Is it permissible to fast the day of Ashura alone with the intention of making up a missed fast (qada') if fasting the following day is not possible due to menstruation?

Fasting the day of Ashura alone is permissible because there is no prohibition against fasting it individually. Rather, what has been reported indicates the desirability of fasting the ninth with it, or the ninth and the eleventh. The Prophet, peace and blessings be upon him, fasted it and commanded its fasting. So, if there is a legitimate excuse preventing the fasting of other days, there is no sin in fasting the tenth alone.