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Old 09-13-2014, 01:51 AM   #10
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Default Re: Back Up Your Data NOW - Solar Flares

This discussion has piqued my interest. Time for some physics. Anyone else want to do physics?

There are a couple ways a solar flare can in theory corrupt or erase data. The first is via photons ionizing the material the data is stored in. (Si and Si- for an SSD, and Cobalt-Chrome-Platinum alloys in your standard HDD) I think I'm going to not do mat at 1 AM this fine morning because while I'm interested I'm tired, and besides while I can do the math on data corruption in a single atom setup (and then scale up), i suspect there might be complications from alloys. Onto the physics-y part. A Faraday cage would protect against this, but then again so is the casing for the hard drive itself, not to mention your house and the atmosphere etc.

OK fine a bit of math. At the earths surface the sun produces approx 1kW/m^2. This comes out to (assume avg photon is 600nm) 10^22 photon*sec/m^2. (photon-seconds per square meter. Doncha love units?) A hard drive is about 4 square inches, simple math says that if you stuck a hard drive in direct sunlight about 2*10^19 photons hit the thing every second. In theory the majority of these photons could ionize Si-. (I found a doc that says this ion has an ionization energy of like 1 or 2 eV) Because I can carry a laptop around with me in direct sunlight and it works they obviously don't. Without doing any math (beyond what's already done), I think I can hazard a guess that if you are worried that you are getting enough photons that you need to worry about data corruption via light you have bigger problems. Like you no longer have an ozone layer big.

Method number 2: magnets. Turns out a thing that can accompany flares is a big chunk of stuff that comes out of the sun, called a coronal mass ejection.(CME) These things can really screw with the Earth's magnetic field - which isn't very good for a couple reasons. The big thing is that changing a magnetic field - quite possibly intensely - will induct current into various things we don't want currently inducted to. A faraday cage can protect against this, but probably shouldn't be touching the drive - especially the connector - and should be grounded. Aluminum foil meets neither of these requirements. This can in theory lead to some charge getting stored in the drive itself - which (I'm tired and would have to noodle around with this more to be sure) I'm guessing can affect the drive. Of course if you are inducting enough charge that this matters then you probably once again have bigger things to worry about. Like having no electricity, and nuclear power plants melting down.
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