Space systems — Space environment (natural and artificial) — The Earth's ionosphere model: international reference ionosphere (IRI) model and extensions to the plasmasphere

ISO 16457:2014 provides guidance to potential users for the specification of the global distribution of ionosphere densities and temperatures, as well as the total content of electrons in the height interval from 50 km to 1 500 km. It includes and explains several options for a plasmaspheric extension of the model, embracing the geographical area between latitudes of 80°S and 80°N and longitudes of 0°E to 360°E, for any time of day, any day of year, and various solar and magnetic activity conditions.

Systèmes spatiaux — Environnement spatial (naturel et artificiel) — Guidage sur le modèle de l'ionosphère internationale de référence (IRI) et extensions à la plasmasphère

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Corrected version
Space systems — Space environment
(natural and artificial) — The Earth’s
ionosphere model: international
reference ionosphere (IRI) model and
extensions to the plasmasphere
Systèmes spatiaux — Environnement spatial (naturel et artificiel)
— Guidage sur le modèle de l’ionosphère internationale de référence
(IRI) et extensions à la plasmasphère
Reference number
ISO 16457:2014(E)
ISO 2014

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ISO 16457:2014(E)

© ISO 2014
All rights reserved. Unless otherwise specified, no part of this publication may be reproduced or utilized otherwise in any form
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Published in Switzerland
ii © ISO 2014 – All rights reserved

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ISO 16457:2014(E)

Contents Page
Foreword .iv
Introduction .v
1 Scope . 1
2 Terms and definitions . 1
3 Abbreviated terms . 3
4 General considerations . 3
5 Applicability . 3
6 Model description . 4
7 Model content and inputs . 4
8 Plasmasphere extension of the IRI model . 5
8.1 General . 5
8.2 Global Core Plasma Model (GCPM) . 5
8.3 Global Plasmasphere Ionosphere Density (GPID) model . 5
8.4 IMAGE/RPI plasmasphere model . 5
8.5 IZMIRAN plasmasphere model . 5
9 Accuracy of the model . 6
Annex A (informative) Brief introduction to ionosphere and plasmasphere physics.7
Annex B (informative) Physical models. 9
Bibliography .12
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ISO 16457:2014(E)

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to Trade (TBT) see the following URL: Foreword - Supplementary information
The committee responsible for this document is Technical Committee ISO/TC 20, Aircraft and space
vehicles, Subcommittee SC 14, Space systems and operations.
This first edition of ISO 16457 cancels and replaces ISO/TS 16457:2009, which has been technically
This corrected version of ISO 16457:2014 incorporates the following correction.
In the Foreword, the following sentence has been added regarding the revision:
This first edition of ISO 16457 cancels and replaces ISO/TS 16457:2009, which has been technically
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ISO 16457:2014(E)

Guided by the knowledge gained from empirical data analysis, this International Standard provides
guidelines for specifying the global distribution of electron density, electron temperature, ion
temperature, ion composition, and total electron content through the Earth’s ionosphere and
plasmasphere. The model recommended for the representation of these parameters in the ionosphere is
the international reference ionosphere (IRI).
IRI is an international project sponsored by the Committee on Space Research (COSPAR) and the
International Union of Radio Science (URSI). These organizations formed a working group in the late
1960s to produce an empirical standard model of the ionosphere based on all available data sources. The
IRI Working Group consists of more than 50 international experts representing different countries and
different measurement techniques and modelling communities. The group meets annually to discuss
improvements and additions to the model. As a result of these activities, several steadily improved
editions of the model have been released (see References [1], [2], [3], [5], [6], [18], [19], [20], and [53]).
For a given location over the globe, time, and date, IRI describes the monthly averages of electron density,
+ + + + + +
electron temperature, ion temperature, and the percentage of O , H , He , N , NO , O , and Cluster ions in
the altitude range from 50 km to 1 500 km. In addition, IRI provides the electron content by numerically
integrating over the electron density height profile within user-provided integral boundaries. IRI is a
climatological model describing monthly average conditions. The major data sources for building the
IRI model are the worldwide network of ionosondes, the powerful incoherent scatter radars, the topside
sounders, and in situ instruments flown on several satellites and rockets. This International Standard
also presents several empirical and semi-empirical models that can be used to extend the IRI model to
plasmasphere altitudes.
One advantage of the empirical approach is that it solely depends on measurements and not on the
evolving theoretical understanding of the processes that determine the electron and ion densities
and temperatures in the Earth’s ionosphere. A physical model can help to find the best mathematical
functions to represent variations of these parameters with altitude, latitude, longitude, time of day, day
of year, and solar and magnetic activity.
IRI is recommended for international use by COSPAR and URSI. The IRI model is updated and improved
as new data and new sub-models become available. This International Standard provides a common
framework of the International Standard of the Earth’s ionosphere and plasmasphere for the potential
1) The homepage of the IRI project is at The IRI homepage provides access to the IRI
FORTRAN computer code and an interactive system for computing and plotting IRI parameters online A special
PC Windows version of IRI-2001 with multiple plotting options is available from the University of Massachusetts
Lowell at[16]. The IRI-Plas code including IRI extension to the plasmasphere is
available at
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Space systems — Space environment (natural and
artificial) — The Earth’s ionosphere model: international
reference ionosphere (IRI) model and extensions to the
1 Scope
This International Standard provides guidance to potential users for the specification of the global
distribution of ionosphere densities and temperatures, as well as the total content of electrons in the
height interval from 50 km to 1 500 km. It includes and explains several options for a plasmaspheric
extension of the model, embracing the geographical area between latitudes of 80°S and 80°N and
longitudes of 0°E to 360°E, for any time of day, any day of year, and various solar and magnetic activity
2 Terms and definitions
For the purposes of this document, the following terms and definitions apply.
region of the Earth’s atmosphere in the height interval from 50 km to 1 500 km containing weakly
ionized cold plasma
−3 +
torus of cold, relatively dense (>10 cm ) plasma of mostly H in the inner magnetosphere, which is
trapped on the Earth’s magnetic field lines and co-rotates with the Earth
Note 1 to entry: Cold plasma is considered to have an energy of between a few electronvolts and a few dozen
outward boundary of the plasmasphere located at between two and six earth radii from the centre of
the Earth and formed by geomagnetic field lines where the plasma density drops by a factor of 10 or
more across a range of L-shells of as little as 0,1
Note 1 to entry: The L-shell is a parameter describing a particular set of planetary magnetic field lines, often
describing the set of magnetic field lines which cross the Earth’s magnetic equator at a number of Earth-radii equal
to the L-value, e.g. “L = 2” describes the set of the Earth’s magnetic field lines which cross the Earth’s magnetic
equator two earth radii from the centre of the Earth.
solar activity
series of processes occurring in the sun’s atmosphere which affect the interplanetary space and the
Note 1 to entry: The level of solar activity is characterized by indices.
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ISO 16457:2014(E)

ionospheric storm
storm lasting about a day, documented by depressions and/or enhancements of the ionospheric electron
density during various phases of the storm
Note 1 to entry: Ionospheric storms are the ultimate result of solar flares or coronal mass ejections, which produce
large variations in the particle and electromagnetic radiation that hit Earth’s magnetosphere and ionosphere, as
well as large-scale changes in the global neutral wind, composition, and temperature.
sunspot number
R, alternatively called Ri or Rz, is a daily index of sunspot activity defined as R=k(10g+s) where s is the
number of individual spots, g is the number of sunspot groups, and k is an observatory factor
12-month running mean of monthly sunspot number
kp index
planetary three-hour index of geomagnetic activity characterizing the disturbance in the Earth’s
magnetic field over three-hour universal time (UT) intervals
Note 1 to entry: The index scale is uneven quasi-logarithmic and expressed in numbers from 0 to 9.
ap index
three-hour UT amplitude index of geomagnetic variation equivalent to kp
Note 1 to entry: It is expressed in 1 nT to 400 nT.
total electron content
integral number of electrons in the column from a lower altitude boundary to an upper boundary
Note 1 to entry: Typically the integral is taken from the lower boundary of the ionosphere (65 km during daytime
and 80 km during night time) to the plasmapause.
16 −2
Note 2 to entry: It is expressed in units of 10 electrons m (TECU).
Ionosphere global index
[56] [7]
ionosphere-effective sunspot number that is obtained by adjusting the CCIR maps to global
ionosonde measurements of the F2 plasma critical frequency foF2
12-month running mean of monthly ionosphere-effective sunspot number
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ISO 16457:2014(E)

3 Abbreviated terms
IRI international reference ionosphere
ELF extremely low frequency (less than 3 kHz)
VLF very low frequency (3 kHz to 30 kHz)
LF low frequency (30 kHz to 300 kHz)
MF medium frequency (300 kHz to 3 MHz)
HF high frequency (3 MHz to 30 MHz)
VHF very high frequency (30 MHz to 300 MHz)
UHF ultra high frequency (300 MHz to 3 000 MHz)
4 General considerations
This model for the representation of the ionospheric and plasmaspheric plasma parameters is important
to a wide spectrum of applications. Electromagnetic waves travelling through the ionized plasma at the
Earth’s environment experience retardation and refraction effects. A remote sensing technique relying
on signals traversing the ionosphere and plasmasphere therefore needs to account for the ionosphere-
plasmasphere influence in its data analysis. Applications can be found in the disciplines of altimetry,
radio astronomy, satellite communication, navigation and orbit determination.
Radio signals, transmitted by modern communication and navigation systems can be heavily disturbed
by space weather hazards. Thus, severe temporal and spatial changes of the electron density in the
ionosphere and plasmasphere can significantly degrade the signal quality of various radio systems
which even can lead to a complete loss of the signal. Model-based products providing specific space
weather information, in particular now- and forecast of the ionospheric state, serve for improvement of
the accuracy and reliability of impacted communication and navigation systems.
For high frequency radio communication, a good knowledge of the heights and plasma frequencies of
the reflective layers of the ionosphere and the plasmasphere is critical for continuous and high-quality
radio reception. High frequency communication remains of great importance in many remote locations
of the globe. The model helps to estimate the effect of charged particles on technical devices in the
Earth’s environment and defines the ionosphere-plasmasphere operational environment for existing
and future systems of radio communication, radio navigation, and other relevant radio technologies in
the medium and high frequency ranges.
5 Applicability
There are a multitude of operational usages for ionospheric models, of which the most important are
outlined in this clause. Operators of certain navigational satellite systems such as GPS (USA), GLONASS
(Russia), BeiDou (China), and GALILEO (Europe) require ionospheric predictions to mitigate losses of
navigation signal phase and/or amplitude lock, as well as to maintain accurate orbit determination for
all its satellites. Users of global navigation satellite systems need precise ionospheric models to increase
the accuracy and to reduce the precise positioning convergence time. Radio and television
operators using MF, HF, VHF, UHF satellite, or ground stations require ionospheric parameters for
efficient communications and for reducing interferences. Space weather forecasters have a great need
for accurate ionospheric models to support their customers with reliable and up to the minute space
weather information. Ionospheric models are also used in the aeronautical and space system industries
2) GPS: Global Positioning System; GLONASS: Global Orbiting Navigation Satellite System; GALILEO: European
Global Satellite Navigation System; BeiDou: BeiDou Navigation Satellite System.
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ISO 16457:2014(E)

and by governmental agencies performing spacecraft design studies. Here the models help to estimate
surface charging, sensor interference, and satellite anomaly conditions.
Users also apply ionospheric models to mitigate problems with HF communications, HF direction finding,
radar clutter, and disruption to ELF/VLF communications with underwater vehicles. Insurance companies
estimating the cost of protecting human health in space and satellites make use of ionospheric models.
Scientists using remote sensing measurement techniques in astronomy, biology, geology, geophysics,
and seismology require parameter estimates for compensating the effects of the ionosphere on their
observations. An ionospheric model might be also used to evaluate tomographic, radio occultation, and
other similar techniques, by providing the ground-truth background model for test runs. Amateur radio
operators, as well as students and teachers in space research and applications, also use ionosphere
parameters. This International Standard might be also applied for ray-path calculations to assess the
performance of a particular ground-based or space-borne systems. Monthly medians of ionospheric
parameters are useful for HF circuit and service planning, while maps for individual days and hours aid
frequency management and retrospective studies.
6 Model description
The first version of the IRI model, IRI-1979, and its mathematical build-up is described in References [18],
[19], and [20]. The most detailed description of the model and the mathematical formulas and methods
used is given in a 155-page report about IRI-1990. The next significant updates of the model were
[5] [3]
introduced with IRI-1995 and IRI-2000. The core of the version of IRI proposed for this International
Standard, IRI-2007, is described in detail in References [53] and [54].
IRI-related research efforts and applications of the IRI model are presented and discussed during
annual IRI workshops , with each workshop focusing on a specific modelling topic. Papers from these
workshops have been published in dedicated issues of the journal Advances in Space Research . Recent
reviews of IRI and other ionospheric models can be found in References [4], [51], [52], and [54].
7 Model content and inputs
The IRI model uses a modular approach combining sub-models for the different parameters in different
altitude regimes. Examples of such sub-models are:
— International Telecommunication Union ITU-R (former CCIR) model for the F2 layer critical
frequency foF2 (directly related with the F2 peak electron density, in m ) and for the propagation
factor M(3000)F2 (inversely correlated with the peak height, in km) ; IRI recommends use of the
CCIR model above continental areas and recommends use of the URSI model above ocean areas,
because the URSI model produces better results than the CCIR model in these areas; Instead of the
CCIR-recommended sunspot number IRI uses the global ionosphere index IG because it gives
better results especially at high solar activities,
— COSPAR International Reference Atmosphere (CIRA) model for the neutral temperature,
— STORM model for storm-time updating of the F2 layer peak density , and
— International Geomagnetic Reference Field (IGRF) model of the International Association of
Geomagnetism and Aeronomy (IAGA) for the magnetic coordinates (http://www.ngdc.noaa.
The IRI model requires the following indices as input parameters:
— R12, the 12-month running mean of sunspot number R;
— IG12, the 12-month running mean of global ionosphere index IG;
3) Information about past and future workshops can be found on the IRI homepage (, which
also provides access to the final report from each workshop and to a bibliography of IRI-related papers and issues
of Advances in Space Research.
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ISO 16457:2014(E)

— ap, the 3-hourly planetary magnetic indices for the prior 33 h.
These indices can either be found automatically from the indices files that are included with the IRI
software package and that are updated quarterly, or the user can provide his/her own input values for
these indices. For R12 and IG12, the indices file starts from January 1958 and include indices prediction
for two years ahead. For ap, the index values start from January 1960 .
In addition, model users have the options to use measured peak parameters to update the IRI profile,
including the F2, F1, and E layer critical frequencies (or electron densities), the F2 peak height [or
M(3000)F2 propagation factor], and the E peak height. In this way, real-time IRI predictions can be
obtained if the real-time peak parameters are available. The total electron content (TEC) is obtained by
numerical integration from the model’s lower boundary (65 km during daytime and 80 km during night
time) to the user-specified upper boundary.
8 Plasmasphere extension of the IRI model
8.1 General
The models described in 8.2 to 8.5 have been proposed as plasmasphere extension of the IRI model.
8.2 Global Core Plasma Model (GCPM)
GCPM-2000 is an empirical description of thermal plasma densities in the plasmasphere, plasmapause,
magnetospheric trough, and polar cap. GCPM-2000 uses the kp index and is coupled to IRI in the
transition region 500 km to 600 km .
8.3 Global Plasmasphere Ionosphere Density (GPID) model
The semi-empirical GPID model includes IRI below 500 km to 600 km and extends it with
theoretical plasmasphere electron density description along the field lines. Authors report on drawbacks
of merging of the IRI with the plasmasphere part of GPID .
8.4 IMAGE/RPI plasmasphere model
[15] [21]
The IMAGE/RPI plasmasphere model is based on radio plasma imager (RPI) measurements of
the electron density distribution along magnetic field lines. A plasmaspheric model is evolving for up to
about four earth radii. The depletion and refilling of the plasmasphere during and after magnetic storms
is described in Reference [22]. A power profile model as function of magnetic activity was developed
from RPI observations for the polar cap region.
8.5 IZMIRAN plasmasphere model
The IZMIRAN model is an empirical model based on whistler and satellite observations. It
presents global vertical analytical profiles of electron density and temperature smoothly fitted to IRI
electron density profiles at an altitude of topside half peak density (400 km to 600 km for electron density
and 400 km for electron temperature) and extended towards the plasmapause (up to 36 000 km). For
the smooth fitting of the two models, the shape of the IRI topside electron density profile is improved
4) For ap, the index values currently lag a few months behind, because of the problems in obtaining and predicting
this index.
5) A FORTRAN code implementation of GCPM that includes all regions except the polar cap is available from
6) The GPID model source code was written in MATLAB software but is not currently available for release.
7) IZMIRAN: Institute of Terrestrial Magnetism, Ionosphere and Radio Waves Propagation, Russian Academy of
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ISO 16457:2014(E)

using ISIS-1, ISIS-2, and IK-19 satellite inputs. The plasmasphere model depends on solar activity
and magnetic activity (kp-index) .
9 Accuracy of the model
The IRI model has been built to represent the monthly average behaviour of space plasma. Efforts are
underway to also include a quantitative description of the monthly variability in IRI. As variability
measure, either the relative standard deviation or upper/lower quartiles and deciles will be used.
The accuracy of the IRI electron density model is typically (given here as standard deviation divided by
monthly median in %):
— 50 % to 80 % at heights from 65 km to 95 km;
— 5 % to 15 % at heights from 100 km to 200 km during daytime;
— 15 % to 30 % at heights from 100 km to 200 km during night time;
— 15 % to 25 % at heights from 200 km to 1 000 km at low and middle dip latitudes (<60°);
— 50 % to 80 % at heights from 200 km to 1 000 km at high dip latitudes (>60°).
8) ISIS: International Satellites for Ionospheric Studies; IK-19: Intercosmos-19 satellite.
9) Source code for this IRI ionosphere-plasmasphere version is available from the IZMIRAN web site http://ftp.
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ISO 16457:2014(E)

Annex A

Brief introduction to ionosphere and plasmasphere physics
The ionosphere and plasmasphere are conductive, ionized regions of the Earth’s atmosphere consisting
of free electrons and ions. The ionosphere and plasmasphere are embedded within the Earth’s magnetic
field and thus are constrained by interactions of the ionized particles with the magnetic field. The
ionization levels in this near-Earth space plasma are controlled by solar extreme ultraviolet (EUV)
radiation and particle precipitation. The dynamics of the neutral atmosphere plays a significant role
in causing movement of the ionized particles by collisions with neutral atoms and molecules from the
surrounding thermosphere. The ionosphere extends in altitude from about 65 km to about 1 500 km
and exhibits significant variations with local time, altitude, latitude, longitude, solar cycle, season,
and geomagnetic activity. At middle and low latitudes, the ionosphere is contained within a region of
closed field lines, whereas at high latitudes the geomagnetic field can reconnect with the interplanetary
magnetic field and thus open the ionosphere to the driving force of the solar wind.
Plasma flowing upwards from the oxygen-dominated topside ionosphere remains constrained by Earth’s
field lines of force co-rotating with the Earth and comprises the hydrogen-dominated plasmasphere
[25][26] + +
extended up to a few earth radii. The O /H transition height where the ion gas consists of an
equal percentage of both ions is often taken as the boundary between the ionosphere and plasmasphere.
These two regions of the upper atmosphere are strongly coupled through diffusion and resonant charge
+ + +
exchange reactions between O and H . At quiet conditions, H in the plasmasphere typically diffuses
down to the topside ionosphere at night and undergoes resonant charge exchange reactions with atomic
+ +
oxygen to produce O (downward flux). The O produced in this way can make a significant contribution
to the maintenance of the night time ionosphere, and works in combination with the meridional
component of the neutral wind. The depleted night time plasmasphere can be refilled during the day
through the reverse process; that is, the O ions flow up from the ionosphere, exchange charges with
the neutral hydrogen atoms to produce protons, and the protons are then stored in the p

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