Electron Pitch‐Angle Distribution in Earth's Magnetotail: Pancake, Cigar, Isotropy, Butterfly, and Rolling‐Pin

Electron pitch‐angle distributions, including isotropy, pancake, cigar, butterfly, and recently discovered rolling‐pin distributions, are crucial to understanding electron dynamics in the magnetotail. However, occurrence rates of these distributions remain unclear. Here, for the first time, we reveal the occurrence rates of these distributions in the magnetotail by using Cluster data during 2001–2009, with special focus on the newly reported rolling‐pin distribution. We find that percentages of these distributions are 44.7% (isotropy), 31.3% (pancake), 17.5% (cigar), 4.9% (rolling‐pin), and 1.6% (butterfly), respectively. We find that in the XYGSM plane, occurrence rates of these PADs peak near: [XGSM ≈ −11 RE, YGSM ≈ −5 RE] (isotropy), [XGSM ≈ −15 RE, YGSM ≈ −11 RE] (pancake), [XGSM ≈ −11 RE, YGSM ≈ −5 RE] (cigar), [XGSM ≈ −11 RE, YGSM ≈ −3 RE] (rolling‐pin), and [XGSM ≈ −11 RE, YGSM ≈ −4 RE] (butterfly), respectively; and along the r direction, where r is the distance to the center of the Earth in the XYGSM plane, their occurrence rates peak near: −18 RE