I need to know Earth's magnetic field at my geographic location. I tried to google it, but I don't see anything concrete; moreover, I see tons of contradicting information on how often does the magnetic field change direction and how fast is it decaying. Does anyone know a reliable source? All I need is an estimate, but for a concrete location (say, San Francisco, CA, USA, 37°39′22″N, 122°25′32″W) and approximate date as August 2006.
The best answer will get 10 points. No silly answers, please.
2006-08-22 19:30:25 · 4 answers · asked by Snowflake 7 in Science & Mathematics ➔ Physics
Oh, sorry, I'm not specific enough: I need the magnetic field strength in Gauss or in Tesla.
2006-08-22 20:05:30 · update #1
Direction of the magnetic field is less important to me. I'm sorry again for using the lab jargon rather then scientific term. I'm looking to find the information on Earth's magnetic field *strenght*
2006-08-22 20:09:09 · update #2
Magnetif field is not routinely surveyed with the degree of accuracy that you are implying. If you need a very precise location then you will absolutely have to make the measurement yourself. Howevewer, you can see the raw data for the USGS magnetic field observatories at http://geomag.usgs.gov/observatories/data/realtime/. You need to look at the H value, which appear to be in nano Tesla.
2006-08-22 20:30:35 · answer #1 · answered by Anonymous · 0⤊ 0⤋
The field has two components: the horizontal component, which you can see with a compass of the usual sort (it's called variation or deviation, depending on who you are talking to), and a vertical component -- the field lines are not parallel to the surface of the earth. Only rarely is the latter of interest. According to my aviation chart, the variation at San Francisco was approximately 15 degrees 20 minutes east in 2003. It changes only slowly, so that number is probably still quite good. Local effects, such as buildings or buried masses (natural or artificial) can cause appreciable change, so if you need really good data you need to go measure it yourself. I use a Suunto KB-14 compass that is good to about a tenth of a degree, available from Ben Meadows (benmeadows.com) for about $90.
Subsequent responder has found an excellent site. Particularly read the "health warning" to find out how your data can get screwed up.
2006-08-23 02:54:02 · answer #2 · answered by Anonymous · 0⤊ 0⤋
Try the US Coast and Geodetic service. They produce maps which give magnetic North for a particular location. The magnetic North changes all the time, it is in the general area of far northeastern Canada, but it moves. When I was in the US Army Map Service we printed the deviation from true North on all the maps so that the user could use a compass and find due North.
2006-08-23 02:35:06 · answer #3 · answered by bigjohn B 7 · 0⤊ 0⤋
This is a bit outside my realm of knowledge, but I'm just about inquisitive enough to wanna know everything. So.
You can try this link. I'm not sure it's what you're looking for but it may be on the right path.
http://www.ngdc.noaa.gov/IAGA/vmod/
You can actually download a working Geomagnetic Field Modeling program.
Links or even telephone numbers.
http://www.iugg.org/
try both. Good luck.
2006-08-23 02:55:23 · answer #4 · answered by theenormusnorm 2 · 0⤊ 0⤋