Special issue "Swarm science results after 2 years in space"

Olsen et al. Earth, Planets and Space (2016) 68:172 DOI 10.1186/s40623-016-0546-6

Special issue Swarm science results after2years inspace

Nils Olsen1*, Claudia Stolle2, Rune Floberghagen3, Gauthier Hulot4 and Alexey Kuvshinov5

Swarm is a three-satellite constellation mission launched by the European Space Agency (ESA) on 22 November 2013. It consists of three identical spacecraft, two of which (Swarm Alpha and Swarm Charlie) are ying almost side-by-side in polar orbits at lower altitude (about 470 km in September 2016) with an East-West separation of 1.4 in longitude corresponding to 155km at the equator. The third satellite (Swarm Bravo) is in a slightly higher orbit (about 520km altitude in September 2016). Each of the three satellites carry a magnetometry package (consisting of absolute scalar magnetometer, uxgate vector magnetometer, and star imager) for measuring the direction and strength of the magnetic eld, and instruments to measure plasma and electric eld parameters as well as gravitational acceleration. Time and position are provided by on-board GPS. The conguration of the various instruments on each of the three Swarm spacecraft is shown in Fig. 1. More information about the mission can be found at http://earth.esa.int/swarm

Web End =http://earth.esa.int/ http://earth.esa.int/swarm

Web End =swarm .

The 21 articles collected in this special issue were stimulated by the Joint Inter-Association Symposium JA4 Results from Swarm, Ground Based Data and Earlier Satellite Missions at the 26th General Assembly of the International Union of Geodesy and Geophysics (IUGG) held in Prague in July 2015.

Tner-Clausen et al. (2016) report on the advanced calibration of the magnetometry package of the Swarm satellites. Finlay etal. (2016) and Olsen etal. (2016) present models of Earths core magnetic eld, while Thbault et al. (2016) and Kotsiaros (2016) determine models of the lithospheric eld. The importance of high-resolution magnetic eld models for studying external magnetic

eld contributions, in particular during geomagnetic quiet conditions, is discussed by Stolle etal. (2016).

Five contributions discuss the magnetic eld produced by ionospheric and magnetospheric currents: Chulliat etal. (2016) present a climatological model of the ionospheric currents responsible for geomagnetic daily variations at non-polar latitudes, while the work of Laundal et al. (2016) concentrates on a consistent description of horizontal ionospheric and eld-aligned currents in the polar ionosphere, in particular regarding their dependence on solar irradiation that controls ionospheric conductivity. A scheme for estimating the polar ionospheric currents that form the Polar Electrojets on an orbit-by-orbit basis is presented by Aakjr etal. (2016), while Tozzi etal. (2016) discuss unmodelled magnetic eld contributions in satellite-based magnetic eld models. Michelis etal. (2016) present a study of high-latitude magnetic eld variations during the St. Patricks Day Storm.

The same event is investigated by Pignalberi et al. (2016) using Swarm plasma density measurements, and by Cherniak and Zakharenkova (2016) using GPS data from ground and Swarm.

Calibration of the electric eld instrument of Swarm is presented by Fiori etal. (2016). A combination of electric, magnetic, and TEC observations has been used by Astafyeva et al. (2016) to investigate the magnetic storm of 2223 June 2015. Aoyama etal. (2016) combine ground magnetic data and Swarm TEC observations to study possible ionospheric eects of the 2015 eruption of a volcano in Chile, Zakharenkova etal. (2016) used GPS and Swarm plasma observations to study equatorial plasma density irregularities in the topside ionosphere, and Xiong etal. (2016) performed a scale analysis of equatorial plasma irregularities.van den IJssel et al. (2016) describe improvements of Swarm GPS antenna settings to enhance high-precision positioning of the spacecraft, and da Encarnao et al. (2016) discuss various attempts to determine monthly

*Correspondence: [email protected]

1 Division of Geomagnetism, DTU Space, Technical University of Denmark, Diplomvej 371, 2800 Kongens Lyngby, DenmarkFull list of author information is available at the end of the article

The Author(s) 2016. This article is distributed under the terms of the Creative Commons Attribution 4.0 International License (http://creativecommons.org/licenses/by/4.0/

Web End =http://creativecommons.org/licenses/by/4.0/ ), which permits unrestricted use, distribution, and reproduction in any medium, provided you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons license, and indicate if changes were made.

Olsen et al. Earth, Planets and Space (2016) 68:172

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snapshot models of the large-scale part of Earths gravity eld from Swarm GPS observations.

Finally, the processing of the Swarm accelerometer data is described by Siemes etal. (2016).

The work reported in this issue could not have been achieved without the unfailing support of our deeply regretted friend and colleague Gernot Plank (Fig. 2), to which we wish to dedicate this special issue of Earth Planets Space. Gernot has been one of the major contributors to the success of the Swarm mission. With great enthusiasm he played a considerable role in the establishment of Swarm SCARF, the Swarm Level-2 data processing facility. Swarm SCARF was key to the project and all scientic results presented in the present special issue (as well an in a previous issue, see Earth Planets Space, Vol.65, Issue 11) heavily rely on the success of this facility. Gernots

energy and enthusiastic spirit, from beginning to end of even the most intense meetings, was extremely appreciated. He had a remarkable ability to help solve problems and convince anyone to do the right thing in the interest of the project and science, sometimes even very late in the evening, and always in his unique and particularly cheerful way, whatever the circumstances.

Gernot passed away in March 2016 after a lengthy, hard, and unfair ght against cancer. He, and his legendary laugh, will be sorrowfully missed by his friends and colleagues.

Authors contributions

All authors of this article served as guest editors for this special issue. All authors read and approved the nal manuscript.

Author details

1 Division of Geomagnetism, DTU Space, Technical University of Denmark, Diplomvej 371, 2800 Kongens Lyngby, Denmark. 2 HelmholtzZentrum Potsdam, Deutsches GeoForschungsZentrum GFZ, 14473 Potsdam, Germany.

3 Directorate of Earth Observation Programmes, ESRIN, Via Galileo Galilei 2, 00044 Frascati, Italy. 4 Equipe de Gomagntisme, Institut de Physique du Globe de Paris, Sorbonne Paris Cit, Universit Paris Diderot, CNRS, 1 rue Jus sieu, 75005 Paris, France. 5 Institute of Geophysics, ETH Zrich, Sonneggstrasse 5, 8092 Zrich, Switzerland.

Acknowledgements

We thank the authors of the papers in this special issue, and the referees who served to evaluate the contributions and gave helpful comments and suggestions.

Received: 10 October 2016 Accepted: 10 October 2016

References

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Michelis PD, Consolini G, Tozzi R, Marcucci MF (2016) Observations of high latitude geomagnetic eld uctuations during St. Patricks Day Storm: Swarm and SuperDARN measurements. Earth Planets Space 68:105. doi:http://dx.doi.org/10.1186/s40623-016-0476-3

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