Talk: Northern Lights

In article <3f2loq$1j...@gagme.wwa.com> kei...@badlands.NoDak.edu (Kirk the Eisenbeis) writes:
>
>Curt Rice (ric...@isl.uit.no) wrote:
>
>: In article <3ehvm2$sp...@gagme.wwa.com>, jit...@erehwon.caltech.edu (Mike
>: Jittlov) wrote:
>
>
>: [much deleted]
>: > Crosspost/imported from:
>: >
>: > rec.arts.ascii (moderated) #3503 (6 + 19 more)
>: > From: ric...@rs4.tcs.tulane.edu (Dave Rice)
>: > [1] Line: Aurora borealis/Northern Lights
>: > Date: Fri Dec 30 20:21:39 PST 1994
>: > Organization: Tulane University, New Orleans, LA
>: > > A few comments on aurora and on the figure:
>: >
>: > Aurora borealis and its southern counterpart, aurora australis, are phenomena
>: > that occur only in the high latitudes, about 65 degrees North or South.
>
>: This interesting report is reinforced with a great display on the topic
>: currently at Tromsoe Museum.  A couple of comments/questions:
>
>: I live in Tromsoe during the school year and northern Minnesota during the
>: summers.  We routinely see northern lights both places.  No surprise in
>: Tromsoe, of course, but Minnesota doesn't fulfill either the latitude or
>: season requirements.
>
>I agree--the whole article seemed to be well-informed, but I disagree
>with the 65 degrees requirement.  I'm only around 48-49 and they aren't
>too uncommon (not like every week, but maybe a few times every couple
>months?)
>

Rermber that the 65 degrees is geomagnetic latitude and not
geographic.  The 'magnet inside the earth' is, unfortunately, not
lined up with the earth's rotational axis.

The auroral region is defined as the region from 60 to 75 deg dipole latitude
(International Auroral Atlas, 1963).

You must keep in mind that the whole phenomenon is an extremely
dynamic one, so aurora in Mexico (or at your location) isn't _that_ sensational.
Sometimes the auroral zone has to widen considerably to be able to
digest all the energy that in inbound... and then of course it is seen
at lower latitudes.

The auroral zone is more like an oval, and the earth is rotating
underneath (not _with_) this oval, so there is a dependency on local
as well as universal time.  In addition, there is a 11 yr cycle, a semi-annual
variation (maxima at equinoxes), 27-30 day periodicities and so on.
Some say there is a longitudinal variation too! (I think this has
even been confirmed and explained)

Some usenet sci. newsgroups have Auroral Alert postings in case
you want advance warning there might be aurora tonight.

T.
--
Trond Steinar Trondsen                           VE6NOR/LA1OEA
___________________________________________ o ________________________________
                                           /~> | University of Calgary/Physics
E-mail: tro...@phys.ucalgary.ca         o....<\ | Institute  for Space Research

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