Hi Jay, yes I think John has it about right. I look at it this way.....you
are trying to estimate the values of a "current" flowing round the equator
in the Van Allen belt. This generates a field that you can detect at the
Equator and less so further away from the equator, with a sensitive magnetic
field measuring device (Magetometer) The magnitude of the field due to the
ring current is about 0.1% of the static geomagnetic field. Unfortunately
the magnetometer will also respond to any distortions in the static field.
So the "change in shape" of the magnetoshere caused by the sudden increase
in pressure of the Solar-wind / CME shock front will cause a transient
change. It is not until the electrons and ions have "passed by" Earth and
some have been collected in the "tail" that these are "sucked back" and
enter the ring current. Things move very quickly, but the "transient"
changes can be misleading. I always regard the most reliable values as those
when the Kp has recovered to low values. The transient positive swings DO
indicate an event....I expect that in the next 3 hour period you will
probably see NOAA plot a Kp=4 or even 5 and then the Dst will plunge down to
the -60s again. It will be interesting to see how quickly this affects
Steve's plot of DCF39. His path is quite close to the auroral circle, so
there may be some depression in the later part of the night. If NOAAs
appreciation of the size of the coronal hole is right this should not be a
very serious event, in their terms a minor storm (Kp<6). But I guess it will
"top-up" the ring current again and slow the return to really quiet
conditions.......which may lead to worse propagation (!!) or at least "not
the best levels"
Fascinating stuff this ionoshere !!
Cheers dde Alan G3NYK
----- Original Message -----
From: "Jay Rusgrove" <[email protected]>
To: <[email protected]>
Sent: 15 March 2005 18:22
Subject: LF: DST
Just happened to notice...Kyoto "real time" DST showing +14 at the
moment...will be interesting to see where it "settles in".