[1] Numerical raytracing with Landau damping is used to calculate >100 keV electron precipitation signatures induced by hypothetical VLF transmitters distributed broadly in geomagnetic latitude and operating at a wide range of frequencies. A one-half second pulse from each source is simulated and attenuation to the base of the magnetosphere for geomagnetic latitudes from 10°to 60°is calculated. Source location affects induced precipitation more strongly than operating frequency or radiated power. Sources located at 35°to 45°induce the most >100 keV precipitation for the 10 to 40 kHz waves typical of ground-based VLF sources, while locations below l ' 15°or above l ' 55°are least effective at precipitating energetic electrons. In all cases, induced precipitation increases as the operating frequency decreases, with 10 kHz waves from a source at l ' 35°the most effective at precipitating >100 keV electrons. Precipitation signatures produced by five existing ground-based VLF transmitters are also simulated: the NAA, NLK, NAU, NPM, and NWC VLF transmitters. NWC induces the strongest >100 keV electron precipitation signature, followed by NPM, NAU, NAA, and NLK.

[1] Ionospheric effects of energetic electron precipitation induced by controlled injection of VLF signals from a ground based transmitter are observed via subionospheric VLF remote sensing. The 21.4 kHz NPM transmitter in Lualualei, Hawaii is keyed ON-OFF in 30 minute periodic sequences. The same periodicity is observed in the amplitude and phase of the sub ionospherically propagating signals of the 24.8 kHz NLK (Jim Creek, Washington) and 25.2 kHz NLM (LaMoure, North Dakota) transmitters measured at Midway Island. Periodic perturbations of the NLK signal observed at Palmer, Antarctica suggest that energetic electrons scattered at longitudes of NPM continue to be precipitated into the atmosphere as they drift toward the South Atlantic Anomaly. Utilizing a model of the magnetospheric waveparticle interaction, ionospheric energy deposition, and subionospheric VLF propagation, the precipitated energy flux induced by the NPM transmitter is estimated to peak at L $ 2 and $ 1.6 Â 10 À4 ergs s À1 cm À2 . Citation: Inan,

[1] Near loss cone energetic electron flux increases induced by ground-based very low frequency (VLF) transmissions are observed directly via satellite-based detection. In 2 years of experiments ranging from 27 March 2006 through 2 April 2008 with the 21.4-kHz transmitter NPM in Lualualei, Hawaii, and the French satellite DEMETER (detection of electromagnetic emissions transmitted from earthquake regions), only a few cases of detection of individual pulses of transmitter-induced precipitation of inner radiation belt electrons have been realized. Analysis of the specific cases of detection allow comparison of precipitating flux with predictions based on ray-tracing analyses of wave propagation and test particle modeling of the wave-particle interaction. Results indicate that the precipitated flux of >100 keV electrons induced by the NPM transmitter peaks at L ' 1.9 and, in the rare cases of detection, may be at higher energies than the $100 keV peak predicted by the model. The low detection rate is attributed to the orientation of the DEMETER particle detector, which is mostly overwhelmed by the trapped population at the location of detection.

Whistler mode waves in the magnetosphere play an important role in the energy dynamics of the Earth's radiation belts. Previous theoretical work has been extended to include ions in the fully adiabatic warm plasma theory. Using a finite electron and ion temperature of 1 eV, refractive index surfaces are calculated for 1–10 kHz whistler mode waves in the inner magnetosphere (L ≲ 2.5). For the frequencies of interest, a finite ion temperature is found to have a greater effect on the refractive index surface than the electron temperature and the primary effect is to close an otherwise open refractive index surface. Including a finite ion temperature is especially important when the wave frequency is just above the local lower hybrid resonance frequency. For wave frequencies more than ∼1 kHz above the local lower hybrid resonance frequency, including the ion temperature has a negligible effect on the refractive index surface calculation. The results are used to assess previous conclusions on whether in situ whistler mode sources can be realistically used to precipitate energetic electrons. It is found that the number of in situ sources needed to illuminate the inner plasmasphere (L≲2.5) with whistler mode energy may be greater than previously predicted.

[1] Numerical ray tracing indicates that the in situ injection of whistler mode waves of 1 kHz to 4 kHz can be used to illuminate the inner radiation belts and slot region. These results were derived by using the Stanford VLF Ray Tracing Program to simulate sources placed at a total of six points in the inner magnetosphere: L = 1.5, L = 2.0, and L = 2.5 at two geomagnetic latitudes, the equator and a latitude of 20°along each field line. The results demonstrate that an in situ source, by varying the frequency of the injected waves, can illuminate L shells both higher and lower than the source site, with wave frequencies below (above) the local lower hybrid resonance, f LHR , moving to higher (lower) L shells. Accounting for the limitations that would be imposed by a practical antenna immersed in the magnetospheric medium restricts the radiating wave frequency, f, to 0.9 f LHR F < (f LHR + 1 kHz), and the wave normal angle at injection to no farther than 3°from the resonance cone. Even after accounting for these restrictions, it requires only three in situ sources placed at the above locations to illuminate 1.4 ' L ' 2.7, which comprises the bulk of the inner radiation belt.Citation: Kulkarni, P., U. S. Inan, and T. F. Bell (2006), Whistler mode illumination of the plasmaspheric resonant cavity via in situ injection of ELF/VLF waves,