MESSENGER observations of an active reconnection site in Mercury’s magnetotail. Panels (a)–(c) show an overview of the current sheet crossing. Panels (d)–(i) show a subset of the data near the diffusion region. (a)–(b) The magnetic field magnitude and its three components in the LMN coordinates. (c) Spectrogram of the ion differential energy flux (cm⁻² Sr⁻² s⁻¹ eV⁻¹) from the FIPS instrument. (d) The magnetic field magnitude. (e)–(g) L, M, and N components of the magnetic field. (h) Count rate of energetic electrons detected from the NS instrument with 1 s resolution in its burst mode. The labeled lobe region was identified by mostly the lack of flux detected by the FIPS instruments and the plasma sheet region was identified by hot plasma with high flux detected by FIPS instruments. Note that the plasma asymmetry across the current sheet represents temporal evolution of magnetotail structure due to a very short timescale of global flux circulation. The ion diffusion region was identified by the quadrupole Hall field, negative B_N, and energetic electrons bursts. The diffusion region crossing is divided into five short subintervals, T1–T5, according to the observed features of B_N.