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Pulsar Nulling and Vacuum Radio Emission from Axion Clouds
Andrea Caputo1, Samuel J Witte2,3, Alexander A Philippov4
1CERN, Department of Theoretical Physics, Esplanade des Particules 1, P.O. Box 1211, Geneva 23, Switzerland.
Physical Review Letters
|November 1, 2024
Summary
A dense cloud of gravitationally bound axions can form in pulsar polar caps. This axion cloud can intermittently screen electric fields, causing pulsar radio emission to periodically null, or produce narrow radio lines.
Area of Science:
- Astrophysics
- Particle Physics
Background:
- Pulsars are rapidly rotating neutron stars with strong magnetic fields.
- Nonrelativistic axions are hypothetical particles that can be produced in extreme astrophysical environments.
Purpose of the Study:
- Investigate the interaction between axion clouds and pulsar magnetosphere electrodynamics.
- Determine the impact of axion clouds on particle acceleration and radio emission in pulsars.
Main Methods:
- Theoretical modeling of axion cloud formation and its effect on pulsar magnetosphere.
- Analysis of axion-field dynamics and electrodynamic screening mechanisms.
Main Results:
- Light axions (m_a ≲ 10^-7 eV) can screen electric fields, leading to periodic nulling of pulsar radio emission.
- Heavier axions can lead to incoherent oscillations, producing narrow radio lines via a novel emission process.
Conclusions:
- Axion clouds significantly influence pulsar emission mechanisms, offering new observational signatures.
- The interplay between axion clouds and pulsar electrodynamics provides a unique probe for axion physics.
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