Sodankylä ionospheric tomography dataset 2003–2014

At Sodankylä Geophysical Observatory, we have made continuous ionospheric tomography measurements for one solar cycle. Because of this big database, we have written a dataset paper, and, the paper is now online as a discussion paper in Geoscientific Instrumentation, Methods and Data Systems (an EGU journal).

The number of satellite overflights over the 
whole observation period with respect to 
minimum threshold elevation. 

In the paper, we show that ionospheric tomography results are modulated by the solar cycle, which can be seen from the analysed data. We have altogether measured over 66,000 flybys of the Russian COSMOS beacon satellites. For the analysis, we used only north-to-south flights, because they are along the SGO ionospheric tomography chain.

In the figure below, we have plotted the analysed total electron content (VTEC) values over Kokkola, Finland (averaged from 11-14 MLT). These are compared to the well-established Sun activity indices, the sunspot number and the solar flux index F10.7.

The paper is fully citable as:

Norberg, J., Roininen, L., Kero, A., Raita, T., Ulich, T., Markkanen, M., Juusola, L., and Kauristie, K.: Sodankylä ionospheric tomography dataset 2003–2014, Geosci. Instrum. Method. Data Syst. Discuss., 5, 385-404, doi:10.5194/gid-5-385-2015, 2015.

... and here's the abstract:

Sodankylä Geophysical Observatory has been operating a tomographic receiver network and collecting the produced data since 2003. The collected dataset consists of phase difference curves measured from Russian COSMOS dual-frequency (150/400 MHz) low-Earth-orbit satellite signals, and tomographic electron density reconstructions obtained from these measurements. In this study vertical total electron content (VTEC) values are integrated from the reconstructed electron densities to make a qualitative and quantitative analysis to validate the long-term performance of the tomographic system. During the observation period, 2003–2014, there were three-to-five operational stations at the Fenno-Scandinavian sector. Altogether the analysis consists of around 66 000 overflights, but to ensure the quality of the reconstructions, the examination is limited to cases with descending (north to south) overflights and maximum elevation over 60°. These constraints limit the number of overflights to around 10 000. Based on this dataset, one solar cycle of ionospheric vertical total electron content estimates is constructed. The measurements are compared against International Reference Ionosphere IRI-2012 model, F10.7 solar flux index and sunspot number data. Qualitatively the tomographic VTEC estimate corresponds to reference data very well, but the IRI-2012 model are on average 40 % higher of that of the tomographic results.

VTEC values over Kokkola averaged from 11-14 MLT 
versus corresponding IRI-2012 model values, 
sunspot number and solar flux index F10.7. 

Ionosfäärin tomografiamittauksiin uusia laitteistoja ja laskentamenetelmiä

Ilmatieteen laitoksen vetämässä ionosfääritomografiaprojektissa TomoScandissa on kehitetty uusia menetelmiä ionosfäärin kuvantamiseen. Ilmatieteen laitoksen lehdistötiedote projektin viimeisimmistä käänteistä julkaistiin tänään IL:n sivuilla. Lehdistötiedote löytyy täältä.

Projektin tieteellisiä tuloksia on raportoitu Radio Sciencessa:

J. Norberg, L. Roininen, J. Vierinen, O. Amm, D. McKay-Bukowski, M. Lehtinen.
Ionospheric tomography in Bayesian framework with Gaussian Markov random field priors.
Radio Science 01/2015, DOI: 10.1002/2014RS005431.
http://onlinelibrary.wiley.com/doi/10.1002/2014RS005431/abstract

J. Vierinen, J. Norberg, M. S. Lehtinen, O. Amm, L. Roininen, A. Väänänen, P. J. Erickson, D. McKay‐Bukowski.
Beacon satellite receiver for ionospheric tomography.
Radio Science 10/2014, DOI: 10.1002/2014RS005434.
http://onlinelibrary.wiley.com/doi/10.1002/2014RS005434/abstract

SGO:n ja Ilmatieteen laitoksen 11 vastaanotinasemaa
sijaitsevat Virosta Huippuvuorille.

Early access: Ionospheric tomography paper

The early-access version of the paper:

J. Norberg, L. Roininen, J. Vierinen, O. Amm, D. McKay-Bukowski and M. Lehtinen, Ionospheric tomography in Bayesian framework with Gaussian Markov random field priors, Radio Science (2015) DOI: 10.1002/2014RS005431

is available here: http://onlinelibrary.wiley.com/enhanced/doi/10.1002/2014RS005431/.


Here is the abstract:

We present a novel ionospheric tomography reconstruction method. The method is based on Bayesian inference with the use of Gaussian Markov random field priors. We construct the priors as a system of stochastic partial differential equations. Numerical approximations of these equations can be represented with linear systems with sparse matrices, therefore providing computational efficiency. The method enables an interpretable scheme to build the prior distribution based on physical and empirical information on the structure of the ionosphere. We show through synthetic test cases in a two-dimensional setup of latitude-altitude slices how this method can be applied to satellite-based ionospheric tomography and how information about the structure of the ionosphere can be implemented in the prior. The technique is capable of being easily extended to multi-frequency tomographic analysis, or used for the inclusion of other data sets of ionospheric electron density, such as ground-based observations by radars or ionosondes.

Ionospheric tomography in Bayesian framework with Gaussian Markov random field priors

We are pleased to report that our latest study on ionospheric tomography with a GMRF-type prior information has been accepted for publication in Radio Science. The current reference is:

J. Norberg, L. Roininen, J. Vierinen, O. Amm, D. McKay-Bukowski and M. Lehtinen, Ionospheric tomography in Bayesian framework with Gaussian Markov random field priors, Radio Science, Accepted January 2015.

We will post a link to the early-access version as soon as it is available. This is a companion paper of the so-called "tomography receiver paper" reported in Radio Science earlier. It is available here.

Current tomography project titled 'TomoScand' is a collaboration project between Finnish Meteorological Institute, Sodankylä Geophysical Observatory and MIT Haystack Observatory.

Here is a schematic plot of ionospheric tomography, where the objective
is to probe the ionosphere beacon 150/400 MHz satellite signals and to estimate
the electron density ~60-1000 km above the Earth.

EISCAT, KAIRA and TomoScand experiment / CME Impact 14 UT Fri

As per the Wednesday X1.6 Flare, we expect the CME impact on Earth at ~14 UT Friday. Following experiments are in our task list (provided acceptance by EISCAT):

1. EISCAT ESR (Svalbard): will start up in the morning - run at least till midnight. https://www.eiscat.se/raw/rtg/gup.cgi?E
2. EISCAT Mainland - provided maintenance service completed and HQ acceptance:
  a) VHF MANDA D-region experiment, vertical, USRP sampling, EISCAT recording
  b) UHF BELLA F-region experiment, field-aligned, USRP sampling, EISCAT recording
3. KAIRA Riometry
4. FMI TomoScand ionospheric tomography (with COSMOS 2414 Satellite flyby ~14 UT over Tromsø + other viable flybys)