{"id":3683,"date":"2011-09-19T11:49:02","date_gmt":"2011-09-19T15:49:02","guid":{"rendered":"http:\/\/www.engineeringradio.us\/blog\/?p=3928"},"modified":"2023-04-29T13:39:29","modified_gmt":"2023-04-29T17:39:29","slug":"burning-telegraph-wires-and-other-irregularities","status":"publish","type":"post","link":"https:\/\/www.engineeringradio.us\/blog\/2011\/09\/burning-telegraph-wires-and-other-irregularities\/","title":{"rendered":"Burning Telegraph Wires and other Irregularities"},"content":{"rendered":"\n

By now, you have heard of the great solar flare of 1859<\/a> that set telegraph wires afire across the US and Europe. \u00a0This phenomenon was due to a large electromagnetic pulse from the earth’s magnetosphere interacting with the particles from a Coronal Mass Ejection (CME) caused by the solar flare. \u00a0The long stretches of wire suspended above the earth acted like a large generator winding and cutting through the magnetic field, which in turn caused voltage (Electromagnetic force or EMF), which in turn, caused the fires.<\/p>\n\n\n\n

In 1859 our understanding of electricity and magnetics is not what it is today, thus, the fires were likely caused by overloaded conductors without means to bypass excess electrical energy to ground.<\/p>\n\n\n\n

\"Schematic<\/a>
Schematic of Earth’s magnetosphere, courtesy NASA<\/figcaption><\/figure>\n\n\n\n

Fast forward to today. \u00a0We are in the upswing of solar cycle 24, which is expected to peak in May of 2013. \u00a0NASA<\/a> predicts that this will be the lowest sunspot peak since 1907. \u00a0That does not necessarily mean the coast is clear. \u00a0Over the last 11 years since solar cycle 23 peaked, computers and electronic automation have proliferated exponentially, becoming the norm. \u00a0Things like GPS not only guide clueless travelers where to turn but also sync up all those cellular telephone transmitters with timing signals. \u00a0IP networks, SCADA, telephone networks, and so on all run on some form of CPU. \u00a0Newer Energy Star appliances like toasters and refrigerators also have CPUs. \u00a0 That technology has yet to experience a large electromagnetic pulse <\/a>(EMP) in the real world. \u00a0Things could indeed get hairy if a moderate to large class X solar flare generated a CME that was polarized correctly to interact with Earth’s magnetic field and cause damage at ground level.<\/p>\n\n\n\n

Solar flares and CME are slow-moving events, with 1-2 days warning before the effects of a CME reach Earth. \u00a0One can stay apprised of solar flares and other solar activity by subscribing to NOAA Space Weather Prediction Center’s<\/a> email service.<\/p>\n\n\n\n

\"HEMP<\/a>
HEMP Mechanism for 400 kM high altitude burst<\/figcaption><\/figure>\n\n\n\n

Of greater concern is other sources of EMP like high altitude nuclear explosions<\/a>\u00a0(HEMP). \u00a0Those types of events, while rare, can happen. \u00a0The good news is, the defense mechanisms for solar flares, high-altitude nuclear bursts and lightning-induced EMP are the same. \u00a0They are effective grounding, shielding, filtering and surge suppression.1<\/sup> \u00a0Of the three EMP scenarios, high altitude nuclear burst has the tightest design spec, so creating a building that incorporates the ideas in MIL-STD-188-125-1 specifications is a good start.<\/p>\n\n\n\n

The question becomes, is all of this really necessary. \u00a0It depends on how important it is to radio station ownership to remain on the air during such an event. \u00a0Based on historical information and global geopolitics, the probabilities of such an occurrence are:<\/p>\n\n\n\n