I have seen this twice now, once in Switzerland, where the site was small, but many individuals were on the wing, and once in Northern Norway. It is a very small Fritillary, but extremely attractive. The female is top left, the male below her, and the underside shot was of a very alert territorial male.
Note the chevrons > < on the forewings, a distinctive feature.
Definitely a challenge for butterfly photography.
The Arctic ones are a little larger...