Gizmodo's Watch Elon Musk Describe Terraforming Mars to Stephen Colbert links to the video (shown below). Their second article Elon Musk Clarifies His Plan to "Nuke Mars" quotes Musk from a SolarCity launch event in Times Square New York a few weeks later in late 2015:
“What I was talking about,” said Musk, “was having a series of very large, by our standards, but very small by calamity standards, essentially having two tiny pulsing suns over the poles. They’re really above the planet. Not on the planet.
“Every several seconds,” Musk continued “send large fusion bombs over the poles. A lot of people don’t appreciate that our sun is a giant fusion explosion,” he added, to a reportedly silent audience.
What Musk keeps trying to explain here is a scheme for heating up the surface of Mars quickly, in order to make the planet hospitable to plant life. There’s a lot of carbon dioxide locked up in Mars’ poles as dry ice, and CO2, as we know, is a powerful global warming agent. If we release enough energy over the poles, we might just be able to send all that CO2 skyward, warming the atmosphere enough to kickstart a positive feedback loop and a runaway greenhouse effect.
- The detonation would be atmospheric, not on the surface.
- Mars' atmosphere is roughly speaking 1% that of Earth, so the gamma-ray attenuation length is roughly 100x longer.
- The "Compton current" (Compton electrons produced by the gamma-ray pulse) would be produced over a far larger shell, creating a nuclear electromagnetic pulse with far different characteristics than the atmospheric detonation of a neutron bomb on Earth would.
- While characteristics of terrestrial EMPs are affected by Earth's magnetic field, the E1 pulse certainly happens with or without one.
- For a start on how to think about the Compton current and the generation of the prompt electromagnetic pulse, see for example Justification and verification of High Altitude EMP Theory, Part 1 as well as the Rand Corporation report The Compton Current and the Energy Deposition Rate from Gamma Quanta — A Monte Carlo Calculation.
Using nuclear devices for terraforming might be considered for other purposes besides liberating gas from the polar ice caps, and very low yield devices make handy (but radioactive) tools for large scale excavation. I'm not advocating any of this or asking about utility here. The question is about the EMP felt by orbiting spacecraft.
Question: Would the EMP from atmospheric polar nuclear detonations on Mars felt by orbiting spacecraft be larger or smaller than (if it were) on Earth?
For this question (originally inspired by discussion below this answer) I'm looking particularly for sourced answers that draw upon science.