ACE in situ measurements at L1 and geomagnetic indices. (a) The number density (in cm⁻³) on a logarithmic scale; (b) the plasma speed (in red) and a straight line (indigo) that has been added to illustrate the very long, almost linear plasma-speed decrease between 2002 May 23 at 22:54 UTC and 2002 May 25 at 10:35 UTC; (c) the Alfvén speed; (d) the plasma temperature (in red) and half the expected plasma temperature (in blue) on a logarithmic scale; (e) the magnetic field strength on a logarithmic scale; (f), (g), and (h) the components of the magnetic field in GSE; (i) the plasma β; (j) the thermal (in red), magnetic (in blue), and total (in grey) pressures (in pPa); (k) the disturbance storm time (Dst) index (in red) and SYM-H indices (in blue); (l) the AE (in red), AU (in blue), and AL (in grey) auroral indices; (m) the Pearson product-moment correlation coefficient for the plasma speed and the plasma temperature for a moving time window of six hours. The background colours illustrate the different structures in the solar wind: the sheath of the first ICME is in light blue (on 2002 May 23 between10:15 UTC and 11:50 UTC); the magnetic ejecta of the first ICME is in yellow (on 2002 May 23 between 11:50 UTC and 15:10 UTC); the sheath of the second ICME is in light red (on 2002 May 23 between 15:10 UTC and 21:30 UTC); the magnetic ejecta of the second ICME is in light green (between the 2002 May 23 at 21:30 UTC and the 2002 May 25 at 18:00 UTC). The end of the second flux rope is represented by a vertical black line. The flux rope back itself is separated into two regions by a vertical blue line.