The pasuk states (Tehillim 44:6): "Raise up Elokim with blowing ('teruah')." The Chozeh of Lublin zy"a (quoted in Lechem Shlomo, Ois 5) explains that the word "teruah" refers to "rayus" (brotherliness).The pasuk is saying that through rayus on Rosh Hashanah, when everyone blesses all of his friends from the heart to have a good year, Hashem gets up from his chair of strict judgment and sits down on His chair of mercy. The name "Elokim" refers to the middas hadin (the Divine attribute of strict judgment), and the pasuk is saying that through the rayus shown when everyone sincerely blesses each other, He rises from this middah and switches to the Divine attribute of mercy.

This article explains how showing brotherliness (rayus) on Rosh Hashanah can annul strict judgment. It details how Hashem switches from the attribute of strict 

Annulling Midas Hadin

Collected Thoughts on the Weekly Parshah From Rabbi Meir Isamar Rosenbaum shlita