Targeted VLF Wave-injection Experiments

Mark Gołkowski

MURI Review

Stanford University

February 18, 2009

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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 kHz12.65 kHz

L=2.61 L=1.97L=1.78

Resonant Energies: ~50-500 keV

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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

KangaroosStanford Scientists

Stanford ScientistsKangaroos

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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

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Example 1-Hop

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2

1A

Becc

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Temporal (non-linear) Growth

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Example Growth

~7-8 dB total

~70-80 dB/sec

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Example Growth

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Example Detection

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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

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Diurnal patterns

Day DayNight Day DayNight

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Average Daily Variations

Sunrise

Sunset

Tanaka et al. 1987 Stanford 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)

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DEMETER Observations (1)

NovosibirskKomsomolskKrasnodar

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

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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

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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

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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