To Start with, Indra can take on the role of both Surya and Chandra. Such is his magnificence.
Mahabharat 515(218)
Indra grants beings strength, energy, offspring and happiness. When he is satisfied, the lord of the gods grants everyone their shares. He withdraws it from those who perform evil deeds and grants it to those who perform good ones. The destroyer of Bala assigns beings to their tasks. He acts as the sun when there is no sun, and as the moon when there is no moon. He becomes the fire, the wind, the earth and the water and their origins. These are Indra’s tasks and Indra
Rig Veda 1.32.4 - According to the Rig Ved, the sun, dawn and skies had fallen in the battle with Vritra. Indra gave them life.
yad indrāhan prathamajām ahīnām ān māyinām amināḥ prota māyāḥ | āt sūryaṃ janayan dyām uṣāsaṃ tādītnā śatruṃ na kilā vivitse ||
4 When, Indra, thou hadst slain the dragon's firstborn, and overcome the charms of the enchanters,
Then, giving life to Sun and Dawn and Heaven, thou foundest not one foe to stand against thee.
Rig Veda 1.51.4 - Indra made the sun visible after destroying Vritra.
tvam apām apidhānāvṛṇor apādhārayaḥ parvate dānumad vasu | vṛtraṃ yad indra śavasāvadhīr ahim ād it sūryaṃ divy ārohayo dṛśe ||
You have opened the receptacle of the waters; you have detained in the mountain the treasure of the malignant; when you had slain Vṛtra, the destryer, you made the sun visible in the sky.
Hara Hara Mahadeva 🙏🏻📿🪔🔱
Namo Narayana 🙏🏻🪷🪔🦅