The positive column is due to \(a_{\psi}\gt a_{\psi\,ne}\) positive particles
The Crookes' Dark Space is due to the time needed by the newly ejected \(a_{\psi\,c}\) to attain \(v_{boom}\) speed of the gas concealed. The glow beyond this dark space is due to discharge caused by the negative particles at \(v_{boom}\). More negative particles are generated during discharge. When the particles has speed beyond \(v_{boom}\) discharge stops.
At the same time \(a_{\psi\,c}\) coalesce into bigger particles.
The Faraday Dark Space is due to \(a_{\psi\,ne}\) not accelerated by any electric field and race through with a constant velocity. Their speed is higher than \(v_{boom}\) and does not cause discharge.
At the same time \(a_{\psi\,ne}\) coalesce into bigger particles.
Beyond Faraday Dark Space, \(a_{\psi}\gt a_{\psi\,ne}\), the particles are positive and is retarded by the positive anode (and the negative cathode). When their speeds reduce to \(v_{boom}\), they cause the gas to discharge (red region). Below \(v_{boom}\) speed discharge stops and a dark striation develops. This is just like the Faraday Dark Space but it developed under a positive field and is much shorter.
\(a_{\psi\,c}\) particles generated during the last discharge accelerate under the positive field, also cause discharge when they attain \(v_{boom}\) speed (bright region within the red region). But discharge stops when the particles are beyond \(v_{boom}\) speed. A dark striation develops, and \(a_{\psi\,c}\) particles ejected during the last discharge coalesce into positive particles, which are decelerated by electric field in the tube. And another discharge occurs at the end of the dark furrow when the positive particles have slowed to \(v_{boom}\) speed.
First discharge in the positive column (middle left in the diagram above) is due to positive particles. Beyond this bright strip, the positive particle are at speed lower than \(v_{boom}\) and does not cause the concealed gas to discharge. Negative \(a_{\psi\,c}\) particles generated during the discharge are the cause of subsequent discharges. These negative particles also coalesce with the positive particles and form bigger positive particles. For this reason their number reduces, and the subsequent discharges fade gradually, til they reach the anode. The positive particles are reversed near the anode and travels back to the cathode. On their way, they cause discharge when their speed reaches \(v_{boom}\) in the reverse direction (red region). Before attaining \(v_{boom}\) speed, a dark region occurs just before the anode.
Some negative particles will collide with the anode at high speed and causes it to glow (bright/blue region). In the same manner, some positive charge reaches the cathode and cause that to glow (red color). Since positive particles are the result of negative particles coalescence, they reach the cathode later and the glow at the cathode occurs later than the glow at the anode, as the discharge tube lights up from the cathode side.
The negative glow can be extended by reducing the voltage at the anode. The Faraday Dark Space correspondingly reduces, as the negative particle takes longer to go beyond \(v_{boom}\). The glow at the cathode, attributed to positive particles is also reduced as the number of positive particles in the tube is reduced. The tube lights up with one color
Positive particles exist as the result of coalesce without the need for ionization of the low pressure gas.
If discharge is due to one type of particles, then there should be only one color.
