A planet is said to be rising, or ascending, when moving via the ascendant between the fourth and tenth cusps, i.e. in the eastern hemisphere of the chart. Some modern astrologers only consider a planet to be rising if actually placed in the first house, where its strength is accentuated because angular. [It's a moot point as to whether a planet in the mid-heaven should be described as "rising", or simply "elevated". Certainly it is angular and thus strengthened.