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We have measured the rotation measure (RM) of 37 extragalactic sources in the region from $1^h$~$50^m$ to $3^h$~$10^m$ Right Ascension and $32\deg$ to $44\deg$ Declination. The goal of these observations is to determine the turbulent properties of the ISM. This area is unique in that it is the only region where the $H_\alpha$ intensity has been mapped out completely, both spatially and in velocity (Reynolds, Ap.J.,1980,236,p 153). With a combination of rotation measure and emission measure measurements, it may be possible to separately determine the electron density and magnetic field fluctuations in ISM turbulence. The measurements show that the RMs of the extragalactic sources are relatively smooth over the whole region. However, changes in the RMs of the extragalactic sources are observed between sources separated by a few degrees or less. In order to determine what part of these changes are due to structure in the galaxy and which are random variations due to turbulence, we have compared the measured RMs to various models for the galactic magnetic field and plasma density. The structure function of the random component of the RMs can be determined from the residuals in order to make an estimate of the amplitude and the largest scale size of the turbulence.
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