I have had interest (amateur) in aurora borealis for some time. At
my location, near Uppsala Sweden, I have witnessed some of the
strongest displays ever. At the same time, there are stories
circulating in the literature and media that Earth is losing its
magnetic field. The doomsday stories are that, perhaps like Mars,
this would lead to reduced protection of the atmosphere from
bombardment derived from solar activity, and at the current rate
of loss of magnetic field, lethal depletion of Earth's atmosphere
could occur in about a single millenium.

Seems pretty extreme! I wonder, do people who support this
doomsday scenaria also believe that solar activity is increasing,
and that this would enhance the rate of atmospheric depletion?
Do they have any proposals as to the normal frequency and amplitude
of variations over the course of many millenia for comparison?

Dominic-Luc Webb

"Dominic-Luc Webb" wrote in message
...
|
| I have had interest (amateur) in aurora borealis for some time. At
| my location, near Uppsala Sweden, I have witnessed some of the
| strongest displays ever. At the same time, there are stories
| circulating in the literature and media that Earth is losing its
| magnetic field. The doomsday stories are that, perhaps like Mars,
| this would lead to reduced protection of the atmosphere from
| bombardment derived from solar activity, and at the current rate
| of loss of magnetic field, lethal depletion of Earth's atmosphere
| could occur in about a single millenium.
|
| Seems pretty extreme! I wonder, do people who support this
| doomsday scenaria also believe that solar activity is increasing,
| and that this would enhance the rate of atmospheric depletion?
| Do they have any proposals as to the normal frequency and amplitude
| of variations over the course of many millenia for comparison?
|

There is evidence that the main (dipole) component of the earth's magnetic
field is losing strength and some people believe that a "reversal" will
occur within the next few thousand years.

This could indeed result in more dramatic aurora displays and confusion to
animals / birds which use the magnetic field for navigation.

The good news is that there have been tens, if not hundreds, of these
reversals in the earth's history and the planet is still teeming with life
and has plenty of atmosphere left.

The timescale is such that none of us here are likely to live to see the
critical stages of the reversal. We are just noticing the slow decrease in
magnetic field strength.
--
- Yokel -
oo oo
OOO OOO
OO 0 OO
) ( I ) (
) ( /\ ) (

"Yokel" now posts via a spam-trap account.
Replace my alias with stevejudd to reply.

On Tue, 6 Sep 2005, Yokel wrote:

"Dominic-Luc Webb" wrote in message
...
|
| I have had interest (amateur) in aurora borealis for some time. At
| my location, near Uppsala Sweden, I have witnessed some of the
| strongest displays ever. At the same time, there are stories
| circulating in the literature and media that Earth is losing its
| magnetic field. The doomsday stories are that, perhaps like Mars,
| this would lead to reduced protection of the atmosphere from
| bombardment derived from solar activity, and at the current rate
| of loss of magnetic field, lethal depletion of Earth's atmosphere
| could occur in about a single millenium.
|
| Seems pretty extreme! I wonder, do people who support this
| doomsday scenaria also believe that solar activity is increasing,
| and that this would enhance the rate of atmospheric depletion?
| Do they have any proposals as to the normal frequency and amplitude
| of variations over the course of many millenia for comparison?
|

There is evidence that the main (dipole) component of the earth's magnetic
field is losing strength and some people believe that a "reversal" will
occur within the next few thousand years.

This could indeed result in more dramatic aurora displays and confusion to
animals / birds which use the magnetic field for navigation.


Thanks for that response. It increased the S/N on this list (lot of
off topic garbage). Maybe you know a reference describing these
reversals and intensities over time? I presume you mean the aurora
will get weaker if anything until the reversal, or?

I am optimistic Earth will remain more than a few thousand more years,
assuming no human intervention to speed things up.

Dominic

"Dominic-Luc Webb" wrote in message
...
| On Tue, 6 Sep 2005, Yokel wrote:
|
| "Dominic-Luc Webb" wrote in message
| ...
| |
| | I have had interest (amateur) in aurora borealis for some time. At
| | my location, near Uppsala Sweden, I have witnessed some of the
| | strongest displays ever. At the same time, there are stories
| | circulating in the literature and media that Earth is losing its
| | magnetic field. The doomsday stories are that, perhaps like Mars,
| | this would lead to reduced protection of the atmosphere from
| | bombardment derived from solar activity, and at the current rate
| | of loss of magnetic field, lethal depletion of Earth's atmosphere
| | could occur in about a single millenium.
| |
| | Seems pretty extreme! I wonder, do people who support this
| | doomsday scenaria also believe that solar activity is increasing,
| | and that this would enhance the rate of atmospheric depletion?
| | Do they have any proposals as to the normal frequency and amplitude
| | of variations over the course of many millenia for comparison?
| |
|
| There is evidence that the main (dipole) component of the earth's
magnetic
| field is losing strength and some people believe that a "reversal" will
| occur within the next few thousand years.
|
| This could indeed result in more dramatic aurora displays and confusion
to
| animals / birds which use the magnetic field for navigation.
|
|
| Thanks for that response. It increased the S/N on this list (lot of
| off topic garbage). Maybe you know a reference describing these
| reversals and intensities over time? I presume you mean the aurora
| will get weaker if anything until the reversal, or?
|
| I am optimistic Earth will remain more than a few thousand more years,
| assuming no human intervention to speed things up.
|

Try a suitable combination of "Earth's Magnetic Field Reversal" in your
search engine of choice.

This used to be text-book stuff in the days when the "Internet" was
something being put together by a few university departments.

Alternatively, look under "Continental Drift". The sequence of reversals
left magnetic "stripes" in the sea-floor, produced by the rock taking the
local magenetic field as it cooled from magma and this field then being
"frozen in". It was finding these "stripes" and realising what they were
that enabled the spreading of the sea floors and deduction of the positions
of continents to be used to show the truth of the tectonic plate theory.

The magnetic field does not "die" during a reversal. The familiar "dipole"
field which we visualise as a big "bar magnet" in the earth fades away, but
some of its energy is transferred to other components which produce erratic
patterns of many magnetic poles. This energy is then taken back as the
dipole field re-appears but in the reverse direction and its strength is
then restored by whatever process (still not fully inderstood) generates the
field in the first place.

Aurorae should get stronger and more widespread as two strong magnetic poles
are replaced by a number of weaker ones much less effective at shielding the
upper atmosphere from solar blasts.
--
- Yokel -
oo oo
OOO OOO
OO 0 OO
) ( I ) (
) ( /\ ) (

"Yokel" now posts via a spam-trap account.
Replace my alias with stevejudd to reply.