  The GRAPES-3 muon telescope in Ooty, India had claimed detection of a 2 hour
(h) high-energy ($\sim$20 GeV) burst of galactic cosmic-rays (GCRs) through a
$>$50$\sigma$ surge in GeV muons, was caused by reconnection of the
interplanetary magnetic field (IMF) in the magnetosphere that led to transient
weakening of Earth's magnetic shield. This burst had occurred during a G4-class
geomagnetic storm (storm) with a delay of $\frac{1}{2}$h relative to the
coronal mass ejection (CME) of 22 June 2015 (Mohanty et al., 2016). However,
recently a group interpreted the occurrence of the same burst in a subset of 31
neutron monitors (NMs) to have been the result of an anisotropy in
interplanetary space (Evenson et al., 2017) in contrast to the claim in
(Mohanty et al., 2016). A new analysis of the GRAPES-3 data with a fine
10.6$^{\circ}$ angular segmentation shows the speculation of interplanetary
anisotropy to be incorrect, and offers a possible explanation of the NM
observations. The observed 28 minutes (min) delay of the burst relative to the
CME can be explained by the movement of the reconnection front from the bow
shock to the surface of Earth at an average speed of 35 km/s, much lower than
the CME speed of 700 km/s. This measurement may provide a more accurate
estimate of the start of the storm.
