How to survive a solar proton flare

Solar proton flares appear to be fairly rare. The last ones to cause severe injury to life on Earth seem to have occurred 12,900 tears ago, producing what some call the Rancholabrean (or Labrean for short, for the La Brea tar pits) extinction, that wiped out most megafauna, such as mastodons, mammoths, and giant ground sloths (megatherium) from North America, Northern Europe, and northern Asia. It was not a complete, worldwide, extinction event. It is discussed in a companion article, Earth Changes .

The focus in this article is how to survive another such event.
The threat is from a solar flare that delivers intense proton radiation that breaks through the Earth's magnetosphere. Most of the radiation would come almost straight down, and consist not only of protons but of secondary radiation such as neutrons and gamma radiation, both of which can penetrate several feet of shielding, with up to 3-10 sieverts of radiation. 3 are usually fatal. This is not like the radiation that would be produced in a nuclear war, which would include radiation from dust (fallout).
There may be little or no warning, and such warning as might be issued might be only about an hour in advance. Flares can be seen by solar observatories in time to warn astronauts of a proton storm, but it does not appear that the Emergency Warning System is prepared for an event of this kind for the entire nation. If it came in the middle of the night, most people would probably die soon.

Most modern homes will not provide enough shelter. You need to get under at least three feet of concrete, stone, or soil. The basement of a three-story office building might work, if the floors are concrete. A concrete bridge or drain pipe might work.

Be on the lookout for shelters.

Try to identify anything that might provide shelter near where you live, work, or travel regularly. You may not find much. If you get warning in time, you may have some time to look, but it is best to have already spotted some.

Carry a radiation detector.

There are some nice ones available, but the most practical is likely a radiation badge, that needs no power, and can be carried around at all times. One I like is the RAD Triage 50. It can be worn every day for two years, and one can keep a backup in a freezer for another ten years. One would use it to determine which locations have the most shelter.

Keep a supply of water.

You will probably need water for a week, Use the radiation detector to determine when it is safe to come out of the shelter. Might want to keep a LifeStraw Personal Water Filter for each person in your party.

Keep a firearm.

You may have to fight for use of a shelter. Even nice people can become dangerous when they think they are about to die.

Get emergency power.

A proton flare is likely to cause the same kind of damage as a coronal mass ejection or EMP attack. Even if the Shield Act  is passed and implemented, it will only protect the electric grid. Unshielded will be millions of other electronic devices, including phones, radios, and motor vehicles. You need to get photoelectric panels and emergency generators (assuming you can get fuel for them). Buildings with solar roof panels may become essential. Older vehicles that can be stripped of complicated electronics may be critical.

Establish emergency communications.

It is likely that most communication systems will fail, either as a direct result of the proton storm, or from the disablement of operators. The best alternative is likely to be ham radio transceivers. A good kind are portable handheld units or a GP-5 survival radio that can operate for a long time on batteries. You may also need portable Faraday bags and Faraday cages you can build to protect electronics from EMP, CMEs and proton radiation. You can also provide Faraday shielding for buildings but most of these won't provide proton radiation shielding for people.

Organize survivors.

You will need to use a kind of triage system that separates those who don't need help from those who are beyond help, with a middle group that can benefit from help, even it only buys them a few years before they succumb from cancer. Look for preppers and militia activists. Some of them imagine living in the wilderness for extended periods of time, but wildlife and livestock may also not survive, and small isolated groups are likely to be indefensible. Communities of a few thousand individuals are more likely to survive long enough to repopulate the country.
The U.S. military has an extensive system of underground bunkers and tunnels, for themselves and a few senior officials, if they can get to them in time. When they come out they are likely to need the help of other survivors, and it is important to ally with them, and not become competitors.

The first level of government to be established is local, counties or small towns. New law enforcement personnel may need to be elected and trained. Their priority may need to be to get supplies of food and medicine delivered from where they are produced to where they are needed.

The proper legal basis for doing all this is the US. Constitution as originally understood.

Notes:

1. Vivos flare survival shelters