the CPS at 197 MHz, and CPS oscillates around zero. These results indicate that the CPS is dominated by errors due to foregrounds, which should be proportional to $(C_l^{\rm FG})^{1/2}$. Same as left panels, blue circles indicate the foreground contamination on the CPS at $l=500$ in the bottom right panel of Fig. \[fig:CPSLST\]. ]{}

[ ]{}

![image](./Fig_paper/fluxvslst.eps){width="7cm"} ![image](./Fig_paper/fluxvslst_smallscale.eps){width="7cm"}

![image](./Fig_paper/Fig11_X_100.eps){width="7cm"} ![image](./Fig_paper/Fig11_X_500.eps){width="7cm"} ![image](./Fig_paper/Fig11_X_100_lini.eps){width="7cm"} ![image](./Fig_paper/Fig11_X_500_lini.eps){width="7cm"}

Ionosphere Dependence
---------------------

[ The Earth’s ionosphere refracts radio waves and produces phase errors and spatial offsets of radio point sources in interferometer measurements. Although the RTS calibrates the phase error, the uncalibrated error can produce residuals of point sources after the point source subtraction. Here, we show the effect of ionosphere activity on the APS and CPS. ]{}

[ In [@Cris2017], they have discussed particular types of ionosphere activity by defining the metric of ionosphere quality, $m$, based on the total offsets of point sources and dominant eigenvalue determined by a principal component analysis to the source offsets. In general, the quiet ionosphere has $m<4$ and the active has $m>10$. [ Since, for example, the calibration error due to the ionosphere can generate the error of the point sources subtraction, then we might find a correlation of 