Model of ionosphere heating and VLFELF emission Heating
- Slides: 12
Model of ionosphere heating and VLF/ELF emission
Heating model § Heating by HF field is modelled by solving kinetic equation for electron distribution function, implemented in MATLAB § Kinetic model includes: § § § HF frequency and geomagnetic field Elastic collisions Inelastic and superelastic collisions Ionization/attachment processes The amplitude of HF field can slowly vary in time (VLF/ELF modulation) § The propagation of the wave includes changes of the ionosphere HF conductivity due to the wave itself (selfabsorption)
Results 1: electron distribution function § Ebr is an electrical breakdown field, which is proportional to frequency and inversely proportional to density. § The electron distributions are similar for same values of h=w/n
Results 2: Time-dependent (modulated) calculations § Square-modulated wave § Electron distribution f(E) is calculated at each moment of time § Conductivity, effective temperature, loss rates and other quantities are calculated from f(E) § Shown here, as an example, is the Pedersen conductivity changing with time
VLF/ELF emission and propagation model § Uses mode theory to solve Maxwell’s equations in stratified medium, implemented in MATLAB § Capabilities: § Full wave 3 D solution of both whistler waves launched into ionosphere and VLF waves launched into Earth-ionosphere waveguide § Magnetized plasma with arbitrary direction of geomagnetic field § Arbitrary configuration of harmonically varying currents § Both ionosphere and Earth-ionosphere waveguide § Stable against the “swamping” instability by evanescent waves § Runs much faster than FDFD and FDTD models: § Cell size can be larger than the wavelength § Vertical cell size can be variable § Can be extended to satellite altitudes
Example: application to HF heating § Modulation frequency=1875 Hz § Emission is caused by the change in electrojet current caused by HF heating § The current structure is shown. It has a horizontal pancake shape § We use our method to find E and B field § Size of the calculation domain: § horizontal: 1280 km (in 2 directions) § vertical 300 km
Results 1 § Execution of the MATLAB script for a 3 D calculation in a 128 x 85 mesh took ~45 min on a desktop computer (4 GB Ram, 2 x 2. 8 GHz Xeon) § Sz is the vertical component of the Poynting vector § Because of the tilted B field, the upward flow of energy leaves the plane of the picture § The beam stays narrow due to a large size of the emitting region
Results 2 § Sz is calculated at 120 km and 300 km. The beam changes its shape, but insignificantly due to a large size of the emitting region (small perpendicular k-vector)
Results 3 § The observed field on the ground is due to both near field and propagating Earth-ionosphere waveguide modes.
Results 4: whistler wave structure § Even though the vertical mesh is coarser than the wavelength, the fields at intermediate points can be also calculated
Results 5: VLF mode structure (Ez field) § The Earth-ionospher waveguide mode can be seen in this plot below ~ 75 km
Results 6: Field at 300 km § The VLF mode structure is preserved, although the largest field is in the central “funnel”
- Difference between induction heating and dielectric heating
- Ionosphere height
- Ionosphere
- Astronomy
- Jdiss
- Ionosphere
- Ionosphere
- Stratosphere height
- Vertical division of atmosphere
- Ionosphere
- Atomic emission spectra and the quantum mechanical model
- Atomic emission spectra and the quantum mechanical model
- Difference between absorption and emission spectrum