Physics
Scientific paper
Dec 2009
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2009agufmsm53a1350g&link_type=abstract
American Geophysical Union, Fall Meeting 2009, abstract #SM53A-1350
Physics
[2768] Magnetospheric Physics / Plasmasphere, [2772] Magnetospheric Physics / Plasma Waves And Instabilities, [2774] Magnetospheric Physics / Radiation Belts, [2778] Magnetospheric Physics / Ring Current
Scientific paper
Electromagnetic ion cyclotron (EMIC) waves in the Earth’s magnetosphere are excited near the magnetic equator with frequencies below the proton gyro-frequency. The free energy for wave growth is provided by temperature anisotropy of ring current (RC) ions, which naturally develops during inward convection from the plasmasheet. EMIC waves strongly affect the dynamics of resonant RC ions, thermal electrons and ions, and the outer radiation belt relativistic electrons, leading to non-adiabatic particle heating and/or pitch-angle scattering and loss to the atmosphere. The resent Cluster observations of EMIC waves and associated ion distributions in the inner magnetosphere during the November 2003 storm showed that although the temperature anisotropy of RC H+ with energies greater than 10 keV was high during the entire November 22 event, EMIC waves were observed only in conjunction with over an order of magnitude intensification of the ion fluxes below 1 keV. Similarly, observations of Pc 1-2 events in the dayside outer magnetosphere indicate that greatly increased fluxes of low energy protons are crucial for the instability driven by anisotropic RC H+. This suggests that a suprathermal plasma plays an important role in destabilization of more energetic RC and/or plasma sheet ions, and high energy anisotropic RC and/or plasma sheet protons appear to be a necessary but not sufficient condition for the occurrence of EMIC waves. As a result, both the cold plasmaspheric plasma and the suprathermal ions injected from the plasma sheet control EMIC wave excitation, and those ions have to be included in the total density model to correctly model EMIC wave generation and/or distribution in the Earth’s magnetosphere. Although the effect of density on EMIC wave generation is well-known, an assumption that the total plasma density is dominated by the thermal plasma was made in all previous efforts to model EMIC waves on a global magnetospheric scale. In other words, RC ions were only included in growth rate but omitted in the real part of the wave dispersion relation. This assumption could be especially severe outside the plasmapause where the RC density contribution is comparable to or even dominates the thermal plasma contribution. In this presentation, using our model of EMIC waves self-consistently interacting with RC ions, we study the role of RC H+ in the real part of EMIC wave dispersion relation during May 2-3, 1998. The main results of our study are: First, RC H+ only contributes a few percent to the total plasma density near the inner edge of the plasmasphere boundary layer but it can dominate outside the plasmapause. About 90 % of the RC H+ density in the dawn MLT sector is formed by the suprathermal ions (< 2 keV), while a major contribution in dusk comes from the 10-100 keV ions allowing not more than 10-20 % for the suprathermal ions. Second, RC H+ in the real part of the wave dispersion relation increases local growth rate leading to a dramatic change in the wave global patterns. The “new” EMIC waves are generated not only on the plasmapause, as expected from previous global simulations, but also inside and outside the plasmapause consistent with the observations.
Gamayunov Konstantin
Rassoul Hamid
Zhang Minghui
No associations
LandOfFree
Electromagnetic Ion Cyclotron Wave Redistribution in the Earth’s Magnetosphere due to Ring Current H+ in the Wave Dispersion Relation does not yet have a rating. At this time, there are no reviews or comments for this scientific paper.
If you have personal experience with Electromagnetic Ion Cyclotron Wave Redistribution in the Earth’s Magnetosphere due to Ring Current H+ in the Wave Dispersion Relation, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Electromagnetic Ion Cyclotron Wave Redistribution in the Earth’s Magnetosphere due to Ring Current H+ in the Wave Dispersion Relation will most certainly appreciate the feedback.
Profile ID: LFWR-SCP-O-1881593