Electron temperature and de Hoffmann‐Teller potential change across the Earth's bow shock: New results from ISEE 1

We present a survey of the trends between the electron temperature increase Δ T e and the de Hoffmann‐Teller frame (HTF) electrostatic potential jump ΔΦ HT and their correlation with other parameters that characterize the shock transition using a new ISEE 1 database of 129 Earth bow shock crossings. A fundamental understanding of the HTF potential is central to distinguishing the reversible and irreversible changes to electron temperature across collisionless shocks. The HTF potential is estimated using three different techniques: (1) integrating the steady state, electron fluid momentum equation across the shock layer using high time resolution plasma and field data from ISEE 1, (2) using the steady state, electron fluid energy equation, and (3) using an electron polytrope approximation. We find that ΔΦ HT and Δ T e are strongly and positively correlated with |Δ( m p U n 2 /2)|, which is in good qualitative agreement with earlier experimental surveys [ Thomsen et al. , 1987b; Schwartz et al. , 1988] that used bow shock model normals and used the flow in the spacecraft frame. There is a strong linear organization of the Δ T e with ΔΦ HT , which suggests an average effective electron polytropic index of 〈γe〉 ≈ 2. In addition, Δ T e and ΔΦ HT are organized by β e , although our results may be biased by our limited sampling of shock conditions. Comparisons indicate that the differentials in the HTF potential δΦ HT are proportional to the differentials in the magnetic field intensity δB across the shock, with a proportionality constant κ that is a fixed constant for a given shock crossing.