What is meant by "Shuruq" in determining prayer times: Is it sunrise, or the time of the Shuruq prayer?

The "Shuruq" (sunrise) according to jurists is the beginning of the sun's ascent. What is meant by it is the legal sunrise, which is the emergence of the first edge of the sun. As for the calendrical "Shuruq," it is the sunrise of the sun's center. Linguistically, "Shuruq" refers to the sun's rising from the east. The time for the "Salat al-Shuruq" (sunrise prayer) is when the sun has risen to the height of a spear, which is when the prohibition against supererogatory prayers ends.