IEC 61000-2-9:2025

IEC 61000-2-9 ®
Edition 2.0 2025-05
INTERNATIONAL
STANDARD
Electromagnetic compatibility (EMC) –
Part 2-9: Environment – Description of HEMP environment – Radiated
disturbance
ICS 33.100.01  ISBN 978-2-8327-0393-9

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– 2 – IEC 61000-2-9:2025 © IEC 2025
CONTENTS
FOREWORD . 4
INTRODUCTION . 6
1 Scope . 7
2 Normative references . 7
3 Terms and definitions . 7
4 Types of HEMP waveforms . 12
5 Description of HEMP environment, radiated parameters . 12
5.1 High-altitude bursts . 12
5.2 Spatial extent of E HEMP on the earth's surface. 14
5.3 HEMP time dependence . 14
5.3.1 General. 14
5.3.2 Early-time HEMP waveform. 14
5.3.3 Intermediate-time HEMP waveform . 19
5.3.4 Late-time HEMP waveform . 20
5.3.5 The complete standard HEMP electric field time waveform . 21
5.4 Early-time HEMP magnetic field component . 22
5.5 HEMP amplitude and energy fluence spectrum . 23
5.6 Comparison of the early-, intermediate- and late-time HEMP . 25
5.7 Reflection and transmission of the early-time HEMP . 25
Annex A (informative) Background of HEMP environments. 30
A.1 Development of a standard early-time (E ) HEMP waveform . 30
A.2 Alternate analytic standard early-time HEMP waveform . 32
A.2.1 Overview and comparisons . 32
A.2.2 Formulae for the difference of exponentials (DEXP) . 34
A.2.3 Formulae for the quotient of exponentials (QEXP) . 35
A.3 Far field region for the early-time HEMP . 36
A.4 Additional information for the late-time HEMP . 37
Bibliography . 41

Figure 1 – Geometry for the definition of polarization and of the angles of elevation Ψ
and azimuth ϕ . 8
Figure 2 – Geometry for the definition of the direction of propagation . 9
Figure 3 – Geomagnetic dip angle . 10
Figure 4 – Schematic representation of the early-time HEMP from an example of a
high-altitude burst. 13
Figure 5 – HEMP tangent radius as a function of height of burst (HOB) . 15
Figure 6 – Typical variations in peak electric fields on the earth's surface for burst
altitudes between 30 km and 500 km and for ground zero between 30° and 60°
northern latitude . 16
Figure 7 – Different waveforms for three typical cases indicated in Figure 6 (point A,
point B, point C) and the composite curve fit . 16
Figure 8 – Plots of the early-time HEMP standard waveform (Formula (1)) and a world
map indicating the variation of the dip angle of the geomagnetic field used in
Formula (2) . 19
Figure 9 – Standard late-time HEMP waveform . 21
Figure 10 – Complete standard HEMP time waveform . 22

Figure 11 – Amplitude spectrum of each HEMP component . 23
Figure 12 – Fraction of energy fluence from f = 10 Hz to f . 24
Figure 13 – Representation of incident, reflected and refracted waves . 25
Figure 14 – Calculated total horizontal electric field as a sum of the incident
plus reflected fields for a HEMP (early-time part only) . 27
Figure 15 – Calculated total horizontal electric field as a sum of the incident plus
reflected fields for a HEMP (early-time part only) for different angles of elevation . 28
Figure 16 – Calculated transmitted horizontal electric fields for a HEMP (early-time
part only) . 29
Figure A.1 – Three sample early-time HEMP time waveforms and the standard pulse
(with a peak value of 50 kV/m) . 30
Figure A.2 – The Fourier transform amplitudes of the time waveforms in Figure A.1 . 31
Figure A.3 – Comparison of the DEXP and the QEXP time waveforms and their time

derivatives . 33
Figure A.4 – Frequency amplitudes for the DEXP and QEXP E HEMP waveforms . 34
Figure A.5 – Analytic B-field waveform estimated to be the worst-case late-time HEMP
waveform . 37
Figure A.6 – Analytic E-field waveform estimated to be the worst-case late-time HEMP
waveform, σ = 0,1 S/m . 38
Figure A.7 – Analytic E-field waveform estimated to be the worst-case late-time HEMP
waveform, σ = 10 mS/m . 39
Figure A.8 – Analytic E-field waveform estimated to be the worst-case late-time HEMP
waveform, σ = 1,0 mS/m . 39
Figure A.9 – Analytic E-field waveform estimated to be the worst-case late-time HEMP
waveform, σ = 0,1 mS/m . 40

Table A.1 – E HEMP time waveform parameters . 32
– 4 – IEC 61000-2-9:2025 © IEC 2025
INTERNATIONAL ELECTROTECHNICAL COMMISSION
____________
ELECTROMAGNETIC COMPATIBILITY (EMC) –

Part 2-9: Environment –
Description of HEMP environment – Radiated disturbance

FOREWORD
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IEC 61000-2-9 has been prepared by subcommittee 77C: High power transient phenomena, of
IEC technical committee 77: Electromagnetic compatibility. It is an International Standard.
It forms Part 2-9 of IEC 61000. It has the status of a horizontal basic EMC publication in
accordance with IEC Guide 107.
This second edition cancels and replaces the first edition published in 1996. This edition
constitutes a technical revision.
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