In March 2005 , measurements by the Solar Wind Anisotropies ( SWAN ) instrument onboard the Solar and Heliospheric Observatory ( SOHO ) have shown that the heliosphere , the solar wind-filled volume which prevents the solar system from becoming embedded in the local ( ambient ) interstellar medium , is not axisymmetrical , but is distorted , very likely under the effect of the local galactic magnetic field . In March 2005 , it was reported that measurements by the Solar Wind Anisotropies ( SWAN ) instrument onboard the Solar and Heliospheric Observatory ( SOHO ) have shown that the heliosphere , the solar wind-filled volume which prevents the solar system from becoming embedded in the local ( ambient ) interstellar medium , is not axisymmetrical , but is distorted , very likely under the effect of the local galactic magnetic field .