Sorry, I forgot something else, these variables would be well defined ?:
Thanks
La = Quantity[3 x 10^10, 1/"Centimeters"^2 * "Seconds"];
\[Sigma] = Quantity[2.02 x 10^-18, 1/"Centimeters"^2]^ ;
nNO = Quantity[1 x 10^8, 1/"Centimeters"^3];
deltaz = Quantity[900, "Kilometers"];
H = Quantity[10, "Kilometers"];
k = Quantity[3.5 x 10^-7, 1/"Centimeters"^3];
ne = Quantity[ 5.23 x 10^5, 1/"Centimeters"^3];
ni = Quantity [5.09 x 10^5, 1/"Centimeters"^3];