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tokens: and B1 shock regions along the outflow of L1157 are marked here with circles (B0), triangles (B1), and squares (B2). The dashed circles represent the HPBW of the IRAM 30 m spectra at 86 GHz (29′′), 210 GHz (12′′), and 350 GHz(7.5′′). The green contours in the channel maps show the 10, 60, and 120 σ levels of the integrated intensity map of 28 SiO, shown in Fig. 1 . 4 LVG analysis In this section we analyse the single-dish spectra of the SiO and its isotopologues 29 SiO and 30 SiO from the 2−1 up to the 8−7 transition ( E up from 6 to 163 K), shown in Fig. 2 . The 12–11 spectrum was excluded from the analysis because it is too noisy: we note, however, that the fluxes reported in Table 1 are consistent with the solutions provided below. The line properties are summarised in Table 1 . This table also reports the integrated intensity in three velocity ranges: EHV: –23 to –13 km s −1 , HV: –13 to –3 km s −1 , and LV: –3 to +5 km s −1 . In order to derive the average physical properties of the gas that emits SiO, we carried out a non-LTE analysis using the large velocity gradient (LVG) code described in Ceccarelli et al. (2003) . We used the collisional coefficients of SiO with H 2 computed between 10 and 300 K for the first 20 levels by Dayou Balança (2006) that are provided by the BASECOL database ( Dubernet et al. 2013 ). We ran a large grid of models (≥7000) covering a SiO column density N SiO from 1.5 × 10 13 to 8 × 10 15 cm −2 , a H 2 density n H2 from 1 × 10 3 to 2 × 10 7 cm −3 , and a temperature T from 30 to 300 K. We then determined the solution by simultaneously fitting the 28 SiO, 29 SiO, and 30 SiO lines and left as free parameters N SiO , n H2 , and T , while the emitting sizes and line widths were those measured. We assumed 28 Si/ 29 Si = 19.7 and 28 Si/ 30 Si = 29.8, as obtained by Anders Grevesse (1989) and confirmed by our SOLIS observations for L1157-B1 (see Sect. 3.3 ), and we added the 20% calibration uncertainty in the observed intensity error bars. We sampled the parameter space unevenly (with steps of 10 K until 100 and 20 K for higher temperatures, steps of a factor of 2 for densities lower than 6 × 10 6 cm −3 and 1.3 at higher ones, steps of a factor of 1.5 in column densities until 1 × 10 14 cm −2 and 1.1–1.2 at higher ones to ensure better cover close to the minimum χ 2 . The beam dilution was taken into account, assuming that the emitting gas has a circular Gaussian shape and using the standard equation for beam dilution. We carried out the non-LTE analysis for the HV and EHV components. The results are described in the two following subsections and are summarised in Table 2 . Table 2 Result of the non-LTE LVG analysis. Notes. The HV and EHV emissions are composed of two physical components each: the first is associated with the B1a clump, and the second is more extended (see text). ( a ) SiO abundance with respect to molecularhydrogen. The H 2 column density used to calculate the SiO abundance is derived from the CO