Earth, Planets and Space | 2021
Special issue “Characterization of the geomagnetic field and its dynamic environment using data from space-based magnetometers”
Abstract
© The Author(s) 2021. This article is licensed under a Creative Commons Attribution 4.0 International License, which permits use, sharing, adaptation, distribution and reproduction in any medium or format, as long as you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons licence, and indicate if changes were made. The images or other third party material in this article are included in the article’s Creative Commons licence, unless indicated otherwise in a credit line to the material. If material is not included in the article’s Creative Commons licence and your intended use is not permitted by statutory regulation or exceeds the permitted use, you will need to obtain permission directly from the copyright holder. To view a copy of this licence, visit http:// creat iveco mmons. org/ licen ses/ by/4. 0/. The main part of the geomagnetic field arises from electric currents in the Earth’s outer core. It extends to a distance of ∼ 10 Earth radii and acts as a shield for protecting our atmosphere against solar and cosmic particle radiation. It also determines the strength and geometry of ionospheric and magnetospheric current systems. While the Earth’s core field varies on time scales of months to years, electric currents in the ionosphere and magnetosphere change within seconds to days, e.g., during space weather events. Continuous monitoring of the various magnetic field variations is thus important to characterize the Earth’s space environment and ensure the preparedness of modern technology on the ground and in space on which society increasingly depends. Most of our knowledge of the spatial and temporal variations of the recent geomagnetic field has been obtained using observations taken by high precision magnetic satellite missions, such as Ørsted, CHAMP, and currently the European Space Agency’s (ESA) magnetic field constellation mission Swarm. However, a multitude of satellites in low Earth orbit (LEO) carry magnetometers that, by design, do not meet the accuracy of dedicated geomagnetic missions. These are avionic, so-called platform magnetometers that are primarily used for coarse attitude determination of the spacecraft. Another category is magnetometers meant for science applications mounted on a boom, but those missions often neither measure the absolute magnetic field intensity together with the variations of the magnetic components nor provide precise attitude determination of the magnetometer itself. However, magnetic data from these missions have been shown to add valuable information in characterizing the geomagnetic field and its environment after appropriate calibration. This special issue collects articles that document successful calibration strategies including the validation of their results, e.g., by comparison to other data or applied in exemplary science cases, and articles that outline valuable research application in Earth and space sciences by the use of these magnetometer data. Figure 1 shows the altitude distribution of the satellite missions, which data were analyzed in papers of this special issue. In combination, they provide a multi-mission data set in LEO spanning almost two solar cycles. Extending the calibration scheme developed and applied to data from high-precision satellite missions, Olsen et al. (2020) introduce an approach for characterization, calibration, and alignment of vector magnetometer data, applied to data from the platform magnetometers onboard ESA’s CryoSat-2 satellite. The calibration is performed by comparing the magnetometer sensor readings with magnetic field values for the time and position of the satellite as given by an a priori high-precision geomagnetic field model, e.g. CHAOS (Finlay et al. 2020), to estimate the magnetometer calibration parameters by solving a least square problem. The calibrated magnetic data show good agreement with Open Access