Very Low Frequency Astronomy

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Very Low Frequency Astronomy

• Or how to observe at work on a cloudy day!

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The Radio Spectrum
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• The Ionosphere
• VLF are opaque to the ionosphere
• Therefore VLF Astronomy is by its nature an
  indirect method of observing

E Layer
D Layer
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Quiet Sun
Low level of Sky-wave signal Vs. ground-wave
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At Night
Erratic level of Sky-wave signal Vs. Constant
ground-wave
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Active Sun
High level of Sky-wave signal received during
flare
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Most people think radio astronomy think is
complicated
Colin Clements 4Ghz Radio Telescope
But it doesnt have to be...
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Radio Equipment
Antenna
Recorder
PC
Receiver
Larger the better More turns the better I have
three 128 turns 400x400 square tuned antenna 25
turns 600mm Diameter circle un-tuned 150 turns
600mm diameter circle untuned

• Receiver
• Two approaches
• radio receiver tuned to a specific station,
  outputs signal strength
• PC sound card

• Recorder
• Two approaches
• Data logger
• PC

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My UKRAA VLF Receiver
Antenna
Aerial Tuning Unit
Receiver
Data logger/controller
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Starbase Observatory Software
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My Natural Radio Spectrum Set-up
Antenna
Soundcard
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Live power spectrum, peaks are radio transmitters
Waterfall shows how the power changes with time
SpectrumLab Freeware Running on an old
laptop Win98 (first Edition) 192MB RAM Pentium II
400MHz processor 6GB Harddisk
Up to 100 plotters can be set to record the power
at specific frequencies / bands of frequency
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Radio Stations

• 19.6kHz GBZ, Anthorn,UK
• 20.27kHz ICV, Isola di Tavolara, Italy
• 20.9kHz FTA, Sainte-Assise, France
• 21.75kHz HWU, Rosnay, France
• 22.1kHz GQD, 22,.1kHz Skelton, UK
• 23.4kHz DHO38 Rhauderfehn, Germany
• 24Khz NAA, Cutler, Maine, USA
• 37.5kHz, NRK/TFK Grindavik, Iceland
• 62.6kHz, La Regine, France
• 81kHz, Inskip, UK

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VLF receivers currently monitored
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Recording Interpreting Results

• Amplitude of event
• Corresponds (usually) to the flare class, but
  will be specific to conditions and observer
• Start, Peak End of event
• Recorded as an importance level

Class Energy
X 10-4-10-3W/m2
M 10-5-10-4W/m2
C 10-6-10-5W/m2
B 10-7-10-6W/m2
A 10-8-10-7W/m2
Increasing Energy
A text book SID Importance 2 2011-02-28 1246
1254 1348 Corresponded to a M1 event
Duration Importance
lt18 min 1-
19-25 min 1
26-32 min 1
33-45 min 2
46-85 min 2
86 125 min 3
gt126 min 3
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Typical Quiet Day
Transmitter is turned off at 0700 0800 every
day
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SID
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Raw Data can be a little confusing
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Removing signals after sunset and the signals
that are not showing useful information can make
it easier to see what is going on.
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SIDs come in many shapes
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Results
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Next Steps for VLF

• Get laptop set-up in shed and connected via wifi
  to main PC
• Get lap-top controlling UKRAA controller
• Build VLF set-up for CMHAS observatory
• Experiment with different antenna configurations
• Automate logging and access via web

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Future Projects for Radio Astronomy

• Meteor Detection
• Solar activity monitor (21Mhz)
• Radio Jove (21Mhz)
• Radio Imaging