The magnetotail of Mars: Phobos observations

Magnetic measurements obtained by the Phobos spacecraft in circular orbit at 2.86 Mars radii show a 2‐lobed magnetic tail. The peak solar‐antisolar component of the magnetic field in these lobes is about 14 nT. The polarity of the tail lobes is sensitive to the direction of the interplanetary magnetic field as expected for a magnetic field induced by the solar wind interaction. The ratio of the cross‐tail component of the tail field is over twice that in the solar wind, or about a factor of 4 larger than the ratio observed in the Venus tail at greater distances. Since the ratio is observed to decrease with increasing distance in the Venus tail, we conclude that the Mars and Venus magnetotails are in fact similar. If there is an influence of an intrinsic planetary magnetic field on the magnetotail of Mars that influence is weak.