Investigation of Jovian Radio Emissions
A dual dipole array radio telescope was assembled to investigate decametric radio emissions from Jupiter. The project aims to investigate the emissions characteristics. The thesis starts with explanation of radiation and astronomical aspects of Jupiter but places emphasis on how the processes in the magnetosphere creates observable radio emissions. In particular, Io influences on radio signals were considered. The procedure of radio telescope assembly and key methods for noise prediction and analysis is determined. Selected datasets were qualitatively analysed and statistics concluded. The project took place at the Concord Research Labs, supervised by Dr M. Wild.
What did I want to achieve?
In this project, I plan to identify the type of observable Jovian Radio Emissions.
In my independent research, I aim to study the background information for Radio Astronomy, such as types of radiations; Jupiter’s planetary properties, such as the composition, size and different orbital satellites; Processes that induces the radio emissions, such as the interaction between the Magnetosphere and Io; Factors that influence the radio emissions, such as the Ionosphere.
In the Concord Research Lab, I aim to set up a dual dipole antenna radio telescope at a suitable site location and calibrate electronic components in the radio receiver. A suitable length for the coaxial transmission cable will be determined by calculations. Preliminary experiments and observations will be conducted to indicate areas of improvement before the main investigation.
In my independent time, I aim to develop necessary software skills. Softwares will be needed for radio bursts prediction, data recording from the radio telescope. If possible, variables will be investigated alongside the radio data. Characteristics of radio bursts should be qualitatively described and, if possible, statistically analysed to reach a conclusion.
Being 318 times more massive than the Earth and 2.5 times the mass of all other planets combined, Jupiter is the largest planet in the Solar System. Its large volume and low density contributes to vigorous chemical reactions between the constituents gases such as methane, ammonia, silicon oxides. Over more, Jupiter has the most moons in the solar system, up to 69 known ‘natural satellites’.
A magnetosphere is a large electromagnetic field which causes charged particles in the surrounding of planets or celestial bodies to be influenced by the field. Jupiter’s inner magnetosphere is the source for shortwave signals – cyclotron radiation – which is a type of decametric radio emissions. The inner magnetosphere contains trapped clouds of charged particles which experiences a strong Lorentz force induced by the magnetic field. When the electron is moving perpendicularly across the field, it will be deflected into a circular orbit. As the electrons enter magnetic field at an angle, they move in a spiral pattern towards the poles.
This is the process that forms planetary radiation belts of dense electron clouds, doughnut-shaped torodial regions centred on the magnetic equator. Very high-speed relativistic electrons spiralling around Jupiter’s magnetic field lines create the glow on Jupiter.
Jupiter’s decametric emissions can be divided into two types, L-bursts and S-bursts, each bursts lasting for a few minutes.
- L-bursts – long duration signals that sound like the “swoosh of ocean waves breaking up against a shoreline”.
- S-bursts – short duration signals that sound like the “crackling of a campfire”.
Originated from different latitudes, Io-A, Io-B, and Io-C, are observed at 20 MHz, the optimum frequency due to the Earth Ionosphere (layer of ionised gas 60 to 1000km above the surface of the Earth) influencing the passage of radio waves.
I self-assembled a dual dipole radio telescope. Each of the dipole antenna consists of two pieces of wire and three insulators, where the signals from two dipole are combined by the power combiner. Due to Jupiter being at the southern angle, signals will arrive on the southern dipole first, therefore by adding an extra length of coaxial cable, 135º, running from the south dipole to the power combiner, an intentional phase difference between the two signals will cause the resultant to be phase and twice the gain of the celestial radio signal. To maximise the beaming pattern at Acton Burnell, 52.6152° N 2.6940° W, the height of the antenna was tailored to 15 feet.
Results and Conclusion
In the 33 days of investigation, I concluded that Io A events has the highest probability in occurring (21 times) while Io C has the lowest (5 times). While Io A events occurs periodically, peaking at around 130-150 minutes once every week, Io C events occurs rather randomly.
Furthermore, there may be positive correlation between the occurrences of Io A and Io C events, suggested by the product moment correlation coefficient of 0.685.
Io B events occurs periodically, peaking at around 120 minutes once every week, occurred 9 times in the 33 days investigation, however, it does not correlate with either Io A or Io C events.
Future possibilities may include correlating the radio data with the local listening conditions. Rain precipitation could be a variable that affects the collection of radio signals.