Industrial application of nanosecond pulsed corona technology for air purification requires high volume, high power plasma reactors. Cylinder-wire type reactors require multiple cylinders or very long reactors to meet these demands. In this article, we focus on the characterization of a pulsed corona plasma in a long (4.5 m) plasma reactor. The reactor cylinder acts as a coaxial transmission line wherein high-voltage pulses propagate with close to the speed of light. Interactions between plasma generation and reflection behavior inside the reactor are expected and therefore investigated. A 4.5-m-long corona reactor is constructed and equipped with voltage and current sensors at multiple positions along the reactor length. A lumped element SPICE model is developed to simulate the reflection behavior. Strong reflections at the end of the reactor are observed for pulse rise times which are shorter than the transient time of the reactor. Plasma generation and energy distribution in the reactor, as well as impedance matching between source and reactor, are affected by these reflections. We investigate the role of the input voltage and rise time and analyze the electrical characterization, impedance characterization, and reactor efficiency.