IEC TR 62396-6:2017

IEC TR 62396-6 ®
Edition 1.0 2017-07
TECHNICAL
REPORT
colour
inside
Process management for avionics – Atmospheric radiation effects –
Part 6: Extreme space weather – Potential impact on the avionics environment
and electronics
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IEC TR 62396-6 ®
Edition 1.0 2017-07
TECHNICAL
REPORT
colour
inside
Process management for avionics – Atmospheric radiation effects –

Part 6: Extreme space weather – Potential impact on the avionics environment

and electronics
INTERNATIONAL
ELECTROTECHNICAL
COMMISSION
ICS 03.100.50; 31.020; 49.060 ISBN 978-2-8322-4512-5

– 2 – IEC TR 62396-6:2017 © IEC 2017
CONTENTS
FOREWORD . 3
INTRODUCTION . 5
1 Scope . 6
2 Normative references . 6
3 Terms and definitions . 6
4 Abbreviated terms and acronyms . 7
5 Extreme space weather (ESW) . 8
5.1 General . 8
5.2 Space weather relevant to avionics . 8
5.3 Examples of proton spectra for GLEs . 9
5.4 GLEs in recent history . 10
5.5 GLEs inferred from historical data . 11
5.5.1 General . 11
5.5.2 The Carrington event . 11
5.5.3 The AD774-775 event . 11
5.6 Defining an extreme space weather environment . 12
5.6.1 General . 12
5.6.2 ESW level 1: February 1956 GLE . 13
5.6.3 ESW level 2: An event much larger than the February 1956 GLE,
approximately representative of a 1-in-1 000-year event . 15
5.7 Forecasting the occurrence of an extreme space weather event . 15
5.8 Acceleration factors in ground testing . 16
5.9 Real-time atmospheric radiation monitoring and aircraft in-flight radiation
monitoring . 16
6 Considerations of ESW impact on infrastructure related to flight operations . 17
Bibliography . 18

Figure 1 – 23 February 1956 GLE – Integral and differential proton spectra fitted with
band and exponential functions . 10
Figure 2 – 19 October 1989 GLE – Integral and differential proton spectra fitted with
band and exponential functions . 10
Figure 3 – Proton spectra for galactic cosmic ray background (solid red line) and
February 1956 GLE (dashed blue line), and ratio between the two (green dotted line) . 13
Figure 4 – Integral neutron spectra at ground level (top) and 12 km altitude (bottom)
for GCR and GLE conditions at two cut-off rigidities . 14

INTERNATIONAL ELECTROTECHNICAL COMMISSION
____________
PROCESS MANAGEMENT FOR AVIONICS –
ATMOSPHERIC RADIATION EFFECTS –

Part 6: Extreme space weather –
Potential impact on the avionics environment and electronics

FOREWORD
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The main task of IEC technical committees is to prepare International Standards. However, a
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data of a different kind from that which is normally published as an International Standard, for
example "state of the art".
IEC TR 62396-6, which is a technical report, has been prepared by IEC technical
committee 107: Process management for avionics.
This first edition cancels and replaces the first edition of IEC PAS 62396-6 published in 2014.
This edition constitutes a technical revision. The technical changes with respect to the
previous edition are the contents of the present document.

– 4 – IEC TR 62396-6:2017 © IEC 2017
The text of this technical report is based on the following documents:
Enquiry draft Report on voting
107/298/DTR 107/305/RVDTR
Full information on the voting for the approval of this technical report can be found in the
report on voting indicated in the above table.
This document has been drafted in accordance with the ISO/IEC Directives, Part 2.
A list of all parts in the IEC 62396 series, published under the general title Process
management for avionics – Atmospheric radiation effects can be found on the IEC website.
The committee has decided that the contents of this document will remain unchanged until the
stability date indicated on the IEC website under "http://webstore.iec.ch" in the data related to
the specific document. At this date, the document will be
• reconfirmed,
• withdrawn,
• replaced by a revised edition, or
• amended.
A bilingual version of this publication may be issued at a later date.

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INTRODUCTION
This document provides information intended to improve the understanding of extreme space
weather events.
Rarely occurring natural hazards can have a high impact to society and national economies.
Natural events have no respect for national boundaries and the whole world can suffer. The
April 2010 Icelandic (Eyjafjallajökull) volcano eruption and resulting ash cloud and the
March 2011 Japanese earthquake and tsunami demonstrated how devastating rarely
occurring natural events can be.
In 2011 the UK recognised “extreme space weather” (ESW) events (also referred to as solar
super storms and sometimes simply as super storms) as one of these rare, but high impact,
hazards. There is evidence of the impact of ESW events in the past. During an event in
February 1956, which was monitored at ground level, a rise in radiation flux of more than 2
orders of magnitude was derived for aircraft environments.
The document does not consider high altitude nuclear explosions or any other man-made
modifications of space weather.

.
– 6 – IEC TR 62396-6:2017 © IEC 2017
PROCESS MANAGEMENT FOR AVIONICS –
ATMOSPHERIC RADIATION EFFECTS –

Part 6: Extreme space weather –
Potential impact on the avionics environment and electronics

1 Scope
This part of IEC 62396, which is a technical report, provides information intended to improve
the understanding of extreme space weather events; it details the mechanisms and conditions
that produce “extreme space weather” (ESW) as a result of a large increase in the activity on
the surface of the sun and it discusses the potential radiation environment based on
projection of previous recorded ESW.
This document does not detail the solutions with regard to the ESW events whose occurrence
is extremely rare. As the stakes related to ESW environment go widely beyond the electronics
issues and there are a lot of other elements in consideration (human concern for example),
this document does not detail potential specific provisions or mitigations.
2 Normative references
The following documents are referred to in the text in such a way that some or all of their
content constitutes requirements of this document. For dated references, only the edition
cited applies. For undated references, the latest edition of the referenced document (including
any amendments) applies.
IEC 62396-1:2016, Process management for avionics – Atmospheric radiation effects –
Part 1: Accommodation of atmospheric radiation effects via single event effects within
avionics electronic equipment
3 Terms and definitions
For the purposes of this document, the terms and definitions given in IEC 62396-1 and the
following apply.
ISO and IEC maintain terminological databases for use in standardization at the following
addresses:
• IEC Electropedia: available at http://www.electropedia.org/
• ISO Online browsing platform: available at http://www.iso.org/obp
3.1
Carrington event
largest solar storm on record, which took place from 1 to 3 September 1859, and is named
after British astronomer Richard Carrington
3.2
coronal mass ejection
CME
large burst of solar wind plasma ejected into space

3.3
extreme space weather
ESW
solar activity leading to the endangerment of engineered systems or human health and safety
3.4
geo-effective
storm causing
3.5
geomagnetic storm
worldwide disturbance of the Earth’s magnetic field induced by a solar storm
3.6
single event effect
SEE
response of a component caused by the impact of a single particle (for example galactic
cosmic rays, solar energetic particles, energetic neutrons and protons)
Note 1 to entry: The range of responses can include both non-destructive (for example upset) and destructive (for
latch-up or gate rupture) phenomena.
[SOURCE: IEC 62396-1:2016, 3.53]
3.7
solar energetic particles
SEP
high-energy particles coming from the sun
3.8
AD774
large ground level enhancement (GLE) implied by radiocarbon-dating of tree rings to have
occurred in AD774-775
4 Abbreviated terms and acronyms
ATC air traffic control
CAA Civil Aviation Authority
CME coronal mass ejection
ConOps concept of operation
EDAC error detection and correction
ESW extreme space weather
FAA Federal Aviation Administration
GCR galactic cosmic rays
GEO geostationary orbit
GLE ground level enhancement
GLNM ground level neutron monitor
GNSS global navigation satellite systems
GPS global positioning system
GRB gamma ray burst
HF high frequency
IAVWOPSG International Airways Volcano Watch Operations Group

– 8 – IEC TR 62396-6:2017 © IEC 2017
ICAO International Civil Aviation Organization
ICRP International Commission on Radiological Protection
LF low frequency
MBU multiple bit upset
NATS National Air Traffic Control Service
NOAA National Oceanic and Atmospheric Administration
QARM Quotid Atmospheric Radiation Model
RAE Royal Academy of Engineering
SEB single event burnout
SEE single event effects
SEIEG Space Environment Impact Expert Group
SEPE solar energetic particle event
SEU single event upset
SRAM static random access memory
5 Extreme space weather (ESW)
5.1 General
Space weather is defined in the 2013 report by the Royal Academy of Engineering as
“variations in the Sun, solar wind, magnetosphere, ionosphere, and thermosphere, which can
influence the performance and reliability of a variety of space-borne and ground-based
technological systems and can also endanger human health and safety” [1] . A great deal of
additional information on the many different varieties of both space weather environments and
effects is provided in the report. The probability of occurrence of extreme space weather
events is very difficult to determine, especially for the types of events most relevant to
avionics. There are approximately seventy years’ worth of direct measurements of events
affecting the atmospheric radiation environment. Recently this record has been partially
supplemented by solar events not directed at the Earth, for example the large solar eruption
in July 2012 that was measured by the Stereo A spacecraft [2]. However, it is still the case
that the upper limit for the severity of extreme space weather is unknown, and ultimately
estimates should be made based on various assumptions.
5.2 Space weather relevant to avionics
The vast majority of space weather phenomena are not directly relevant to avionics. Some, for
example ionospheric disturbances that potentially affect GPS navigation and radio
communication, are relevant to aviation generally but not to avionics specifically. This
document concerns itself solely with solar energetic particle events (SEPEs), as these pose
the primary hazard to electronic components within aircraft. Like galactic cosmic rays (GCR),
SEPEs are comprised of highly energetic protons and ions that interact with molecules in the
upper atmosphere and produce cascades of secondary particles, of which neutrons are of
primary interest in this context. The secondary neutrons are able to penetrate the atmosphere
at aviation altitudes and below, where they can pose a threat to avionics through single event
effects (SEEs) in sensitive components. Much more detail on this general SEE phenomenon
is given in IEC 62396-1 and more background on the threat of ESW to aviation and other
infrastructure is given in the RAE report. [1]
Knowledge of the SEPE environment is dependent on measurements and thus uncertainties
increase substantially with more historical events. In the space era (1960s onwards) there
are relatively good measurements from space-borne instruments of SEPE proton fluxes at the
___________
Numbers in square brackets refer to the Bibliography.

lower end of the relevant spectral energy range (i.e. a few hundred MeV and below). These
data provide an effect characterisation of such events on satellites where lower energy
protons dominate single event effects rates. For terrestrial effects, including the aviation
environment, it is crucial to supplement these data with measurements pertaining to the
higher energy part of the proton spectra. Protons need a minimum energy of around 300 MeV
to instigate secondary cascades that can penetrate to aircraft altitudes. At low latitudes, even
higher energies are required for primary particles to penetrate the shielding provided by the
Earth’s magnetic field. Indeed, it is this geomagnetic shielding that effectively enables
knowledge of the higher energy end of the proton spectrum to be obtained. A global network
of ground level neutron monitor (GLMN) stations provides continuous measurement of high
energy neutron fluxes at the Earth’s surface over a broad range of latitudes. These record not
only the background GCR-induced neutron flux that varies with an eleven-year period in anti-
phase with the solar cycle, but also the infrequent and transient enhancements caused by the
most powerful SEPEs. A minority of SEPEs produce a sufficient number of very high energy
(~GeV and above) protons to cause measurable neutron flux increases over a range of
latitudes within the GLNM network. During these ground level enhancements (GLEs) the
geomagnetic field effectively acts as a giant spectrometer, providing proxy information on the
incident proton spectrum via relative neutron flux increases at different vertical cut-off
rigidities. Vertical cut-off rigidity is the ratio of momentum to charge required by a charged
particle (e.g. a proton) to reach the upper atmosphere at a certain point within the
magnetosphere. It is a function of both latitude and longitude. If a number of neutron monitors
at similar rigidities show differing levels of neutron flux increase, this is a measure of the
anisotropy of the event. Tylka and Dietrich [3] have used a combination of neutron monitor
data and satellite instrument data to fit proton spectra for 53 of the 67 GLEs recorded since
1956.
5.3 Examples of proton spectra for GLEs
Comparison plots from Tylka and Dietrich [3] of the 23 February 1956 event and the
19 October 1989 ground level events, both of which were large solar events, are given below;
these are based on ground level radiation monitoring of the event.
A significant difference between the spectra is that the 1956 spectrum contains more (over an
order of magnitude) high energy protons (above 1 000 MeV) than the 1989 event. The events
have been termed ground level events because there has been a large increase in
atmospheric radiation at ground level which has been monitored. The radiation levels
monitored at ground level were significantly higher for the February 1956 event than the
October 1989 event. Radiation ground level monitoring has only been available in modern
times for about the last 100 years and the February 1956 event can be considered a nominal
ESW event. At that time during the 1950s electronics was in its infancy with most systems
based on thermionic valves and less prone to influence from atmospheric radiation.
The 23 February 1956 and 19 October 1989 solar proton spectra are given as examples of the
different fitting methods in Figure 1 and Figure 2 respectively. It should be noted that only the
fits are shown in these plots (symbols do not represent data). The band spectral form,
comprised of a double power-law, was deemed to be the best fit to data.

– 10 – IEC TR 62396-6:2017 © IEC 2017
Band-integral
Band-diff.
EXP-integral
EXP-diff.
0,1
10 100 1 000 10 000
Proton energy (MeV)
IEC
Figure 1 – 23 February 1956 GLE – Integral and differential proton spectra
fitted with band and exponential functions

10 Band-integral
Band-diff.
EXP-integral
EXP-diff.
–1
10 100 1 000 10 000
Proton energy (MeV)
IEC
Figure 2 – 19 October 1989 GLE – Integral and differential proton spectra
fitted with band and exponential functions
5.4 GLEs in recent history
Since 1942 a total of 71 GLEs have been recorded by ground-based instruments. In the very
early years these were measured by ionisation chambers, with the invention of neutron
monitors coming a few years later in 1948. Thus, the frequency of GLEs is approximately one
2 2
2 2 Integral and diff. fluence, #/cm and #/cm (MeV)
Integral and diff. fluence, #/cm and #/cm (MeV)

per year, although it is notable that there has only been one GLE in the 2007 to 2015 time
frame. The largest GLE on record occurred on 23 February 1956, leading to a 50-fold
increase in count rates at the neutron monitor station in Leeds, UK. This can be considered as
the most extreme directly-observed space weather event in the context of threats to avionics,
however it is not a worst possible case (see 5.5.1). Tylka and Dietrich have calculated the
integral proton fluence for this event above a rigidity of 1 GV (435 MeV) as ~4 x 10

–2
proton·cm [3]. Another common metric for characterising SEPEs and GLEs is the integral
proton fluence above 30 MeV, F . A more physically relevant threshold for atmospheric
neutron production, however, is 300 MeV. Thus, for completeness, both thresholds are used
in this document. Estimates of F and F for the February 1956 event vary, though

30 300
commonly used figures that are consistent with the Tylka and Dietrich analysis are as follows:
9 –2
F (Feb ’56) ≈ 10 proton·cm
7 –2
F (Feb ’56) ≈ 8 x 10 proton·cm
These figures are used later in the document to scale other event magnitudes and worst
...