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tokens: 19:03 to 19:39 UT. We plot in panels (e) and (f) of Figure 11 the maps of Alfvénic Mach number (with and without accounting for magnetic mirroring) covering the interval from 19:03 to 19:43 UT. During this time interval, the magnetic connections from the shock are on open field lines connected to the AR and to polar coronal holes. Significant magnetic turbulence must prevail in the AR in order for the modeled location to agree with the observations. 5. Connecting the Shock Evolution with the Time History of the Relativistic Protons at Earth In this section, we investigate whether particles accelerated by shocks crossing field lines reaching Earth can explain the time history of relativistic protons observed in GLE72. Kurt et al. ( 2019 ) detail observations made by several neutron monitors. They show that the proton angular distribution was strongly anisotropic early in the event and only became isotropic at about 18:00 UT. The Fort Smith (FSMT) neutron monitor located in the Northwest Territories (60 north, 112 west) was relatively closely aligned with solar magnetic field lines at 16:00 UT. Therefore, it provides an excellent monitor of early particle acceleration at the Sun. We plot the pressure-corrected FSMT 1 and 5 minute count rates from 15:30 to 17:00 UT in Figure 12 . The rates rise in response to the event at about 16:08:30 UT. Figure 12. Comparison between the evolution of the and the time history of the GLE72 count rates from FSMT neutron monitor (see text for details). In determining the evolution of the shock wave parameters at regions well connected to Earth, we use the methods presented in Kouloumvakos et al. ( 2019 ) and also in our discussions in Sections 3 and 4 . The shock wave intersected magnetic field lines that were well connected to Earth at 15:57 UT, and it became supercritical around 15:59 UTl. 7 7 This assumes that the shock accelerating the particles was quasi-perpendicular requiring a critical Mach number of ∼2.7, which was reached at 15:59 UT. The mean M A and M fm parameters continued to increase, reaching a maxima near 18:00. The mini-neutron monitor DOMC (Usoskin et al. 2015 ) NM station situated at the South Pole recorded the most intense flux with a peak at 18:50 UT (see Mishev et al. 2018 ). The density compression ratio saturated within 15 minutes and reached an asymptotic value of 4. Using a similar model to the one used in Section 4.3 to predict the time profile of the γ -ray emission, we examine the shock origin of the particles that access field lines reaching Earth. We consider an function that includes only the term sh discussed in Section 4.3 , which approximates the effectiveness of shock acceleration. In order to directly compare estimated proton flux with the FSMT NM count rate, we need to shift to account for the time it took the protons to reach Earth. A common approach is to assume that the particles propagate along IP magnetic field lines following a Parker spiral whose shape is defined by