and crests in different locations of the same TEC perturbation.

Case $\#$4
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![image](Figure5.png){width="80.00000%"}

In Figure \[Figure5\] we show a pair of SCs which have been detected by two spatially spaced instruments. This represents a rare situation. In contrast to the previous case, here the SCs are almost replicas of each other. Panels (a) and (b) of the figure represent the CALLISTO DARO and the CALLISTO ESSEN solar dynamic spectra, respectively. While the SC in the CALLISTO ESSEN spectrogram (SC-E) is enhanced, the SC in the CALLISTO DARO spectrogram (SC-D) is partly suppressed in intensity. The upper part, front and back envelopes of the SC-D stand out distinctly though. Both SCs belong to the inverted V-like type. Moreover, they coincide in appearance time as well as frequency range.

We selected the instant at 08:05 UT near the SCs’ symmetry lines. This moment is indicated by purple and grey lines in panels (a) and (b), respectively. The IPPs at 08:05 UT for the CALLISTO DARO (purple plus) and the CALLISTO ESSEN (grey cross) antennas were computed and plotted on the dTEC map in panel (c). The IPPs locate in the valley bordering by the crests C1 and C2 (red arrows). The 