In this site, we present both still and moving "maps" of the emitting "micro-storms" which circulate around the magnetic polar-cap region of pulsar B0943+10 and produce its radio frequency emission. The maps are based on three sets of observations at the Arecibo Observatory in Puerto Rico, the first on January 2, 1972 at 430 MHz ("old 430-MHz"), the second on January 17, 1990 at 111.5 MHz ("111-MHz"), and the most recent on on October 19, 1992 at 430 MHz ("new 430_MHz"). The still "maps" show the average positions and intensities of the emitting "micro-storms" over several hundred pulses during each of the observations. In each observation, just 20 "micro-storms" comprise the full pattern of emission---some stronger and some weaker---and the moving images show how their positions and intensities change over the course of the observations.
The pulsar rotates on its axis about every 1.1 seconds, and the "micro-storms" rotate around the magnetic axis about every 37 rotation periods. However, we have depicted this rotating pattern of radio-emitting storms as fixed in order to show their changing intensities, positions and forms more clearly. In B0943+10 the magnetic axis makes an angle of about 12 degrees to the rotation axis, and the "nearer" rotational pole is depicted as "up" in the various "maps". Similarly, our sightline to the pulsar makes an angle of about 7 degrees with the rotational axis---thus crossing the magnetic polar-cap region at the top of the "maps" some 5 degrees from the magnetic pole. Therefore, the "dark" region in the center of each figure cannot be mapped because it is never reached during successive rotations of the pulsar. This "tangential" sightline geometry is typical of other pulsars which exhibit well ordered patters of subpulse beams.
While the radio emission comes from a height of 1-200 kilometers, it results from the powerful "micro-storms" in the polar-cap region near the surface of the pulsar. This region in B0943+10 has a radius of only about 200 meters, making the storms themselves only some 30-40 meters in diameter. The pulsar emits a total energy of about 1/25 that of the Sun, making the energy associated with each of the "micro-storms" about 1/1000 that of the Sun. It is then remarkable that pulsar radio emission can be traced to building-sized storms on the city-sized star!
All three observations begin with what Suleymanova and Izvekova have called "B" mode pulses-sequences--- that is, sequences which exhibit well ordered patterns of "drifting" subpulses. However, the newer observation at 430 MHz exhibits a change to the weaker, disorganized "Q" mode at pulse number 817. The moving image for this sequence shows what occurs at this point quite graphically; the full pattern of "micro-storms" disappears, and the few remaining storms become both brighter and extend to larger distances from the magnetic pole.
Two papers reporting these results more fully are now in preparation and will be listed below when they are available in preprint form. This work represents a collaboration between Dr. Joanna Rankin (Dept. of Physics, University of Vermont) and myself (i.e. Avinash A. Deshpande of the Raman Research Institute).
Caution: The moving images are designed to be viewed with Netscape itself. If the user preferences have been set to use xv to load .gif files, then only the first "movie" frame can be viewed. To remedy this problem, select "Preferences" and then "Applications" and remove any reference to an application to view .gif files.
Note: The moving images for Old 430-MHz & 111.5-MHz are presently available from a remote site only.
