Chorus

About: Chorus is a research topic. Over the lifetime, 829 publications have been published within this topic receiving 8415 citations.

Two types of magnetospheric ELF chorus and their substorm dependences

Abstract: The distribution of extremely low frequency (10-1500 Hz) magnetospheric chorus to all local times and latitudes is investigated in order to determine dependence on substorms, and to evaluate the conditions under which chorus is generated. The analysis carefully separates space and time effects by an investigation of data obtained by the OGO 5 search coil magnetometer. A study of spatial dependencies shows that chorus occurs in two magnetic regions: equatorial chorus is located near the equator, and high-latitude chorus is located above 15 degrees. An analysis of chorus in each of the regions illustrates that equatorial chorus is definitely related to substorm, whereas high-latitude chorus often occurs within magnetically quiet intervals.

The dramatic festivals of Athens

Abstract: The lesser festivals the great or city Dionysia the actors the costumes the chorus the audience the artists of Dionysus.

Global distribution of wave amplitudes and wave normal angles of chorus waves using THEMIS wave observations

Abstract: [1] The global distribution of chorus wave amplitudes and their wave normal angles is investigated using high-resolution wave spectra and waveform data from THEMIS for lower-band and upper-band chorus separately. Statistical results show that large amplitude chorus (>300 pT) occurs predominantly from premidnight to postdawn and is preferentially observed at lower L shells ( 50 pT) tend to have wave normal angles of <20° and their wave normal angles become even smaller with increasing wave amplitudes. For modest waves, the wave normal angles are distributed over a broad range with a major peak at <20° and a secondary peak at 60°–80°. Wave normal angles of lower-band chorus are generally smaller on the dayside than on the nightside possibly due to the more uniform and more compressed magnetic field configuration on the dayside. Lower-band chorus becomes more oblique with increasing latitude on the dayside, whereas on the nightside the probability of observing oblique chorus decreases at higher latitudes. Compared to lower-band chorus, the properties of upper-band chorus are somewhat different. Upper-band chorus is considerably weaker in magnetic wave amplitudes, shows tighter confinement to the magnetic equator (<10°), and occurs at smaller L shells (<8). Furthermore, wave normal angles of upper-band chorus are generally larger than those of lower-band chorus, but the occurrence rate still peaks at wave normal angles of <20°, particularly for strong upper-band chorus.

Chorus source locations from VLF Poynting flux measurements with the Polar spacecraft

Abstract: Previous studies have used indirect evidence to argue that whistler-mode chorus emissions are generated near the magnetic equator. In this paper a spatial survey of wave normals and Poynting vectors computed from three-component electric and magnetic field measurements is used to show that chorus is generated very close to the magnetic equator. One surprising result is that there are almost no chorus emissions propagating toward the magnetic equator, such as might be expected from high-latitude magnetospheric reflections. The absence of a reflected component indicates that the chorus is reabsorbed, probably by Landau damping, before returning to the magnetic equatorial plane.