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IRI is updated yearly. IRI is more accurate in describing the variation of the electron density from bottom of the ionosphere to the altitude of maximum density than in describing the total electron content (TEC). Since 1999 this model is "International Standard" for the terrestrial ionosphere (standard TS16457).
Total electron content (TEC) is an important descriptive quantity for the ionosphere of the Earth. TEC is the total number of electrons integrated between two points, along a tube of one meter squared cross section , i.e., the electron columnar number density .
For a specified geographic location, time, and date, IRI provides average monthly values for electron density, electron temperature and ion temperature, and the molecular composition of the ions in the range of altitudes from 50 km to 2000 km. [1] The latest standard is IRI-2012. [1] [2] A new version, IRI-2016, has since been released. [3]
As with other ionospheric sectors, 'layer' implies a concentration of plasma, while 'region' is the volume that contains the said layer. The F region contains ionized gases at a height of around 150–800 km (100 to 500 miles) above sea level, placing it in the Earth's thermosphere , a hot region in the upper atmosphere , and also in the ...
Electron density or electronic density is the measure of the probability of an electron being present at an infinitesimal element of space surrounding any given point. It is a scalar quantity depending upon three spatial variables and is typically denoted as either ρ ( r ) {\displaystyle \rho ({\textbf {r}})} or n ( r ) {\displaystyle n ...
Here R is the mean Earth radius, H is the mean height of the ionosphere shell. The IPP or Ionospheric Pierce Point is the altitude in the ionosphere where electron density is greatest. [1] These points can change based on factors like time of day, solar activity, and geographical location, which all influence ionospheric conditions. [2]
Critical frequency is the highest magnitude of frequency above which the waves penetrate the ionosphere and below which the waves are reflected back from the ionosphere. It is denoted by " f c ". Its value is not fixed and it depends upon the electron density of the ionosphere.
In this phase, electron density in the ionosphere, particularly in higher altitude layers such as F1 and F2 will increase. Ionisation in the positive phase will be less apparent due to the increase of electron density. [13] Positive phase ionospheric storms have a longer duration and are more prevalent in winter. [13]