DOI: 10.5285/151a855f-d030-485b-a2dd-4ea874e59bf6
title: Statistical investigation of the frequency dependence of the chorus source mechanism of plasmaspheric hiss

description: We use data from eight satellites to statistically examine the role of chorus as a potential source of plasmaspheric hiss. We find that the strong equatorial (|λm| &lt; 6°) chorus wave power in the frequency range 50 &lt; f &lt; 200 Hz does not extend to high latitudes in any MLT sector and is unlikely to be the source of the low frequency plasmaspheric hiss in this frequency range. In contrast, strong equatorial chorus wave power in the medium frequency range 200 &lt; f &lt; 2000 Hz is observed to extend to high latitudes and low altitudes in the pre-noon sector, consistent with ray tracing modelling from a chorus source and supporting the chorus to hiss generation mechanism. At higher frequencies, chorus may contribute to the weak plasmaspheric hiss seen on the dayside in the frequency range 2000 &lt; f &lt; 3000 Hz band, but is not responsible for the weak plasmaspheric hiss on the night-side in the frequency range 3000 &lt; f &lt; 4000 Hz. The research leading to these results has received funding from the Natural Environment Research Council (NERC) Highlight Topic grant NE/P01738X/1 (Rad-Sat) and the NERC grants NE/V00249X/1 (Sat-Risk) and NE/R016038/1. Jacob Bortnik received funding from NASA grant NNX14AI18G, and RBSP-ECT and EMFISIS funding provided by JHU/APL contracts 967399 and 921647 under NASA's prime contract NAS5-01072. Wen Li and Xiao-Chen Shen received funding from NASA grants 80NSSC20K0698 and 80NSSC19K0845, NSF grant AGS-1847818, and the Alfred P. Sloan Research Fellowship FG-2018-10936.
description: The plasma wave data used in this study come from Dynamics Explorer 1 (DE1), Cluster 1, Double Star TC1, THEMIS-A, THEMIS-D, THEMIS-E, RBSP-A and RBSP-B. The DE1 wave data are available from the CDAWeb (https://cdaweb.sci.gsfc.nasa.gov/index.html/). The Cluster and Double Star TC1 data are available at the Cluster Science Archive (https://www.cosmos.esa.int/web/csa). The THEMIS data is available from http://themis.ssl.berkeley.edu/data/themis/. The Van Allen Probes plasma wave data are available at https://emfisis.physics.uiowa.edu/data/index. The AE indices used in this study are available from the NSSDC Omniweb. Full details of the subsequent analysis are given in Meredith et al. [2021].
description: We use data from the Plasma Wave Instrument on DE1, the STAFF instruments on Cluster 1 and Double Star TC1, the Search Coil Magnetometers on THEMIS -A, -D and -E and the Electric and Magnetic Field Instrument Suite and Integrated Science (EMFISIS) instruments on board RBSP-A and RBSP-B. The Plasma Wave Instrument on DE1 measured one component of the magnetic field in the frequency range between 1.78 Hz and 410 kHz. The SFC Step Frequency Correlator, composed of two Step Frequency Receivers, provided the spectral density of the magnetic field coming from 128 frequency channels, logarithmically spaced between 105 Hz and 410 kHz. The STAFF experiment on Cluster 1 consists of a three-axis search coil magnetometer to measure magnetic fluctuations at frequencies up to 4 kHz, a waveform unit (up to either 10 Hz or 180 Hz) and a Spectrum Analyser (up to 4 kHz). The Spectrum Analyser combines the 3 magnetic components of the waves with the two electric components measured by the Electric Fields and Waves experiment (EFW) to calculate in real time the 5 x 5 Hermitian cross-spectral matrix at 27 frequencies distributed logarithmically in the frequency range 8 Hz to 4 kHz. The STAFF experiment on Double Star TC1 consisted of a search coil antenna, three pre-amplifiers, a magnetic waveform unit, and power supply provided by CETP, and a Digital Wave Processor (DWP) provided by the University of Sheffield. The DWP computed the spectral matrix (3 power spectra plus the cross phase between each component) at 27 frequencies between 8 Hz and 4 kHz. The Search Coil Magnetometers on THEMIS-A, -D and -E measure magnetic field fluctuations in the frequency range from 0.1 Hz to 4 kHz. The high resolution (fff) data used here consists of measurements of one component of the magnetic wave spectral density in the spacecraft spin plane, with a frequency resolution with 32 or 64 frequency bands logarithmically spaced over 4-4000 Hz. The EMFISIS Waveform Receivers on RBSP-A and RBSP-B measured the sum of the three components of the magnetic power spectral density of the waves in 65 frequency channels, with centre frequencies between 2.13 Hz and 11.24 kHz.
description: The wave data have been calibrated and quality-controlled prior to release.
description: The temporal resolution of the DE1 PWI was 32 s: one measurement was performed each second for 4 frequencies and 32 seconds were needed for full frequency coverage. The Cluster 1 STAFF instrument provided the spectral matrix (3 power spectra plus the cross phase between each component) at 27 frequencies between 8 Hz and 4 kHz with a time resolution between 0.125 and 4s. The Double Star TC1 STAFF instrument provided the spectral matrix (3 power spectra plus the cross phase between each component) at 27 frequencies between 10 Hz and 4 kHz with a 1 s time resolution. The THEMIS -A, -D , and -E high resolution SCM wave data were recorded with a cadence of 8 seconds. The RBSP-A and RBSP-B EMFISIS WFR data used in this study were collected at a 6 second time resolution.