Search

Spread-F (SF) is a feature that can be visually observed on ionograms when the ionosonde signals are significantly impacted by plasma irregularities in the ionosphere. Depending on the scale of the plasma irregularities, radio waves of different frequencies are impacted differently when the signals pass through the ionosphere. An automated method for detecting SF in ionograms is presented in this study. Through detecting the existence of SF in ionograms, we can help identify instances of plasma irregularities that are potentially affecting the high-frequency radio-wave systems. The ionogram images from Jicamarca observatory in Peru, during the years 2008–2019, are used in this study. Three machine learning approaches have been carried out: supervised learning using Support Vector Machines, and two neural network-based learning methods: autoencoder and transfer learning. Of these three methods, the transfer learning approach, which uses convolutional neural network architectures, demonstrates the best performance. The best existing architecture that is suitable for this problem appears to be the ResNet50. With respect to the training epoch number, the ResNet50 showed the greatest change in the metric values for the key metrics that we were tracking. Furthermore, on a test set of 2050 ionograms, the model based on the ResNet50 architecture provides an accuracy of 89%, recall of 87%, precision of 95%, as well as Area Under the Curve of 96%. The work also provides a labeled data set of around 28,000 ionograms, which is extremely useful for the community for future machine learning studies. We are grateful for the Singapore International Graduate Award that C. Luwanga is a beneficiary of and the NTU start up grant for AC from school of EEE. T.-W. Fang was supported by NSF SWQU grant (AGS 2028032) and NOAA Space Weather Prediction Center. Y.-J. Lee was funded under NSF grant (AGS 1552017).

We report the proposal and results of a low‐cost, easy‐to‐build GPS‐based sensor for detection and monitoring ionospheric irregularities through the detection of amplitude scintillation. The system is based on the Raspberry Pi single‐board computer combined with an Adafruit Ultimate GPS peripheral, which is capable of measuring (at 10‐Hz rate) the intensity of the L1 signals transmitted by GPS satellites. We introduce and discuss results of short‐ and long‐term observations obtained with a prototype of this system deployed in Presidente Prudente, a low magnetic latitude site in Brazil. The deployment and observations were carried out to test the ability of the system to detect ionospheric scintillations and, therefore, monitor the occurrence of ionospheric irregularities associated with equatorial spread F. Our results show that this low‐cost sensor is indeed capable of detecting scintillation events associated with equatorial spread F. Comparison with simultaneous, collocated measurements made by a commercial scintillation monitor are also presented. The joint observations allowed us to quantify the performance of the low‐cost monitor and to identify sources of potential limitations. While the sensor cannot (and it was not intended to) substitute commercial scintillation monitors, the low cost allows its use in studies of ionospheric irregularities (space weather) that require observations made by distributed arrays of small instruments (DASI). Furthermore, the simplicity of the sensor design stimulates its use in educational and citizen science initiatives.

We introduce and analyze the first data from an array of closely spaced Global Positioning System (GPS) scintillation receivers established in the auroral zone in late 2013 to measure spatial and temporal variations in L band signals at 100–1000 m and subsecond scales. The seven receivers of the Scintillation Auroral GPS Array (SAGA) are sited at Poker Flat Research Range, Alaska. The receivers produce 100 s scintillation indices and 100 Hz carrier phase and raw in-phase and quadrature-phase samples. SAGA is the largest existing array with baseline lengths of the ionospheric diffractive Fresnel scale at L band. With an initial array of five receivers, we identify a period of simultaneous amplitude and phase scintillation. We compare SAGA power and phase data with collocated 630.0 nm all-sky images of an auroral arc and incoherent scatter radar electron precipitation measurements, to illustrate how SAGA can be used in multi-instrument observations for subkilometer-scale studies. Key Points A seven-receiver Scintillation Auroral GPS Array (SAGA) is now at Poker Flat, Alaska SAGA is the largest subkilometer array to enable phase/irregularities studies Simultaneous scintillation, auroral arc, and electron precipitation are observed

Made available in DSpace on 2019-09-12T16:53:23Z (GMT). No. of bitstreams: 0 Previous issue date: 2016 Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq) National Space Science Center (NSSC), Chinese Academy of Sciences (CAS) Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP) NSF through Cornell University [AGS-1433968] Neste trabalho, a dependência sazonal do campo elétrico da região E (EEF) no equador de mergulho é examinada. Os campos elétricos zonal leste ( E y ) e vertical diurno ( E z ) são responsáveis ​​pela fenomenologia geral da ionosfera equatorial e de baixa latitude, incluindo o eletrojeto equatorial (EEJ) e sua instabilidade de plasma. Os componentes do campo elétrico são estudados com base em sondagens de radares retroespalhados de longo prazo (348 dias para ambos os sistemas) coletados durante dias calmos geomagnéticos ( Kp ≤ 3+), de 2001 a 2010, no Observatório Espacial de São Luís (SLZ), Brasil (2,33 ° S, 44,20 ° W), e no Rádio Observatório de Jicamarca (JRO), Peru (11,95 ° S, 76,87 ° W ) Entre os resultados, observamos, pela primeira vez, uma diferença sazonal entre o EEF nesses dois setores na América do Sul com base em medições coerentes de radar. O EEF é mais intenso no verão no SLZ, no equinócio no JRO e tem sido altamente variável com a temporada no setor brasileiro em comparação com o setor peruano. Além disso, a variação secular no campo geomagnético e seu efeito na EEJ sobre o Brasil resultou que quanto mais longe está o equador magnético de SLZ, mais tarde a EEJ é observada (10 h LT) e mais cedo termina (16 h LT ) Além disso, o intervalo de tempo de ocorrência do tipo II diminuiu significativamente após o ano de 2004, In this work, the seasonal dependency of the E region electric field (EEF) at the dip equator is examined. The eastward zonal (E-y) and the daytime vertical (E-z) electric fields are responsible for the overall phenomenology of the equatorial and low- latitude ionosphere, including the equatorial electrojet (EEJ) and its plasma instability. The electric field components are studied based on long-term backscatter radars soundings (348 days for both systems) collected during geomagnetic quiet days (Kp

The MF data recorded by the low-altitude satellite DEMETER have been used to survey the MF waves around the Earth. A global map of the MF emissions indicates that there exists a wave activity in the frequency range 2-2.5 MHz above the main powerful VLF ground-based transmitters operating in the frequency range 18-50 kHz. It is shown that this is due to the high-frequency part of whistlers induced by the thunderstorm activity. They can penetrate trough the ionosphere at the locations of the transmitters because these transmitters induce large ionospheric perturbations. This means that an integrated map over several months is able to show these MF emissions above all main VLF transmitters. The discrepancy between intensities of the emissions in winter and summer (in the Northern Hemisphere) is explained by considering the geographic variations of the plasma frequency below the satellite. It is shown that the MF waves spread in longitude in the hemisphere opposite to the VLF transmitters., Centre National d'Etudes Spatiales (CNES); MURI; Stanford University

We have used the radar interferometer technique at Jicamarca to study in detail irregularities with wavelengths of a few kilometers generated in the unstable equatorial electrojet plasma during strong type 1 conditions. In-situ rocket observations of the same instability process are discussed in a companion paper. These large scale primary waves travel essentially horizontally and have large amplitudes. The vertical electron drift velocities driven by the horizontal wave electric fields reach or exceed the ion-acoustic velocity even though the horizontal phase velocity of the wave is considerably smaller. A straightforward extension to the long wavelength regime of the usual linear theory of the electrojet instability explains this and several other observed features of these dominant primary waves.