Here in Russia, we call these hats "shapka-ushanka" or just "ushanka". In English it will be something like "ears-hat". That's because we call these "sides" as "ushi" ("ears"): when they are turned down, hat is look like "something-with-ears" - "ears-hat".
Actually, this one on the photo is chienesse and not quite russian, but it's close to. Russian "ushanka" has some differences in style and it is even more warm If you want, I can send to you a couple of photos of me wearing "ushanka" in the winter forest Sometimes I travel on walking tours in winter (alone or with "comrades" ). Winter forest in night is great.