Electric currents at IMF sector boundaries

Numerical simulation of magnetic field reconnection at IMF sector boundarie s shows that the reconnection line may be carried by the solar wind out of the region of the anomalous resistivity. This makes it possible to observe magnetic loops at the Earth's orbit open to the Sun as well as from it. Bes ides, it is shown that the current sheet in the vicinity of the reconnectio n line has to split into two currents. Experimental data on the structure of the sector boundaries are analyzed, a nd it is shown that the currents at sector boundaries are indeed often spli tted. The thickness of the splined boundaries may amount to 18 x 10(6) km; taking into account this value, the heliocentric distance of the region of anomal ous resistivity in the interplanetary current sheet is estimated as 0.4-0.5 AU. The probability of observing magnetic loops open towards the Sun seems to b e greater than that of loops open from the Sun, which suggests an essential asymmetry of the field reversal regions.