Jagiellonian University Faculty of Physics, Astronomy and Applied Computer Science Joanna Kozakiewicz Investigation of the Martian subsurface by analysis of the Schumann resonance parameters A dissertation submitted to the Jagiellonian University for the degree of Doctor of Philosophy PhD Advisor: Prof. Katarzyna Otmianowska-Mazur Krakow 2015 Abstract Two electrically conductive planetary spheres, the ionosphere and the ground, form a spherical waveguide. Within such a planetary cavity a phenomenon called Schumann resonance (SR) can occur. It is a resonance of extremely low frequency (ELF) electromagnetic waves. The resonance parameters are strongly related to the electromagnetic properties of the cavity. On Mars, a low- conductivity ground significantly influences ELF wave propagation. For that reason, a newly developed analytical method, which enables to estimate the Schumann resonance parameters and explicate their dependence of the ground properties, is introduced. The obtained results indicate that the influence of the Martian ground on the SR parameters is important. As a result, Schumann resonance can be used as a tool to study, not only the properties of the Martian atmosphere, but also the properties of the subsurface layers. Schumann resonance may be especially useful in groundwater exploration. Key words: Schumann resonance radio waves subsurface of Mars 1 Abstrakt Dwie elektrycznie przewodzące sfery planetarne, jonosfera i grunt, tworzą kulisty falowód. W takiej wnęce planetarnej może wystąpić zjawisko zwane rezonansem Schumanna (SR). Jest to rezonans fal elektromagnetycznych o bardzo niskich częstotliwościach (ELF), którego parametry są ściśle związane z właściwościami elektromagnetycznymi wnęki. Na Marsie, słabo przewodzący grunt znacząco wpływa na propagację fal ELF. Z tego powodu wprowadzona została metoda analityczna, pozwalająca na oszacowanie parametrów rezonansu Schumanna i ich zależności od właściwości gruntu. Uzyskane wyniki wskazują, że wpływ gruntu marsjańskiego na parametry SR jest ważny. Dzięki temu rezonans Schumanna może być zastosowany jako narzędzie do badania, nie tylko właściwości marsjańskiej atmosfery, ale także warstw podpowierzchniowych. Rezonans Schumanna może być szczególnie przydatny w poszukiwaniu wody pod powierzchnią Marsa. Słowa kluczowe: rezonans Schumanna fale radiowe podpowierzchnia Marsa 2 Acknowledgments This work would not have been finished without help of many people. I am especially grateful to PhD Andrzej Kułak for the opportunity to study this interesting subject of the Schumann resonance phenomenon and for his help and support during my research. I wish to express my gratitude to my PhD advisor Prof. Katrzyna Otmianowska-Mazur and my supervisor Prof. Bogusław Kamys for the possibility to develop my interest in planetary science. I am also grateful to PhD Ewa Malata for creating the opportunity to study geology. I would like to thank Krzysztof Zietara for the discussion and remarks connected to the ELF station design and for the 3D visualization of the Martian platform. I wish to thank PhD Earle R. Williams for useful guidelines and to PhD Marian Soida for his helpful comments on the text of my PhD thesis. I wish to express my gratitude to two people: Anna Stec and Marta Sieprawska-Winkel without whose administrative support I would not be able to begin and complete my work. This work was supported in part by the Polish Ministry of Science and Higher Education under subsidy for research and development of young researchers and PhD students, and in part by the Polish National Center for Research and Development Grants: NCN-2013/09/N/ST9/02200. 3 Table of Contents Introduction ............................................................................................... 6 1 Schumann resonance and ELF propagation in a planetary cavity.......... 9 1.1 Historical background....................................................................................................... 9 1.2 Theoretical background.................................................................................................. 11 1.2.2 Introduction to ELF propagation modeling ................................................................ 18 1.2.3 Analytical modeling of ELF propagation..................................................................... 21 1.2.4 Properties of a planetary cavity ................................................................................. 26 1.2.4.1 Low-frequency EM sources................................................................................ 28 1.2.4.2 Electrical properties of the atmosphere............................................................ 30 1.2.4.3 Electrical properties of the ground.................................................................... 36 2 Martian Environment..........................................................................38 2.1 Mars exploration............................................................................................................. 38 2.2 Orbital and global parameters........................................................................................ 40 2.3 Magnetosphere .............................................................................................................. 44 2.4 Atmosphere .................................................................................................................... 48 2.4.1 Ionosphere.................................................................................................................. 51 2.4.2 Electrical properties of the lower atmosphere .......................................................... 58 2.4.2.1 Electron densities .............................................................................................. 59 2.4.2.2 Conductivity profiles.......................................................................................... 61 2.4.3 ELF sources in the atmosphere .................................................................................. 63 2.4.3.1 Martian dust ...................................................................................................... 66 2.4.3.2 Charging mechanism ......................................................................................... 67 2.4.3.3 Electric field generation in saltation.................................................................. 69 2.4.3.4 Electric field generation in dust storms............................................................. 70 2.4.3.5 Electric field generation in dust devils............................................................... 72 2.4.3.6 Global atmospheric electric circuit.................................................................... 74 2.4.3.7 Radio emission from the Martian sources......................................................... 76 2.5 Ground............................................................................................................................ 77 3 Modeling of ELF propagation in the Martian waveguide .....................88 3.1 Modeling of the ground electrical properties ................................................................ 88 3.2 Modeling of the Martian waveguide ............................................................................ 101 3.2.1 Electric models of the atmosphere .......................................................................... 101 3.2.2 Electrical models of the ground ............................................................................... 104 3.3 Analytical modeling with a multi-layer ground ............................................................ 107 3.3.1 Three-layer modeling ............................................................................................... 108 3.3.2 Two-layer modeling.................................................................................................. 111 3.3.3 One-layer modeling.................................................................................................. 111 4 Schumann resonance and ELF propagation parameters on Mars ......113 4.1 Previous studies on Schumann resonance on Mars..................................................... 113 4.2 Schumann resonance parameters with a multi-layer ground...................................... 115 4.3 Propagation parameters with a multi-layer ground..................................................... 119 4.4 Discussion of the results ............................................................................................... 121 5 The ELF experiment on Mars.............................................................129 5.1 Electrical activity investigation on Mars....................................................................... 129 5.1.1 Remote sensing measurements ............................................................................... 129 5.1.2 In situ measurements............................................................................................... 130 5.2 ELF measurements on Earth......................................................................................... 131 4 5.3 Objectives and description of the Martian experiment ............................................... 132 5.3.1 Objectives................................................................................................................. 133 5.3.2 Description of the measuring system....................................................................... 133 5.3.3 Martian platform description..................................................................................