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Author(s): Angelo De Santis | Baldev Arora | Heather McCreadie

Journal: Annals of Geophysics
ISSN 1593-5213

Volume: 52;
Issue: 1;
Date: 2010;
Original page

Earth is a complex dynamic system and study of the geomagnetic field can provideinsight to the dynamic processes operative in the outer core where the main field isproduced by a geo-dynamo mechanism. By contrast the study of transient geomagneticvariations is an important tool for studying the complex solar wind-magnetosphere-ionosphere coupling. In addition the currents induced by the time varying externalcurrent system allow us to image the crust and the upper mantle in terms ofelectric conductivity. Lack of measurements and collection of geomagnetic data fromcertain strategic locations restricts the development of high quality models of maingeomagnetic field as well as the current systems responsible for transient geomagneticvariations. Division V of the International Association of Geomagnetic Aeronomy(IAGA) jointly with the Interdivisional Commission for Developing Countries organizeda special symposium «Geomagnetic Measurements in Remote Regions» at GeneralAssembly of IUGG held at Perugia (Italy) during July 2-12, 2007. Papers werepresented on data base numerical simulations identifying strategic gaps in the existingobservatory network where new measurements of geomagnetic field could improveupon existing geomagnetic reference models. Special focus was on describing thenovel design of equipment, modes of data collection and dissemination from remoteregions. During the symposium, 21 presentations were presented and this issue ofAnnals of Geophysics compiles a selection of papers.It is significant that each paper in this special issue is multi-authored by severalinstitutions and countries. This emphasizes the importance of worldwide collaborationwhen obtaining and analyzing data from geophysical observations in remote regions.With current technology magnetic observatories still require people to take measurementsat least once per week to enable baselines to be established and must beaway from power sources and transmission lines. This restricts the location of magneticobservatories used for deep Earth investigations. However, presented here arepapers describing ways to overcome harsh conditions and obtain magnetic data inremote locations. The need for long term ground based geomagnetic observatoriesfor reference models is well established and discussed. Also discussed, is the studyof magnetic field variations for determining transient phenomena. The measuringstations can exist unmanned as highlighted during the session by the Japanese group (not included in this volume) and Chambodut et al.Five papers (Cafarella et al., Chambodut et al., De Lauretis et al., Maksymchuket al., and Torta et al.) describe magnetic observations in Antarctica. Most of thiscontinent is covered by ice so it is almost impossible to sample the continental surfacedirectly: magnetic exploration allows us to overcome much of this problem, providingimportant information on the geological and tectonic settings of this continent.Antarctica is also an interesting magnetic region because it is in darkness forhalf of the year, so production of the ionospheric plasma that creates the daily Solarquiet variation is reduced for this period in this region (Chambodut et al.). In addition,it contains the southern polar cap current system – a window to the solar windand the magnetospheric-ionospheric energy transfer processes (De Lauretis et al.).Torta et al. and Chambodut et al. describe the exceptional means necessary for amagnetic observatory in Antarctica attempting to attain INTERMAGNET status. Torta etal. use Livingston Island (LIV), in the South Shetland Islands archipelago (in operationfor ten years), and Chambodut et al. describe Concordia Base (in operation forjust over 3 years). Both have not yet achieved INTERMAGNET status.De Lauretis et al. use two stations Concordia at Dome C and Mario Zucchelli atTerra Nova Bay to show that the geomagnetic signals, measured by the two stations,have very different signatures that depend upon the position of the stations with respectto the sources.The paper by Cafarella et al., describes long-term trends in geomagnetic measurementswhich have non-absolute baselines for six months of the year at MarioZucchelli station (TNB). These authors compare TNB data with the models fromsatellite measurements and find them to be in good agreement. They exhibit the differentlong-term trend in source currents for example, daily variation, pulsationsand internal Earth sources such as jerks.Maksymchuk et al. also describe the results of long-term (1998-2005 yrs.) magneticinvestigations but use tectonomagnetic techniques in the Western Antarcticnear the location of Ukrainian Antarctic Station «Academic Vernadsky». This newtype of research is described.A novel approach to remote data acquisition is given in Torta et al. They describethe development of data transmission facilities for real time access between Antarcticaand Spain using METEOSAT and GOES satellites and recently the move to ahigh frequency (HF) digital radio-link, using ionospheric propagation.Geomagnetic measurements from the deep sea are discussed in Vitale et al. From2000 to 2005 two exploring geophysical missions were undertaken in the Tyrrheniandeep seafloor at depths between around -2000 and -3000 m in the framework of the European-funded GEOSTAR Projects. During the two GEOSTAR deep seafloormissions, scalar and vector magnetometer measurements were used to improveglobal and regional geomagnetic reference models and to infer specific geoelectricinformation about the two sites.Three papers (Korte et al., Macmillan et al., Matzka et al.) describe magnetic observationsin the region of the South Atlantic anomaly. This is the region betweenAfrica and South America where Earth’s main magnetic field is depressed causinglocalized space weather hazards (some described in Macmillan et al.), especiallysatellite outages. Korte et al. describes the installation of new magnetic observatoriesin Bolivia, Namibia and St Helena, and Macmillan et al. describe two oldermagnetic observatories located on Ascension Island and Port Stanely.Repeat station surveys are a way of measuring the secular variation of main field.Matzka et al. contains a detailed report of a repeat station survey in this region atTristan da Cunha Island. They also describe the drawbacks of repeat station surveysand prefer a magnetic observatory in the region which will be established for theSWARM satellite mission. However, Korte et al. show that when nothing else existsrepeat stations are still a good way of obtaining secular variation data. They describethe addition of several repeat stations in the South Atlantic anomaly area inAfrica.Torta et al. and Korte et al. also describe efforts being made to create an unmannedmagnetic observatory, which would have INTERMAGNET standards.The Guest Editors wish to thank Enkelejda Qamili for her assistance during thesession in Perugia, the numerous referees who reviewed the papers and the Editorialoffice of Annals of Geophysics for their continued support and encouragement inbring out this special issue of the Journal.

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