The Empirical-Canadian High Arctic Ionospheric Model

E-CHAIM is intended as an alternative to the use of the International Reference Ionosphere (IRI) model at high latitudes. To this end, the model represents ionospheric electron density in the region above 50°N geomagnetic latitude. The model is composed of several sub-models, each representing a key feature in the ionospheric electron density profile. Like the IRI, NmF2 and hmF2 are chosen as the anchor point of the profile, with all other components representing characteristics with respect to the F2 peak density and height. Each of these sub-models feature a spherical cap harmonic expansion in the new Altitude-Adjusted Corrected Geomagnetic (AACGM) coordinates of Shepherd [2014], calculated at 350km altitude, for the representation of the horizontal structure of the modelled parameter. All further references to geomagnetic coordinates in this text refer to these 350km AACGM coordinates. The order and degree of this expansion is determined experimentally, based on the amount, distribution, and quality of available data. The seasonal variability is modelled by a Fourier expansion and solar cycle variability is modelled via a function of solar F10.7 cm flux and IG ionospheric index.

  • Shepherd, S.G., (2014), Altitude-Adjusted Corrected Geomagnetic Coordinates: Definition and Functional Approximations, J. Geophys. Res., 119, doi:10.1002/2014JA020264

The model papers include:

  • Themens, D.R., P.T. Jayachandran, A.M. McCaffrey, B. Reid, and R.H. Varney (2019). A bottomside parameterization for the Empirical Canadian High Artic Ionospheric Model (E-CHAIM), Radio Sci., doi: 10.1029/2018RS006748
  • Themens, D.R., P.T. Jayachandran, I. Galkin, and C. Hall (2017). The Empirical Canadian High Arctic Ionospheric Model (E-CHAIM): NmF2 and hmF2, J. Geophys. Res. Space Physics, doi: 10.1002/2017JA024398
  • Themens, D.R., et al. (2018), Topside Electron Density Representations for Middle and High Latitudes: A Topside Parameterization for E‐CHAIM Based on the NeQuick, Journal of Geophysical Research: Space Physics, 123, 2, 1603-1617.


The E-CHAIM software is available both as a web application and as a series of downloadable, standalone programs. These programs are available for IDL, Matlab and C. The web application is publicly available at the following link:

E-CHAIM Web Application - using version 3.2.2 of the C library


The standalone software is available at no cost, but you need to register in order to download it and we ask all users to please state the version of the model in any publication or scientific use of E-CHAIM. Once you have registered, you can download the software at the following link:

E-CHAIM Standalone Software


Update Schedule: Scheduled updates to E-CHAIM will occur on a biannual basis. The model's next update is scheduled for October 1st, 2019. Any urgent updates that need to be incorporated off of this schedule will be announced via email.


Supplementary Support Software
You can find additional files to support work done with the E-CHAIM data and models on the Supplementary Support Software page.

Rules of the Road

When using the Empirical-Canadian High Arctic Ionospheric Model (E-CHAIM) for scientific purposes, we ask users to adhere to the following guidelines:

  • List the version number for the version of the E-CHAIM code you are using (ex: v1.4.0).
  • While we do not ask to be included as co-authors to your publications using the model, we do ask that you let us know after you have published a paper that uses the model. This goes a long way to helping us justify further funding support to keep the model available and free.
  • Please include the following acknowledgement in publications using the model: “E-CHAIM is supported under Defence Research and Development Canada contract number W7714‐186507/001/SS and is maintained by the Canadian High Arctic Ionospheric Network (CHAIN) with operations support from the Canadian Space Agency.”

E-CHAIM Project Lead:

David Themens - This email address is being protected from spambots. You need JavaScript enabled to view it.