Whistler mode waves for ring distribution with A.C. electric field in inner magnetosphere of Saturn
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Whistler mode waves can propagate upstream without collision impact. They are generated in these areas of vibration. They are known to play a crucial role in thermodynamics and electron acceleration. Sometimes, in some cases, they are seen as waves that strike the wavefront. Mercury, Earth, Venus and Saturn are the planets where whistlers have been recorded in the upstream regions. They are right handed waves and can be left-hand polarized in the frame of spacecraft due to the strong negative Doppler shift. The weaker Doppler shift owes to the large angle between magnetic field vectors at 10 AU (Astronomical unit) and the solar wind velocity. These waves propagate with an angle between 10 to 60 degrees to background magnetic field. In the present paper, we took an advantage of Cassini present in the Saturnian magnetosphere to explore the whistler mode wave’s importance. A dispersion relation for obliquely as well as for whistler waves propagating perpendicular to the magnetic field, has been applied to Saturnian magnetosphere. Using the observations made by Voyager and Cassini, growth rate has been determined for non-relativistic plasma. Whistler waves are excited by temperature anisotropy, where the vertical temperature is higher than the parallel temperature. The effect of electron density, temperature anisotropy, energy density with some other parameters on the growth of whistler mode emission is studied. The result is found to be in good agreement with observations. Whistler mode wave interaction with particles basically emphasizes on the increase (decrease) in the energy of resonant particles and this variation is related to the transfer of energy to (from) other resonant particle group where the wave is the mediator of the energization process. Due to the non-monotonic nature of the ring distribution, at vertical velocities, the magnification produced by this instability is larger than the typical bi-Maxwellian anisotropy distribution because the wave can maintain resonance over a longer portion of its orbit.
KeywordsWhistler mode waves Magnetosphere of Saturn Ring distribution function
The authors are grateful to the Chairman, Indian Space Research Organization (ISRO), Director and members of PLANEX program, ISRO, for the financial support. We are thankful to Dr. Ashok K. Chauhan (Founder President, Amity University), Dr. Atul Chauhan (President, Amity University) and Dr. Balvinder Shukla (Vice Chancellor, Amity University) for their immense encouragement. We also express our gratitude to the reviewers for their expert comments for the manuscript.
- Barkhausen, H.: Zwei mit Hilfe der neuen Verstarker entdeckte Erscheinungen. Phys. Z. 20, 401–403 (1919) Google Scholar
- Cowley, S.W.H., Wright, D.M., Bunce, E.J., Carter, A.C., Dougherty, M.K., Giampieri, G., Nichols, J.D., Robinson, T.R.: Cassini observations of planetary-period magnetic field oscillations in Saturn’s magnetosphere: Doppler shifts and phase motion. Geophys. Res. Lett. 33(7), L07104 (2006) ADSCrossRefGoogle Scholar
- Davidson, R.C.: Kinetic waves and instabilities in a uniform plasma. In: Handbook of Plasma (1983) Google Scholar
- Gabrel, V., Echim, M.: Transport and entry of plasma clouds/jets across transverse magnetic discontinuities: Three-dimensional electromagnetic particle-in-cell simulations. J. Geophys. Res. 121 (2016). https://doi.org/10.1002/2015JA021973
- Gurnett, D.A., Kurth, W.S., Kirchner, D.L., Hospodarsky, G.B., Averkamp, T.F., Zarka, P., Lecacheux, A., Manning, R., Roux, A., Canu, P., Cornilleau-Wehrlin, N., Galopeau, P., Meyer, A., Bostrom, R., Gustafsson, G., Wahlund, J.-E., Aahlen, L., Rucker, H.O., Ladreiter, H.P., Macher, W., Woolliscroft, L.J.C., Alleyne, H., Kaiser, M.L., Desch, M.D., Farrell, W.M., Harvey, C.C., Louarn, P., Kellogg, P.J., Goetz, K., Pedersen, A.: The Cassini radio science investigation. Space Sci. Rev. 114, 395–463 (2004) ADSCrossRefGoogle Scholar
- Hayakawa, M., Lefeuvre, F., Rauch, J.L.: On the system of Aureol-3 satellite direction finding for ionospheric and magnetospheric ELF waves. Trans. Inst. Electr. Inform. Comm. Eng. E 73, 942–951 (1990) Google Scholar
- Helliwell, R.A.: Whistlers and Related Ionospheric Phenomena. Stanford University Press, Stanford (1965) Google Scholar
- Potter, R.K.: Analysis of audio-frequency atmospherics. Proc. Inst. Radio Eng. 39, 1067 (1951) Google Scholar
- Sonwalkar, V.S., Inan, U.S., Bell, T.F., Helliwell, R.A., Chmyrev, V.M., Sobolev, Y.P., Ovcharenko, O.Y., Selegej, V.: Simultaneous observations of VLF ground transmitter signals on the DE 1 and COSMOS 1809 satellites: detection of a magnetospheric caustic and a duct. J. Geophys. Res. 99, 17511–17522 (1994) ADSCrossRefGoogle Scholar