edu.ucar.opensky::articles:12898 UCAR/NCAR - Library OpenSky Support PO Box 3000 Boulder CO 80307-3000 opensky@ucar.edu http://opensky.ucar.edu/ homepage pointOfContact 2025-12-26T03:43:48.517632 ISO 19115-2 Geographic Information - Metadata - Part 2: Extensions for Imagery and Gridded Data ISO 19115-2:2009(E) https://n2t.org/ark:/85065/d76974f7 Long-term changes in solar quiet (Sq) geomagnetic variations related to Earth's magnetic field secular variation 2013-06-18T00:00:00Z publication https://n2t.org/ark:/85065/d76974f7 https://doi.org/10.1002/jgra.50352 de Haro Barbas, B. author Elias, A. author Cnossen, Ingrid author de Artigas, M. Z. author UCAR/NCAR - Library publisher The daily amplitude of the solar quiet (Sq) magnetic variation of the horizontal intensity, H, of observatories at low and midlatitudes is analyzed, in search of significant long-term trends. These trends are expected based on secular variations of the Earth's magnetic field (B) and increasing concentrations of greenhouse gases which can affect Sq for instance through their effect on ionospheric conductivities and E-region electron concentration. The hourly horizontal geomagnetic field component, H, measured at Apia, Fredericksburg, Hermanus, Bangui, and Trivandrum was analyzed for the period 1960-2000. The solar activity effect was filtered out from the daily Sq amplitude of H, and then linear trends were calculated and compared to trend values obtained from the Coupled Magnetosphere-Ionosphere-Thermosphere model. Linear trends were calculated separately for periods of different secular trends in the magnetic field intensity, B. We found significant trends in experimental data for Apia, Fredericksburg, Hermanus, and for the period 1960-1983 for Bangui. There is reasonable quantitative agreement between experimental and simulated trends, and a qualitative agreement with trends expected from the secular trend in B. UCAR/NCAR - Library OpenSky Support PO Box 3000 Boulder CO 80307-3000 opensky@ucar.edu http://opensky.ucar.edu/ homepage pointOfContact PDF Text theme Resource Type 2016-01-01T00:00:00Z publication Copyright 2013 American Geophysical Union. None eng geoscientificInformation