Ändra sökning
RefereraExporteraLänk till posten
Permanent länk

Direktlänk
Referera
Referensformat
  • apa
  • harvard1
  • ieee
  • modern-language-association-8th-edition
  • vancouver
  • Annat format
Fler format
Språk
  • de-DE
  • en-GB
  • en-US
  • fi-FI
  • nn-NO
  • nn-NB
  • sv-SE
  • Annat språk
Fler språk
Utmatningsformat
  • html
  • text
  • asciidoc
  • rtf
Faraday signature of magnetic helicity from reduced depolarization
KTH, Centra, Nordic Institute for Theoretical Physics NORDITA.ORCID-id: 0000-0002-7304-021X
2014 (Engelska)Ingår i: Astrophysical Journal, ISSN 0004-637X, E-ISSN 1538-4357, Vol. 786, nr 2, s. 91-Artikel i tidskrift (Refereegranskat) Published
Abstract [en]

Using one-dimensional models, we show that a helical magnetic field with an appropriate sign of helicity can compensate the Faraday depolarization resulting from the superposition of Faraday-rotated polarization planes from a spatially extended source. For radio emission from a helical magnetic field, the polarization as a function of the square of the wavelength becomes asymmetric with respect to zero. Mathematically speaking, the resulting emission occurs then either at observable or at unobservable (imaginary) wavelengths. We demonstrate that rotation measure (RM) synthesis allows for the reconstruction of the underlying Faraday dispersion function in the former case, but not in the latter. The presence of positive magnetic helicity can thus be detected by observing positive RM in highly polarized regions in the sky and negative RM in weakly polarized regions. Conversely, negative magnetic helicity can be detected by observing negative RM in highly polarized regions and positive RM in weakly polarized regions. The simultaneous presence of two magnetic constituents with opposite signs of helicity is shown to possess signatures that can be quantified through polarization peaks at specific wavelengths and the gradient of the phase of the Faraday dispersion function. Similar polarization peaks can tentatively also be identified for the bi-helical magnetic fields that are generated self-consistently by a dynamo from helically forced turbulence, even though the magnetic energy spectrum is then continuous. Finally, we discuss the possibility of detecting magnetic fields with helical and non-helical properties in external galaxies using the Square Kilometre Array.

Ort, förlag, år, upplaga, sidor
2014. Vol. 786, nr 2, s. 91-
Nyckelord [en]
galaxies: magnetic fields, methods: data analysis, polarization
Nationell ämneskategori
Fysik
Identifikatorer
URN: urn:nbn:se:kth:diva-146552DOI: 10.1088/0004-637X/786/2/91ISI: 000335884500015Scopus ID: 2-s2.0-84899460053OAI: oai:DiVA.org:kth-146552DiVA, id: diva2:724237
Forskningsfinansiär
EU, Europeiska forskningsrådet, 227952Vetenskapsrådet, 621-2011-5076 2012-5797
Anmärkning

QC 20140612

Tillgänglig från: 2014-06-12 Skapad: 2014-06-12 Senast uppdaterad: 2017-12-05Bibliografiskt granskad

Open Access i DiVA

Fulltext saknas i DiVA

Övriga länkar

Förlagets fulltextScopus

Personposter BETA

Brandenburg, Axel

Sök vidare i DiVA

Av författaren/redaktören
Brandenburg, Axel
Av organisationen
Nordic Institute for Theoretical Physics NORDITA
I samma tidskrift
Astrophysical Journal
Fysik

Sök vidare utanför DiVA

GoogleGoogle Scholar

doi
urn-nbn

Altmetricpoäng

doi
urn-nbn
Totalt: 64 träffar
RefereraExporteraLänk till posten
Permanent länk

Direktlänk
Referera
Referensformat
  • apa
  • harvard1
  • ieee
  • modern-language-association-8th-edition
  • vancouver
  • Annat format
Fler format
Språk
  • de-DE
  • en-GB
  • en-US
  • fi-FI
  • nn-NO
  • nn-NB
  • sv-SE
  • Annat språk
Fler språk
Utmatningsformat
  • html
  • text
  • asciidoc
  • rtf