The interesting thing, however, is that spacecraft observations, like the ones made by ESA's Venus Express, have shown that the ionosphere of Venus direct interaction with the solar winds causes an externally induced magnetic field, which deflects the particles from the solar winds and protects the atmosphere from being blown away from the planet.
However, the article also explains that the Venus magnetosphere is not as protective as earth's magnetosphere. Measurements of the Venus magnetic field show several similarities, such as deflection of the solar winds and the reconnections in the tail of the magnetosphere, causing plasma circulations in the magnetosphere. The differences might explain the fact that some gasses and water are lost from the Venus atmosphere. The magnetic field of Venus is about 10 times smaller as the earth's magnetic field. The shape of the magnetic field is also different. Earth has a more sharp magnetotail facing away from the sun and Venus has a more comet shaped magnetotail. During the reconnections most of the plasma is lost in the atmosphere.
The article explains therefore that although Venus does not have an intrinsic magnetic field, but the interaction of the thick atmosphere with the solar winds causes an externally induced magnetic field, that deflect the particles of the solar winds. The article suggests, however, that the different magnetic field may cause that lighter gasses are not that much protected and therefore are lost into space.