What is Winterline (The second horizon)?

Winterline is a phenomenon when pseudo or second horizon gets visible due to hot air from the downwards gets trapped because of the cold air coming down from the snow capped mountains.
Winterline is not visible from every place, Himachal and Uttarakhand states of India have very good places to see winter lines, mostly greater altitude than 7000 ft.
This photograph is from the last winter.

Winterline as visible from Lokhandi, a small village at Uttarakhand state of India.