14 documents found in 347ms
# 1
Korte, Monika • Brown, Maxwell
Abstract: Global spherical harmonic paleomagnetic field model LSMOD.2 describes the magnetic field evolution from 50 to 30 ka BP based on published paleomagnetic sediment records and volcanic data. It is an update of LSMOD.1, with the only difference being a correction to the geographic locations of one of the underlying datasets. The time interval includes the Laschamp (~41 ka BP) and Mono Lake (~34 ka BP) excursions. The model is given with Fortran source code to obtain spherical harmonic magnetic field coefficients for individual epochs and to obtain time series of magnetic declination, inclination and field intensity from 49.95 to 30 ka BP for any location on Earth. For details see M. Korte, M. Brown, S. Panovska and I. Wardinski (2019): Robust characteristics of the Laschamp and Mono lake geomagnetic excursions: results from global field models. Submitted to Frontiers in Earth Sciences
File overview: LSMOD.2 -- ASCII file containing the time-dependent model by a list of spline basis knot points and spherical harmonic coefficients for these knot points.LSfield.f -- Fortran source code to obtain time series predictions of declination, inclination and intensity from the model file.LScoefs.f -- Fortran source code to obtain the spherical harmonic coefficients for an individual age from the time-dependent model file. The data are licenced under the Creative Commons Attribution 4.0 International Licence (CC BY 4.0) and the Fortran Codes under the Apache License, Version 2.0. The Fortran source code should work with any standard Fortran 77 or higher compiler. Each of the two program files can be compiled separately, all required subroutines are included in the files. The model file, LSMOD.1 or LSMOD.2, is read in by the executable program and has to be in the same directory. The programs work with interactive input, which will be requested when running the program.
# 2
Ritter, Patricia
Abstract: This dataset comprises profiles of Hall ionospheric current densities derived from scalar magnetic field data measured from the CHAMP satellite during six magnetic storms. The Hall currents are intense electric currents that flow horizontally above the earth’s surface in the polar region and perpendicular to the geomagnetic field. They peak at approximately ± 80° of geomagnetic latitude. Together with the field-aligned currents they form part of the ionospheric current system. During enhanced geomagnetic activity the Hall current peak locations are shifted equatorward. The CHAllenging Minisatellite Payload (CHAMP) spacecraft circled the Earth during the years 2000 – 2010 on a near-polar orbit (inclination 87.3°), each orbit taking 93 minutes at an altitude of initially 455 km. Within 4 months CHAMP covered all local times. The data records used for determining the Hall currents are scalar magnetic field measurements obtained with the Overhauser magnetometer on the satellite boom, with a sample frequency of 1 Hz and a resolution of 0.1 nT. In order to isolate the magnetic effects of ionospheric currents in the satellite observations, the contributions from all other sources were removed from the scalar field readings. The main, crustal and external magnetic fields were subtracted using the POMME 6 model (Maus et al, 2010, http://www.geomag.us/models/pomme6.html). The Hall current densities were obtained by fitting a line current model to the observed magnetic field residuals. The model consists of a series of 160 horizontal infinite current lines centered at the orbit position closest to the geographic pole, at an altitude of 110 km and separated by 1° in latitude. The magnetic field of the line currents are related to the current strength according to the Biot–Savart law. Assuming a static current, the strength of each current line is derived from an inversion of the observed field residuals applying a least squares fitting approach. This method of Hall current estimation from scalar magnetometer records measured at satellites was proposed initially by Olsen (1996). The reliability of the approach was demonstrated and validated in a statistical study where Hall current density estimates from CHAMP were directly compared with independent determinations from ground observations of the IMAGE magnetometer array (Ritter et al., 2004).
# 3
Soares, Gabriel B. • Matzka, Jürgen • Pinheiro, Katia
Abstract: This dataset comprises preliminary minute means of the XYZ (X=geographic north, Y=geographic east, Z=downward) magnetic field components measured at the geomagnetic observatory Tatuoca (IAGA code TTB) for the period June 1st, 2008 to December 31st, 2017. TTB is located in northern Brazil and operates under the administration of Observatório Nacional (ON) since 1957. Since 2015 it is operated in cooperation between ON and GFZ. Since the early years of the 2000 decade, the magnetic equator is close to the observatory TTB. The variations from June 1st 2008 until November 19th, 2015 were recorded by a LEMI-417M fluxgate magnetometer (sampling rate during most of this period was 1 sec, but occasionally 0.25 or 6 sec). From November 20th, 2015 onwards, a DTU FGE fluxgate magnetometer (1 sec sampling) provided the variations. From late October 2016, the total field F was measured with a Gemsys overhauser absolute scalar magnetometer with 1 sec sampling. This is a processed and calibrated dataset. Inconsistencies like spikes and data jumps were corrected. The maximum admitted noise level in this dataset is 1 nT peak to peak in the underlying 1 sec data. Periods of recurrent noise exceeding this criterion were systematically deleted from the records. For data calibration, the baseline was constructed by means of absolute measurements of the geomagnetic field and applied to the variation data. The data files are provided in the IAGA-2002 format (https://www.ngdc.noaa.gov/IAGA/vdat/IAGA2002/iaga2002format.html) as daily files for 1-minute means. Following the IAGA2002-format, the filename consists of the IAGA-code, the year (YYYY), the month (MM), the day (DD), the letter p for preliminary, the letters min for 1-minute data, and the file extension min again for 1-minute data. The first 16 lines in each file are a IAGA2002-typical header, then comes, blank separated, the date (YYYY-MM-DD), time (hh:mm:ss.sss in UTC), day of year (DOY), the X component (XXXXX.XX in nT), the Y-component (YYYYY.YY in nT), the Z-component (ZZZZZ.ZZ in nT) and F (FFFFF.FF in nT). Please note that a dataset based on the data provided here will be submitted to the World Data Centre for Geomagnetism (WDC Edinburgh) at a later stage and might undergo further modifications. Geomagnetic observatories in general are described in e.g. Jankowski and Sucksdorff (1996), Matzka et al. (2010). GFZ observatories and observatory cooperations are described in Matzka (2016). The Geomagnetic Observatory Tatuoca (TTB) is described in Moschhauser et al. (2017).
# 4
Pick, Leonie • Korte, Monika
Abstract: The HMC (Hourly Magnetospheric Currents) index measures the activity of large-scale magnetospheric currents on Earth's surface from 1900 to 2015. It resolves the absolute intensity of low-frequency variations, especially at periods relevant to the solar cycle, more robustly than existing geomagnetic indices. HMC is based on hourly means of vector magnetic field measurements from 34 mid latitude geomagnetic observatories obtained from WDC Edinburgh (http://www.wdc.bgs.ac.uk/catalog/master.html). This data has been manually revised to correct for spikes, jumps and drifts. A detailed description of the derivation method is given in Pick et al., 2018 to which these data are supplementary material. This directory contains the HMC index (hmc1900phor.hor) and the modified observatory data that it is based on (data.zip). The index and the observatory data files are formatted in compliance with the IAGA-2002 ASCII exchange format (https://www.ngdc.noaa.gov/IAGA/vdat/IAGA2002/iaga2002format.html). Individual file names are composed of:[IAGA code of observatory] + [first active year during 1900-2015] + [p(provisional)] + [hor(hourly)] + [_mod(modified)].hor Also included is information on how the data modifications (list in modifications.pdf) were applied (readme.txt).
# 5
Korte, Monika • Brown, Maxwell • Gunnarson, Sydney
Abstract: Global spherical harmonic paleomagnetic field model LSMOD.1 describes the magnetic field evolution from 50 to 30 ka BP based on published paleomagnetic sediment records and volcanic data. The time interval includes the Laschamp (~41 ka BP) and Mono Lake (~34 ka BP) excursions. The model is given with Fortran source code to obtain spherical harmonic magnetic field coefficients for individual epochs and to obtain time series of magnetic declination, inclination and field intensity from 49.95 to 30 ka BP for any location on Earth. For details see M. Brown, M. Korte, R. Holme, I. Wardinski and S. Gunnarson (2018): Earth's magnetic field is probably not reversing. PNAS, 115, 5111-5116.
File overviewLSMOD.1 -- ASCII file containing the time-dependent model by a list of spline basis knot points and spherical harmonic coefficients for these knot points.LSfield.f -- Fortran source code to obtain time series predictions of declination, inclination and intensity from the model file.LScoefs.f -- Fortran source code to obtain the spherical harmonic coefficients for an individual age from the time-dependent model file. The data are licenced under the Creative Commons Attribution 4.0 International Licence (CC BY 4.0) and the Fortran Codes under the Apache License, Version 2.0. The Fortran source code should work with any standard Fortran 77 or higher compiler. Each of the two program files can be compiled separately, all required subroutines are included in the files. The model file, LSMOD.1 or LSMOD.2, is read in by the executable program and has to be in the same directory. The programs work with interactive input, which will be requested when running the program.
# 6
Brown, Maxwell • Korte, Monika • Holme, Richard • Wardinski, Ingo • Gunnarson, Sydney
Abstract: Compilation of palaeomagnetic data from sediments and volcanic rocks from 68 sites spanning 30,000 to 50,000 years ago used to create the temporally continuous global spherical harmonic geomagnetic field model LSMOD.1. This is in supplement to the paper "Earth's magnetic field is (probably not reversing" (Brown et al. 2018) A description of how the data were treated is given in SI Appendix of the associated publication. A full list of complementary data sources (references) is given is provided with the data.-----------------For the volcanics there is one filevolc.txt The headers are:Age[ka] - age in thousands of years before present (0 = 1950 AD).Error[ka] - uncertainty on the age.Lat[Deg] - Latitude of site in degrees.Lon[Deg] - Longitude of site in degrees.Dec[Deg] - Declination in degrees.Inc[Deg] - Inclination in degrees.Alpha95[Deg] - 95% circular confidence limit on the directional data.F[microT] - intensity in micro Tesla.F_Error[microT] - uncertainy on the intensity in micro Tesla. -9999 - no data-----------------For the sediments there are two types of files, those that end *.txt and those that end *int.txt. *.txt - directional data with the headers: Age[ka] - age in thousands of years before present (0 = 1950 AD).Lat[Deg] - Latitude of site in degrees.Lon[Deg] - Longitude of site in degrees.Dec[Deg] - Declination in degrees.Inc[Deg] - Inclination in degrees. -9999 - no data *int.txt - scaled intensity data using PADM2M (as described in Section S1.3 of SI Appendix)Age[ka] - age in thousands of years before present (0 = 1950 AD).Lat[Deg] - Latitude of site in degrees.Lon[Deg] - Longitude of site in degrees.F[microT] - Scaled intensity in micro Tesla. 6 of the sediment data sets are individual records (BLS, CHI, MIN, PYR, SIO, S01).6 of the sediment data sets are stacks of records (BBS, NAS, NPS, OBS, SBS, SAS). All details of the records are given in Table S1 and Table S2 of the SI Appendix of the associated publication.
# 7
Ritter, Oliver • Muñoz, Gerard • Weckmann, Ute • Klose, Reinhard • Rettig, Stefan • (et. al.)
Abstract: Magnetotellurics (MT) is a passive geophysical method which uses natural variations of electromagnetic fields generated by global lightning discharges and ionospheric current systems. Since it is impossible to control these source fields, signal-to-noise ratios can be poor, particularly in presence of cultural electromagnetic noise such as power lines, railways, anti-corrosion currents in gas pipelines, etc. The Remote Reference (RR) technique is an effective way to improve magnetotelluric data quality by referencing the locally recorded electromagnetic fields to simultaneously collected, undisturbed fields at a remote reference site. Finding and maintaining such a reference site during a field campaign is expensive and time consuming. The permanent reference site in Wittstock is operated by the Geo-Electromagnetics working group of the GFZ within the framework of the Geophysical Instrument Pool Potsdam and offers high quality magnetic field recordings for RR processing free of charge for the EM community.A permanent magnetotelluric (MT) remote reference station is located in an urban forest near the city of Wittstock, in north-eastern Germany (Eydam and Muñoz, 2011). It is equipped with two S.P.A.M. Mk IV data loggers and three sets of magnetometers working in different frequency ranges. The highest frequency data is recorded using Metronix MFS07 induction coils with a sampling frequency of 6.25 kHz. The high frequency data is recorded in quasi-continuous segments, with intervals of data being collected for 10 minutes at every hour. The intermediate, broad band magnetic field data are recorded continuously using Metronix MFS06 induction coils at 250 Hz sampling frequency. Finally, long period data is recorded using a 3-component Geomagnet Fluxgate magnetometer with 5 Hz sampling rate. For completeness, electric fields are also recorded continuously at the highest frequency.The data are organized and available as daily folders. Data files are in EMERALD format (Ritter et al., 1998), which is also described in this document. We also provide computer code and example data demonstrating how to read these data files. The tools are provided as FORTRAN, C and C++ source codes and MATLAB scripts.
# 8
Matzka, Jürgen • Ricaldi, Edgar • Miranda, Pedro
Abstract: The dataset contains minute mean values of the geomagnetic field expressed as northward component X, eastward component Y, and vertical (downward) component Z as measured at the geomagnetic observatory Villa Remedios, Bolivia, for January 2013. Villa Remedios (preliminary code VRE) is operated in cooperation by the university Universidad Mayor de San Andrés in La Paz, Bolivia, and GFZ German Research Centre for Geosciences since the end of 2002. The observatory is not yet an INTERMAGNET observatory and so far, no data has been submitted to any World Data Centre for Geomagnetism. However, preliminary geomagnetic data (minute means) from Villa Remedios are available upon request from GFZ. Please note that a dataset based on the data provided here will be submitted to the WDC for Geomagnetism at a later stage and might differ slightly due to calibration and removal of outliers. Villa Remedios is located about 650 km south of the magnetic equator and about 930 km south-east of the geomagnetic observatory Huancayo (IAGA code HUA, Peru). This makes VRE a suitable observatory to be used in conjunction with HUA to isolate and study the equatorial electrojet signal at Huancayo. The data file is in ASCII format and contains blank-separated the year (YYYY), the month (MM), the day (DD), the time (UTC) in the format hh.mm, the X component in nanotesla (nT), the Y component in nT, the vertical component Z in nT, the total geomagnetic field F in nT measured with an independent, auxiliary scalar magnetometer, and, finally, the difference (in nT) between F measured with the auxiliary scalar magnetometer and the total field calculated from the components X, Y and Z. Components X, Y and Z are measured with an FGE variometer (serial number S0199, E0213 built by DTU Space, Technical University of Denmark) and in this data file, they are preliminarily calibrated and given in nanotesla (nT). These values are minute means and filtered from spot readings by an INTERMAGNET Gauss-shaped filter. The scalar magnetometer is a GSM90F1 by Gemsys, Canada. The data logger is a Flare+ by British Geological Survey. Geomagnetic observatories are described in e.g. Jankowski and Sucksdorf (1996), in Matzka et al., (2010) and Matzka (2016).
# 9
Matzka, Jürgen • Lilienkamp, Henning • Soares, Gabriel Brando • Rosales, Domingo • Vidal, Erick • (et. al.)
Abstract: The dataset contains hourly mean values (HMV) of the horizontal magnetic field component H as measured at the geomagnetic observatory Huancayo for 1958 to 2013. Huancayo observatory (IAGA code HUA) is operated by Instituto Geofisico del Peru. This dataset is based on and partly supersedes the data publication Matzka et al. (2017a), which is described in Matzka et al. (2017b). It will be superseded by another data publication (Soares et al., in preparation) that we intend to publish at GFZ Data Services as well as the World Data Centres for Geomagnetism. As already described in Matzka et al. (2017a, 2017b), the HMVs were taken from the World Data Centre Kyoto (WDC Kyoto) and data gaps (in total some 19 years from the 1960ies, 1970ies and 1980ies) were filled in by typing handwritten records of the HMV at GFZ. These handwritten records were monthly tables that were received as digital images from geomagnetic observatory Huancayo or that were received as microfilms from World Data Centre Boulder. We also produced digital images of these microfilms. The values from the WDC Kyoto are definitive values; the monthly tables presumably also contain definitive values. Corrections to HUA HMVs from WDC Kyoto: There is a known error in the time stamping of the HUA HMVs prior to 1948 (before 1948 the data was reported in local time, rather than universal time). This error is corrected in the present dataset. Also, an attempt was made to correct for a jump in the HMV time series at this time. Further corrections, made to the dataset by Matzka et al. (2017a), are mostly the correction or deletion of outliers and the correction of shifts in the data. Again, please note that a dataset based on the data provided here will be submitted to the World Data Centres for Geomagnetism at a later stage and will have some additional modifications (Soares et al., in preparation). The data file is in ASCII format and contains blank-separated first the year (YYYY), the month (MM), the day (DD) followed by the 24 HMVs of H (format HHHHH) in nanotesla (nT), starting with the HMV for 00 to 01 universal time. Geomagnetic observatories are described in e.g. Jankowski and Sucksdorf (1996), in Matzka et al., (2010) and Matzka (2016).
# 10
Matzka, Jürgen • Ricaldi, Edgar • Miranda, Pedro
Abstract: The dataset contains minute mean values of the geomagnetic field expressed as northward component X, eastward component Y, and vertical (downward) component Z as measured at the geomagnetic observatory Villa Remedios, Bolivia, for August 2010. Villa Remedios (preliminary code VRE) is operated in cooperation by the university Universidad Mayor de San Andrés in La Paz, Bolivia, and GFZ German Research Centre for Geosciences since the end of 2002. The observatory is not yet an INTERMAGNET observatory and so far, no data has been submitted to any World Data Centre for Geomagnetism. However, preliminary geomagnetic data (minute means) from Villa Remedios are available upon request from GFZ. Please note that a dataset based on the data provided here will be submitted to the WDC for Geomagnetism at a later stage and might differ slightly due to calibration and removal of outliers. Villa Remedios is located about 650 km south of the magnetic equator and about 930 km south-east of the geomagnetic observatory Huancayo (IAGA code HUA, Peru). This makes VRE a suitable observatory to be used in conjunction with HUA to isolate and study the equatorial electrojet signal at Huancayo. The data file is in ASCII format and contains blank-separated the year (YYYY), the month (MM), the day (DD), the time (UTC) in the format hh.mm, the X component in nanotesla (nT), the Y component in nT, the vertical component Z in nT, the total geomagnetic field F in nT measured with an independent, auxiliary scalar magnetometer, and, finally, the difference (in nT) between F measured with the auxiliary scalar magnetometer and the total field calculated from the components X, Y and Z. Components X, Y and Z are measured with an FGE variometer (serial number S0199, E0213 built by DTU Space, Technical University of Denmark) and in this data file, they are preliminarily calibrated and given in nanotesla (nT). These values are minute means and filtered from spot readings by an INTERMAGNET Gauss-shaped filter. The scalar magnetometer is a GSM90F1 by Gemsys, Canada. The data logger is a Flare+ by British Geological Survey. Geomagnetic observatories are described in, e.g., Jankowski and Sucksdorf (1996), in Matzka et al., (2010), and Matzka (2016).
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