As senior rabbi at Temple Judea, Aaronson will guide a congregation of more than 1,000 families.
Aaronson said the opportunity to lead the California congregation was too good to pass up, offering a wide range of opportunities and challenges. But he called the move "bittersweet."
"It's going to be difficult to leave friends," Aaronson said. "This has just been a very unique community that has a footprint far beyond its size. Because of the fact the Utah Jewish community is small, I've been able to really do a lot of things that in a larger community I wouldn't be able to do."
Joy Erickson, Har Shalom director of membership and volunteer outreach, said the congregation is sad to see him go but thrilled for his new chance.
"It's a wonderful, wonderful opportunity for him," Erickson said. "He's my friend and mentor, and I'm going to miss him."
Douglas Goldsmith, Har Shalom board president, said much has changed during the time Aaronson has led the congregation. Not only has the congregation swelled in size, but it also includes a number of interfaith families, thanks to an accepting and inclusive atmosphere, Goldsmith said.
"A tremendous number of interfaith families," Goldsmith said, "are now identified with the Jewish religion very much as a result of Aaronson's work."
Goldsmith said the Har Shalom board will meet in January to begin the process of selecting a new rabbi.