Topband: 160 spotlight effect

[Larry]

All:
First off, the effort made by the recent Baker Island DXpedition is
greatly appreciated.  Those who spent their time and effort to make this
happen deserve thanks and praise.  Thank you, one and all, for a great
DXpedition!

Now on to the subject of this post, something mentioned in the
discussion about the recent Baker Island DXpedition, _*the 160 spotlight
effect.*_ (With my modest station using wire antennas, I was able to
work them on 20 meters, and hear but not work them on other bands.)_**_

I have noted this phenomenon on a number of occasions over the last 4
years, when I have been on 160, but have been the beneficiary only once
that I recall, for a relatively short period one night.  Does anyone
have a concise explanation of the mechanism behind this?
The one night I enjoyed being "in the spotlight" I put 12 new DX
contacts in my 160 log, which thrilled me, but I remain curious about
how this happens.  I've heard some bits of differing theories, but still
don't have a complete mental picture of the mechanism involved.

Can anyone on Topband share their thoughts on this, please?

Sincerely, Larry Wright W8ANT