ing into account that <span class="math notranslate nohighlight">\(\displaystyle dt =\frac {dz} {v}\)</span>, then:</p>
<div class="math notranslate nohighlight">
\[a '' =\displaystyle\frac {e} {a}\frac {2I} {m\gamma ^ 3\upsilon ^ 3}.\]</div>
<p>We introduce the characteristic Alfven current <span class="math notranslate nohighlight">\(I_a =\displaystyle\frac {mc ^ 3} {e}\approx\)</span> 17 kA, therefore:</p>
<div class="math notranslate nohighlight">
\[a '' =\displaystyle\frac {2I} {I_a (\beta\gamma) ^ 3}\