Preface

Abstract

Earth is a complex dynamic system and study of the geomagnetic field can provide<br />insight to the dynamic processes operative in the outer core where the main field is<br />produced by a geo-dynamo mechanism. By contrast the study of transient geomagnetic<br />variations is an important tool for studying the complex solar wind-magnetosphere-<br />ionosphere coupling. In addition the currents induced by the time varying external<br />current system allow us to image the crust and the upper mantle in terms of<br />electric conductivity. Lack of measurements and collection of geomagnetic data from<br />certain strategic locations restricts the development of high quality models of main<br />geomagnetic field as well as the current systems responsible for transient geomagnetic<br />variations. Division V of the International Association of Geomagnetic Aeronomy<br />(IAGA) jointly with the Interdivisional Commission for Developing Countries organized<br />a special symposium «Geomagnetic Measurements in Remote Regions» at General<br />Assembly of IUGG held at Perugia (Italy) during July 2-12, 2007. Papers were<br />presented on data base numerical simulations identifying strategic gaps in the existing<br />observatory network where new measurements of geomagnetic field could improve<br />upon existing geomagnetic reference models. Special focus was on describing the<br />novel design of equipment, modes of data collection and dissemination from remote<br />regions. During the symposium, 21 presentations were presented and this issue of<br />Annals of Geophysics compiles a selection of papers.<br />It is significant that each paper in this special issue is multi-authored by several<br />institutions and countries. This emphasizes the importance of worldwide collaboration<br />when obtaining and analyzing data from geophysical observations in remote regions.<br />With current technology magnetic observatories still require people to take measurements<br />at least once per week to enable baselines to be established and must be<br />away from power sources and transmission lines. This restricts the location of magnetic<br />observatories used for deep Earth investigations. However, presented here are<br />papers describing ways to overcome harsh conditions and obtain magnetic data in<br />remote locations. The need for long term ground based geomagnetic observatories<br />for reference models is well established and discussed. Also discussed, is the study<br />of magnetic field variations for determining transient phenomena. The measuring<br />stations can exist unmanned as highlighted during the session by the Japanese group (not included in this volume) and Chambodut et al.<br />Five papers (Cafarella et al., Chambodut et al., De Lauretis et al., Maksymchuk<br />et al., and Torta et al.) describe magnetic observations in Antarctica. Most of this<br />continent is covered by ice so it is almost impossible to sample the continental surface<br />directly: magnetic exploration allows us to overcome much of this problem, providing<br />important information on the geological and tectonic settings of this continent.<br />Antarctica is also an interesting magnetic region because it is in darkness for<br />half of the year, so production of the ionospheric plasma that creates the daily Solar<br />quiet variation is reduced for this period in this region (Chambodut et al.). In addition,<br />it contains the southern polar cap current system – a window to the solar wind<br />and the magnetospheric-ionospheric energy transfer processes (De Lauretis et al.).<br />Torta et al. and Chambodut et al. describe the exceptional means necessary for a<br />magnetic observatory in Antarctica attempting to attain INTERMAGNET status. Torta et<br />al. use Livingston Island (LIV), in the South Shetland Islands archipelago (in operation<br />for ten years), and Chambodut et al. describe Concordia Base (in operation for<br />just over 3 years). Both have not yet achieved INTERMAGNET status.<br />De Lauretis et al. use two stations Concordia at Dome C and Mario Zucchelli at<br />Terra Nova Bay to show that the geomagnetic signals, measured by the two stations,<br />have very different signatures that depend upon the position of the stations with respect<br />to the sources.<br />The paper by Cafarella et al., describes long-term trends in geomagnetic measurements<br />which have non-absolute baselines for six months of the year at Mario<br />Zucchelli station (TNB). These authors compare TNB data with the models from<br />satellite measurements and find them to be in good agreement. They exhibit the different<br />long-term trend in source currents for example, daily variation, pulsations<br />and internal Earth sources such as jerks.<br />Maksymchuk et al. also describe the results of long-term (1998-2005 yrs.) magnetic<br />investigations but use tectonomagnetic techniques in the Western Antarctic<br />near the location of Ukrainian Antarctic Station «Academic Vernadsky». This new<br />type of research is described.<br />A novel approach to remote data acquisition is given in Torta et al. They describe<br />the development of data transmission facilities for real time access between Antarctica<br />and Spain using METEOSAT and GOES satellites and recently the move to a<br />high frequency (HF) digital radio-link, using ionospheric propagation.<br />Geomagnetic measurements from the deep sea are discussed in Vitale et al. From<br />2000 to 2005 two exploring geophysical missions were undertaken in the Tyrrhenian<br />deep seafloor at depths between around -2000 and -3000 m in the framework of the European-funded GEOSTAR Projects. During the two GEOSTAR deep seafloor<br />missions, scalar and vector magnetometer measurements were used to improve<br />global and regional geomagnetic reference models and to infer specific geoelectric<br />information about the two sites.<br />Three papers (Korte et al., Macmillan et al., Matzka et al.) describe magnetic observations<br />in the region of the South Atlantic anomaly. This is the region between<br />Africa and South America where Earth’s main magnetic field is depressed causing<br />localized space weather hazards (some described in Macmillan et al.), especially<br />satellite outages. Korte et al. describes the installation of new magnetic observatories<br />in Bolivia, Namibia and St Helena, and Macmillan et al. describe two older<br />magnetic observatories located on Ascension Island and Port Stanely.<br />Repeat station surveys are a way of measuring the secular variation of main field.<br />Matzka et al. contains a detailed report of a repeat station survey in this region at<br />Tristan da Cunha Island. They also describe the drawbacks of repeat station surveys<br />and prefer a magnetic observatory in the region which will be established for the<br />SWARM satellite mission. However, Korte et al. show that when nothing else exists<br />repeat stations are still a good way of obtaining secular variation data. They describe<br />the addition of several repeat stations in the South Atlantic anomaly area in<br />Africa.<br />Torta et al. and Korte et al. also describe efforts being made to create an unmanned<br />magnetic observatory, which would have INTERMAGNET standards.<br />The Guest Editors wish to thank Enkelejda Qamili for her assistance during the<br />session in Perugia, the numerous referees who reviewed the papers and the Editorial<br />office of Annals of Geophysics for their continued support and encouragement in<br />bring out this special issue of the Journal.