PSN-L Email List Message

Subject: Re: Passing solar flare geomagnetic shock wave?
From: meredith lamb mlamb1@..........
Date: Sat, 10 Jun 2000 13:33:37 -0700

CapAAVSO@....... wrote:

> In a message dated 6/10/00 12:26:39 AM Eastern Daylight Time,
> mlamb1@.......... writes:
> << Thanks Chris,
>  I checked right away, and think I have to withdraw any
>  geo-magnetic conclusions; there just isn't any realistic match
>  comparison.  Nice of you to forward the web sites to explore,
>  and answer the question.
>  Take care,
>  Meredith Lamb >>
> ------------------------------------------------------------------------------
> -------------
> Hi Meredith,
>     That big pulse you recorded on 8 June was REAL despite your not being
> able to find it on those high-latitude European magnetic station's
> recordings. Here's how Jim Mandaville, an amateur in Tuscan, AZ  described
> it: "It hit my magnetometer around 1100 UTC Thursday.  The positive jump was
> so abrupt and strong that when I saw it in the morning I thought  (1) my
> electronics had gone berserk or (2) a prowler had come and parked his getaway
> car beside my house!  But when I checked the USGS Tucson magnetogram, it was
> identical.  This unusual storm remained strongly
> positive for several hours, then fell back into the negative region (but
> not strongly so), then slowly recovered through the day.  I got a good
> recording of it all.
>     Here's how Alex McWilliams saw it at his amateur magnetic observatory in
> Minnesota: "A VERY unusual spike happened at close to 1230 UTC  when the pen
> shot up very rapidly a very large amount and then recovered to original level
> - all in a matter of perhaps less than a minute.  I do not recall
> moving anything in the house at that time."
>     So you see, Meredith, your recording was no an artifact after all. It was
> an accurate recording of a real event. By the way, What is a diamagnetic
> horizontal seismograph and why does it record magnetic storms in addition to
> earthquakes?

A diamagnetic seismometer, is for all purposes, simply a levitated
neodymium magnet in a diamagnetic graphite "sandwich" (magnetically
repelling), with a overhead ferrite magnet for vertical adjustment. 
The magnet is balanced between the overhead magnet and the earths
gravity. Naturally, being a magnet its not desireable as a seismometer
"mass", especially with no present magnetic shielding (yet).  Any 
magnetic environmental variations will have an effect on it and the
output.  The levitated magnet acts like a (non-physically attached)
hanging pendulum from the magnetic centering influence of the overhead
magnet.  It hasn't been too sensitive to seismic P-S waves unless the
quake is larger or relatively nearby of sufficient magntitude.  I'am
hoping permalloy shielding will alleviate some of the magnetic
influences, and allow better views of seismic variations....but I'am
not to sure it will be any better.  It is simply a toy at the present.  

> Best regards,
> Cap

Hi Cap,

Some more web browsing/searching seemed to have come up with
a bull's eye for the diamagnetic seismometer here.  A USGS geomagnetic
Boulder (BOU) geomagnetic plot on their horizontal showed a big and
rapid (110 nt) change at the same time (+ or - 30 seconds) as shown on
my graph recording.  Boulder is closest at only ~ 30 miles away.  Big
difference in instrumentation here of course, as the seismometer is over
damped, and the magnetometer uses vastly different electronics. 
Interesting, as it shows a influence of geomagnetic changes; but perhaps
only of the big and rapid variety of such.  The USGS web site is at:

I think the site only shows the BOU plots for 7 days, and then is
no longer available on the web.  The "H", or horizontal plot is the
logical comparison to the diamagnetic seismometer.

Per your message above, it seems that the spike is like a storm
hitting areas at different times.  Here it hit at 9:10 UTC.

Have to admit strongly I'am a fish out of water with this
geomagnetic stuff.  Thanks to Cap, Chris Chapman and Edward
Cranswick of USGS, for their assistances with this topic!

I've since re-done the web site "show and tell" on this 
geomagnetic disturbance.  See:

Thanks, Meredith Lamb


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Larry Cochrane <cochrane@..............>