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Category: Communication

Description: **Authors:** Ruben Andreasyan, Gurgen Paronyan, Andranik Suqiasyan **Affiliations:** Byurakan Astrophysical Observatory after V.A. Ambartsumian, Armenia Faraday rotation data on 180 pulsars and more than 2000 extragalactic radio sources are used in a detail study of the magnetic field in the direction of galactic longitude 400 \less l \less 700, that includes the Sagittarius spiral arm region. The highly regular magnetic field of the Sagittarius spiral arm and in the Halo of northern hemisphere of Galaxy is directed nearly to the Sun, when the magnetic field of southern hemisphere Halo is directed from the Sun. This is clear from the study of distribution of rotation measures of pulsars as well as from the data of extragalactic radio sources. We propose that the Sagittarius spiral arm lies mainly to the north of the Galactic plane and the magnetic field in this arm has the same direction as in the halo of northern hemisphere. The magnetic field with opposite direction in the southern hemisphere of Galaxy is the field of the halo of the southern hemisphere.