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Often E1 HEMP is discussed in terms of the peak incident E field, as if no other characteristic matters. And most smile diagrams do plot this quantity. However, other quantities could also be of interest. In the following diagrams we show “smile” diagrams plotting different field quantities, all for the same E1 HEMP conditions (a 75 km HOB over the central U.S.). The figures are listed in Table 2-5 (the last three results listed in the table will be discussed in the next subsection). In general, the contour levels used are as fractions of the maximum incident field (which occurs at the white “+” inside the red contour in Figure 2-17).

Table 2-5. List of the sample “smile” diagrams. All cases are for the same burst scenario. Sample Smile Diagrams

Smile Display function Figure 2-17 Peak of incident E field

Figure 2-18 Peak of horizontal component of incident E field

Figure 2-19 Peak of north/south horizontal component of incident E field Figure 2-20 Peak of east/west horizontal component of incident E field

Figure 2-21 Field direction of peak of horizontal component of incident E field Figure 2-22 Peak of vertical component of incident E field

Figure 2-23 Peak of horizontal component of total E field (including reflection) Figure 2-24 Peak of vertical component of total E field (including reflection) Figure 2-25 Total energy density in incident E1 HEMP

Figure 2-26 Total energy denisty in 10 to 100 MHz band for incident E1 HEMP Figure 2-30 Peak current on north/south overhead line

Figure 2-31 Peak current on east/west overhead line Figure 2-32 Peak current on vertical wire

Parameters:

Burst: 40oN, 95oW, 75 km.

Reflected field (Figures 2-23 and 2-24): 10-2 S/m ground, observer 3 meters up. Coupling (Figures 2-27 – 2-29): 10-3 S/m ground, wire 0.2 centimeters radius.

Horizontal: wire 100 meters long, 5 meters above ground. Vertical: wire 5 meters long, base on ground.

These samples use the same case as shown in Figure 2-3, and so incident peaks in Figure 2-17 shows the same result. Figure 2-18 shows the peak of the horizontal part of the incident E1 HEMP – it is almost the same as for the peak of the total signal shown in the previous figure. In the next two figures this is separated into the peak for the north/south component (Figure 2-19) and the east/west component (Figure 2-20). Figure 2-21 repeats Figure 2-18 (peak horizontal) but also has arrows to show the direction of the horizontal field. We see that the E field looks to be azimuthal – pointing clockwise around the center. However, looking closely near the center, we see that it actually swirls around the null point, slightly above the center (ground zero, marked by a “+”). Figure 2-22 shows the peak of the incident vertical E field. This component tends to be smaller than the horizontal (and total) field, and so here we have used a different contour set than the previous plots. Note that most of the results seem to have east-west symmetry, but the vertical peak does not – this will be discussed later.

The previous results were all for the incident field. In the next two figures we have peaks for the total field, which includes reflection off the ground. We assume 10-2 S/m ground conductivity (in the range of soil conductivities, this would be considered toward the high end), and an observer point 3 meters off the ground. Figure 2-23 shows the horizontal peaks, and Figure 2-24 the vertical. The horizontal results show a suppression of the signal, especially as we go out toward the tangent (this gets worse as the observer point gets closer to the ground), while the vertical signal shows a slight enhancement.

For the next two figures we go to the frequency domain, for the incident E1 HEMP signal. Figure 2-25 shows the total energy density in the signal, while Figure 2-26 shows the energy density in the band of 10 to 100 MHz (toward the high frequency end). These are plotted as a fraction of the total energy density at the maximum E1 HEMP point (the max point, to the south of GZ). Note the contour set for the high frequency band had some low level contours added – this is to show how drastically the high frequencies fall off as we go to the tangent.

Figure 2-17. Sample E1 HEMP peak contours. This plots the peak value of the incident E field total waveform. The burst height is 75 km. The contours are as percentages of the absolute highest peak, which occurs at the point marked by the white cross hairs, south of the burst position (GZ, marked by the black cross hairs).

Figure 2-18. Sample E horizontal component contours. For the sample case of Figure 2-17, this gives a contour plot of the peak of the horizontal component of the incident E1 HEMP E field. The contour edges are at the same field level values as for Figure 2-17 (both use the same percents of the maximum peak magnitude of the incident field).

Figure 2-19. Sample E north/south horizontal component contours. This and the next figure break down the horizontal term (Figure 2-18) into two components. These contours show the North/South component of the peak E1 HEMP incident E field. (Again this uses the same E field values for edges of the contour set.)

Figure 2-20. Sample E east/west horizontal component contours. This shows the other horizontal component for the E1 HEMP sample – the East/West part of the peak E field (using the same contour set values as the previous plots).

Figure 2-21. Horizontal E field direction for E1 HEMP sample. Arrows show the E field directions for the horizontal E field peak for the sample case. The contours are for the peak horizontal E field – the same as in Figure 2-18. (Here we have zoomed in a little more than for the other figures.)

Figure 2-22. Sample E vertical component contours. This gives the peaks of the vertical component for the E1 HEMP sample. Here a different contour levels set is used, since the vertical values tend to be somewhat smaller than the horizontal values (but the contours still use percent of the maximum total incident E field value).

Figure 2-23. Peak horizontal E1 HEMP contours, including ground reflection. We have added a 10% contour level for this plot. (Parameters: 10-2 _{S/m ground conductivity, observer 3 meters off ground.)}

Figure 2-24. Peak vertical E1 HEMP contours, including ground reflection. (Parameters: 10-2 _{S/m ground}

Figure 2-25. Sample E1 HEMP total energy contours. This plot shows the total electromagnetic energy in the incident E1 HEMP. The contour set uses percents of the value at the peak point.

Figure 2-26. Contours of energy in the 10 to 100 MHz band. This is like the previous plot, but for only the energy in 10-100 MHz. The contour values are as percentages of the value of total energy at the maximum E1 HEMP energy point (the same normalization used for Figure 2-25).