Upper Limit of EM-Field Strength

[Kayser]

Hello!
Which are the highest theoretically possible electric and magnetic vacuum field strengths E and H? How are they calculated?

 

[mfb]

Why do you think they are limited?

Above the Schwinger limit things get complicated, but it is not a hard upper limit.

 

[Kayser]

Thank you- Hans - for your sophisticated reply. I knew the Schwinger limit, but nothing comparable to magnetic fields. The subject remains open to unlimited speculation.

 

[mfb]

Magnetic fields in one system are electric fields in another system. The transformations are not completely arbitrary, but something that limits the electric field strength should also limit the magnetic field strength.

Who is Hans?