General Meeting Report 11 July
Lockie Cresswell and Stewart Southam speak on
Magnetometry, Space-Weather and the Square Kilometre Array
Lockie is a physicist/geologist who has spent 23 years working in a scientific laboratory measuring all manner of forces. He is a Director of RF Probes, Senior Consultant for Microforce, and Chairman of the Australian Standard Committee for Car Alarms and Engine Immobilizers. His hobbies include astronomy, radio astronomy, amateur radio, electronics, computing, rf instrumentation and physics.
It was through the engineering challenges of the Radio Astronomers Group’s oversize Telstra Dish project that I first became aware of Lockie’s many-faceted nature ( ASV General Meeting July 2000). Lockie believes that the measurement of unseen forces is a challenge to both scientific methodology and engineering: Science builds upon tested theories of the past guided by good engineering and scientific practice to develop new observational techniques and, hence, acquire new observations or data about the universe.
In physics, a force is anything that can cause a mass-particle or body to accelerate, rotate, deform or stress. First mentioned by Archimedes in the 3rd century BC it was mathematically defined as the rate of change of the momentum of a body by Isaac Newton in the 17th century. Later, with the development of quantum field theory and general relativity it was realized that “force” is actually a redundant concept, better understood as fundamental interactions.
Lockie’s presentation for the evening centred on one unique observational technique, Magnetometry, and on his experiences and experiments in this field. A magnetometer is a scientific instrument used to measure the strength and/or direction of the magnetic field in the vicinity of the instrument. Once calibrated to the prevailing local field (normally the Earth magnetic lines) it can detect minute variations in that field. There are six general types of magnetometers: The Jam-jar; the Hall-effect; the Cesium vapour beam; the Proton precession; the Flux gate and the Squid device. All of them are capable of measuring down to sub-nano Tesla (millionths of Earth’s magnetic field strength) fluctuations. Lockie’s early experiments included detecting distant trains and other vehicles. An astronomical application is the detection of changes in the Earth’s magnetic field due to changes in the Solar wind caused by massive eruptions (flares) on the Sun. Solar flares emit vast quantities of high energy electromagnetic radiation and ionized particles that can play havoc with electronic equipment and communication systems on Earth. A magnetometry set-up can thus serve as a ”Space Weather” early warning system.
Magnetometers are sometimes called gaussmeter, in honour of Carl Friedrich Gauss who, in 1833 published a paper on “The intensity of the Earth’s magnetic fields expressed in absolute measure” in which he described a new instrument consisting of a bar-magnet suspended on a gold fibre
My own experience with magnetometers was in the late 1960s when we tried to use them as vehicle detectors or counters on traffic lights. Beer-can detectors we used call them, due to their distinctive shape. Following extensive testing they proved unsatisfactory for our application because their sensitivity range could not be focussed on individual traffic lanes. If set to reliably detect small motorbikes in a turning lane, the unit would also be triggered by big trucks in the adjacent lanes going straight ahead. An inductive Loop Detector was superior in that regard and has been used in all traffic light installations ever since.
Stewart Southam spoke about the controversial Square Kilometre Array. The SKA is a $2bn+ proposed directional radio telescope system consisting of 100 stations, each with 100 x 10m dishes, totalling an effective one million square metres of collecting area. Operating as an Interferometer at wavelengths from 3m down to 1cm it will have unprecedented accuracy. It will be the biggest and most sensitive radio telescope ever built. In fact it will be the largest scientific facility on Earth. Its potential scientific uses are almost limitless and include investigations into strong-field tests of gravity, cosmology and galactic evolution, probing the Dark Age and the formation of the first stars, search for extra-terrestrial intelligence (SETI) and investigating proto-planetary disks. Of the four countries in the Southern Hemisphere originally considered, only South Africa and Australia are still in the running. The central site in Australia will be Mileura near Meekatharra, where 5000 dishes will be placed in a 5km wide, seven arm spiral.
The SKA is seen as the future in radio cosmology and will be a boost to the Australian economy, technology, science and industry.
The Feature Telescope for the night was presented by Clint Jeffrey, another member of the Radio Astronomy Group. Presenting some of the plumbing and hardware that go into making useful antennae he also spoke of the Jupiter monitoring project “JOVE” with three nominated receiver sites
at Officer, Arthurs Creek and Murchison, and future projects to co-relate solar flare radio frequency output with magnetometer measurements. Radio Jove is part of a world-wide project.
All in all an information-packed evening, that stretched out late into the night. Alfred Klink