TY - JOUR
T1 - Evaluation of the Sq Magnetic Field Variation Calculated by GAIA
AU - Fujita, Shigeru
AU - Murata, Yuka
AU - Fujii, Ikuko
AU - Miyoshi, Yasunobu
AU - Shinagawa, Hiroyuki
AU - Jin, Hidekatsu
AU - Fujiwara, Hitoshi
N1 - Funding Information:
S. F. and I. F. acknowledge discus sions about 3-D electromagnetic inversion problems with T. Koyama and K. Baba of Earthquake Research Institute, University of Tokyo. This work was supported by JSPS KAKENHI grants JP15H05815 and JP15K05262. The geomagnetic 1-min values at magnetic observatories were obtained through INTERMAGNET at http://www.intermagnet.org/ index-eng.php. The ionospheric current data used for this study are available upon request at iono@ml.nict.go.jp.
Publisher Copyright:
©2018. American Geophysical Union. All Rights Reserved.
PY - 2018/4
Y1 - 2018/4
N2 - 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.
AB - 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.
UR - http://www.scopus.com/inward/record.url?scp=85045196390&partnerID=8YFLogxK
UR - http://www.scopus.com/inward/citedby.url?scp=85045196390&partnerID=8YFLogxK
U2 - 10.1002/2017SW001745
DO - 10.1002/2017SW001745
M3 - Article
AN - SCOPUS:85045196390
SN - 1542-7390
VL - 16
SP - 376
EP - 390
JO - Space Weather
JF - Space Weather
IS - 4
ER -