Swedish Institute of Space Physics, IRF
The Ionosphere II
Chapman layer, recombinations and F1/F2
Create a neutral atmosphere, ionize it from above, consider recombinations,
look at the stationary electron density and sound it.
The Ionosphere is a plasma, which is defined from below;
by the neutral gas under gravity, and from above; by the light from the sun.
The light from the sun produces charged particles (electrosn and ions)
from the neutral gas.
The created electrons will be the dynamic particles interacting with radiowaves in our Ionosphere and the
created ions will make up the nessecary positive background. A plasma is neutral.
The ions together with neutral particles will catch electrons and balance the electron production
by the sunlight; the plasma
will be in a quasi equlibrium.
1. Create an atmosphere from a diffusion model. The density at a selected point
has to give a preasure wich can "hold" the atmosphere above. The density at a certain height is
proportional to the preasure at that height and if we move the point a little bit higher up the
preasure will decrease so it exactly balance the little bit less atmosphere
which is then above; it will be an exponential law charactrized by a scale height
which defines the mass distribution in height . The scale height depends
on the molekyle mass and the temperature.
At the ground the scale height is about 8 km; we can consider the
atmosphere there as consisting of only one type "mean molekyle". Higher up we have
to consider each molekule type for it self and get molekylemass dependent
scaleheights (~T(temperature)/M(molekule mass)).
2. Create ionosation light from the sun and let it produce electrons from atoms,
which distribution is defined by the atmosphere we created above. The electron production
is measured in electron per unit volume and per seconds. The number of electron
will steadily increase.
3. Start the recombination processes so we can get a quasi equlibrium.
There are two types working together in sequence; one is direct proportional (alpha) to the square of the electron
density and the other is only proportional to the elctron density. If one is weaker than the other it will be most
important.
The second one has a recombination coefficient dependent on height. That
dependens will be modeled by an uppwards decreasing exponetial, beta, with
a scale height, hBeta.
4. Play with the different parameters. You should be able to get only one peak
in the electron distribution and only se F2 and you should be able to
get two peaks and see both F1 and F2.
5. Do sounding of your ionosphere and figure out how a distribution should
look like to generate an ionogram with only one peak or how it should
look like to generate an ionogram with two peaks.
6. Do sounding with an ionosphere with a magnetic field.
You will find splitting of the traces which will be of three types O, X and Z.
7. Put in an E-layer around 100 km and sound an almost compleat ionosphere; you will get
an ionogram very similar to a real one.