Preface

Angelo De Santis, Baldev Arora, Heather McCreadie

Abstract


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

References


DOI: https://doi.org/10.4401/ag-4566
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Published by INGV, Istituto Nazionale di Geofisica e Vulcanologia - ISSN: 2037-416X