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The very first use of the solar eclipse to study the ionosphere was done in 1912 at a wavelength of 5,500 meters. Since that time, multiple studies have been done at VLF and LF frequencies. Most of these studies were performed at a single receive site with a single transmit location during a single eclipse, thus making it very hard to compare data from separate collections. This paper addresses historical collection efforts, what has been learned about the sun’s influence upon the ionosphere, and the role of neutral corpuscular particles ionizing the ionosphere. Questions raised by the above will be addressed. A planned crowdsource effort will then be described that will attempt to address and answer questions raised by having multiple receivers all reporting on signals transmitted by the same VLF/LF stations. There are two approaches to the crowdsource collection. One approach uses the SuperSID network that is already reporting on changes in propagation of signals from VLF stations. The other approach uses a receiver and antenna based upon an instrumentation amplifier chip and a smart phone as a software defined radio. The later approach will be detailed.
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On the Development of the SAMI2 Ionosphere Model
The development of the ionosphere model SAMI2 at the Naval Research Laboratory (NRL) is described. The genesis of the code and the adversities we faced in developing the model are described. The evolution of the numerical algorithms used is discussed as well as the decision to open-source the code. An example of a new discovery made with the code, the formation of an electron `hole' in the nighttime, high-altitude, low-latitude ionosphere, is given.
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- Award ID(s):
- 1931415
- PAR ID:
- 10378382
- Date Published:
- Journal Name:
- Perspectives of earth and space scientists
- ISSN:
- 2637-6989
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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Korea Polar Research Institute (KOPRI) installed an ionospheric sounding radar system called Vertical Incidence Pulsed Ionospheric Radar (VIPIR) at Jang Bogo Station (JBS) in 2015 in order to routinely monitor the state of the ionosphere in the auroral oval and polar cap regions. Since 2017, after two-year test operation, it has been continuously operated to produce various ionospheric parameters. In this article, we will introduce the characteristics of the JBS-VIPIR observations and possible applications of the data for the study on the polar ionosphere. The JBS-VIPIR utilizes a log periodic transmit antenna that transmits 0.5–25 MHz radio waves, and a receiving array of 8 dipole antennas. It is operated in the Dynasonde B-mode pulse scheme and utilizes the 3-D inversion program, called NeXtYZ, for the data acquisition and processing, instead of the conventional 1-D inversion procedure as used in the most of digisonde observations. The JBS-VIPIR outputs include the height profiles of the electron density, ionospheric tilts, and ion drifts with a 2-minute temporal resolution in the bottomside ionosphere. With these observations, possible research applications will be briefly described in combination with other observations for the aurora, the neutral atmosphere and the magnetosphere simultaneously conducted at JBS.more » « less
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Abstract Ultralow frequency (ULF) electromagnetic waves are regularly detected by satellites near the plasmapause during substorms. Usually, the small‐scale waves are observed embedded in the large‐scale, quasi‐stationary electric field. We suggest that the small‐scale waves are generated in the ionosphere by the interactions between the large‐scale field and irregularities in the ionospheric density/conductivity. Under certain conditions, these waves can be trapped in the global magnetospheric resonator and amplified by the positive feedback interactions with the ionosphere. To verify this hypothesis, we model with a two‐fluid magnetohydrodynamics code structure and amplitude of the ULF waves simultaneously observed near the plasmapause by the Defense Meteorological Satellite Program satellite at low altitudes and the Combined Release and Radiation Effects satellite at high altitudes. Simulations reproduce in good, quantitative detail the structure and amplitude of the observed waves. In particular, simulations reproduce a “spiky” character of the electric field observed by the Defense Meteorological Satellite Program satellite at low altitude, which is a characteristic feature of ULF waves produced by the ionospheric feedback instability.more » « less
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We present FARR (Finite-difference time-domain ARRay), an open source, high-performance, finite-difference time-domain (FDTD) code. FARR is specifically designed for modeling radio wave propagation in collisional, magnetized plasmas like those found in the Earth’s ionosphere. The FDTD method directly solves Maxwell’s equations and captures all features of electromagnetic propagation, including the effects of polarization and finite-bandwidth wave packets. By solving for all vector field quantities, the code can work in regimes where geometric optics is not applicable. FARR is able to model the complex interaction of electromagnetic waves with multi-scale ionospheric irregularities, capturing the effects of scintillation caused by both refractive and diffractive processes. In this paper, we provide a thorough description of the design and features of FARR. We also highlight specific use cases for future work, including coupling to external models for ionospheric densities, quantifying HF/VHF scintillation, and simulating radar backscatter. The code is validated by comparing the simulated wave amplitudes in a slowly changing, magnetized plasma to the predicted amplitudes using the WKB approximation. This test shows good agreement between FARR and the cold plasma dispersion relations for O, X, R, and L modes, while also highlighting key differences from working in the time-domain. Finally, we conclude by comparing the propagation path of an HF pulse reflecting from the bottomside ionosphere. This path compares well to ray tracing simulations, and demonstrates the code’s ability to address realistic ionospheric propagation problems.more » « less
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ami2py is a Python module that runs the SAMI2 (Sami2 is Another Model of the Ionosphere) ionospheric model, as well as load and archive the results. SAMI2 is a model developed by the Naval Research Laboratory to simulate the motions of plasma in a two-dimensional ionospheric environment along a dipole magnetic field. SAMI2 solves for the chemical and dynamical evolution of seven ion species in this environment (H+ , He+ , N+ , O+ , N+ 2 , NO , and O2 ). The Python implementation allows for additional modifications to the empirical models within SAMI2, including the exospheric temperature in the empirical thermosphere and the input of E×B ion drifts. The code is open source and available to the community on GitHub. The work here discusses the implementation and use of sami2py, including integration with the pysat ecosystem and the growin python package for ionospheric calculations. As part of the Application Usability Level (AUL) framework, we will discuss the usability of this code in terms of several ionospheric applications.more » « less
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Accepted Manuscript1.0
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