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tokens: with the lowest velocities ( V 290 km s −1 ) are clearly divided into two groups. One group is an undisturbed low-velocity SW, the second group includes points near the heliospheric plasma sheet and inside weak and very slow ICMEs. Using the regression model with different slopes in regions of low and high velocity (Table 2 ), we calculated hourly values of the expected temperature T exp and the temperature index K T = T / T exp for all hourly data from 1965 July–2019 November. The distribution of the temperature index is presented in Fig. 2 . The distribution is unimodal, peaked, right-skewed, and has a long tail in the region of large values. In Fig. 2 the tail is cut off, because the maximum value of the temperature index is too large ( K T max = 39.5) and the overwhelming majority of the observations have temperature index K T 5. A large number of high K T values is understandable: as a rule, the observed temperature is higher than expected where different-speed SW streams interact (e.g. Elliot et al. 2005 ). There are many such areas: they are in front of almost all HSS from CHs and in front of all ICMEs with sufficiently high speed. In other words, the events in a distribution tail in a region of large values of temperature index may be associated with CIRs or sheaths before high-speed ICME. Figure 2. Distribution of the temperature index K T (from 1965 July–2019 November). Analysis of the minimal (for each FD) values of the temperature index K T min for a large number of events (766 FDs) allowed us to establish a correspondence between K T min and the type of solar source modulating cosmic rays. Fig. 3 presents the distribution of K T min for groups of FDs associated with different types of source (1, ejection from an active region accompanied by a solar flare; 2, CME associated with a solar filament eruption from a region beyond a sunspots group; 3, mixed events with contributions of HSS from CHs and CMEs; 4, clear influence of HSS from CH without other influences), and for the full group of events (group 5). It is clearly visible that the distribution of K T min values for group 4 (CH-associated events) differs significantly from the distributions for groups 1 and 2 (CME-associated events). The K T min means (0.36 ± 0.02 in group 1 and 0.38 ± 0.02 in group 2) and medians (0.28 and 0.31 respectively) are approximately equal for the two groups associated with CMEs. At the same time, these statistics differ significantly from the mean (0.59 ± 0.01) and median (0.58) in the CH-associated group. The distribution of the mixed events group (mean 0.50 ± 0.02, median 0.47) is between those of the CME and CH groups and is close to the distribution of the full group of events (group 5: mean 0.48 ± 0.01, median 0.49). The results obtained therefore reveal that we can use K T min as a tool to help in the identification of FDs with solar sources. Figure 3. Box plots of the temperature index minimal values K T min (from 2000 January–2016 November) in