Left column: data for calm solar wind intervals only, in red for state 1 and in blue for state 2. Right column: rest of the data set, in magenta for state 1 and in cyan for state 2. Top panels: electron β_e scaled to 35.6 R_⊙ (see Section 2.2), against proton speed in km s⁻¹. Middle panels: electron density (cm⁻³) scaled to 35.6 R_⊙, against proton speed in km s⁻¹. Error bars provided by the QTN method are plotted as thin black lines behind each point and are used to compute the error on β_e. Bottom panels: magnetic field intensity (nT) scaled to 35.6 R_⊙, against proton speed in km s⁻¹.