A plasma bulk motion in the midnight magnetosphere during auroral breakup inferred from all-sky image and magnetic field observations at geosynchronous altitudes

First 10min intervals of Pi2 onset at geosynchronous altitudes during the expansion of energetic ion regions in the nighttime sector

“…Those events with eastward deflections (clockwise rotation, azimuth angle decreased) at T¼ 0 are shown to the left and those with westward deflections (counterclockwise rotation, azimuth angle increase) at T¼0 are to the right. geosynchronous altitudes may be correlated with the propagation direction because the polarization switched at two geosynchronous satellites (Goes5 and Goes6) that were facing each other with an aurora expansion between them (Saka et al, 2007). In the western longitudes of aurora expansion, the polarization was CW, while it was CCW in the eastern longitudes.…”

Ionospheric loop currents and associated ULF oscillations at geosynchronous altitudes during preonset intervals of substorm aurora

“…The ULF oscillations observed by GOES 6 at off‐equatorial latitudes, 8.8°N in dipole latitudes, can be related to plasma displacement at the equatorial plane by using the polar coordinates of the field line vectors in ( B , θ , ϕ ), where B is the field magnitude, θ is the inclination angle in degrees measured positive northward from the V‐D plane, and ϕ represents the azimuth angle of field vectors in degrees in the V‐D plane measured positive counterclockwise from the V axis [ Saka et al , , ]. The azimuthal angle ϕ is 180° when the field line vectors point earthward.…”

“…The interval of the equatorward drift of the aurora from 04:03 UT to 04:51 UT is denoted as the preonset interval marked by the horizontal arrow in Figure 1. ULF oscillations were observed from 04:15 UT to 04:35 UT in all of the three components, H, V, and D. In the keogram, there appeared a The ULF oscillations observed by GOES 6 at off-equatorial latitudes, 8.8°N in dipole latitudes, can be related to plasma displacement at the equatorial plane by using the polar coordinates of the field line vectors in (B, θ, ϕ), where B is the field magnitude, θ is the inclination angle in degrees measured positive northward from the V-D plane, and ϕ represents the azimuth angle of field vectors in degrees in the V-D plane measured positive counterclockwise from the V axis [Saka et al, 2007[Saka et al, , 2010. The azimuthal angle ϕ is 180°w hen the field line vectors point earthward.…”

Excitation of the third harmonic mode in meridian planes for Pi2 in the auroral zone

“…In the polar coordinates, the azimuth angle is 180 when the field line vector points toward Earth. The field line motions associated with the circular rotations (not the twist) of the plasma slabs at the equatorial plane may cause wave polarizations, δB ⊥ , in the satellite magnetometer data off the equatorial plane [ Saka et al , 2007]. δB ⊥ is written as ( B 0 δθ , B 0 δϕ ), where B 0 represents the mean magnitudes.…”

“…This hodogram suggests that the field line vector rotated clockwise (CW) around the mean fields as viewed in the opposite direction of the field lines. The plasma slab in the equatorial plane is thought to have slipped in the same sense, i.e., clockwise as viewed from the north [ Saka et al , 2007]. At the satellite footprint (GWR), CW polarization was observed in the H‐D plane (Figure 10, bottom).…”