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Today, tomorrow,
next week, next year. . . sometime in the coming decades. . .
our planet could once again be hit by an intense volley of Galactic
cosmic rays. It will come cloaked and hidden from us, until
the very moment it strikes. We live on the edge of a galactic
volcano. Knowing neither the time, the magnitude, nor the
severity of the next eruption or its impact on our environment,
we stand unprepared to
deal with this event, much less anticipate its arrival.
Galactic Superwaves: Their Effects on Life and Society
When cosmic rays from Galactic superwaves
impact the Earth's atmosphere, they produce "electron cascades."
Each primary cosmic ray generates millions of secondary
high energy electrons. Many of these particles scatter
upwards and become trapped by the Earth's magnetic field to form
radiation belts similar to those created by high altitude nuclear
explosions. In just one day, a major Galactic superwave
event would inject into the geomagnetic field a particle energy
equivalent to 1000 one-megaton hydrogen bomb explosions (1025
ergs). At this rate, the energy delivered to the belts
after one year would exceed 30,000 times the energy received
from the most powerful solar cosmic ray storms observed in modern
times.
Such energized radiation belts could cause a global communications
blackout by creating radio static and by permanently damaging
critical electronic components of communication satellites. Air
travel during such conditions would be extremely hazardous. The
resulting atmospheric ionization would destroy the ozone layer,
and increase skin cancer rates, due to high levels of UV reaching
the Earth's surface; the cosmic ray particles penetrating to
ground level would significantly increase cell mutation rates.
Galactic superwaves may also produce an intense electromagnetic
pulse (EMP) whenever a cosmic ray front happens to strike the
Earth's atmosphere. Galactic superwaves such as those that
arrived during the last ice age could have generated pulses delivering
tens of thousands of volts per meter in times as short as a billionth
of a second, comparable to the early-time EMP signal from a high-altitude
nuclear explosion (see Figure 7).
In addition, there is the danger that a superwave could transport
outlying cosmic dust into the solar system which could seriously
affect the Earth's climate possibly triggering a new ice age.
Although there is a small probability that the next superwave
will be as catastrophic as the one at the end of the last ice
age, even the less intense, more frequent events would be quite
hazardous for the global economy.
Figure 7. Intensity vs. time plot for EMP
from a high-altitude nuclear explosion (solid line) compared
to that from a hypothetical superwave (dashed line). The numbers
designate early-time, intermediate-time, and late-time EMP phases
(ns = nanoseconds, µs = microseconds).
In March 2009, the U.S. National Research
Council published a report entitled Severe
Space Weather Events: Understanding Societal and Economic Impacts;
see also March 2009 New Scientist
for a summary. It describes hazards to modern society
that could occur should we experience a large magnitude solar
storm, similar to the 1859 Carrington
event solar flare. Many of the adverse effects the
report describes are the same as those that would occur during
the arrival of a superwave, even one of relatively low magnitude.
The four-second extragalactic gamma ray burst that arrived
in 1983, did have a measurable effect on radio transmissions
used for global navigation and communication.(20)
By comparison, the "minor" superwave events discussed
above might have total energies hundreds of millions of times
greater than this.
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