Astronomy and Astrophysics – Astrophysics
Scientific paper
2005-07-15
Astron.Nachr. 326 (2005) 414-427
Astronomy and Astrophysics
Astrophysics
13 pages, 2 figures; published in Astron. Nachr./AN
Scientific paper
10.1002/asna.200510366
The commonly used classical equipartition or minimum-energy estimate of total magnetic fields strengths from radio synchrotron intensities is of limited practical use because it is based on the hardly known ratio K of the total energies of cosmic ray protons and electrons and also has inherent problems. We present a revised formula, using the number density ratio K for which we give estimates. For particle acceleration in strong shocks K is about 40 and increases with decreasing shock strength. Our revised estimate for the field strength gives larger values than the classical estimate for flat radio spectra with spectral indices of about 0.5-0.6, but smaller values for steep spectra and total fields stronger than about 10 muG. In very young supernova remnants, for example, the classical estimate may be too large by up to 10x. On the other hand, if energy losses of cosmic ray electrons are important, K increases with particle energy and the equipartition field may be underestimated significantly. Our revised larger equipartition estimates in galaxy clusters and radio lobes are consistent with independent estimates from Faraday rotation measures, while estimates from the ratio between radio synchrotron and X-ray inverse Compton intensities generally give much weaker fields. This may be explained e.g. by a concentration of the field in filaments. Our revised field strengths may also lead to major revisions of electron lifetimes in jets and radio lobes estimated from the synchrotron break frequency in the radio spectrum.
Beck Rainer
Krause Marita
No associations
LandOfFree
Revised equipartition & minimum energy formula for magnetic field strength estimates from radio synchrotron observations does not yet have a rating. At this time, there are no reviews or comments for this scientific paper.
If you have personal experience with Revised equipartition & minimum energy formula for magnetic field strength estimates from radio synchrotron observations, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Revised equipartition & minimum energy formula for magnetic field strength estimates from radio synchrotron observations will most certainly appreciate the feedback.
Profile ID: LFWR-SCP-O-411175