Distribution of X‐type magnetic neutral lines in the magnetotail with Geotail observations

We obtained the distribution of the X‐type magnetic neutral lines in the magnetotail from X GSM = 0 to −210 R E with Geotail observations. For the detection of the neutral lines, we adopted simultaneous reversals of magnetic field from north to south (south to north) and ion bulk velocity from earthward to tailward (tailward to earthward). In the near‐tail region (0 ≥ X GSM > −30 R E ), the occurrence rate of the reversal events had a peak at Y GSM ≃ +9 R E and was characterized by a very asymmetric form in the Y GSM direction. The region of the reversal events appeared to expand in the Y GSM direction up to a 50 R E width at X GSM ≃ −50 R E . This width was maintained in the region further downtail ( X GSM < −50 R E ). The occurrence rate integrated in the Y GSM direction was found to have a maximum at X GSM ≃ −60 R E .