brightened regions merged at post-midnight.