Dipolarization Fronts in Cold-Dense and Hot-Tenuous Plasma Sheet Conditions: A Comparative Study

We present the first comparative observation of two dipolarization fronts (DFs) in cold-dense plasma sheet (CDPS) and hot-tenuous plasma sheet (HTPS) conditions. We find that: (a) the CDPS and HTPS are formed under distinct solar wind conditions. (b) The DF in HTPS has a higher B-z increase than the DF in CDPS; (c) DF in CDPS can transfer energy from magnetic field to particles more efficiently than the DF in HTPS; (d) the > 2 keV (< 2 keV) electron phase space density of flux pileup region (FPR) in HTPS is higher (lower) than that of FPR in CDPS; (e) the electron cyclotron harmonic waves are excited at DF in HTPS instead of the DF in CDPS. (f) The responses in the ionospheric currents are weak for both DFs in CDPS and HTPS. These results reveal the differences in properties and physical processes between the DFs in CDPS and HTPS. Our findings can significantly improve the understanding of physical mechanisms underlying the formation and evolution processes of DFs.Plain Language Summary Taking advantage of the high-resolution measurements from Magnetospheric Multiscale Mission, we present the first comparative observation of two dipolarization fronts (DFs) in cold-dense plasma sheet (CDPS) and hot-tenuous plasma sheet (HTPS) conditions. From the comparison, we find the CDPS and HTPS are formed under distinct solar wind conditions, the distinct properties of electromagnetic structure, energy conversion, thermotics, and wave activities at the two rare DFs. These results reveal the properties and physical processes of the DFs in CDPS and HTPS, which help us understand the physical mechanisms underlying the formations and evolution processes of DFs.