Very Low Frequency AstronomyOr how to observe at work on a cloudy day!

The Radio Spectrum

D Layer

E Layer

The Ionosphere

•VLF are opaque to the ionosphere

Therefore VLF Astronomy is by its nature an indirect method of observing

Quiet Sun

Low level of Sky-wave signal Vs. ground-wave

At Night

Erratic level of Sky-wave signal Vs. Constant ground-wave

Active Sun

High level of Sky-wave signal received during flare

Most people think radio astronomy think is complicated

Colin Clements 4Ghz Radio Telescope

But it doesn’t have to be...

Radio Equipment

Receiver Recorder PC

Antenna

Larger the betterMore turns the

better

I have three128 turns 400x400 square

tuned antenna25 turns 600mm Diameter

circle un-tuned150 turns 600mm diameter

circle untuned

Receiver Two approaches

1. radio receiver tuned to a specific station, outputs signal strength

2. PC sound card

RecorderTwo approaches

1. Data logger2. PC

My UKRAA VLF ReceiverAntenna

Aerial Tuning Unit

Receiver

Data logger/controller

Starbase Observatory Software

My Natural Radio Spectrum Set-up

Soundcard

Antenna

SpectrumLab FreewareRunning on an old laptopWin98 (first Edition)192MB RAMPentium II 400MHz processor6GB Harddisk

Live power spectrum, peaks are radio transmitters

Waterfall shows how the power changes with time

Up to 100 plotters can be set to record the power at specific

frequencies / bands of frequency

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

VLF receivers currently

monitored

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

Duration Importance

<18 min 1-

19-25 min 1

26-32 min 1+

33-45 min 2

46-85 min 2+

86 – 125 min 3

>126 min 3+

A text book SIDImportance = 2+2011-02-2812:46 – 12:54 – 13:48Corresponded to a M1 event

Increasing Energy

Typical Quiet Day

Transmitter is turned off at 07:00 – 08:00 every day

SID

Raw Data can be a little confusing

Removing signals after sunset and the signals that are not showing useful information can make it easier to

see what is going on.

SIDs come in many shapes

Res

ult

s

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

Future Projects for Radio Astronomy

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