Publications
Geomagnetism publications.
Filter Total Items: 414
New and revised 14C dates for Hawaiian surface lava flows: Paleomagnetic and geomagnetic implications
Radiocarbon dates have been obtained for 30 charcoal samples corresponding to 27 surface lava flows from the Mauna Loa and Kilauea volcanoes on the Island of Hawaii. The submitted charcoal was a mixture of fresh and archived material. Preparation and analysis was undertaken at the NERC Radiocarbon Laboratory in Glasgow, Scotland, and the associated SUERC Accelerator Mass Spectrometry facility. The
Authors
Nicola Pressling, Frank A. Trusdell, David Gubbins
New substorm index derived from high-resolution geomagnetic field data at low latitude and its comparison with AE and ASY indices
High-resolution geomagnetic field data (i.e., ≤5 seconds) have recently become more commonly used by space physicists. The data permit the identification of Pi2 pulsations, having periods of 40-150 seconds and irregular waveforms. Pulsations of this type appear clearly in time series from mid- and low-latitude ground stations on the nightside at substorm onset. Therefore, with data from multiple o
Authors
M. Nose, T. Iyemori, M. Takeda, H. Toh, T. Ookawa, G. Cifuentes-Nava, J. Matzka, Jeffrey J. Love, H. McCreadie, M. K. Tunçer, J. J. Curto
Absolute Measurement Session XIII IAGA Workshop Boulder Magnetic Observatory
The absolute measurement session of the XIII IAGA Workshop was held at the Boulder Magnetic Observatory June 10-13, 2008. Approximately 85 people attended this session. The main focus of the session was for observers to make and compare measurements using DIFlux magnetometers. The session also included absolute measurement training, with lectures and practical training. Also included were data pro
Authors
A. Berarducci, Andy Woods
Missing data and the accuracy of magnetic-observatory hour means
Analysis is made of the accuracy of magnetic-observatory hourly means constructed from definitive minute data having missing values (gaps). Bootstrap sampling from different data-gap distributions is used to estimate average errors on hourly means as a function of the number of missing data. Absolute and relative error results are calculated for horizontal-intensity, declination, and vertical-comp
Authors
Jeffrey J. Love
Total field sensor comparison
During the XIIIth IAGA Workshop (hereafter referred to as “the workshop"), several total field comparison measurements were conducted at the Boulder Magnetic Observatory (BOU). The purpose of these tests was to look for errors within the total field instruments which are considered “absolutes” instruments. The total field measurement is a critical component of the absolute measurement computation.
Authors
Tim White
Earth's magnetic field complex: U.S. National activities during the Decade of Geopotential Field Research
The US geomagnetism community is supported by NASA, NOAA, USGS, NSF, DOD, and US universities. During the Decade of Geopotential Field Research, inaugurated in 1999 with the launch of the Danish satellite Ørsted on a US rocket, the US community has been involved in satellite mission development and analysis, instrument development, model development, and in the discovery and understanding of new p
Authors
Michael E. Purucker, T. Sabaka, W. Kuang, S. Maus, Jeffrey J. Love
On the reported magnetic precursor of the 1993 guam earthquake
Using 1-second magnetometer data recorded 67 km from the epicenter of the 1993 Mw 7.7 Guam earthquake, Hayakawa et al. (1996) and Miyahara et al. (1999) identify anomalous precursory changes in ultra-low frequency magnetic polarization (the ratio of vertical to horizontal field components). In a check of their results, we compare their data (GAM) with 1-second data from the Kakioka observatory (KA
Authors
J.N. Thomas, J.J. Love, M.J.S. Johnston, K. Yumoto
Geomagnetic observations on tristan da cunha, south atlantic ocean
Few geomagnetic ground observations exist of the Earth's strongest core field anomaly, the South Atlantic Anomaly (SAA). The geomagnetic repeat station on the island Tristan da Cunha, located half-way between South Africa and South America at 37?? 05' S, 12?? 18' W, is therefore of crucial importance. We have conducted several sets of repeat station measurements during magnetically quiet condition
Authors
J. Matzka, N. Olsen, C.F. Maule, L.W. Pedersen, A.M. Berarducci, S. Macmillan
Revised Dst and the epicycles of magnetic disturbance: 1958-2007
A revised version of the storm-time disturbance index Dst is calculated using hourly-mean magnetic-observatory data from four standard observatories and collected over the years 1958-2007. The calculation algorithm is a revision of that established by Sugiura et al., and which is now used by the Kyoto World Data Center for routine production of Dst. The most important new development is for the re
Authors
J.J. Love, J.L. Gannon
On the reported magnetic precursor of the 1989 Loma Prieta earthquake
Among the most frequently cited reports in the science of earthquake prediction is that by Fraser-Smith et al. (1990) and Bernardi et al. (1991). They found anomalous enhancement of magnetic-field noise levels prior to the 18 October 1989 Loma Prieta earthquake in the ultra-low-frequency range (0.0110-10.001 Hz) from a ground-based sensor at Corralitos, CA, just 7 km from the earthquake epicenter.
Authors
J.N. Thomas, J.J. Love, M.J.S. Johnston
In situ measurements of contributions to the global electrical circuit by a thunderstorm in southeastern Brazil
The global electrical circuit, which maintains a potential of about 280??kV between the earth and the ionosphere, is thought to be driven mainly by thunderstorms and lightning. However, very few in situ measurements of electrical current above thunderstorms have been successfully obtained. In this paper, we present dc to very low frequency electric fields and atmospheric conductivity measured in t
Authors
J.N. Thomas, R.H. Holzworth, M.P. McCarthy
Monitoring the Earth's dynamic magnetic field
The mission of the U.S. Geological Survey's Geomagnetism Program is to monitor the Earth's magnetic field. Using ground-based observatories, the Program provides continuous records of magnetic field variations covering long timescales; disseminates magnetic data to various governmental, academic, and private institutions; and conducts research into the nature of geomagnetic variations for purposes
Authors
Jeffrey J. Love, David Applegate, John B. Townshend