What is the ruling regarding someone who fondled his girlfriend over the phone during the daytime in Ramadan, leading to the emission of semen, and what expiation does that entail?

Telephoning one's wife is permissible, but if it arouses lust and causes the emission of semen, it invalidates the fast. Both husband and wife must make up for that day, according to the majority of scholars. The Maliki school, however, stipulates expiation (kaffarah) in addition to making up the fast. As for telephoning and fondling a woman who is not one's wife, it is originally forbidden (haram), and its prohibition becomes more severe in Ramadan. Both individuals must repent and make up for that day.