Volume 653, September 2021
|Number of page(s)||5|
|Section||Letters to the Editor|
|Published online||09 September 2021|
Letter to the Editor
Geometry of radio pulsar signals: The origin of pulsation modes and nulling
Nicolaus Copernicus Astronomical Center, Polish Academy of Sciences, Rabiańska 8, 87-100 Toruń, Poland
Accepted: 6 August 2021
Radio pulsars exhibit an enormous diversity of single pulse behaviour that involves sudden changes in pulsation mode and nulling occurring on timescales of tens or hundreds of spin periods. The pulsations appear both chaotic and quasi-regular, which has hampered their interpretation for decades. Here I show that the pseudo-chaotic complexity of single pulses is caused by the viewing of a relatively simple radio beam that has a sector structure traceable to the magnetospheric charge distribution. The slow E × B drift of the sector beam, when sampled by the line of sight, produces the classical drift-period-folded patterns known from observations. The drifting azimuthal zones of the beam produce the changes in pulsation modes and both the intermodal and sporadic nulling at timescales of beating between the drift and the star spin. The axially symmetric conal beams are thus a superficial geometric illusion, and the standard carousel model of pulsar radio beams does not apply. The beam suggests a particle flow structure that involves inward motions with possible inward emission.
Key words: pulsars: general / pulsars: individual: PSR B1919+21 / pulsars: individual: PSR B1237+25 / pulsars: individual: PSR B1918+19 / radiation mechanisms: non-thermal
© ESO 2021
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