Abstract On 21 August 2017, a total solar eclipse traversed the continental United States and caused large‐scale changes in ionospheric densities. These were detected as changes in medium‐ and high‐frequency radio propagation by the Solar Eclipse QSO Party citizen science experiment organized by the Ham Radio Science Citizen Investigation (hamsci.org). This is the first eclipse‐ionospheric study to make use of measurements from a citizen‐operated, global‐scale HF propagation network and develop tools for comparison to a physics‐based model ionosphere. Eclipse effects were observed ±0.3 hr on 1.8 MHz, ±0.75 hr on 3.5 and 7 MHz, and ±1 hr on 14 MHz and are consistent with eclipse‐induced ionospheric densities. Observations were simulated using the PHaRLAP raytracing toolkit in conjunction with the eclipsed SAMI3 ionospheric model. Model results suggest 1.8, 3.5, and 7 MHz refracted at h ≥125 km altitude with elevation angles θ ≥22°, while 14 MHz signals refracted at h < 125 km with elevation angles θ < 10°.
SAMI3 (Sami3 is Also a Model of the Ionosphere) is a seamless, three-dimensional, physics-based model of the ionosphere (Huba et al, 2008). It is based on SAMI2, a two-dimensional model of the ionosphere (Huba et al., 2000).
SAMI3 models the plasma and chemical evolution of seven ion species (H⁺, He⁺, N⁺, O⁺, N⁺₂, NO⁺ and O⁺₂). The temperature equation is solved for three ion species (H⁺, He⁺ and O⁺) and for the electrons. Ion inertia is included in the ion momentum equation for motion along the geomagnetic field. This is important in modeling the topside ionosphere and plasmasphere where the plasma becomes collisionless.
SAMI3 includes 21 chemical reactions and radiative recombination, and uses a nonorthogonal, nonuniform, fixed grid for the magnetic latitude range +/- 89 degrees..
Drivers Neutral composition, temperature, and winds: NRLMSISE00 (Picone et al., 2002) and HWM14 (Drob et al., 2015). Solar radiation: Flare Irradiance Spectral Model version 2 (FISM v2) Magnetic field: Richmond apex model [Richmond, 1995]. Neutral wind dynamo electric field: Determined from the solution of a 2D potential equation [Huba et at., 2008]. For the SAMI3/Weimer configuration: High latitude electric field: calculated from the empirical Weimer model for the potential. For the SAMI3/AMPERE configuration: High latitude electric field: calculated using the Magnetosphere-Ionosphere Coupling solver (MIX) developed by Merkin and Lyon (2010). The inputs to MIX are SAMI3's internal conductances, plus field-aligned current observations from Active Magnetosphere and Planetary Electrodynamics Response Experiment (AMPERE), derived from the 66+ satellite Iridium NEXT constellation's engineering magnetometer data. This potential calculation is described in Chartier et al (2022).
For ease of use, SAMI3 output is remapped to a regular grid using the Earth System Modeling Framework by Hill et al (2004)
The physical mechanism of wave‐particle resonances in a curved magnetic field is investigated. Specifically, the energy exchange process between a wave and resonant curvature drifting particles is discussed (i.e., ω∼k⋅Vc, where Vc = v2∥/RcΩ is the curvature drift, Rc is the radius of curvature of the magnetic field, and Ω is the cyclotron frequency). A general expression for the wave damping/growth rate is derived based upon physical arguments. The theory is applied to the lower‐hybrid‐drift instability and nonlinear consequences are discussed.
The lower‐hybrid‐drift instability has been proposed as a mechanism to generate small‐scale density and 100 Hz electric field fluctuations in the nightside Venus ionosphere [ Huba , 1992]. The primary purpose of this paper is to compare this theory with observations of density irregularities. Marginal stability boundaries (γ = 0) for the lower‐hybrid‐drift instability and the occurrence of small‐scale density fluctuations are presented as a function of magnetic field B and density n . For density gradient scale lengths in the range 2–10 km, 80–85% of the density fluctuations lie in the unstable B/n parameter regime (γ > 0). A secondary purpose of the paper is to present stability boundaries for the onset of instability at a wavelength for which the Pioneer Venus Orbiter (PVO) could measure a Doppler‐shifted frequency of 100 Hz. The conditions on B and n for instability in this situation are more stringent than those for marginal stability, especially at low densities ( n ≤ 5 × 10 3 cm −3 ). In general, the instability is most likely to be generated in regions of low β: high magnetic field strength and low density, as found in ionospheric holes or troughs.
By transferring energy from pickup ions in a rocket exhaust plume to EM waves in the ionosphere, the first demonstration of rocket exhaust driven amplification (REDA) of whistler mode waves was achieved on 26 May 2020. The source of coherent VLF waves was the Navy NML Transmitter at 25.2 kHz located in La Moore, South Dakota. A region of the topside ionosphere at 480 km altitude was converted into an amplifying medium with a 60 second firing of the Cygnus BT-4 engine. The rocket exhaust was injected as a neutral cloud moving perpendicular to field lines that connected the NML transmitter to the VLF Radio Receiver Instrument (RRI) on e-POP/SWARM-E at 1080 km altitude. Charge exchange between the ambient O+ ions and the hypersonic water molecules in the exhaust produced an active plasma media with H2O+ ions in a ring-beam velocity distribution. The 25.2 kHz VLF signal from NML was amplified by 30 dB for a period 87 seconds as observed with the electric fields measurements by the RRI. A secondary source of coherent ELF waves was amplified by 50 dB relative to a 300 Hz signal before the engine burn. The 300 Hz ELF waves are of unknown origin but they were related to harmonics of 100 Hz recorded by the RRI more the 600 seconds before the Cygnus burn. Extremely strong coherent emissions and quasi-periodic bursts were observed in the 300 to 310 Hz frequency range for 200 seconds after the release. The excitation of a ELF whistler cavity may have lasted longer but the orbit of the SWARM-E/e-POP moved the RRI sensor away from the wave emission region. Propagation analysis suggests that the 25.2 kHz VLF waves are less likely to be trapped in plasmaspheric ducts than the 300 Hz ELF band. The 50 dB amplification of the ELF modes may be the result of multi-hop whistler modes echoing between geomagnetic-conjugate hemispheres, gaining energy by cyclotron resonance with the radiation belt electrons.
Summary form only given. Conduction and opening processes of plasma opening switches (POS) are examined with the aid of numerical simulations. In a POS, a plasma initially bridges a small axial region of the transmission line of an inductive energy storage generator. A section of vacuum transmission line then connects the POS region to a load. The plasma initially carries the generator current, allowing no current to flow to the load. Modifications to the plasma or to the current distribution in the plasma eventually open the POS, allowing power to flow to the load. These modifications can occur by a variety of different mechanisms: by plasma deformation and displacement, by magnetic field transport, or by a combination of such effects. Deformation and displacement are carried out by J/spl times/B forces and by electrostatic forces (ion erosion) associated with electron vortices. Magnetic field penetration can occur by electron-magneto-hydrodynamic (EMH) effects or resistive diffusion. Both particle-in-cell (PIC) and MHD codes are used to demonstrate many of these effects. In these simulations, a wide range of plasma densities (n/sub e/=5/spl times/10/sup 12/-5/spl times/10/sup 15/ cm/sup -3/) are examined.
SAMI3 (Sami3 is Also a Model of the Ionosphere) is a seamless, three-dimensional, physics-based model of the ionosphere (Huba et al, 2008). It is based on SAMI2, a two-dimensional model of the ionosphere (Huba et al., 2000).
SAMI3 models the plasma and chemical evolution of seven ion species (H⁺, He⁺, N⁺, O⁺, N⁺₂, NO⁺ and O⁺₂). The temperature equation is solved for three ion species (H⁺, He⁺ and O⁺) and for the electrons. Ion inertia is included in the ion momentum equation for motion along the geomagnetic field. This is important in modeling the topside ionosphere and plasmasphere where the plasma becomes collisionless.
SAMI3 includes 21 chemical reactions and radiative recombination, and uses a nonorthogonal, nonuniform, fixed grid for the magnetic latitude range +/- 89 degrees..
Drivers Neutral composition, temperature, and winds: NRLMSISE00 (Picone et al., 2002) and HWM14 (Drob et al., 2015). Solar radiation: Flare Irradiance Spectral Model version 2 (FISM v2) Magnetic field: Richmond apex model [Richmond, 1995]. Neutral wind dynamo electric field: Determined from the solution of a 2D potential equation [Huba et at., 2008]. For the SAMI3/Weimer configuration: High latitude electric field: calculated from the empirical Weimer model for the potential. For the SAMI3/AMPERE configuration: High latitude electric field: calculated using the Magnetosphere-Ionosphere Coupling solver (MIX) developed by Merkin and Lyon (2010). The inputs to MIX are SAMI3's internal conductances, plus field-aligned current observations from Active Magnetosphere and Planetary Electrodynamics Response Experiment (AMPERE), derived from the 66+ satellite Iridium NEXT constellation's engineering magnetometer data. This potential calculation is described in Chartier et al (2022).
For ease of use, SAMI3 output is remapped to a regular grid using the Earth System Modeling Framework by Hill et al (2004)
SAMI3 (Sami3 is Also a Model of the Ionosphere) is a seamless, three-dimensional, physics-based model of the ionosphere (Huba et al, 2008). It is based on SAMI2, a two-dimensional model of the ionosphere (Huba et al., 2000).
SAMI3 models the plasma and chemical evolution of seven ion species (H⁺, He⁺, N⁺, O⁺, N⁺₂, NO⁺ and O⁺₂). The temperature equation is solved for three ion species (H⁺, He⁺ and O⁺) and for the electrons. Ion inertia is included in the ion momentum equation for motion along the geomagnetic field. This is important in modeling the topside ionosphere and plasmasphere where the plasma becomes collisionless.
SAMI3 includes 21 chemical reactions and radiative recombination, and uses a nonorthogonal, nonuniform, fixed grid for the magnetic latitude range +/- 89 degrees..
Drivers Neutral composition, temperature, and winds: NRLMSISE00 (Picone et al., 2002) and HWM14 (Drob et al., 2015). Solar radiation: Flare Irradiance Spectral Model version 2 (FISM v2) Magnetic field: Richmond apex model [Richmond, 1995]. Neutral wind dynamo electric field: Determined from the solution of a 2D potential equation [Huba et at., 2008]. For the SAMI3/Weimer configuration: High latitude electric field: calculated from the empirical Weimer model for the potential. For the SAMI3/AMPERE configuration: High latitude electric field: calculated using the Magnetosphere-Ionosphere Coupling solver (MIX) developed by Merkin and Lyon (2010). The inputs to MIX are SAMI3's internal conductances, plus field-aligned current observations from Active Magnetosphere and Planetary Electrodynamics Response Experiment (AMPERE), derived from the 66+ satellite Iridium NEXT constellation's engineering magnetometer data. This potential calculation is described in Chartier et al (2022).
For ease of use, SAMI3 output is remapped to a regular grid using the Earth System Modeling Framework by Hill et al (2004)
SAMI3 (Sami3 is Also a Model of the Ionosphere) is a seamless, three-dimensional, physics-based model of the ionosphere (Huba et al, 2008). It is based on SAMI2, a two-dimensional model of the ionosphere (Huba et al., 2000).
SAMI3 models the plasma and chemical evolution of seven ion species (H⁺, He⁺, N⁺, O⁺, N⁺₂, NO⁺ and O⁺₂). The temperature equation is solved for three ion species (H⁺, He⁺ and O⁺) and for the electrons. Ion inertia is included in the ion momentum equation for motion along the geomagnetic field. This is important in modeling the topside ionosphere and plasmasphere where the plasma becomes collisionless.
SAMI3 includes 21 chemical reactions and radiative recombination, and uses a nonorthogonal, nonuniform, fixed grid for the magnetic latitude range +/- 89 degrees..
Drivers Neutral composition, temperature, and winds: NRLMSISE00 (Picone et al., 2002) and HWM14 (Drob et al., 2015). Solar radiation: Flare Irradiance Spectral Model version 2 (FISM v2) Magnetic field: Richmond apex model [Richmond, 1995]. Neutral wind dynamo electric field: Determined from the solution of a 2D potential equation [Huba et at., 2008]. For the SAMI3/Weimer configuration: High latitude electric field: calculated from the empirical Weimer model for the potential. For the SAMI3/AMPERE configuration: High latitude electric field: calculated using the Magnetosphere-Ionosphere Coupling solver (MIX) developed by Merkin and Lyon (2010). The inputs to MIX are SAMI3's internal conductances, plus field-aligned current observations from Active Magnetosphere and Planetary Electrodynamics Response Experiment (AMPERE), derived from the 66+ satellite Iridium NEXT constellation's engineering magnetometer data. This potential calculation is described in Chartier et al (2022).
For ease of use, SAMI3 output is remapped to a regular grid using the Earth System Modeling Framework by Hill et al (2004)
SAMI3 (Sami3 is Also a Model of the Ionosphere) is a seamless, three-dimensional, physics-based model of the ionosphere (Huba et al, 2008). It is based on SAMI2, a two-dimensional model of the ionosphere (Huba et al., 2000).
SAMI3 models the plasma and chemical evolution of seven ion species (H⁺, He⁺, N⁺, O⁺, N⁺₂, NO⁺ and O⁺₂). The temperature equation is solved for three ion species (H⁺, He⁺ and O⁺) and for the electrons. Ion inertia is included in the ion momentum equation for motion along the geomagnetic field. This is important in modeling the topside ionosphere and plasmasphere where the plasma becomes collisionless.
SAMI3 includes 21 chemical reactions and radiative recombination, and uses a nonorthogonal, nonuniform, fixed grid for the magnetic latitude range +/- 89 degrees..
Drivers Neutral composition, temperature, and winds: NRLMSISE00 (Picone et al., 2002) and HWM14 (Drob et al., 2015). Solar radiation: Flare Irradiance Spectral Model version 2 (FISM v2) Magnetic field: Richmond apex model [Richmond, 1995]. Neutral wind dynamo electric field: Determined from the solution of a 2D potential equation [Huba et at., 2008]. For the SAMI3/Weimer configuration: High latitude electric field: calculated from the empirical Weimer model for the potential. For the SAMI3/AMPERE configuration: High latitude electric field: calculated using the Magnetosphere-Ionosphere Coupling solver (MIX) developed by Merkin and Lyon (2010). The inputs to MIX are SAMI3's internal conductances, plus field-aligned current observations from Active Magnetosphere and Planetary Electrodynamics Response Experiment (AMPERE), derived from the 66+ satellite Iridium NEXT constellation's engineering magnetometer data. This potential calculation is described in Chartier et al (2022).
For ease of use, SAMI3 output is remapped to a regular grid using the Earth System Modeling Framework by Hill et al (2004)
