# Physical reason for Helium-hole?

I just found a "Helium-hole" from atmospheric data provided here. I was actually looking for this, and the first search was immediately succesful, a hole was found from;
Time: 05.01.2002, 05:00 UTC
Place: 68 Latitude, 0 Longitude on 112-138 km height,
It's is shown in the picture below. As the picture shows the derivate, thus below 1 the amount is decreasing. The absolute amount was -25.7% less at 122 km height than the peak above at 139 km. The absolute amounts were $3.294x10^{-07}g/cm^3$ at 122 km height and, $4.434x10^{-07}g/cm^3$ at 139 km height.

As Helium is chemically unreactive under all normal conditions. And the temperature was $245 K ... 629 K$, and pressure $6.7x10^{-4}Pa...4.7x10^{-3}Pa$, which I consider "normal", as this vacuum is merely a "medium vacuum".

Thus there must be some physical reason for this, which I am just not aware of?

This question is related; Why In Thermosphere is He and O divided as measured? Edit; It seems that the this is not actaully a hole. The picture below shows how the amount of Helium is actually constantly higher above 140 km height. • NASA should be all capitalized because that's how they write it, rather than following tabloid papers. Jan 10, 2017 at 19:27
• No answer? Ok, If this is just another "We do not know"-thing for "Standard Model"; en.wikipedia.org/wiki/Standard_Model#Challenges Then, such an answer will be also be accepted and awarded. Jan 21, 2017 at 5:28