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Re: LF: Re: Poor conditions

To: <[email protected]>
Subject: Re: LF: Re: Poor conditions
From: "Alan Melia" <[email protected]>
Date: Mon, 23 Mar 2015 23:31:56 -0000
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Hi Roelof yes though I am not sure how well authenticated. The return of Dst from the plunge after a ME impact is always logarithmic. My thoughts on this are that the ring current acts as a reservoir of charge which is exchanged with the atmosphere.. The mechanism of the interchange is diffusion, then this is concentration driven, so rate of the interchange is rather like a discharging capacitor (my analogy)
You are right in spotting the positive swing in Dst this almost always
occurs, there are of course positive ions and electrons in the plasma, and I
think the upward swing is due to the ions. I think if the IMF is in
the"wrong" direction there is little positive movement, and the plasma
"bounces off" the magnetosphere and does not reconnect. This is one of those
"non-events" were nothing dramatic happens. That is undoutedly over
simplified and a lot is my interpretation......which might be in error
:-)) There are difficulties using Kyoto for the Dst estimate because they
take a day or two to refine the corrections an weed out the false data from
the corps of magnetometers they use. Although the estimate from Colorado
University is indirect in that it is estimated from the data collected by
the ACE satellite I find that it is more reliable in real-time and has less
dramatic excursions that the ground-based magnetmeter data. The latter is
only declared reliable about 6 monthsafter the event which is no help for
real time prediction work. I did use it for about a year until I found the
Colorado site (Thanks o a nudge from John W1TAG). They do plot the Kyoto
data as well as the ACE based estimate. The mean Kyoto measure runs perhaps
20nT above the Colorado estimate.
----- Original Message ----- From: <[email protected]>
To: <[email protected]>
Sent: Monday, March 23, 2015 8:12 PM
Subject: Re: LF: Re: Poor conditions

Hello Alan,

Thank you for the information.

I keep an eye on the Kyoto Dst and on he 17th it peaked +45.
Such a peek often preceeds a major drop, however this one was very
fast and deep. After the minimum of -228, it rose almost as steep as
it dropped to about -90. After that the recovering is much slower
and at the same speed.

Is there an explanation for this?

Roelof, pa0rdt

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