Substorm location and timing using CARISMA ground-based magnetometers

1. Substorm location and timing using CARISMA ground-based magnetometers I. R. Mann, D.K. Milling, A. Kale University of Alberta

2. Substorm onset models and THEMIS • CD model and NENL model - distinguished by timing THEMIS: 3 inner probes monitor current disruption. 2 outer probes monitor tail lobes. Ground-based observations in the US/Canada sector are needed for auroral breakup timing and location. GBOs deployed by UofC UofA will host THEMIS magnetometer data centre

3. Planned and existing CARISMA, THEMIS GBO and CANMOS magnetometers - 1s and 8Hz real-time fluxgate data from all CARISMA sites. - GPS timed; data loggers at all sites prevents data loss.

4. Substorm Timing THEMIS probes give onset timing < 10s Array of GBOs with ASIs < 10s Magnetometers: 2 ULF signals observed at substorm onset Pi2 (40-150s) => ~60s ‘Global’; auroral zone transverse mode source mixed with fast mode wave at mid-lats. (will implement real-time detection algorithm – Nose et al., 1995) Pi1B (1-40s) => ~3s ; ‘Local’; peak power associated with WTS and electrojet; Ducting horizontally. Pi1B measured both with CARISMA 8 Hz data and SCMs. Network of CARISMA induction coils offers 50 Hz data – high sensitivity for structured Pc1-2 (pearls, IPDP etc) as well as Ionospheric Alfven Resonator!

5. Substorm location 3-D Biot-Savart • Context for THEMIS measurements can be provided by mid-latitude magnetometers. Where is the probe meridian in relation to the SCW? Simple model Reversal of Z at Electrojet latitude Simple model overestimates SCW width and underestimates Electrojet latitude – more realistic model required (e.g. Cramoysan et al., 1995).

6. Fort Smith SCW structure – EJ at GEO Pi2 Bandpass Filtered 40-200 s Pi1B Highpass filtered at 10 s What do auroral images and riometer data look like?

7. Structured Pc1-2 (pearls, IPDP…) MCMU • New CARISMA fluxgate magnetometer data at 8Hz shows clear structured Pc1-2. • Sometimes this is visible across multiple stations in the CARISMA array. • Studies to examine excitation mechanisms, comparison to FAC and riometer absorption (precipitation) signatures should be scientifically valuable.

8. MCMU FSMI

9. Ionospheric Alfven Resonator • Appears difficult to see IAR in 8Hz fluxgate CARISMA data. • Spectral resonance structures (SRS) are however visible in induction coil network data. • Study by Cash et al., (2005) suggests frequencys correlate with fof2. • Example IC data from Hyashi coils (as well as new data from Shiokawa coils in Athabasca) show IAR clearly.

10. Magnetometer data: www.ssdp.ca • Download and plot archive data. • Online time-domain spectral filtering (Pi2, Pi1, etc). • Real-time 1s data flow. • 8 Hz on request.

11. Summary • Ground-based Magnetometers can provide substorm onset timing and location information. • CARISMA magnetometers are important in providing this data for THEMIS - complementary to the ground network of ASIs • Always available; unaffected by cloud or daylight. New mid-latitude coverage will provide cleaner Pi2 and SCW bay signatures. • New loggers, GPS timing, and satellite VSat HSI data collection. Upgraded standard 1s data product (from 5s). New 8Hz fluxgate data stream. • Expansion of CARISMA to mid-latitude begins next summer. Also induction coil magnetometers (50Hz) to be deployed at 8 sites. • Data freely available from www.ssdp.ca. 1s data stream being integrated into THEMIS archive. • Provides clear SCW, Pi2 and Pi1B substorm signals. • Additional science targets: Substorm relationship to energetic particle dynamics, M-I coupling, etc (e.g., EMIC waves, Pc1-2 emissions, IAR etc).