Here is what Prashna Upanishad tells about Pitriyana [Southern course] and Devayana[Northern course]
संवत्सरो वै प्रजापतिस्तस्यत्यने दक्षिणं चोत्तरं च तद्येह वै तदिष्टापूर्ते कृतमित्युपासते ते चान्द्रमसमेव लोकमभिजयन्ते त एव पुनरावर्तन्ते तस्मादेत ऋषय प्रजाकामा दक्षिणं प्रतिपद्यन्ते एष ह वै रयिर्यः पितृयाणः ९
I-9: The year is verily the Lord of creatures. Of Him there are two Courses, the Southern[Pitriyana] and the Northern[Devayana]. As to that, those, who follow, in that way, the sacrifices and public good etc., that are products of action, conquer the very world of the moon. It is they who come back. (Since this is so), hence these seers of heaven, who are desirous of progeny, attain the Southern Course. That which is the Course of the Manes is verily food.
अथोत्तरेणा तपसा ब्रह्मचर्येण श्रद्धया विद्यात्मानमन्विष्यादित्यमभिजयन्ते एतद्वै प्राणानामायतनमेतदमृतमभयमेतत् परायणमेत्तस्मान्न पुनरावर्तन्त इत्येष निरोधस्तदेष श्लोक १०
I-10: Again, by searching for the Self through the control of the senses, brahmacharya, faith and meditation, they conquer the sun (by proceeding) along the Northern Course.[Devayana] This is the resort of all that lives; this is indestructible; this is fearless; this is the highest goal, for from this they do not come back. This is unrealisable (to the ignorant).