A medium and high-frequency antenna array for radar and radio imaging of the ionosphere is planne... more A medium and high-frequency antenna array for radar and radio imaging of the ionosphere is planned for installation in Aguadilla, Puerto Rico. Science goals include the study of space weather, radio propagation, meteors, lightning, and plasma physics. Radio imaging is ideal for the study of stimulated ionospheric radio emissions, such as those induced by the Arecibo Observatory high-power HF radio transmitter, which is likely to be restored to operation in the near future. The array will be complemented by a wide variety of instruments fielded by collaborators, and will be a rich source of student projects at all levels.
Since the fall of the Arecibo 305[Formula: see text]m telescope platform on 2020 December 1, ther... more Since the fall of the Arecibo 305[Formula: see text]m telescope platform on 2020 December 1, there has been much discussion of building a new Arecibo telescope or rebuilding the facility that was destroyed. In the collapse, the top of the three platform support towers was sheared off, and the feed arm fell free from the swinging platform and destroyed 25% of the dish. Fortunately, the Control Building, the home of the computers, spectrometers, masers, atomic clocks, 430[Formula: see text]MHz Klystrons, etc., was spared. By replacing the main dish support cables and resurfacing with coarse mesh, the main dish can be repaired as a reflector [Formula: see text] operation. By replacing the damaged aluminum panels to make the dish whole again, RF operations at up to 500[Formula: see text]MHz can be resumed. In this paper, we outline the steps that can be taken to restore High Frequency (HF, 3–30[Formula: see text]MHz) ionospheric heating, 430[Formula: see text]MHz ionospheric incoherent ...
Puerto Rico (PR) was struck by the Extreme Weather System (EWS) category IV hurricane Maria on Se... more Puerto Rico (PR) was struck by the Extreme Weather System (EWS) category IV hurricane Maria on Sep 20, 2017. This work presents a preliminary analysis of the marked variability in the upper atmosphere observed by instruments at Arecibo Observatory (AO), PR. During various stages of Maria, these instruments detected distinct, altitude-dependent thermospheric responses in an extensive area from the center of this EWS. On the night of Sept 17, 2017, when Maria was about 850 km southeast from AO, an all-sky imager registered wavefronts propagating northwestward (away from the convective source) in three wavelengths. A photometer detected a decrease in the OI5577 (~ 95km) before Maria's landfall. Ionosonde data acquired during Maria's approach and landfall indicate an intensification of the tidal amplitudes near the peak of the Fregion (~300 km) during nighttime. As the EWS Maria progressed northward, a VLF receiver operating at the AO confirmed fluctuations in the D-region ionos...
This work presents the results for the 7320A line width data acquired from April to October of 20... more This work presents the results for the 7320A line width data acquired from April to October of 2008 at Arecibo (18.35N, 66.75W) using a CCD array detection with a high-spectral resolution Fabry-Perot interferometer. The excited O+(2P) atom is formed by photoionization or electron impact with energy in excess of 18.6EV (< 666Å). With a lifetime of 4.57s in the upper
Optical observations of transient luminous events and remote-sensing of the lower ionosphere with... more Optical observations of transient luminous events and remote-sensing of the lower ionosphere with low-frequency radio waves have demonstrated that thunderstorms and lightning can have substantial impacts in the nighttime ionospheric D region. However, it remains a challenge to quantify such effects in the daytime lower ionosphere. The wealth of electron density data acquired over the years by the Arecibo Observatory incoherent scatter radar (ISR) with high vertical spatial resolution (300-m in the present study), combined with its tropical location in a region of high lightning activity, indicate a potentially transformative pathway to address this issue. Through a systematic survey, we show that daytime sudden electron density changes registered by Arecibo’s ISR during thunderstorm times are on average different than the ones happening during fair weather conditions (driven by other external factors). These changes typically correspond to electron density depletions in the D and E ...
Neste trabalho e apresentado um modelo semi-empirico de ventos neutros termosfericos medios longi... more Neste trabalho e apresentado um modelo semi-empirico de ventos neutros termosfericos medios longitudinais para periodos de baixas atividades solar e geomagnetica com dependencia em hora local, dia do ano e latitude geografica para 250 km de altitude. O modelo e denominado de SEATWIM (sigla em ingles para Semi Empirical Averaged Termospheric Wind Model ) valido para periodos de baixa atividade solar e geomagnetica. O SEATWIM foi construido a partir de uma analise estatistica dos dados observados in situ obtidos pelo satelite UARS ( Upper Atmosphere Research Satllite ) por meio da carga util WINDII ( Wind Imaging Interferometer ), onde os valores representativos para 250 km sao obtidos pela media integrada em altitude entre 205 km e 275 km, e, a partir de uma analise estatistico-espectral, foi extraido comportamento diario e sazonal distribuidos em latitude geografica. O modelo proposto exibe uma boa concordância em relacao a climatologia dos dados observados pelo satelite para as com...
Optical observations of transient luminous events and remote-sensing of the lower ionosphere with... more Optical observations of transient luminous events and remote-sensing of the lower ionosphere with low-frequency radio waves have demonstrated that thunderstorms and lightning can have substantial impacts in the nighttime ionospheric D region. However, it remains a challenge to quantify such effects in the daytime lower ionosphere. The wealth of electron density data acquired over the years by the Arecibo Observatory incoherent scatter radar (ISR) with high vertical spatial resolution (300-m in the present study), combined with its tropical location in a region of high lightning activity, indicate a potentially transformative pathway to address this issue. Through a systematic survey, we show that daytime sudden electron density changes registered by Arecibo’s ISR during thunderstorm times are on average different than the ones happening during fair weather conditions (driven by other external factors). These changes typically correspond to electron density depletions in the D and E ...
In the last couple of decades, substantial research has been dedicated to understanding the coupl... more In the last couple of decades, substantial research has been dedicated to understanding the coupling between atmospheric regions. Research on transient luminous events (TLEs) appeared and quickly intensified with the promise of TLEs serving as an optical remote sensing tool of the mesosphere and lower ionosphere. However, to date it remains challenging to obtain quantitative estimates of electron density changes in the ionospheric D region due to underlying lightning and thunderstorms. Arecibo’s incoherent scatter radar (ISR) capabilities for measuring ionospheric electron density with high resolution (300-m spatial resolution in the present study), combined with its tropical location in a region of high lightning incidence rates, indicate a potentially transformative pathway to address this problem. Through a systematic survey, we show that sudden electron density changes registered by Arecibo’s ISR during thunderstorm times are on average different than the ones happening during f...
2021 XXXIVth General Assembly and Scientific Symposium of the International Union of Radio Science (URSI GASS)
The energetic particle precipitation strongly affects the lower ionosphere, since these particles... more The energetic particle precipitation strongly affects the lower ionosphere, since these particles play an important role in the production of ionic pairs. Numerical simulations of ionospheric cosmic noise absorption at 30 MHz are shown, for the South Atlantic Magnetic Anomaly (SAMA) region. Simulations were carried out for aeronomic conditions of Cachoeira Paulista (22,50°S; 45,00°W) Simulation analysis were done for nighttime hours and moderate solar activity conditions. The simulations here presented include precipitation processes of electrons and galactic cosmic rays, photo-ionization processes, and processes of ionospheric absorption of cosmic noise. Also, the simulations take into account chemical equilibrium conditions for 25 positive ions and 10 negative ions described by 175 chemical reactions. Height profiles of cosmic noise absorption and its response to different characteristic energy levels (energy spectrum) and different ranges of energy of the precipitating electron flux were studied. As expected, absorption increases with precipitating electron flux and characteristic energy. An interesting feature observed is the presence of two peaks of absorption at different heights. For a fixed value of characteristic energy, an increase in the precipitating electron flux raises the height of the lower peak and lowers the height of the upper peak. Our results also show that for a fixed range of energy of precipitating electron flux, the heights of both absorption peaks decrease with the increase of the characteristic energy.
. Intermediate layers (ILs) are regions of enhanced electron density located in the ionospheric v... more . Intermediate layers (ILs) are regions of enhanced electron density located in the ionospheric valley that extends from the peak altitude of the daytime E-region to the bottom side of the F-region. This work presents the daytime behavior of the ILs parameters (the virtual height - h’IL, and the top frequency - ftIL) over the low latitude region of Cachoeria Paulista (CP, 22.42° S; 45° W, I: −34.4°) for the deepest solar minimum of the last 500 years. In such a unique condition, this research reveals for the first time the ILs' quiet state seasonal behavior as well as its responses to moderate changes in the geomagnetic activity. The main results show that even small variations of geomagnetic activity (quantified by the planetary Kp index) are able to modify the dynamics of the ILs parameters. For the first time, it was observed that during the summer, the h’IL decrease rapidly with the increase of geomagnetic activity mainly in the early morning hours. In the following hours, a smoothed rise of the IL was found in all seasons analyzed. Regarding to frequency, it was observed that after 12:00 LT, there is a tendency of it decreased with the increase of the magnetic disturbances, being this characteristic more intense after 16:00 LT, except in the equinox, when little or no response was found during all the interval analyzed. In addition, it stands out that the annual periodicity of the ftIL was observed while the h’IL presents semiannual component.
A medium and high-frequency antenna array for radar and radio imaging of the ionosphere is planne... more A medium and high-frequency antenna array for radar and radio imaging of the ionosphere is planned for installation in Aguadilla, Puerto Rico. Science goals include the study of space weather, radio propagation, meteors, lightning, and plasma physics. Radio imaging is ideal for the study of stimulated ionospheric radio emissions, such as those induced by the Arecibo Observatory high-power HF radio transmitter, which is likely to be restored to operation in the near future. The array will be complemented by a wide variety of instruments fielded by collaborators, and will be a rich source of student projects at all levels.
Since the fall of the Arecibo 305[Formula: see text]m telescope platform on 2020 December 1, ther... more Since the fall of the Arecibo 305[Formula: see text]m telescope platform on 2020 December 1, there has been much discussion of building a new Arecibo telescope or rebuilding the facility that was destroyed. In the collapse, the top of the three platform support towers was sheared off, and the feed arm fell free from the swinging platform and destroyed 25% of the dish. Fortunately, the Control Building, the home of the computers, spectrometers, masers, atomic clocks, 430[Formula: see text]MHz Klystrons, etc., was spared. By replacing the main dish support cables and resurfacing with coarse mesh, the main dish can be repaired as a reflector [Formula: see text] operation. By replacing the damaged aluminum panels to make the dish whole again, RF operations at up to 500[Formula: see text]MHz can be resumed. In this paper, we outline the steps that can be taken to restore High Frequency (HF, 3–30[Formula: see text]MHz) ionospheric heating, 430[Formula: see text]MHz ionospheric incoherent ...
Puerto Rico (PR) was struck by the Extreme Weather System (EWS) category IV hurricane Maria on Se... more Puerto Rico (PR) was struck by the Extreme Weather System (EWS) category IV hurricane Maria on Sep 20, 2017. This work presents a preliminary analysis of the marked variability in the upper atmosphere observed by instruments at Arecibo Observatory (AO), PR. During various stages of Maria, these instruments detected distinct, altitude-dependent thermospheric responses in an extensive area from the center of this EWS. On the night of Sept 17, 2017, when Maria was about 850 km southeast from AO, an all-sky imager registered wavefronts propagating northwestward (away from the convective source) in three wavelengths. A photometer detected a decrease in the OI5577 (~ 95km) before Maria's landfall. Ionosonde data acquired during Maria's approach and landfall indicate an intensification of the tidal amplitudes near the peak of the Fregion (~300 km) during nighttime. As the EWS Maria progressed northward, a VLF receiver operating at the AO confirmed fluctuations in the D-region ionos...
This work presents the results for the 7320A line width data acquired from April to October of 20... more This work presents the results for the 7320A line width data acquired from April to October of 2008 at Arecibo (18.35N, 66.75W) using a CCD array detection with a high-spectral resolution Fabry-Perot interferometer. The excited O+(2P) atom is formed by photoionization or electron impact with energy in excess of 18.6EV (< 666Å). With a lifetime of 4.57s in the upper
Optical observations of transient luminous events and remote-sensing of the lower ionosphere with... more Optical observations of transient luminous events and remote-sensing of the lower ionosphere with low-frequency radio waves have demonstrated that thunderstorms and lightning can have substantial impacts in the nighttime ionospheric D region. However, it remains a challenge to quantify such effects in the daytime lower ionosphere. The wealth of electron density data acquired over the years by the Arecibo Observatory incoherent scatter radar (ISR) with high vertical spatial resolution (300-m in the present study), combined with its tropical location in a region of high lightning activity, indicate a potentially transformative pathway to address this issue. Through a systematic survey, we show that daytime sudden electron density changes registered by Arecibo’s ISR during thunderstorm times are on average different than the ones happening during fair weather conditions (driven by other external factors). These changes typically correspond to electron density depletions in the D and E ...
Neste trabalho e apresentado um modelo semi-empirico de ventos neutros termosfericos medios longi... more Neste trabalho e apresentado um modelo semi-empirico de ventos neutros termosfericos medios longitudinais para periodos de baixas atividades solar e geomagnetica com dependencia em hora local, dia do ano e latitude geografica para 250 km de altitude. O modelo e denominado de SEATWIM (sigla em ingles para Semi Empirical Averaged Termospheric Wind Model ) valido para periodos de baixa atividade solar e geomagnetica. O SEATWIM foi construido a partir de uma analise estatistica dos dados observados in situ obtidos pelo satelite UARS ( Upper Atmosphere Research Satllite ) por meio da carga util WINDII ( Wind Imaging Interferometer ), onde os valores representativos para 250 km sao obtidos pela media integrada em altitude entre 205 km e 275 km, e, a partir de uma analise estatistico-espectral, foi extraido comportamento diario e sazonal distribuidos em latitude geografica. O modelo proposto exibe uma boa concordância em relacao a climatologia dos dados observados pelo satelite para as com...
Optical observations of transient luminous events and remote-sensing of the lower ionosphere with... more Optical observations of transient luminous events and remote-sensing of the lower ionosphere with low-frequency radio waves have demonstrated that thunderstorms and lightning can have substantial impacts in the nighttime ionospheric D region. However, it remains a challenge to quantify such effects in the daytime lower ionosphere. The wealth of electron density data acquired over the years by the Arecibo Observatory incoherent scatter radar (ISR) with high vertical spatial resolution (300-m in the present study), combined with its tropical location in a region of high lightning activity, indicate a potentially transformative pathway to address this issue. Through a systematic survey, we show that daytime sudden electron density changes registered by Arecibo’s ISR during thunderstorm times are on average different than the ones happening during fair weather conditions (driven by other external factors). These changes typically correspond to electron density depletions in the D and E ...
In the last couple of decades, substantial research has been dedicated to understanding the coupl... more In the last couple of decades, substantial research has been dedicated to understanding the coupling between atmospheric regions. Research on transient luminous events (TLEs) appeared and quickly intensified with the promise of TLEs serving as an optical remote sensing tool of the mesosphere and lower ionosphere. However, to date it remains challenging to obtain quantitative estimates of electron density changes in the ionospheric D region due to underlying lightning and thunderstorms. Arecibo’s incoherent scatter radar (ISR) capabilities for measuring ionospheric electron density with high resolution (300-m spatial resolution in the present study), combined with its tropical location in a region of high lightning incidence rates, indicate a potentially transformative pathway to address this problem. Through a systematic survey, we show that sudden electron density changes registered by Arecibo’s ISR during thunderstorm times are on average different than the ones happening during f...
2021 XXXIVth General Assembly and Scientific Symposium of the International Union of Radio Science (URSI GASS)
The energetic particle precipitation strongly affects the lower ionosphere, since these particles... more The energetic particle precipitation strongly affects the lower ionosphere, since these particles play an important role in the production of ionic pairs. Numerical simulations of ionospheric cosmic noise absorption at 30 MHz are shown, for the South Atlantic Magnetic Anomaly (SAMA) region. Simulations were carried out for aeronomic conditions of Cachoeira Paulista (22,50°S; 45,00°W) Simulation analysis were done for nighttime hours and moderate solar activity conditions. The simulations here presented include precipitation processes of electrons and galactic cosmic rays, photo-ionization processes, and processes of ionospheric absorption of cosmic noise. Also, the simulations take into account chemical equilibrium conditions for 25 positive ions and 10 negative ions described by 175 chemical reactions. Height profiles of cosmic noise absorption and its response to different characteristic energy levels (energy spectrum) and different ranges of energy of the precipitating electron flux were studied. As expected, absorption increases with precipitating electron flux and characteristic energy. An interesting feature observed is the presence of two peaks of absorption at different heights. For a fixed value of characteristic energy, an increase in the precipitating electron flux raises the height of the lower peak and lowers the height of the upper peak. Our results also show that for a fixed range of energy of precipitating electron flux, the heights of both absorption peaks decrease with the increase of the characteristic energy.
. Intermediate layers (ILs) are regions of enhanced electron density located in the ionospheric v... more . Intermediate layers (ILs) are regions of enhanced electron density located in the ionospheric valley that extends from the peak altitude of the daytime E-region to the bottom side of the F-region. This work presents the daytime behavior of the ILs parameters (the virtual height - h’IL, and the top frequency - ftIL) over the low latitude region of Cachoeria Paulista (CP, 22.42° S; 45° W, I: −34.4°) for the deepest solar minimum of the last 500 years. In such a unique condition, this research reveals for the first time the ILs' quiet state seasonal behavior as well as its responses to moderate changes in the geomagnetic activity. The main results show that even small variations of geomagnetic activity (quantified by the planetary Kp index) are able to modify the dynamics of the ILs parameters. For the first time, it was observed that during the summer, the h’IL decrease rapidly with the increase of geomagnetic activity mainly in the early morning hours. In the following hours, a smoothed rise of the IL was found in all seasons analyzed. Regarding to frequency, it was observed that after 12:00 LT, there is a tendency of it decreased with the increase of the magnetic disturbances, being this characteristic more intense after 16:00 LT, except in the equinox, when little or no response was found during all the interval analyzed. In addition, it stands out that the annual periodicity of the ftIL was observed while the h’IL presents semiannual component.
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Papers by Christiano Brum