IRI: Empirical quiet-time model of foF2 critical frequency as 2D maps in Jones-Gallett formalism

Description

Capabilities

• Jones-Gallet empirical climate model of 2D global O-wave Critical Frequency of the F2-layer

  CriticalFrequency_F2-Layer

  Observed Property

  CriticalFrequency_F2-Layer

  Dimensionality Instance

  2DMap

  Dimensionality Timeline

  2DAnimation

  Units

  MHz

Processing Input Parameters

R12_pre-2015

This IRI model computation requires the old-style 13-month smoothed International SunSpot Number (ISSN) value R12, prior to redefinition of the sunspot number computation by WDC-SILSO in June 2015. It is therefore required to obtain R12 data from WDC-SILSO first, then scale down by a factor of 0.7. Monthly updates of the ISSN data is required. Instead, consider using IG index when available (see below).

IG_ionosonde-provided

This IRI foF2 model computations may use IG index instead of R12. IG is an "effective" sunspot number derived by tweaking the standard R12 value into the best match to the monthly median noon foF2 values from 13 ionosonde observatories. As in 2022, IG index values are computed and released daily by E-CHAIM project at University of New Brunswick, Canada (https://chain-new.chain-project.net/echaim_downloads/ig_rz.dat). Correspondingly, regular updates of the IG data file are required for IRI to operate correctly.

IGRF

This IRI model computation requires 2D global map of modip (modified dip) of the Earth's magnetic field. The International Geomagnetic Reference Field (IGRF) is a commonly used model of the Earth's main magnetic field that provides modip calculation. Regular updates of IGRF expansion coefficients (every 5 years) are required.

Coefficients

This IRI model computation requires a set of expansion coefficients stored as a local file. Two options are usually provided: the original CCIR-1967 coefficients as described in ITU-R recommendation P1239-3 (2012/02), or their later update known as URSI-1988.

Data Levels

• L4