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(meteorobs) NLC-E-region
About a possible relationship between NLC and sporadic E-layers:
There is no direct relation. NLC is a neutral atmospheric phenomena, depending
on water vapor concentration at the mesospause, on the temperature there and on
dust grains beeing the nuclei for condensation.
Sporadic E is a plasma phenomena, because the neutral molecules and atoms
between 90 and 120 km are ionized by solar EUV radiation.
Surprisingly both phenomena occur at the same season. Sporadic E occurrance
peaks in the summer months, NLC occur exclusively in June, July and August.
It is probable that the occurrance of both is controled by wave activity in the
respective height range: gravity waves (fine structure) and planetary waves
(day-to-day variability).
I could say more about these things, but I am extremely busy these days
(PATHFINDER and others). I can come back to this topic in September.
Kristian Schlegel, MPI fuer Aeronomie, Katlenburg-Lindau, Germany