[PTTG]

Figured I'd revisit this. I like a number of these possibilities.

Originally Posted by PTTG

A cosmic energy wave struck Earth and caused a number of catastrophes. Here they are:

1: Global geomagnetic storm of cosmic proportions, paired with heavy charged particle bombardment. Huge lighting discharges all over the surface, and even deeply buried conductors undergo extreme magnetic flux.

The electrical discharges destroyed all but the most hardened electrical infrastructure and directly killed approximately 5% of the population directly. The firestorms started by the electrical surges killed about as many. The loss of long-range communication and advanced medicine caused somewhat more. The big problem was the loss of transport tech when combined with the smoke from the fires and the associated loss of crop productivity.

Those regions with strong group identities and limited political strife were able to stabilize. Those that also has repairable industrial capacity recovered over the next few decades and by 2020 some cities were even rebuilding their computer networks. Other regions weren't so lucky, either stuck as effectively feudal substates of industrial regions, or else still anarchic wastes a generation after the storm.

Pre-storm military strength was of only moderate importance, as the electrical interference overcame even the best hardening and was capable of affecting even deeply buried equipment. Plus, even the working equipment would only last so long...

2: Cosmic ray torrent, irradiating everything on the surface for over 20 hours.

Due to the northerly positioning of Vega and the duration of the wave, only Antarctica and parts of South America south of the Falklands remained safe from the cosmic ray shower. In the most highly effected areas, surface radiation levels skyrocketed to over three million times normal background levels. Some suspect that the wave in part changed the way radiation passes through the atmosphere in order to cause this effect. At these levels, death was quite likely even in a short term.

The peak radiation levels were reached from western Canada eastward at the 51 degree line around the pole all the way around and terminating in eastern Siberia, but dangerous radiation levels covered the entire northern hemisphere and much of the south as well. While the atmosphere seemed to be ineffective, surface defenses such as soil cover and such were as effective as normal.

The extreme radiation ultimately killed some 15% of the population over the 20 hour irradiation, and an additional 20% sickened and died over the following two years. Of those, the vast majority of the victims came from the global north. The Falklands were only moderately affected, in part due to Vega being over the horizon only briefly even in the northenmost part of the chain. It became one of the major organizational hubs after the wave.

In the north, subterranian bunkers became the centers of reconquest. Aside from the eeree dead trees, the irradiated land was fairly safe to recover. Civil collapse, as seen elsewhere, caused more deaths than the actual disaster did, especially in the equitorial and southern nations.

3: Change in fundamental constants in the presence of the wave, causing all solar system bodies larger than a few hundred km across to break into fragments.

There were no survivors. Those that visit this reality might find themselves on a chunk of terrain ripped from its moorings and floating freely and out of sight of the nearest piece of what remains of Earth.