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Research - Arve Aksnes

Measuring the neutral temperature in the lower thermosphere

Using the rotational structure of the N2 LBH bands from HITS observations aboard the ARGOS satellite, we have developed a new technique to measure the neutral temperature in the lower thermosphere (between ~150 and 270 km). By performing a best fit model to the HITS observations within the wavelength region of 144.0-155.0 nm, a rotational temperature Tr may be determined. Based on accepted principles of molecular spectroscopy and experimental laboratiry results, this parameter is expected to have a one-to-one relationship with the neutral temperature Tn.
A. Aksnes, R. Eastes, S. Budzien, and K. Dymond,
Neutral temperatures in the lower thermosphere from N2 Lyman-Birge-Hopfield (LBH) band profiles
Geophys. Res. Lett., 33, L15103, doi:10.1029/2006GL026255, 2006.
  • PDF (172 kB)

    • Importance of cascading for the N2 LBH excitation

    Under construction

    Instantaneous Global Conductance Maps

    From remote sensing of UV and X-ray emissions by the UVI and PIXIE cameras onboard the Polar satellite, we derive global maps of the precipitating electron energy spectra from less than 1 keV to 100 keV. Based on the electron spectra, we infer height profiles of the resulting ionization. Photoionization is also included in these calculations. We then generate instantaneous global maps of the Hall and Pedersen conductances. This technique allows us to study the time development of the conductances during geomagnetic substorms.
    A. Aksnes, J. Stadsnes, J. Bjordal, N. Østgaard, R. R. Vondrak, D. L. Detrick, T. J. Rosenberg, G. A. Germany, and D. Chenette,
    Instantaneous ionospheric global conductance maps during an isolated substorm.
    Annales Geophysicae, 20, 1181, 2002.
  • PDF (4.2 MB)
    • A. Aksnes, and J. Stadsnes,
    Instantaneous global conductances derived from PIXIE and UVI measurements.
    Space Research in Norway, 2000-2002.
  • WORD document (908 kB)

    • Effects of Energetic Electrons on the Ionospheric Electrodynamics

    Remote sensing of UV emissions gives good coverage of the precipitating electrons in the energy range of a few keV, responsible for the Pedersen conductance. X-ray measurements are needed to capture the high-energy tail of the energetic electrons from some tens of keV and up to 100 keV affecting the Hall conductance. The PIXIE X-ray camera on the Polar satellite is the only instrument providing global information about the energetic electron precipitation. Instantaneous global conductance maps derived with and without the inclusion of PIXIE X-ray data have been implemented in the Assimilative Mapping of Ionospheric Electrodynamics (AMIE) procedure to study the effects of energetic electrons on the ionospheric electrodynamics. This includes ionospheric conductances, the ionospheric electric field, the atmospheric Joule heating, and the auroral energy flux.
    A. Aksnes, J. Stadsnes, G. Lu, N. Østgaard, R. R. Vondrak, D. L. Detrick, T. J. Rosenberg, G. A. Germany, and M. Schulz,
    Effects of energetic electrons on the electrodynamics in the ionosphere.
    Annales Geophysicae, 22, 475, 2004.
  • PDF (7.0 MB)

    • Comparison of conductances derived using different techniques

    We have derived and compared conductances (and the electron density) above Tromsø, Norway, using EISCAT radar data and remote sensing of UV and X-ray emissions (UVI and PIXIE on the Polar satellite).
    A. Aksnes, J. Stadsnes, N. Østgaard, G. A. Germany, K. Oksavik, R. R. Vondrak, A. Brekke, and U. P. Løvhaug,
    Height profiles of the ionospheric electron density derived using space-based remote sensing of UV and X-ray emissions, and EISCAT radar data: A ground-truth experiment
    Journal of Geophysical Research, 111 (A2), A02301, doi:10.1029/2005JA011331, 2006.
  • PDF (381 kB)
    • Another comparison approach has also been performed, using the method of characteristics to derive conductances above Northern Scandinavia. The method of characteristics is a ground-based technique to derive the ionospheric conductances, using electric field measurements and ground magnetometer data.
    A. Aksnes, O. Amm, J. Stadsnes, N. Østgaard, G. A. Germany, R. R. Vondrak, and I. Sillanpaa,
    Ionospheric conductances derived from satellite measurements of auroral UV and X-ray emissions, and ground-based electromagnetic data: A comparison.
    Annales Geophysicae, 23, 343, 2005.
  • PDF (from Annales Geophysicae)

    • Analysis of mesoscale ionospheric electrodynamics of omega bands

    An omega band is an auroral phenomena typically occuring on the morning side diffuse aurora in the recovery phase of substorms. Auroral omega bands are periodic, wave-like undulations of the poleward boundary of the aurora, and the name omega is due to the dark areas between the auroral tongues, which resemble the form of the inverted capital greek letter. We use ground-based electromagnetic data from the MIRACLE and BEAR networks and satellite optical observations from the UVI and PIXIE instruments on the Polar satellite to study the ionospheric electrodynamics during an omega band event over Northern Scandinavia.
    0. Amm, A. Aksnes, J. Stadsnes, N. Østgaard, R. R. Vondrak, G. A. Germany, G. Lu, and A. Viljanen,
    Mesoscale ionospheric electrodynamics of omega bands determined from ground-based electromagnetic and satellite optical observation.
    Annales Geophysicae, 23, 325, 2005.
  • PDF (from Annales Geophysicae)
    • 0. Amm, A. Aksnes, J. Stadsnes, N. Østgaard, R. R. Vondrak, G. A. Germany, and I. Sillanpaa,
    Observations and analysis of ionospheric electrodynamics during a substorm recovery phase using the MIRACLE network.
    Proc. Seventh International Conf. on Substorms (ICS-7), Levi, Finland, March 21-27, 2004, Finnish Meterological Institute report 2004:5, p. 87-94, 2004..
  • PDF (2.1 MB)
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