Propagation characteristics of Pi 2 pulsations observed at high‐ and low‐latitude MAGDAS/CPMN stations: A statistical study

<jats:p>The objective of this study is to understand better the propagation of Pi 2 waves in the nighttime region. We examined Pi 2 oscillations that showed high correlation between high‐ and low‐latitude Magnetic Data Acquisition System/Circum Pan‐Pacific Magnetometer Network stations (correlation coefficient: ∣<jats:italic>γ</jats:italic>∣ ≥ 0.75). For each horizontal component (<jats:italic>H</jats:italic> and <jats:italic>D</jats:italic>) we examined the magnetic local time (MLT) dependence of the delay time of high‐latitude Pi 2 oscillations that corresponds to the highest correlation with the low‐latitude Pi 2 oscillation. We found the delay time of the high‐latitude <jats:italic>H</jats:italic> showed remarkable MLT dependence, especially in the premidnight sector: we found that in the premidnight sector the high‐latitude <jats:italic>H</jats:italic> oscillation tends to delay from the low‐latitude oscillation (<100 s). On the other hand, the delay time of the high‐latitude <jats:italic>D</jats:italic> oscillation was not significant (∼±10 s) in the entire nighttime sector. We propose a Pi 2 propagation model to explain the observed delay time of high‐correlation high‐latitude <jats:italic>H</jats:italic>. The model quantitatively explains the trend of the event distribution. We also examined the spatial distribution of high‐correlation Pi 2 events relative to the center of auroral breakups. It was found that the high‐correlation Pi 2 events tend to occur away from the center of auroral breakups by more than 1.5 MLT. The present result suggests that the high‐correlation <jats:italic>H</jats:italic> component Pi 2 oscillations at high latitude are a manifestation of forced Alfvén waves excited by fast magnetosonic waves.</jats:p>