We developed a new approximation for the frequencies at which the absorption coefficient is negative, and therefore the electron- cyclotron-maser mechanism operates. This new approximation is given by Eq. 4, and is easy to compute. Our approximation gives results which are much more accurate than previous approximations, and are practically the same as the results of a full numerical calculation. The frequencies derived with the approximation are within of the numerically calculated frequencies.
The parameters entering the approximation are the angle of emission to the magnetic field , the loss-cone opening angle , the ratio , and the ratio .
The new approximation can be used to define a range of possible
frequencies of millisecond spike emission, given the ratio
. Or, when spike emission is
detected, the approximation can be used to give the range of physical
parameters in the emission region.
© European Southern Observatory (ESO) 1999
Online publication: July 16, 1999