A device which can overcome certain of the compromises of conventional Faraday rotation methods a... more A device which can overcome certain of the compromises of conventional Faraday rotation methods and at the same time measure the optical phase as well as the polarization is reported. This would be useful for unfolding the Faraday rotation signal using the line-of-sight density along exactly the same path. Preliminary design parameters using a CO2 laser are presented.
We present a statistical analysis of thunderstorm radiofrequency and optical data from the FORTE ... more We present a statistical analysis of thunderstorm radiofrequency and optical data from the FORTE satellite to examine the relationship of strong radiofrequency pulsed emissions to more conventional signals from lightning. The study is built on a FORTE database of intracloud, pulsed radio signals from storms whose geolocation is provided either by coincidence with the FORTE optical imager or by coincidence with ground-based lightning-detection arrays. Intracloud radio emissions with peak power >40 kW in the FORTE low band (26-48 MHz) have unique characteristics compared to weaker emissions, including: Occurring either in isolation or at the start of leader progression, but never within a progressing leader; occurring without light emission detectable with FORTE; occurring in frequent association with a rapid (10 microsec) relaxation of the electric charge; and followed by an upward-progressing leader, in the cases where a leader is initiated. These strong intracloud radio pulses appear to be associated with an intracloud discharge process that is physically distinct from conventional leader progression.
The Los Alamos Sferic Array (EDOT) has recorded over 3.7 million lightning-related fast electric ... more The Los Alamos Sferic Array (EDOT) has recorded over 3.7 million lightning-related fast electric field change data records during April 1 - August 31, 2001 and 2002. The events were detected by three or more stations, allowing for differential-time-of-arrival location determination. The waveforms are characterized with estimated peak currents as well as by event type. Narrow Bipolar Events (NBEs), the VLF/LF signature of Compact Intra-cloud Discharges (CIDs), are generally isolated pulses with identifiable ionospheric reflections, permitting determination of event source altitudes. We briefly review the EDOT characterization of events. The FORTE satellite observes Trans-Ionospheric Pulse Pairs (TIPPs, the VHF satellite signature of CIDs). The subset of coincident EDOT and FORTE CID observations are compared with the total EDOT CID database to characterize the VHF detection efficiency of CIDs. The NBE polarity and altitude are also examined in the context of FORTE TIPP detection. The parameter-dependent detection efficiencies are extrapolated from FORTE orbit to GPS orbit in support of the V-GLASS effort (GPS based global detection of lightning).
Journal of Atmospheric and Terrestrial Physics, Apr 30, 1989
The paper presents an introduction to the use of phase-coherent, multireceiver HF Doppler soundin... more The paper presents an introduction to the use of phase-coherent, multireceiver HF Doppler sounding arrays for measuring the horizontal velocity of traveling ionospheric disturbances (TIDs). The point of departure is the theorem of Pfister (1971) relating ray Doppler to ray zenith angle for a monostatic full reflection sounder. Retaining the simple model of a specular, smooth ionospheric reflector which is deformed by a propagating undulation, the theorem is first generalyzed to bistatic sounding geometry and then the effects of amplitude are included in addition to phase. Next, these results are cast into an algorithm for treating multireceiver phase sounders containing many diverse baselines, in order to obtain an accurate and unambiguous solution in the plane of wave slowness (inverse of velocity). The point spread function of this solution is controlled gy process bandwidth and by array geometry.
The ocean is an important sink for atmospheric carbon dioxide, and the exchange of carbon dioxide... more The ocean is an important sink for atmospheric carbon dioxide, and the exchange of carbon dioxide between the atmosphere and ocean plays a critical role in determining the spatial distribution of atmospheric carbon dioxide. However, there is still a great deal of uncertainty in both magnitude and regional patterns of anthropogenic uptake associated with estimates of oceanic carbon fluxes. Using a recently developed technique, exchange of anthropogenic carbon dioxide across the air-sea interface have been estimated from observations of dissolved inorganic carbon and nutrient concentrations and an Ocean General Circulation Model (OGCM) using a Green's function inverse modeling technique. Previous sensitivity studies have shown that model circulation error is an important source of error in the ocean inversion. In order to address the role of ocean circulation biases, inverse estimates of anthropogenic carbon air-sea gas exchange are presented using basis functions from a suite of seven different OGCM's. The robustness of the ocean inversion will be quantified and the effects of differences between approaches to modeling ocean circulation on the ocean carbon cycle will be explored. These results will be discussed in the context of recent atmospheric inverse estimates.
... Storm Monitoring Using VHF Receivers D. Suszcynsky, A. Jacobson, J. Fitzgerald, C. Rhodes, E.... more ... Storm Monitoring Using VHF Receivers D. Suszcynsky, A. Jacobson, J. Fitzgerald, C. Rhodes, E. Tech, D. Roussel-Dupre Los Alamos National Laboratory Space & Atmospheric Sciences Group,NIS-1 [email protected] 505-665-3119 FORTE Science/Operations Team ...
The oceanic carbon transport and propagation of uncertainties in an ocean inverse scheme are exam... more The oceanic carbon transport and propagation of uncertainties in an ocean inverse scheme are examined in detail. Traditionally, ocean carbon fluxes are estimated using bulk parameterization of air-sea gas exchange and observed air-sea gradients. An alternative approach has been published using ocean interior observations from the WOCE/JGOFS global carbon dioxide survey and an ocean general circulation model in a Green's function based inverse model to constrain the temporally averaged pre-industrial and present-day carbon dioxide fluxes. Thorough understandings of ocean carbon transport and error propagation through the inverse system are critical initial steps in this work. The ocean carbon transport in the model is examined in detail and with a focus on the impact of uncertainty propagation on carbon transport. The potential biases to carbon transport in the inverse scheme due to the technique used to account for biological processes and the impact of propagation of uncertainty in the observations are discussed.
Observations by HF ionospheric sounding of disturbances produced by powerful chemical explosions ... more Observations by HF ionospheric sounding of disturbances produced by powerful chemical explosions (several KT) are described. These experiments were performed at distances of about 30 to 40 km from the explosion point. Because of the amplification due to the atmospheric density decrease with increasing altitude, the acoustic waves from such explosions are characterized by shock waves features when they reach the ionosphere. The development of the disturbance was studied from the lower E region up to the F2 region by using 8 sounding frequencies. It is shown that a blanketing sporadic E layer undergoes small scale fluctuations and becomes semi-transparent after the passage of the disturbance. Several wave fronts with different properties are followed to the F1 region. In the lower E region, the wave induced stratifications on which the radio waves are partially reflected. The echoes totally reflected in the E region undergo an amplitude modulation with a period of about 2 seconds, persisting about 30 minutes. The variations of the total reflection height and of the Doppler frequency shift are most noticeable in the F1 region. The wave loses its shock wave feature in the F2 region and the disturbance signature is then that of a pseudo-sinusoidal wave with a wave length of several tens of kilometers.
A 6-min-period oscillation persisting for an hour has been observed in the ionospheric E region f... more A 6-min-period oscillation persisting for an hour has been observed in the ionospheric E region following a 5-kt chemical explosion on the ground 250 km south of the measurement site. The oscillations' phase velocity in the upper atmosphere is 0.15 km/s at an azimuth 60 W.
Journal of Geophysical Research Atmospheres, Nov 27, 2001
We present long optical and radio frequency (RF) time series of lightning events observed with th... more We present long optical and radio frequency (RF) time series of lightning events observed with the FORTE satellite in January 2000. Each record contains multiple RF and optical impulses. We use the RF signatures to identify the general type of discharge for each impulse according to the discrimination techniques described by Suszcynsky et al. (2000) and reviewed herein. We see a large number of paired, impulsive events in the RF which allow us to study the heights within clouds of several events. We also see that the rate of RF/optical coincidence depends on the type of discharge: nearly 100% of VHF signals from first negative return strokes have an associated optical signal, whereas a mere 50% of impulsive intracloud events appear to have an optical counterpart. While the RF signals from ground strokes clearly coincide with simple optical signals in almost all cases, the intracloud lightning often shows nearly continuous, complicated RF and optical emissions which do not cleanly correlate with one another. The RF and optical pulses do not show a well-defined relationship of intensities, for any lightning type. The observed delay between the RF and optical pulses we interpret as mainly an effect of the scattering experienced by the light as it traverses the cloud. For intracloud lightning, we find no evidence of an intrinsic delay at the source between the onset of the RF and optical signals. Impulsive in-cloud RF events are seen to occur on average every 0.9 ms during a flash.
The Los Alamos National Laboratory/Sandia National Laboratory FORTE satellite is described and it... more The Los Alamos National Laboratory/Sandia National Laboratory FORTE satellite is described and its capabilities for global remote sensing of lightning in the radio regime are described. Some results from 7 years of successful operation are presented. A future global lightning monitoring mission, VGLASS, is described.
New inversion estimates of anthropogenic carbon fluxes for 29 discrete ocean regions are used to ... more New inversion estimates of anthropogenic carbon fluxes for 29 discrete ocean regions are used to study pathways of upper ocean ventilation. Sensitivity of the flux estimates to transport uncertainty is investigated using five different OGCM integrations. Global total uptake of anthropogenic carbon for 2000 is estimated to be 2.2 PgC/yr +/- 0.4 (two S.D.). The inverse analysis shows which geographic areas of the world ocean are the most important sinks for anthropogenic carbon, and how robust these regional flux estimates are in the face of model biases.
For the first time a climatological comparison of cloud-to-ground lightning (CG) data from the Na... more For the first time a climatological comparison of cloud-to-ground lightning (CG) data from the National Lightning Detection Network (NLDN) and Cloud Top Temperature (CTT) from the 10.7 μ m channel of the GOES-8 satellite is addressed. Data involved in the study concern 12 months shared between 1998 and 1999. Millions of events available each month of the study and for each lightning categories (+CG and -CG) make the robustness of the statistics. These data show two kinds of behaviors. One set of clouds gathers thunderclouds with CTT warmer than -55 dg C, the second set, thunderclouds with CTT colder than -55 dg C. The first set of clouds represents the majority of thunderclouds. In these storms, the stroke densities are quasi-constant. This constant stroke densities display well defined dependences to the latitude and to the month of thunderstorm occurrences. Only, the threshold of CG production is CTT dependent for the storms belonging to the first set. Thunderclouds belonging to the second set, display stroke densities sharply increasing with decreasing CTT. The CTT dependence of stroke density is consistent with scaling law for lightning flash rates in function of the convective vigor of storms. Among the storms of the second set of data, are included those producing severe weather. A special analysis of those ``severe weather'' storm stroke densities and CTT correspondences will be presented. The presented work contributes to the current topic of scaling law for lightning flash rates. It brings also essential relationships for modelers who needs to parameterized CG rates in models implicitly resolving clouds.
We show that sustained plasma discharges in the ZT-40M reversed-field pinch experiment can be exp... more We show that sustained plasma discharges in the ZT-40M reversed-field pinch experiment can be explained in terms of electron wander in a stochastic magnetic field. We indicate results of a Fokker-Planck calculation for nonlocal electrical conductivity in slab geometry and show that this approach can account for the key anomalies of reversed-field pinch behavior, without needing to invoke a "plasma dynamo."
The Fast On-Orbit Recording of Transient Events (FORTE) satellite is a joint Los Alamos National ... more The Fast On-Orbit Recording of Transient Events (FORTE) satellite is a joint Los Alamos National Laboratory (LANL) and Sandia National Laboratories (SNL) experiment that was launched into a nearly circular low-earth orbit on August 29, 1997. The payload consists of broadband Very High Frequency (VHF) receivers and a two-sensor Optical Lightning System (OLS). One of the OLS sensors, the Lightning Location System (LLS), is a narrow band (777.6 nm + 0.5 nm) 128 x 128 pixel charge coupled device (CCD) array that is autonomously triggered, and provides imaging and geolocation of lightning events to within a pixel size of 10 km x 10 km. This paper presents a data-clustering algorithm which uses FORTE LLS event locations to both (a.) discriminate between lightning and energetic-particle/glint events and (b.) identify regions of high event density that are associated with storm activity. In addition to the utilization of basic statistical and data-clustering techniques, data driven thresholds are employed in the identification of probable storm regions. The application of automatic data discovery and analysis techniques allows for an efficient, flash/storm-level analysis of the more than 30 million events recorded by FORTE LLS, including a statistical characterization of seasonal, diurnal, and geographical variations in lightning and storm activity.
A laser diagnostic scheme is described which facilitates localization of density fluctuations alo... more A laser diagnostic scheme is described which facilitates localization of density fluctuations along the line of sight. The method exploits both the generally observed anisotropy of density fluctuations in low-beta plasmas, as well as the twisting of the magnetic field which occurs across the minor diameter of reversed-field pinches and spheromaks. Both interferometric and Schlieren variations are discussed.
An interferometer described in the Boston, 1992, meeting of the Beacon Satellite Symposium has be... more An interferometer described in the Boston, 1992, meeting of the Beacon Satellite Symposium has been in full operation for over a year now. It consists of four autonomous stations; three are in a triangle 70 km on a side and one is in the center. The stations receive the VHF beacons from two geosynchronous satellites, GOES-2 and ATS-3. The phases of the beacons are tracked at each station by referring them to an extremely stable rubidium oscillator. The studies of the two satellites are virtually separate experiments. The received phase of the beacon is retarded by the increased Total-Electron-Content of the dense regions of waves in the ionosphere. By comparing the phase history at four spatially separated stations, the authors can determine the two-dimensional propagation vector of the waves. This array is optimal for wavelengths of 70-300 km (periods of 300-3,000 seconds). Since the measurement is of the phase of the signal rather than the difference between the O-mode and X-mode phases, and since the beacons are in the VHF rather than in the L-band of GPS beacons, the array is very sensitive. It has a noise level of 10(exp 13) electrons/m(exp 2), or 10(sup -4) of the normal daytime TEC. This has been verified by operating two stations in the same location, so that they saw the same ionosphere. The first interesting results from a year's study is that the authors do not see the same TID's when looking at the two satellites. One conclusion they draw is that they do not see evidence of ionospheric winds.
A device which can overcome certain of the compromises of conventional Faraday rotation methods a... more A device which can overcome certain of the compromises of conventional Faraday rotation methods and at the same time measure the optical phase as well as the polarization is reported. This would be useful for unfolding the Faraday rotation signal using the line-of-sight density along exactly the same path. Preliminary design parameters using a CO2 laser are presented.
We present a statistical analysis of thunderstorm radiofrequency and optical data from the FORTE ... more We present a statistical analysis of thunderstorm radiofrequency and optical data from the FORTE satellite to examine the relationship of strong radiofrequency pulsed emissions to more conventional signals from lightning. The study is built on a FORTE database of intracloud, pulsed radio signals from storms whose geolocation is provided either by coincidence with the FORTE optical imager or by coincidence with ground-based lightning-detection arrays. Intracloud radio emissions with peak power >40 kW in the FORTE low band (26-48 MHz) have unique characteristics compared to weaker emissions, including: Occurring either in isolation or at the start of leader progression, but never within a progressing leader; occurring without light emission detectable with FORTE; occurring in frequent association with a rapid (10 microsec) relaxation of the electric charge; and followed by an upward-progressing leader, in the cases where a leader is initiated. These strong intracloud radio pulses appear to be associated with an intracloud discharge process that is physically distinct from conventional leader progression.
The Los Alamos Sferic Array (EDOT) has recorded over 3.7 million lightning-related fast electric ... more The Los Alamos Sferic Array (EDOT) has recorded over 3.7 million lightning-related fast electric field change data records during April 1 - August 31, 2001 and 2002. The events were detected by three or more stations, allowing for differential-time-of-arrival location determination. The waveforms are characterized with estimated peak currents as well as by event type. Narrow Bipolar Events (NBEs), the VLF/LF signature of Compact Intra-cloud Discharges (CIDs), are generally isolated pulses with identifiable ionospheric reflections, permitting determination of event source altitudes. We briefly review the EDOT characterization of events. The FORTE satellite observes Trans-Ionospheric Pulse Pairs (TIPPs, the VHF satellite signature of CIDs). The subset of coincident EDOT and FORTE CID observations are compared with the total EDOT CID database to characterize the VHF detection efficiency of CIDs. The NBE polarity and altitude are also examined in the context of FORTE TIPP detection. The parameter-dependent detection efficiencies are extrapolated from FORTE orbit to GPS orbit in support of the V-GLASS effort (GPS based global detection of lightning).
Journal of Atmospheric and Terrestrial Physics, Apr 30, 1989
The paper presents an introduction to the use of phase-coherent, multireceiver HF Doppler soundin... more The paper presents an introduction to the use of phase-coherent, multireceiver HF Doppler sounding arrays for measuring the horizontal velocity of traveling ionospheric disturbances (TIDs). The point of departure is the theorem of Pfister (1971) relating ray Doppler to ray zenith angle for a monostatic full reflection sounder. Retaining the simple model of a specular, smooth ionospheric reflector which is deformed by a propagating undulation, the theorem is first generalyzed to bistatic sounding geometry and then the effects of amplitude are included in addition to phase. Next, these results are cast into an algorithm for treating multireceiver phase sounders containing many diverse baselines, in order to obtain an accurate and unambiguous solution in the plane of wave slowness (inverse of velocity). The point spread function of this solution is controlled gy process bandwidth and by array geometry.
The ocean is an important sink for atmospheric carbon dioxide, and the exchange of carbon dioxide... more The ocean is an important sink for atmospheric carbon dioxide, and the exchange of carbon dioxide between the atmosphere and ocean plays a critical role in determining the spatial distribution of atmospheric carbon dioxide. However, there is still a great deal of uncertainty in both magnitude and regional patterns of anthropogenic uptake associated with estimates of oceanic carbon fluxes. Using a recently developed technique, exchange of anthropogenic carbon dioxide across the air-sea interface have been estimated from observations of dissolved inorganic carbon and nutrient concentrations and an Ocean General Circulation Model (OGCM) using a Green's function inverse modeling technique. Previous sensitivity studies have shown that model circulation error is an important source of error in the ocean inversion. In order to address the role of ocean circulation biases, inverse estimates of anthropogenic carbon air-sea gas exchange are presented using basis functions from a suite of seven different OGCM's. The robustness of the ocean inversion will be quantified and the effects of differences between approaches to modeling ocean circulation on the ocean carbon cycle will be explored. These results will be discussed in the context of recent atmospheric inverse estimates.
... Storm Monitoring Using VHF Receivers D. Suszcynsky, A. Jacobson, J. Fitzgerald, C. Rhodes, E.... more ... Storm Monitoring Using VHF Receivers D. Suszcynsky, A. Jacobson, J. Fitzgerald, C. Rhodes, E. Tech, D. Roussel-Dupre Los Alamos National Laboratory Space & Atmospheric Sciences Group,NIS-1 [email protected] 505-665-3119 FORTE Science/Operations Team ...
The oceanic carbon transport and propagation of uncertainties in an ocean inverse scheme are exam... more The oceanic carbon transport and propagation of uncertainties in an ocean inverse scheme are examined in detail. Traditionally, ocean carbon fluxes are estimated using bulk parameterization of air-sea gas exchange and observed air-sea gradients. An alternative approach has been published using ocean interior observations from the WOCE/JGOFS global carbon dioxide survey and an ocean general circulation model in a Green's function based inverse model to constrain the temporally averaged pre-industrial and present-day carbon dioxide fluxes. Thorough understandings of ocean carbon transport and error propagation through the inverse system are critical initial steps in this work. The ocean carbon transport in the model is examined in detail and with a focus on the impact of uncertainty propagation on carbon transport. The potential biases to carbon transport in the inverse scheme due to the technique used to account for biological processes and the impact of propagation of uncertainty in the observations are discussed.
Observations by HF ionospheric sounding of disturbances produced by powerful chemical explosions ... more Observations by HF ionospheric sounding of disturbances produced by powerful chemical explosions (several KT) are described. These experiments were performed at distances of about 30 to 40 km from the explosion point. Because of the amplification due to the atmospheric density decrease with increasing altitude, the acoustic waves from such explosions are characterized by shock waves features when they reach the ionosphere. The development of the disturbance was studied from the lower E region up to the F2 region by using 8 sounding frequencies. It is shown that a blanketing sporadic E layer undergoes small scale fluctuations and becomes semi-transparent after the passage of the disturbance. Several wave fronts with different properties are followed to the F1 region. In the lower E region, the wave induced stratifications on which the radio waves are partially reflected. The echoes totally reflected in the E region undergo an amplitude modulation with a period of about 2 seconds, persisting about 30 minutes. The variations of the total reflection height and of the Doppler frequency shift are most noticeable in the F1 region. The wave loses its shock wave feature in the F2 region and the disturbance signature is then that of a pseudo-sinusoidal wave with a wave length of several tens of kilometers.
A 6-min-period oscillation persisting for an hour has been observed in the ionospheric E region f... more A 6-min-period oscillation persisting for an hour has been observed in the ionospheric E region following a 5-kt chemical explosion on the ground 250 km south of the measurement site. The oscillations' phase velocity in the upper atmosphere is 0.15 km/s at an azimuth 60 W.
Journal of Geophysical Research Atmospheres, Nov 27, 2001
We present long optical and radio frequency (RF) time series of lightning events observed with th... more We present long optical and radio frequency (RF) time series of lightning events observed with the FORTE satellite in January 2000. Each record contains multiple RF and optical impulses. We use the RF signatures to identify the general type of discharge for each impulse according to the discrimination techniques described by Suszcynsky et al. (2000) and reviewed herein. We see a large number of paired, impulsive events in the RF which allow us to study the heights within clouds of several events. We also see that the rate of RF/optical coincidence depends on the type of discharge: nearly 100% of VHF signals from first negative return strokes have an associated optical signal, whereas a mere 50% of impulsive intracloud events appear to have an optical counterpart. While the RF signals from ground strokes clearly coincide with simple optical signals in almost all cases, the intracloud lightning often shows nearly continuous, complicated RF and optical emissions which do not cleanly correlate with one another. The RF and optical pulses do not show a well-defined relationship of intensities, for any lightning type. The observed delay between the RF and optical pulses we interpret as mainly an effect of the scattering experienced by the light as it traverses the cloud. For intracloud lightning, we find no evidence of an intrinsic delay at the source between the onset of the RF and optical signals. Impulsive in-cloud RF events are seen to occur on average every 0.9 ms during a flash.
The Los Alamos National Laboratory/Sandia National Laboratory FORTE satellite is described and it... more The Los Alamos National Laboratory/Sandia National Laboratory FORTE satellite is described and its capabilities for global remote sensing of lightning in the radio regime are described. Some results from 7 years of successful operation are presented. A future global lightning monitoring mission, VGLASS, is described.
New inversion estimates of anthropogenic carbon fluxes for 29 discrete ocean regions are used to ... more New inversion estimates of anthropogenic carbon fluxes for 29 discrete ocean regions are used to study pathways of upper ocean ventilation. Sensitivity of the flux estimates to transport uncertainty is investigated using five different OGCM integrations. Global total uptake of anthropogenic carbon for 2000 is estimated to be 2.2 PgC/yr +/- 0.4 (two S.D.). The inverse analysis shows which geographic areas of the world ocean are the most important sinks for anthropogenic carbon, and how robust these regional flux estimates are in the face of model biases.
For the first time a climatological comparison of cloud-to-ground lightning (CG) data from the Na... more For the first time a climatological comparison of cloud-to-ground lightning (CG) data from the National Lightning Detection Network (NLDN) and Cloud Top Temperature (CTT) from the 10.7 μ m channel of the GOES-8 satellite is addressed. Data involved in the study concern 12 months shared between 1998 and 1999. Millions of events available each month of the study and for each lightning categories (+CG and -CG) make the robustness of the statistics. These data show two kinds of behaviors. One set of clouds gathers thunderclouds with CTT warmer than -55 dg C, the second set, thunderclouds with CTT colder than -55 dg C. The first set of clouds represents the majority of thunderclouds. In these storms, the stroke densities are quasi-constant. This constant stroke densities display well defined dependences to the latitude and to the month of thunderstorm occurrences. Only, the threshold of CG production is CTT dependent for the storms belonging to the first set. Thunderclouds belonging to the second set, display stroke densities sharply increasing with decreasing CTT. The CTT dependence of stroke density is consistent with scaling law for lightning flash rates in function of the convective vigor of storms. Among the storms of the second set of data, are included those producing severe weather. A special analysis of those ``severe weather'' storm stroke densities and CTT correspondences will be presented. The presented work contributes to the current topic of scaling law for lightning flash rates. It brings also essential relationships for modelers who needs to parameterized CG rates in models implicitly resolving clouds.
We show that sustained plasma discharges in the ZT-40M reversed-field pinch experiment can be exp... more We show that sustained plasma discharges in the ZT-40M reversed-field pinch experiment can be explained in terms of electron wander in a stochastic magnetic field. We indicate results of a Fokker-Planck calculation for nonlocal electrical conductivity in slab geometry and show that this approach can account for the key anomalies of reversed-field pinch behavior, without needing to invoke a "plasma dynamo."
The Fast On-Orbit Recording of Transient Events (FORTE) satellite is a joint Los Alamos National ... more The Fast On-Orbit Recording of Transient Events (FORTE) satellite is a joint Los Alamos National Laboratory (LANL) and Sandia National Laboratories (SNL) experiment that was launched into a nearly circular low-earth orbit on August 29, 1997. The payload consists of broadband Very High Frequency (VHF) receivers and a two-sensor Optical Lightning System (OLS). One of the OLS sensors, the Lightning Location System (LLS), is a narrow band (777.6 nm + 0.5 nm) 128 x 128 pixel charge coupled device (CCD) array that is autonomously triggered, and provides imaging and geolocation of lightning events to within a pixel size of 10 km x 10 km. This paper presents a data-clustering algorithm which uses FORTE LLS event locations to both (a.) discriminate between lightning and energetic-particle/glint events and (b.) identify regions of high event density that are associated with storm activity. In addition to the utilization of basic statistical and data-clustering techniques, data driven thresholds are employed in the identification of probable storm regions. The application of automatic data discovery and analysis techniques allows for an efficient, flash/storm-level analysis of the more than 30 million events recorded by FORTE LLS, including a statistical characterization of seasonal, diurnal, and geographical variations in lightning and storm activity.
A laser diagnostic scheme is described which facilitates localization of density fluctuations alo... more A laser diagnostic scheme is described which facilitates localization of density fluctuations along the line of sight. The method exploits both the generally observed anisotropy of density fluctuations in low-beta plasmas, as well as the twisting of the magnetic field which occurs across the minor diameter of reversed-field pinches and spheromaks. Both interferometric and Schlieren variations are discussed.
An interferometer described in the Boston, 1992, meeting of the Beacon Satellite Symposium has be... more An interferometer described in the Boston, 1992, meeting of the Beacon Satellite Symposium has been in full operation for over a year now. It consists of four autonomous stations; three are in a triangle 70 km on a side and one is in the center. The stations receive the VHF beacons from two geosynchronous satellites, GOES-2 and ATS-3. The phases of the beacons are tracked at each station by referring them to an extremely stable rubidium oscillator. The studies of the two satellites are virtually separate experiments. The received phase of the beacon is retarded by the increased Total-Electron-Content of the dense regions of waves in the ionosphere. By comparing the phase history at four spatially separated stations, the authors can determine the two-dimensional propagation vector of the waves. This array is optimal for wavelengths of 70-300 km (periods of 300-3,000 seconds). Since the measurement is of the phase of the signal rather than the difference between the O-mode and X-mode phases, and since the beacons are in the VHF rather than in the L-band of GPS beacons, the array is very sensitive. It has a noise level of 10(exp 13) electrons/m(exp 2), or 10(sup -4) of the normal daytime TEC. This has been verified by operating two stations in the same location, so that they saw the same ionosphere. The first interesting results from a year's study is that the authors do not see the same TID's when looking at the two satellites. One conclusion they draw is that they do not see evidence of ionospheric winds.
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Papers by Abram Jacobson