[P-EM15] Dynamics in magnetosphere and ionosphere

[PEM15-27] Transmission of the magnetospheric electric fields to the middle and low latitude ionosphere as observed by the Hokkaido SuperDARN radar and HF Doppler sounders

*菊池 崇^1,3、橋本 久美子²、海老原 祐輔³、西村 幸敏⁴、冨澤 一郎⁵、西谷 望¹、長妻 努⁶ (1.名古屋大学宇宙地球環境研究所、2.吉備国際大学、3.京都大学生存圏研究所、4.Center for Space Physics, Boston University、5.電気通信大学宇宙電磁環境研究センター、6.情報通信研究機構)

キーワード：中低緯度電離圏、磁気圏電場、電離圏電場、磁気圏電離圏地面伝送線モデル、準周期DP2変動

The quasi-periodic DP2 fluctuations have been observed by magnetometers at high latitudes and dayside equator [Nishida, 1968] and their occurrence is simultaneous within the temporal resolution of 25s [Kikuchi et al., 1996]. The equatorial DP2 fluctuations are composed of the eastward electrojet (EEJ) and westward counterelectrojet (CEJ), which are caused by the convection and overshielding electric fields, respectively [Kikuchi et al., 2010]. In the present paper, we show that the DP2 electric fields were detected by the Hokkaido SuperDARN radar and HF Doppler sounder at middle and low latitudes, respectively on both the day- and night-sides. We also show that the DP2 electric fields induced the EEJ/CEJ in the nighttime equatorial ionosphere, which are in opposite direction to those on the dayside. We further confirmed the evening anomaly with the electric fields being in the same direction as in the day. All the local time and latitude features of the DP2 electric fields are the same as those of the geomagnetic sudden commencements [Kikuchi et al., 2016]. We suggest that the electric field and currents with periods ranging from 1 min to hours are associated with the electric potentials transmitted on the magnetosphere-ionosphere-ground transmission line [Kikuchi, 2014] on both the day- and night-sides.

References

Kikuchi , T., Y. Ebihara, K. K. Hashimoto, R. Kataoka, T. Hori, S. Watari, and N. Nishitani (2010), Penetration of the convection and overshielding electric fields to the equatorial ionosphere during a quasiperiodic DP 2 geomagnetic fluctuation event, J. Geophys. Res., 115, A05209, doi:10.1029/2008JA013948.

Kikuchi, T. (2014), Transmission line model for the near-instantaneous transmission of the ionospheric electric field and currents to the equator, J. Geophys. Res. Space Physics, 119, doi:10.1002/2013JA019515.

Kikuchi, T., K. K. Hashimoto, I. Tomizawa, Y. Ebihara, Y. Nishimura, T. Araki, A. Shinbori, B. Veenadhari, T. Tanaka, and T. Nagatsuma (2016), Response of the incompressible ionosphere to the compression of the magnetosphere during the geomagnetic sudden commencements, J. Geophys. Res. Space Physics, 121, doi:10.1002/2015JA022166.