1. Whistler Waves and Related Magnetospheric Phenomena
Denys Piddyachiy
Space, Telecommunications and Radioscience Laboratory
Stanford University, Stanford, CA
13 February 2007
PHYS 312 Basic Plasma Physics

2. Outline What is whistler? Examples
Mechanism of whistler waves formation
Whistler propagation in magnetosphere:
ducted whistlers
magnetospherically reflected whistlers
Interaction of whistler waves with energetic particles from Earth’s radiation belts
References

3. Whistler! What is this!?
From Merriam-Webster
whis·tler
a : any of various birds; especially : any of numerous oscine birds (especially genus Pachycephala) found chiefly in Australia and South Pacific islands and having a whistling call
b : a large marmot (Marmota caligata) of northwestern North America having a shrill alarm call
c : a broken-winded horse
d : a very-low-frequency radio signal that is generated by lightning discharge, travels along the earth's magnetic-field lines, and produces a sound resembling a whistle of descending pitch in radio receivers
Example of a whistler recorded at Palmer Station, Antarctica

4. Just another example of whistlers
f, kHz

5. Region of interest (filled with plasma)

6. Region of interest (filled with plasma)

7. Lightning-generated signal
Very good conductors in ELF/VLF range (300 Hz - 30kHz)

8. Whistler wave propagation in the magnetosphere

9. Multi-hop whistlers (Palmer Station, Antarctica)

10. Multi-hop whistlers (Palmer Station, Antarctica)

11. First order approximation of whistler wave propagation
Refractive index or dispersion relation:
Group velocity:
Group delay:

12. Whistlers aboard a satellite

13. Magnetospherically reflected (MR) whistlers

14. Magnetospherically reflected vs. ducted whistlers
Hey, dude, what is going on here? I am a physicist. I want an explanation.

15. Theoretical background
Ray tracing:
Refractive index:
use B field and electron density models

16. Refractive index surfaces
Fig. Refractive index surface indicating the resonance cone angle θres. Expanded section shows the refractive index at an angle θ with associated ray direction.

17. Modeling of MR whistlers

18. Earth’s radiation belts

19. Lightning (whistler) induced electron precipitation
Basic physics of Lightning-induced Electron Precipitation (LEP):
1) Lightning discharges produce intense electromagnetic radiation in very low frequency (VLF) range.
2) The VLF waves enter into the magnetosphere where they propagate almost along B-field lines to a region near the magnetic equator.
3) In the equatorial region VLF waves can effectively interact with energetic electrons from the radiation belts which leads to the scattering of electrons, i.e. changing of their pitch angles distribution if this condition is satisfied:
ωCe = ω – k║ v║
4) The change of the pitch angles leads to lowering of electrons reflection points in their bounce motion between conjugate ionospheres and as a consequence to their precipitation into the atmosphere.

20. Lightning-induced precipitation detection aboard low earth orbit satellite DEMETER

21. Adiabatic motion of electrons in radiation belts

22. Mechanism of electron precipitation by whistler waves

23. References
Helliwell, R.A., Whistlers and related ionospheric phenomena, Stanford University Press, Stanford, Calif., 1965.
Kivelson, M.G., and C.T. Russel, Introduction to spacephysics, Cambridge University Press, 1995.
Spasojevic, M., Global Dynamics of the Earth's Plasmasphere, Stanford Univ., PhD thesis, 2003.
Bortnik, J., Precipitation of Radiation Belt Electrons by Lightning-Generated Magnetospherically Reflecting Whistler Waves, Stanford Univ., PhD thesis, 2004.
Burgess, W. C., Lightning-Induced Coupling of the Radiation Belts to Geomagnetically Conjugate Ionospheric Regions, Stanford Univ., PhD thesis, 1993.
Carpenter, D.L., Remote sensing the Earth’s plasmasphere, Rad. Sci. Bull, 2004.
Inan, U. S., D. Piddyachiy, W. B. Peter, J. A. Savaud, M. Parrot, DEMETER Satellite observations of lightning-induced electron precipitation bursts, Geophysical Research Letters (under review), 2007.
PhD theses and other related information could be found at