The interpretation of magnetic field data at low magnetic latitudes is difficult because the vector nature of the magnetic field increases the complexity of anomalies from magnetic rocks. The most obvious approach to this problem is to reduce the data to the magnetic pole (RTP), where the presumably vertical magnetisation vector will simplify observed anomalies. However, RTP requires special treatment of north-south features in data observed in low magnetic latitudes due to high amplitude corrections of such features. Furthermore, RTP requires the assumption of induced magnetisation with the result that anomalies from remanently and anisotropically magnetised bodies can be severely disturbed.The amplitude of the 3-D analytic signal of the total magnetic field produces maxima over magnetic contacts regardless of the direction of magnetisation. The absence of magnetisation direction in the shape of analytic signal anomalies is a particularly attractive characteristic for the interpretation of magnetic field data near the magnetic equator. Although the amplitude of the analytic signal is dependent on magneti sation strength and the direction of geological strike with respect to the magnetisation vector, this dependency is easier to deal with in the interpretation of analytic signal amplitude than in the original total field data or pole-reduced magnetic field. It is also straightforward to determine the depth to sources from the distance between inflection points of analytic signal anomalies.

Australia Telescope Compact Array radio continuum maps of the edge‐on galaxy in Circinus are presented for four frequencies. The unresolved core of the galaxy measures less than 20 pc in diameter and has a flat spectral index of α =−0.06 ± 0.15 (S ∝ να). An arcsecond‐scale jet close to the core is directed similarly to the previously detected larger scale plumes. The core is surrounded by what we believe to be a diffuse radio counterpart to the recently discovered r =  200 pc starburst ring.  The large radio lobes are shown to consist of central plume features surrounded by edge‐brightened emission. The polarized emission from these lobes is mainly contained within these distinct plume and edge‐brightened features, the latter showing very high degrees of polarization (> 50 per cent at λ= 6 cm).  A study of the depolarization and rotation measures indicates that with respect to the galactic disc, the northern radio lobe is in the foreground and directed towards us whilst the opposite is true for the southern lobe.  Analysis of the spectral indices along the plume structures shows slight steepening of values away from the core (α ≃ −0.8), indicative of ageing of electrons along the flow. Brighter hotspots of emission present in both north and south plumes show significantly flatter spectral indices (α ≃ −0.4). This is similar to the spectral index behaviour observed in higher energy astrophysical jets. High field strengths in the edge‐brightened regions (up to 18 μG) of the radio lobes are probably owing to compression of the frozen halo field, indicative of interaction between the ejecta driven bow shock with the ambient halo medium.  Comparison with other galaxies displaying similar features suggests that although the nuclear starburst is no doubt contributing significantly to the concentration of cosmic rays in the radio lobes, a Seyfert nucleus is needed to explain the collimated jet observed in these objects.

HI observations with the Australia Telescope Compact Array (ATCA) are used to study the neutral gas distribution and kinematics of the Circinus galaxy. One of the most outstanding features of Circinus is its enormous size (at least 80 arcmin or nearly 100 kpc, assuming a distance of 4 Mpc) revealing a beautiful large‐scale spiral pattern. The fit of a tilted‐ring model to the velocity field reveals a strong kinematic warp of the outer spiral arms. The inner region (radius 250 arcsec or 5 kpc) contains a highly elongated structure with non‐circular motions, suggesting that Circinus is a barred spiral galaxy. At the centre of Circinus there is a 50‐arcsec or 1‐kpc‐radius HI ring or disc rotating with a speed of at least 200 km s‐1.

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The TAURUS‐2 Fabry–Perot interferometer, mounted on the 3.9‐m Anglo‐Australian Telescope, has been used to observe the Circinus galaxy. We have mapped the intensity and velocity distribution of the ionized hydrogen in the galaxy using the Balmer series Hα spectral line. The semiresolved core (observed with a seeing disc of 30 pc) appears amorphous in shape, which is commonly observed in Seyfert 2 galaxies. Its peak coincides with the core position measured in the radio continuum, suggesting that ionized gas surrounds a non‐thermal source. A circumnuclear ring or spiral of radius 220 pc and a rotational velocity of 350 km s−1 (assuming circular motions) surrounds the core. The inclination angle of this feature, i=40°±10°, is less than that of the previously observed radio continuum disc. The velocity channel maps obtained for the Hα ring show that the kinematics resemble those of a rotating ring and the intensity displays a complex structure indicative of several, unresolved, H II regions. We believe the ring to represent a circumnuclear starburst. Our Hα data also show the presence of the previously detected [O III] ionization cone to the north‐west of the core, measuring more than 400 pc in length. We suggest that the ionization cone lies in a different plane from that of the starburst ring and is directed away from us. Several kinematic components of the core are derived and we calculate an outflow velocity in excess of 150–200 km s−1 for gas above the core of Circinus. We also present evidence for inflowing ionized gas at the centre of Circinus. The correlation of the Hα and radio continuum features is discussed, as well as the possible presence of a starburst‐driven superwind in the Circinus galaxy.