Whistler‐like pulsation events in the frequency range 20 to 200 Hz

Abstract

A class of events, sweeping down in frequency, occurring between 20 and 200 Hz, were observed for the first time. The observing site is at Poker Flat, Alaska, 65°N. Characteristics include a daytime diurnal maximum, an apparent seasonal minimum in winter, a tendency for maximum occurrences on magnetically quiet days, and a typical event duration of ∼1 minute. The events occur at the same frequencies as a type of hiss observed on OGO‐5 (Kivelson and Russell, 1973) and a class of events observed on Injun 5 called ‘lion's roar’ (Gurnett and Frank, 1972), but the spectral form of the events observed on the ground is quite different from either of those types.

Multiflash whistlers in ELF-band observed at low latitude

“…The maximum number of events observed around 09:00 to 10:00 h (IST) which is consistent with the low latitude observation by Wang et al (2005). There appears to be a night to dawn gap, the same as that reported by Heacock (1974), Sentman and Ehring (1994) or Wang et al (2005). There also appears an increased rate of occurrence from 20:00-23:00 h (IST), but no other peak is observed as reported by Wang et al (2005) from low latitude.…”

“…This peculiar event with a multiflash nature occurred only once during the whole period of observation. Time duration for various ELF whistlers and this unique multiflash ELF whistler event ranges from 0.5 s to 3.5 s much smaller than those in previous studies (Heacock, 1974;Kim et al, 2006;Sentman and Ehring, 1994;Wang et al, 2005) which were around 40 s to 120 s.…”

“…These emissions were detected to possess a frequency range similar to magnetosheath lion roar (Smith et al, 1967) Correspondence to: A. K. Singh (abhay s@rediffmail.com) but their spectral forms are quite different (Heacock, 1974). Sentman and Ehring's (1994) measurements at California reported whistler-like events with frequencies laying in ELFband, along with the dispersion characteristics and the local time occurrence distribution similar to the events detected by Heacock (1974). Recently, Wang et al (2005) and Kim et al (2006) also reported a similar type of ELF phenomena.…”

“…Extremely low frequency (ELF: 3-3000 Hz) waves have been associated with a range of magnetosphere-ionosphere coupling phenomena as well as meteorological phenomena (Magunia, 1996;Cummer et al, 1998). Heacock (1974), Sentman and Ehring (1994), Wang et al (2005) and Kim et al (2006) have reported ELF emissions/whistlers at much lower frequencies between 40-200 Hz. Heacock (1974) discovered dispersive emission in the ELF-band near Fairbanks, Alaska (geomag.…”

Case studies on the wave propagation and polarization of ELF emissions observed by Freja around the local proton gyrofrequency

“…Some common features have been found plied. The downward propagation in a limited frequency band in ground based observations of Heacock [1974]. can be possibly explained by the effects of propagation from the 6.…”