 Magnetic holes with small scale sizes are often observed in the magnetotail plasma sheet by both cluster and TC1 satellites. These holes are not caused by flapping movements of the magnetotail current sheet, but rather by a dipolarized magnetic field topology. They are most common when the magnetic field has a northward orientation and tend to occur in regions where the plasma sheet is marginally stable. Additionally, the magnetic holes are usually accompanied by enhanced electron energy fluxes at 90-degree pitch angles, as well as increased proton Marmor radii. This article was authored by W. J. Sun, W. J. Sun, Q. Q. Schur and others.