Editing Geomagnetic storm (section)

==== Communications ====

[[High frequency]] (3–30&nbsp;MHz) communication systems use the ionosphere to reflect radio signals over long distances. Ionospheric storms can affect radio communication at all latitudes. Some frequencies are absorbed and others are reflected, leading to rapidly fluctuating signals and unexpected [[radio propagation|propagation]] paths. TV and commercial radio stations are little affected by solar activity, but ground-to-air, ship-to-shore, [[shortwave]] [[Broadcasting|broadcast]] and [[amateur radio]] (mostly the bands below 30&nbsp;MHz) are frequently disrupted. Radio operators using HF bands rely upon solar and geomagnetic alerts to keep their communication circuits up and running.

Military detection or early warning systems operating in the high frequency range are also affected by solar activity. The ''[[over-the-horizon radar]]'' bounces signals off the ionosphere to monitor the launch of aircraft and missiles from long distances. During geomagnetic storms, this system can be severely hampered by radio clutter. Also some submarine detection systems use the magnetic signatures of submarines as one input to their locating schemes. Geomagnetic storms can mask and distort these signals.

The [[Federal Aviation Administration]] routinely receives alerts of solar radio bursts so that they can recognize communication problems and avoid unnecessary maintenance. When an aircraft and a ground station are aligned with the Sun, high levels of noise can occur on air-control radio frequencies.{{citation needed|date=August 2016}} This can also happen on [[UHF]] and [[Super high frequency|SHF]] satellite communications, when an Earth station, a satellite and the Sun are in [[Sun outage|alignment]]. In order to prevent unnecessary maintenance on satellite communications systems aboard aircraft AirSatOne provides a live feed for geophysical events from NOAA's [[Space Weather Prediction Center]].<ref>{{cite web |url=https://www.airsatone.com//gams |title=AirSatOne's Live Feed}}</ref> allows users to view observed and predicted space storms. Geophysical Alerts are important to flight crews and maintenance personnel to determine if any upcoming activity or history has or will have an effect on satellite communications, GPS navigation and HF Communications.

[[electrical telegraph|Telegraph]] lines in the past were affected by geomagnetic storms. Telegraphs used a single long wire for the data line, stretching for many miles, using the ground as the return wire and fed with [[Direct current|DC]] power from a battery; this made them (together with the power lines mentioned below) susceptible to being influenced by the fluctuations caused by the [[ring current]]. The voltage/current induced by the geomagnetic storm could have diminished the signal, when subtracted from the battery polarity, or to overly strong and spurious signals when added to it; some operators learned to disconnect the battery and rely on the induced current as their power source. In extreme cases the induced current was so high the coils at the receiving side burst in flames, or the operators received electric shocks. Geomagnetic storms affect also long-haul telephone lines, including undersea cables unless they are [[fiber optic]].<ref>{{Cite web|url=http://image.gsfc.nasa.gov/poetry/storm/storms.html|archive-url=https://web.archive.org/web/20050911073432/http://image.gsfc.nasa.gov/poetry/storm/storms.html|url-status=dead|title=image.gsfc.nasa.gov|archive-date=11 September 2005}}</ref>

Damage to communications satellites can disrupt non-terrestrial telephone, television, radio and Internet links.<ref>{{cite news|title=Solar Storms Could Be Earth's Next Katrina|newspaper = NPR.org|url=https://www.npr.org/templates/story/story.php?storyId=124125001|access-date=2010-03-04}}</ref> The [[United States National Academy of Sciences|National Academy of Sciences]] reported in 2008 on possible scenarios of widespread disruption in the 2012–2013 solar peak.<ref>{{cite book |title=Severe Space Weather Events—Understanding Societal and Economic Impacts: Workshop Report |publisher=National Academies Press |location=Washington, D.C. |date=2008 |doi=10.17226/12507 |isbn=978-0-309-12769-1 |url=http://www.nap.edu/catalog.php?record_id=12507#toc}}</ref> A solar superstorm could cause large-scale global months-long [[Internet outage]]s. A study describes potential mitigation measures and exceptions – such as user-powered [[Wireless mesh network|mesh networks]], related [[peer-to-peer]] applications and new protocols – and analyzes the robustness of the current [[Internet infrastructure]].<ref>{{cite news |title=Computer scientist warns global internet is not prepared for a large solar storm |url=https://techxplore.com/news/2021-08-scientist-global-internet-large-solar.html |access-date=22 September 2021 |work=techxplore.com |language=en}}</ref><ref>{{cite news |title=A Bad Solar Storm Could Cause an 'Internet Apocalypse' |url=https://www.wired.com/story/solar-storm-internet-apocalypse-undersea-cables/ |access-date=22 September 2021 |magazine=Wired}}</ref><ref>{{cite conference |last1=Jyothi |first1=Sangeetha Abdu |book-title=Proceedings of the 2021 ACM SIGCOMM 2021 Conference |title=Solar superstorms: Planning for an internet apocalypse |date=9 August 2021 |pages=692–704 |doi=10.1145/3452296.3472916 |publisher=Association for Computing Machinery|isbn=9781450383837 |doi-access=free }}</ref>