There is an existing question that has reference to mention of Svarbhanu in Rig Veda. But I am more interested in related stories - be it from brahmanas, ithasas or puranas. Specifically, what was his origin ? How did he become enemy of Surya dev? When did Indra strike him down and how did Sage Atri find and restore Surya dev
In Hinduism, Rahu is responsible for causing eclipses, and as far as I know, Swarbhanu is one of the various names of Rahu.
Quoting from the Rahu Kavacham, which is supposedly from Mahabharata's Drona Parva:
Katim may vikata pathu, ooru may sura poojitha,
Swarbhanuni januni pathu jange may pathu jadayaha., 5
Let my hip be protected by the funny one, Let my thighs be protected by he who is worshipped by devas, Let my knees be protected by him who makes the sun his own, Let my calves be protected by him who is sluggish.
Gulphou grahapathi pathu, padhou may bheeshanakruthi,
Sarvanyangani may pathu neela chandana bhooshana., 6
Let my ankle be protected by the lord of planets, Let my feet be protected by he who looks terrible, And let all my limbs be protected by him who wears blue sandal paste.
The Kavacham ends thus:
Ithi Sri Mahabharathe Drutharasthra jayantha samvade drona parvani rahu kavacham sampoornam,
Thus ends the armour of Rahu occurring in the middle of discussion between Drutharashtra and Jayantha which occurs in the chapter on Drona of the Mahabharatha epic.
In Rahu Stotram too, which is found in Skanda Purana, Swarbhanu is mentioned as one name of Rahu.
Rahur dhanavamanthri cha simhika chitha nandana,
Ardha kaya, sada krodhi, chandradhithya vimardhana., 1
Rahu, Minister of Rakshasa, one who makes Simhika happy, Half bodied one, one who is always angry, Tormentor who troubles Sun and Moon.
Roudhro rudhra priyo daithya swar bhanur, bhanur bheethidha,
Graha raja sudhapayee rakadhithyabhilashtaka., 2
Angry one, Devotee of Rudhra, Ogre, One who is near the Sun, one who terrifies the sun, King of planets, one who got nectar, One who desires the moon and the sun.
So, Swarbhanu is none other than Rahu, whose story is quite well known.
The Jyotisha text Horasara also mentions that Swarbhanu is one name of Rahu.
From Chapter 2 we have the following verse:
RAhustamoasuro-agushcha svarbhAnushcha vidhuntudhah |
Saimhikeshcha bhujango-ahishcha te samAh ||
Rahu is indicated as Tamas, Asura, Swarbhanu, Vidhuntuda, Pata, Sainhikeya, Bhujanga and Ahi. (40)
Next, quoting from the book "Essence of Brahmanda Purana":
Abodes of Planets:
Through out various Manvantaras, the Abodes of various Planets are fixed and permanent. They are named after each one of them like Soura Sthaana or the Abode of Surya, Sowmya Sthana (Abode of Chandra), Shukra Sthana, Brihaspati (Jaiva) Sthana, Lohita Sthana (Kuja), Shanaischara Sthana, Budha Sthana, Swarbhanu (Rahu) Sthana, and Jyotirgana or Nakshatra Sthanaas. In the current Vaivaswata Manvantara, the Planets are called ‘Vaitanikas’. Aditi’s son Vivaswanta is Surya; Dharma’s son Twishi the Vasu is called Chandra; belonging to Shukra Vamsha, the Rakshasa Guru Shukra is famed as Yajna Yaajaka for the Daanavaas; Angiras’s son Brihatteaja or Brihaspati is popular as Deva Guru; Twishi’s son Budha is also reckoned as a virtuous Graha; Sanjna and Surya’s son Shanaischara is in his abode too; Lohita or Kuja was born toVikesi Devi and Agni Deva; The Stars called Rikshas are known as the daughters; and Rahu the son of Devi Simhika also called Swarbhanu is the originator of troubles. The Abode of Surya is full of Agni and white where as Twishi or Chandra is full of water and white; Budha or Mercury who is Pancha Kirana or of Five Rays too is full of water and of dark colour; Shukra Sthaana is a Lotus again with water and has sixteen Rays; Kuja also is full of water but of blood red colour; Brihaspati has a big Place and watery in green colour with twelve rays; Saturn has eight rays of black colour and Jalamaya or full of water; and Rahu Sthaana is of dark colour and is the tormentor of Praanis or Beings. All the Nakshatras are ‘ jalamayas’ or full of water and of white colour glitterting with illumination thanks to Surya Deva and these Stars were as old as Kalpa and are shiny due to the interaction of Surya.’
We can also quote from the Vishnu Sahasranama found in Skanda Purana:
Divya drishtah Samadrishtih Deva Daanava vanchakah,
Kabandhah Ketukaari cha Swabhaanu –schandra taapanah/
Graha Raajo Grahi Graahah Sarvagraha vimochakah,
Daana maana japo homah Saanukuah Shubhagrahah/ ( 71-90)
Ketukari or Bhagavan was also the responsible to the Creation of Ketu who along with Devas in the queue in disguise for the distribution of Amrita but got beheaded by Vishnu as Mohini yet got restored to celestial Life since Ketu already enjoyed the drink of Amrita or deathlessness; Swarbhanu chandra taapnah or Bhagavan in reference to the incident of Rahu Ketu at the distribution of Amrita was obliged to let Chandra and Surya be troubled by Rahu Kethu although at the timings of Ecipses
Quoting from the astrological text Hora Ratnam:
107. Synonyms for Rahu & Ketu:
Rahu, Tama (darkness), Asura (demon), Agu, Swarbhanu, Vidhuntuda, Ghata, Saimhikeya (son of Simhika), Bhujanga (snake) and Bhujaga (also snake that creeps with shoulders) are Rahu’s names. Ketu is known by such other names as Sikhi (one who has reached the summit of knowledge), Ketu, Dhvaja (flag), Dhumra, Mrityu Putra and Anila (wind, rheumatism, paralysis).
So, there is ample evidence to prove that Swarbhanu and Rahu are not different. We can quote similarly from various other sources to prove the same conclusion.