A new very low frequency phenomenon: Whistlers trapped below the protonosphere

Abstract

A new whistler phenomenon has been identified through measurements at ground stations, on an Aerobee rocket between 100 and 200 km, and on the Alouette satellite at 1000 km. The new phenomenon is called the 'subprotonospheric' or 'SP' whistler, since most of its path appears to be restricted to the region below about 1000 km. The first example of an SP whistler was reported by Barrington and Belrose. In the present report a large number of observations are summarized, and the basic characteristics of the new phenomenon are described. Experimental results are presented which suggest that the whistler ray path is confined to the region between roughly 100-and 1000-km altitude, and that the whistler energy can echo back and forth between these levels. The SP phenomenon occurs mostly at night, typically within a few hours after sunset. SP events are often observed over a period of one or two hours in duration and, for a single Alouette pass, have been observed over a north-south range as great as 2000 km in extent. The evidence. suggests that the SP phenomenon occurs mostly near sunspot minimum and at dipole latitudes greater than 45 degrees.

Study of oblique whistlers in the low-latitude ionosphere, jointly with the C/NOFS satellite and the World-Wide Lightning Location Network

“…Our search algorithm penalizes multi-dispersive propagation and favors simple, single-mode whistler dispersion. More work will be required to determine whether, on the one hand, we are simply missing SP whistlers which are actually present due to lightning near the subsatellite point, or whether, on the other hand, the SP whistlers are not present at the low latitudes of C/NOFS, in keeping with early predictions of SP latitude dependence (Carpenter et al, 1964). We mention that, at least in mid-latitudes, the unducted, oblique whistler has already been shown to account for much of lightning-induced electron precipitation (Bortnik et al, 2006a, b;Lauben et al, 1999;Peter and Inan, 2004), so this seems to add to the original confirmation of the role of the unducted, oblique whistler (Holzworth et al, 1999).…”

Fluctuating magnetic fields in the magnetosphere

“…The possibility of such ray paths has been confirmed by ray tracing techniques by and Walker (1966). Subprotonospheric whistlers are usually observed in the frequency range from 700-2500 Hz, at local night, and at dipole latitudes greater than about 45 ~ (L = 2) (Carpenter et al, 1964).…”

“…Furthermore, with the exception of two above studies of isolated events, there has been little recent activity in studying this phenomenon, and our only knowledge of their average properties comes from the preliminary study of Carpenter et al (1964). The subprotonospheric whistler remains one whistler phenomenon that requires further experimental and theoretical study.…”

ESD whistlers from local Thunderstorms observed at Srinagar (L = 1.28) – First observation from Low Latitudes

“…SP whistler energy echoes back and forth between 100 and 1000 km inonospheric heights with increasing dispersions corresponding to the increase in number of reflections (Carpenter et al, 1964). One of the interesting features of SP-whistlers is that they are found to obey Eckersley law within the experimental error.…”

“…Thus ESD whistlers earlier observed at ground-based stations Suffield and Great Whale River in USA, Jammu and Bhopal in India were explained on the basis of non-ducted whistler mode propagation (Carpenter et al, 1964;Okuzawa and Horita, 1974;Shawhan, 1996;Singh et al, 1972;Lalmani et al, 1999Lalmani et al, , 2001Singh et al, 2005). On the other hand ESD whistlers observed at ground stations Kakioka and Tohakatta in Japan were explained in terms of field-aligned (ducted) propagation by Tsuruda et al (1964).…”