I wasn't able to find much online about Sunna, even using the alternate name of "Sol." Wikipedia claims that Sol is the most common name for the personification of the Sun (http://en.wikipedia.org/wiki/Sol_(disambiguation)).
The following is taken from an online article titled "What Would the Druids Do at the Summer Solstice?" (http://www.adf.org/rituals/celtic/midsummer/wwtdd-summer-solstice.html) which I found very enlightening:
Many readily will point out that the Sun has not been considered male by all religions around the world and, even in the Western Branch of the Indo-European, we find examples such as the Norse at times addressing the Sun as a Goddess, "Sunna", the very word from which we get our word "Sun."
The Sun DESERVES our love and worship and we deserve to love and worship the Sun, without guilt. The Sun is without a doubt at least one half of our reason for existence on this beautiful planet, the other of course is the great system of Life on the Earth's surface we call Nature. It may seem natural for us to see them as a grand dyad: Mother Nature and Father Sun; but it's not altogether necessary. The choice is up to you... must we then muddy it up with "mortal" gender and familial issues?
At one point in our past, most of us, in a moment of rebellious insight threw-off the chains of our cultural conditioning and embraced things "witchy", "magical" and "Druidic" and found ourselves doing-so because of the beauty and truth and power we found in them. The resistance we broke-through in that moment was the web of falsehoods and negativity that society had spun around them. There is a similar agenda holding us back within our own subculture, a largely unspoken but ever-present agenda which would turn our face away from the sunrise...
So the sun, and therefore Sunna, should be embraced and loved and worshiped. I plan to do just that!
Thank You for the sunshine. Thank You for its warmth. Thank You for the rays which embrace me and that help the crops to grow. Thank You for You love.