Science Project to study Solar Terrestrial Physics September – December 2010

Radio & X Ray observations of the Sun We will build a radio receiver that can give us information on the X Rays emitted from the Sun We will learn about the Physics of the Sun, interplanetary space, and the impact of X rays and the Solar Wind on the earth. We will set up a 24/7 observing programme and use software to analyse data

Radio & X Ray observations of the Sun

Solar Terrestrial Environment Physics PROJECT STEP - Monmouth Boys School (Sept – Dec 2010) STEPSTEP

Radio & X Ray observations of the Sun The project will have a number of stages: –Introduction to Solar – Terrestrial Physics –Building a suitable radio receiver –Testing & calibrating the receiver –Monitoring & analysis software –Observing & logging data –Data analysis & physical insights –Comparing with Satellite data –Setting up an observing programme

Introduction to Solar – Terrestrial Physics The introduction will cover: –The Solar – Terrestrial environment –The Earths Ionosphere & Magnetosphere –Effects of Solar X rays on the Ionosphere –Using Military Transmitters as probes –The electronics needed –The software required –Examples of what will be observed –Comparing with Satellite Data

Our Sun The Sun is a gravitationally bound nuclear reactor It is largely stable, but has some variability There is the 11year sunspot cycle Strong magnetic fields wind up around the equator as the Sun spins The field lines SNAP and trapped energy is thrown into space year

Sun spins faster at the equator Field lines get twisted with differential rotation Field lines dragged along equator Lines get wound up like an elastic band Eventually the lines ‘snap’ and release stored energy

Solar instabilities - flares Sun rotates once every 27 days Flares last minutes or hours Notice the ‘flashes’

Solar Flares When the flare occurs the changing magnetic fields propel millions of tons of charged particles into space Sometimes in the direction of the Earth Energetic X Rays are also emitted & travel at the speed of light This ‘prompt’ radiation reaches earth in ~ 9 minutes – particles take several hours or days

Production of hard X rays in magnetic ‘pinch’ Sun spot fields make X rays reconnection flare loop material ejected into space ‘pinch’ constriction Surface of Sun Magnetic field lines sun spot From Kanya Kusano JAMSTEC

Solar Flares The fast particles first encounter the Earths Magnetosphere at up to 10x the radius of the Earth & form a shock wave boundary Charged particles cannot cross field lines – they travel around & along them

Earth’s Magnetic Field The magnetic field of the Earth is thought to be generated in the rotating molten iron core Without the Solar wind it would be a Dipolar Field - like a bar magnet

Earth’s Magnetosphere Configuration of magnetic fields in the Magnetosphere

Magnetically neutral Polar Cusps Charged particles can flow into the Polar Cusps Can flow down into the Atmosphere Charged particles H H

Particles create an aurora in Polar regions Example of Aurora Borealis in Alaska

Aurora are almost symmetrical around poles Auroral Oval – Aurora Australis 11/9/2005

Magnetosphere is like a ‘jelly’ Magnetosphere is compressed by impact of solar particles & vibrates or wobbles Particles Earth’s magnetic field Horizontal (x) Horizontal (y) 3- 4 / 8/ 2010 Solar Particles hit BAA (RAG) 2010

X Rays from the Sun X rays are very energetic photons Produced when electrons are accelerated very rapidly when solar magnetic field ‘snaps’ Travel at light speed to Earth 9 minutes

X rays penetrate the Magnetosphere X rays are not charged – they can penetrate magnetic fields When they reach the earth they pass through the Magnetosphere into the Ionosphere They only start to interact with the atmosphere when it becomes dense enough 100km altitude

Diurnal solar energy deposition in ionosphere UV and X rays ionise the day side ionosphere

The Ionosphere Consists of layers of charged particles – Plasma in bands at various heights Some layers disappear at night when solar UV energy is cut off These plasma layers reflect radio waves from surface of the earth Low frequency waves cannot pass through D Region

What is a Plasma ? Plasma is the name given to matter that is ionised It is neutral in bulk but is composed of electrons & ions and neutral atoms The electrons can react to radio waves The electrons take in energy and speed up Energy is taken back by collisions with neutral atoms and ions & released as heat Positive ion - electron Neutral atom

Radio wave propagation In daytime the LW & MW signals are reflected and ABSORBED At night the plasma density is less and the waves are preferentially reflected Propagation through a plasma depends on two things: –Electron density –Collisions with neutrals Both vary with plasma density & height

Radio waves & reflecting plasma layers Height and density of layers varies diurnally & with sunspot cycle – function of input energy from Sun We will look in some detail at the D region & Very Low Frequency waves

High frequencies escape – low are reflected Low frequency waves are reflected Direct signal partly blocked by curvature of the earth

VLF reflection from D Region VLF radio waves are reflected by the D Region Bottom of D 90km Transmitter Receiver

Location of Military VLF transmitters Used to communicate with Naval ships & submarines Low frequencies travel around the world & penetrate water NAA 24kHz GBZ 19.6kHz ICV 20.27kHz JXN 16.4kHz QUFE 18.1kHz DHO 23.4kHz GQD 22.1kHz HWU 18.3kHz

Frequencies of VLF Military transmitters GBZ DHO GQD NAA UFQE Military transmitters 15 – 24kHz JXN Radio Spectrum 15 to 24kHz

Dependence on height of reflecting layer The reflection point depends on h & D The height ‘h’ depends on the plasma density receiver h D

Using the ionosphere as a X ray detector The plasma density depends on the input energy – UV and Xrays X rays ionise the D region and increase the plasma density The D region gets thicker & the base moves to lower altitude The reflection geometry changes ! Signals from the VLF transmitters change !

The outcome The Earth’s ionosphere can be used as a SOLAR X RAY DETECTOR There is an additional path length for the sky wave When summed with the ground wave we get an interference pattern between the two waves that depends on ‘h’

Calculating signal strength with height of D region Difference in path length between sky & ground wave is just L-D Giving a phase difference in Radians of : Add in phase inversion on reflection From eqn. 1 – 3 we can calculate received signal strength as a function of height ‘H’ Work by Mark Edwards

Calculation of VLF signal 19.6kHz Signal Strength D region height km 78km 71km calculated Signal Strength measured Diurnal variation of VLF signal Strength

Evidence of X ray impact - S.I.D. Sudden Ionospheric Disturbance (SID) due to Solar X ray flares Normal diurnal variation shown in blue Two SID events just after mid day Characteristic ‘shark fin’ shape Measured VLF signal level SIDs ~ I day

Practical value of monitoring Solar –Terrestrial Environment LEO GEO Solar generated Geomagnetic storms kill sensitive satellites in Low Earth Orbit and in Geostationary orbits Large scale power grids have been overloaded by surges on long power lines caused by geomagnetic storms

Building a receiver Requires an antenna-a loop aerial An amplifier-high gain & wide band A waveform digitiser- computer sound card Spectrum analyser-Fourier software Data logger-data file software Graph plotter-graphing software Data analysis-Microsoft XL We will build a couple of receivers and set up a SID Monitoring Station in Monmouth In future we may connect it to the internet

Basic layout of VLF receiver Loop Antenna 1m x 1m High Gain Amplifier PC with sound card Display Spectrum Lab software

pegs to wind coil around coil – 40 turns central wooden support wooden bracing arms wooden joining plate fixing screws pole in ground or fixed to tripod slips inside hole Receiving Antenna 1m x 1m

1m Approx 40 turns (~200m wire) Terminal block Coaxial cable 10nF +V -V 0V 1k 33k CA k 100k CA3140 output input ~33x Gain Amplifier ~3x Gain Amplifier X1 Gain Buffer Initial VLF Receiver Amplifier (Gain ~ 333x or 50dB) +6 to +12V -6 to -12V uF Buffered output + The 10k trim pot is used to adjust the offset null The buffer output stage is only required if using > 50m of output coaxial cable k Gain=33xGain=10x IC1 IC2 High gain Amplifier

Amplifier construction ground -ve rail +ve rail 10 trim pot IC1 IC2 notch In Output WIRING LAYOUT OF INITIAL APMLIFIER BOARD

Output from Spectrum Lab software Typical Spectrum of Received Signal 0 to 24kHz Frequency Hz Signal Level dB 40dB or X 100 VLF Transmitting stations general man made radio noise (mains) * Typical voltage from resonant antenna = 0.14mV rms *

Time (hours) Signal Strength dB) A plot of 10 VLF transmitter signal strengths as a function of time Graph plotting software

SID captured on 12 th June 2010

Live Satellite data To confirm a true SID we need X Ray flux data This can be obtained from the GOES satellite Near real time download via the internet

Solar X ray burst - generates SID Solar X Ray burst - GOES spacecraft

STEREO satellite - multi wavelength pictures of Sun Two spacecraft STEREO (ahead) & STEREO (behind) Together give 3D data on Solar activity

Solar Dynamic Observer satellite SDO view of Sun on 13/7/2010 SDO Generates high definition movies of Solar activity

Comparing our results SID monitoring site in Italy Enables us to compare our results We need to collect data every day and log all results Can give talks at Astronomical society meetings GOES 14 X Ray Flux Time of day SID

We will have a working system by Christmas Massive flare on limb of Sun

Start building next time