Multi beam observations of cosmic radio noise using a VHF radar with beam forming by a Butler matrix

[摘要] The Leibniz-Institute of Atmospheric Physics (IAP) in Kühlungsborn startedto install a new MST radar on the North-Norwegian island Andøya(69.30° N, 16.04° E) in 2009. The new Middle Atmosphere AlomarRadar System (MAARSY) replaces the previous ALWIN radar which has beensuccessfully operated for more than 10 years. The MAARSY radar providesincreased temporal and spatial resolution combined with a flexible sequentialpoint-to-point steering of the radar beam. To increase the spatiotemporalresolution of the observations a 16-port Butler matrix has been built andimplemented to the radar. In conjunction with 64 Yagi antennas of the formerALWIN antenna array the Butler matrix simultaneously provides 16 individualbeams. The beam forming capability of the Butler matrix arrangement has beenverified observing the galactic cosmic radio noise of the supernova remnantCassiopeia A. Furthermore, this multi beam configuration has been used inpassive experiments to estimate the cosmic noise absorption at 53.5 MHzduring events of enhanced solar and geomagnetic activity as indicators forenhanced ionization at altitudes below 90 km. These observations arewell correlated with simultaneous observations of corresponding beams of theco-located imaging riometer AIRIS (69.14° N, 16.02° E) at38.2 MHz. In addition, enhanced cosmic noise absorption goes along withenhanced electron densities at altitudes below about 90 km as observedwith the co-located Saura MF radar using differential absorption anddifferential phase measurements.

[学科分类] 电子、光学、磁材料