## 2 Data and Methods
### Magnetopause and Plasmapause Position Models  
The magnetopause position was obtained by means of the [PERSON] [39; 40] T01 magnetospheric field model. T01 is a semi-empirical model in which the total magnetospheric field of external origin comes from the sum of the Chapman-Ferraro current and contributions from cross-tail, ring, and field-aligned currents. All these contributions are calculated taking into account the solar wind (SW) dynamic pressure, the interplanetary magnetic field (IMF) configuration, and the Dst index. For the present analysis, we used the SW and IMF observations stored in the OMNI CDAWeb repository.  
The plasmapause location was assessed using the Liu and Liu [41] model, which is based on the experimental THEMIS-D satellite plasmapause crossing database. The model is based on the following equation:  
\[\phi=2\pi(MLT/24),\]  
\[\begin{array}{llll}\vspace{0.2 cm}\vspace{0.2 cm}\vspace{0.2 cm}\vspace{0.2 cm} \vspace{0.2 cm}\vspace{0.  
we were able to determine the ICME boundaries [43] using the IMF behavior (Panel a) in conjunction with the SW temperature (Panel c) and the SW dynamic pressure (Panel d). Indeed, upon the ICME's arrival, the SW temperature decreased from \(\sim\)\(9\times 10^{4}\) K to \(\sim\)\(1.5\times 10^{4}\) K, while the IMF increased to 18 nT, lasting for approximately 12 h. At the same time, the IMF underwent a smooth rotation, leading to a prolonged (\(\sim\)22 h) southward orientation (Panel b) at \(\approx\)14:30 UT on 25 August. Finally, the solar wind dynamic pressure fluctuated between \(\sim\)4 nPa and \(\sim\)10 nPa. A CIR followed on 26 August: the SW temperature increased from \(\sim\)\(\times 10^{4}\) K to nearly \(30\times 10^{4}\) K around 12:20 UT, with the pressure increasing from \(\sim\)2 nPa to \(\sim\)8 nPa, as the solar wind stream was crossing a negative polarity high-speed stream (HSS) [42].  
To evaluate the consequences of the ICME impact on the Earth's environment, we used the Sym-H index (which mirrors the dynamics of the symmetric part of the ring current [44]) and the AE index (which indirectly measures the energy deposition rate in  
Figure 3: Solar wind parameters observed by the ACE spacecraft at L1: (**a**) IMF intensity; (**b**) IMF \(B_{z}\) component; (**c**) proton temperature; (**d**) dynamic pressure of the solar wind; (**e**) Sym-H index; (**f**) AE (black), AL (red), and AU (blue) indices. The SW parameters are expressed in the Geocentric Solar Magnetospheric (GSM) coordinate system.  
the polar ionosphere [45]). On 26 August, Sym-H (Figure 3e) showed a rapid decrease, reaching its minimum value (\(\sim-190\) nT) at 07:57 UT. This structure mimics the behavior of the \(B_{z}\) component of the IMF, which shows a long-lasting (\(\sim\)10 h) negative value starting at 16:52 UT of 25 August. This trend is clearly related to the southward IMF carried by the magnetic cloud [43]. As a consequence of this long interval of negative \(B_{z}\), the SW plasma could flow inside the Earth's magnetosphere, possibly due to the occurrence of magnetic reconnection at the magnetopause between the geomagnetic field and the IMF [42].  
The large bursts in the AE index (black line in Figure 3f) can be related to a sequence of fast relaxation events, possibly stemming from an activity in the near-Earth magnetotail regions in the form of a sequence of loading-unloading releases of energy [46; 47]. Such processes give rise to a great amount of particle precipitation in the high-latitude region as confirmed by the behavior of the AL index (red line), which is excellently correlated with the negative turn of \(B_{z}\). AL (and hence AE) peaks are directly related to the north-south flip of \(B_{z}\) between 11:00 UT and 21:00 UT on 26 August, induced by the arrival of the CIR.