  The quantum fluctuations of an "accelerated" vacuum state, that is vacuum
fluctuations in the presence of a constant electromagnetic field, can be
described by the temperature $\TEH$. Considering $\TEH$ for the gyromagnetic
factor $g=1$ we show that $\TEH(g=1)=\THU$, where $\THU$ is the Unruh
temperature experienced by an accelerated observer. We conjecture that both
particle production and nonlinear field effects inherent in the Unruh
accelerated observer case are described by the case $g=1$ QED of strong fields.
We present rates of particle production for $g=0,1,2$ and show that the case
$g=1$ is experimentally distinguishable from $g=0,2$. Therefore, either
accelerated observers are distinguishable from accelerated vacuum or there is
unexpected modification of the theoretical framework.
