Embed Size (px)
Citation preview
Wave Injection at Low Latitudes
Mark Golkowski
Remediation of Enhanced Radiation Belts Workshop
Lake Arrowhead, CA
March 3-6, 2007
2
Adelaide, Australia
~500 kW ? Navigation transmitter in Komsomolsk na Amur in Russian far east (400 msec pulses) at L = 2
Conjugate point in southern Australia
Stanford University receiver since January 2007
Explore and quantify wave-growth
Stanford Scientists Kangaroos
3
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
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
Example 1-Hop
2
2
1A
Becc
6
Temporal (non-linear) Growth
7
Example Growth
~7-8 dB total
~70-80 dB/sec
8
Example Growth
9
Example Detection
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
Diurnal patterns
Day DayNight Day DayNight
12
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)
13
Summary
1-Hop echoes regularly observed from Komsomolsk Alpha transmitter
Echoes exhibit temporal growth of ~70-80 dB/sec Propagation delays of 460 msec – 540msec
equatorial electron concentrations of 4000-5000 cm-3 at L = 2
Triggered of frequency emmisions not observed yet, except perhaps on DEMETER satellite
Diurnal variations likely result from propagation/ducting effects
Future Work: statistically quantify effect of geomagnetic conditions on wave growth
