1. Targeted VLF Wave-injection Experiments Mark Gołkowski MURI Review Stanford University February 18, 2009

2. 2 Russian Alpha Transmitters  3.6 second pattern (six 0.6s segments)  400ms pulses, 200ms off between pulses  Three sites alternate among 3 frequencies 14.88 kHz 11.91 kHz 12.65 kHz L=2.61L=1.97L=1.78 Resonant Energies: ~50-500 keV

3. 3 Adelaide, Australia  ~500 kW ? Navigation transmitter in Komsomolsk na Amur in Russian far east (400 msec pulses) at L = 1.97  Conjugate point in southern Australia  Stanford University receiver since January 2007  Explore and quantify wave-growth Kangaroos Stanford Scientists Kangaroos

4. 4 Historical Background  Triggered emissions have been observed from other mid-latitude transmitters: NAA (L=2) 14.5 kHz, 200 msec pulses  Whistler-mode Komsomolsk Alpha pulses have been studied by Tanaka et al. 1987 in the context of whistler propagation characteristics

5. 5 Example 1-Hop

6. 6 Temporal (non-linear) Growth

7. 7 Example Growth ~7-8 dB total ~70-80 dB/sec

8. 8 Example Growth

9. 9 Example Detection

10. 10 10-Day Statistics (1-10 April)  Count of 1-hop observations in synoptic (1min/5min) recordings  10 days during and after a geomagnetic disturbance  1-Hop observations show qualitative relationship to geomagnetic activity Need more data to quantify relationship

11. 11 Diurnal patterns Day NightDay Night

12. 12 Average Daily Variations Sunrise Sunset Tanaka et al. 1987Stanford 2008  Diurnal variation shows maxima after sunset and sunrise  Tanaka et al. 1987: diurnal variation is same for whistlers and is a propagation effect (duct formation, coupling in/out of duct)

13. 13 DEMETER Observations (1) Novosibirsk Komsomolsk Krasnodar DEMETER 2-Hop Echoes 2-Hop echoes with triggered emissions excited by Novosibirsk transmitter observed on DEMETER Transmitter: L=2.61 Echoes observed from L=1.77 (start of burst mode) to L=1.64 Max Amplitudes: ~1  V/m 2-Hop Propagation Time: ~1.25 seconds

14. 14 DEMETER Observations (2) DEMETER  Triggered emissions observed in conjugate region of Krasnodar Transmitter  Noticeable Doppler shift  Observation: L=2.3,  Transmitter (Krasnodar): L=1.78

15. 15 Propagation Modes  Emissions ducted end to end can be observed on the ground  ‘Hybrid’ Mode [Bell et al., JGR, 1983]: ducted waves observed after exiting duct and reflecting from ionosphere  Triggered emissions from non-ducted waves?  Use ray tracing and observed Doppler shift to determine trajectories

16. 16 Summary  1-Hop echoes regularly observed on the ground from Komsomolsk Alpha transmitter  Triggering of off-frequency emmisions not observed yet on the ground  DEMETER observes triggered emissions (off- frequency components) near all 3 Alpha transmitters  Future Work: Determine propagation paths for satellite observations, quantify conditions for wave growth using both ground and satellite observations