Geotail electron observations in association with intense bursts of electron cyclotron harmonic waves in the dayside magnetosphere

Along the magnetopause skimming orbit oil October 17, 1992, the Geotail spa cecraft observed intense bursts of electron cyclotron harmonic waves called "totem pole" (TP) emissions which occurred sporadically and intermittently in time in the dayside magnetosphere. The present paper focuses on the ana lysis of the electron environment associated with the TP emissions. Field a nalysis shows that, because of the occurrence of an intense Pc5 pulsation, there was E x B drift flow which was switching its direction in time near t he magnetopause. The Geotail/comprehensive plasma instrumentation data show that the electron density fluctuated corresponding to the drift flow varia tion. Overall, TP emissions tend to occur during a transient time interval including a time when the density of cold electrons below 100 eV takes a mi nimum value. In the interval from 2225 to 2235 UT, TP emissions were well c orrelated with the density decrease of the cold electrons. In the interval including a stagnation time of the low switching front the Sun-duskward to the tail-dawnward direction, the density of the cold electrons became minim um, and simultaneously, TP emissions were observed. Contrary to the decreas e of the cold electrons, the electron density increased st energies higher than 100 eV ill association with the TP emissions. Namely, the TP emissions were observed when the density ratio of the hot electrons to the cold ones (n(h)/n(c)) increased. In the interval from 2252 to 2302 UT, TP emissions were found during a transition time of the cold electron density. We call c onclude that the sporadic and intermittent signature of TP emissions can be due to the change of the electron environment driven by the intense field pulsation.