ELFT HÍRADÓ

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ELTE Fizikai Intézet

                                ORTVAY KOLLOKVIUM

                    2016. március 31., csütörtök, 15:00-kor
                Az ELTE Pázmány Péter s. 1/A alatti épületében
                           földszinti 0.81 előadóban

                                Yoshiharu Omura
   (Research Institute for Sustainable Humanosphere, Kyoto University)

            "Dynamic variation of radiation belts due to nonlinear
	    wave-particle interactions during space weather events" 


Kivonatos ismertetés:
During space weather events, energetic particles are injected from the 
magnetotail to the inner magnetosphere, and various kinds of wave-particle 
interactions take place. Whistler-mode chorus emissions are one of the most 
important waves for the dynamics of relativistic electrons forming the outer 
radiation belt. Chorus emissions are excited via interaction with 10 – 100 keV 
electrons outside the plasmasphere [1,2], and they can accelerate a fraction 
of resonant electrons to MeV energy through nonlinear wave trapping mechanisms 
called relativistic turning acceleration (RTA) [3] and ultra-relativistic 
acceleration (URA) [4]. The time scale of acceleration is much shorter than 
that predicted by the quasi-linear theory [5]. Another kind of waves important 
for the radiation belt dynamics is EMIC triggered emissions with rising-tone 
frequencies excited by nonlinear interaction with 10 – 100 keV protons both 
inside and outside the plasmasphere [6]. The EMIC emissions can interact with 
relativistic electrons (> 0.3 MeV) and scatter them to lower pitch angles 
efficiently by nonlinear wave trapping, resulting in significant precipitation 
of radiation belt electrons [7,8] as well as energetic protons [9]. We review 
recent development of nonlinear theory and simulations that can describe 
dynamic nature of the radiation belts under intense space weather events.

References:

1. Y. Omura, et al., J. Geophys. Res., 114, A07217, 2009.

2. Y. Omura and D. Nunn, J. Geophys. Res., 116, A05205, 2011.

3. Y. Omura N. Furuya, D. Summers, J. Geophys. Res., Vol. 112, A06236, 2007.

4. D. Summers, and Y. Omura, Geophys. Res. Lett., 34, L24205, 2007.

5. Y. Omura et al., J. Geophys. Res., 120, 9545–9562, 2015.

6. S. Nakamura, et al., J. Geophys. Res., 120, 7318–7330, 2015.

7. Y. Omura and Q. Zhao, J. Geophys. Res., 118, 5008, 2013.

8. Y. Kubota et al., J. Geophys. Res., 120, 4384-4399, 2015.

9. M. Shoji and Y. Omura, J. Geophys. Res., 118, 5553, 2013