From space weather.com where they had a similar picture today - “Note the flared tops. That's what's unusual. Ordinary light pillars shoot straight into the sky with pointy tips. The V-shaped tops of these pillars are extremely rare.
The vast majority of light pillars are caused by ice crystals that look like tiny microscopic plates. However, ice crystals floating around the Rovaniemi airport were not little plates; instead, they were little pencils. Pencil-shaped ice crystals create the flare. To see the shape, common crystal plates must be absent. No one knows where they went! So there is an element of mystery, as well.”