TY - JOUR
T1 - Seasonal variation of inter-hemispheric field-aligned currents deduced from time-series analysis of the equatorial geomagnetic field data during solar cycle 23–24
AU - Ranasinghe, Manjula
AU - Fujimoto, Akiko
AU - Yoshikawa, Akimasa
AU - Jayaratne, Chandana
N1 - Funding Information:
This work is financially supported by National Research Council (NRC) of Sri Lanka (16–098). The MAGDAS observation is financially supported by Japan Society for the Promotion of Science (JSPS) as Grant-in-Aid for Overseas Scientific Survey (15253005, 18253005). AF was supported by the JSPS KAKENHI Grant (17J40136, 19K03956). AY was supported by JSPS KAKENHI Grant (19K03956, 15H05815, JP20H01961).
Publisher Copyright:
© 2021, The Author(s).
PY - 2021/12
Y1 - 2021/12
N2 - The east–west component of magnetic field variation (∆D-component) at Davao station (Philippines, geomagnetic latitude: – 2.22˚N) are used to investigate the characteristics of the long-term Inter-Hemispheric Field-Aligned Currents (IHFACs) based on the time-series analysis from August 1998 to July 2020. Recent in situ satellite and ground-based observations have reported that dusk-side current polarity of IHFAC is often opposite to that of the noon IHFAC, being inconsistent with Fukushima's IHFACs model. We investigated the consistency of the dusk-side IHFAC polarity derived from the observations with the polarity expected from Fukushima’s IHFACs model and examined the solar cycle dependence of IHFACs. It was confirmed that the dusk-side IHFACs during June and December solstices flow in the same direction of the noontime IHFACs, which was consistent with the IHFAC polarities suggested by the Fukushima model. The dusk-side IHFACs around March and September–November months disagreed with the Fukushima model. The ∆D variations clearly showed seasonal asymmetry in the dawn and noon sectors, whereas the ∆D variations in the dusk sector demonstrated seasonal symmetry. Solar cycle dependence of IHFACs was exhibited in the dusk sector. For the dawn and noon sectors, the yearly peak-to-peak ∆D amplitude in the later solar cycle SC24 decreased by about 35% in comparison with the earlier solar cycle SC23. In contrast, the dusk-side yearly peak-to-peak ∆D amplitude increased by about 200%. The dusk-side IHFAC yearly amplitude tended to be in inverse proportion to solar activity. [Figure not available: see fulltext.]
AB - The east–west component of magnetic field variation (∆D-component) at Davao station (Philippines, geomagnetic latitude: – 2.22˚N) are used to investigate the characteristics of the long-term Inter-Hemispheric Field-Aligned Currents (IHFACs) based on the time-series analysis from August 1998 to July 2020. Recent in situ satellite and ground-based observations have reported that dusk-side current polarity of IHFAC is often opposite to that of the noon IHFAC, being inconsistent with Fukushima's IHFACs model. We investigated the consistency of the dusk-side IHFAC polarity derived from the observations with the polarity expected from Fukushima’s IHFACs model and examined the solar cycle dependence of IHFACs. It was confirmed that the dusk-side IHFACs during June and December solstices flow in the same direction of the noontime IHFACs, which was consistent with the IHFAC polarities suggested by the Fukushima model. The dusk-side IHFACs around March and September–November months disagreed with the Fukushima model. The ∆D variations clearly showed seasonal asymmetry in the dawn and noon sectors, whereas the ∆D variations in the dusk sector demonstrated seasonal symmetry. Solar cycle dependence of IHFACs was exhibited in the dusk sector. For the dawn and noon sectors, the yearly peak-to-peak ∆D amplitude in the later solar cycle SC24 decreased by about 35% in comparison with the earlier solar cycle SC23. In contrast, the dusk-side yearly peak-to-peak ∆D amplitude increased by about 200%. The dusk-side IHFAC yearly amplitude tended to be in inverse proportion to solar activity. [Figure not available: see fulltext.]
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U2 - 10.1186/s40623-021-01481-6
DO - 10.1186/s40623-021-01481-6
M3 - Letter
AN - SCOPUS:85110687505
VL - 73
JO - Earth, Planets and Space
JF - Earth, Planets and Space
SN - 1343-8832
IS - 1
M1 - 146
ER -