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Seminars and Colloquia

Physics

Relativistic charge solitons caused due to Nonlinear-Landau damping : A candidate to explain coherent radio emission from pulsars 
 
Thu, Mar 28, 2019,   04:00 PM at Seminar Hall 31, 2nd Floor, Main Building

Dr Dipanjan Mitra
NCRA-TIFR,

Abstract:
Collective plasma emissions in astrophysics are referred to as
coherent emission. Radio emission from pulsars are coherent in nature,
and observations strongly suggest that: (a) the coherent emission is
excited by acceleration of ``charge bunches'' in a 1D relativistically
moving pair plasma, and (b) the radio emission occurs at a frequency
lower than the local plasma frequency. Theoretically, it is
challenging to form a stable charge bunch that follow the above
observational constraints, and even after fifty years of pulsar
discovery the mechansim of how collective plasma process excites the
coherent radio emission remains an unresolved problem.
 
In this talk we will propose a potential resolution for the formation
of charge bunches, based on a kinetic theory of linear and non-linear
growth of electrostatic Langmuir waves in the relativistic pair
plasma.  In the non-linear regime, we will demonstrate the existence
of relativistic charge solitons (the “charge bunches”) as solutions of
the non-linear Schrodinger equation (NLSE). The formalism includes the
crucial effect of non-linear Landau damping, which is inherent in the
derivation of the NLSE. We will also demonstrate a remarkable finding,
i.e. the emergence of these intense soliton-like pulses from an
initial disordered state of Langmuir waves.
 
Pulsars: Are rotating neutron stars.
 
Landau damping: Discoverd by L. Landau, is the phenomenon of 
damping of waves in collisionless plasma due to resonant 
energy exchange between waves and particle.
....................................................................................................................................................................
 
Core Work reported in Paper, reference: Lakoba, T, Mitra, D., 
Melikidze G. I., 2018, MNRAS, 480, 4526

 

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