Journal of the Royal Society of Western Australia ISSN 0035-922X CONTENTS Page REVIEW PAPER Plasma physics: an introductory survey B J Green RESEARCH PAPER Geomorphology of pit gnammas in southwestern Australia B V Timms RESEARCH NOTES Meclianism and effects of silencing green peach aphid genes via RNA interference V Bilgi, J Fosu-Nyarko & M G K Jones 17 Distribution, abundance and bioerosion of the grazing sea urchin Echinometra mathaei at Ningaloo Marine Park, Western Australia M W Langdon, M van Keulen & E I Paling 19 Palynology of the southern Gunbarrel Basin C Mack 21 Nutritional risk in children with cystic fibrosis is associated with reduced lung function, pancreatic insufficiency and gender L Rosser, D Bryant, K Josh, T O'Sullivan, P Lyons-Wall & A Devine 23 The birds and the bees and the Banksia mating trees: measuring the success of Banksia woodland restoration using genetic and ecological markers A Ritchie, S Krauss, P Nevill, E A Sinclair & K Dixon 25 BOOK REVIEWS A Beginners Guide to Diatoms by Jacob John Reviewed by A Kemp 27 OBITUARIES John Robert De Laeter 1933-2010 29 Gillian Perry (nee Jenkins) 1943-2011 31 Lindsay James Peet 1939-2012 33 Alec Francis Trendall 1928-2013 35 EDITOR'S NOTE 39 Volume 96 Part 1 July 2013 To promote and foster science in Western Australia Patron Her Majesty the Queen Vice-Patrons His Excellency Mr Malcolm J McCusker, AC CVO QC Governor of Western Australia Professor Lyn Beazley AO FTSE MA PhD COUNCIL 2013-2015 President H Bekle Hon Editor A E Cockbain Immediate Past President P O'Brien Hon Librarian Vice-President K Trinajstic Journal Manager M Gallegos Vice-President W A Loneragan Councillors Hon Secretaries A W R Bevan Council L Milne L Collins Membership J Rosser C Florides Proceedings M Gallegos D W Haig Hon Treasurer P O'Brien S Toby EDITORIAL BOARD 2013-2015 Editor-in-chief K A Haskard, Data Analysis Australia A E Cockbain, South Perth P Ladd, Murdoch University Associate Editors D Laird, Murdoch University H Bekle, Notre Dame University K Trinajstic, Curtin University A Bevan, Western Australian Museum M Van Keulen, Murdoch University R Davis, Edith Cowan University K Wright, Curtin University The Royal Society of Western Australia was founded in 1914. 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The Journal of the Royal Society of Western Australia was first published in 1915. Its circulation exceeds 650 copies. Nearly 100 of these are distributed to institutions or societies elsewhere in Australia. A further 300 copies circulate to more than 40 countries. The Society also has over 350 personal members, most of whom are scientists working in Western Australia. The Journal is indexed and abstracted internationally. Cover design: The four subjects symbolize the diversity of sciences embraced by the Royal Society of Western Australia. Mangles' kangaroo paw {Anigozanthos ma7iglesii) and the numbat (Myrmecobius fasciatus) are the floral and faunal emblems of Western Australia, and stromatolites are of particular significance in Western Australian geology (artwork: Jan Taylor). Tlie Gogo Fish (Mcnamaraspis kaprios) is the fossil emblem of Western Australia (artwork: Danielle West after an original by John Long). Journal of the Royal Society of Western Australia, 96:1-6, 2013 Plasma physics: an introductory survey B J GREEN School of Physics, University of Western Australia, 35 Stirling Highway, Crawley, WA 6009, This paper describes what plasmas are, why their study is essential to our understanding of the universe, how plasma physics is applied to many scientific and technological areas of development, and how it possibly could provide the solution to the world's energy problems. In addition, the paper will briefly describe Australia's involvement in this research and development area. KEYWORDS: fusion energy, fusion reactions, nucleosynthesis, physics, plasmas. WHAT IS A PLASMA? Why the term 'plasma' was used is unclear. One explanation does involve the similarity with blood A plasma is an ionised gas in which the nearest plasma (both carry particles), while another explanation neighbour interactions between the electrically-charged refers to the Greek word meaning 'anything moulded or constituents (negatively-charged electrons and positively- formed', since plasma usually moulds itself to the shape charged ions, which are in equal numbers so as to of its container. Plasma physicists have, ever since, had maintain overall electrical neutrality) is dominated by the to clarify this issue, and in most cases, to express an long-range interactions of many 'distant' particles. In ignorance of the properties of blood plasma! fact, many plasmas contain a significant number of un¬ ionised neutral atoms, but the long-range interactions In 1920, A S Eddington realised that from atomic mass dominate. determinations made by F W Aston it is possible that hydrogen can be converted to helium (by the fusion or The force (F) between isolated point electrical charges joining together of the hydrogen nuclei) under the right Cj and Cj which are separated by a distance r is conditions, and that this could be the origin of the source F = (e,e2)/(4rre/) (1) of energy for all stars, in particular the sun. G Gamow, in 1928 derived (using quantum mechanics) the formula for where e„ is the permittivity of a vacuum. This is the so- the fusion of two nuclei with the associated release of called Coulomb interaction, and because it falls off energy (as matter and energy are equivalent according to relatively slowly with distance r, is a 'long-range' one Einstein). R Atkinson and F G Houtermans (in 1929) then compared to the shorter range forces between the used Gamow's results to calculate the rate of energy particles which are constituents of the three other forms production arising from thermonuclear fusion reactions of matter—solid, liquid and gas. A plasma has been in hydrogen plasma in stellar cores. H Bethe (in 1939), termed 'the fourth state of matter', because it has elucidated the processes whereby the energy of stars is properties which are quite distinctive. produced, for which he received the 1967 Nobel Prize in As electrically-charged particles are constituents of a Physics. This theory worked well for stars with masses plasma, the plasma can conduct electrical currents, it can up to about the mass of the sun. In 1938, C F von be influenced by electric and magnetic fields, and Weizsecker identified processes which were important in currents flowing in the plasma generate magnetic fields. more massive stars. The study of the creation of heavier Plasma can support a whole range of wave motions. nuclei in such fusion processes was initiated by F Hoyle In fact, the above (classical) definition of plasma has in 1946. Tliis interesting story is described in more detail been extended to other situations where plasma in the history section of the Wikipedia article on properties can still be found, e.g. non-electrically neutral nucleosynthesis (http://en.wikipedia.org/wiki/ situations. Stellar_nucleosynthesis). Nucleosynthesis is the formation of the chemical elements by nuclear reactions occurring in the cores of stars. Fusion is thus a BRIEF HISTORY OF PLASMA PHYSICS fundamental process in the establishment and maintenance of the universe. Plasma was first identified as a 'different' state of matter The first fusion reactions performed in the laboratory in the study of low-density ionised gases, which were were carried out by the 'fathers of fusion' M Oliphant, P formed in electrical discharge tubes (Crookes 1879). The Harteck and E Rutherford in the early 1930s (Oliphant et term 'plasma' was introduced by Langmuir (1928) and «1.1934). Tonks &Langmuir (1929) in connection with their studies of oscillations of ionised gases. Such oscillations (which today we refer to as plasma oscillations) are due to the ABUNDANCE OF PLASMA strong restoring electrical forces that act whenever there are charge separations, as can occur as a result of thermal Plasma is the most common state of visible matter in the fluctuations. entire universe. It is estimated that over 99% of the visible matter in the universe is in the plasma state (Figure la) e.g. intergalactic medium, interstellar medium, and the © Royal Society of Western Australia 2013 solar system [the sun (Figure lb), the solar wind and the 1 Journal of the Royal Society of Western Australia, 96(1), July 2013 (a) (b) PLASMAS-THE 4^*' STATE OF MATTER Number Density (Charged Particles / m^) Figure 1 (a) This shows different plasmas in terms of their temperature in K, and the number density (no. of charged particles/m^). The range of temperatures spans more than six orders of magnitude, while the number density spans more than 30 orders of magnitude. <http://fusedweb.pppl.gOv/cpep/chart_pages/5.plasma4statematter.html>. (b) Tire sun—a functioning fusion reactor, (c) Lightning, a dramatic natural, terrestrial, plasma occurrence, (d) The interior of the JET tokamak. The infrared camera reveals the heat loads on the wall and sometimes the radiation from the very cold areas of the plasma.