None whatsoever. The alarm message is sent when the light level at the aurora detector exceeds a preset threshold, meaning that the northern lights are visible in the sky at that moment. A display should last long enough for you to drive away from city lights (see #4 below), but if you don't read your e-mail until the following morning, you're out of luck.
If you have a cell phone, pager, or other wireless communication device, it can probably receive the alarm e-mails; check with your service provider. This can be a convenient way to ensure that alarms will wake you up anytime during the night. The alarm mailing lists distribute only the alarm messages, never anything else, and these are infrequent (usually a few per month or less), so people who have to pay per message should not need to worry.
During the largest displays in North America, like the one on 31 March 2001, the aurora may be seen at least as far south as Mexico; these grand events usually happen once or twice in every 11-year solar activity cycle. Here in central Illinois, a good aurora can be seen at least once a year (more during the solar maximum, less during the solar minimum).
Almost as important as your latitude are your local observing conditions. Because of light pollution, most auroras will be all but invisible from large towns or cities. You must find a dark rural observing site and allow your eyes at least ten minutes to adapt to the darkness once you arrive. Your local astronomy club is a good resource for finding nearby dark sites.
The irony of light pollution is that common-sense lighting practices would drastically reduce the amount of pollution, while at the same time improving visibility, safety, and energy efficiency. You can help by joining me in supporting the International Dark-Sky Association with your membership dues!
It varies. Usually the more intense the aurora, the longer it lasts. The really big displays tend to be visible in one form or another for most of the night, although there will be a definite peak lasting an hour or two. A faint display might last half an hour or even less.
Possibly. Because the aurora is a high altitude phenomenon, the same glow that is visible from one place can also be seen hundreds of miles away. On large scales, the aurora is an oval shape centered around the magnetic poles, and it usually reaches similar latitudes over a wide area (tens of degrees in longitude).
The real problem is the weather. You may see useless alarms when the skies are clear in Walla Walla, but cloudy at your location. You might also miss displays that you could have seen, if the weather at the detector is bad. Despite this, many people across North America have found the alarms useful.
False alarms are rare, but they tend to occur in clusters since the root cause often remains on consecutive nights. These include insufficient compensation of the alarm threshold for bright moonlight, city lights reflecting from snow cover and low clouds, lightning, and even the occasional software bug.
Over time, the false alarm rate has been decreasing, and they are now less common than real auroras. You can now expect to go for months without needless interruptions of sleep.
Sure. Even "dumb" phones have an email-to-text-message gateway, and with smart phones (obviously) this is easy. If you don't set things up so you get awakened when the message comes in, you'll probably miss the aurora (see answer #1).
You should see a test message on the first of every month. The lack of other messages means that there have been no false alarms---a good thing! Keep in mind that when the popular media finally pays attention to solar activity and space weather, they sometimes hype it out of proportion. Thus, near solar maximum, people get the impression that major auroras are happening every week. In reality, there are long dry spells with nothing going on at middle latitudes---the entire northern hemisphere winter of 2000-2001, for example.
Impressive solar activity may fail to produce a middle- or low-latitude aurora even when forecasters' confidence is high. In other cases there may well have been a dramatic aurora, but no alarm was issued. This could happen if the weather at the detector site was thick overcast, or if the aurora happened during the daytime. This is one reason why the Aurora Alarm is so useful: It only alerts you to the auroras that you can see.
Complete circuit details can be found on the technical information page of this web site. The aurora detector was the topic for my senior engineering design project at Walla Walla College, and the choice of parts reflects more what was on-hand in the laboratory than what would be convenient for home builders to duplicate. Unless you have a knowledge of electronics that goes beyond the ability to reproduce a schematic diagram, this project will probably be an exercise in frustration. If you are serious about building one, though, please contact me.
The cost of the parts, if purchased new, will be at least $300. If you can find a surplus photomultiplier tube and optical filter, or elect to design and build the high voltage power supply yourself, it may be possible to save $100-$200.
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