Editing Pulsar wind nebula (section)

==Properties of pulsar wind nebulae==

Pulsar winds are composed of charged particles ([[plasma (physics)|plasma]]) accelerated to [[relativistic speed]]s by the rapidly rotating, powerful [[magnetic field]]s above {{convert|1|TG|e6T|abbr=off|lk=on}} that are generated by the spinning pulsar.  The pulsar wind often streams into the surrounding interstellar medium, creating a standing [[shock wave]] called the 'wind termination shock', where the wind decelerates to sub-relativistic speed. Beyond this radius, [[Synchrotron_radiation|synchrotron]] emission increases in the magnetized flow.

Pulsar wind nebulae often show the following properties:
* An increasing brightness towards the center, without a shell-like structure as seen in supernova remnants.
* A highly [[Polarization (waves)|polarized]] [[flux]] and a flat [[spectral index]] in the radio band, α=0–0.3. The index steepens at X-ray energies due to synchrotron radiation losses and on the average has an X-ray photon index of 1.3–2.3 (spectral index of 2.3–3.3).
* An X-ray size that is generally smaller than their radio and optical size (due to smaller synchrotron lifetimes of the higher-energy electrons).<ref name="Slane2000">{{cite journal |title=Chandra Observations of the Crab-like Supernova Remnant G21.5-0.9 |journal=Astrophysical Journal |first1=Patrick O. |last1=Slane |first2=Yang |last2=Chen |first3=Norbert S. |last3=Schulz |first4=Frederick D. |last4=Seward |first5=John P. |last5=Hughes |first6=Bryan M. |last6=Gaensler |display-authors=3 |volume=533 |issue=1 |pages=L29–L32 |date=April 2000 |pmid=10727384 |doi=10.1086/312589 |arxiv=astro-ph/0001536 |bibcode=2000ApJ...533L..29S|s2cid=17387448 }}</ref>
* A photon index at [[teraelectronvolt|TeV]] gamma-ray energies of ~2.3.

Pulsar wind nebulae can be powerful probes of a pulsar/neutron star's interaction with its surroundings. Their unique properties can be used to infer the geometry, energetics, and composition of the pulsar wind, the space velocity of the pulsar itself, and the properties of the ambient medium.<ref name="Gaensler2006">{{cite journal |title=The Evolution and Structure of Pulsar Wind Nebulae |journal=Annual Review of Astronomy and Astrophysics |last1=Gaensler |first1=Bryan M. |last2=Slane |first2=Patrick O. |volume=44 |issue=1 |pages=17–47 |date=September 2006 |doi=10.1146/annurev.astro.44.051905.092528 |arxiv=astro-ph/0601081 |bibcode=2006ARA&A..44...17G|s2cid=10699344 }}</ref>