Evaluation of the Sq Magnetic Field Variation Calculated by GAIA. Issue 4 (13th April 2018)

• Record Type: Journal Article
• Authors: Fujita, Shigeru; Murata, Yuka; Fujii, Ikuko; Miyoshi, Yasunobu; Shinagawa, Hiroyuki; Jin, Hidekatsu; Fujiwara, Hitoshi
• Is Part Of: Space weather. Volume 16:Issue 4(2018)
• Page Start: 376
• Page End: 390
• Publication Date: 2018-04-13
• Subjects: GAIA -- Sq magnetic field -- evaluation -- Earth's induction; Space environment -- Periodicals; 551.509992
• DOI: 10.1002/2017SW001745
• Languages: English
• ISSNs: 1542-7390

Abstract

Abstract: Magnetic variations calculated by the Ground‐to‐topside model of Atmosphere and Ionosphere for Aeronomy (GAIA) are compared with those observed at global magnetic observatory network in geomagnetic calm days in order to evaluate accuracy of the ionospheric current system calculated by GAIA. The calculated Y component magnetic variations can reproduce more than 50% of the observed variations at more than half observatories treated. In particular, GAIA can reproduce more than 75% of the observed Y component variations in the equinox, whereas there is tendency of low correlation of the waveform between the calculated and observed variations in the winter season. Next, GAIA reproduces so well of the X component variations at the low‐latitude observatories. Low correlation between the calculated and observed X component variations at middle‐latitude observatories seems to be caused by inaccurate determination of the position of the ionospheric Sq current vortex. Last, although the calculated Z component variations do not so well reproduce the observed ones compared with other component, GAIA can reproduce more than 50% of the observed Z component variation at about half observatories in general. Calculated amplitude of the horizontal magnetic variations (X and Y components) exhibit smaller than the observed one whereas that of the vertical variation (Z component) is larger than the observed one. This tendency is roughly explained by the induction effect of the Earth that is not considered in GAIA. Thus, GAIA considerably well reproduces the pure ionospheric current system that is not affected by the solid Earth. Plain Language Summary: We demonstrate that the Ground‐to‐topside model of Atmosphere and Ionosphere for Aeronomy reproduces the Sq magnetic field variations fairly well. This result gurantees other scientists to use Ground‐to‐topside model of Atmosphere and Ionosphere for Aeronomy for studying various ionospheric dynamo processes. Key Points: GAIA reproduces well Y variation in general and low‐latitude X variation; for Z, reproducibility exceeds to 0.5 at about half observatories Reproducibility is reduced due to inaccurate latitude of the Sq current vortex for X and due to the heterogeneous ground conductivity for Z The amplitude ratio of the calculated Sq variation to the observed one is consistent with the theoretical estimation for all three components