Summary: | We present the first and direct comparison between magnetospheric plasma waves and polar mesosphere winter echoes (PMWE) simultaneously observed by the conjugate observation with Arase satellite and high‐power atmospheric radars in both hemispheres, namely, the Program of the Antarctic Syowa Mesosphere, Stratosphere, and Troposphere/Incoherent Scatter Radar (PANSY) at Syowa Station (SYO; ‐69.00°S, 39.58°E), Antarctica, and the Middle Atmosphere Alomar Radar System (MAARSY) at Andøya (AND; 69.30°N, 16.04°E), Norway. The PMWE were observed during 03‐07 UT on March 21, 2017, just after the arrival of corotating interaction region (CIR) in front of high‐speed solar wind stream. An isolated substorm occurred at 04 UT during this interval. Electromagnetic ion cyclotron (EMIC) waves and whistler‐mode chorus waves were simultaneously observed near the magnetic equator and showed similar temporal variations to that of the PMWE. These results indicate that chorus waves as well as EMIC waves are drivers of precipitation of energetic electrons, including relativistic electrons, which make PMWE detectable at 55‐80 km altitude. Cosmic noise absorption (CNA) measured with a 38.2‐MHz imaging riometer and low‐altitude echoes at 55‐70 km measured with an MF radar at SYO also support the relativistic electron precipitation. We suggest a possible scenario in which the various phenomena observed in near‐Earth space, such as magnetospheric plasma waves (EMIC waves and chorus waves), pulsating auroras, CNA, and PMWE, can be explained by the interaction between the high‐speed solar wind containing CIRs and the magnetosphere. journal article
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