I am envisioning an apocalypse scenario where a majority of vehicles and electronics are disabled and a vast majority of Grid infrastructure is destroyed. The Carrington Event in the 1800s produced massive E3 geomagnetic disturbances that caused a lot of damage to existing communications infrastructure and caused brilliant auroras across a huge swathe of latitudes. I've read that CMEs can cause E3 type EMP creating DC issues with larger electrical systems, as long wires act as antennas and can damage transformers, etc. Similar to the Quebec power outage when a transformer was destroyed, I am envisioning a scenario where a massive X-30+ solar flare immediately precedes an equally large CME. CMEs take longer to travel the 93 million mile distance, so the flare effectively "blocks" the preventative measures that would have otherwise occurred as satellites cannot see the plasma cloud encroaching on us.
From what I've read, the CME does not produce E1 and E2 issues, which are caused by gamma radiation from nuclear blasts in the atmosphere, causing electrons to separate and bombard the Earth. I have read, however, that there were previously "stealth" CMEs which were observed where CMEs occurring on the non-Earth facing side of the sun happen and release gamma rays which, due to the different rotation of the sun and subsequent magnetic fields, swirled around and smashed back into the sun.
My proposition for feasibility is this: The sun undergoes an event which causes multiple massive magnetic abnormalities causing an extremely rapid buildup of pressure. CMEs explode from the sun with masses of highly energetic plasma streaming into space. The magnetic abnormalities cause the aforementioned massive flare, which is observed by NASA, NOAA, and a number of observatories around the Earth. The flare itself is so energetic that it damages the satellites as it approaches and causes issues with radio communications with the satellites more protected by the Earth's magnetic field. In the ensuing hours, gamma rays emitted from the massive event begin to bombard the Earth. [From what I've read, there are a number of issues with this, as it can cause ozone to deplete, buildup of nitrogen di-oxide, etc. and I will have to work out the levels of this etc.] The gamma rays rip through our atmosphere and begin bombarding the stratosphere across the entire exposed portion of the planet. As we rotate, we are under a random bombardment from E1 energy, quickly destroying phones, automotive electronics, transformers, protection systems designed to manage geomagnetic disturbances, etc. This is a nearly global event. Then, we are bathed in a blanket of intense, horrific CME. One of the ejections was not only directed at Earth, but was magnitudes of order larger than any precedents. The power grid is almost entirely destroyed.
I believe the power grid aspect is fully possible, hypothetically. I am just unsure whether the gamma rays could even be released and "happen" to strike the Earth in such a bombarding, horrific fashion, acting as a global E1 EMP.