Are there ballooning-interchange heads in the midtail?

Abstract Magnetospheric multiscale (MMS) observed a series of isolated dipolarization fronts embedded in fast bursty bulk flows (BBFs/DFs) near 18 Earth’s radii ( $$\hbox {R}_E$$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:msub> <mml:mtext>R</mml:mtext> <mml:mi>E</mml:mi> </mml:msub> </mml:math> ) during a weak steady convection event. A number of distinctive signatures in the MMS data manifest kinetic ballooning-interchange instability (BICI) activity in the midtail whose signatures were recently identified in near-Earth THEMIS observations. For the first time we clearly identify strong electromagnetic waves near proton-cyclotron frequency also in the high-resolution plasma data. We confirm the predicted azimuthal wave propagation from four-point observations, and compare with the plasma flows’ and DFs’ motion. We use an adapted magnetospheric model to identify the ionospheric and ground footprints of the magnetic field lines. Inspecting energetic particles from conjugate low-altitude spacecraft azimuthal passage we find for the first time the azimuthal structuring of energetic proton fluxes suggesting the multiple sheets of field-aligned current. Auroral observations indicate the presence of a structured poleward azimuthal auroral arc and injection prints. We compare MMS midtail observations with previous near-Earth observations and discuss peculiarities of possible BICI generation during steady convection events. We find that the midtail BICI activity could be associated with greater temporal and spatial scales as compared to those of the near-Earth BICI activity. Graphical Abstract