Time History of Events and Macroscale Interactions during Substorms (THEMIS) probes P3–P5 observations on 19 May 2010 between 12:10 and 12:14 UT. From top to bottom are shown: z component of curl of the ion velocity ω
z
and equatorial components of divergence of the ion velocity – ∂V
ix
/∂x (blue), ∂V
iy
/∂y (green) and the sum of the two (black). ω
z
, ∂V
ix
/∂x and ∂V
iy
/∂y were calculated for the area of the triangle with its apices at the locations of P3, P4, and P5 (coordinates are provided in the top of the right panel in Figure 3; the triangle is shown in Figure S3 of the Supporting Information S1). Ion pressure P
p
, magnetic field pressure P
B
, sum of the ion and magnetic field pressures, ion‐to‐magnetic pressure ratio (plasma β = P
p
/P
B
), vertical component of the electric field E
Z
at probes P3 (cyan), P4 (blue) and P5 (magenta). All shown parameters are derived from joint THEMIS electrostatic analyzer‐Solid State Telescope ion observations.