4:15 PM - 4:30 PM
[PEM10-14] Statistical study of mid- and low-latitude electric field response corresponding to the CW structure that develops during substorms
Keywords:substorm, magnetosphere, ionosphere, mid-latitudes
The purpose of this study is to comprehensively understand the evolution of global 3D current system from polar to equatorial ionosphere during substorms.
There are two types of current systems in the polar ionosphere: the R1-current linked to the magnetospheric convection system, and the R2-current linked to the pressure gradient in the inner magnetosphere [Iijima and Potemra, 1976, 1978]. In addition to these currents, when a substorm onset is occurred by a strong plasma injection, a current wedge (CW) is generated by the plasma vorticities at the edge of the plasma flow. It has the same current polarities as the R1-current system.
Magnetic field variations generated by field-aligned currents (FAC) associated with CW development are significant in the nightside mid- and low-latitude, and these variations was modeled by McPherron et al. [1973]. We capture the spatio-temporal development of CW current systems during substorm by using MAGDAS and SuperMag magnetic field data, and by comparing them with the electric field data from the FM-CW installed at Kyushu University in Paratunka, Russia, we are analyzing the electromagnetic dynamic responses in the mid- and low-latitude regions.
We performed a comparative analysis of ionospheric electric and geomagnetic fields for 50 of the 1790 isolated substorms that occurred between September 21, 2006 and December 31, 2010, when the paratunka was on the night side (19:00-24:00, 0:00-05:00) in which the electric field changed significantly with substorm onset. The results show that the amplitude of the electric field variation is correlated with the westward auroral electrojets strength. Furthermore, the direction of the electric field reflects the electric field caused by the Hall polarization effect due to the ionospheric current induced by CW (simulated by Yoshikawa et al. [2013]), based on a detailed classification of the relative positions of the CW and observation points from mid-latitude geomagnetic data.
However, similar analyses of the other 1740 cases showed that these models alone could not explain the results, and even when the substorm conditions (intensity of the auroral electrojet and the local time at which the electric field variations were observed) were the same as in the above 50 cases, there were many events that showed no electric field variations associated with the onset. Therefore, we consider that the magnitude of the electric field variations is not only a function of the auroral electrojet and CW, but also the background magnetospheric and ionospheric conditions, and the influence of the solar wind. Therefore, in this presentation, we report the results of a comprehensive study of nightside electric field variations during substorms, based on a detailed classification of geomagnetic disturbances in the background of substorms by a combined analysis with the Kp index and IMF Bz of solar wind, in addition to the index of substorms (SML)
There are two types of current systems in the polar ionosphere: the R1-current linked to the magnetospheric convection system, and the R2-current linked to the pressure gradient in the inner magnetosphere [Iijima and Potemra, 1976, 1978]. In addition to these currents, when a substorm onset is occurred by a strong plasma injection, a current wedge (CW) is generated by the plasma vorticities at the edge of the plasma flow. It has the same current polarities as the R1-current system.
Magnetic field variations generated by field-aligned currents (FAC) associated with CW development are significant in the nightside mid- and low-latitude, and these variations was modeled by McPherron et al. [1973]. We capture the spatio-temporal development of CW current systems during substorm by using MAGDAS and SuperMag magnetic field data, and by comparing them with the electric field data from the FM-CW installed at Kyushu University in Paratunka, Russia, we are analyzing the electromagnetic dynamic responses in the mid- and low-latitude regions.
We performed a comparative analysis of ionospheric electric and geomagnetic fields for 50 of the 1790 isolated substorms that occurred between September 21, 2006 and December 31, 2010, when the paratunka was on the night side (19:00-24:00, 0:00-05:00) in which the electric field changed significantly with substorm onset. The results show that the amplitude of the electric field variation is correlated with the westward auroral electrojets strength. Furthermore, the direction of the electric field reflects the electric field caused by the Hall polarization effect due to the ionospheric current induced by CW (simulated by Yoshikawa et al. [2013]), based on a detailed classification of the relative positions of the CW and observation points from mid-latitude geomagnetic data.
However, similar analyses of the other 1740 cases showed that these models alone could not explain the results, and even when the substorm conditions (intensity of the auroral electrojet and the local time at which the electric field variations were observed) were the same as in the above 50 cases, there were many events that showed no electric field variations associated with the onset. Therefore, we consider that the magnitude of the electric field variations is not only a function of the auroral electrojet and CW, but also the background magnetospheric and ionospheric conditions, and the influence of the solar wind. Therefore, in this presentation, we report the results of a comprehensive study of nightside electric field variations during substorms, based on a detailed classification of geomagnetic disturbances in the background of substorms by a combined analysis with the Kp index and IMF Bz of solar wind, in addition to the index of substorms (SML)