The CCD photometric observation of comet 103P/Hartley 2 with broadband optical filters was carried out at Xuyi Station of Purple Mountain Observatory, Chinese Academy of Sciences by use of Near Earth Object Telescope (NEOT). We monitored the comet from September 30 to November 4, 2010 and investigated the variation of activities. The Afρ parameter derived from our r broadband data varies from 46.0 to 126.0 cm and increases with time. The dust production rate in terms of Afρ was measured and a tentative calculation of the dust (or gas) loss-rate of nucleus was executed under the assumption that the nucleus of comet 103P/Hartley 2 is spherical. The r-band image and the surface brightness profile taken on September 30, 2010 was measured and the gradient of surface brightness profile of 103P/Hartley 2 showed m < 1.5.
We consider the instability of the cometary plasma tail which is composed of a neutral sheet, two lobes of the ion tail and solar wind. The plasma is assumed to be highly conductive and incompressible. The unstable state yields a magnetic field which is perpendicular to the tail axis. Our result is consistent with findings about plasma from the International Cometary Explorer （ICE）.
