| Summary: | We report two outstanding events on the response of ELF/VLF waves associated with\nmagnetospheric sudden impulses. The former event was observed at 12:35-12:40UT on\nJanuary 18, 2013 at Athabasca, Canada, Kannuslehto, Finland and Syowa Station, Antarctica.\nThe solar-wind density and speed increased by ~20 /cm3 and ~40 km/s, respectively, while\nthe IMF-Bz was kept northward, resulting in no development of storm and substorm. The\nthree ground stations show enhancement of ELF/VLF hiss starting at 1235 UT at Syowa\n(15LT), 1236 UT at Kannuslehto (14LT), and 1240 UT at Athabasca (05LT) from dayside to\ndawn side, indicating that the ELF/VLF hiss was globally excited associated with this sudden\nimpulse. The 4-min delay at 05 LT at Athabasca may suggest delay of wave generation until\nthe energization of magnetospheric electrons reaches a certain level. The latter event was\nobserved at 11:17 UT, 2 to 3 minutes after a very intense sudden impulse (SYM-H amplitude\n~63 nT) during northward IMF, at both Athabasca and RBSP-B, which are at nearly\nconjugate locations at 03 MLT. A chorus-like burst was centered at ~2.5 kHz lasting\napproximately 3 minutes. At RBSP-A, a hiss emission was observed below 1.5kHz first at\n11:16 UT about one-minutes before the chorus burst, while such hiss was not observed at\nAthabasca. This fact indicates that the generation mechanisms of hiss and discrete chorus\nemissions are different at the beginning of electron acceleration, and that their propagation\nprocess from the source magnetosphere to the ground station is also different.
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