Interessantes zu den Ankunftszeiten...

[Ulrich Rieth]

Hallo !

Cary Oler hat mal wieder ein paar Bemerkungen zu den Ankunftszeiten von sich gelassen.
im Prinzip ist es eine Wiederholung der Diskussion, die wir hier schon hatten. Aber ich kopier die Passagen trotzdem mal hier rein.
Gruß

Ulrich

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Name: Cary
Date: Sat, 20 Oct 2001 21:36:20 -0600
Subject: Re: Arrival times

Hi all. Just thought I'd interject a few things.

TSobiech, the arrival time is indeed for the late UTC day of 21 October or the early UTC day of 22 October. Our initial prediction
(which we are still holding as our primary prediction) was for around 03:00 UTC on 22 October (not 21 October as some have thought).

Ulrich, you're pretty much bang on. CME brightness is not necessarily a sign of energetics. Very strong CMEs do tend to be brighter, but
then they are often denser ejections of mass as well. Very dim CMEs can also be rather influential when they hit the Earth. So you can't
necessarily tell geoeffectiveness from CME brightness. We wish it were that simple.

When examining LASCO images/movies of coronal mass ejection events, everyone should keep in mind that each one has its own
'personality'. Some are bright or have wide cone angles where much of the ejected masss may be dispersed or spread out. Others may
be dim or have narrow cone angles where more of the ejected mass is concentrated in a smaller spatial region. There is reason to
believe (Ulrich alluded to some of them) that the first CME event had a narrower cone angle with a trajectory very much centered
toward the Earth. Just as it is difficult (if not impossible) to tell how fast a train is moving toward you while standing on the railroad tracks,
it is difficult to tell how fast an Earthward directed CME with a narrow cone angle is travelling toward the Earth. Type II shock velocity
measurements suggest the CME may have been travelling a fair bit faster than LASCO image analyses suggested (again, due to the
suspected narrower cone angle).

Thus far, it appears the disturbance is about a day away from impacting, which would ring true with predictions for late on 21 or early on
22 October (UTC time).

Time will tell...