University of Oulu

Palmroth, M., Grandin, M., Sarris, T., Doornbos, E., Tourgaidis, S., Aikio, A., Buchert, S., Clilverd, M. A., Dandouras, I., Heelis, R., Hoffmann, A., Ivchenko, N., Kervalishvili, G., Knudsen, D. J., Kotova, A., Liu, H.-L., Malaspina, D. M., March, G., Marchaudon, A., Marghitu, O., Matsuo, T., Miloch, W. J., Moretto-Jørgensen, T., Mpaloukidis, D., Olsen, N., Papadakis, K., Pfaff, R., Pirnaris, P., Siemes, C., Stolle, C., Suni, J., van den IJssel, J., Verronen, P. T., Visser, P., and Yamauchi, M.: Lower-thermosphere–ionosphere (LTI) quantities: current status of measuring techniques and models, Ann. Geophys., 39, 189–237,, 2021

Lower-thermosphere–ionosphere (LTI) quantities : current status of measuring techniques and models

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Author: Palmroth, Minna1,2; Grandin, Maxime1; Sarris, Theodoros3;
Organizations: 1Univ Helsinki, Dept Phys, Helsinki, Finland.
2Finnish Meteorol Inst, Space & Earth Observat Ctr, Helsinki, Finland.
3Democritus Univ Thrace, Dept Elect & Comp Engn, Xanthi, Greece.
4Royal Netherlands Meteorol Inst KNMI, Utrecht, Netherlands.
5Athena Res & Innovat Ctr, Space Programmes Unit, Athens, Greece.
6Univ Oulu, Space Phys & Astron Res Unit, Oulu, Finland.
7Swedish Inst Space Phys IRF, Uppsala, Sweden.
8British Antarctic Survey UKRI NERC, Cambridge, England.
9Univ Toulouse, CNES, CNRS, Inst Rech Astrophys & Planetol, Toulouse, France.
10Univ Texas Dallas, Ctr Space Sci, Dallas, TX USA.
11European Space Agcy, European Space Res & Technol Ctr, Noordwijk, Netherlands.
12Royal Inst Technol KTH, Div Space & Plasma Phys, Stockholm, Sweden.
13German Res Ctr Geosci, GFZ Potsdam, Potsdam, Germany.
14Univ Calgary, Dept Phys & Astron, Calgary, AB, Canada.
15Natl Ctr Atmospher Res, POB 3000, Boulder, CO 80307 USA.
16Univ Colorado, Astrophys & Planetary Sci Dept, Boulder, CO 80309 USA.
17Univ Colorado, Lab Atmospher & Space Phys, Boulder, CO 80309 USA.
18Delft Univ Technol, Fac Aerosp Engn, Delft, Netherlands.
19Inst Space Sci, Bucharest, Romania.
20Univ Colorado, Ann & HJ Smead Dept Aerosp Engn Sci, Boulder, CO 80309 USA.
21Univ Oslo, Dept Phys, Oslo, Norway.
22Univ Bergen, Inst Phys & Technol, Bergen, Norway.
23Tech Univ Denmark, DTU Space, Copenhagen, Denmark.
24NASA, Goddard Space Flight Ctr, Heliophys Sci Div, Greenbelt, MD USA.
25Univ Potsdam, Fac Sci, Potsdam, Germany.
26Univ Oulu, Sodankyla Geophys Observ, Sodankyla, Finland.
27Swedish Inst Space Phys IRF, Kiruna, Sweden.
Format: article
Version: published version
Access: open
Online Access: PDF Full Text (PDF, 6.2 MB)
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Language: English
Published: Copernicus Publications, 2021
Publish Date: 2021-04-28


The lower-thermosphere–ionosphere (LTI) system consists of the upper atmosphere and the lower part of the ionosphere and as such comprises a complex system coupled to both the atmosphere below and space above. The atmospheric part of the LTI is dominated by laws of continuum fluid dynamics and chemistry, while the ionosphere is a plasma system controlled by electromagnetic forces driven by the magnetosphere, the solar wind, as well as the wind dynamo. The LTI is hence a domain controlled by many different physical processes. However, systematic in situ measurements within this region are severely lacking, although the LTI is located only 80 to 200 km above the surface of our planet. This paper reviews the current state of the art in measuring the LTI, either in situ or by several different remote-sensing methods. We begin by outlining the open questions within the LTI requiring high-quality in situ measurements, before reviewing directly observable parameters and their most important derivatives. The motivation for this review has arisen from the recent retention of the Daedalus mission as one among three competing mission candidates within the European Space Agency (ESA) Earth Explorer 10 Programme. However, this paper intends to cover the LTI parameters such that it can be used as a background scientific reference for any mission targeting in situ observations of the LTI.

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Series: Annales geophysicae
ISSN: 0992-7689
ISSN-E: 1432-0576
ISSN-L: 0992-7689
Volume: 39
Issue: 1
Pages: 189 - 237
DOI: 10.5194/angeo-39-189-2021
Type of Publication: A1 Journal article – refereed
Field of Science: 115 Astronomy and space science
1171 Geosciences
Funding: This research has been supported by the European Space Agency (ESA/ESTEC) contract number 4000127346/19/NL/IA with the Democritus University of Thrace for the Daedalus science and requirements consolidation study, in the framework of the Earth Explorer 10 Phase-0 feasibility studies (PI: Theodoros Sarris). Further support was provided by the European Space Agency (grant nos. 4000127660 MAGICS, and 4000118383 SIFACIT), the European Research Council (grant no. 682068-PRESTISSIMO), the Academy of Finland, Luonnontieteiden ja Tekniikan Tutkimuksen Toimikunta (grant nos. 309937 and 312351), the National Science Foundation, USA (grant nos. 1852977, OPP-1443726, and AGS-1552153), NASA (grant nos. NNX16AB82G, 80NSSC20K0601, 80NSSC20K0633, and 80NSSC17K0007), the Research Council of Norway (grant nos. 267408 and 275653), and the Programme National Soleil-Terre de l'Institut des Sciences de l'Univers (PNST/INSU).
Copyright information: © Author(s) 2021. This work is distributed under the Creative Commons Attribution 4.0 License.