Sample records for equatorial plasma bubbles

  1. Transequatorial propagation through equatorial plasma bubbles—Discrete events

    Microsoft Academic Search

    M. L. Heron

    1980-01-01

    The discrete nature of VHF transequatorial propagation path openings is pointed out. These events are shown to be consistent with the concept of guided propagation inside equatorial plasma bubbles. The important prediction of this work is that observations on discrete transequatorial VHF links may be used to track the production and development of equatorial plasma bubbles.

  2. The Morphology of Equatorial Plasma Bubbles - a review

    NASA Astrophysics Data System (ADS)

    Kil, Hyosub

    2015-03-01

    Plasma bubbles that occur in the equatorial F-region make up one of the most distinguishing phenomena in the ionosphere. Bubbles represent plasma depletions with respect to the background ionosphere, and are the major source of electron density irregularities in the equatorial F-region. Such bubbles are seen as plasma depletion holes (in situ satellite observations), vertical plumes (radar observations), and emission-depletion bands elongated in the north-south direction (optical observations). However, no technique can observe the whole three-dimensional structure of a bubble. Various aspects of bubbles identified using different techniques indicate that a bubble has a "shell" structure. This paper reviews the development of the concepts of "bubble" and "shell" in this context.

  3. 3D Modeling of Equatorial Plasma Bubbles

    NASA Astrophysics Data System (ADS)

    Huba, Joseph; Joyce, Glenn; Krall, Jonathan

    2011-11-01

    Post-sunset ionospheric irregularities in the equatorial F region were first observed by Booker and Wells (1938) using ionosondes. This phenomenon has become known as equatorial spread F (ESF). During ESF the equatorial ionosphere becomes unstable because of a Rayleigh-Taylor-like instability: large scale (10s km) electron density ``bubbles'' can develop and rise to high altitudes (1000 km or greater at times). Understanding and modeling ESF is important because of its impact on space weather: it causes radio wave scintillation that degrades communication and navigation systems. In fact, it is the focus of of the Air Force Communications/Navigation Outage Forecast Satellite (C/NOFS) mission. We will describe 3D simulation results from the NRL ionosphere models SAMI3 and SAMI3/ESF of this phenomenon. In particular, we will examine the causes of the day-to-day ariability of ESF which is an unresolved problem at this time. Booker, H.G. and H.G. Wells, Terr. Mag. Atmos. Elec. 43, 249, 1938.

  4. Guest investigator program study: Physics of equatorial plasma bubbles

    NASA Technical Reports Server (NTRS)

    Tsunoda, Roland T.

    1994-01-01

    Plasma bubbles are large-scale (10 to 100 km) depletions in plasma density found in the night-time equatorial ionosphere. Their formation has been found to entail the upward transport of plasma over hundreds of kilometers in altitude, suggesting that bubbles play significant roles in the physics of many of the diverse and unique features found in the low-latitude ionosphere. In the simplest scenario, plasma bubbles appear first as perturbations in the bottomside F layer, which is linearly unstable to the gravitationally driven Rayleigh-Taylor instability. Once initiated, bubbles develop upward through the peak of the F layer into its topside (sometimes to altitudes in excess of 1000 km), a behavior predicted by the nonlinear form of the same instability. While good general agreement has been found between theory and observations, little is known about the detailed physics associated with plasma bubbles. Our research activity centered around two topics: the shape of plasma bubbles and associated electric fields, and the day-to-day variability in the occurrence of plasma bubbles. The first topic was pursued because of a divergence in view regarding the nonlinear physics associated with plasma bubble development. While the development of perturbations in isodensity contours in the bottomside F layer into plasma bubbles is well accepted, some believed bubbles to be cylinder-like closed regions of depleted plasma density that floated upward leaving a turbulent wake behind them (e.g., Woodman and LaHoz, 1976; Ott, 1978; Kelley and Ott, 1978). Our results, summarized in a paper submitted to the Journal of Geophysical Research, consisted of incoherent scatter radar measurements that showed unambiguously that the depleted region is wedgelike and not cylinderlike, and a case study and modeling of SM-D electric field instrument (EFI) measurements that showed that the absence of electric-field perturbations outside the plasma-depleted region is a distinct signature of wedge-shaped plasma bubbles. The second topic was pursued because the inability to predict the day-to-day occurrence of plasma bubbles indicated inadequate knowledge of the physics of plasma bubbles. An understanding of bubble formation requires an understanding of the roles of the various terms in the linearized growth rate of the collisional Rayleigh-Taylor instability. In our study, we examined electric-field perturbations found in SM-D EFI data and found that the seeding is more likely to be produced in the E region rather than the F region. The results of this investigation are presented in the Appendix of this report and will be submitted for publication in the Journal of Geophysical Research.

  5. GPS Observations of Plasma Bubbles and Scintillations over Equatorial Africa

    NASA Astrophysics Data System (ADS)

    Carrano, C. S.; Valladares, C. E.; Semala, G. K.; Bridgwood, C. T.; Adeniyi, J.; Amaeshi, L. L.; Damtie, B.; D'Ujanga Mutonyi, F.; Ndeda, J. D.; Baki, P.; Obrou, O. K.; Okere, B.; Tsidu, G. M.

    2010-12-01

    Sponsored in part by the International Heliophysical Year (IHY) program, Boston College, Air Force Research Laboratory (AFRL), and several universities in Africa have collaborated to deploy a network of GPS receivers throughout equatorial Africa, a region which has been largely devoid of ground-based ionospheric monitoring instruments. High date-rate GPS receivers capable of measuring Total Electron Content (TEC) and GPS scintillations were installed at Abidjan, Ivory Coast (5.3°N, 4.0°W, dip 3.5°S); Addis Ababa (9.0°N, 38.8°E, dip 0.1°N ); Bahir Dar, Ethiopia (26.1°N, 50.6°E, dip 20.1°N); Cape Verde (16.6°S, 22.9°W, dip 4.9°N); Ilorin, Nigeria (8.4°S, 4.7°E, dip 1.9°S); Kampala, Uganda (0.3°S, 32.6°E, dip 9.2°S); Lagos, Nigeria (6.5°N, 3.4°E, dip 3.1°S); Nairobi, Kenya (1.3°S, 36.8°W, dip 10.7°S); Nsukka, Nigeria (6.8°S, 7.4°W, dip 3.0°S); and Zanzibar, Tanzania (6.2°S, 39.2°E, dip 15.9°S). In this paper we report on the longitudinal, local time and seasonal occurrence of plasma bubbles and L band scintillations over equatorial Africa in 2009 and 2010, as a first step toward establishing the climatology of ionospheric irregularities over Africa. The scintillation intensity is obtained by measuring the standard deviation of normalized GPS signal power. The plasma bubbles are detected using an automated technique, whereby the GPS TEC is detrended to remove the diurnal variation and excursions exceeding a particular threshold are extracted for further analysis. A harmonic analysis (FFT) of these extracted events is performed to exclude wavelike features indicative of gravity waves or traveling ionospheric disturbances, and the remaining events are identified as plasma bubbles. Our findings suggest that the occurrence of plasma bubbles and L band scintillations over Africa are well correlated, but that some discrepancies in their morphologies are evident. While plasma bubbles and scintillations are generally observed during equinoctial periods, there are some longitudinal differences in their local time and seasonal occurrence statistics.

  6. Numerical simulation of equatorial plasma bubbles over Cachimbo: COPEX campaign

    NASA Astrophysics Data System (ADS)

    Carrasco, A. J.; Batista, I. S.; Abdu, M. A.

    2014-08-01

    The problem of day-to-day variability in onset of equatorial spread F (ESF) is addressed using data from the 2002 COPEX observational campaign in Brazil and numerical modeling. The observational results show that for values of virtual height of the F layer base less than 355 km at around 18:35 LT, and for the prereversal peak enhancement of the vertical plasma drift (Vp) less than 30 m/s, the spread-F (ESF) was absent on four nights over Cachimbo (9.5°S, 54.8°W, dip latitude = -2.1°). In this work we analyze the geophysical conditions for the generation of the irregularities by comparing the nights with and without the ESF. In the comparison a numerical code is used to simulate plasma irregularity development in an extended altitude range from the bottom of the equatorial F layer. The code uses the flux corrected transport method with Boris-Book’s flux limiter for the spatial integration and a predictor-corrector method for the direct time integration of the continuity equation for O+ and the SOR (Successive-Over-Relaxation) method for electric potential equation. The code is tested with different evening eastward electric fields (or vertical drifts Vp < 30 m/s and Vp > 30 m/s) in order to study the influence of the prereversal enhancement in the zonal electric field on plasma bubble formation and development. The code also takes into account the zonal wind, the vertical electric field and the collision frequency of ions with neutrals and the amplitude of initial perturbation. The simulation shows a good agreement with the observational results of the ESF. The results of the code suggest that the instability can grow at the F layer bottomside by the Rayleigh-Taylor mechanism only when the Vp > 30 m/s. In the analyzed cases we have considered the competition of other geophysical parameters in the generation of plasma structures.

  7. Nonlinear evolution of equatorial spread F. 3. Plasma bubbles generated by structured electric fields

    Microsoft Academic Search

    Chao-Song Huang; Michael C. Kelley

    1996-01-01

    Observations have shown that in some cases equatorial spread F (ESF) irregularities including plasma bubbles are related to temporal and spatial structures of electric fields. It has been conjectured that the electric field structures may be responsible to production of ESF bubbles. We present here numerical results of electric field effects in nonlinear evolution of ESF. In our simulations we

  8. The zonal motion of equatorial plasma bubbles relative to the background ionosphere

    NASA Astrophysics Data System (ADS)

    Kil, Hyosub; Lee, Woo Kyoung; Kwak, Young-Sil; Zhang, Yongliang; Paxton, Larry J.; Milla, Marco

    2014-07-01

    The zonal motions of plasmas inside equatorial plasma bubbles are different from those in the background ionosphere. The difference was explained in terms of the tilt of bubbles by recent studies, but observational evidence of this hypothesis has not yet been provided. We examine this hypothesis and, at the same time, look for an alternative explanation on the basis of the coincident satellite and radar observations over Jicamarca (11.95°S, 76.87°W) in Peru. In the observations at premidnight by the first Republic of China satellite (altitude: 600 km, inclination: 35°), plasmas inside bubbles drift westward relative to ambient plasmas. The same phenomenon is identified by radar observations. However, the relative westward plasma motions inside bubbles occur regardless of the tilt of bubbles, and therefore, the tilt is not the primary cause of the deviation of the plasma motions inside bubbles. The zonal plasma motions in the topside are characterized by systematic eastward drifts, whereas the zonal motions of plasmas in the bottomside backscatter layer show a mixture of eastward and westward drifts. The zonal plasma motions inside backscatter plumes resemble those in the bottomside backscatter layer. These observations indicate that plasmas inside bubbles maintain the properties of the zonal plasma motions in the bottomside where the bubbles originate. With this assumption, the deviation of the zonal motions of plasmas inside bubbles from those of ambient plasmas is understood in terms of the difference of the zonal plasma flows in the bottomside and topside.

  9. Automated Processing of Airglow Images for Studying Equatorial Plasma Bubbles

    NASA Astrophysics Data System (ADS)

    Makela, Jonathan J.; Yao, Daniel; Miller, Ethan

    As an increasing number of ionospheric imaging instruments are deployed to study structure in the Earth's ionosphere, it will become more important to develop efficient techniques to analyze the wealth of data that is collected. Several novel techniques have been created to extract useful parameters from airglow images captured from imagers installed at multiple locations around the globe. A system has been developed to detect bubble events in our airglow image database, spanning over seven years. This is a site labeler that divides each image into 16×16 pixel sites and classifies each site based upon the statistics within each site. The nonsubsampled wavelet transform at different levels is used as a texture descriptor and is combined with pixel statistics to form feature vectors for each site. Classification is performed with a simple back-propagationtrained neural network and site labels are smoothed by a random field approach. Labels are drawn from a 4-class set consisting of "clear", "bubble", "cloudy", and "other" categories. Once an image is labeled as containing a bubble, another algorithm is used to segment the image into regions containing the bubble. These regions can be analyzed to estimate structure scale sizes and drift velocities, among other physical parameters. We also show how the segmented bubble regions can be used in conjunction with radio occultation links to estimate the scattering irregularity height.

  10. Three-dimensional morphology of equatorial plasma bubbles deduced from measurements onboard CHAMP

    NASA Astrophysics Data System (ADS)

    Park, J.; Lühr, H.; Noja, M.

    2015-01-01

    Total electron content (TEC) between Low-Earth-Orbit (LEO) satellites and the Global Navigation Satellite System (GNSS) satellites can be used to constrain the three-dimensional morphology of equatorial plasma bubbles (EPBs). In this study we investigate TEC measured onboard the Challenging Minisatellite Payload (CHAMP) from 2001 to 2005. We only use TEC data obtained when CHAMP passed through EPBs: that is, when in situ plasma density measurements at CHAMP altitude also show EPB signatures. The observed TEC gradient along the CHAMP track is strongest when the corresponding GNSS satellite is located equatorward and westward of CHAMP with elevation angles of about 40-60°. These elevation and azimuth angles are in agreement with the angles expected from the morphology of the plasma depletion shell proposed by Kil et al.(2009).

  11. Equatorial plasma bubbles in the ionosphere over Eritrea: occurrence and drift speed

    NASA Astrophysics Data System (ADS)

    Wiens, R. H.; Ledvina, B. M.; Kintner, P. M.; Afewerki, M.; Mulugheta, Z.

    2006-07-01

    An all-sky imager was installed in Asmara, Eritrea (15.4° N, 38.9° E, 7° N dip) and used to monitor the OI 630-nm nightglow. Nine months of data were studied between September 2001 and May 2002, a time including the recent maximum in the solar activity cycle. Equatorial plasma bubbles (EPBs) were recorded on 63% of nights with adequate viewing conditions. The station location within view of the equatorial ionization anomaly and with a magnetic declination near zero makes it an excellent test case for comparison with satellite studies of the seasonal variation of EPBs with longitude. The imager was accompanied by two Cornell GPS scintillation monitors, and the amplitude scintillation data are compared to the all-sky data. GPS scintillations indicate the beginning of EPBs, but die out sooner in the post-midnight period than the larger scale EPBs. Both phenomena exhibit clear occurrence maxima around the equinoxes. Ionospheric zonal drift speeds have been deduced from EPB and GPS scintillation pattern movement. Average near-midnight EPB drift speeds are between 100 and 120 m/s most months, with the GPS scintillation speeds being about the same. A winter drift speed maximum is evident in both EPB and GPS scintillation monthly means.

  12. Faith in a seed: on the origins of equatorial plasma bubbles

    NASA Astrophysics Data System (ADS)

    Retterer, J. M.; Roddy, P.

    2014-05-01

    Our faith in the seeds of equatorial plasma irregularities holds that there will generally always be density perturbations sufficient to provide the seeds for irregularity development whenever the Rayleigh-Taylor instability is active. When the duration of the time of the Rayleigh-Taylor instability is short, however, the magnitude of the seed perturbations can make a difference in whether the irregularities have a chance to grow to a strength at which the nonlinear development of plumes occurs. In addition, the character of the resulting irregularities reflects the characteristics of the initial seed density perturbation, e.g., their strength, spacing, and, to some extent, their spatial scales, and it is important to know the seeds to help determine the structure of the developed irregularities. To this end, we describe the climatology of daytime and early-evening density irregularities that can serve as seeds for later development of plumes, as determined from the Planar Langmuir Probe (PLP) plasma density measurements on the C/NOFS (Communication and Navigation Outage Forecast System) satellite mission, presenting their magnitude as a function of altitude, latitude, longitude, local time, season, and phase in the solar cycle (within the C/NOFS observation era). To examine some of the consequences of these density perturbations, they are used as initial conditions for the PBMOD PBMOD (Retterer, 2010a) 3-D irregularity model to follow their potential development into larger-amplitude irregularities, plumes, and radio scintillation. "Though I do not believe that a pla[sma bubble] will spring up where no seed has been, I have great faith in a seed. Convince me that you have a seed there, and I am prepared to expect wonders." - Henry David Thoreau

  13. Remote detection of the maximum altitude of equatorial ionospheric plasma bubbles

    NASA Technical Reports Server (NTRS)

    Benson, R. F.

    1981-01-01

    Nearly 200 post-sunset low-altitude passes of the Alouette 2 and ISIS 1 satellites near the dip equator are studied in order to find the maximum ionospheric plasma bubble altitudes, which are determined by calculating the apex altitude of the magnetic field line passing through the satellite when it is immersed in a bubble. The calculations are made only upon the observation of conjugate hemisphere ionospheric echoes, which result from ducted HF sounder signals that are guided along field-aligned irregularities within the plasma depletion. The maximum bubble altitudes corresponding to the three longitude sectors centered on zero deg, 75 deg W, and 105 deg E, are found to often exceed 1000 km, but seldom 3000 km. The electron density depletions within these field-aligned bubbles, as measured at the point of satellite encounter with the topside ionosphere, are generally less than a factor of two but may exceed a factor of ten.

  14. Distributions of TEC Fluctuations and Losses of Lock Associated with Equatorial Plasma Bubbles

    NASA Astrophysics Data System (ADS)

    Nakata, H.; Kikuchi, H.; Tsugawa, T.; Otsuka, Y.; Takano, T.; Shimakura, S.; Shiokawa, K.; Ogawa, T.

    2009-12-01

    Equatorial plasma bubbles (EPBs) are local depletions of the electron density in the ionosphere. Due to field-aligned irregularities (FAIs) with various spatial scales, EPBs affect wide-band radio waves and cause scintillations in GPS navigation system. Strong scintillation can cause a GPS receiver to lose lock on GPS signals because of rapid variations of signal amplitude and phase, and limit the availability of carrier phase measurements. Since the scintillation is caused by Fresnel diffraction, the spatial scale of FAIs that causes the scintillation of GPS signals is about 2-300 m. Therefore, loss of phase lock (LOL) on GPS signals is a reference of hundred-meter-scale FAIs. As EPBs are also associated with fluctuations of the total electron content (TEC), the enhancement of Rate of TEC change index (ROTI) occurs around EPBs. Assuming that the altitude of the ionosphere is about 400 km, the velocity of the pierce point of the GPS radio wave at the ionospheric altitude is approximately 70 m/s around the zenith. Thus, ROTI averaged during 5 minutes is a reference of ten-kilometer-scale fluctuations. In this study, we analyzed LOL and 5-min. ROTI associated with EPBs to examine the spatial and temporal scales of electron density disturbances associated with EPBs. We selected 11 EPBs from 630-nm airglow images obtained by all-sky imager at Sata, Japan, in 2001. LOL and ROTI are obtained from GPS data from GPS Earth Observation Network (GEONET) of Japan, which consists of more than 1000 GPS receivers. As a result, it is shown that both LOL and the enhancement of ROTI are observed in 8 events out of 11 events. The distributions of LOL are approximately consistent with the areas in which the ionospheric electron density is depleted. The enhancements of ROTI are observed in the vicinities of EPBs. The enhancement of ROTI expands especially in the west side of EPBs. After the EPBs pass through, therefore, LOLs are vanished but the enhancements of ROTI last a while. This result shows that the hundred-meter-scale irregularities are distributed within EPBs while the ten-kilometer-scale disturbances are located around EPBs. Such huge EPBs as to be observed in Japan will appear in solar maximum periods. Therefore it is important to prepare against the next solar maximum by examining characteristics of the EPBs. Fortunately, LOL and the enhancement of ROTI are treated as indicators of these huge EPBs since most of the EPBs are associated with them. Examinations of these EPBs must be progressed further.

  15. Topside sounder observations of equatorial bubbles

    NASA Technical Reports Server (NTRS)

    Dyson, P. L.; Benson, R. F.

    1978-01-01

    Large scale regions of depleted equatorial ionospheric plasma, called equatorial bubbles, are investigated using topside sounder data. The sounder's unique remote measuring capability enables the magnetic field-aligned nature of the bubbles to be investigated. A search of all available Alouette 2 and ISIS 1 ionograms during nighttime perigee passes near the magnetic equator has revealed a variety of echo signatures associated with bubbles. In addition to a sudden drop in electron density, these signatures usually include in situ spread F and ducted traces. The ducted traces have been used to determine the electron density distribution and to infer changes in ion composition along the magnetic field line within the duct associated with the bubble. In some cases it can be determined that the bubble is asymmetric with respect to the magnetic equator. Even though such features require 3 dimensional models for their explanation, the great field-aligned extent of the bubbles (relative to their cross section) suggests that current theories, which ignore variations along the magnetic field, are still applicable.

  16. Equatorial plasma bubble zonal velocity using 630.0 nm airglow observations and plasma drift modeling over Ascension Island

    NASA Astrophysics Data System (ADS)

    Chapagain, Narayan P.; Taylor, Michael J.; Makela, Jonathan J.; Duly, Timothy M.

    2012-06-01

    We present OI (630.0 nm) airglow image data from Ascension Island (geographic: 7.9°S, 14.4°W dip latitude: 16°S) in the southern Atlantic Ocean taken with the Utah State University all-sky CCD camera during 20 March to 7 April 1997 in order to study plasma bubbles occurring in the low-latitude nighttime ionosphere. The initial plasma bubble onset occurs in the early evening hours at ˜19:15-20:00 LST and is followed by eastward propagation with an average speed of ˜90-120 m/s prior to local midnight, rapidly decreasing around the midnight and postmidnight periods. The Ascension results are compared with similar observations from Christmas Island in order to examine the longitudinal variations of EPB development and propagation. The observed EPB velocities from Ascension Island are also compared with the results of a plasma drift model. In a case study during the night of 4-5 April, the velocity reveals unusual latitudinal shear, up to 0.12 m/s/km, with a reversal to westward flow at low latitudes while eastward flow is maintained at higher latitudes. Consequently, the bubble rotates counterclockwise and tilts eastward, significantly away from alignment with the geomagnetic field lines. The westward reversal of the drift motion near the geomagnetic equator is most likely the result of a reversal in the F region dynamo or from a large increase in the altitude of the shear node in the F region plasma drift at the geomagnetic equator.

  17. Simultaneous optical measurements of equatorial plasma bubble (EPB) from Kolhapur (16.8°N, 74.2°E) and Gadanki (13.5°N, 79.2°E)

    NASA Astrophysics Data System (ADS)

    Ghodpage, R. N.; Taori, A.; Patil, P. T.; Gurubaran, S.; Sripathi, S.; Banola, S.; Sharma, A. K.

    2014-12-01

    In this paper, we study the Equatorial Plasma Bubble (EPB) features using All sky imager (ASI) observations of O(1D) 630.0 nm night airglow emission from Kolhapur (16.8°N, 74.2°E, 10.6°N dip lat.) and Gadanki (13.5°N, 79.2°E, 6.5°N dip lat.) during March 2012. The optical data was supported by the ionosonde measurements from Tirunelveli (8.7°N, 77.8°E, 0.5°N dip lat.) which revealed the occurrence of equatorial spread-F. The EPBs were monitored at both locations as nearly north-south aligned intensity depleted regions. We computed east-west plasma drift velocity over Kolhapur and Gadanki for the nights having coordinated measurements. Also, the observed plasma bubble drift velocities are compared with the zonal neutral wind velocities obtained from the HWM-07 model and the empirical drift model of England and Immel (2012). We observed that, generally, the mean zonal drift velocities of the plasma bubbles tend to decrease with local time (after midnight). Our results reveal the drift velocity noted in Kolhapur data varies from 124 m/s to 181.8 m/s, while from the Gadanki data show the drift velocity to range from 116.3 m/s to 160.3 m/s.

  18. Colored bubbles: An experiment for triggering equatorial spread F

    Microsoft Academic Search

    G. Haerendel; O. H. Bauer; S. Cakir; H. Foeppl; E. Rieger; A. Valenzuela

    1983-01-01

    Barium plasma clouds were released in the post-sunset F region of the equatorial ionosphere. The clouds were characteristically distorted and exhibited the formation of irregularities of various scales. Visible striations, radio wave scintillations, spread echoes on ionograms were noted. Bubble formation was not observed. The origin of distortions and irregularities is related to the combined action of the friction with

  19. Modeling the Climatology of Equatorial Plasma Bubbles at Solar Minimum Using Plasma Drifts Observed by C/NOFS

    NASA Astrophysics Data System (ADS)

    Retterer, J. M.; Su, Y.; Gentile, L. C.; de La Beaujardiere, O.; Stoneback, R. A.; Pfaff, R. F.

    2010-12-01

    The goal of the C/NOFS (Communication and Navigation Outage Forecast System) project is to further our understanding of the processes in the low-latitude ionosphere that lead to radio scintillation that can interfere with operational systems. Because the height of the F-layer of the ionospheric plasma at night largely controls whether scintillation occurs, the vertical plasma drift is a key parameter among the several quantities the C/NOFS satellite was instrumented to measure in predicting whether scintillation occurs or not. Based on the operation of the C/NOFS IVM Ion Driftmeter and VEFI Electric Field Instrument over the two years since its launch, a climatological model of the vertical plasma drift has been obtained using long-term averages of the measurements. These drifts have been used in PBMOD, the first-principles model of the low-latitude ionosphere, bubble formation, and scintillation developed for the C/NOFS program, to see whether these drifts are in accord with observations of these phenomena. The DMSP satellites, in circular near-polar orbits around 840 km altitude, occasionally observe depletions in plasma density when they cross the geomagnetic equator in the evening and dawn sectors. Statistics for the frequency of observation of these depletions have been collected over the period of the C/NOFS mission. Recall that this period was a remarkably low and extended solar minimum, and the pattern of scintillation occurrence then is notably different from the standard paradigm of post-sunset occurrence. We will present maps of the frequency of occurrence of depletions, calculated with the models using the C/NOFS drift climatology, as a function of season and longitude, and compare the results with DMSP and other observations.

  20. MF and HF ducting within equatorial bubbles

    NASA Astrophysics Data System (ADS)

    Platt, I. G.; Dyson, P. L.

    1989-10-01

    MF and HF conjugate ducting is often observed while satellite sounders are within equatorial bubbles. This paper examines two possible forms of this propagation. The first is guiding by the bubble itself, the second is ducting along irregularities of small cross-section embedded in the bubble. One bubble model, based on observations by Dyson and Benson (1978) gives some results at variance with observation. Nevertheless, it is considered that slight changes to the model, such as asymmetries between the conjugate ionospheres, should remove the discrepancies. The results show that both forms of propagation probably occur.

  1. A simulation of equatorial plasma bubble signatures on the OI 6300 A nightglow meridional profile over Brazilian low latitude

    NASA Astrophysics Data System (ADS)

    Nakamura, Y.; Sobral, J. H. A.; Abdu, M. A.

    1981-11-01

    The OI 6300 A nightglow emission measurements carried out by scanning photometers over Cachoeira Paulista show propagating disturbances of the meridional and east-west intensity profiles. The disturbances propagate from north to south and from west to east. It is shown that these disturbances are closely correlated with the occurrence of spread F irregularities observed by ionosonde. Airglow intensity was calculated as a function of zenith angle in the photometer scanning range using electron density profiles perturbed by field aligned plasma bubble, whose vertical velocity and electron density depletion profile were determined from a numerical simulation of the nonlinear Rayleigh Taylor instability under ionospheric conditions that best represented those of the observing period and location. The result shows that, as the field aligned plasma bubbles rises up over the equator, their extremities trace out poleward motion in the low latitude ionosphere which could explain the observed north to south propagation of the airglow intensity valleys.

  2. Continuous generation and two-dimensional structure of equatorial plasma bubbles observed by high-density GPS receivers in Southeast Asia

    NASA Astrophysics Data System (ADS)

    Buhari, S. M.; Abdullah, M.; Hasbi, A. M.; Otsuka, Y.; Yokoyama, T.; Nishioka, M.; Tsugawa, T.

    2014-12-01

    High-density GPS receivers located in Southeast Asia (SEA) were utilized to study the two-dimensional structure of ionospheric plasma irregularities in the equatorial region. The longitudinal and latitudinal variations of tens of kilometer-scale irregularities associated with equatorial plasma bubbles (EPBs) were investigated using two-dimensional maps of the rate of total electron content change index (ROTI) from 127 GPS receivers with an average spacing of about 50-100 km. The longitudinal variations of the two-dimensional maps of GPS ROTI measurement on 5 April 2011 revealed that 16 striations of EPBs were generated continuously around the passage of the solar terminator. The separation distance between the subsequent onset locations varied from 100 to 550 km with 10 min intervals. The lifetimes of the EPBs observed by GPS ROTI measurement were between 50 min and over 7 h. The EPBs propagated 440-3000 km toward the east with velocities of 83-162 m s-1. The longitudinal variations of EPBs by GPS ROTI keogram coincided with the depletions of 630 nm emission observed using the airglow imager. Six EPBs were observed by GPS ROTI along the meridian of Equatorial Atmosphere Radar (EAR), while only three EPBs were detected by the EAR. The high-density GPS receivers in SEA have an advantage of providing time continuous descriptions of latitudinal/longitudinal variations of EPBs with both high spatial resolution and broad geographical coverage. The spatial periodicity of the EPBs could be associated with a wavelength of the quasiperiodic structures on the bottomside of the F region which initiate the Rayleigh-Taylor instability.

  3. Explicit characteristics of evolutionary-type plasma bubbles observed from Equatorial Atmosphere Radar during the low to moderate solar activity years 2010-2012

    NASA Astrophysics Data System (ADS)

    Ajith, K. K.; Ram, S. Tulasi; Yamamoto, M.; Yokoyama, T.; Gowtam, V. Sai; Otsuka, Y.; Tsugawa, T.; Niranjan, K.

    2015-02-01

    Using the fan sector backscatter maps of 47 MHz Equatorial Atmosphere Radar (EAR) at Kototabang (0.2°S geographic latitude, 100.3°E geographic longitude, and 10.4°S geomagnetic latitude), Indonesia, the spatial and temporal evolution of equatorial plasma bubbles (EPBs) were examined to classify the evolutionary-type EPBs from those which formed elsewhere and drifted into the field of view of radar. A total of 535 EPBs were observed during the low to moderate solar activity years 2010-2012, out of which about 210 (~39%) are of evolving type and the remaining 325 (~61%) are drifting-in EPBs. In general, both the evolving-type and drifting-in EPBs exhibit predominance during the postsunset hours of equinoxes and December solstices. Interestingly, a large number of EPBs were found to develop even a few minutes prior to the apex sunset during equinoxes. Further, the occurrence of evolving-type EPBs exhibits a clear secondary peak around midnight (2300-0100 LT), primarily, due to higher rate of occurrence during the postmidnight hours of June solstices. A significant number (~33%) of postmidnight EPBs generated during June solstices did not exhibited any clear zonal drift, while about 14% of EPBs drifted westward. Also, the westward drifting EPBs are confined only to June solstices. The responsible mechanisms for the genesis of fresh EPBs during postmidnight hours were discussed in light of equatorward meridional winds in the presence of weak westward electric fields.

  4. Observations of the Topside Ionosphere Plasma Bubbles in the Separate Plasma Component (He+): Model Estimations

    NASA Astrophysics Data System (ADS)

    Sidorova, Larisa; Filippov, Sergey

    2013-04-01

    The question about an opportunity to detect the topside plasma bubbles of equatorial origin in their separate plasma component (He+) is investigated. There are the indications [1, 2, 3, 4] that there is genetic connection between the He+ density depletions (subtroughs) and the equatorial plasma bubbles. For validation of this idea the characteristic times of the main aeronomy and electrodynamics processes, in which the plasma bubbles and their minor ion component (He+) are involved, have been calculated and compared among themselves. The conditions and factors, connected with solar activity, which are more favorable in the detection of the topside ionosphere plasma bubbles as He+ depletions, were under consideration. The numerical calculations, obtained in SAMIS3 model (3D model of equatorial spread F) and kindly presented by J. Huba (USA) [5], were used for this study. It was revealed that the plasma bubbles, reaching the "ceiling" heights, can exist within several days and that there is principal opportunity to observe them in the separate plasma component (He+). [1] L.N. Sidorova, Adv. Space Res. 33, 850 (2004). [2] L.N. Sidorova, Adv. Space Res. 39, 1284 (2007). [3] L.N. Sidorova, Geomag. and Aeronomy, Intern. 48, 56 (2008). [4] L.N. Sidorova, S.V. Filippov, J. Atm. Solar-Terr. Phys. 86, 83-91, doi: 10.1016/j.jastp.2012.06.013 (2012). [5] J.D. Huba, G. Joyce, J. Krall, Geophys. Res. Lett. 35, L10102, doi:10.1029/2008GL033509 (2008).

  5. Radar and Optical Measurements of Equatorial Plasma Depletions

    NASA Astrophysics Data System (ADS)

    Chapagain, N. P.; Taylor, M. J.; Fejer, B. G.

    2008-12-01

    The primary focus of the recently launched Air Force Communication/Navigation Outage Forecasting System (C/NOFS) satellite is to quantify and forecast ionospheric irregularities responsible for the development of equatorial spread F that can severely affect communication and navigation systems. In support of this mission goal, we present new measurements and analyses using previously obtained ground-based radar and optical measurements from two important equatorial sites. Using available data from the Jicamarca JULIA and incoherent scatter radar observations from 1996 to 2006, we have studied the initial development of equatorial spread F from Peru (11.95°S, 76.87°W) over a full 11 year solar cycle. Detailed analysis show that onset heights and peak heights of radar plumes increase with increase in solar activity, as previously suggested from case studies. In contrast, investigations of spread F onset times show a little variation with solar activity, while onset times of radar plumes decrease from solar minimum to moderate conditions and then remain nearly constant during solar maximum. In addition to this study, we have also made novel investigations of spread F optical signatures (termed depletions) from Christmas Island (2°N, 157.4°W) in central Pacific region using CCD image measurements of the thermospheric OI 630 nm airglow emission. The measurements were obtained using a USU all-sky imager from Sep.14 to Oct 2, 1995, under solar minimum conditions similar to current levels that C/NOFS is measuring. We have analyzed the zonal velocities of the plasma depletions and their horizontal scale sizes. Large variations in the day-to-day spatial characteristics and the zonal velocities were found. We have proposed new measurements from equatorial Brazil in coordination with C/NOFS to investigate bubble dynamics and associated atmospheric conditions.

  6. Oscillating plasma bubbles. II. Pulsed experiments

    SciTech Connect

    Stenzel, R. L.; Urrutia, J. M. [Department of Physics and Astronomy, University of California, Los Angeles, California 90095-1547 (United States)

    2012-08-15

    Time-dependent phenomena have been investigated in plasma bubbles which are created by inserting spherical grids into an ambient plasma and letting electrons and ions form a plasma of different parameters than the ambient one. There are no plasma sources inside the bubble. The grid bias controls the particle flux. There are sheaths on both sides of the grid, each of which passes particle flows in both directions. The inner sheath or plasma potential develops self consistently to establish charge neutrality and divergence free charge and mass flows. When the electron supply is restricted, the inner sheath exhibits oscillations near the ion plasma frequency. When all electrons are excluded, a virtual anode forms on the inside sheath, reflects all ions such that the bubble is empty. By pulsing the ambient plasma, the lifetime of the bubble plasma has been measured. In an afterglow, plasma electrons are trapped inside the bubble and the bubble decays as slow as the ambient plasma. Pulsing the grid voltage yields the time scale for filling and emptying the bubble. Probes have been shown to modify the plasma potential. Using pulsed probes, transient ringing on the time scale of ion transit times through the bubble has been observed. The start of sheath oscillations has been investigated. The instability mechanism has been qualitatively explained. The dependence of the oscillation frequency on electrons in the sheath has been clarified.

  7. Anatomy of plasma structures in an equatorial spread F event

    NASA Astrophysics Data System (ADS)

    Chen, K. Y.; Yeh, H. C.; Su, S. Y.; Liu, C. H.; Huang, Norden E.

    This paper investigates the small scale plasma structures observed by ROCSAT-1 in the equatorial F region through the newly developed Hilbert-Huang transform (HHT) method in the time (space) domain under the frozen-in approximation. The new method allows us to decompose the non-stationary, nonlinear data into a finite number of intrinsic scale modes. In this report the structures of vertical ion velocity and horizontal density gradient inside a plasma bubble are analyzed mode by mode anatomically without making the usual linearization assumption. We found that the intrinsic modes for velocity and density gradient of the selected event have identical wave form for structures with scales between 300 m and 50 m. This implies that the vertical velocity fluctuations induced from the electric field follows the exact Boltzmann relation in the limited regime of scale length between 300 m and 50 m. A spectral break at 50 m is clearly seen in the velocity HHT spectrum. The spectral form of velocity differs greatly from that of density gradient at scale lengths shorter than 50 m.

  8. Longitudinal structure of plasma bubbles over South American Continent observed by GNSS TEC mapping

    NASA Astrophysics Data System (ADS)

    Takahashi, Hisao; De Paula, Eurico; Shiokawa, Kazuo; Otsuka, Yuichi; Marcos Denardini, Clezio; Nogueira, Paulo; Wrasse, Cristiano M.; Paulino, Igo; Costa, Sonia; Ivo, Andre; Gomes, Vitor C.

    Total electron contents (TEC) from the equatorial to low-middle latitude ionosphere over South American Continent have been monitored by ground-based GNSS receiving network RBMC/IBGE, LISN, IGS and RAMSAC since December 2012. It was possible to monitor spatial and temporal variations of TEC over South America with a spatial resolution of 150 -500 km and by 10 minutes time interval. Plasma bubble formation, development and longitudinal drifting modes were successfully monitored. Equidistant several bubbles (longitudinal separation of 500-1000 km) with a large latitudinal extension (> 2000 km) were frequently observed during the November to February season in 2013. Diagnostics of the equatorial plasma bubbles using TEC mapping technique will be presented and discussed.

  9. Plasma wave excitation on meteor trails in the equatorial electrojet

    Microsoft Academic Search

    Elaine Chapin; Erhan Kudeki

    1994-01-01

    The unusual properties of meteor echoes recently observed at Jicamarca (Chapin and Kudeki, 1994) are attributed to the growth and propagation of plasma irregularities along meteor trails deposited within the equatorial electrojet. It is suggested that trails at electrojet heights must carry intense discharge currents that excite two-stream and\\/or gradient drift instabilities for irregularity growth. The direction of electron motion

  10. Estimation of the initial amplitude of perturbation and its use in numerical simulation of plasma bubbles

    NASA Astrophysics Data System (ADS)

    Batista, Inez S.; Carrasco, Alexander J.; Abdu, Mangalathayil A.

    2012-07-01

    This work describes an experimental method for the calculation of the initial amplitude of plasma bubble seed perturbation in the bottomside F layer from ionograms. The observations show that after sunset the ionograms exhibit irregularities in the base of the F trace. In the context of the plasma depletion in the bottomside F-layer, the irregularities in ionograms can be seen like isodensity contour in evolution (in space and time). The initial amplitudes, calculated using the methodology, were used to simulate plasma bubbles through the use of flux corrected transport method with Boris-Book's flux limiter for the spatial integration and a predictor-corrector method for the direct time integration of the continuity equation of {O}^{+} and the SOR method for electric potential equation. Generalized Rayleigh-Taylor instability plays a predominant role in the evolution of long-wavelength irregularities in the equatorial ionosphere. This instability is influenced by the vertical density gradient at bottom of the F layer, and the magnitude and shape of the density perturbation that seeds the instability. The code is tested with different enhanced evening eastward electric fields to study the influences of pre-reversal enhancement in the zonal electric field on plasma bubble formation and development. The values of the zonal electric fields are based on Digisonde observations over the dip equatorial station of Cachimbo (9.5° S, 54.8° W) during the 2002 COPEX (Conjugate Point Equatorial Experiment) campaign in Brazil.

  11. Oscillating plasma bubbles. I. Basic properties and instabilities

    NASA Astrophysics Data System (ADS)

    Stenzel, R. L.; Urrutia, J. M.

    2012-08-01

    Plasma bubbles are created in an ambient discharge plasma. A bubble is a plasma volume of typically spherical shape, which is separated from the ambient plasma by a negatively biased grid of high transparency. Ions and electrons from the ambient plasma flow into the bubble volume. In steady state the flow of particles and currents is divergence-free, which is established by the plasma potential inside the bubble. The grid has two sheaths, one facing the ambient plasma, the other the bubble plasma. The inner sheath is observed to become unstable, causing the plasma potential in the bubble to oscillate. The instability arises from an excess of ions and a deficiency of electrons. Its frequency is in the range of the ion plasma frequency but depends on all parameters which influence the charge density in the sheath. When the grid voltage is very negative, electrons cannot enter the outer sheath, and the inner sheath becomes a virtual anode which reflects ions such that the bubble interior is empty. When an electron source is placed into the bubble it can neutralize the ions and the bubble refills. Without plasma sources or sinks the bubble plasma is extremely sensitive to perturbations by probes. Modified current-voltage characteristics of Langmuir and emissive probes are demonstrated. A sequence of papers first describes the basic steady-state properties, then the time evolution of bubbles, the effects of electron sources in bubbles, and the role of the grid and bubble geometry. The physics of plasma bubbles is important to several fields of basic plasma physics such as sheaths, sheath instabilities, diagnostic probes, electrostatic confinement, and current and space charge neutralization of beams.

  12. Broad plasma depletions detected in the bottomside of the equatorial F region: Simultaneous ROCSAT-1 and JULIA observations

    NASA Astrophysics Data System (ADS)

    Kil, Hyosub; Kwak, Young-Sil; Lee, Woo Kyoung; Oh, Seung-Jun; Milla, Marco; Galkin, Ivan

    2014-07-01

    We investigated the association of broad plasma depletions (BPDs) with plasma bubbles and ionospheric uplift in the equatorial F region using the coincident satellite and radar observations over Jicamarca in Peru. BPDs were detected by the first Republic of China satellite (ROCSAT-1) on the nights of 21 and 22 December 2002 during the period of moderate geomagnetic activity. The observations of the Jicamarca Unattended Long-term Investigations of the Ionosphere and Atmosphere radar and an ionosonde showed that the F peak height was lifted above the ROCSAT-1 altitude (600 km) at the times of the BPD detection. The fraction of NO+ was substantial at the locations of BPDs. These observations support the association of the BPDs with the ionospheric uplift. However, the absence of large backscatter plumes at the times of the BPD detection indicates that the BPDs were not produced by a single large bubble or a merger of bubbles.

  13. Mesospheric gravity waves and ionospheric plasma bubbles observed during the COPEX campaign

    NASA Astrophysics Data System (ADS)

    Paulino, I.; Takahashi, H.; Medeiros, A. F.; Wrasse, C. M.; Buriti, R. A.; Sobral, J. H. A.; Gobbi, D.

    2011-07-01

    During the Conjugate Point Experiment (COPEX) campaign performed at Boa Vista (2.80?N;60.70?W, dip angle21.7?N) from October to December 2002, 15 medium-scale gravity waves in the OHNIR airglow images were observed. Using a Keogram image analysis, we estimate their parameters. Most of the waves propagate to Northwest, indicating that their main sources are Southeast of Boa Vista. Quasi-simultaneous plasma bubble activities in the OI 630 nm images were observed in seven cases. The distances between the bubble depletions have a linear relationship with the wavelengths of the gravity waves observed in the mesosphere, which suggests a direct contribution of the mesospheric medium-scale gravity waves in seeding the equatorial plasma bubbles.

  14. The current system associated with the boundary of plasma bubbles

    NASA Astrophysics Data System (ADS)

    Sun, Wei-Jie; Fu, Suiyan; Pu, Zuyin; Parks, George K.; Slavin, James A.; Yao, Zhonghua; Zong, Qiu-Gang; Shi, Quanqi; Zhao, Duo; Cui, Yanbo

    2014-12-01

    The current system associated with the boundary of plasma bubbles in the Earth's magnetotail has been studied by employing Cluster multipoint observations. We have investigated the currents in both the dipolarization front (DF, leading edge of the plasma bubble) and the trailing edge of the plasma bubble. The distribution of currents at the edge indicates that there is a current circuit in the boundary of a plasma bubble. The field-aligned currents in the trailing edge of the plasma bubble are flowing toward the ionosphere (downward) on the dawnside and away from the ionosphere (upward) on the duskside, in the same sense as region-1 current. Together with previous studies of the current distributions in the DF and magnetic dip region, we have obtained a more complete picture of the current system surrounding the boundary of plasma bubble. This current system is very similar to the substorm current wedge predicted by MHD simulation models but with much smaller scale.

  15. Cluster and Double Star multipoint observations of a plasma bubble

    Microsoft Academic Search

    A. P. Walsh; A. N. Fazakerley; A. D. Lahiff; M. Volwerk; A. Grocott; M. W. Dunlop; A. T. Y. Lui; L. M. Kistler; M. Lester; C. Mouikis; Z. Pu; C. Shen; J. Shi; M. G. G. T. Taylor; E. Lucek; T. L. Zhang; I. Dandouras

    2009-01-01

    Depleted flux tubes, or plasma bubbles, are one possible explanation of bursty bulk flows, which are transient high speed flows thought to be responsible for a large proportion of flux transport in the magnetotail. Here we report observations of one such plasma bubble, made by the four Cluster spacecraft and Double Star TC-2 around 14:00 UT on 21 September 2005,

  16. Alfvén wave characteristics of equatorial plasma irregularities in the ionosphere derived from CHAMP observations

    NASA Astrophysics Data System (ADS)

    Lühr, Hermann; Park, Jaeheung; Xiong, Chao; Xiong, Chao; Rauberg, Jan

    2014-08-01

    We report magnetic field observations of the components transverse to the main field in the frequency range 1-25 Hz from times of equatorial plasma irregularity crossings. These field variations are interpreted as Alfvénic signatures accompanying intermediate-scale (150 m – 4 km) plasma density depletions. Data utilized are the high-resolution CHAMP magnetic field measurements sampled at 50 Hz along the north-south satellite track. The recorded signals do not reflect the temporal variation but the spatial distribution of Alfvénic signatures. This is the first comprehensive study of Alfvénic signatures related to equatorial plasma bubbles that covers the whole solar cycle from 2000 to 2010. A detailed picture of the wave characteristics can be drawn due to the large number (almost 9000) of events considered. Some important findings are: Alfvénic features are a common feature of intermediate-scale plasma structures. The zonal and meridional magnetic components are generally well correlated suggesting skewed current sheets. The sheets have an orientation that is on average deflect by about 32° away from magnetic east towards upward or downward depending on the hemisphere. We have estimated the Poynting flux flowing into the E region. Typical values are distributed over the range 10-8 - 10-6 W/m2. Large Poynting fluxes are related to steep spectra of the Alfvénic signal, which imply passages through regularly varying electron density structures. No dependence of the Poynting flux level on solar activity has been found. But below a certain solar flux value (F10.7 < 100 sfu) practically no events are detected. There is a clear tendency that large Poynting flux events occur preferably at early hours after sunset (e.g. 20:00 local time). Towards later times the occurrence peak shifts successively towards lower energy levels. Finally we compare our observations with the recently published results of the high-resolution 3-D model simulations by Dao et al. (2013).

  17. DEMETER Observations of Equatorial Plasma Depletions and Related Ionospheric Phenomena

    NASA Astrophysics Data System (ADS)

    Berthelier, J.; Malingre, M.; Pfaff, R.; Jasperse, J.; Parrot, M.

    2008-12-01

    DEMETER, the first micro-satellite of the CNES MYRIAD program, was launched from Baikonour on June 29, 2004 on a nearly circular, quasi helio-synchronous polar orbit at ~ 715 km altitude. The DEMETER mission focuses primarily on the search for a possible coupling between seismic activity and ionospheric disturbances as well as on the effects of natural phenomena such as tropospheric thunderstorms and man-made activities on the ionosphere. The scientific payload provides fairly complete measurements of the ionospheric plasma, energetic particles above ~ 70 keV, and plasma waves, up to 20 kHz for the magnetic and 3.3 MHz for the electric components. Several studies related to space weather and ionospheric physics have been conducted over the past years. Following a brief description of the payload and the satellite modes of operation, this presentation will focus on a set of results that provide a new insight into the physics of instabilities in the night-time equatorial ionosphere. The observations were performed during the major magnetic storm of November 2004. Deep plasma depletions were observed on several night-time passes at low latitudes characterized by the decrease of the plasma density by nearly 3 orders of magnitude relative to the undisturbed plasma, and a significant abundance of molecular ions. These features can be best interpreted as resulting from the rise of the F-layer above the satellite altitude over an extended region of the ionosphere. In one of the passes, DEMETER was operated in the Burst mode and the corresponding high resolution data allowed for the discovery of two unexpected phenomena. The first one is the existence of high intensity monochromatic wave packets at the LH frequency that develop during the decay phase of intense bursts of broadband LH turbulence. The broadband LH turbulence is triggered by whistlers emitted by lightning from atmospheric thunderstorms beneath the satellite. The second unexpected feature is the detection of a population of super-thermal ionospheric ions with a density of about 2-3% of the thermal ion population. The super- thermal ions appeared to be heated to temperatures of a few eV at times when LH turbulence and monochromatic wave packets are observed while the temperature of the core ion population is not affected. High time resolution plasma density measurements show the presence of strong small scale plasma irregularities in the depletions that scatter the high amplitude whistler waves and may lead to the development of strong LH turbulence and of monochromatic wave packets. The ensuing interaction between these waves and the ambient ions may lead to the formation of a super-thermal tail in the ion distribution function. Ion acceleration by LH turbulence and solitary waves is a commonly observed phenomenon along auroral magnetic field lines but, to our knowledge, this is the first time that a similar process has been observed in the equatorial ionosphere. These findings exemplify a novel coupling mechanism between the troposphere and the ionosphere: Under highly disturbed conditions at times of magnetic storms, part of the energy released by lightning and radiated as whistlers can dissipate in the equatorial ionosphere and produce super-thermal ion populations.

  18. Plasma core at the center of a sonoluminescing bubble

    NASA Astrophysics Data System (ADS)

    Bemani, F.; Sadighi-Bonabi, R.

    2013-01-01

    Considering high temperature and pressure during single bubble sonoluminescence collapse, a hot plasma core is generated at the center of the bubble. In this paper a statistical mechanics approach is used to calculate the core pressure and temperature. A hydrochemical model alongside a plasma core is used to study the bubble dynamics in two host liquids of water and sulfuric acid 85 wt % containing Ar atoms. Calculation shows that the extreme pressure and temperature in the plasma core are mainly due to the interaction of the ionized Ar atoms and electrons, which is one step forward to sonofusion. The thermal bremsstrahlung mechanism of radiation is used to analyze the emitted optical energy per flash of the bubble core.

  19. Plasma core at the center of a sonoluminescing bubble.

    PubMed

    Bemani, F; Sadighi-Bonabi, R

    2013-01-01

    Considering high temperature and pressure during single bubble sonoluminescence collapse, a hot plasma core is generated at the center of the bubble. In this paper a statistical mechanics approach is used to calculate the core pressure and temperature. A hydrochemical model alongside a plasma core is used to study the bubble dynamics in two host liquids of water and sulfuric acid 85 wt % containing Ar atoms. Calculation shows that the extreme pressure and temperature in the plasma core are mainly due to the interaction of the ionized Ar atoms and electrons, which is one step forward to sonofusion. The thermal bremsstrahlung mechanism of radiation is used to analyze the emitted optical energy per flash of the bubble core. PMID:23410423

  20. Oscillating plasma bubbles. III. Internal electron sources and sinks

    SciTech Connect

    Stenzel, R. L.; Urrutia, J. M. [Department of Physics and Astronomy, University of California, Los Angeles, California 90095-1547 (United States)

    2012-08-15

    An internal electron source has been used to neutralize ions injected from an ambient plasma into a spherical grid. The resultant plasma is termed a plasma 'bubble.' When the electron supply from the filament is reduced, the sheath inside the bubble becomes unstable. The plasma potential of the bubble oscillates near but below the ion plasma frequency. Different modes of oscillations have been observed as well as a subharmonic and multiple harmonics. The frequency increases with ion density and decreases with electron density. The peak amplitude occurs for an optimum current and the instability is quenched at large electron densities. The frequency also increases if Langmuir probes inside the bubble draw electrons. Allowing electrons from the ambient plasma to enter, the bubble changes the frequency dependence on grid voltage. It is concluded that the net space charge density in the sheath determines the oscillation frequency. It is suggested that the sheath instability is caused by ion inertia in an oscillating sheath electric field which is created by ion bunching.

  1. In-situ measurements of plasma parameters in the equatorial ionosphere by the resonance cone technique

    NASA Astrophysics Data System (ADS)

    Thiemann, H.; Piel, A.; Gupta, S. P.

    Resonance cone data obtained during a joint Indo-German rocket campaign in the equatorial ionosphere are presented. Plasma parameters are derived from the experimental data and compared with standard Langmuir probe measurements.

  2. Theoretical study of the ionospheric plasma cave in the equatorial ionization anomaly region

    NASA Astrophysics Data System (ADS)

    Chen, Yu-Tsung; Lin, C. H.; Chen, C. H.; Liu, J. Y.; Huba, J. D.; Chang, L. C.; Liu, H.-L.; Lin, J. T.; Rajesh, P. K.

    2014-12-01

    This paper investigates the physical mechanism of an unusual equatorial electron density structure, plasma cave, located underneath the equatorial ionization anomaly by using theoretical simulations. The simulation results provide important new understanding of the dynamics of the equatorial ionosphere. It has been suggested previously that unusual E>?×B>? drifts might be responsible for the observed plasma cave structure, but model simulations in this paper suggest that the more likely cause is latitudinal meridional neutral wind variations. The neutral winds are featured by two divergent wind regions at off-equator latitudes and a convergent wind region around the magnetic equator, resulting in plasma divergences and convergence, respectively, to form the plasma caves structure. The tidal-decomposition analysis further suggests that the cave related meridional neutral winds and the intensity of plasma cave are highly associated with the migrating terdiurnal tidal component of the neutral winds.

  3. Temperature structure of plasma bubbles in the low latitude ionosphere around 600 km altitude

    Microsoft Academic Search

    K.-I. Oyama; K. Schlegel; S. Watanabe

    1988-01-01

    The electron temperature inside plasma bubbles at a height of 600 km was first measured by means of Japan's seventh scientific satellite Hinotori which is an equator orbiting satellite with an inclination of 31 deg. During the period between June 1981 and February 1982, 724 plasma bubbles were detected and studied. The electron temperature inside the plasma bubbles is either

  4. Systematic study of intermediate-scale structures of equatorial plasma irregularities in the ionosphere based on CHAMP observations

    NASA Astrophysics Data System (ADS)

    Lühr, Hermann; Xiong, Chao; Park, Jaeheung; Rauberg, Jan

    2014-03-01

    Equatorial spread-F ionospheric plasma irregularities on the night-side, commonly called equatorial plasma bubbles (EPB), include electron density variations over a wide range of spatial scales. Here we focus on intermediate-scale structures ranging from 100 m to 10 km, which play an important role in the evolution of EPBs. High-resolution CHAMP magnetic field measurements sampled along north-south track at 50 Hz are interpreted in terms of diamagnetic effect for illustrating the details of electron density variations. We provide the first comprehensive study on intermediate-scale density structures associated with EPBs, covering a whole solar cycle from 2000 to 2010. The large number of detected events, almost 9000, allows us to draw a detailed picture of the plasma fine structure. The occurrence of intermediate-scale events is strongly favoured by high solar flux. During times of F10.7 < 100 sfu practically no events were observed. The longitudinal distribution of our events with respect to season or local time agrees well with that of the EPBs, qualifying the fine structure as a common feature, but the occurrence rates are smaller by a factor of 4 during the period 2000-2005. Largest amplitude electron density variations appear at the poleward boundaries of plasma bubbles. Above the dip-equator recorded amplitudes are small and fall commonly below our resolution. Events can generally be found at local times between 19 and 24 LT, with a peak lasting from 20 to 22 LT. The signal spectrum can be approximated by a power law. Over the frequency range 1 – 25 Hz we observe spectral indices between -1.4 and -2.6 with peak occurrence rates around -1.9. There is a weak dependence observed of the spectral index on local time. Towards later hours the spectrum becomes shallower. Similarly for the latitude dependence, there is a preference of shallower spectra for latitudes poleward of the ionisation anomaly crest. Our data suggest that the generation of small plasma structure

  5. New Evidence for Equatorially Trapped Thermal Plasma During Early Post-Storm Recovery

    NASA Technical Reports Server (NTRS)

    Gallagher, D. L.; Green, J. L.

    2005-01-01

    Almost 20 years ago Olsen et al. [1987] reported Dynamics Explorer 1 Retarding Ion Mass Spectrometer observations of equatorially trapped, cold ions in the vicinity of the plasmapause. In that study the trapped population corresponded to a local minimum in density at the magnetic equator. During that time period observations were uncovered of a local maximum in plasma density at the equator. Until IMAGE there has been no good opportunity to experimentally revisit this topic, however until now no direct evidence of a relevant equatorial process has been recognized near the plasmapause during early recovery conditions. It appears that evidence has now been found in both the Extreme Ultraviolet Imager and Radio Plasma Imager observations. The observations, conditions, and properties of what appears to be an equatorially trapped and enhanced density near the magnetic equator will be presented and discussed.

  6. Seasonal and longitudinal variation of large-scale topside equatorial plasma depletions

    Microsoft Academic Search

    M. A. Hei; R. A. Heelis; J. P. McClure

    2005-01-01

    We examine the large-scale properties of three classes of equatorial topside plasma depletions referred to as channels. In order of increasing zonal width and internal large-scale substructuring, we study simple channels, multichannels, and superchannels. We find that peaks in channel activity are centered on 0° (African sector) and 180° (Western Pacific sector). Superchannels are found to strongly dominate in the

  7. Dependence of electron trapping on bubble geometry in laser-plasma wakefield acceleration

    SciTech Connect

    Li, X. F.; Yu, Q.; Huang, S.; Zhang, F.; Kong, Q., E-mail: qkong@fudan.edu.cn [Applied Ion Beam Physics Laboratory, Key Laboratory of the Ministry of Education, Institute of Modern Physics, Fudan University, Shanghai 200433 (China); Gu, Y. J. [Applied Ion Beam Physics Laboratory, Key Laboratory of the Ministry of Education, Institute of Modern Physics, Fudan University, Shanghai 200433 (China); Institute of Physics of the ASCR, ELI-Beamlines Project, Na Slovance 2, 18221 Prague (Czech Republic); Kawata, S. [Department of Advanced Interdisciplinary Sciences, Utsunomiya University, 7-1-2 Yohtoh, Utsunomiya 321-8585 (Japan)

    2014-07-15

    The effect of bubble shape in laser-plasma electron acceleration was investigated. We showed the general existence of an ellipsoid bubble. The electromagnetic field in this bubble and its dependence on bubble shape were determined through theory. The electron-trapping cross-section for different bubble aspect ratios was studied in detail. When the shape of the bubble was close to spherical, the trapping cross-section reached to the maximum. When the bubble deviated from a spherical shape, the cross-section decreased until electron injection no longer occurred. These results were confirmed by particle-in-cell simulation.

  8. A modelling study of the latitudinal variations in the nighttime plasma temperatures of the equatorial topside ionosphere during

    E-print Network

    Paris-Sud XI, Université de

    of the equatorial topside ionosphere during northern winter at solar maximum G. J. Bailey1 , M. H. Denton1 , R. A in the nighttime plasma temperatures of the equatorial topside ionosphere dur- ing northern winter at solar maximum®rm that the crests observed near 15 latitude in the winter hemisphere are due to adiabatic heating and the troughs

  9. Plasma Quenching by Air during Single-Bubble Sonoluminescence David J. Flannigan and Kenneth S. Suslick*

    E-print Network

    Suslick, Kenneth S.

    Plasma Quenching by Air during Single-Bubble Sonoluminescence David J. Flannigan and Kenneth S of sudden and dramatic changes in single-bubble sonoluminescence (SBSL) intensity (i.e., radiant power, SL subnanosecond flashes of light at the point of maximum implosion: single-bubble sonoluminescence, SBSL.2

  10. The Study of the origin of broad plasma depletions in the equatorial F region

    NASA Astrophysics Data System (ADS)

    Oh, S.; Lee, W.; Kil, H.; Kwak, Y.; Paxton, L.; Zhang, Y.

    2013-12-01

    Broad plasma depletions (BPDs), plasma depletions broader than regular plasma bubbles, are occasionally detected by the Communication/Navigation Outage Forecasting System (C/NOFS) satellite. The BPD phenomenon is understood in association with either plasma bubbles or modulation of the F region height. This study presents the BPD events that are considered to be associated with the latter. The coincident observations of the ionosphere from space (C/NOFS and the first Republic of China satellite) and on the ground (radars and ionosondes) showed that significant fountain process or uplift of the ionosphere occurred in the regions where BPDs were detected. The coincident ionosonde observations in the American sector showed the rapid increase of the F region height and, eventually, the disappearance of the ionosphere at the time of the BPD detection. Some BPDs showed the association with large scale wave structures and storm-induced electric fields. Our observation results indicate that the satellite detection of BPDs can be understood in terms of the uplift of the F region height above the satellite altitude. The coincidence of bubbles often with BPDs is explained by the promotion of the bubble activity by the uplift of the ionosphere.

  11. Morphology of the postsunset vortex in the equatorial ionospheric plasma drift

    NASA Astrophysics Data System (ADS)

    Lee, Woo Kyoung; Kil, Hyosub; Kwak, Young-Sil; Paxton, Larry J.

    2015-01-01

    postsunset vortex in the equatorial ionosphere exhibits clockwise plasma motions after sunset in longitude (time) and altitude coordinates when the equatorial ionosphere is viewed looking northward. We describe the typical morphology of the postsunset vortex using incoherent scatter radar observations at Jicamarca in Peru during the previous solar maximum (2000-2002). A pronounced vortical plasma motion appears around 1700 LT along with the onset of the prereversal enhancement (PRE). The center of this vortex is located near an altitude of 270 km. A smaller-scale vortex also appears about 0.5 ~ 1 h later at higher altitudes. However, the morphology and occurrence time of this small vortex depend on the characteristics of the coherent backscatter region. We find that the earlier vortex is the major feature of the postsunset vortices because it is repeatable, associated with the PRE, and independent to the occurrence of the coherent backscatter region.

  12. Micro Dynamics of Pulsed Laser Induced Bubbles in Dusty Plasma Liquids

    SciTech Connect

    Teng, L.-W.; Tsai, C.-Y.; Tseng, Y.-P.; I Lin [Department of Physics, National Central University, Jhungli, Taiwan 32001 (China)

    2008-09-07

    We experimentally study the micro dynamics of the laser induced plasma bubble in a dusty plasma liquid formed by negatively charged dust particles suspended in a low pressure rf Ar glow discharge. The plume from the ablation of the suspended dust particles pushes away dust particle and generates a dust-free plasma bubble. It then travels downward. The spatio-temporal evolution of the dust density fluctuation surrounding the bubble is monitored by directly tracking dust motion through optical video microscopy. The micro dynamics of the bubble associated dust acoustic type solitary oscillation in the wake field is investigated and discussed.

  13. Electromagnetic Analysis of ITER Diagnostic Equatorial Port Plugs During Plasma Disruptions

    SciTech Connect

    Y. Zhai, R. Feder, A. Brooks, M. Ulrickson, C.S. Pitcher and G.D. Loesser

    2012-08-27

    ITER diagnostic port plugs perform many functionsincluding structural support of diagnostic systems under high electromagnetic loads while allowing for diagnostic access to the plasma. The design of diagnostic equatorial port plugs (EPP) are largely driven by electromagnetic loads and associate responses of EPP structure during plasma disruptions and VDEs. This paper summarizes results of transient electromagnetic analysis using Opera 3d in support of the design activities for ITER diagnostic EPP. A complete distribution of disruption loads on the Diagnostic First Walls (DFWs), Diagnostic Shield Modules (DSMs) and the EPP structure, as well as impact on the system design integration due to electrical contact among various EPP structural components are discussed.

  14. Kinetic Theory of Equilibrium Axisymmetric Collisionless Plasmas in Off-equatorial Tori around Compact Objects

    NASA Astrophysics Data System (ADS)

    Cremaschini, Claudio; Ková?, Ji?í; Slaný, Petr; Stuchlík, Zden?k; Karas, Vladimír

    2013-11-01

    The possible occurrence of equilibrium off-equatorial tori in the gravitational and electromagnetic fields of astrophysical compact objects has been recently proved based on non-ideal magnetohydrodynamic theory. These stationary structures can represent plausible candidates for the modeling of coronal plasmas expected to arise in association with accretion disks. However, accretion disk coronae are formed by a highly diluted environment, and so the fluid description may be inappropriate. The question is posed of whether similar off-equatorial solutions can also be determined in the case of collisionless plasmas for which treatment based on kinetic theory, rather than a fluid one, is demanded. In this paper the issue is addressed in the framework of the Vlasov-Maxwell description for non-relativistic, multi-species axisymmetric plasmas subject to an external dominant spherical gravitational and dipolar magnetic field. Equilibrium configurations are investigated and explicit solutions for the species kinetic distribution function are constructed, which are expressed in terms of generalized Maxwellian functions characterized by isotropic temperature and non-uniform fluid fields. The conditions for the existence of off-equatorial tori are investigated. It is proved that these levitating systems are admitted under general conditions when both gravitational and magnetic fields contribute to shaping the spatial profiles of equilibrium plasma fluid fields. Then, specifically, kinetic effects carried by the equilibrium solution are explicitly provided and identified here with diamagnetic energy-correction and electrostatic contributions. It is shown that these kinetic terms characterize the plasma equation of state by introducing non-vanishing deviations from the assumption of thermal pressure.

  15. Analytic model of electromagnetic fields around a plasma bubble in the blow-out regime

    NASA Astrophysics Data System (ADS)

    Yi, S. A.; Khudik, V.; Siemon, C.; Shvets, G.

    2013-01-01

    An analytic model of the electric and magnetic fields surrounding the nonlinear plasma "bubble" formed around the high-current electron bunch in a plasma wakefield accelerator is developed. The model, justified by the results of particle-in-cell simulations, accurately captures the thin high-density plasma sheath and extended return current layer surrounding the bubble. The resulting global fields inside and outside the bubble are used to investigate electron self-injection in a plasma with a smooth density gradient. It is shown that accurate description of the current/density sheaths is crucial for quantitative description of self-injection.

  16. Characteristics of the Plasma Distribution in Mercury's Equatorial Magnetosphere Derived from MESSENGER Magnetic Field and Plasma Observations

    NASA Astrophysics Data System (ADS)

    Korth, H.; Anderson, B. J.; Johnson, C. L.; Winslow, R. M.; Raines, J. M.; Slavin, J. A.; Purucker, M. E.; Zurbuchen, T.; Solomon, S. C.; McNutt, R. L.

    2012-12-01

    Localized reductions in the magnetic field associated with plasma pressure in Mercury's plasma sheet have been routinely observed by the Magnetometer on the MErcury Surface, Space ENvironment, Geochemistry, and Ranging (MESSENGER) spacecraft. We present a statistical analysis of near-equatorial magnetic depressions to derive the structure of Mercury's plasma sheet pressure. Because the plasma pressure in the magnetosphere correlates with solar wind density, the pressures were normalized to a Mercury heliocentric distance of 0.39 AU. A model magnetic field was used to map observations obtained on the ascending and descending orbit nodes to the magnetic equator, and the mapped equatorial distribution revealed the presence of plasma in a toroidal section extending on the nightside from dusk to dawn. Mapping the data to invariant magnetic latitude shows that the pressure is symmetric about the magnetic equator. The average pressure normalized for heliocentric distance is 1.45 nPa and exhibits a weak, 0.05 nPa/h, dusk-to-dawn gradient with local time. The plasma sheet pressure can vary between successive orbits by an order of magnitude. Unlike the predictions of some global simulations of Mercury's magnetosphere but consistent with observations by MESSENGER's Fast Imaging Plasma Spectrometer, the plasma enhancements do not form a closed distribution around the planet. This difference may arise from the idealized solar wind and interplanetary magnetic field conditions used in the simulations, conditions that maximize the size and stability of the magnetosphere and thus promote the formation of drift paths that close around the planet. For typical plasma sheet energies, 5 keV, the first adiabatic invariant for protons fails to be conserved even within 500 km altitude at midnight, implying that stochastic processes must be considered in plasma sheet transport.

  17. Relaxing melt and plasma bubbles in laser-pulsed metals

    NASA Astrophysics Data System (ADS)

    Dömer, H.; Bostanjoglo, O.

    2003-11-01

    Melting and ablation of aluminum, chromium, and nickel films by nanosecond laser pulses with fluences of 2.4-13 J/cm2 were tracked by high-speed transmission electron microscopy and selected area (20 ?mø) diffraction. Electron exposure time was 8 ns. At fluences causing no detected evaporation, short-range order in the melt, as probed by diffraction, shows up with a time lag of nanoseconds. At lower "evaporating" fluences, the material is ablated by exploding gas bubbles nucleating all over the melt within 5 ns. At sufficiently high laser fluences, a plasma is produced with an ionization degree >20%, varying on the micrometer scale, as revealed by dark-field imaging.

  18. Global equatorial ionospheric vertical plasma drifts measured by the AE-E satellite

    NASA Technical Reports Server (NTRS)

    Fejer, B. G.; De Paula, E. R.; Heelis, R. A.; Hanson, W. B.

    1995-01-01

    Ion drift meter observations from the Atmosphere Explorer E (AE-E) satellite during the period of January 1977 to December 1979 are used to study the dependence of equatorial (dip latitudes less than or equal to 7.5 deg) F region vertical plasma drifts (east-west electric fields) on solar activity, season, and longitude. The satellite-observed ion drifts show large day-to-day and seasonal variations. Solar cycle effects are most pronounced near the dusk sector with a large increase of the prereversal velocity enhancement from solar minimum to maximum. The diuurnal, seasonal, and solar cycle dependence of the logitudinally averaged drifts are consistent with results from the Jicamarca radar except near the June solstice when the AE-E nighttime downward velocities are significantly smaller than those observed by the radar. Pronounced presunrise downward drift enhancements are often observed over a large longituudinal range but not in the Peruvian equatorial region. The satellite data indicate that longitudinal variations are largest near the June solstice, particularly near dawn and dusk but are virtually absent during equinox. The longitudinal dependence of the AE-E vertical drifts is consistent with results from ionosonde data. These measurements were also used to develop a description of equatorial F region vertical drifts in four longitudinal sectors.

  19. Penetration Electric Field Generated Plasma Bubbles Tracked by VEFI and PLP on C/NOFS and Associated Scintillations

    NASA Astrophysics Data System (ADS)

    Basu, S.; Costa, E.; Pfaff, R. F.

    2011-12-01

    Plasma bubbles and scintillations were observed at the appropriate longitudes, namely in the Atlantic-sector, during the initial main phase (Basu et al., Radio Science, 2010) of complex CME-driven moderate magnetic storms that had a minimum Dst of - 60 nT at approximately 2300 UT on 3 August 2010. Fortunately, the C/NOFS satellite was near-perigee in this longitude sector during dusk and was able to intercept what was almost certainly the same bubble in two consecutive orbits. This allowed us to utilize the high resolution dc and ac electric fields from VEFI and plasma density measurements from PLP to track the evolution of the electric field and plasma density structure for the first time to elucidate the variability in the spectral characteristics in a freshly generated and mature bubble. In addition to the two-sloped density structure observed by Rodrigues et al. ( GRL, 2009), the most significant finding was the persistence of the electric field structuring at high frequencies observed in both dc and ac measurements. Such high frequency structures and their dynamics have great significance for the interpretation of radar measurements (Hysell et al., GRL, 2009) and for testing the predictions of instability theories at meter and sub-meter scale irregularities (Huba and Ossakow, JGR, 1979). The scintillation measurements at the Atlantic SCINDA sites, namely, Cape Verde closer to the magnetic equator in the Northern Hemisphere and Ascension Island near the southern crest of the equatorial anomaly shed light on the belt width of scintillations during a moderate magnetic storm in a period where climatologically scintillations are almost non-existent.

  20. Plasma turbulence disc circulating the equatorial region of the plasmasphere identified by the plasma wave detector (PWS) onboard the Akebono (EXOS-D) satellite

    Microsoft Academic Search

    Hiroshi Oya; Masahide Iizima; Akira Morioka

    1991-01-01

    For the observation data of the plasma wave turbulence detected by the PWS (Plasma Wave and Sounder Experiment) on board the EXOS-D (Akebono) satellite, the enhancements of the upper hybrid wave emission called equatorial enhancement of the plasma wave turbulence (EPWAT) that are characterized by the increasing level of the upper hybrid emissions are studied on their occurrence regions and

  1. Supra-bubble regime for laser acceleration of cold electron beams in tenuous plasma

    E-print Network

    Supra-bubble regime for laser acceleration of cold electron beams in tenuous plasma V. I. Geyko,1 I the most common scalings from the original Ref. 1 for this comparison; for more accurate models, see Refs

  2. Characteristics of the plasma distribution in Mercury's equatorial magnetosphere derived from MESSENGER Magnetometer observations

    NASA Astrophysics Data System (ADS)

    Korth, Haje; Anderson, Brian J.; Johnson, Catherine L.; Winslow, Reka M.; Slavin, James A.; Purucker, Michael E.; Solomon, Sean C.; McNutt, Ralph L., Jr.

    2012-12-01

    Localized reductions in the magnetic field associated with plasma pressure in Mercury's magnetospheric cusp and nightside plasma sheet have been routinely observed by the Magnetometer on the MErcury Surface, Space ENvironment, GEochemistry and Ranging (MESSENGER) spacecraft. We present a statistical analysis of near-equatorial magnetic depressions to derive the structure of Mercury's plasma sheet pressure. Because the plasma pressure in the magnetosphere correlates with solar wind density, the pressures were normalized to a Mercury heliocentric distance of 0.39 AU. A model magnetic field was used to map observations obtained on the ascending and descending orbit nodes to the magnetic equator and revealed the presence of plasma in a toroidal section extending on the nightside from dusk to dawn. Mapping the data to invariant magnetic latitude shows that the pressure is symmetric about the magnetic equator. The average pressure normalized for heliocentric distance is 1.45 nPa and exhibits a weak, 0.05 nPa/h, dusk-to-dawn gradient with local time. The plasma sheet pressure can vary between successive orbits by an order of magnitude. Unlike the predictions of some global simulations of Mercury's magnetosphere, the plasma enhancements do not form a closed distribution around the planet. This difference may arise from the idealized solar wind and interplanetary magnetic field conditions used in the simulations, which maximize the size and stability of the magnetosphere, thus promoting the formation of drift paths that close around the planet. For typical plasma sheet energies, 5 keV, the first adiabatic invariant for protons fails to be conserved even within 500 km altitude at midnight, implying that stochastic processes must be considered in plasma sheet transport.

  3. Electrons trajectories around a bubble regime in intense laser plasma interaction

    SciTech Connect

    Lu, Ding; Xie, Bai-Song; Ali Bake, Muhammad; Sang, Hai-Bo [Key Laboratory of Beam Technology and Materials Modification of the Ministry of Education, College of Nuclear Science and Technology, Beijing Normal University, Beijing 100875 (China)] [Key Laboratory of Beam Technology and Materials Modification of the Ministry of Education, College of Nuclear Science and Technology, Beijing Normal University, Beijing 100875 (China); Zhao, Xue-Yan [Key Laboratory of Beam Technology and Materials Modification of the Ministry of Education, College of Nuclear Science and Technology, Beijing Normal University, Beijing 100875 (China) [Key Laboratory of Beam Technology and Materials Modification of the Ministry of Education, College of Nuclear Science and Technology, Beijing Normal University, Beijing 100875 (China); Shanghai Institute of Optics and Fine Mechanics, Chinese Academy of Sciences, Shanghai 201800 (China); Wu, Hai-Cheng [Center for Applied Physics and Technology, Peking University, Beijing 100084 (China)] [Center for Applied Physics and Technology, Peking University, Beijing 100084 (China)

    2013-06-15

    Some typical electrons trajectories around a bubble regime in intense laser plasma interaction are investigated theoretically. By considering a modification of the fields and ellipsoid bubble shape due to the presence of residual electrons in the bubble regime, we study in detail the electrons nonlinear dynamics with or without laser pulse. To examine the electron dynamical behaviors, a set of typical electrons, which locate initially at the front of the bubble, on the transverse edge and at the bottom of the bubble respectively, are chosen for study. It is found that the range of trapped electrons in the case with laser pulse is a little narrower than that without laser pulse. The partial phase portraits for electrons around the bubble are presented numerically and their characteristic behaviors are discussed theoretically. Implication of our results on the high quality electron beam generation is also discussed briefly.

  4. Towards understanding plasma formation in liquid water via single bubble studies

    NASA Astrophysics Data System (ADS)

    Foster, John E.; Sommers, Bradley; Gucker, Sarah

    2015-01-01

    Plasma-in-water based technological approaches offer great potential to addressing a wide range of contaminants threatening the safety of freshwater reserves. Widespread application of plasma-based technologies, however require a better understanding of plasma formation processes in water and the nature of the plasma-driven chemistry in solution. In this paper, we survey the scope of the threat to freshwater via contamination from a variety of sources, the status of conventional treatment technologies, the promise of plasma-based water purification, and the pathway to understanding plasma formation in water through the study of single bubble breakdown physics. Plasma formation in bubbles lie at the heart of plasma formation in liquid water. We present findings from ongoing research at the University of Michigan aimed at understanding the nature of plasma formation in bubbles, which provides an avenue for not only understanding breakdown conditions, but also insight in reducing the magnitude of the breakdown voltage. These experiments also establish an approach to a standardized apparatus for the study of plasma discharges in bubbles. We also discuss approaches to controlling plasma-induced chemistry in liquid water.

  5. Plasmas in Multiphase Media: Bubble Enhanced Discharges in Liquids and Plasma/Liquid Phase Boundaries

    SciTech Connect

    Kushner, Mark Jay [University of Michigan] [University of Michigan

    2014-07-10

    In this research project, the interaction of atmospheric pressure plasmas with multi-phase media was computationally investigated. Multi-phase media includes liquids, particles, complex materials and porous surfaces. Although this investigation addressed fundamental plasma transport and chemical processes, the outcomes directly and beneficially affected applications including biotechnology, medicine and environmental remediation (e.g., water purification). During this project, we made advances in our understanding of the interaction of atmospheric pressure plasmas in the form of dielectric barrier discharges and plasma jets with organic materials and liquids. We also made advances in our ability to use computer modeling to represent these complex processes. We determined the method that atmospheric pressure plasmas flow along solid and liquid surfaces, and through endoscopic like tubes, deliver optical and high energy ion activation energy to organic and liquid surfaces, and produce reactivity in thin liquid layers, as might cover a wound. We determined the mechanisms whereby plasmas can deliver activation energy to the inside of liquids by sustaining plasmas in bubbles. These findings are important to the advancement of new technology areas such as plasma medicine

  6. Field-Reversed Bubble in Deep Plasma Channels for High-Quality Electron Acceleration

    NASA Astrophysics Data System (ADS)

    Pukhov, A.; Jansen, O.; Tueckmantel, T.; Thomas, J.; Kostyukov, I. Yu.

    2014-12-01

    We study hollow plasma channels with smooth boundaries for laser-driven electron acceleration in the bubble regime. Contrary to the uniform plasma case, the laser forms no optical shock and no etching at the front. This increases the effective bubble phase velocity and energy gain. The longitudinal field has a plateau that allows for monoenergetic acceleration. We observe as low as 10-3 rms relative witness beam energy uncertainty in each cross section and 0.3% total energy spread. By varying the plasma density profile inside a deep channel, the bubble fields can be adjusted to balance the laser depletion and dephasing lengths. Bubble scaling laws for the deep channel are derived. Ultrashort pancakelike laser pulses lead to the highest energies of accelerated electrons per Joule of laser pulse energy.

  7. Field-reversed bubble in deep plasma channels for high-quality electron acceleration.

    PubMed

    Pukhov, A; Jansen, O; Tueckmantel, T; Thomas, J; Kostyukov, I Yu

    2014-12-12

    We study hollow plasma channels with smooth boundaries for laser-driven electron acceleration in the bubble regime. Contrary to the uniform plasma case, the laser forms no optical shock and no etching at the front. This increases the effective bubble phase velocity and energy gain. The longitudinal field has a plateau that allows for monoenergetic acceleration. We observe as low as 10?³ rms relative witness beam energy uncertainty in each cross section and 0.3% total energy spread. By varying the plasma density profile inside a deep channel, the bubble fields can be adjusted to balance the laser depletion and dephasing lengths. Bubble scaling laws for the deep channel are derived. Ultrashort pancakelike laser pulses lead to the highest energies of accelerated electrons per Joule of laser pulse energy. PMID:25541776

  8. Bubble Bubble

    NSDL National Science Digital Library

    Mercer Mayer

    2009-11-11

    With magic bubble solution, a boy discovers that he can blow any kind of bubble imaginable: a kangaroo, a bird, a car, or a boat. Mercer Mayer's colorful illustrations enliven this engaging tale of mysterious bubbles.

  9. Dynamics of Ionospheric Plasma Depletions Measured by Airglow Emissions

    NASA Astrophysics Data System (ADS)

    Chapagain, Narayan; Taylor, Michael

    2010-10-01

    The earth's ionosphere most often shows the occurrence of highly irregular plasma density and velocity fluctuations with a large range of scale sizes and amplitudes. This night time ionospheric irregularities in the equatorial F-region is commonly referred to as equatorial spread F or plasma depletions (bubbles). In this presentation, we analyze the development and dynamics of the equatorial plasma depletions observed using OI (630.0 nm) airglow emissions measured by Utah State University all-sky CCD camera from different longitude sectors near equatorial regions including Christmas Island in Pacific Ocean, Ascension Island in Atlantic Ocean, and Brazil. The results illustrate the large day-to-day variability of the plasma bubbles evolution and development from all sites. The plasma bubble structures propagated eastward during the nighttime. The development of bubbles and the magnitude of the zonal drift velocities during the post midnight period were significantly longitudinal dependence.

  10. Radio-Tomographic Images of Post-midnight Equatorial Plasma Depletions

    NASA Astrophysics Data System (ADS)

    Hei, M. A.; Bernhardt, P. A.; Siefring, C. L.; Wilkens, M.; Huba, J. D.; Krall, J.; Valladares, C. E.; Heelis, R. A.; Hairston, M. R.; Coley, W. R.; Chau, J. L.

    2013-12-01

    For the first time, post-midnight equatorial plasma depletions (EPDs) have been imaged in the longitude-altitude plane using radio-tomography. High-resolution (~10 km × 10 km) electron-density reconstructions were created from total electron content (TEC) data using an array of receivers sited in Peru and the Multiplicative Algebraic Reconstruction Technique (MART) inversion algorithm. TEC data were obtained from the 150 and 400 MHz signals transmitted by the CERTO beacon on the C/NOFS satellite. In-situ electron density data from the C/NOFS CINDI instrument and electron density profiles from the UML Jicamarca ionosonde were used to generate an initial guess for the MART inversion, and also to constrain the inversion process. Observed EPDs had widths of 100-1000 km, spacings of 300-900 km, and often appeared 'pinched off' at the bottom. Well-developed EPDs appeared on an evening with a very small (4 m/s) Pre-Reversal-Enhancement (PRE), suggesting that postmidnight enhancements of the vertical plasma drift and/or seeding-induced uplifts (e.g. gravity waves) were responsible for driving the Rayleigh-Taylor Instability into the nonlinear regime on this night. On another night the Jicamarca ISR recorded postmidnight (~0230 LT) Eastward electric fields nearly twice as strong as the PRE fields seven hours earlier. These electric fields lifted the whole ionosphere, including embedded EPDs, over a longitude range ~14° wide. CINDI detected a dawn depletion in exactly the area where the reconstruction showed an uplifted EPD. Strong Equatorial Spread-F observed by the Jicamarca ionosonde during receiver observation times confirmed the presence of ionospheric irregularities.

  11. Energy enhancement of proton acceleration in combinational radiation pressure and bubble by optimizing plasma density

    SciTech Connect

    Bake, Muhammad Ali; Xie Baisong [Key Laboratory of Beam Technology and Materials Modification of the Ministry of Education, Beijing Normal University, Beijing 100875 (China); College of Nuclear Science and Technology, Beijing Normal University, Beijing 100875 (China); Shan Zhang [Department of Mathematics and Physics, Shijiazhuang Tiedao University, Shijiazhuang 050043 (China); Hong Xueren [College of Nuclear Science and Technology, Beijing Normal University, Beijing 100875 (China); College of Physics and Electronic Engineering, Northwest Normal University, Lanzhou 730070 (China); Wang Hongyu [Department of Physics, Anshan Normal University, Anshan 114005 (China); Shanghai Bright-Tech Information Technology Co. Ltd, Shanghai 200136 (China)

    2012-08-15

    The combinational laser radiation pressure and plasma bubble fields to accelerate protons are researched through theoretical analysis and numerical simulations. The dephasing length of the accelerated protons bunch in the front of the bubble and the density gradient effect of background plasma on the accelerating phase are analyzed in detail theoretically. The radiation damping effect on the accelerated protons energy is also considered. And it is demonstrated by two-dimensional particle-in-cell simulations that the protons bunch energy can be increased by using the background plasma with negative density gradient. However, radiation damping makes the maximal energy of the accelerated protons a little reduction.

  12. Can HF heating generate ESF bubbles?

    NASA Astrophysics Data System (ADS)

    Zawdie, K. A.; Huba, J. D.

    2014-12-01

    The injection of powerful HF waves into the ionosphere can lead to strong electron heating followed by a pressure perturbation which can locally reduce the plasma density. In the postsunset equatorial ionosphere, density perturbations can provide the seed to generate equatorial spread F (ESF) bubbles. In this paper, a modified version of the SAMI3/ESF ionosphere code is used to model the density depletions created by HF heating and to determine if ESF bubbles can be artificially generated. It is found that HF heating primarily redistributes plasma along the geomagnetic field and does not significantly perturb the flux tube integrated conductivities. Thus, HF heating does not appear to be a viable method to seed or generate ESF bubbles.

  13. A quiet time empirical model of equatorial vertical plasma drift in the Peruvian sector based on 150 km echoes

    NASA Astrophysics Data System (ADS)

    Alken, P.

    2009-02-01

    Equatorial vertical plasma drift is an important consequence of the E and F region dynamos. Understanding the climatology of vertical drift can provide significant insight into many ionospheric phenomena. In this study we present the first empirical model of vertical plasma drifts at 150 km altitude, observed by the Jicamarca Unattended Long-term studies of the Ionosphere and Atmosphere (JULIA) coherent scatter radar located in Peru. The model, called JULIA Vertical Drift Model (JVDM), describes the local time, seasonal, and solar flux behavior of the equatorial vertical drifts in the Peruvian sector. The model is valid from 0800 through 1600 local time, which is typically when JULIA makes vertical drift measurements. During very high solar flux conditions, however, the model is unreliable before 1000 local time owing to a lack of JULIA data. The model includes a climatology of the 150 km equatorial vertical drifts as well as an estimate of the day-to-day variability, which can be significant. The daytime drifts typically peak between 1000 and 1200 LT and have amplitudes of 25-30 m/s +/- 10 m/s. The model has been validated against the global empirical model of Scherliess and Fejer, with a total rms difference of under 4 m/s for 1000 to 1600 LT. This model will allow researchers to study daily variations in the equatorial electric field by subtracting the climatological mean. Model coefficients and software are available online at http://geomag.org/models and http://www.earthref.org.

  14. Phase transition to an opaque plasma in a sonoluminescing bubble.

    PubMed

    Kappus, Brian; Khalid, Shahzad; Chakravarty, Avik; Putterman, Seth

    2011-06-10

    Time-resolved spectrum measurements of a sonoluminescing Xe bubble reveal a transition from transparency to an opaque Planck blackbody. As the temperature is <10?000??K and the density is below liquid density, the photon scattering length is 10?000 times too large to explain its opacity. We resolve this issue with a model that reduces the ionization potential. According to this model, sonoluminescence originates in a new phase of matter with high ionization. Analysis of line emission from Xe* also yields evidence of phase segregation for this first-order transition inside a bubble. PMID:21770508

  15. Phase Transition to an Opaque Plasma in a Sonoluminescing Bubble

    NASA Astrophysics Data System (ADS)

    Kappus, Brian; Khalid, Shahzad; Chakravarty, Avik; Putterman, Seth

    2011-06-01

    Time-resolved spectrum measurements of a sonoluminescing Xe bubble reveal a transition from transparency to an opaque Planck blackbody. As the temperature is <10000K and the density is below liquid density, the photon scattering length is 10 000 times too large to explain its opacity. We resolve this issue with a model that reduces the ionization potential. According to this model, sonoluminescence originates in a new phase of matter with high ionization. Analysis of line emission from Xe* also yields evidence of phase segregation for this first-order transition inside a bubble.

  16. Generation of intense ultrashort midinfrared pulses by laser-plasma interaction in the bubble regime

    SciTech Connect

    Pai, C.-H.; Chang, Y.-Y.; Ha, L.-C.; Xie, Z.-H.; Chen, Y.-M.; Wang, J. [Institute of Atomic and Molecular Sciences, Academia Sinica, Taipei 10617, Taiwan (China); Department of Physics, National Central University, Jhongli 32001, Taiwan (China); Department of Physics, National Taiwan University, Taipei 10617, Taiwan (China); Lin, M.-W.; Chen, S.-Y. [Institute of Atomic and Molecular Sciences, Academia Sinica, Taipei 10617, Taiwan (China); Department of Physics, National Central University, Jhongli 32001, Taiwan (China); Lin, J.-M. [Institute of Atomic and Molecular Sciences, Academia Sinica, Taipei 10617, Taiwan (China); Department of Physics, National Central University, Jhongli 32001, Taiwan (China); Department of Physics, National Chung Cheng University, Chia-Yi 62102, Taiwan (China); Tsaur, G. [Department of Mathematics, Tunghai University, Taichung 40704, Taiwan (China); Chu, H.-H.; Chen, S.-H. [Department of Physics, National Central University, Jhongli 32001, Taiwan (China); Lin, J.-Y. [Department of Physics, National Chung Cheng University, Chia-Yi 62102, Taiwan (China)

    2010-12-15

    As an intense laser pulse propagates through an underdense plasma, the strong ponderomotive force pushes away the electrons and produces a trailing plasma bubble. In the meantime the pulse itself undergoes extreme nonlinear evolution that results in strong spectral broadening toward the long-wavelength side. By experiment we demonstrate that this process can be utilized to generate ultrashort midinfrared pulses with an energy three orders of magnitude larger than that produced by crystal-based nonlinear optics. The infrared pulse is encapsulated in the bubble before exiting the plasma, hence is not absorbed by the plasma. The process is analyzed experimentally with laser-plasma tomographic measurements and numerically with three-dimensional particle-in-cell simulation. Good agreement is found between theoretical estimation, numerical simulation, and experimental results.

  17. Periodic spacing between consecutive equatorial plasma bubbles J. J. Makela,1

    E-print Network

    Vadas, Sharon

    (GWs). The distribution of spacings compares favorably to the spectrum of GW induced traveling ionospheric disturbances (TIDs) measured by Vadas and Crowley (2010) from a similar geographic latitude structure with wavelength on the order of 200­400 km in the bottomside ionosphere whose spacing is echoed

  18. The Quantitative Analysis of Active Species Generated by Direct Current Plasma within Oxygen Bubbles

    NASA Astrophysics Data System (ADS)

    Ishii, Yoko; Ando, Mizuki; Takeuchi, Nozomi; Ikeda, Kei; Yasuoka, Koichi

    In this research, concentrations of hydrogen peroxide and dissolved ozone generated by direct current plasma within oxygen bubbles in water were measured. The current magnitude and water conductivity were changed from 1 to 7mA, and from 1 to 100 ?S/cm, respectively. The highest efficiency of hydrogen peroxide generation was 0.64g/kWh at 7mA with 100?S/cm solution. The concentration of dissolved ozone decreased with increasing the discharge current, and was almost zero when the current was higher than 5mA. Non-dimensional simulation revealed that the water vapor concentration in bubbles strongly affects the generation of active species. With a large current, the amount of water vaporized into the bubbles enlarged due to a large heat flux from plasma.

  19. Supra-bubble regime for laser acceleration of coldelectron beams in tenuous plasma

    SciTech Connect

    Geyko, V. I.; Dodin, I. Y.; Fisch, N. J.; Fraiman, G. M.

    2009-01-18

    Relativistic electrons can be accelerated by an ultraintense laser pulse in the "supra-bubble" regime, that is, in the blow-out regime ahead of the plasma bubble (as opposed to the conventional method, when particles remain inside the bubble). The acceleration is caused by the ponderomotive force of the pulse, via the so-called snow-plow mechanism. The maximum energy gain, ?? ~ ?g a, is attained when the particle Lorentz factor ? is initially about ?g/a, where ?g is the pulse group speed Lorentz factor, and a is the laser parameter, proportional to the laser field amplitude. The scheme operates at a ? ?g, yielding ?? of up to that via wakefield acceleration for the same plasma and laser parameters, ?? ~ ?2g. The interaction length is shorter than that for the wake field mechanism but grows with the particle energy, hindering acceleration in multiple stages.

  20. Storm-enhanced plasma density (SED) features, auroral and polar plasma enhancements, and rising topside bubbles of the 31 March 2001 superstorm

    Microsoft Academic Search

    Ildiko Horvath; Brian C. Lovell

    2011-01-01

    The significant plasma structuring (due to bubbles) detected over AnconThe TOI feature development in both hemispheres during E-field penetrationThe temporal variations of auroral and polar plasma enhancements

  1. The ESPERIA equatorial, electromagnetic, plasma, and particle mission concerned with detecting preseismic related signals.

    NASA Astrophysics Data System (ADS)

    Sgrigna, V.; Esperia Team

    ESPERIA is an equatorial mission planned with a LEO small-satellite and a multi-instrument payload. The project has been ideally conceived to define the near-Earth electromagnetic, plasma, and particle environment, both in steady-state and perturbed-state conditions. In recent times has been observed that either Earth's interior processes or near-Earth space phenomena have a privileged and sensitive zone of investigation constituted by the ionosphere-magnetosphere transition region, at altitudes ranging around 500(1000 km. In fact, sun and cosmic rays as well as, seismic, anthropogenic and thunderstorm activities, influence the structure and dynamics of the zone. These external and internal contributions play an important role in defining the particle and electromagnetic field character of the region, both in steady-state and perturbed-state conditions. So, a suitable monitoring of the topside ionosphere may give an help in studying many important physical phenomena as pre-earthquake and anthropogenic electromagnetic emissions, solar wind and flares, as well as in mapping the geomagnetic field. The ESPERIA Phase A Study has been performed by an International Consortium lead by the University Roma Tre, within the Earth observation program for small scientific missions of the Italian Space Agency (ASI). The scientific objectives of the study are to plan an EM, plasma, and particle mission concerned with detecting tectonic, anthropogenic, and preseismic related EM signals. The primary aim of the mission is to study ionospheric and magnetospheric effects caused by seismicity to develop methods for the evaluation of seismic risk (providing for disaster assessment) and give contribution in earthquake forecasting studies. A secondary objective is the study of electromagnetic emissions of anthropogenic origin (power line harmonic radiation, VLF and HF transmitters) and their influence in the ionosphere and magnetosphere. To achieve the objectives with maximum reliability, ESPERIA is based with strong emphasis on coordinated, simultaneous, and continuous ground-based and space observations, as well as on mutual data comparison with other missions of similar quality. On board the satellite ULF(HF electromagnetic fields, fluxes of charged particle (200 keV(GeV), and ionospheric plasma temperature and density will be detected. Ground-based measurements of mechanical (tilt and strain) and electromagnetic fields will be carried out in several test areas of the Earth's surface.

  2. Effect of Ar bubbling during plasma electrolytic oxidation of AZ31B magnesium alloy in silicate electrolyte

    NASA Astrophysics Data System (ADS)

    Lee, Junghoon; Kim, Yonghwan; Chung, Wonsub

    2012-10-01

    Argon gas was bubbled during plasma electrolytic oxidation (PEO) treatment of magnesium alloy in a silicate solution. The appearance of arcs and plasma discharging was locally concentrated on the magnesium alloy surface and phase fraction of Mg2SiO4 in the oxide layer was increased due to Argon gas bubbling. The higher energy density of the Ar plasma atmosphere is believed to contribute to the effective formation of the high temperature phase (Mg2SiO4), particularly in the inner layer. Furthermore, the PEO treated Mg alloy with Ar bubbling showed improved corrosion resistance by a change of open pores structure.

  3. Analytic model of electron self-injection in a plasma wakefield accelerator in the strongly nonlinear bubble regime

    NASA Astrophysics Data System (ADS)

    Yi, S. A.; Khudik, V.; Siemon, C.; Shvets, G.

    2012-12-01

    Self-injection of background electrons in plasma wakefield accelerators in the highly nonlinear bubble regime is analyzed using particle-in-cell and semi-analytic modeling. It is shown that the return current in the bubble sheath layer is crucial for accurate determination of the trapped particle trajectories.

  4. Analytic model of electron self-injection in a plasma wakefield accelerator in the strongly nonlinear bubble regime

    SciTech Connect

    Yi, S. A.; Khudik, V.; Siemon, C.; Shvets, G. [Department of Physics and Institute for Fusion Studies, University of Texas at Austin, One University Station C1500, Austin, Texas (United States)

    2012-12-21

    Self-injection of background electrons in plasma wakefield accelerators in the highly nonlinear bubble regime is analyzed using particle-in-cell and semi-analytic modeling. It is shown that the return current in the bubble sheath layer is crucial for accurate determination of the trapped particle trajectories.

  5. Multi-wavelength Emission from the Fermi Bubbles. I. Stochastic Acceleration from Background Plasma

    NASA Astrophysics Data System (ADS)

    Cheng, K. S.; Chernyshov, D. O.; Dogiel, V. A.; Ko, C. M.

    2014-07-01

    We analyze processes of electron acceleration in the Fermi bubbles in order to define parameters and restrictions of the models, which are suggested for the origin of these giant radio and gamma-ray structures. In the case of the leptonic origin of the nonthermal radiation from the bubbles, these electrons should be produced somehow in situ because of the relatively short lifetime of high-energy electrons, which lose their energy by synchrotron and inverse-Compton processes. It has been suggested that electrons in bubbles may be accelerated by shocks produced by tidal disruption of stars accreting onto the central black hole or a process of re-acceleration of electrons ejected by supernova remnants. These processes will be investigated in subsequent papers. In this paper, we focus on in situ stochastic (Fermi) acceleration by a hydromagnetic/supersonic turbulence, in which electrons can be directly accelerated from the background plasma. We showed that the acceleration from the background plasma is able to explain the observed fluxes of radio and gamma-ray emission from the bubbles, but the range of permitted parameters of the model is strongly restricted.

  6. Analytic model of electron self-injection in a plasma wakefield accelerator in the strongly nonlinear bubble regime

    NASA Astrophysics Data System (ADS)

    Yi, Sunghwan; Khudik, Vladimir; Shvets, Gennady

    2012-10-01

    We study self-injection into a plasma wakefield accelerator in the blowout (or bubble) regime, where the bubble evolves due to background density inhomogeneities. To explore trapping, we generalize an analytic model for the wakefields inside the bubble [1] to derive expressions for the fields outside. With this extended model, we show that a return current in the bubble sheath layer plays an important role in determining the trapped electron trajectories. We explore an injection mechanism where bubble growth due to a background density downramp causes reduction of the electron Hamiltonian in the co-moving frame, trapping the particle in the dynamically deepening potential well [2]. Model calculations agree quantitatively with PIC simulations on the bubble expansion rate required for trapping, as well as the range of impact parameters for which electrons are trapped. This is an improvement over our previous work [3] using a simplified spherical bubble model, which ignored the fields outside of the bubble and hence overestimated the expansion rate required for trapping. [4pt] [1] W. Lu et al., Phys. Plasmas 13, 056709 (2006).[0pt] [2] S. Kalmykov et al., Phys. Rev. Lett 103, 135004 (2009).[0pt] [3] S.A. Yi et al., Plasma Phys. Contr. Fus. 53, 014012 (2011).

  7. Seeding equatorial spread F with turbulent gravity waves: Phasing effects

    NASA Astrophysics Data System (ADS)

    Wu, T.-W.; Huba, J. D.; Krall, J.; Fritts, D. C.; Laughman, B.

    2015-01-01

    The Naval Research Laboratory (NRL) SAMI3/equatorial spread F (ESF) three-dimensional ionosphere model is used to study the initiation and development of the large-scale plasma bubbles in the postsunset equatorial F region by turbulent gravity waves. The gravity wave turbulence is obtained from a three-dimensional anelastic, finite-volume model. We show that the phasing of gravity waves at conjugate regions in the ionosphere can enhance (in phase) or reduce (out of phase) the effective seed of the instability. The nonlocalized nature of the effective seed may contribute to the observed day-to-day variability of ESF. Additionally, we find that the zonal and vertical wind perturbations associated with the gravity waves are most effective in seeding ESF bubbles; perturbations of the meridional wind are relatively ineffective.

  8. Insights in the laser-induced breakdown spectroscopy signal generation underwater using dual pulse excitation — Part I: Vapor bubble, shockwaves and plasma

    NASA Astrophysics Data System (ADS)

    Lazic, V.; Laserna, J. J.; Jovicevic, S.

    2013-04-01

    Plasma and vapor bubble formation and evolution after a nanosecond laser pulse delivered to aluminum targets inside water were studied by fast photography. This technique was also applied to monitor the plasma produced by a second laser pulse and for different interpulse delays. The bubble growth was evident only after 3 ?s from the first laser pulse and the bubble shape changed during expansion and collapse cycles. The evolution and propagation of the initial shockwave and its reflections both from the back sample surface and cell walls were detected by Schlieren photography. The primary plasma develops in two phases: violent particle expulsion and ionization during the first ?s, followed by slow plasma growth from the ablation crater into the evolving vapor bubble. The shape of the secondary plasma strongly depends on the inner bubble pressure whereas the particle expulsion into the expanded bubble is much less evident. Both the primary and secondary plasma have similar duration of about 30 ?s. Detection efficiency of the secondary plasma is much reduced by light refraction at the curved bubble-water interface, which behaves as a negative lens; this leads to an apparent reduction of the plasma dimensions. Defocusing power of the bubble lens increases with its expansion due to the lowering of the vapor's refraction index with respect to that of the surrounding liquid (Lazic et al., 2012 [1]). Smell's reflections of secondary plasma radiation at the expanded bubble wall redistribute the detected intensity on a wavelength-dependent way and allow gathering of the emission also from the external plasma layer that otherwise, would not enter into the optical system.

  9. Lightning-induced lower-hybrid turbulence and trapped Extremely Low Frequency (ELF) electromagnetic waves observed in deep equatorial plasma density depletions during intense magnetic storms

    Microsoft Academic Search

    M. Malingre; J.-J. Berthelier; R. Pfaff; J. Jasperse; M. Parrot

    2008-01-01

    During the early phase of the intense magnetic storm of 7–11 November 2004, the DEMETER satellite encountered large-scale equatorial plasma density depletions with density decreases of two or three orders of magnitude. Wave measurements carried out inside these depletions show the occurrence of broadband and localized lower-hybrid turbulence triggered by whistlers propagating from thunderstorm lightning occurring below the orbit path.

  10. Lightning-induced lower-hybrid turbulence and trapped Extremely Low Frequency (ELF) electromagnetic waves observed in deep equatorial plasma density depletions during intense magnetic storms

    Microsoft Academic Search

    M. Malingre; J.-J. Berthelier; R. Pfaff; J. Jasperse; M. Parrot

    2008-01-01

    During the early phase of the intense magnetic storm of 7-11 November 2004, the DEMETER satellite encountered large-scale equatorial plasma density depletions with density decreases of two or three orders of magnitude. Wave measurements carried out inside these depletions show the occurrence of broadband and localized lower-hybrid turbulence triggered by whistlers propagating from thunderstorm lightning occurring below the orbit path.

  11. The dependence of pulsating auroral events on energetic electrons and cold plasma near the equatorial plane

    SciTech Connect

    Nemzek, R.J.; Belian, R.D.; McComas, D.J.; Thomsen, M.F. [Los Alamos National Lab., NM (United States); Nakamura, R.; Baker, D.N. [National Aeronautics and Space Administration, Greenbelt, MD (United States). Goddard Space Flight Center; Yamamoto, T. [Institute of Space and Astronautical Science, Sagamihara (Japan)

    1992-10-01

    Pulsating auroras are a substorm recovery phase phenomenon, occurring shortly after an auroral breakup. The current theory of the pulsating aurora involves a ``relaxation oscillator`` mechanism requiring a population of high-energy (10`s of keV) electrons and a low-energy plasma number density on the order of a few particles per cm{sup 3}. We investigated this relationship by comparing energetic electron and plasma data from a geosynchronous satellite to pulsating auroras recorded by an all-sky video camera which contained the satellite`s ionospheric conjugate point in its field of view. Pulsating auroral events were generally closely connected to substorm injections on the satellite, but there was no clear correlation with changes in plasma density. During all of the events the density was in an acceptable range for the relaxation oscillator mechanism to function. The relationship to substorm injections impiles that the pulsating aurora can be used to map the substorm injection region down to the ionosphere. An unusual diminishing of the pulsating aurora during the growth phase of a subsequent substorm was also discovered.

  12. The dependence of pulsating auroral events on energetic electrons and cold plasma near the equatorial plane

    SciTech Connect

    Nemzek, R.J.; Belian, R.D.; McComas, D.J.; Thomsen, M.F. (Los Alamos National Lab., NM (United States)); Nakamura, R.; Baker, D.N. (National Aeronautics and Space Administration, Greenbelt, MD (United States). Goddard Space Flight Center); Yamamoto, T. (Institute of Space and Astronautical Science, Sagamihara (Japan))

    1992-01-01

    Pulsating auroras are a substorm recovery phase phenomenon, occurring shortly after an auroral breakup. The current theory of the pulsating aurora involves a relaxation oscillator'' mechanism requiring a population of high-energy (10's of keV) electrons and a low-energy plasma number density on the order of a few particles per cm{sup 3}. We investigated this relationship by comparing energetic electron and plasma data from a geosynchronous satellite to pulsating auroras recorded by an all-sky video camera which contained the satellite's ionospheric conjugate point in its field of view. Pulsating auroral events were generally closely connected to substorm injections on the satellite, but there was no clear correlation with changes in plasma density. During all of the events the density was in an acceptable range for the relaxation oscillator mechanism to function. The relationship to substorm injections impiles that the pulsating aurora can be used to map the substorm injection region down to the ionosphere. An unusual diminishing of the pulsating aurora during the growth phase of a subsequent substorm was also discovered.

  13. An equatorial scintillation model

    Microsoft Academic Search

    E. J. Fremouw; R. E. Robins

    1985-01-01

    Radiowave scintillation in the presence of natural and\\/or high altitude nuclear disturbances has the potential to disrupt numerous transionospheric radio and radar systems. This report develops a model characterizing the plasma density irregularities that produce scintillation in the naturally disturbed equatorial F layer. The model has been incorporated into Program WBMOD along with subroutines for computing both link geometry and

  14. On the Azimuthal Variation of Core Plasma in the Equatorial Magnetosphere

    NASA Technical Reports Server (NTRS)

    Gallagher, D. L.; Craven, P. D.; Comfort, R. H.; Moore, T. E.

    1995-01-01

    Previous results of plasmapause position surveys have been synthesized into a description of the underlying global distribution of plasmasphere-like or core plasma densities unique to a steady state magnetosphere. Under these steady conditions, the boundary between high- and low-density regions is taken to represent the boundary between diurnal near-corotation and large-scale circulation streamlines that traverse the entire magnetosphere. Results indicate a boundary that has a pronounced bulge in the dusk sector that is rotated westward and markedly reduced in size at increased levels of geomagnetic activity (and presumably magnetospheric convection). The derived profile is empirical confirmation of an underlying 'tear drop' distribution of core plasma, which is valid only for prolonged steady conditions and is somewhat different from that associated with the simple superposition of sunward flow and corotation, both in its detailed shape and in its varying orientation. Variation away from the tear drop profile suggests that magnetospheric circulation departs from a uniform flow field, having a radial dependence with respect to the Earth that is qualitatively consistent with electrostatic shielding of the convection electric field and which is rotated westward at increased levels of geophysical activity.

  15. Observations and Simulations of Formation of Broad Plasma Depletions Through Merging Process

    NASA Technical Reports Server (NTRS)

    Huang, Chao-Song; Retterer, J. M.; Beaujardiere, O. De La; Roddy, P. A.; Hunton, D.E.; Ballenthin, J. O.; Pfaff, Robert F.

    2012-01-01

    Broad plasma depletions in the equatorial ionosphere near dawn are region in which the plasma density is reduced by 1-3 orders of magnitude over thousands of kilometers in longitude. This phenomenon is observed repeatedly by the Communication/Navigation Outage Forecasting System (C/NOFS) satellite during deep solar minimum. The plasma flow inside the depletion region can be strongly upward. The possible causal mechanism for the formation of broad plasma depletions is that the broad depletions result from merging of multiple equatorial plasma bubbles. The purpose of this study is to demonstrate the feasibility of the merging mechanism with new observations and simulations. We present C/NOFS observations for two cases. A series of plasma bubbles is first detected by C/NOFS over a longitudinal range of 3300-3800 km around midnight. Each of the individual bubbles has a typical width of approx 100 km in longitude, and the upward ion drift velocity inside the bubbles is 200-400 m/s. The plasma bubbles rotate with the Earth to the dawn sector and become broad plasma depletions. The observations clearly show the evolution from multiple plasma bubbles to broad depletions. Large upward plasma flow occurs inside the depletion region over 3800 km in longitude and exists for approx 5 h. We also present the numerical simulations of bubble merging with the physics-based low-latitude ionospheric model. It is found that two separate plasma bubbles join together and form a single, wider bubble. The simulations show that the merging process of plasma bubbles can indeed occur in incompressible ionospheric plasma. The simulation results support the merging mechanism for the formation of broad plasma depletions.

  16. Plasma and Field Observations at the Day-Side, Equatorial Magnetopause, Boundary Layers and Magnetosphere

    NASA Technical Reports Server (NTRS)

    Chandler, M. O.; Craven, P. D.; Moore, T. E.; Coffey, V. N.; Whitaker, Ann F. (Technical Monitor)

    2001-01-01

    The Polar spacecraft's orbit has precessed in latitude to an orientation that places it at the dayside magnetopause every 18 hours. In this configuration the various regions near the magnetopause(LLBL, turbulent boundary layer, magnetosphere, and magnetosheath) are sampled with high temporal and spatial resolution. These observational periods-ranging from several minutes to more than two hours-provide an unprecedented look at plasma conditions in these regions. Initial analysis of the low-energy ion data from TIDE reveal plasmaspheric-like ions within the turbulent boundary layer. Within this layer, circularly polarized waves accelerate these ions to 30-40 kilometers per second perpendicular to the local magnetic field. These relatively high velocities allow the H(+) to be observed above the -2V spacecraft potential. They also put the low-density O(+) in the higher-energy, higher sensitivity channels such that densities of order 10e-2 can be observed.

  17. Diagnostics of equatorial and low latitude ionosphere by TEC mapping over Brazil

    NASA Astrophysics Data System (ADS)

    Takahashi, H.; Costa, S.; Otsuka, Y.; Shiokawa, K.; Monico, J. F. G.; Paula, E.; Nogueira, P.; Denardini, C. M.; Becker-Guedes, F.; Wrasse, C. M.; Ivo, A. S.; Gomes, V. C. F.; Gargarela, W.; Sant'Anna, N.; Gatto, R.

    2014-08-01

    The total electron content (TEC) in the equatorial and low-latitude ionosphere over Brazil was monitored in two dimensions by using 2011 data from the ground-based global navigation satellite system (GNSS) receiver network operated by the Brazilian Institute for Geography and Statistics. It was possible to monitor the spatial and temporal variations in TEC over Brazil continuously during both day and night with a temporal interval of 10 min and a spatial resolution of about 400 km. The daytime equatorial ionization anomaly (EIA) and post-sunset plasma enhancement (PS-EIA) were monitored over an area corresponding to a longitudinal extension of 4000 km in South America. Considerable day-to-day variation was observed in EIA and PS-EIA. A large latitudinal and longitudinal gradient of TEC indicated a significant ionospheric range error in application of the GNSS positioning system. Large-scale plasma bubbles after sunset were also mapped over a wide range. Depletions with longitudinally separated by more than 800 km were observed. They were extended by more than 2000 km along the magnetic field lines and drifted eastward. It is expected that 2-dimensional TEC mapping can serve as a useful tool for diagnosing ionospheric weather, such as temporal and spatial variation in the equatorial plasma trough and crest, and particularly for monitoring the dynamics of plasma bubbles.

  18. Electron injection and acceleration in the plasma bubble regime driven by an ultraintense laser pulse combined with using dense-plasma wall and block

    NASA Astrophysics Data System (ADS)

    Zhao, Xue-Yan; Xie, Bai-Song; Wu, Hai-Cheng; Zhang, Shan; Hong, Xue-Ren; Aimidula, Aimierding

    2012-03-01

    An optimizing and alternative scheme for electron injection and acceleration in the wake bubble driven by an ultraintense laser pulse is presented. In this scheme, the dense-plasma wall with an inner diameter matching the expected bubble size is placed along laser propagation direction. Meanwhile, a dense-plasma block dense-plasma is adhered inward transversely at some certain position of the wall. Particle-in-cell simulations are performed, which demonstrate that the block plays an important role in the first electron injection and acceleration. The result shows that a collimated electron bunch with a total number of about 4.04×108?m-1 can be generated and accelerated stably to 1.61 GeV peak energy with 2.6% energy spread. The block contributes about 50% to the accelerated electron injection bunch by tracing and sorting statistically the source.

  19. Equatorial Guinea.

    PubMed

    1989-03-01

    Equatorial Guinea is situated on the Gulf of Guinea along the west African coast between Cameroon and Gabon. The people are predominantly of Bantu origin. The country's ties with Spain are significant; in 1959, it became the Spanish Equatorial region ruled by Spain's commissioner general. Recent political developments in Equatorial Guinea include the formation of the Democratic Party for Equatorial Guinea in July of 1987 and the formation of a 60-member unicameral Chamber of Representatives of the People in 1983. Concerning the population, 83% of the people are Catholic and the official language is Spanish. Poverty and serious health, education and sanitary problems exist. There is no adequate hospital and few trained physicians, no dentists, and no opticians. Malaria is endemic and immunization for yellow fever is required for entrance into the country. The water is not potable and many visitors to the country bring bottled water. The tropical climate of Equatorial Guinea provides the climate for the country's largest exports and source of economy; cacao, wood and coffee. Although the country, as a whole, has progressed towards developing a participatory political system, there are still problems of governmental corruption in the face of grave health and welfare conditions. In recent years, the country has received assistance from the World Bank and the United States to aid in its development. PMID:12177983

  20. Concurrence of monoenergetic electron beams and bright X-rays from an evolving laser-plasma bubble.

    PubMed

    Yan, Wenchao; Chen, Liming; Li, Dazhang; Zhang, Lu; Hafz, Nasr A M; Dunn, James; Ma, Yong; Huang, Kai; Su, Luning; Chen, Min; Sheng, Zhengming; Zhang, Jie

    2014-04-22

    Desktop laser plasma acceleration has proven to be able to generate gigaelectronvolt-level quasi-monoenergetic electron beams. Moreover, such electron beams can oscillate transversely (wiggling motion) in the laser-produced plasma bubble/channel and emit collimated ultrashort X-ray flashes known as betatron radiation with photon energy ranging from kiloelectronvolts to megaelectronvolts. This implies that usually one cannot obtain bright betatron X-rays and high-quality electron beams with low emittance and small energy spread simultaneously in the same accelerating wave bucket. Here, we report the first (to our knowledge) experimental observation of two distinct electron bunches in a single laser shot, one featured with quasi-monoenergetic spectrum and another with continuous spectrum along with large emittance. The latter is able to generate high-flux betatron X-rays. Such is observed only when the laser self-guiding is extended over 4 mm at a fixed plasma density (4 × 10(18) cm(-3)). Numerical simulation reveals that two bunches of electrons are injected at different stages due to the bubble evolution. The first bunch is injected at the beginning to form a stable quasi-monoenergetic electron beam, whereas the second one is injected later due to the oscillation of the bubble size as a result of the change of the laser spot size during the propagation. Due to the inherent temporal synchronization, this unique electron-photon source can be ideal for pump-probe applications with femtosecond time resolution. PMID:24711405

  1. Concurrence of monoenergetic electron beams and bright X-rays from an evolving laser-plasma bubble

    PubMed Central

    Yan, Wenchao; Chen, Liming; Li, Dazhang; Zhang, Lu; Hafz, Nasr A. M.; Dunn, James; Ma, Yong; Huang, Kai; Su, Luning; Chen, Min; Sheng, Zhengming; Zhang, Jie

    2014-01-01

    Desktop laser plasma acceleration has proven to be able to generate gigaelectronvolt-level quasi-monoenergetic electron beams. Moreover, such electron beams can oscillate transversely (wiggling motion) in the laser-produced plasma bubble/channel and emit collimated ultrashort X-ray flashes known as betatron radiation with photon energy ranging from kiloelectronvolts to megaelectronvolts. This implies that usually one cannot obtain bright betatron X-rays and high-quality electron beams with low emittance and small energy spread simultaneously in the same accelerating wave bucket. Here, we report the first (to our knowledge) experimental observation of two distinct electron bunches in a single laser shot, one featured with quasi-monoenergetic spectrum and another with continuous spectrum along with large emittance. The latter is able to generate high-flux betatron X-rays. Such is observed only when the laser self-guiding is extended over 4 mm at a fixed plasma density (4 × 1018 cm?3). Numerical simulation reveals that two bunches of electrons are injected at different stages due to the bubble evolution. The first bunch is injected at the beginning to form a stable quasi-monoenergetic electron beam, whereas the second one is injected later due to the oscillation of the bubble size as a result of the change of the laser spot size during the propagation. Due to the inherent temporal synchronization, this unique electron–photon source can be ideal for pump–probe applications with femtosecond time resolution. PMID:24711405

  2. Gravity wave and tidal influences on equatorial spread F based on observations during the Spread F Experiment (SpreadFEx)

    NASA Astrophysics Data System (ADS)

    Fritts, D. C.; Vadas, S. L.; Riggin, D. M.; Abdu, M. A.; Batista, I. S.; Takahashi, H.; Medeiros, A.; Kamalabadi, F.; Liu, H.-L.; Fejer, B. G.; Taylor, M. J.

    2008-10-01

    The Spread F Experiment, or SpreadFEx, was performed from September to November 2005 to define the potential role of neutral atmosphere dynamics, primarily gravity waves propagating upward from the lower atmosphere, in seeding equatorial spread F (ESF) and plasma bubbles extending to higher altitudes. A description of the SpreadFEx campaign motivations, goals, instrumentation, and structure, and an overview of the results presented in this special issue, are provided by Fritts et al. (2008a). The various analyses of neutral atmosphere and ionosphere dynamics and structure described in this special issue provide enticing evidence of gravity waves arising from deep convection in plasma bubble seeding at the bottomside F layer. Our purpose here is to employ these results to estimate gravity wave characteristics at the bottomside F layer, and to assess their possible contributions to optimal seeding conditions for ESF and plasma instability growth rates. We also assess expected tidal influences on the environment in which plasma bubble seeding occurs, given their apparent large wind and temperature amplitudes at these altitudes. We conclude 1) that gravity waves can achieve large amplitudes at the bottomside F layer, 2) that tidal winds likely control the orientations of the gravity waves that attain the highest altitudes and have the greatest effects, 3) that the favored gravity wave orientations enhance most or all of the parameters influencing plasma instability growth rates, and 4) that gravity wave and tidal structures acting together have an even greater potential impact on plasma instability growth rates and plasma bubble seeding.

  3. Equatorial Sundial

    NSDL National Science Digital Library

    McDonald Observatory

    2008-01-01

    In this activity, learners make an equatorial sundial, which is simple to construct and teaches fundamental astronomical concepts. Learners use the provided template and a straw to build the sundial. Then, learners take the sundial outside on a sunny day and measure the time at least fours time in one day. They also compare these measurements to the "clock" time. Learners can experiment with their sundials during different months as well. This lesson guide includes background information about Nabta, an Egyptian Stonehenge.

  4. Equatorial Guinea.

    PubMed

    1984-06-01

    Attention in this discussion of Equatorial Guinea is directed to the following: the people, history, geography, government, political conditions, the economy, foreign relations, and relations between the US and Equatorial Guinea. The population was estimated at 304,000 in 1983 and the annual growth rate was estimated in the range of 1.7-2.5. The infant mortality rate is 142.9/1000 with a life expectancy of 44.4 years for males and 47.6 years for females. The majority of the Equatoguinean people are of Bantu origin. The largest tribe, the Fang, is indigenous to the mainland, although many now also live on Bioko Island. Portuguese explorers found the island of Bioko in 1471, and the Portuguese retained control until 1778, when the island, adjacent islets, and the commercial rights to the mainland between the Niger and Ogooue Rivers were ceded to Spain. Spain lacked the wealth and the interest to develop an extensive economic infrastructure in Equatorial Guinea during the 1st half of this century, but the Spanish did help Equatorial Guinea achieve 1 of the highest literacy rates in Africa. They also founded a good network of health care facilities. In March 1968, under pressure from Guinean nationalists, Spain announced that it would grant independence to Equatorial Guinea as rapidly as possible. A referendum was held on August 11, 1968, and 63% of the electorate voted in favor of the constitution, which provided for a government with a general assembly and presidentially appointed judges in the Supreme Court. After the coup in August 1979, power was placed in the hands of a Supreme Military Council. A new constitution came into effect after a popular vote in August 1982, abolishing the Supreme Military Council. Under the terms of the constitution, the president was given extensive powers. By the end of 1983, a 60-member Chamber of Representatives of the people had been formed. The government, which is credited with restoring greater personal freedom, is regarded favorably by the populace. The economy is based on 3 products -- cacao, wood, and coffee. These are exported to spain and other European countries. There is little industry, and the local market for industrial products is small. The government wants to expand the role of free enterprise and to promote foreign investment. The potential exists for a viable ariculture-based, export-oriented economy. The US provides over $1 million annually in economic assistance, primarily in the field of agricultural development to assist in production of cash and food crops. PMID:12178092

  5. Synchrotron Radiation from a Laser Plasma Accelerator in the Bubble Regime

    NASA Astrophysics Data System (ADS)

    Kneip, S.; McGuffey, C.; Chvykov, V.; Dollar, F.; Kalintchenko, G.; Maksimchuk, T.; Mangles, S. P. D.; Matsuoka, T.; Nagel, S. R.; Palmer, C. A. J.; Schreiber, J.; Ta Phuoc, K.; Thomas, A. G. R.; Krushelnick, K.; Najmudin, Z.

    2010-11-01

    A laser wakefield accelerator is shown to operate in the highly non-linear bubble regime, following the characteristic scaling of energy gain with density and leading to monoenergetic electron beams with up to 400 MeV and hundreds of pC charge. The bubble acts at the same time as a miniature undulator, causing the electrons to give off a beam of betatron x-rays with milliradian divergence, ?m source size, 1-100 keV photon energy and 1022 ph/mm2/mrad2s/0.1% BW.

  6. An equatorial scintillation model

    NASA Astrophysics Data System (ADS)

    Fremouw, E. J.; Robins, R. E.

    1985-09-01

    Radiowave scintillation in the presence of natural and/or high altitude nuclear disturbances has the potential to disrupt numerous transionospheric radio and radar systems. This report develops a model characterizing the plasma density irregularities that produce scintillation in the naturally disturbed equatorial F layer. The model has been incorporated into Program WBMOD along with subroutines for computing both link geometry and scintillation indices, the latter by means of phase screen diffraction theory. The model is based on similarly extensive analysis of Wideband data from two equatorial stations. It describes irregularities at an effective height of 350 km that are isotropic across the geomagnetic field and elongated by a factor of 50 along the field and whose one dimensional spatial power spectrum obeys a single regime power law with a (negative) spectral index of 1.5. The height-integrated spectral strength of the irregularities is modeled as a function of solar epoch (sunspot number), the angle between the sunset terminator and the geomagnetic field line through the equatorial F layer point in question (a measure of seasonal and longitudinal variation), time after E-layer sunset on that field line, and the F-layer magnetic apex latitude of the point. The report also highlights a factor missing from complete characterization of the joint seasonal/longitudinal variation of scintillation, thought to depend upon thermospheric neutral winds.

  7. Global characteristics of the cold plasma in the equatorial plasmapause region as deduced from the GEOS 1 mutual impedance probe

    Microsoft Academic Search

    P. M. E. Décréau; C. Beghin; M. Parrot

    1982-01-01

    Thermal plasma parameters are derived by the mutual impedance experiment on GEOS. The investigation covers the plasmasphere, an intermediate region of ionospheric refilling, and the plasma trough. The intermediate region is always present in the day sector where the ionospheric source plays a leading part, and where the plasma parameters exhibit electron densities of 2 to 20 cu cm and

  8. A Modeling Study of the Latitudinal Variations in the Nighttime Plasma Temperatures of the Equatorial Topside Ionosphere During Northern Winter at Solar Maximum

    NASA Technical Reports Server (NTRS)

    Bailey, G. J.; Denton, M. H.; Heelis, R. A.; Venkatraman, S.

    2000-01-01

    Latitudinal variations in the nighttime plasma temperatures of the equatorial topside ionosphere during northern winter at solar maximum have been examined by using values modelled by SUPIM (Sheffield University Plasmasphere Ionosphere Model) and observations made by the DMSP F10 satellite at 21.00 LT near 800 km altitude. The modelled values confirm that the crests observed near 15 deg latitude in the winter hemisphere are due to adiabatic heating and the troughs observed near the magnetic equator are due to adiabatic cooling as plasma is transported along the magnetic field lines from the summer hemisphere to the winter hemisphere. The modelled values also confirm that the interhemispheric plasma transport needed to produce the required adiabatic heating/cooling can be induced by F-region neutral winds. It is shown that the longitudinal variations in the observed troughs and crests arise mainly from the longitudinal variations in the magnetic meridional wind. At longitudes where the magnetic declination angle is positive the eastward geographic zonal wind combines with the northward (summer hemisphere to winter hemisphere) geographic meridional wind to enhance the northward magnetic meridional wind. This leads to deeper troughs and enhanced crests. At longitudes where the magnetic declination angle is negative the eastward geographic zonal wind opposes the northward geographic meridional wind and the trough depth and crest values are reduced. The characteristic features of the troughs and crests depend, in a complicated manner, on the field-aligned flow of plasma, thermal conduction, and inter-gas heat transfer. At the latitudes of the troughs/crests, the low/high plasma temperatures lead to increased/decreased plasma concentrations.

  9. Correlation analysis between the occurrence of ionospheric scintillation at the magnetic equator and at the southern peak of the Equatorial Ionization Anomaly

    NASA Astrophysics Data System (ADS)

    Lima, G. R. T.; Stephany, S.; Paula, E. R.; Batista, I. S.; Abdu, M. A.; Rezende, L. F. C.; Aquino, M. G. S.; Dutra, A. P. S.

    2014-06-01

    Ionospheric scintillation refers to amplitude and phase fluctuations in radio signals due to electron density irregularities associated to structures named ionospheric plasma bubbles. The phenomenon is more pronounced around the magnetic equator where, after sunset, plasma bubbles of varying sizes and density depletions are generated by plasma instability mechanisms. The bubble depletions are aligned along Earth's magnetic field lines, and they develop vertically upward over the magnetic equator so that their extremities extend in latitude to north and south of the dip equator. Over Brazil, developing bubbles can extend to the southern peak of the Equatorial Ionization Anomaly, where high levels of ionospheric scintillation are common. Scintillation may seriously affect satellite navigation systems, such as the Global Navigation Satellite Systems. However, its effects may be mitigated by using a predictive model derived from a collection of extended databases on scintillation and its associated variables. This work proposes the use of a classification and regression decision tree to perform a study on the correlation between the occurrence of scintillation at the magnetic equator and that at the southern peak of the equatorial anomaly. Due to limited size of the original database, a novel resampling heuristic was applied to generate new training instances from the original ones in order to improve the accuracy of the decision tree. The correlation analysis presented in this work may serve as a starting point for the eventual development of a predictive model suitable for operational use.

  10. Equatorial spread F initiation and growth from satellite traces as revealed from conjugate point observations in Brazil

    NASA Astrophysics Data System (ADS)

    Abdu, M. A.; Kherani, E. A.; Batista, I. S.; Reinisch, B. W.; Sobral, J. H. A.

    2014-01-01

    better understanding of the precursor conditions for the instability growth is very important for identifying the causes of day-to-day variability in the equatorial spread F (ESF)/plasma bubble irregularity development. We investigate here the satellite trace (S-trace) in the ionograms, a precursor to the postsunset ESF occurrence, as observed by Digisondes operated at an equatorial and two magnetic conjugate sites in Brazil during a 66 day observational campaign (Conjugate Point Equatorial Experiment 2002). The satellite traces first occur at the equatorial site, and sequentially, after a variable delay of approximately 20 to 50 min, they are observed nearly simultaneously over the two conjugate sites. The evening prereversal enhancement in the zonal electric field/vertical drift is found to control its development. Using a three-dimensional simulation code based on collisional interchange instability mechanism, it is shown that the observed S-trace occurrence sequence is fully consistent with the instability initiation over the equator with the field-aligned plasma depletion vertical growth marked by latitudinal expansion of its extremities to conjugate locations. The delay in the S-trace occurrence at the conjugate sites (a measure of the nonlinear growth of the instability for plasma depletion) is controlled also by field line parallel (meridional) neutral wind. The relationship between the S-trace and the large-scale wave structure in the F layer, another widely known characterization of the precursor condition for the ESF development, is also clarified.

  11. Vertical neutral wind in the equatorial F-region deduced from electric field and ion density measurements

    NASA Technical Reports Server (NTRS)

    Laakso, Harri; Aggson, Thomas L.; Herrero, F. A.; Pfaff, Robert F.; Hanson, William B.

    1995-01-01

    Direct current (DC) electric field and ion density measurements near density depletion regions (that is, equatorial plasma bubbles) are used to estimate the vertical neutral wind speed. The measured zonal electric field in a series of density depletions crossed by the San Marco D satellite at 01.47-01.52 Universal Time (UT) on 25 October 1988, can be explained if a downward neutral wind of 15-30 m/s exists. Simultaneously, the F-region plasma was moving downward at a speed of 30-50 m/s. These events appear in the local time sector of 23.00-23.15 in which strong downward neutral winds may occur. Indeed, airglow measurements suggest that downward neutral velocities of 25-50 m/s are possible at time near midnight in the equatorial F-region.

  12. Development of a passive VHF radar system using software-defined radio for equatorial plasma instability studies

    NASA Astrophysics Data System (ADS)

    Tuysuz, B.; Urbina, J.; Lind, F. D.

    2013-07-01

    In this paper, a bistatic passive radar receiver system named "Coherent-scatter Atmospheric Passive Radar Imager (CAPRI)" is described. It is primarily designed to study the dynamics of the upper atmosphere by utilizing "transmitters of opportunity" as the RF target illuminators. CAPRI is constructed using the open source software-defined radio toolkit, GNU Radio, to meet the signal processing requirements in combination with the open source hardware, Universal Software Radio Peripheral 2, for data acquisition. The resultant system is highly flexible, and we present the details of the design as well as a performance analysis. CAPRI will be deployed in Peru, near the magnetic equator, for long-term operations in the area. FM stations near Lima, Peru, will be utilized with the targets of interest being the equatorial electrojet and the spread F. The results will then be compared to the Jicamarca Unattended Long-term investigations of the Ionosphere and Atmosphere (JULIA) radar data, and CAPRI will be used to improve the simultaneous time and spatial coverage in the region in a more cost-effective manner.

  13. Bubble Mania

    NSDL National Science Digital Library

    2013-07-30

    In this math lesson, learners practice measurement skills as they examine a soap bubble print. Learners follow a recipe to make a soap bubble solution. They use the soapy solution to blow large bubbles with a plastic drinking straw until the bubbles pop, leaving behind circular prints. Learners find the diameter, circumference, and area of the bubble print.

  14. On the enigma of day-to-day variability in equatorial spread F

    NASA Astrophysics Data System (ADS)

    Tsunoda, Roland T.

    2005-04-01

    We show that large-scale wave structure (LSWS), in plasma density in the bottomside F layer, is a hitherto unheralded contributor to the long-standing enigma of day-to-day variability in equatorial spread F (ESF). Little is known about LSWS; it seems to appear in altitude near a vertical shear in zonal plasma drift, during the post-sunset rise of the F layer, and its growth via an interchange instability appears to predispose quasi-periodically spaced regions to development of plasma bubbles. First indications are that LSWS development is necessary and sufficient for ESF occurrence. We suggest that variability in LSWS development, perhaps together with the shear in zonal drift, may contribute to day-to-day ESF variability. A need revealed by this study is that a cluster of distributed sensors, not isolated ones, is necessary to pursue the problem of day-to-day variability.

  15. Characterizing the 10 November 2004 storm-time middle-latitude plasma bubble event in Southeast Asia using multi-instrument observations

    Microsoft Academic Search

    Guozhu Li; Baiqi Ning; Biqiang Zhao; Libo Liu; Weixing Wan; Feng Ding; J. S. Xu; J. Y. Liu; K. Yumoto

    2009-01-01

    The development and dynamics of ionospheric plasma bubble (PB) irregularity during the super storm of 7–11 November 2004 are investigated using the data from a multi-instrument network operated in Southeast Asia. Analysis of fluctuations in Global Positioning System total electron content (GPS TEC), ionosonde, GPS scintillation, and in situ satellite density data indicates a series of intense PB-associated irregularities at

  16. Equatorial GPS ionospheric scintillations over Kototabang, Indonesia and their relation to atmospheric waves from below

    NASA Astrophysics Data System (ADS)

    Ogawa, Tadahiko; Miyoshi, Yasunobu; Otsuka, Yuichi; Nakamura, Takuji; Shiokawa, Kazuo

    2009-04-01

    Using Global Positioning System (GPS) satellites, we have been conducting equatorial ionospheric scintillation observations at Kototabang, Indonesia since January 2003. Scintillations caused by equatorial plasma bubbles appear between 2000 and 0100 LT in equinoctial months with a seasonal asymmetry, and their activity decreases with decreasing solar activity. A comparison between scintillation index ( S 4) and Earth's brightness temperature ( T bb) variations suggests that the scintillation activity can be related to tropospheric disturbances over the Indian Ocean to the west of Kototabang. To understand better the reasons of day-to-day variability of S 4, we analyze S 4, T bband lower thermospheric neutral wind () data. The results show that S 4 fluctuates with periods of about 2.5, 5, 8, 14 and 25 days, possibly due to atmospheric waves from below and that similar periods are also found in the T bband variations. Using a general circulation model, we made numerical simulations to determine the behavior of neutral wind in the equatorial thermosphere. The results indicate the following: (1) 2- to 20-day waves dissipate rapidly above about an altitude of 125 km, and 0.5- to 3-hour waves become predominant above 100 km, (2) zonal winds above 200 km altitude are, on the whole, eastward during sunset-sunrise, (3) zonal wind patterns due to short-period (1-4 h) atmospheric gravity waves (AGWs) above 120 km altitude change day by day, exhibit wavy structures with scale lengths of about 30-1000 km and, as a whole, move eastward at about 100-1 while changing patterns over time. These simulations suggest that the Rayleigh-Taylor instability responsible for plasma bubble generation can be seeded by AGWs with short periods of about 0.5-3 h, and that background conditions necessary for this instability are modulated by planetary-scale atmospheric waves propagating up to an altitude of about 120 km from below.

  17. Buoyant Bubbles

    NSDL National Science Digital Library

    2012-06-26

    What keeps bubbles and other things, like airplanes, floating or flying in the air? In this activity, learners blow bubbles and wave 3x5 cards above, below and on different sides of the bubbles to keep them afloat as long as possible. The Did You Know section explains the Bernoulli principle: how waving cards above the bubbles helps keep them afloat because faster moving air exerts less pressure to push the bubbles down. The activity can be extended by having learners wave their bubbles through an obstacle course they design themselves.

  18. Soap Bubbles

    NSDL National Science Digital Library

    2011-12-07

    Learners explore three-dimensional geometric frames including cubes and tetrahedrons, as they create bubble wands with pipe cleaners and drinking straws. Then they investigate how soap film flows into a state of minimum energy when they lift the wand up from the bubble solution. Learners also see how light reflection and interference create shimmering colors in the bubbles.

  19. Best Bubbles

    NSDL National Science Digital Library

    Austen Saltz

    2010-01-01

    In this activity, learners experiment with creating various types of bubble solutions and testing which ingredients form longer-lasting bubbles. Learners investigate how surface tension works and the importance of using a surfactant to make bubbles. This activity includes a video about NASA astronaut Don Pettit, who used candy corn to conduct science experiments during his stint aboard the International Space Station.

  20. Recalcitrant bubbles

    PubMed Central

    Shanahan, Martin E. R.; Sefiane, Khellil

    2014-01-01

    We demonstrate that thermocapillary forces may drive bubbles against liquid flow in ‘anomalous' mixtures. Unlike ‘ordinary' liquids, in which bubbles migrate towards higher temperatures, we have observed vapour bubbles migrating towards lower temperatures, therefore against the flow. This unusual behaviour may be explained by the temperature dependence of surface tension of these binary mixtures. Bubbles migrating towards their equilibrium position follow an exponential trend. They finally settle in a stationary position just ‘downstream' of the minimum in surface tension. The exponential trend for bubbles in ‘anomalous' mixtures and the linear trend in pure liquids can be explained by a simple model. For larger bubbles, oscillations were observed. These oscillations can be reasonably explained by including an inertial term in the equation of motion (neglected for smaller bubbles). PMID:24740256

  1. Guided radio-wave propagation in the equatorial ionosphere according to the topside sounding onboard Interkosmos-19

    NASA Astrophysics Data System (ADS)

    Karpachev, A. T.; Zhbankov, G. A.; Kuleshova, V. P.; Telegin, V. A.

    2014-12-01

    In addition to normal vertical-incident ionogram traces, strongly remote (up to 2000 km) traces of HF-radio-signal reflections observed on topside-sounder ionograms of the Interkosmos-19 satellite obtained in the equatorial ionosphere are presented. Such traces are connected with waveguides (ducts). These waveguides are field-aligned irregularities of the ionospheric plasma with electron density depletions of a few percent and cross-field dimension of a few to several kilometers. Ray tracing confirms this supposition and allows an estimate of typical waveguide parameters: diameter ?10-15 km and amplitude |?N/N|?10%, where N is the electron density. The waveguide traces usually start at the cutoff frequencies of the main traces. However, sometimes they begin at much lower frequencies which indicates the satellite was transitioning through an equatorial plasma bubble during the recording of the ionogram. The X-mode of ducted echoes is more distinct then the O-mode. Only one ducted trace is usually observed on the Interkosmos-19 ionograms; a second conjugate trace is rarely recorded. The same is true for combination modes which is a combination of an oblique-incidence and guided propagation. Waveguides are observed at all heights of Interkosmos-19 (500-1000 km) inside the equatorial anomaly region (from -40° to +40° Dip). Waveguides are usually associated with other irregularities of various sizes in the equatorial ionosphere, some of which cause additional traces and spread F on the topside-sounding ionograms. Ducted-echo characteristics observed with Interkosmos-19 are different from those observed earlier with the Alouette and ISIS satellites. This difference is discussed. It is shown that the ionospheric plasma irregularities responsible for the waveguides are observed much more often during nighttime than during daytime.

  2. Dynamics of equatorial spread F using ground-based optical and radar measurements

    NASA Astrophysics Data System (ADS)

    Chapagain, Narayan P.

    The Earth's equatorial ionosphere most often shows the occurrence of large plasma density and velocity fluctuations with a broad range of scale sizes and amplitudes. These night time ionospheric irregularities in the F-region are commonly referred to as equatorial spread F (ESF) or plasma bubbles (EPBs). This dissertation focuses on analysis of ground-based optical and radar measurements to investigate the development and dynamics of ESF, which can significantly disrupt radio communication and GPS navigation systems. OI (630.0 nm) airglow image data were obtained by the Utah State University all-sky CCD camera, primarily during the equinox period, from three different longitudinal sectors under similar solar flux conditions: Christmas Island in the Central Pacific Ocean, Ascension Island in South Atlantic, and Brasilia and Cariri in Brazil. Well-defined magnetic field-aligned depletions were observed from each of these sites enabling detailed measurements of their morphology and dynamics. These data have also been used to investigate day-to-day and longitudinal variations in the evolution and distribution of the plasma bubbles, and their nocturnal zonal drift velocities. In particular, comparative optical measurements at different longitudinal sectors illustrated interesting findings. During the post midnight period, the data from Christmas Island consistently showed nearly constant eastward bubble velocity at a much higher value (˜80 m/s) than expected, while data from Ascension Island exhibited a most unusual shear motion of the bubble structure, up to 55 m/s, on one occasion with westward drift at low latitude and eastward at higher latitudes, evident within the field of view of the camera. In addition, long-term radar observations during 1996-2006 from Jicamarca, Peru have been used to study the climatology of post-sunset ESF irregularities. Results showed that the spread F onset times did not change much with solar flux and that their onset heights increased linearly from solar minimum to solar maximum. On average, radar plume onset occurred earlier with increasing solar flux, and plume onset and peak altitudes increased with solar activity. The F-region upward drift velocities that precede spread F onset increased from solar minimum to solar maximum, and were approximately proportional to the maximum prereversal drift peak velocities.

  3. Equatorial vertical plasma drifts and the measured and IRI model-predicted F 2-layer parameters above Ouagadougou during solar minimum

    NASA Astrophysics Data System (ADS)

    Oyekola, O. S.

    2012-06-01

    In this paper, hourly median value of ionosonde measurements: peak height F 2-layer ( h m F 2), F 2-layer critical frequency ( f o F 2) and propagation factor M(3000) F 2 made at near-equatorial dip latitude, Ouagadougou, Burkina Faso (12°N, 1.5°W; dip: 1.5°N) and relevant F 2-layer parameters: thickness parameter ( B o), electron temperature ( T e), ion temperature ( T i), total electron content (TEC) and electron density ( N e) (at the fixed altitude of 300 km) provided by the International Reference Ionosphere (IRI) model for the longitude of Ouagadougou are contrasted with the IRI vertical drift model to explore in detail the monthly climatological behavior of equatorial ionosphere and the effects of equatorial electrodynamics on the diurnal structure of F 2-layer parameters. The analysis period covers four months representative of solstitial and equinoctial seasonal periods during solar minimum year of 1987 for geomagnetically quiet-day. It is demonstrated that the month-by-month morphological patterns between vertical E × B drifts and F 2-layer parameters range from worst to reasonably good and are largely seasonally dependent. A cross-correlation analysis conducted between equatorial drift and F 2-layer characteristics yield statistically significant correlations for equatorial vertical drift and IRI- B o, IRI- T e and IRI-TEC, whereas little or no acceptable correlation is obtained with observational evidence. Examination of the association between measured f o F 2, h m F 2 and M(3000) F 2 illustrates consistent much more smaller correlation coefficients with no systematic linkage.

  4. Recent results from CHAMP plasma parameter and magnetic field observations

    NASA Astrophysics Data System (ADS)

    Stolle, Claudia; Luehr, Hermann; Park, Jaeheung; Xiong, Chao; Fejer, B. G.

    The multi-year data base of magnetic field and ionospheric measurements from the CHAMP satellite contains an enormous potential to investigate the behaviour and the origin of currents in the F region. Very prominent phenomena are the post-sunset equatorial plasma irregularities (commonly known as "bubbles", or "Equatorial Spread-F" (ESF)) which cause also signatures in the total magnetic field due to diamagnetic currents. The continuous magnetic observations, available at a 1Hz rate, have allowed for the compilation of a comprehensive climatology of the magnetic signatures due to ESF. It reveals a distinct seasonal/longitudinal (S/L) distribution, and the occurrence rate reduces considerably with decreasing solar flux. The (S/L) distribution of bubbles has been found to correlate very well, up to 90 percent, with the pre-reversal enhancement vertical plasma drift peak. This provides strong evidence for the close relation between these phenomena. Since the amplitude of the diamagnetic effect depends on the ambient magnetic field strength and on the background electron density, the global distribution shows also slight differences to the ESF climatology based on plasma depletions. Although electron density readings are only available every 15s, CHAMP data suggest that the plasma irregularities are less structured at places where the ambient magnetic field is strong (e.g. East Asia, Indonesia). In these regions the bubble statistic based on magnetic signatures is systematically lower than that from plasma measurements.

  5. Big Bubbles

    NSDL National Science Digital Library

    2012-06-26

    How do you measure a bubble when it's floating? You can't really, but in this activity, learners can measure the diameter of the ring of suds a bubble leaves on a flat surface. The fun is blowing up the bubbles as big as possible with a straw. Then comes the measuring. This activity can be used to connect science and math, and makes a great rainy day or indoor lunch activity.

  6. Computed optical emissions from a sonoluminescing bubble

    Microsoft Academic Search

    William C. Moss; David A. Young; Judith A. Harte; Joanne L. Levatin; Balazs F. Rozsnyai; George B. Zimmerman; I. Harold Zimmerman

    1999-01-01

    A sonoluminescing bubble has been modeled as a thermally conducting, partially ionized plasma. The model is more complete than previous models, due to the inclusion of both plasma and normal molecular thermal conduction, vapor pressure, surface tension, the mixing of gas and water vapor in the bubble, and opacities. The model accounts for most of the observed experimental trends, including

  7. Specification of the occurrence of equatorial ionospheric scintillations during the main phase of large magnetic storms within solar cycle 23

    NASA Astrophysics Data System (ADS)

    Basu, S.; Basu, Su.; MacKenzie, E.; Bridgwood, C.; Valladares, C. E.; Groves, K. M.; Carrano, C.

    2010-10-01

    Satellite communication and navigation systems operating at low latitudes suffer outages due to ionospheric scintillations during large magnetic storms that are not currently specified by any model. This paper describes and demonstrates how in the framework of an eastward electric field penetration from high to low latitudes at dusk during the main phase of a large storm, for which the rate of change of Dst ? -50 nT/h and the Dst minimum index ? -100 nT, it is possible to specify the longitude interval within the low-latitude ionosphere where scintillations and plasma bubbles are most likely to occur. It is known that the eastward prompt penetration electric field becomes enhanced near sunset due to the day-to-night conductivity gradient. Such enhanced eastward electric fields generally set off the Rayleigh-Taylor plasma instability at F region heights and cause the formation of plasma bubbles and irregularities of electron density that give rise to scintillations of satellite signals. We first discuss two individual magnetic storms that satisfy the criterion of large magnetic storms mentioned above and for which the onsets of the main phase are about 15 h apart. We show that the dusk sectors corresponding to these two storms are such that irregularities and scintillations were observed in the Atlantic-Peruvian longitude sector for one storm and in the Pacific sector for the other. We then present a statistical study with 30 large magnetic storms during solar cycle 23 which satisfy the two criteria of large magnetic storms and we attempt to specify the longitude interval of irregularity and scintillation occurrence during the main phase of such storms. We have tracked globally the occurrence of equatorial scintillations during magnetic storms by the use of scintillation observations made by the Air Force Research Laboratory's Scintillation Network Decision Aid (SCINDA) network and the DMSP satellite in situ measurements of plasma bubbles at 840 km. The statistical study reveals that during large magnetic storms, scintillations and plasma bubbles occur over a specific longitude sector for which the local dusk corresponds to the time interval of the main phase of storms. The magnetic storm induced scintillations may enhance the general seasonal/longitudinal pattern of quiet time scintillations at the station but may also occur where it is least expected in accordance with climatology. The storm time response of the equatorial ionosphere discussed in this paper will be implemented in the SCINDA algorithm to enhance its capability to specify scintillations during large magnetic storms.

  8. Bubble Trouble

    NSDL National Science Digital Library

    2013-07-08

    In this activity on page 15 of the PDF, learners measure the amount of bubbles that they make using a detergent. Learners investigate whether adding Epsom salt to the solution affects its "sudsiness"--an important attribute of soap, since sudsy bubbles help soap clean greasy dirt. Use this activity to explore how chemicals can change a material's properties and how substances dissolve.

  9. Bubble Tray

    NSDL National Science Digital Library

    The Exploratorium

    2012-06-26

    In this activity, learners use simple materials to create giant bubbles. Learners will explore what gives bubbles their shape, what makes them break or last, what causes the colors and patterns in the soap film, and why do they change? Use this activity to introduce the concepts of surface tension and interference.

  10. Bubble, Bubble, Toil and Trouble.

    ERIC Educational Resources Information Center

    Journal of Chemical Education, 2001

    2001-01-01

    Bubbles are a fun way to introduce the concepts of surface tension, intermolecular forces, and the use of surfactants. Presents two activities in which students add chemicals to liquid dishwashing detergent with water in order to create longer lasting bubbles. (ASK)

  11. Guided radio-wave propagation in the equatorial ionosphere according to the Intercosmos-19 and Alouette/ISIS satellites

    NASA Astrophysics Data System (ADS)

    Karpachev, Alexander; Zhbankov, Gennadii; Telegin, Viktor; Kuleshova, Valentina

    In addition to normal vertical-incident ionogram traces, strongly remote (up to 2000 km), traces of HF-radio-signal reflections observed on topside-sounder ionograms of the Interkosmos-19 satellite obtained in the equatorial ionosphere are presented. Such traces are connected with waveguides (ducts). These waveguides are field-aligned irregularities of ionospheric plasma with electron density depletion of a few percent and cross-field dimension of a few to several kilometers. Ray tracing confirms this supposition and allows an estimate of the typical parameters of the waveguides. The waveguide traces usually start at the cutoff frequency of the main trace. However, sometimes they begin at much lower frequencies which indicate the waveguides are located in plasma bubbles. Only one ducted trace is usually observed on the Interkosmos-19 ionograms; a second conjugate trace is rarely recorded. Waveguides are observed at all heights of Interkosmos-19 (500-1000 km) inside the equatorial anomaly region (from -40 to +40 degrees DipLat). Ducted-echo characteristics observed with the Interkosmos-19 are different from those observed earlier with the Alouette and ISIS satellites. This difference is discussed. It is shown that the ionospheric plasma irregularities responsible for the waveguides are observed much more often during nighttime than during daytime.

  12. Controlling bubbles

    NASA Astrophysics Data System (ADS)

    Lohse, Detlef; Prosperetti, Andrea

    2003-01-01

    In this short overview we report on our ongoing work on the dynamics of bubbles in various flows. Three different situations are explored: the competition between acoustic and hydrodynamics forces in a vertical pipe (Rensen J, Bosman D, Magnaudet J, Ohl C D, Prosperetti A, Tögel R, Versluis M and Lohse D 2001 Phys. Rev. Lett. 86 4819), a rising bubble on which shape oscillations have been induced (de Vries J, Luther S and Lohse D 2002 Eur. J. Phys. B 29 503), and a bubble in a rotating horizontal cylinder. Whereas for the first two situations the standard bubble force models (Magnaudet J and Eames I 2000 Annu. Rev. Fluid Mech. 32 659) are consistent with our measurements, modifications for the lift force model seem to be required in the last case.

  13. Cauldron Bubbles

    NSDL National Science Digital Library

    WGBH Boston

    2003-01-01

    In this activity, learners mix up a bubbly brew and examine density. Learners explore how they can make different materials fall and rise in water using oil, water, and salt. Learners can experiment using other materials like sugar and sand.

  14. Response of equatorial, low- and mid-latitude F-region in the American sector during the intense geomagnetic storm on 24-25 October 2011

    NASA Astrophysics Data System (ADS)

    de Jesus, R.; Sahai, Y.; Fagundes, P. R.; de Abreu, A. J.; Brunini, C.; Gende, M.; Bittencourt, J. A.; Abalde, J. R.; Pillat, V. G.

    2013-07-01

    In this paper, we present and discuss the response of the ionospheric F-region in the American sector during the intense geomagnetic storm which occurred on 24-25 October 2011. In this investigation ionospheric sounding data obtained of 23, 24, 25, and 26 October 2011 at Puerto Rico (United States), Jicamarca (Peru), Palmas, São José dos Campos (Brazil), and Port Stanley, are presented. Also, the GPS observations obtained at 12 stations in the equatorial, low-, mid- and high-mid-latitude regions in the American sector are presented. During the fast decrease of Dst (about ˜54 nT/h between 23:00 and 01:00 UT) on the night of 24-25 October (main phase), there is a prompt penetration of electric field of magnetospheric origin resulting an unusual uplifting of the F region at equatorial stations. On the night of 24-25 October 2011 (recovery phase) equatorial, low- and mid-latitude stations show h'F variations much larger than the average variations possibly associated with traveling ionospheric disturbances (TIDs) caused by Joule heating at high latitudes. The foF2 variations at mid-latitude stations and the GPS-VTEC observations at mid- and low-latitude stations show a positive ionospheric storm on the night of 24-25 October, possibly due to changes in the large-scale wind circulation. The foF2 observations at mid-latitude station and the GPS-VTEC observations at mid- and high-mid-latitude stations show a negative ionospheric storm on the night of 24-25 October, probably associated with an increase in the density of molecular nitrogen. During the daytime on 25 October, the variations in foF2 at mid-latitude stations show large negative ionospheric storm, possibly due to changes in the O/N2 ratio. On the night of 24-25, ionospheric plasma bubbles (equatorial irregularities that extended to the low- and mid-latitude regions) are observed at equatorial, low- and mid-latitude stations. Also, on the night of 25-26, ionospheric plasma bubbles are observed at equatorial and low-latitude regions.

  15. Hydrodynamic obstruction to bubble expansion

    SciTech Connect

    Konstandin, Thomas [CERN Physics Department, Theory Division, CH-1211 Geneva 23 (Switzerland); No, José M., E-mail: tkonstan@cern.ch, E-mail: jose-miguel.no@cea.fr [Institut de Physique Théorique, CEA/Saclay, F-91191 Gif-sur-Yvette Cédex (France)

    2011-02-01

    We discuss a hydrodynamic obstruction to bubble wall acceleration during a cosmological first-order phase transition. The obstruction results from the heating of the plasma in the compression wave in front of the phase transition boundary. We provide a simple criterion for the occurrence of the obstruction at subsonic bubble wall velocity in terms of the critical temperature, the phase transition temperature, and the latent heat of the model under consideration. The criterion serves as a sufficient condition of subsonic bubble wall velocities as required by electroweak baryogenesis.

  16. Modeling the Direct Penetration of Electric Fields to the Equatorial Ionosphere

    NASA Astrophysics Data System (ADS)

    Rothwell, P. L.; Jasperse, J. R.; Burke, W. J.; Grossbard, N. J.; Huang, C.

    2004-05-01

    The interplanetary electric field has been observed to penetrate directly to the equatorial region where it affects the generation of plasma bubbles which, in turn, cause the scintillation of transionospheric electromagnetic signals. We use the approach of Nopper and Caravillano [1978] to model the effect of the Region I and Region II currents on the global electric field. We find, consistent with observations, the well-known shielding of the equatorial region by Region II currents. Numerically, two approaches are taken. The first approach is to solve N-squared simultaneous linear algebraic equations for each of the grid points. The second approach is to use the Multigrid technique, which allows a rapid convergence of the SOR (successive over- relaxation) iterations. The advantage of the algebraic approach is accuracy, while the advantage of the second approach is speed. Further comparisons between these two approaches will be made. Effects of the magnetic dipole tilt relative to the polar cap, the presence of a sub storm current wedge, the saturation of the transpolar potential, and seasonal effects will be discussed . Nopper R.W. and R. L. Carovillano, Geophys. Res. Ltrs., 5, 699, 1978.

  17. Bubble diagnostics

    DOEpatents

    Visuri, Steven R. (Livermore, CA); Mammini, Beth M. (Walnut Creek, CA); Da Silva, Luiz B. (Danville, CA); Celliers, Peter M. (Berkeley, CA)

    2003-01-01

    The present invention is intended as a means of diagnosing the presence of a gas bubble and incorporating the information into a feedback system for opto-acoustic thrombolysis. In opto-acoustic thrombolysis, pulsed laser radiation at ultrasonic frequencies is delivered intraluminally down an optical fiber and directed toward a thrombus or otherwise occluded vessel. Dissolution of the occlusion is therefore mediated through ultrasonic action of propagating pressure or shock waves. A vapor bubble in the fluid surrounding the occlusion may form as a result of laser irradiation. This vapor bubble may be used to directly disrupt the occlusion or as a means of producing a pressure wave. It is desirable to detect the formation and follow the lifetime of the vapor bubble. Knowledge of the bubble formation and lifetime yields critical information as to the maximum size of the bubble, density of the absorbed radiation, and properties of the absorbing material. This information can then be used in a feedback system to alter the irradiation conditions.

  18. Height dependence of spread F bubble drift velocities

    NASA Technical Reports Server (NTRS)

    Hudson, M. K.; Balsley, B. B.

    1979-01-01

    Vertical bubble velocities in equatorial spread F have been investigated analytically by Ott (1978), Osakow and Chaturvedi (1978), all of whom found a proportionality of the vertical velocity to bubble depletion density. The paper presents radar data from two equatorial sites which support theoretical predictions that vertical drift velocities of spread F bubbles increase with height on the bottomside of the F layer. This increase is shown to result from the proportionality of bubble drift velocity to density depletion amplitude, which itself increases with height. The measured rate of increase is found to be dU/dh equals about 2 m/s km. It is concluded that this is consistent with numerical simulation results within a factor of 2.

  19. Pump-probe imaging of nanosecond laser-induced bubbles in distilled water solutions: Observations of laser-produced-plasma

    NASA Astrophysics Data System (ADS)

    Evans, R.; Camacho-López, S.

    2010-11-01

    This article presents the analysis of the laser-produced-plasma (LPP) formed by the focusing of a 9 ns laser pulse, ? =532 nm, with a NA=0.6 aspherical lens using energies between 100-1500 ?J, into distilled water with varying solutions of table salt. Observations of the filamentation plasma were made, which are explained by self-focusing of the laser pulse by the LPP through ponderomotive cavitation of the electron plasma in the center of the beam. The filamentation of the beam through a low density plasma wave guide explains why the transmission of the pump laser through the interaction region was notably higher on previous experiments that we performed [R. Evans et al., Opt. Express 16, 7481 (2008)], than a very similar set of experiments performed by Noack and Vogel [IEEE J. Quantum Electron. 35, 1156 (1999)].

  20. Tiny Bubbles

    NSDL National Science Digital Library

    Glenn Dolphin

    In this activity, which can be performed as a demonstration by the teacher or by the students themselves, carbon dioxide is generated in a fish tank using sodium bicarbonate and vinegar. The students can observe as the accumulating carbon dioxide extinguishes candles of different heights, marking rising levels of CO2 in the tank. They can also blow soap bubbles (which contain air) into the tank and observe them floating on the denser CO2 at first, then sinking as the gas diffuses through the soap film that forms the bubbles.

  1. Mercury Bubbles

    Microsoft Academic Search

    A. T. Hare

    1908-01-01

    I HAVE on several occasions noticed the beautiful bubbles described by Mr. Wright and Sir William Crookes (pp. 8 and 37). On each occasion I was purifying mercury in the following way. I half filled a rather large Woulffe's bottle with mercury and poured on to it weak nitric acid. Then, in order to keep, the whole in a state

  2. Tiny Bubbles.

    ERIC Educational Resources Information Center

    Kim, Hy

    1985-01-01

    A simple oxygen-collecting device (easily constructed from glass jars and a lid) can show bubbles released by water plants during photosynthesis. Suggestions are given for: (1) testing the collected gas; (2) using various carbon dioxide sources; and (3) measuring respiration. (DH)

  3. Equatorial Electrojet Observations in the African Continent

    NASA Astrophysics Data System (ADS)

    Yizengaw, E.; Moldwin, M. B.; Mebrahtu, A.; Damtie, B.; Pfaff, R.; Zesta, E.

    2008-12-01

    Although Satellite observations in the African sector show unique equatorial ionospheric structures that can severely impact navigation and communication systems, the study of ionospheric disturbances in this region is difficult due to the lack of ground-based instruments. This has created a gap in global understanding of the physics behind the evolution and formation of plasma irregularities in the equatorial region, which imposes limitations on ionospheric density modeling efforts. Therefore, in order to have a more complete global understanding of equatorial ionosphere motion, the international space science community has begun to develop an observational infrastructure in the African sector. This includes the deployment of a number of arrays of small instruments, including the AMBER magnetometer array, through the International Heliophysical Year (IHY) cooperative program with the United Nations Basic Space Science (UNBSS) program. Two AMBER magnetometers have been deployed successfully at Adigrat (~6°N magnetic) in Ethiopia and at Medea in Algeria (28°N magnetic), and became fully operational on 03 August 2008. The remaining two AMBER magnetometers will be deployed soon in Cameroon and Namibia. One of the prime scientific objectives of AMBER is to understand the processes governing electrodynamics of the equatorial ionosphere as a function of latitude, local time, magnetic activity, and season in the African region. The most credible driving mechanism of ionospheric plasma (E × B drift) can be estimated using two magnetometers, one right at the equator and the other about 6 off the equator. Therefore, using the AMBER magnetometer at Adigrat and the INTERMAGNET magnetometer located at Addis Ababa (0.9°N magnetic) in Ethiopia, the equatorial electrojet (E × B drift) activities in that longitudinal sector of the African continent is estimated. The paper also presents the comparison between the estimated vertical drift and the drift values obtained from the vector electric field instrument observation onboard the C/NOFS satellite. The evolution of equatorial ionospheric irregularities will also be presented using data from the growing number of ground- and space-based (on Low-Earth-Orbit (LEO) satellites) GPS receivers in the African region.

  4. Magnetic Dipole Inflation with Cascaded ARC and Applications to Mini-Magnetospheric Plasma Propulsion

    NASA Technical Reports Server (NTRS)

    Giersch, L.; Winglee, R.; Slough, J.; Ziemba, T.; Euripides, P.

    2003-01-01

    Mini-Magnetospheric Plasma Propulsion (M2P2) seeks to create a plasma-inflated magnetic bubble capable of intercepting significant thrust from the solar wind for the purposes of high speed, high efficiency spacecraft propulsion. Previous laboratory experiments into the M2P2 concept have primarily used helicon plasma sources to inflate the dipole magnetic field. The work presented here uses an alternative plasma source, the cascaded arc, in a geometry similar to that used in previous helicon experiments. Time resolved measurements of the equatorial plasma density have been conducted and the results are discussed. The equatorial plasma density transitions from an initially asymmetric configuration early in the shot to a quasisymmetric configuration during plasma production, and then returns to an asymmetric configuration when the source is shut off. The exact reasons for these changes in configuration are unknown, but convection of the loaded flux tube is suspected. The diffusion time was found to be an order of magnitude longer than the Bohm diffusion time for the period of time after the plasma source was shut off. The data collected indicate the plasma has an electron temperature of approximately 11 eV, an order of magnitude hotter than plasmas generated by cascaded arcs operating under different conditions. In addition, indirect evidence suggests that the plasma has a beta of order unity in the source region.

  5. Equatorial oceanography. [review of research

    NASA Technical Reports Server (NTRS)

    Cane, M. A.; Sarachik, E. S.

    1983-01-01

    United States progress in equatorial oceanography is reviewed, focusing on the low frequency response of upper equatorial oceans to forcing by the wind. Variations of thermocline depth, midocean currents, and boundary currents are discussed. The factors which determine sea surface temperature (SST) variability in equatorial oceans are reviewed, and the status of understanding of the most spectacular manifestation of SST variability, the El Nino-Southern Oscillation phenomenon, is discussed. The problem of observing surface winds, regarded as a fundamental factor limiting understanding of the equatorial oceans, is addressed. Finally, an attempt is made to identify those current trends which are expected to bear fruit in the near and distant future.

  6. Jupiter Equatorial Region

    NASA Technical Reports Server (NTRS)

    1997-01-01

    This photographic mosaic of images from NASA's Galileo spacecraft covers an area of 34,000 kilometers by 22,000 kilometers (about 21,100 by 13,600 miles) in Jupiter's equatorial region. The dark region near the center of the mosaic is an equatorial 'hotspot' similar to the site where the Galileo Probe parachuted into Jupiter's atmosphere in December 1995. These features are holes in the bright, reflective, equatorial cloud layer where heat from Jupiter's deep atmosphere can pass through. The circulation patterns observed here along with the composition measurements from the Galileo Probe suggest that dry air may be converging and sinking over these regions, maintaining their cloud-free appearance. The bright oval in the upper right of the mosaic as well as the other smaller bright features are examples of upwelling of moist air and condensation. These images were taken on December 17, 1996, at a range of 1.5 million kilometers (about 930,000 miles) by the Solid State Imaging camera system aboard Galileo.

    North is at the top. The mosaic covers latitudes 1 to 19 degrees and is centered at longitude 336 degrees west. The smallest resolved features are tens of kilometers in size.

    The Jet Propulsion Laboratory, Pasadena, CA manages the mission for NASA's Office of Space Science, Washington, DC.

    This image and other images and data received from Galileo are posted on the World Wide Web, on the Galileo mission home page at: http://galileo.jpl.nasa.gov. Background information and educational context for the images can be found at: http:/ /www.jpl.nasa.gov/galileo/sepo.

  7. Equatorial spread F statistics and empirical representation for IRI: A regional model for the Brazilian longitude sector

    NASA Astrophysics Data System (ADS)

    Abdu, M. A.; Souza, J. R.; Batista, I. S.; Sobral, J. H. A.

    The empirical representation of the equatorial spread F (ESF) statistics in the IRI scheme requires well established distribution statistics of ESF occurrence and intensity as a function of local time, season/month, latitude and solar and magnetic activity levels. We present here a regional model for the quiet-time spread F distribution in the Brazilian longitude sector. In view of the well known dependence of spread F occurrence on magnetic declination angle, and the fact that the declination angle varies rapidly from the west coast (Peruvian sector) to the east coast (Brazilian sector) of south America the present model can be said to be valid for the latter sector. 13 years of spread F data simultaneously collected (during 1978-1990) over the equatorial site Fortaleza and low latitude site Cachoeira Paulista are used in this model. Only spread F data that is believed to be related to plasma bubble developments is used in the model. The data were first grouped into solar flux range bins representing low, medium, and high solar activity levels, represented, respectively, by F10.7 ? 100; 100 < F10.7 < 180; and F10.7 ? 180. Spread F percentage occurrence as a function of (nocturnal) local time for each of the 12 months in each solar flux range was calculated, and form the database for the model. Cubic-B spline fits of the data in local time, latitude, season/month and solar flux nodes constitute the structure of the present model. The model confirms many characteristic features of the spread F statistics already known as well as brings out some new outstanding features for the Brazilian sector. Among the results to be highlighted are: The spread F onset and peak occurrence get delayed in local time with increasing distance from the equator, indicating the plasma bubble origin for the low latitude ionogram spread F traces; The plasma bubble occurrence as well as the vertical rise velocity increase with the increase in solar flux; They attain larger values in summer months (centered around December) than in equinoctial months (March and September). The latitudinal variation in spread F, though based only on two-station data sets in this study, looks compatible with the latitude variation of ion density fluctuations observed by the AE-E satellite. The model will be made available to interested users.

  8. Discrete Bubble Modeling for Cavitation Bubbles

    NASA Astrophysics Data System (ADS)

    Choi, Jin-Keun; Chahine, Georges; Hsiao, Chao-Tsung

    2007-03-01

    Dynaflow, Inc. has conducted extensive studies on non-spherical bubble dynamics and interactions with solid and free boundaries, vortical flow structures, and other bubbles. From these studies, emerged a simplified Surface Averaged Pressure (SAP) spherical bubble dynamics model and a Lagrangian bubble tracking scheme. In this SAP scheme, the pressure and velocity of the surrounding flow field are averaged on the bubble surface, and then used for the bubble motion and volume dynamics calculations. This model is implemented using the Fluent User Defined Function (UDF) as Discrete Bubble Model (DBM). The Bubble dynamics portion can be solved using an incompressible liquid modified Rayleigh-Plesset equation or a compressible liquid modified Gilmore equation. The Discrete Bubble Model is a very suitable tool for the studies on cavitation inception of foils and turbo machinery, bubble nuclei effects, noise from the bubbles, and can be used in many practical problems in industrial and naval applications associated with flows in pipes, jets, pumps, propellers, ships, and the ocean. Applications to propeller cavitation, wake signatures of waterjet propelled ships, bubble-wake interactions, modeling of cavitating jets, and bubble entrainments around a ship will be presented.

  9. On the Geometrical Aspects of GPS Scintillations during the Conjugate Point Equatorial Experiment (copex) Campaign in Brazil

    NASA Astrophysics Data System (ADS)

    Carrano, C. S.; Valladares, C. E.; Groves, K.

    2011-12-01

    We examine the geometrical aspects of GPS scintillations at three locations in Brazil during the Oct-Dec 2002 Conjugate Point Equatorial Experiment (COPEX): Boa Vista (2.85N, 60.70°W, dip 12.60°N); Alta Floresta (9.87°S, 56.1°W, dip 0.75°S); and Campo Grande (20.47°S, 54.66°W, dip 10.77°S). Previous authors [Muella et al., 2008; de Paula et al., 2010] have established the association between the GPS scintillations during the campaign and equatorial plasma bubbles generated by plasma interchange instabilities after sunset. Our aim is to demonstrate the effect of satellite motion and the direction of signal propagation with respect to the magnetic field on the depth and rate of signal fading, both of which affect the probability of scintillation-induced loss of lock on the GPS signals and degrade GPS positioning accuracy [Humphreys et al., 2010; Carrano et al., 2010]. We report on the behavior of the scintillation intensity index (S4) and the intensity decorrelation time (?) as a function of dip latitude, local time, and the speed and direction at which the line of sight scans through the drifting plasma irregularities. We remove the geometrical effects using weak scatter diffraction theory to estimate the turbulent intensity and spatial decorrelation length in the magnetic west-east direction. From these parameters, it is possible to infer the depth and rate of signal fading for any propagation geometry in the region, a capability which is needed for modeling GPS scintillation impacts on GPS positioning accuracy.

  10. Ventilation of the equatorial Atlantic

    NASA Astrophysics Data System (ADS)

    Brandt, Peter; Greatbatch, Richard J.; Claus, Martin; Didwischus, Sven-Helge; Hahn, Johannes

    2013-04-01

    The equatorial oxygen maximum at intermediate depth (300m-700m) is a characteristic feature of the observed water mass distribution of the tropical Atlantic, but it is not well reproduced in biogeochemical models. Here we analyze long-term moored velocity and oxygen observations as well as shipboard hydrographic and current sections acquired along 23°W, which cover the depth range of the oxygen minimum zones of the eastern tropical North and South Atlantic. The mean flow field from shipboard observations shows the presence of the equatorial intermediate current system (EICS) with strongest eastward flow at 2°N/S and westward flow in between. The moored zonal velocity data show high-baroclinic mode equatorial deep jet (EDJ) oscillations at a period of about 4.5 years. Equatorial oxygen observations which do not resolve or cover a full 4.5-yr EDJ cycle nevertheless reveal large variability, with oxygen concentrations locally spanning a range of more than 60 ?mol/kg. We study the effect of the EICS and EDJs on the equatorial oxygen concentration by forcing an advection-diffusion model with the velocity field of the gravest equatorial basin mode corresponding to the observed EDJ cycle superimposed on the mean EICS. The advection-diffusion model includes an oxygen source at the western boundary and oxygen consumption elsewhere. The respective role of mean advection, EDJs, and other possible processes in shaping the mean oxygen distribution of the equatorial Atlantic at intermediate depth is discussed.

  11. Traveling planetary wave ionospheric disturbances and their role in the generation of equatorial spread-F and GPS phase fluctuations during the last extreme low solar activity and comparison with high solar activity

    NASA Astrophysics Data System (ADS)

    de Abreu, A. J.; Fagundes, P. R.; Bolzan, M. J. A.; Gende, M.; Brunini, C.; de Jesus, R.; Pillat, V. G.; Abalde, J. R.; Lima, W. L. C.

    2014-09-01

    This investigation studies traveling planetary wave ionospheric disturbance (TPWID) type oscillations on the modulation of the F region virtual height rise during the E×B electric field pre-reversal enhancement (PRE), near sunset hours. We also studied their role in the generation of equatorial spread F (ESF) and GPS phase fluctuations during periods of the last extreme low solar activity (LSA) of January 2009 to April 2010 (F10.7bar=73). A comparison is made with periods of high solar activity (HSA) in 2003 and 2004 near equatorial region. The ionospheric irregularities investigated are medium (bottom-side) and large (plasma bubble) scales. Ionospheric F region oscillations with period of days are due to the TPWIDs, which play an important role in producing favorable or unfavorable conditions for equatorial ionospheric irregularities, changing the electron vertical profile and F region height. In this paper, we present simultaneous ionospheric sounding (ionosonde) and GPS vertical total electron content (vTEC) observations carried out near equatorial region (Palmas 10.2°S, 48.2°W) and low latitude region (São José dos Campos 23.2°S, 45.9°W; located under the southern crest of the equatorial ionospheric anomaly), Brazil. Observations show that the occurrence of fresh ESF during LSA and HSA and fresh GPS phase fluctuations at equatorial region follow the trend of day-to-day variations in the F region virtual height, which are due to electric field PRE modulated by TPWID wave like oscillations. During LSA, the altitude of 250 km acts as a threshold height for the generation of fresh ionospheric irregularities, whereas during HSA, the threshold height is 300 km. The observations also found a strong increase in the generation of fresh ionospheric irregularities from October 2009 to March 2010 during LSA and from September 2003 to March 2004 during the HSA. Furthermore, in LSA, the period of fresh ionospheric irregularities was less than during HSA, though both periods followed a similar seasonal pattern. In the low-latitude, we observed more ESFs than phase fluctuations because ionosonde is more sensitive than GPS. We also observed periods with and without day-to-day oscillations in the F region virtual height. The observations made by GPS stations and ionosondes in the equatorial region, for much of the period analyzed, presented similar results with regard to the generation of equatorial ionospheric irregularities. In the low latitude, some nights of January, February, October, and December 2009 also showed a similarity.

  12. Shock-wave propagation in a sonoluminescing gas bubble

    NASA Technical Reports Server (NTRS)

    Wu, C. C.; Roberts, Paul H.

    1993-01-01

    The motion of the bubble radius and of the air trapped inside the bubble during sonoluminescence are determined self-consistently by coupling the solution of the Rayleigh-Plesset equation governing the bubble radius to the solution of Euler's equations for the motion of air in the bubble. Results are presented for three slightly different conditions of excitation, in two of which shocks are formed during the collapse of the bubble, and in which such high temperatures are attained that the air is ionized. Estimates are made of the duration and intensity of the light then radiated by the plasma.

  13. Diagnosing temperature change inside sonoluminescing bubbles by calculating line spectra.

    PubMed

    An, Yu; Li, Chaohui

    2009-10-01

    With the numerical calculation of the spectrum of single bubble sonoluminescence, we find that when the maximum temperature inside a dimly luminescing bubble is relatively low, the spectral lines are prominent. As the maximum temperature of the bubble increases, the line spectrum from the bright bubble weakens or even fades away relative to the background continuum. The calculations in this paper effectively interpret the observed phenomena, indicating that the calculated results, which are closely related to the spectrum profile, such as temperature and pressure, should be reliable. The present calculation tends to negate the existence of a hot plasma core inside a sonoluminescing bubble. PMID:19905449

  14. The Colorado Equatorial Sundial

    NASA Astrophysics Data System (ADS)

    Garstang, R. H.

    1996-05-01

    The University of Colorado received from Mr. and Mrs. J. H. Tippit in 1995 a large equatorial sundial in memory of one of their sons, John Garrey Tippit, who graduated from the University of Colorado and was killed in a construction accident in 1969. The sundial is installed in the quadrangle in front of our main Norlin Library. The sundial is made of a large slab of Colorado rose-red granite, mined a few miles from Boulder. It is approximately 185 cm in diameter and 16 cm thick. The gnomon is a steel rod 7.6 cm in diameter and 205 cm in total length. The total mass, estimated from the average densities of granite and steel, is about 1400 kg, and this large mass made it impossible to make slight adjustments to the setup after installation. The sundial carries the motto "Knowledge and time abide in the same place". The sundial can be read to an accuracy of about one minute. We are making a large number of checks of the time; after allowing for the longitude and the equation of time the residuals are up to about three minutes, depending on whether one is using the winter or summer side and on whether it is morning or afternoon. We intend to analyze the errors after we have made checks for about a year.

  15. Global characterization of the equatorial ionospheric anomaly with data from the global ultraviolet imager

    NASA Astrophysics Data System (ADS)

    Henderson, Sidney B., II

    The Equatorial Anomaly (EA) is host to the highest ionospheric densities in the Earth's atmosphere. Disturbances within the EA result in plasma density depletions and large density gradients. In this dissertation we present a method for measuring EA morphology using nighttime 135.6 nm radiance observed by the Global Ultraviolet Imager (GUVI) on-board the Thermosphere Ionosphere Mesosphere Energetics and Dynamics (TIMED) spacecraft. The method uses the singular value decomposition to estimate an along-track intensity profile as TIMED passes over the EA. The method is unique in that it removes intensity depletions due to equatorial plasma bubbles (EPBs) from the estimated intensity profile. Thus, the profiles reflect plasma distribution in response to equatorial E x B drifts and neutral winds. A set of metrics including crest maximum intensity (CM) and crest latitude (CL) is extracted from the intensity profiles. EPBs are also detected. By using these metrics, extensive observations of EA and EPB morphology show that EA morphology can be well characterized by data taken from the 2030-2130 MLT range. Further, this dissertation identifies crest symmetry in intensity and latitude as an indicator of both EA and EPB morphology. For all longitudes, the crest-to-trough ratio (CTR) is shown to be well correlated with the EPB rate. While the CTR may drop with solar flux, EPB levels do not. Thus, the absolute CTR, is less an indicator than the change in the CTR, as a function of longitude for a given season and solar flux. One significant exception to this correlation is observed in the Pacific sector during the June solstice. In this case the EPB rate is high despite a low CTR. In order to estimate global EA morphology for all night local times, the data, are used to train empirical models of the CMS and CLS. Our results indicate that EA enhancement is well correlated with F10.7 cm solar flux, especially during equinox. In terms of seasonal dependence we find that at equinox, north and south crest latitude symmetry occurs before 2300 MLT except in the African-Indian sector where CSL?CNL . Before 2300 MIT during the June solstice, CNM?CSM andCNL?C SL while the reverse is true during the December solstice. We also study the driver-response relationship between the equatorial zonal electric field and the EA. This is done by comparing the vertical plasma drift velocity as predicted by the Scherliess and Fejer empirical model with our EA crest models. Comparing the maximum CM (MaxCM) and maximum CL (MaxCL) observed in a crest with the maximum vertical drift of the prereversal enhancement (MaxVD), we find that the equinox EA response time as a function of longitude is 2.5 to 5 hours in the north crest and 2 to 3.25 hours in the south crest. During the solstices minimum response times were observed at under 1 hour. The magnitude of MaxCM is coarsely correlated with MaxVD. During equinox MaxCL is well correlated with MaxVD.

  16. Calculated pulse widths and spectra of a single sonoluminescing bubble

    SciTech Connect

    Moss, W.C.; Clarke, D.B.; Young, D.A. [Lawrence Livermore National Lab., CA (United States)] [Lawrence Livermore National Lab., CA (United States)

    1997-05-30

    A sonoluminescing bubble has been modeled as a thermally conducting, partially ionized, two-component plasma. The model shows that the measured picosecond pulse widths are due to electron conduction and the rapidly changing opacity of the plasma and that these mechanisms are also responsible for the absence of an {open_quotes}afterglow{close_quotes} subsequent to the sonoluminescence flash while the hot bubble expands and cools. The calculated spectra for sonoluminescing nitrogen and argon bubbles suggest that a sonoluminescing air bubble probably contains only argon, in agreement with a recent theoretical analysis. 27 refs., 3 figs.

  17. Characterization of transverse beam emittance of electrons from a laser-plasma wakefield accelerator in the bubble regime using betatron x-ray radiation

    NASA Astrophysics Data System (ADS)

    Kneip, S.; McGuffey, C.; Martins, J. L.; Bloom, M. S.; Chvykov, V.; Dollar, F.; Fonseca, R.; Jolly, S.; Kalintchenko, G.; Krushelnick, K.; Maksimchuk, A.; Mangles, S. P. D.; Najmudin, Z.; Palmer, C. A. J.; Phuoc, K. Ta; Schumaker, W.; Silva, L. O.; Vieira, J.; Yanovsky, V.; Thomas, A. G. R.

    2012-02-01

    We propose and use a technique to measure the transverse emittance of a laser-wakefield accelerated beam of relativistic electrons. The technique is based on the simultaneous measurements of the electron beam divergence given by v?/v?, the measured spectrum ?, and the transverse electron bunch size in the bubble r?. The latter is obtained via the measurement of the source size of the x rays emitted by the accelerating electron bunch in the bubble. We measure a normalized rms beam transverse emittance <0.5?mmmrad as an upper limit for a spatially Gaussian, spectrally quasimonoenergetic electron beam with 230 MeV energy in agreement with numerical modeling and analytic theory in the bubble regime.

  18. Study of Sun-Earth interactions using equatorial VHF scintillation in the Indian region

    NASA Astrophysics Data System (ADS)

    Banola, Sridhar

    Plasma density irregularities in the ionosphere (associated with ESF, plasma bubbles and Spo-radic E layers) cause scintillations in various frequency ranges. VHF radio wave scintillation technique is extensively used to study plasma density irregularities of sub-kilometre size . Ef-fects of magnetic and solar activity on ionospheric irregularities are studied so as to ascertain their role in the space weather of the near earth environment in space. Indian Institute of Ge-omagnetism operated a ground network of 13 stations monitoring amplitude scintillations on 244/251 MHz (FLEETSAT 73° E) signals in placecountry-regionIndia for more than a decade under AICPITS. At present VHF scintillation is being recorded at Mumbai by monitoring 251 MHz signal transmitted by geostationary satellite UFO2(71.2 E). sampling at 20 Hz. During CAWSES campaign (March-April 2006, low sunspot period) occurrence of daytime scintilla-tions was observed higher than the nighttime scintillations. This could be due to the fact that during low sunspot years occurrence of spread-F is limited to a narrow latitude region near the dip equator. To study solar cycle association of scintillations, long series of simultaneous amplitude scintillation data for period Jan 1989 to Dec 2000 at Indian low-latitude stations Tirunelveli/Trivandrum, close to dip equator, Pondicherry/Karur, located at the fringe of elec-trojet, Mumbai (dip lat. 13.5o N), a temperate station and Ujjain (dip lat. 18.6o N), close to anomaly crest region are utilized. Nighttime scintillation occurrence is solar activity dependent. Equatorial scintillations are inhibited with increase in geomagnetic activity.

  19. Studies on equatorial shock formation during plasmaspheric refilling

    NASA Technical Reports Server (NTRS)

    Singh, N.

    1994-01-01

    Investigations based on small-scale simulations of microprocesses occurring when a magnetic flux tube refills with a cold plasma are summarized. Results of these investigations are reported in the following attached papers: (1) 'Numerical Simulation of Filling a Magnetic Flux Tube with a Cold Plasma: The Role of Ion Beam-Driven Instabilities'; and (2) 'Numerical Simulation of Filling a Magnetic Flux Tube with a Cold Plasma: Effects of Magnetically Trapped Hot Plasma'. Other papers included are: 'Interaction of Field-Aligned Cold Plasma Flows with an Equatorially-Trapped Hot Plasma: Electrostatic Shock Formation'; and 'Comparison of Hydrodynamic and Semikinetic Treatments for a Plasma Flow along Closed Field Lines'. A proposal for further research is included.

  20. The streaming-trapped ion interface in the equatorial inner magnetosphere

    NASA Technical Reports Server (NTRS)

    Lin, J.; Horwitz, J. L.; Gallagher, D.; Pollock, C. J.

    1994-01-01

    Spacecraft measurements of core ions on L=4-7 field-lines typically show trapped ion distributions near the magnetic equator, and frequently indicate field-aligned ion streams at higher latitudes. The nature of the transition between them may indicate both the microphysics of hot-cold plasma interactions and overall consequences for core plasma evolution. We have undertaken a statistical analysis and characterization of this interface and its relation to the equatorial region of the inner magnetosphere. In this analysis, we have characterized such features as the equatorial ion flux anisotropy, the penetration of field-aligned ionospheric streams into the equatorial region, the scale of the transition into trapped ion populations, and the transition latitude. We found that most transition latitudes occur within 13 deg of the equator. The typical values of equatorial ion anisotropies are consistent with bi-Maxwellian temperature ratios of T(sub perpendicular)/T(sub parallel) in the range of 3-5. The latitudinal scales for the edges of the trapped ion populations display a rather strong peak in the 2-3 deg range. We also found that there is a trend for the penetration ratio, the anisotropy half width, and the transition scale length to decrease with a higher equatorial ion anisotropy. We may interpret these features in terms of Liouville mapping of equatorially trapped ions and the reflection of the incoming ionospheric ion streams from the equatorial potential peaks associated with such trapped ions.

  1. Solar Wind Effects on Plasma Density Depletions: C/NOFS Results with Related Observations from DMSP

    NASA Astrophysics Data System (ADS)

    Burke, W. J.; Gentile, L. C.; Roddy, P. A.; Retterer, J. M.; Wilson, G. R.; de La Beaujardiere, O.; Su, Y.

    2010-12-01

    Before C/NOFS, the prevailing wisdom was that equatorial plasma bubbles (EPBs) were primarily a post-sunset phenomenon. Changes in the ionosphere after sunset create conditions favorable for instability formation as polarization electric fields increase near the terminator. Plasma irregularities that develop in the bottomside of the F-layer grow into large depletions that rise rapidly into the topside ionosphere. By two hours in local time after sunset the initial upward drift of the ionosphere reverses suppressing further development of instabilities. Tsunoda’s [1985] seasonal-longitudinal model predicted that EPB rates should peak near times when the equatorial declination and the dusk terminator are closely aligned. Under these conditions E-layer conductance vanishes at both ends of flux tubes simultaneously, allowing EPBs to grow most rapidly. We validated this model during the recent solar maximum. In this unusual solar minimum, however, C/NOFS has encountered very few post-sunset depletions. They commonly appear between local midnight and dawn. We trace the energy flow from the Sun to the Earth to demonstrate that C/NOFS measurements are providing key insights into the dynamics of the Ionosphere-Thermosphere system. Results suggest that systematic effects of solar wind / IMF on dynamics of equatorial plasmas and electric fields may allow long-term alerts about impending ionospheric disturbances that lead to scintillation activity. Reference: Tsunoda, R. T. (1985), J. Geophys. Res., 90, 447.

  2. Digital ionosonde observations during equatorial spread F-italic

    Microsoft Academic Search

    P. E. Argo; M. C. Kelley

    1986-01-01

    In this paper we present and discuss equatorial spread F-italic data taken with a digital ionosonde\\/HF radar located at Huancayo, Peru. A modified phenomenology is developed which uses the system's ability to do echo location. The onset of irregularities is seen to occur in the east and to move westward, while inside this large-scale structure the plasma is found to

  3. Micro-domains of AQP0 in Lens Equatorial Fibers

    Microsoft Academic Search

    Guido A. Zampighi; Sepehr Eskandari; James E. Hall; Lorenzo Zampighi; Michael Kreman

    2002-01-01

    To understand why the water channel aquaporin-0 (AQP0) replaces aquaporin-1(AQP1) during lens development, we studied its spatial arrangement and interactions with proteins in the plasma membrane of equatorial fibers. We used freeze-fracture-labelling; a method that can identify the individual intramembrane particle representing the AQP0 channel. We found that AQP0 was arranged in micro-domains that extended along the long axis of

  4. Bubble Manipulation by Self Organization of Bubbles inside Ultrasonic Wave

    NASA Astrophysics Data System (ADS)

    Yamakoshi, Yoshiki; Koganezawa, Masato

    2005-06-01

    Microbubble manipulation using ultrasonic waves is a promising technology in the fields of future medicine and biotechnology. For example, it is considered that bubble trapping using ultrasonic waves may play an important role in drug or gene delivery systems in order to trap the drugs or genes in the diseased tissue. Usually, when bubbles are designed so that they carry payloads, such as drug or gene, they tend to be harder than free bubbles. These hard bubbles receive a small acoustic radiation force, which is not sufficient for bubble manipulation. In this paper, a novel method of microbubble manipulation using ultrasonic waves is proposed. This method uses seed bubbles in order to manipulate target bubbles. When the seed bubbles are introduced into the ultrasonic wave field, they start to oscillate to produce a bubble aggregation of a certain size. Then the target bubbles are introduced, the target bubbles attach around the seed bubbles producing a bubble mass with bilayers (inner layer: seed bubbles, outer layer: target bubbles). The target bubbles are manipulated as a bilayered bubble mass. Basic experiments are carried out using polyvinyl chloride (PVC) shell bubbles. No target bubbles are trapped when only the target bubbles are introduced. However, they are trapped if the seed bubbles are introduced in advance.

  5. Studies on equatorial shock formation during plasmaspheric refilling

    NASA Technical Reports Server (NTRS)

    Singh, Nagendra

    1993-01-01

    During the grant period starting August 1, 1992, our major effort has been on examining the presence of equatorially trapped hot plasma on plasmaspheric refilling. We performed one-dimensional PIC simulations of cold plasmas expanding into a hot plasma, consisting of hot anisotropic ions and warm isotropic electrons, trapped in a region of minimum magnetic field. Simulations showed that the electric potential barrier built up by the anisotropy of the hot ion population facilitates in the formation of electrostatic shocks when the cold ion beams begin to come into contact with the hot plasma. The shock formation occurs even when the cold ion beams are highly supersonic with respect to the ion-acoustic speed. This finding is interesting because equatorial shock formation during the early stage of plasmaspheric refilling has been debated over about two decades. In the past ion-ion instability has been invoked as the main mechanism for the coupling between the cold ion beams approaching the equator from the conjugate ionspheres. This coupling occurs when the beams are sufficiently slow; the beam velocity being less than three times the ion-acoustic speed. In the presence of hot plasma, the beams slow down by the potential barrier. The slowing down and the reflection process lead to the formation of the electrostatic shock even for highly supersonic ion beams. The mixing of hot and cold plasma was also studied.

  6. Calculated pulse widths and spectra of a single sonoluminescing bubble

    Microsoft Academic Search

    William C. Moss; Douglas B. Clarke; David A. Young

    1997-01-01

    A sonoluminescing bubble has been modeled as a thermally conducting, partially ionized, two-component plasma. The model shows that the measured picosecond pulse widths are due to electron conduction and the rapidly changing opacity of the plasma and that these mechanisms are also responsible for the absence of an {open_quotes}afterglow{close_quotes} subsequent to the sonoluminescence flash while the hot bubble expands and

  7. C/NOFS Satellite Electric Field and Plasma Density Observations of Plasma Instabilities Below the Equatorial F-Peak -- Evidence for Approximately 500 km-Scale Spread-F "Precursor" Waves Driven by Zonal Shear Flow and km-Scale, Narrow-Banded Irregularities

    NASA Technical Reports Server (NTRS)

    Pfaff, R.; Freudenreich, H.; Klenzing, J.; Liebrecht, C.; Valladares, C.

    2011-01-01

    As solar activity has increased, the ionosphere F-peak has been elevated on numerous occasions above the C/NOFS satellite perigee of 400km. In particular, during the month of April, 2011, the satellite consistently journeyed below the F-peak whenever the orbit was in the region of the South Atlantic anomaly after sunset. During these passes, data from the electric field and plasma density probes on the satellite have revealed two types of instabilities which had not previously been observed in the C/NOFS data set (to our knowledge): The first is evidence for 400-500km-scale bottomside "undulations" that appear in the density and electric field data. In one case, these large scale waves are associated with a strong shear in the zonal E x B flow, as evidenced by variations in the meridional (outward) electric fields observed above and below the F-peak. These undulations are devoid of smaller scale structures in the early evening, yet appear at later local times along the same orbit associated with fully-developed spread-F with smaller scale structures. This suggests that they may be precursor waves for spread-F, driven by a collisional shear instability, following ideas advanced previously by researchers using data from the Jicamarca radar. A second new result (for C/NOFS) is the appearance of km-scale irregularities that are a common feature in the electric field and plasma density data that also appear when the satellite is below the F -peak at night. The vector electric field instrument on C/NOFS clearly shows that the electric field component of these waves is strongest in the zonal direction. These waves are strongly correlated with simultaneous observations of plasma density oscillations and appear both with, and without, evidence of larger-scale spread-F depletions. These km-scale, quasi-coherent waves strongly resemble the bottomside, sinusoidal irregularities reported in the Atmosphere Explorer satellite data set by Valladares et al. [JGR, 88, 8025, 1983]. We interpret these new observations in terms of fundamental plasma instabilities associated with the unstable, nighttime equatorial ionosphere.

  8. Interdecadal Sea Surface Temperature Variability in the Equatorial Pacific Ocean. Part II: The Role of Equatorial/Off-Equatorial Wind Stresses in a Hybrid

    E-print Network

    Power, Scott

    to investigate the role of oceanic Rossby waves linking the off-equatorial and equatorial Pacific Ocean. Although, it is clear that off-equatorial oceanic Rossby waves affect equatorial Pacific Ocean variability an oceanic Rossby wave to cross the Pacific Ocean basin in the equatorial region). However, the results also

  9. GPS Occultation Observations of Equatorial Scintillation: Dependence on Magnetic Field Orientation, Longitude, and Season

    NASA Astrophysics Data System (ADS)

    Anderson, P. C.; Straus, P. R.

    2004-12-01

    We analyzed GPS occultation data from the CHAMP, SAC-C, and PICOSat satellite for the entire year 2002 identifying radiowave scintillation occurrence from SNR measurements of the C/A code on the L1 frequency obtained at the 1-second rate cadence. Global distributions clearly indicate that we are observing equatorial scintillation and scintillation in the auroral zones and polar cap. Seasonal and magnetic local time distributions of the low-latitude observations are in good agreement with the known distributions of equatorial scintillation. Longitudinal distributions vary somewhat from the WBMOD climatological model, particularly in the African sector where scintillation is observed nearly all year. A strong dependence on the orientation of the occultation ray path with the magnetic field orientation is observed with a low probability of scintillation at ray path angles perpendicular to the magnetic field and high probability of observations at smaller angles. This is interpreted as the result of the orientation of the ionospheric bubbles responsible for the scintillation. The walls of the bubbles, on which the instabilities that cause the scintillation occur, are typically aligned with the magnetic field. Thus, occultation ray paths along the magnetic field pass along the edge of the bubbles and remain within the region of instabilities for a longer period that ray paths perpendicular to the magnetic field and the bubble walls.

  10. Soap and Bubbles

    NSDL National Science Digital Library

    Brieske, Joel A.

    2002-01-01

    The first Web site, from The Soap and Detergent Association, is called Soaps and Detergents (1). Visitors learn about the chemistry of soap and detergent, their history, how they're manufactured, and more. The easily read text and fun illustrations make this site a great place to start for this topic. The next site, called Bubble Engineering (2), is provided by Bubble Town. The page describes the physics of a cone-shaped bubble blowing device and how its shape reduces the velocity of air being blown through but not the volume of air moving through it. Other links on the site describe what the contents of the best bubble soap mixture. The third site is provided by Kevin Dunn of Hampden-Sydney College Department of Chemistry called Lye Soap (3). The site describes how soap was invented, the chemistry of lye and soap, how to make your own lye, and more. The fourth site highlighted is part of LessonPlansPage.com called Looking at Bubbles (4). The site, which is a lesson plan, is geared towards students between grades 6 and 8. The main objective of the chemistry activity is to explore what things can be added to soap to make the bubbles last longer. All procedures are provided to view online or to print. The Art and Science of Bubbles (5) Web site is maintained by the Soap and Detergent Association. Many great features can be found on this and other pages within the site, including washing hands with soap, the history and chemistry of soaps and detergents, the environmentally smart way of using and disposing of cleaning products, and more. The sixth site related to soap is entitled Bubble Games (6), which is maintained by bubbles.org. Three free games are offered here including Tic-Tac-Bubble, Bubblechase, and Bubble Wrap, which counts how many bubbles you can pop in twenty seconds. Next, from the Homeschooling page of About.com comes the Soap Power (7) activity. This unique lesson plan details how to power a model boat using soap as a result of its surface tension. Lastly, the Bubble Hydrodynamics (8) Web site is maintained by bubbleology.com. Visitors get an introduction to bubble hydrodynamics and also learn about the relationship between temperature and bubbles, surfactants and bubbles, and even oscillations and bubbles.

  11. Electrowetting of soap bubbles

    NASA Astrophysics Data System (ADS)

    Arscott, Steve

    2013-07-01

    A proof-of-concept demonstration of the electrowetting-on-dielectric of a sessile soap bubble is reported here. The bubbles are generated using a commercial soap bubble mixture—the surfaces are composed of highly doped, commercial silicon wafers covered with nanometer thick films of Teflon®. Voltages less than 40 V are sufficient to observe the modification of the bubble shape and the apparent bubble contact angle. Such observations open the way to inter alia the possibility of bubble-transport, as opposed to droplet-transport, in fluidic microsystems (e.g., laboratory-on-a-chip)—the potential gains in terms of volume, speed, and surface/volume ratio are non-negligible.

  12. Gas bubble detector

    NASA Technical Reports Server (NTRS)

    Mount, Bruce E. (Inventor); Burchfield, David E. (Inventor); Hagey, John M. (Inventor)

    1995-01-01

    A gas bubble detector having a modulated IR source focused through a bandpass filter onto a venturi, formed in a sample tube, to illuminate the venturi with modulated filtered IR to detect the presence of gas bubbles as small as 0.01 cm or about 0.004 in diameter in liquid flowing through the venturi. Means are provided to determine the size of any detected bubble and to provide an alarm in the absence of liquid in the sample tube.

  13. Bubbles: Using Controls

    NSDL National Science Digital Library

    2012-06-26

    In this experiment, learners use JOY liquid detergent and glycerin to make the largest bubble they can that lasts 15 seconds. They blow the bubbles in a Teaching Tank, a narrow tank that is commercially available, which allows them to easily measure and monitor the bubbles. Results are collected and graphed by learners. Questions and teaching notes are included to encourage learners to consider what the multiple variables are, and what the effects of sugar, corn syrup, or other sweeteners are on their bubbles.

  14. Sonochemistry and bubble dynamics.

    PubMed

    Mettin, Robert; Cairós, Carlos; Troia, Adriano

    2015-07-01

    The details of bubble behaviour in chemically active cavitation are still not sufficiently well understood. Here we report on experimental high-speed observations of acoustically driven single-bubble and few-bubble systems with the aim of clarification of the connection of their dynamics with chemical activity. Our experiment realises the sonochemical isomerization reaction of maleic acid to fumaric acid, mediated by bromine radicals, in a bubble trap set-up. The main result is that the reaction product can only be observed in a parameter regime where a small bubble cluster occurs, while a single trapped bubble stays passive. Evaluations of individual bubble dynamics for both cases are given in form of radius-time data and numerical fits to a bubble model. A conclusion is that a sufficiently strong collapse has to be accompanied by non-spherical bubble dynamics for the reaction to occur, and that the reason appears to be an efficient mixing of liquid and gas phase. This finding corroborates previous observations and literature reports on high liquid phase sonochemical activity under distinct parameter conditions than strong sonoluminescence emissions. PMID:25194210

  15. Original paper Soap Bubble Clusters

    E-print Network

    Taylor, Jean

    Original paper Soap Bubble Clusters Fred ALMGREN surface, soap bubbles Abstract. This article reviews the theorems from geometric measure theory which guarantee the existence and give the structure of mathematical models of soap bubble clusters. It also

  16. Nature of the `extreme conditions` in single sonoluminescing bubbles

    SciTech Connect

    Lepoint-Mullie, F.; De Pauw, D.; Lepoint, T. [Institut Meurice-CERIA, Brussels (Belgium)] [Institut Meurice-CERIA, Brussels (Belgium); Supiot, P. [Universite des Sciences et Technologies de Lille, Villeneuve d`Ascq (France)] [Universite des Sciences et Technologies de Lille, Villeneuve d`Ascq (France); Avni, R. [NRC Negev, Beer-Sheva (Israel)] [NRC Negev, Beer-Sheva (Israel); [BG Univ., Beer-Sheva (Israel)

    1996-07-25

    A plasma diagnostics analysis is reported which looks at the experimental spectrum of the sonoluminescence emitted by a single argon bubble oscillating nonlinearly in an acoustic field. Under the hypothesis that the bubble is mainly filled with Ar atoms able to participate in the plasma, an order-of-magnitude estimation of the electron density (N{sub e}) associated with the intracavity medium gives N{sub e} = 10{sup 25} m{sup -3}, with an electronic temperature estimated to be about 20000 K, perhaps more. This analysis suggests that the conditions at the root of single-bubble sonoluminescence are highly energy charged and may be compatible with a sparklike process. The plasma developed inside the argon bubble is assumed to be in local thermodynamic equilibrium. 26 refs., 4 figs.

  17. Novel Mechanism for Single Bubble Sonoluminescence

    E-print Network

    Lavrov, B P

    2001-01-01

    Careful re-examination of typical experimental data made it possible to show that the UV continua observed in multi-bubble (MBSL) and single-bubble (SBSL) sonoluminescence spectra have the same physical nature - radiative dissociation of electronically excited hydrogen molecules [and probably hydrides of heavy rare gases like ArH*] due to spontaneous transitions between bound and repulsive electronic states. The proposed mechanism is able to explain all available spectroscopic observations without any exotic hypothesis but in terms usual for plasma spectroscopy.

  18. Prospects for bubble fusion

    SciTech Connect

    Nigmatulin, R.I. [Tyumen Institute of Mechanics of Multiphase Systems (TIMMS), Marx (Russian Federation); Lahey, R.T. Jr. [Rensselaer Polytechnic Institute, Troy, NY (United States)

    1995-09-01

    In this paper a new method for the realization of fusion energy is presented. This method is based on the superhigh compression of a gas bubble (deuterium or deuterium/thritium) in heavy water or another liquid. The superhigh compression of a gas bubble in a liquid is achieved through forced non-linear, non-periodic resonance oscillations using moderate amplitudes of forcing pressure. The key feature of this new method is a coordination of the forced liquid pressure change with the change of bubble volume. The corresponding regime of the bubble oscillation has been called {open_quotes}basketball dribbling (BD) regime{close_quotes}. The analytical solution describing this process for spherically symmetric bubble oscillations, neglecting dissipation and compressibility of the liquid, has been obtained. This solution shown no limitation on the supercompression of the bubble and the corresponding maximum temperature. The various dissipation mechanisms, including viscous, conductive and radiation heat losses have been considered. It is shown that in spite of these losses it is possible to achieve very high gas bubble temperatures. This because the time duration of the gas bubble supercompression becomes very short when increasing the intensity of compression, thus limiting the energy losses. Significantly, the calculated maximum gas temperatures have shown that nuclear fusion may be possible. First estimations of the affect of liquid compressibility have been made to determine possible limitations on gas bubble compression. The next step will be to investigate the role of interfacial instability and breaking down of the bubble, shock wave phenomena around and in the bubble and mutual diffusion of the gas and the liquid.

  19. Interplay Between the Equatorial Geophysical Processes

    NASA Astrophysics Data System (ADS)

    Sridharan, R.

    2006-11-01

    r_sridharanspl@yahoo.com With the sun as the main driving force, the Equatorial Ionosphere- thermosphere system supports a variety of Geophysical phenomena, essentially controlled by the neutral dynamical and electro dynamical processes that are peculiar to this region. All the neutral atmospheric parameters and the ionospheric parameters show a large variability like the diurnal, seasonal semi annual, annual, solar activity and those that are geomagnetic activity dependent. In addition, there is interplay between the ionized and the neutral atmospheric constituents. They manifest themselves as the Equatorial Electrojet (EEJ), Equatorial Ionization Anomaly (EIA), Equatorial Spread F (ESF), Equatorial Temperature and Wind Anomaly (ETWA). Recent studies have revealed that these phenomena, though apparently might show up as independent ones, are in reality interlinked. The interplay between these equatorial processes forms the theme for the present talk.

  20. Single-bubble sonoluminescence

    Microsoft Academic Search

    Michael P. Brenner; Sascha Hilgenfeldt; Detlef Lohse

    2002-01-01

    Single-bubble sonoluminescence occurs when an acoustically trapped and periodically driven gas bubble collapses so strongly that the energy focusing at collapse leads to light emission. Detailed experiments have demonstrated the unique properties of this system: the spectrum of the emitted light tends to peak in the ultraviolet and depends strongly on the type of gas dissolved in the liquid; small

  1. The Dueling Bubble Experiment

    Microsoft Academic Search

    Anshuman Roy; Marcos Borrell; John Felts; Gary Leal; Amir Hirsa

    2007-01-01

    When two drops or bubbles are brought into close proximity to each other, the thin film of the fluid between them drains as they are squeezed together. If the film becomes thin enough that intermolecular forces of attraction overwhelm capillary forces, the drops\\/bubbles coalesce and the time it takes for this to happen, starting from the point of apparent contact

  2. Gases in Tektite Bubbles.

    PubMed

    O'keefe, J A; Lowman, P D; Dunning, K L

    1962-07-20

    Spectroscopic analysis of light produced by electrodeless discharge in a tektite bubble showed the main gases in the bubble to be neon, helium, and oxygen. The neon and helium have probably diffused in from the atmosphere, while the oxygen may be atmospheric gas incorporated in the tektite during its formation. PMID:17801113

  3. Evaporation, Boiling and Bubbles

    ERIC Educational Resources Information Center

    Goodwin, Alan

    2012-01-01

    Evaporation and boiling are both terms applied to the change of a liquid to the vapour/gaseous state. This article argues that it is the formation of bubbles of vapour within the liquid that most clearly differentiates boiling from evaporation although only a minority of chemistry textbooks seems to mention bubble formation in this context. The…

  4. Let Them Blow Bubbles.

    ERIC Educational Resources Information Center

    Korenic, Eileen

    1988-01-01

    Describes a series of activities and demonstrations involving the science of soap bubbles. Starts with a recipe for bubble solution and gives instructions for several activities on topics such as density, interference colors, optics, static electricity, and galaxy formation. Contains some background information to help explain some of the effects.…

  5. Steepened structures in equatorial spread F. 2: Theory

    NASA Technical Reports Server (NTRS)

    Hysell, D. L; Seyler, C. E.; Kelley, M. C.

    1994-01-01

    This paper investigates the properties of a one-dimensional fluid model of plasma convection in the equatorial F region ionosphere. The model equations are similar in form to Burgers equation except for additional higher-order spatial derivatives. Like Burgers equation, solution to the model have the form of propagating, shocklike structures. Numerical simulations of the model closely resemble the steepened structures observed by sounding rocket plasma density probes within equatorial spread F. Simulated denstiy power spectra, like the spectra computed from in situ data, seem to possess power law forms with a break at wavelengths of about 100 m. The precise wavenumber of the spectral break is determined by the ambipolar diffusion coefficient. The model predicts that electric field fluctuations perpendicular to the direction of plasma steepening should be proportional to the plasma density fluctuations. Electric field fluctuations parallel to the steepening will be due primarily to the ambipolar field and have a Boltzmann relationship with density (square of the absolute value of delta E) approximately equal to (K(exp 2))(square of the absolute value of (delta n/n)). At wavelengths less than about 300 m, the ambipolar field should be the dominant component of the total field intensity.

  6. MJO, Equatorial Waves, and Tropical Cyclogenesis

    NSDL National Science Digital Library

    COMET

    2012-11-13

    This case study focuses on monitoring of the MJO and equatorial waves and their role in tropical cyclogenesis. Learners will use conceptual models to understand the structure of the MJO and equatorial waves. They will identify and monitor those circulations using geostationary satellite images. 850-hPa synoptic analysis is used to track equatorial Rossby and mixed Rossby-gravity waves. Focus is on May 2002, a period when an MJO and associated equatorial waves spawned sets of twin cyclones over the Indian Ocean. This case study is similar to a synoptic meteorology laboratory exercise but is designed for use in an online course.

  7. Radio wave scintillations at equatorial regions

    NASA Technical Reports Server (NTRS)

    Poularikas, A. D.

    1972-01-01

    Radio waves, passing through the atmosphere, experience amplitude and phase fluctuations know as scintillations. A characterization of equatorial scintillation, which has resulted from studies of data recorded primarily in South America and equatorial Africa, is presented. Equatorial scintillation phenomena are complex because they appear to vary with time of day (pre-and postmidnight), season (equinoxes), and magnetic activity. A wider and more systematic geographical coverage is needed for both scientific and engineering purposes; therefore, it is recommended that more observations should be made at earth stations (at low-geomagnetic latitudes) to record equatorial scintillation phenomena.

  8. Equatorial refuge amid tropical warming

    NASA Astrophysics Data System (ADS)

    Karnauskas, Kristopher B.; Cohen, Anne L.

    2012-07-01

    Upwelling across the tropical Pacific Ocean is projected to weaken in accordance with a reduction of the atmospheric overturning circulation, enhancing the increase in sea surface temperature relative to other regions in response to greenhouse-gas forcing. In the central Pacific, home to one of the largest marine protected areas and fishery regions in the global tropics, sea surface temperatures are projected to increase by 2.8°C by the end of this century. Of critical concern is that marine protected areas may not provide refuge from the anticipated rate of large-scale warming, which could exceed the evolutionary capacity of coral and their symbionts to adapt. Combining high-resolution satellite measurements, an ensemble of global climate models and an eddy-resolving regional ocean circulation model, we show that warming and productivity decline around select Pacific islands will be mitigated by enhanced upwelling associated with a strengthening of the equatorial undercurrent. Enhanced topographic upwelling will act as a negative feedback, locally mitigating the surface warming. At the Gilbert Islands, the rate of warming will be reduced by 0.7+/-0.3°C or 25+/-9% per century, or an overall cooling effect comparable to the local anomaly for a typical El Niño, by the end of this century. As the equatorial undercurrent is dynamically constrained to the Equator, only a handful of coral reefs stand to benefit from this equatorial island effect. Nevertheless, those that do face a lower rate of warming, conferring a significant advantage over neighbouring reef systems. If realized, these predictions help to identify potential refuges for coral reef communities from anticipated climate changes of the twenty-first century.

  9. The Fermi bubbles revisited

    NASA Astrophysics Data System (ADS)

    Yang, Rui-zhi; Aharonian, Felix; Crocker, Roland

    2014-07-01

    We analyze 60 months of all-sky data from the Fermi-LAT. The Fermi bubble structures discovered previously are clearly revealed by our analysis. With more data, hence better statistics, we can now divide each bubble into constant longitude slices to investigate their gross ?-ray spectral morphology. While the detailed spectral behavior of each slice derived in our analysis is somewhat dependent on the assumed background model, we find, robustly, a relative deficit in the flux at low energies (i.e., hardening) toward the top of the south bubble. In neither bubble does the spectrum soften with longitude. The morphology of the Fermi bubbles is also revealed to be energy-dependent: at high energies they are more extended. We conclude from the gamma-ray spectrum at high latitudes that a low energy break in the parent cosmic ray population is required in both leptonic and hadronic models. We briefly discuss possible leptonic and hadronic interpretations of this phenomenology.

  10. Equatorial flattenings of planets - Venus

    NASA Astrophysics Data System (ADS)

    Bursa, M.; Sima, Z.

    1985-05-01

    The dimensions of Venus were found in order to calculate the degree of flattening due to gravity. The calculations were carried out within the framework of the general flattening theory of Bursa and Sima (1969). Data on the gravitational field of Venus, obtained during observations by Mottinger and Williams (1983) were incorporated in the equations. It is shown that the figure of Venus is different from all terrestrial bodies in the solar system: the surface in the equatorial zone is located above the best-fitting triaxial Venus ellipsoid. Deflections of the vertical at the planet surface are given.

  11. Anomalous opening of the Equatorial Atlantic due to an equatorial mantle thermal minimum

    Microsoft Academic Search

    Enrico Bonatti

    1996-01-01

    The geology of the Equatorial Atlantic is dominated by a broad east-west megashear belt where a cluster of large fracture zones offsets anomalously deep segments of the Mid-Atlantic Ridge (MAR). The origin and evolution of this megashear region may lie ultimately in an equatorial mantle thermal minimum. The notion of a mantle thermal minimum in the Equatorial Atlantic is supported

  12. Central Equatorial Pacific Experiment (CEPEX)

    SciTech Connect

    Not Available

    1993-01-01

    The Earth's climate has varied significantly in the past, yet climate records reveal that in the tropics, sea surface temperatures seem to have been remarkably stable, varying by less than a few degrees Celsius over geologic time. Today, the large warm pool of the western Pacific shows similar characteristics. Its surface temperature always exceeds 27[degree]C, but never 31[degree]C. Heightened interest in this observation has been stimulated by questions of global climate change and the exploration of stabilizing climate feedback processes. Efforts to understand the observed weak sensitivity of tropical sea surface temperatures to climate forcing has led to a number of competing ideas about the nature of this apparent thermostat. Although there remains disagreement on the processes that regulate tropical sea surface temperature, most agree that further progress in resolving these differences requires comprehensive field observations of three-dimensional water vapor concentrations, solar and infrared radiative fluxes, surface fluxes of heat and water vapor, and cloud microphysical properties. This document describes the Central Equatorial Pacific Experiment (CEPEX) plan to collect such observations over the central equatorial Pacific Ocean during March of 1993.

  13. Bubbles, Bubbles: Integrated Investigations with Floating Spheres

    ERIC Educational Resources Information Center

    Reeder, Stacy

    2007-01-01

    In this article, the author describes integrated science and mathematics activities developed for fourth-grade students to explore and investigate three-dimensional geometric shapes, Bernoulli's principle, estimation, and art with and through bubbles. Students were engaged in thinking and reflection on the questions their teachers asked and were…

  14. Bubble core field modification by residual electrons inside the bubble

    SciTech Connect

    Wu Haicheng [College of Nuclear Science and Technology, Beijing Normal University, Beijing 100875 (China); Center for Applied Physics and Technology, Peking University, Beijing 100084 (China); Xie Baisong; Zhao Xueyan [College of Nuclear Science and Technology, Beijing Normal University, Beijing 100875 (China); Zhang Shan [College of Nuclear Science and Technology, Beijing Normal University, Beijing 100875 (China); Department of Mathematics and Physics, Shijiazhuang Railway Institute, Shijiazhuang 050043 (China); Hong Xueren [College of Nuclear Science and Technology, Beijing Normal University, Beijing 100875 (China); College of Physics and Electronic Engineering, Northwest Normal University, Lanzhou 730070 (China); Liu Mingping [School of Information Engineering, Nanchang University, Nanchang 330031 (China)

    2010-11-15

    Bubble core field modification due to the nondepleted electrons present inside the bubble is investigated theoretically. These residual electrons induce charge and current densities that can induce the bubble core field modification as well as the bubble shape change. It is found that the electrons entering into the bubble move backward at almost light speed and would weaken the transverse bubble fields. This reduces the ratio of longitudinal to transverse radius of the bubble. For the longitudinal bubble field, two effects compensate with each other because of their competition between the enhancement by the shortening of bubble shape and the reduction by the residual electrons. Therefore the longitudinal field is hardly changeable. As a comparison we perform particle-in-cell simulations and it is found that the results from theoretical consideration are consistent with simulation results. Implication of the modification of fields on bubble electron acceleration is also discussed briefly.

  15. Tribonucleation of bubbles

    PubMed Central

    Wildeman, Sander; Lhuissier, Henri; Sun, Chao; Lohse, Detlef; Prosperetti, Andrea

    2014-01-01

    We report on the nucleation of bubbles on solids that are gently rubbed against each other in a liquid. The phenomenon is found to depend strongly on the material and roughness of the solid surfaces. For a given surface, temperature, and gas content, a trail of growing bubbles is observed if the rubbing force and velocity exceed a certain threshold. Direct observation through a transparent solid shows that each bubble in the trail results from the early coalescence of several microscopic bubbles, themselves detaching from microscopic gas pockets forming between the solids. From a detailed study of the wear tracks, with atomic force and scanning electron microscopy imaging, we conclude that these microscopic gas pockets originate from a local fracturing of the surface asperities, possibly enhanced by chemical reactions at the freshly created surfaces. Our findings will be useful either for preventing undesired bubble formation or, on the contrary, for “writing with bubbles,” i.e., creating controlled patterns of microscopic bubbles. PMID:24982169

  16. Slurry bubble column dynamics

    SciTech Connect

    Smith, D.N.; Ruether, J.A.; Stiegel, G.J.

    1983-01-01

    A novel approach utilizing an electrical conductivity twin-probe technique is described for obtaining important gas-phase characteristics such as: bubble size, velocity ad holdup fraction. A 10 cm internal diameter by 310 cm height glass column is employed to investigate the bubble dynamics measured with this probe. The liquid phase is composed of a mixture of ethanol and water that may have substantial ''surface activity'' which results in a dynamic surface tension effect on the rate of bubble coalescence. Measurements of gas holdup, bubble size,and velocity indicate the influence of surface activity onthe gas phase characteristics. Possible implications of these results on the hydrodynamics of Fischer-Tropsch reactors are given. An experimental technique and subsequent analysis have been developed to determine the bubble size and velocity distributions in a slurry bubble column cold model. Dynamic surface tension effects have been observed for a two component liquid mixture. The maximum frothing ability of a ''surface-active'' species qualitatively agrees with a dynamic surface tension model. Increased gas holdup and interfacial area are observed with the addition of a ''surface-active'' component. In addition, increased gas holdup and interfacial area are observed with a sintered plate distributor compared to a perforated plate. The presence of solids reduces the gas holdup and increases the bubble size. 11 refs., 11 figs.

  17. Tribonucleation of bubbles.

    PubMed

    Wildeman, Sander; Lhuissier, Henri; Sun, Chao; Lohse, Detlef; Prosperetti, Andrea

    2014-07-15

    We report on the nucleation of bubbles on solids that are gently rubbed against each other in a liquid. The phenomenon is found to depend strongly on the material and roughness of the solid surfaces. For a given surface, temperature, and gas content, a trail of growing bubbles is observed if the rubbing force and velocity exceed a certain threshold. Direct observation through a transparent solid shows that each bubble in the trail results from the early coalescence of several microscopic bubbles, themselves detaching from microscopic gas pockets forming between the solids. From a detailed study of the wear tracks, with atomic force and scanning electron microscopy imaging, we conclude that these microscopic gas pockets originate from a local fracturing of the surface asperities, possibly enhanced by chemical reactions at the freshly created surfaces. Our findings will be useful either for preventing undesired bubble formation or, on the contrary, for "writing with bubbles," i.e., creating controlled patterns of microscopic bubbles. PMID:24982169

  18. Aerator Combined With Bubble Remover

    NASA Technical Reports Server (NTRS)

    Dreschel, Thomas W.

    1993-01-01

    System produces bubble-free oxygen-saturated water. Bubble remover consists of outer solid-walled tube and inner hydrophobic, porous tube. Air bubbles pass from water in outer tube into inner tube, where sucked away. Developed for long-term aquaculture projects in space. Also applicable to terrestrial equipment in which entrained bubbles dry membranes or give rise to cavitation in pumps.

  19. Rotating bubble membrane radiator

    DOEpatents

    Webb, Brent J. (West Richland, WA); Coomes, Edmund P. (West Richland, WA)

    1988-12-06

    A heat radiator useful for expelling waste heat from a power generating system aboard a space vehicle is disclosed. Liquid to be cooled is passed to the interior of a rotating bubble membrane radiator, where it is sprayed into the interior of the bubble. Liquid impacting upon the interior surface of the bubble is cooled and the heat radiated from the outer surface of the membrane. Cooled liquid is collected by the action of centrifical force about the equator of the rotating membrane and returned to the power system. Details regarding a complete space power system employing the radiator are given.

  20. Equatorial ionosphere 'fountain- effect' above imminent earthquake epicenter

    NASA Astrophysics Data System (ADS)

    Ruzhin, Yu.; Depueva, A. H.; Devi, M.

    2003-04-01

    Existence of lithosphere-ionosphere interaction is known for a long time, but it does not mean that the ionospheric morphology above areas of earthquakes preparation is investigated sufficiently well. It was shown that seismo-precursor variations of the atmosphere electricity cause appropriate electric field at the ionospheric heights, which being added to existing natural field may both increase or decrease its action on the ionospheric plasma characteristics: drifts, aeronomy, plasma chemistry, ion composition etc. Anomalous variations appear inside whole ionosphere volume from the lowest boundary of Earth's plasma shell (100 km) up to 1000km and higher. Under fortunate coincidence seismo-precursor electric field can generate natural ionosphere phenomena, 'fountain- effect', leading to Appleton anomaly in the equatorial ionosphere over future earthquake position. Our basic idea is to take into account dependence of the observable effects on a geographical position of the earthquake epicenter. As for low latitudes it is proved by specificity of formation and dynamics of equatorial ionosphere (seismogenic ""fountain" effect , first of all), and also by features of earth crust structure close to the equator (mainly meridionally alongated tectonic faults). Ionospheric effects of low-latitude earthquakes were not investigated separately so far though rather semo-active zones are located namely at low latitudes: India, Peru, Oceania. We used the data of topside sounding of ALOUETTE-1 and ISS-b satellites, and also data of ground-based vertical sounding stationary stations Kodaikanal, Huancayo, Djibouti etc. and records of the total electron content (TEC).

  1. Equatorial potassium currents in lenses.

    PubMed

    Wind, B E; Walsh, S; Patterson, J W

    1988-02-01

    Earlier work with the vibrating probe demonstrated the existence of outward potassium currents at the equator and inward sodium currents at the optical poles of the lens. By adding microelectrodes to the system, it is possible to relate steady currents (J) to the potential difference (PD) measured with a microelectrode. By injecting an outward current (I), it is possible to determine resistances and also the PD at which the steady outward potassium current becomes zero (PDJ = 0). At this PD the concentration gradient for potassium efflux and the electrical gradient for potassium influx are balanced so that there is no net flow of potassium across the membranes associated with the production of J. The PDJ = 0 for 18 rat lenses was 86 mV and that for 12 frogs lenses was -95 mV. This agrees with the potassium equilibrium potential and provides strong evidence to support the view that the outward equatorial current, J, is a potassium current. With the injection of outward current, I, the PD becomes more negative, the outward equatorial current, J, decreases, and the inward current at the optical poles increases. This suggests that there are separate electrical loops for K+ and Na+ that are partially linked by the Na, K-pump. Using Ohm's law, it is possible to calculate the input resistance (R = delta PD/I), the resistance related to the production of J (RJ = delta PD/delta J), and the effect of the combined resistances (delta J/I). The driving force for J can be estimated (PDJ = 0-PD). The relationships among currents, voltages and resistance can be used to determine the characteristics of the membranes that are associated with the outward potassium current observed at the equator. The effects of graded deformation of the lens were determined. The effects were reversible. The sites of inward and outward currents were not altered. Following deformation, the equatorial current, J, increased, and the PD became less negative. The PDJ = 0 remains the same so the ratio of K+ concentrations across the membrane responsible for J is unchanged. Therefore, the decrease in PD is ascribed to an increase in Na+ permeance with a resultant increase in driving force accounting for the increase in J. PMID:3258245

  2. Single Bubble SonoLuminescence of Particles model

    E-print Network

    Mahamadou Adama Maiga

    2012-12-05

    The Single Bubble SonoLuminescence is a phenomenon where the vapor bubble trapped in a liquid collapse by emitting of a light. It is very known that the temperature inside the bubble depends on the radius, during the collapse, the temperature can reach thousands of Kelvins and that the light would be emitted by radiation of the ionized gas inside the bubble. So, studies show that in certain cases neither an imploding shock nor a plasma has been observed and the temperature is not high enough to explain the spectrum observed. The Single Bubble SonoLuminescence remains a subject of study. For this study we consider the bubble as a box where the free particles (particularly electrons) stemming from the molecules dissociation, are are trapped and confined within the bubble. The confinement allows the particles to acquire some energy during the collapse which they lose in the form of light and also to be considered to bind to the bubble as an electron is bound to the nucleus in an atom. So, with regard to the bubble the energy of the particles can be considered to quantify, and with the quantum theory, by putting some hypotheses, their energy is determined well. The energy is physically acceptable that if the bubble is spherical. This necessary condition of a spherical bubble of the model is observed experimentally in the collapse phase but not in the afterbounce phase of the bubble, explain why the bubble emits of light in the collapse but not in the phase of the afterbounces where she can be smaller, and constitute a validation of the Single Bubble SonoLuminescence of particles model. For the application of the Single Bubble SonoLuminescence of particles model we consider a electron free particle of mass . We note that the interval of time between and energy (who can be considered as the duration when the bubble emits some light) is of the order of picoseconds, the same order that the shortest pulses observed experimentally.

  3. Fermi gamma -ray `bubbles' from stochastic acceleration of electrons

    NASA Astrophysics Data System (ADS)

    Mertsch, Philipp; Sarkar, Subir

    Gamma-ray data from the Fermi-LAT show a bi-lobular structure extending up to 50 degrees above and below the Galactic centre, coincident with a possibly related structure in the ROSAT X-ray map. It has been argued that the gamma -rays arise due to inverse Compton scattering of relativistic electrons accelerated at plasma shocks present in the bubbles. We explore the alternative possibility that the relativistic electrons undergo stochastic 2nd-order Fermi acceleration in the entire volume of the bubbles by plasma wave turbulence. This turbulence is generated behind the outer shock and propagates into the bubble volume, leading to a non-trivial spatial variation of the electron spectral index. Rather than a constant volume emissivity as predicted in other models we find an almost constant surface brightness in gamma -rays and also reproduce the observed sharp edges of the bubbles. We comment on possible cross-checks in other channels.

  4. Patterns of equatorial drifts according to diverse observational probes

    NASA Astrophysics Data System (ADS)

    Oyekola, Oyedemi S.

    We examine morphological patterns of observational results of the equatorial vertical E×B drifts obtained from different probing methods (VHF radar at Jicamarca, Ion Drift Meter on the AE-E satellite, drifts derived from ionosonde h’F data at Ibadan (Nigeria) over 1-year, and HF Doppler at Trivandrum (India)) during the evening and nighttime periods for geomagnetic quiet-day and high solar activity conditions (F10.7 ranges from ~160-208 sfu) for three different seasonal periods. A direct comparison between these measurements and the International Reference Ionosphere 2007 (IRI-2007) model-predictions of equatorial vertical plasma drifts are also made. Our results show that while VHF, AE-E and ionosonde-inferred drifts generally exhibit the typical characteristic features of quiet-time equatorial electrodynamics but reveal substantial disparities in the observational techniques of F-region vertical drifts. The trends in the experimental data agree reasonably with the Scherliess-Fejer climatological curves for the three seasons. In contrast, an IRI representation grossly overestimates and show large departure from the Ibadan and Trivandrum Doppler drift patterns between 1500-0100 LT. The model peak velocity occurs at about two hours earlier than the ionosonde and HF-Doppler velocity peaks. The magnitudes of the velocity peak differ by approximately 28 percent. The dusk reversal times fluctuate significantly and occur between about 1800-2200 LT for all the drift techniques. On the other hand, reversal times near sunrise show less variation. The essential feature of equatorial electrodynamics is the evening prereversal enhancement (PRE) peak velocity; a key parameter required to trigger postsunset ionospheric irregularities. We demonstrate that the simulated PRE ranges between about 20-50 m/s with average value (standard deviation) of roughly 37+/-11 m/s; whereas Ibadan ionosonde PRE velocities vary from about 20 to 45 m/s, with typical average value (standard deviation) of about 29+/-6 m/s. Assessment of the association between model and ionosonde PRE velocities with solar F10.7 and geomagnetic Ap indices illustrate that both IRI and ionosonde-inferred PRE peak velocities illustrate no noticeable link with solar flux, but correlate well with geomagnetic activity. This high correlation is an unexpected result which might shed new light on sources of quiet-time variability of the equatorial PRE peak vertical plasma velocities.

  5. What's in a Bubble?

    ERIC Educational Resources Information Center

    Saunderson, Megan

    2000-01-01

    Describes a unit on detergents and bubbles that establishes an interest in the properties of materials and focuses on active learning involving both hands- and minds-on learning rather than passive learning. (ASK)

  6. Bubble impacts with microcantilevers.

    NASA Astrophysics Data System (ADS)

    Stegmeir, Matthew; Longmire, Ellen; Ali, Mubassar; Mantell, Susan

    2006-11-01

    In the current study, we investigate bubbles in laminar channel flows impacting microcantilever obstacles. Static and resonating cantilevers instrumented with integrated strain gages are mounted perpendicular to the mean flow in a vertically-oriented channel with thickness 2mm, span 10mm, and length 585 mm. Steady, fully-developed upward flows with channel Reynolds numbers based on mean fluid velocity and hydraulic diameter of 0-2500 are considered. Bubbles of diameter 200-1000?m are introduced upstream of the test section, and impacts are observed using a microscope equipped with a high frame rate camera. Observations are made along the length of cantilevers backlit with white light. Strain gage signals are monitored and correlated to impact events. The effect of obstacles on bubble motion and deformation as well as the effect of bubble impacts on the cantilever will be discussed. The flow studies are part of a larger research program examining reliability and performance of vibrating microbeams.

  7. Chemistry in Soap Bubbles.

    ERIC Educational Resources Information Center

    Lee, Albert W. M.; Wong, A.; Lee, H. W.; Lee, H. Y.; Zhou, Ning-Huai

    2002-01-01

    Describes a laboratory experiment in which common chemical gases are trapped inside soap bubbles. Examines the physical and chemical properties of the gases such as relative density and combustion. (Author/MM)

  8. The Adaptive Bubble Router

    Microsoft Academic Search

    Valentin Puente; Cruz Izu; Ramón Beivide; José A. Gregorio; Fernando Vallejo; J. M. Prellezo

    2001-01-01

    The design of a new adaptive virtual cut-through router for torus networks is presented in this paper. With much lower VLSI costs than adaptive wormhole routers, the adaptive Bubble router is even faster than deterministic wormhole routers based on virtual channels. This has been achieved by combining a low-cost deadlock avoidance mechanism for virtual cut-through networks, called Bubble flow control,

  9. Nonplanar mhd model for solar flare-generated disturbances in the heliospheric equatorial plane

    Microsoft Academic Search

    S. T. Wu; M. Dryer; S. M. Han

    1983-01-01

    An analysis, with a representative (canonical) example of solar-flare-generated equatorial disturbances, is presented for the temporal and spatial changes in the solar wind plasma and magnetic field environment between the Sun and one astronomical unit (AU). Our objective is to search for first order global consequences rather than to make a parametric study. The analysis - an extension of earlier

  10. Single Bubble SonoLuminescence of Particles model

    E-print Network

    Maiga, Mahamadou Adama

    2012-01-01

    The Single Bubble SonoLuminescence is a phenomenon where the vapor bubble trapped in a liquid collapse by emitting of a light. It is very known that the temperature inside the bubble depends on the radius, during the collapse, the temperature can reach thousands of Kelvins and that the light would be emitted by radiation of the ionized gas inside the bubble. So, studies show that in certain cases neither an imploding shock nor a plasma has been observed and the temperature is not high enough to explain the spectrum observed. The Single Bubble SonoLuminescence remains a subject of study. For this study we consider the bubble as a box where the free particles (particularly electrons) stemming from the molecules dissociation, are are trapped and confined within the bubble. The confinement allows the particles to acquire some energy during the collapse which they lose in the form of light and also to be considered to bind to the bubble as an electron is bound to the nucleus in an atom. So, with regard to the bubb...

  11. Clustering in Bubble Suspensions

    NASA Astrophysics Data System (ADS)

    Zenit, Roberto

    2000-11-01

    A monidisperse bubble suspension is studied experimentally for the limit in which the Weber number is small and the Reynolds number is large. For this regime the suspension can be modeled using potential flow theory to describe the dynamics of the interstitial fluid. Complete theoretical descriptions have been composed (Spelt and Sangani, 1998) to model the behavior of these suspensions. Bubble clustering is a natural instability that arises from the potential flow considerations, in which bubbles tend to align in horizontal rafts as they move upwards. The appearance of bubble clusters was recently corroborated experimentally by Zenit et al. (2000), who found that although clusters did appear, their strength was not as strong as the predictions. Experiments involving gravity driven shear flows are used to explain the nature of the clustering observed in these type of flows. Balances of the bubble phase pressure (in terms of a calculated diffusion coefficient) and the Maxwell pressure (from the potential flow description) are presented to predict the stability of the bubble suspension. The predictions are compared with experimental results.

  12. Computed optical emissions from a sonoluminescing bubble

    SciTech Connect

    Moss, W.C.; Young, D.A.; Harte, J.A.; Levatin, J.L.; Rozsnyai, B.F.; Zimmerman, G.B.; Zimmerman, I.H. [Lawrence Livermore National Laboratory, P. O. Box 808, Livermore, California 94550 (United States)] [Lawrence Livermore National Laboratory, P. O. Box 808, Livermore, California 94550 (United States)

    1999-03-01

    A sonoluminescing bubble has been modeled as a thermally conducting, partially ionized plasma. The model is more complete than previous models, due to the inclusion of both plasma and normal molecular thermal conduction, vapor pressure, surface tension, the mixing of gas and water vapor in the bubble, and opacities. The model accounts for most of the observed experimental trends, including (i) the asymmetric pulse shape; (ii) the temperature and driving pressure dependence of the pulse width and intensity; and (iii) spectral shapes, in particular, the 300-nm peak in the spectrum of xenon sonoluminescence, which to our knowledge has not been explained by any previous model; and (iv) a hydrodynamic explanation of why water is the {open_quotes}friendliest{close_quotes} liquid in which sonoluminescence occurs. The agreement between the calculations and the data, as well as the model`s predictions of almost every experimental trend, suggest strongly that the spectral and temporal properties of the emissions of a sonoluminescing bubble are due to adiabatic- or shock-initiated thermal emission from a cool dense plasma. {copyright} {ital 1999} {ital The American Physical Society}

  13. EQUATORIAL SUPERROTATION ON TIDALLY LOCKED EXOPLANETS

    SciTech Connect

    Showman, Adam P. [Department of Planetary Sciences and Lunar and Planetary Laboratory, University of Arizona, 1629 University Blvd., Tucson, AZ 85721 (United States); Polvani, Lorenzo M., E-mail: showman@lpl.arizona.edu [Department of Applied Physics and Applied Mathematics, Columbia University, New York, NY (United States)

    2011-09-01

    The increasing richness of exoplanet observations has motivated a variety of three-dimensional (3D) atmospheric circulation models of these planets. Under strongly irradiated conditions, models of tidally locked, short-period planets (both hot Jupiters and terrestrial planets) tend to exhibit a circulation dominated by a fast eastward, or 'superrotating', jet stream at the equator. When the radiative and advection timescales are comparable, this phenomenon can cause the hottest regions to be displaced eastward from the substellar point by tens of degrees longitude. Such an offset has been subsequently observed on HD 189733b, supporting the possibility of equatorial jets on short-period exoplanets. Despite its relevance, however, the dynamical mechanisms responsible for generating the equatorial superrotation in such models have not been identified. Here, we show that the equatorial jet results from the interaction of the mean flow with standing Rossby waves induced by the day-night thermal forcing. The strong longitudinal variations in radiative heating-namely intense dayside heating and nightside cooling-trigger the formation of standing, planetary-scale equatorial Rossby and Kelvin waves. The Rossby waves develop phase tilts that pump eastward momentum from high latitudes to the equator, thereby inducing equatorial superrotation. We present an analytic theory demonstrating this mechanism and explore its properties in a hierarchy of one-layer (shallow-water) calculations and fully 3D models. The wave-mean-flow interaction produces an equatorial jet whose latitudinal width is comparable to that of the Rossby waves, namely the equatorial Rossby deformation radius modified by radiative and frictional effects. For conditions typical of synchronously rotating hot Jupiters, this length is comparable to a planetary radius, explaining the broad scale of the equatorial jet obtained in most hot-Jupiter models. Our theory illuminates the dependence of the equatorial jet speed on forcing amplitude, strength of friction, and other parameters, as well as the conditions under which jets can form at all.

  14. Statistical equilibrium of bubble oscillations in dilute bubbly flows

    PubMed Central

    Colonius, Tim; Hagmeijer, Rob; Ando, Keita; Brennen, Christopher E.

    2008-01-01

    The problem of predicting the moments of the distribution of bubble radius in bubbly flows is considered. The particular case where bubble oscillations occur due to a rapid (impulsive or step change) change in pressure is analyzed, and it is mathematically shown that in this case, inviscid bubble oscillations reach a stationary statistical equilibrium, whereby phase cancellations among bubbles with different sizes lead to time-invariant values of the statistics. It is also shown that at statistical equilibrium, moments of the bubble radius may be computed using the period-averaged bubble radius in place of the instantaneous one. For sufficiently broad distributions of bubble equilibrium (or initial) radius, it is demonstrated that bubble statistics reach equilibrium on a time scale that is fast compared to physical damping of bubble oscillations due to viscosity, heat transfer, and liquid compressibility. The period-averaged bubble radius may then be used to predict the slow changes in the moments caused by the damping. A benefit is that period averaging gives a much smoother integrand, and accurate statistics can be obtained by tracking as few as five bubbles from the broad distribution. The period-averaged formula may therefore prove useful in reducing computational effort in models of dilute bubbly flow wherein bubbles are forced by shock waves or other rapid pressure changes, for which, at present, the strong effects caused by a distribution in bubble size can only be accurately predicted by tracking thousands of bubbles. Some challenges associated with extending the results to more general (nonimpulsive) forcing and strong two-way coupled bubbly flows are briefly discussed. PMID:19547725

  15. Statistical equilibrium of bubble oscillations in dilute bubbly flows.

    PubMed

    Colonius, Tim; Hagmeijer, Rob; Ando, Keita; Brennen, Christopher E

    2008-04-01

    The problem of predicting the moments of the distribution of bubble radius in bubbly flows is considered. The particular case where bubble oscillations occur due to a rapid (impulsive or step change) change in pressure is analyzed, and it is mathematically shown that in this case, inviscid bubble oscillations reach a stationary statistical equilibrium, whereby phase cancellations among bubbles with different sizes lead to time-invariant values of the statistics. It is also shown that at statistical equilibrium, moments of the bubble radius may be computed using the period-averaged bubble radius in place of the instantaneous one. For sufficiently broad distributions of bubble equilibrium (or initial) radius, it is demonstrated that bubble statistics reach equilibrium on a time scale that is fast compared to physical damping of bubble oscillations due to viscosity, heat transfer, and liquid compressibility. The period-averaged bubble radius may then be used to predict the slow changes in the moments caused by the damping. A benefit is that period averaging gives a much smoother integrand, and accurate statistics can be obtained by tracking as few as five bubbles from the broad distribution. The period-averaged formula may therefore prove useful in reducing computational effort in models of dilute bubbly flow wherein bubbles are forced by shock waves or other rapid pressure changes, for which, at present, the strong effects caused by a distribution in bubble size can only be accurately predicted by tracking thousands of bubbles. Some challenges associated with extending the results to more general (nonimpulsive) forcing and strong two-way coupled bubbly flows are briefly discussed. PMID:19547725

  16. Colliding with a crunching bubble

    SciTech Connect

    Freivogel, Ben; Freivogel, Ben; Horowitz, Gary T.; Shenker, Stephen

    2007-03-26

    In the context of eternal inflation we discuss the fate of Lambda = 0 bubbles when they collide with Lambda< 0 crunching bubbles. When the Lambda = 0 bubble is supersymmetric, it is not completely destroyed by collisions. If the domain wall separating the bubbles has higher tension than the BPS bound, it is expelled from the Lambda = 0 bubble and does not alter its long time behavior. If the domain wall saturates the BPS bound, then it stays inside the Lambda = 0 bubble and removes a finite fraction of future infinity. In this case, the crunch singularity is hidden behind the horizon of a stable hyperbolic black hole.

  17. Study of electron trapping by a transversely ellipsoidal bubble in the laser wake-field acceleration

    SciTech Connect

    Cho, Myung-Hoon [School of Natural Science, UNIST, BanYeon-Ri 100, Ulju-gun, Ulsan 689-798 (Korea, Republic of)] [School of Natural Science, UNIST, BanYeon-Ri 100, Ulju-gun, Ulsan 689-798 (Korea, Republic of); Kim, Young-Kuk; Hur, Min Sup [School of Electrical and Computer Engineering, UNIST, BanYeon-Ri 100, Ulju-gun, Ulsan 689-798 (Korea, Republic of)] [School of Electrical and Computer Engineering, UNIST, BanYeon-Ri 100, Ulju-gun, Ulsan 689-798 (Korea, Republic of)

    2013-09-15

    We present electron trapping in an ellipsoidal bubble which is not well explained by the spherical bubble model by [Kostyukov et al., Phys. Rev. Lett. 103, 175003 (2009)]. The formation of an ellipsoidal bubble, which is elongated transversely, frequently occurs when the spot size of the laser pulse is large compared to the plasma wavelength. First, we introduce the relation between the bubble size and the field slope inside the bubble in longitudinal and transverse directions. Then, we provide an ellipsoidal model of the bubble potential and investigate the electron trapping condition by numerical integration of the equations of motion. We found that the ellipsoidal model gives a significantly less restrictive trapping condition than that of the spherical bubble model. The trapping condition is compared with three-dimensional particle-in-cell simulations and the electron trajectory in test potential simulations.

  18. A UBVRI equatorial extinction star network

    NASA Technical Reports Server (NTRS)

    Barnes, T. G., III; Moffett, T. J.

    1979-01-01

    An equatorial-extinction star network, based on 1503 observations of 37 stars, is presented. These results together with those of Crawford et al. (1971) provide a well-determined UBVRI extinction network. Identification charts are included.

  19. Longitudinal variations of the equatorial electojet

    NASA Astrophysics Data System (ADS)

    Shume, Esayas

    We have utilized a three dimensional electrostatic potential model to explain the longitudinal variations of the equatorial electrojet. The model runs were constrained by net H component magnetic field measurements from three equatorial stations, namely, Huancayo (Peru) 12.05 S, 284.67 E; Addis Ababa (Ethiopia) 9.8 N, 38.8 E; Tirunelveli (India) 8.42 N, 77.48 E. The model runs were done in an iterative fashion until the computed and measured H component magnetic field values come into a close agreement. The physical mechanisms for the longitudinal variations of the equatorial electrojet were inferred by comparing and contrasting the resulting computed vertical polarization electric field (which drives the equatorial electrojet), and zonal current density profiles for the three stations mentioned above.

  20. Recurring Slope Lineae (RSL) in Equatorial Mars

    NASA Astrophysics Data System (ADS)

    McEwen, A. S.; Dundas, C.; Mattson, S.; Toigo, A.; Ojha, L.; Murchie, S.; Thomas, N.; Wray, J.; Byrne, S.; Chojnacki, M.

    2013-09-01

    Here we report on RSL (possible water seeps) in equatorial regions of Mars, especially in the deep canyons of Valles Marineris (VM). They are active on north-facing slopes in northern spring and summer and on south-facing slopes in southern spring and summer, following the peak solar warming of these steep slopes. This equatorial activity places new constraints on the origin of RSL and has implications for future exploration.

  1. Vertical shear in the Jovian equatorial zone.

    NASA Technical Reports Server (NTRS)

    Layton, R. G.

    1971-01-01

    Jupiter photographs taken in two different wavelength regions (blue and red) are studied for clues to differing Jovian atmosphere motions. The relative motions of features visible on these photographs may be interpreted as a vertical shear at visible cloud level. The value obtained implies that the north equatorial zone must be about 0.35 deg K warmer than the adjacent equatorial zone. Deeper in the atmosphere the reverse must hold.

  2. Effect of direct bubble-bubble interactions on linear-wave propagation in bubbly liquids

    NASA Astrophysics Data System (ADS)

    Fuster, D.; Conoir, J. M.; Colonius, T.

    2014-12-01

    We study the influence of bubble-bubble interactions on the propagation of linear acoustic waves in bubbly liquids. Using the full model proposed by Fuster and Colonius [J. Fluid Mech. 688, 253 (2011), 10.1017/jfm.2011.380], numerical simulations reveal that direct bubble-bubble interactions have an appreciable effect for frequencies above the natural resonance frequency of the average size bubble. Based on the new results, a modification of the classical wave propagation theory is proposed. The results obtained are in good agreement with previously reported experimental data where the classical linear theory systematically overpredicts the effective attenuation and phase velocity.

  3. Effect of bubble deformation on the properties of bubbly flows

    NASA Astrophysics Data System (ADS)

    Bunner, Bernard; Tryggvason, Grétar

    2003-11-01

    Direct numerical simulations of the motion of 27 three-dimensional deformable buoyant bubbles in periodic domains are presented. The full Navier Stokes equations are solved by a parallelized finite-difference/front-tracking method that allows a deformable interface between the bubbles and the suspending fluid and the inclusion of surface tension. The Eötvös number is taken as equal to 5, so that the bubbles are ellipsoidal, and the Galileo number is 900, so that the rise Reynolds number of a single bubble in an unbounded flow is about 26. Three values of the void fraction have been investigated: 2%, 6% and 12%. At 6%, a change in the behaviour of the bubbles is observed. The bubbles are initially dispersed homogeneously throughout the flow field and their average rise Reynolds number is 23. After the bubbles have risen by about 90 bubble diameters, they form a vertical stream and accelerate. The microstructure of the bubble suspension is analysed and an explanation is proposed for the formation of these streams. The results for the ellipsoidal bubbles are compared to the results for nearly spherical bubbles, for which the Eötvös number is 1 and the Galileo number is 900. The dispersion of the bubbles and the velocity fluctuations in the liquid phase are analysed.

  4. The Fermi Bubbles

    NASA Astrophysics Data System (ADS)

    Finkbeiner, Douglas P.

    2015-01-01

    The Fermi Bubbles are a pair of giant lobes at the heart of the Milky Way, extending roughly 50 degrees north and south of the Galactic Center, and emitting photons with energies up to 100 GeV. This previously unknown structure could be evidence for past activity of the central supermassive black hole, or enhanced star formation towards the inner Galaxy. We will describe the path to discovery of the Bubbles in multiwavelength data, from the first hints in microwave radiation measured by WMAP and X-rays from ROSAT, to the unveiling of their shape and spectrum using public gamma-ray data from the Fermi Gamma-ray Space Telescope, to more recent measurements by Planck and XMM-Newton. We will outline the current state of knowledge of the Bubbles' spectrum, morphology and internal structure, and discuss theoretical proposals and numerical simulations for their nature and origin.

  5. Fluid Dynamics of Bubbly Liquids

    NASA Technical Reports Server (NTRS)

    Tsang, Y. H.; Koch, D. L.; Zenit, R.; Sangani, A.; Kushch, V. I.; Spelt, P. D. M.; Hoffman, M.; Nahra, H.; Fritz, C.; Dolesh, R.

    2002-01-01

    Experiments have been performed to study the average flow properties of inertially dominated bubbly liquids which may be described by a novel analysis. Bubbles with high Reynolds number and low Weber number may produce a fluid velocity disturbance that can be approximated by a potential flow. We studied the behavior of suspensions of bubbles of about 1.5 mm diameter in vertical and inclined channels. The suspension was produced using a bank of 900 glass capillaries with inner diameter of about 100 microns in a quasi-steady fashion. In addition, salt was added to the suspension to prevent bubble-bubble coalescence. As a result, a nearly monodisperse suspension of bubble was produced. By increasing the inclination angle, we were able to explore an increasing amount of shear to buoyancy motion. A pipe flow experiment with the liquid being recirculated is under construction. This will provide an even larger range of shear to buoyancy motion. We are planning a microgravity experiment in which a bubble suspension is subjected to shearing in a couette cell in the absence of a buoyancy-driven relative motion of the two phases. By employing a single-wire, hot film anemometer, we were able to obtain the liquid velocity fluctuations. The shear stress at the wall was measured using a hot film probe flush mounted on the wall. The gas volume fraction, bubble velocity, and bubble velocity fluctuations were measured using a homemade, dual impedance probe. In addition, we also employed a high-speed camera to obtain the bubble size distribution and bubble shape in a dilute suspension. A rapid decrease in bubble velocity for a dilute bubble suspension is attributed to the effects of bubble-wall collisions. The more gradual decrease of bubble velocity as gas volume fraction increases, due to subsequent hindering of bubble motion, is in qualitative agreement with the predictions of Spelt and Sangani for the effects of potential-flow bubble-bubble interactions on the mean velocity. The ratio of the bubble velocity variance to the square of the mean is 0(0.1). For these conditions Spelt and Sangani predicted that the homogeneous suspension would be unstable and clustering into horizontal rafts will take place. Evidence for bubble clustering is obtained by analysis of video images. The liquid velocity variance is larger than would be expected for a homogeneous suspension and the liquid velocity frequency spectrum indicates the presence of velocity fluctuations that are slow compared with the time for the passage of an individual bubble. These observations provide further evidence for bubble clustering.

  6. Bubbles and Biosensors

    NSDL National Science Digital Library

    2014-09-18

    Students work in groups to create soap bubbles on a smooth surface, recording their observations from which they formulate theories to explain what they see (color swirls on the bubble surfaces caused by refraction). Then they apply this theory to thin films in general, including porous films used in biosensors, listing factors that could change the color(s) that become visible to the naked eye, and learn how those factors can be manipulated to give information on gene detection. Finally (by experimentation or video), students see what happens when water is dropped onto the surface of a Bragg mirror.

  7. Inertial confinement fusion based on the ion-bubble trigger

    SciTech Connect

    Jafari, S., E-mail: SJafari@guilan.ac.ir; Nilkar, M.; Ghasemizad, A. [Department of Physics, University of Guilan, Rasht 41335-1914 (Iran, Islamic Republic of); Mehdian, H. [Department of Physics and Institute for Plasma Research, Tarbiat Moallem University, Tehran 15614 (Iran, Islamic Republic of)

    2014-10-15

    Triggering the ion-bubble in an inertial confinement fusion, we have developed a novel scheme for the fast ignition. This scheme relies on the plasma cavitation by the wake of an intense laser pulse to generate an ion-bubble. The bubble acts both as an intense electron accelerator and as an electron wiggler. Consequently, the accelerated electrons trapped in the bubble can emit an intense tunable laser light. This light can be absorbed by an ablation layer on the outside surface of the ignition capsule, which subsequently drills it and thereby produces a guide channel in the pellet. Finally, the relativistic electron beam created in the bubble is guided through the channel to the high density core igniting the fusion fuel. The normalized beam intensity and beam energy required for triggering the ignition have been calculated when core is heated by the e-beam. In addition, through solving the momentum transfer, continuity and wave equations, a dispersion relation for the electromagnetic and space-charge waves has been analytically derived. The variations of growth rate with the ion-bubble density and electron beam energy have been illustrated. It is found that the growth rates of instability are significantly controlled by the ions concentration and the e-beam energy in the bubble.

  8. Mixture Segregation within Sonoluminescence Bubbles

    Microsoft Academic Search

    Brian D. Storey; Andrew J. Szeri

    1999-01-01

    This paper concerns a relaxation of the assumption of uniform mixture composition in the interior of sonoluminescence bubbles. Intense temperature and pressure gradients within the bubble drive relative mass diffusion which overwhelms diffusion driven by concentration gradients. This thermal and pressure diffusion results in a robust compositional inhomogeneity in the bubble which lasts several orders of magnitude longer than the

  9. Bubble shape instability and sonoluminescence

    Microsoft Academic Search

    C. C. Wu; P. H. Roberts

    1998-01-01

    Light from a sonoluminescing bubble is extinguished if the amplitude of the acoustic field that drives the bubble oscillation exceeds a certain threshold. It has been suggested that shape instability of the bubble surface is responsible. The effect of viscosity on such an instability is examined here.

  10. Sonoluminescing Air Bubbles Rectify Argon

    Microsoft Academic Search

    Detlef Lohse; Michael P. Brenner; Todd F. Dupont; Sascha Hilgenfeldt; Blaine Johnston

    1997-01-01

    The dynamics of single bubble sonoluminescence (SBSL) strongly depends on the percentage of inert gas within the bubble. We propose a theory for this dependence, based on a combination of principles from sonochemistry and hydrodynamic stability. The nitrogen and oxygen dissociation and subsequent reaction to water soluble gases implies that strongly forced air bubbles eventually consist of pure argon. Thus

  11. Using Bubbles to Explore Membranes

    NSDL National Science Digital Library

    Sandra Wardell

    2009-01-01

    In this activity, learners use bubbles to investigate the structure and unique properties of cell membranes. Bubbles serve as macroscopic models that mimic the cells' phospholipid bilayers. Learners also use the bubbles to form prokaryotic cells and eukaryotic cells. This inquiry type lab can be done as a group or cooperative learning experience. Materials listed are designed for a group of 30 learners.

  12. Latitudinal comparisons of equatorial Pacific zooplankton

    NASA Astrophysics Data System (ADS)

    Roman, M. R.; Dam, H. G.; Le Borgne, R.; Zhang, X.

    Zooplankton biomass and rates of ingestion, egestion and production in the equatorial Pacific Ocean along 140°W and 180° exhibit maximum values in the High-Nutrient Low-Chlorophyll (HNLC) zone associated with equatorial upwelling (5°S-5°N) as compared to the more oligotrophic regions to the north and south. Zooplankton biomass and rates are not usually highest on the equator, but increase "downstream" of the upwelling center as the zooplankton populations exhibit a delayed response to enhanced phytoplankton production. The vertical distribution of zooplankton biomass in the equatorial HNLC area tends to be concentrated in surface waters and is more uniform with depth in oligotrophic regions to the north and south of the equatorial upwelling zone. In general, the amount of mesozooplankton (>200 ?m) carbon biomass is approximately 25% of estimated phytoplankton biomass and 30% of bacterial biomass in the HNLC area of the equatorial Pacific Ocean. Zooplankton grazing on phytoplankton is low in the equatorial Pacific Ocean, generally <5% of the total chlorophyll-a standing stock grazed per day. Based on estimates of metabolic demand, it is apparent that zooplankton in the equatorial Pacific Ocean are omnivores, consuming primarily microzooplankton and detritus. Estimated zooplankton growth rates in the warm waters of the HNLC equatorial Pacific Ocean are high, ranging from 0.58 d -1 for 64-200 ?m zooplankton to 0.08 d -1 for 1000-2000 ?m zooplankton. Thus, the numerical and functional response of equatorial zooplankton to increases in phytoplankton production are more rapid than normally occurs in sub-tropical and temperate waters. Potential zooplankton fecal pellet production, estimated from metabolic demand, is approximately 1.6 times the estimated gravitational carbon flux at 150 m in the zone of equatorial upwelling (5°S-5°N) and 1.1 times the export flux in the more oligotrophic regions to the north and south. The active flux of carbon by diel migrant zooplankton in the HNLC zone is a minor fraction of the gravitational flux (2% at 140°W, 4% at 180°) but increases in the more oligotrophic regions to the north and south where there is a deeper mixed layer and a greater relative proportion of diel migrant zooplankton.

  13. Stability of magnetic equilibria in radio bubbles

    NASA Astrophysics Data System (ADS)

    Benford, Gregory

    2006-06-01

    Current-carrying flows, in the laboratory and in astrophysical jets, can form remarkably stable magnetic structures. Decades of experience show that such flows often build equilibria that reverse field directions, evolving to a magnetohydrodynamic (MHD) Taylor state, which has remarkable stability properties. We model jets and the magnetic bubbles they build as reversed-field pinch equilibria by assuming the driver current to be stiff in the MHD sense. Taking the jet current as rigid and a fixed function of position, we prove a theorem: that the same, simple MHD stability conditions guarantee stability, even after the jet turns off. This means that magnetic structures harbouring a massive inventory of magnetic energy can persist long after the building jet current has died away. These may be the relic radio `fossils', `ghost bubbles' or `magnetic balloons' found in clusters. These equilibria, which are under magnetic tension, will evolve, retaining the stability properties from that state. The remaining fossil is not a disordered ball of magnetic fields, but a stable structure under tension, able to respond to the slings and arrows of outside forces. Typically their Alfvén speeds greatly exceed the cluster sound speed, and so they can keep out hot cluster plasma, leading to X-ray ghosts. Passing shocks cannot easily destroy them, but can energize and light them up anew at radio frequencies. Bubbles can rise in the hot cluster plasma, perhaps detaching from the parent radio galaxy but stable against Rayleigh-Taylor and other modes.

  14. Supersonic electroweak baryogenesis: achieving baryogenesis for fast bubble walls

    SciTech Connect

    Caprini, Chiara; No, José M., E-mail: chiara.caprini@cea.fr, E-mail: jose-miguel.no@cea.fr [IPhT and CNRS URA 2306, CEA-Saclay, F-91191 Gif-sur-Yvette (France)

    2012-01-01

    Standard electroweak baryogenesis in the context of a first order phase transition is effective in generating the baryon asymmetry of the universe if the broken phase bubbles expand at subsonic speed, so that CP asymmetric currents can diffuse in front of the wall. Here we present a new mechanism for electroweak baryogenesis which operates for supersonic bubble walls. It relies on the formation of small bubbles of the symmetric phase behind the bubble wall, in the broken phase, due to the heating of the plasma as the wall passes by. We apply the mechanism to a model in which the Higgs field is coupled to several singlets, and find that enough baryon asymmetry is generated for reasonable values of the parameter space.

  15. Solar Cycle Effects on Equatorial Electrojet Strength and Low Latitude Ionospheric Variability (P10)

    NASA Astrophysics Data System (ADS)

    Veenadhari, B.; Alex, S.

    2006-11-01

    veena_iig@yahoo.co.in The most obvious indicators of the activity of a solar cycle are sunspots, flares, plages, and soon. These are intimately linked to the solar magnetic fields, heliospheric processes which exhibit complex but systematic variations. The changes in geomagnetic activity, as observed in the ground magnetic records follow systematic correspondence with the solar activity conditions. Thus the transient variations in the magnetic field get modified by differing solar conditions. Also the solar cycle influences the Earth causing changes in geomagnetic activity, the magnetosphere and the ionosphere. Daily variations in the ground magnetic field are produced by different current systems in the earth’s space environment flowing in the ionosphere and magnetosphere which has a strong dependence on latitude and longitude of the location. The north-south (Horizontal) configuration of the earth’s magnetic field over the equator is responsible for the narrow band of current system over the equatorial latitudes and is called the Equatorial electrojet (EEJ) and is a primary driver for Equatorial Ionization anomaly (EIA). Equatorial electric fields and plasma drifts play the fundamental roles on the morphology of the low latitude ionosphere and strongly vary during geomagnetically quiet and disturbed periods. Quantitative study is done to illustrate the development process of EEJ and its influence on ionospheric parameters. An attempt is also made to examine and discuss the response of the equatorial electrojet parameters to the fast varying conditions of solar wind and interplanetary parameters.

  16. Seismo-ionospheric coupling appearing as equatorial electron density enhancements observed via DEMETER electron density measurements

    NASA Astrophysics Data System (ADS)

    Ryu, K.; Lee, E.; Chae, J. S.; Parrot, M.; Pulinets, S.

    2014-10-01

    We report the processes and results of statistical analysis on the ionospheric electron density data measured by the Detection of Electro-Magnetic Emissions Transmitted from Earthquake Regions (DEMETER) satellite over a period of 6 years (2005-2010), in order to investigate the correlation between seismic activity and equatorial plasma density variations. To simplify the analysis, three equatorial regions with frequent earthquakes were selected and then one-dimensional time series analysis between the daily seismic activity indices and the equatorial ionization anomaly (EIA) intensity indices, which represent relative equatorial electron density increase, were performed for each region. The statistically significant values of the lagged cross-correlation function, particularly in the region with minimal effects of longitudinal asymmetry, indicate that some of the very large earthquakes with M > 5.0 in the low-latitude region can accompany observable precursory and concurrent EIA enhancements, even though the seismic activity is not the most significant driver of the equatorial ionospheric evolution. The physical mechanisms of the seismo-ionospheric coupling is consistent with our observation, and the possibility of earthquake prediction using the EIA intensity variation is discussed.

  17. Climatic trends of the equatorial undercurrent: A backup mechanism for sustaining the equatorial Pacific production

    E-print Network

    Paparella, Francesco

    in the high-nutrient low-chlorophyll region of the equatorial Pacific compatibly with the significant increase). The area of upwell- ing in the eastern equatorial Pacific is a high nutrient low chlorophyll region where on a Lagrangian approach aimed at understanding the changes in the transport of iron rich waters to the EUC

  18. Bubble fusion: Preliminary estimates

    SciTech Connect

    Krakowski, R.A.

    1995-02-01

    The collapse of a gas-filled bubble in disequilibrium (i.e., internal pressure {much_lt} external pressure) can occur with a significant focusing of energy onto the entrapped gas in the form of pressure-volume work and/or acoustical shocks; the resulting heating can be sufficient to cause ionization and the emission of atomic radiations. The suggestion that extreme conditions necessary for thermonuclear fusion to occur may be possible has been examined parametrically in terms of the ratio of initial bubble pressure relative to that required for equilibrium. In this sense, the disequilibrium bubble is viewed as a three-dimensional ``sling shot`` that is ``loaded`` to an extent allowed by the maximum level of disequilibrium that can stably be achieved. Values of this disequilibrium ratio in the range 10{sup {minus}5}--10{sup {minus}6} are predicted by an idealized bubble-dynamics model as necessary to achieve conditions where nuclear fusion of deuterium-tritium might be observed. Harmonic and aharmonic pressurizations/decompressions are examined as means to achieve the required levels of disequilibrium required to create fusion conditions. A number of phenomena not included in the analysis reported herein could enhance or reduce the small levels of nuclear fusions predicted.

  19. The Liberal Arts Bubble

    ERIC Educational Resources Information Center

    Agresto, John

    2011-01-01

    The author expresses his doubt that the general higher education bubble will burst anytime soon. Although tuition, student housing, and book costs have all increased substantially, he believes it is still likely that the federal government will continue to pour billions into higher education, largely because Americans have been persuaded that it…

  20. What's in the Bubbles?

    NSDL National Science Digital Library

    Francis Eberle

    2007-01-01

    The purpose of this assessment probe is to elicit students' ideas about particles during a change in state. The probe is designed to find out if students recognize that the bubbles formed when water boils are the result of liquid water changing into water vapor. This free selection also includes the Table of Contents, Foreword, Preface, and Index.

  1. Overconfidence and Speculative Bubbles

    Microsoft Academic Search

    Jose A. Scheinkman; Wei Xiong

    2003-01-01

    Motivated by the behavior of asset prices, trading volume, and price volatility during episodes of asset price bubbles, we present a continuous-time equilibrium model in which overconfidence generates disagreements among agents regarding asset fundamentals. With short-sale constraints, an asset buyer acquires an option to sell the asset to other agents when those agents have more optimistic beliefs. As in a

  2. Bubble Rings Entrapment

    E-print Network

    Thoraval, Marie-Jean; Takehara, Kohsei; Etoh, Takeharu Goji

    2012-01-01

    We show how micro-bubble rings are entrapped under a drop impacting onto a pool surface. This fluid dynamics video is submitted to the APS DFD Gallery of Fluid Motion 2012, part of the 65th Annual Meeting of the American Physical Society's Division of Fluid Dynamics (18-20 November, San Diego, CA, USA).

  3. Bubbly Little Star

    NASA Technical Reports Server (NTRS)

    2007-01-01

    In this processed Spitzer Space Telescope image, baby star HH 46/47 can be seen blowing two massive 'bubbles.' The star is 1,140 light-years away from Earth.

    The infant star can be seen as a white spot toward the center of the Spitzer image. The two bubbles are shown as hollow elliptical shells of bluish-green material extending from the star. Wisps of green in the image reveal warm molecular hydrogen gas, while the bluish tints are formed by starlight scattered by surrounding dust.

    These bubbles formed when powerful jets of gas, traveling at 200 to 300 kilometers per second, or about 120 to 190 miles per second, smashed into the cosmic cloud of gas and dust that surrounds HH 46/47. The red specks at the end of each bubble show the presence of hot sulfur and iron gas where the star's narrow jets are currently crashing head-on into the cosmic cloud's gas and dust material.

    Whenever astronomers observe a star, or snap a stellar portrait, through the lens of any telescope, they know that what they are seeing is slightly blurred. To clear up the blurring in Spitzer images, astronomers at the Jet Propulsion Laboratory developed an image processing technique for Spitzer called Hi-Res deconvolution.

    This process reduces blurring and makes the image sharper and cleaner, enabling astronomers to see the emissions around forming stars in greater detail. When scientists applied this image processing technique to the Spitzer image of HH 46/47, they were able to see winds from the star and jets of gas that are carving the celestial bubbles.

    This infrared image is a three-color composite, with data at 3.6 microns represented in blue, 4.5 and 5.8 microns shown in green, and 24 microns represented as red.

  4. Simulations of the equatorial thermosphere anomaly: Geomagnetic activity modulation

    NASA Astrophysics Data System (ADS)

    Lei, Jiuhou; Wang, Wenbin; Thayer, Jeffrey P.; Luan, Xiaoli; Dou, Xiankang; Burns, Alan G.; Solomon, Stanley C.

    2014-08-01

    The modulation of geomagnetic activity on the equatorial thermosphere anomaly (ETA) in thermospheric temperature under the high solar activity condition is investigated using the Thermosphere Ionosphere Electrodynamics General Circulation Model simulations. The model simulations during the geomagnetically disturbed interval, when the north-south component of the interplanetary magnetic field (Bz) oscillates between southward and northward directions, are analyzed and also compared with those under the quiet time condition. Our results show that ionospheric electron densities increase greatly in the equatorial ionization anomaly (EIA) crest region and decrease around the magnetic equator during the storm time, resulting from the enhanced eastward electric fields. The impact of both the direct heat deposition at high latitudes and the modulation of the storm time enhanced EIA crests on the ETA are subsequently studied. The increased plasma densities over the EIA crest region enhance the field-aligned ion drag that accelerates the poleward meridional winds and consequently their associated adiabatic cooling effect. This process alone produces a deeper temperature trough over the magnetic equator as a result of the enhanced divergence of meridional winds. Moreover, the enhanced plasma-neutral collisional heating at higher latitudes associated with the ionospheric positive storm effect causes a weak increase of the ETA crests. On the other hand, strong changes of the neutral temperature are mainly confined to higher latitudes. Nevertheless, the changes of the ETA purely due to the increased plasma density are overwhelmed by those associated with the storm time heat deposition, which is the major cause of an overall elevated temperature in both the ETA crests and trough during the geomagnetically active period. Associated with the enhanced neutral temperature at high latitudes due to the heat deposition, the ETA crest-trough differences become larger under the minor geomagnetic activity condition than under the quiet time condition. However, when geomagnetic activity is further elevated, the ETA crests tend to be masked by high temperatures at middle and high latitudes.

  5. Computed spectral and temporal emissions from a sonoluminescing bubble

    SciTech Connect

    Moss, W. C., LLNL

    1998-02-09

    A sonoluminescing bubble has been modeled as a thermally conducting, partially ionized, two-component radiating plasma. The recent measurements of {approximately} 100ps pulse widths by Gompf et al. are useful for constructing a consistent plasma thermal conduction model that refines our previous model. Normal thermal conduction in the gas and liquid, vapor pressure, and temperature-dependent surface tension are also included in our nonlinear hydrodynamic simulations of the growth and collapse of a gas bubble and the liquid that surrounds it. We validate the model by comparing our simulations with the experimental data of Gaitan and Holt [R{sub 0}, R{sub max}, and intensity, for different driving pressures]. We also calculate the 2D collapse of a sonoluminescing bubble in a uniform magnetic field. The numerical results show that the magnetic field induces an aspherical collapse that reduces the peak temperature in the gas and quenches SBSL. The calculated quenching is consistent with experimental data.

  6. Fermi gamma-ray "bubbles" from stochastic acceleration of electrons.

    PubMed

    Mertsch, Philipp; Sarkar, Subir

    2011-08-26

    Gamma-ray data from Fermi Large Area Telescope reveal a bilobular structure extending up to ?50° above and below the Galactic Center. It has been argued that the gamma rays arise from hadronic interactions of high-energy cosmic rays which are advected out by a strong wind, or from inverse-Compton scattering of relativistic electrons accelerated at plasma shocks present in the bubbles. We explore the alternative possibility that the relativistic electrons are undergoing stochastic 2nd-order Fermi acceleration by plasma wave turbulence through the entire volume of the bubbles. The observed gamma-ray spectral shape is then explained naturally by the resulting hard electron spectrum modulated by inverse-Compton energy losses. Rather than a constant volume emissivity as in other models, we predict a nearly constant surface brightness, and reproduce the observed sharp edges of the bubbles. PMID:21929220

  7. Ring Bubbles of Dolphins

    NASA Technical Reports Server (NTRS)

    Shariff, Karim; Marten, Ken; Psarakos, Suchi; White, Don J.; Merriam, Marshal (Technical Monitor)

    1996-01-01

    The article discusses how dolphins create and play with three types of air-filled vortices. The underlying physics is discussed. Photographs and sketches illustrating the dolphin's actions and physics are presented. The dolphins engage in this behavior on their own initiative without food reward. These behaviors are done repeatedly and with singleminded effort. The first type is the ejection of bubbles which, after some practice on the part of the dolphin, turn into toroidal vortex ring bubbles by the mechanism of baroclinic torque. These bubbles grow in radius and become thinner as they rise vertically to the surface. One dolphin would blow two in succession and guide them to fuse into one. Physicists call this a vortex reconnection. In the second type, the dolphins first create an invisible vortex ring in the water by swimming on their side and waving their tail fin (also called flukes) vigorously. This vortex ring travels horizontally in the water. The dolphin then turns around, finds the vortex and injects a stream of air into it from its blowhole. The air "fills-out" the core of the vortex ring. Often, the dolphin would knock-off a smaller ring bubble from the larger ring (this also involves vortex reconnection) and steer the smaller ring around the tank. One other dolphin employed a few other techniques for planting air into the fluke vortex. One technique included standing vertically in the water with tail-up, head-down and tail piercing the free surface. As the fluke is waved to create the vortex ring, air is entrained from above the surface. Another technique was gulping air in the mouth, diving down, releasing air bubbles from the mouth and curling them into a ring when they rose to the level of the fluke. In the third type, demonstrated by only one dolphin, the longitudinal vortex created by the dorsal fin on the back is used to produce 10-15 foot long helical bubbles. In one technique she swims in a curved path. This creates a dorsal fin vortex since centrifugal force has to be balanced by a lift-like force. She then re-traces her path and injects air into the vortex from her blowhole. She can even make a ring reconnect from the helix. In the second technique, demonstrated a few times, she again swims in a curved path, releases a cloud or group of bubbles from her blowhole and turns sharply away (Which presumably strengthens the vortex). As the bubbles encounter the vortex, they travel to the center of the vortex, merge and, in a flash, elongate along the core of the vortex. In all the three types, the air-water interface is shiny smooth and stable because the pressure gradient in the vortex flow around the bubble stabilizes it. A lot of the interesting physics still remains to be explored.

  8. Relation Between Ionospheric Plasma Irregularities at High Latitudes and Auroral Phenomena

    NASA Astrophysics Data System (ADS)

    Ritter, P.; Park, J.; Luhr, H.

    2012-12-01

    Ionospheric irregularities at low-latitudes, known as equatorial plasma bubbles, tend to occur preferably at post-sunset hours when the vertical plasma velocity during the pre-reversal enhancement is particularly strong. Recently, significant occurrence rates of plasma irregularities have also been reported in the high-latitude regions. Their generation mechanisms are quite different and at present still not fully understood. As these irregularities tend to cluster in three prominent regions of the polar area - cusp, polar cap, and pre-midnight substorm onset sector - we investigate their characteristics for these regions separately. One suggestion for high-latitude irregularity generation is ionisation by soft electron precipitations. These beams of soft electrons are commonly accompanied by bursts of small-scale field-aligned currents (FAC). In a superposed epoch analysis we investigate the relation between the occurrences of plasma irregularities and collocated small-scale FACs. In the cusp, a clear coincidence of the two phenomena is observed. Conversely, in the polar cap small-scale FACs are not so frequent. Therefore we suggest a transport of the irregularities from the cusp region into the polar cap by the general anti-sunward plasma convection pattern. In order to discuss possible relations between plasma irregularities detected in the pre-midnight sector and substorm phases we also compare the event times with the substorm catalogue of Frey and Mende (2006).

  9. Multiscale equatorial electrojet turbulence:Baseline 2-D model

    NASA Astrophysics Data System (ADS)

    Hassan, Ehab; Horton, W.; Smolyakov, A. I.; Hatch, D. R.; Litt, S. K.

    2015-02-01

    The spatial and spectral characteristics of the turbulent plasma density, electric fields, and ion drift in ionospheric E region are studied using a new set of nonlinear plasma fluid equations. The fluid model combines both Farley-Buneman (Type-I) and Gradient-Drift (Type-II) plasma instabilities in the equatorial electrojet. In our unified model of the plasma instabilities, we include the ion viscosity in the ion momentum equation and electron inertia in the electron momentum equation. These two terms play an important role in stabilizing the growing modes in the linear regime and in driving the Farley-Buneman instability into the saturation state. The simulation results show good agreements with a number of features of rocket and radar observations, such as (1) saturation of plasma density perturbations depends on the solar condition and reaches 7-15% relative to the background, (2) fluctuation of the horizontal secondary electric field reaches 8-15 mV/m, (3) stabilization of the phase velocity of the perturbed density wave around the value of the ion-acoustic speed inside the electrojet, (4) "up-down" asymmetry in the vertical fluxes of the plasma density, (5) "east-west" asymmetry of the plasma zonal drifts, and (6) generation of small scale of the order of meter scale lengths irregularities embedded in large-scale structures. Spectral analysis of the density fluctuations reveals the energy cascade due to the nonlinear coupling between structures of different scales. The break-up of the large-scale structures into small-scale structures explains the disappearance of Type-II echoes in the presence of Type-I instabilities.

  10. Plasma observations at the earth's magnetic equator

    NASA Technical Reports Server (NTRS)

    Olsen, R. C.; Shawhan, S. D.; Gallagher, D. L.; Chappell, C. R.; Green, J. L.

    1987-01-01

    New observations of particle and wave data from the magnetic equator from the DE 1 spacecraft are reported. The results demonstrate that the equatorial plasma population is predominantly hydrogen and that the enhanced ion fluxes observed at the equator occur without an increase in the total plasma density. Helium is occasionally found heated along with the protons, and forms about 10 percent of the equatorially trapped population at such times. The heated H(+) ions can be characterized by a bi-Maxwellian with kT(parallel) = 0.5-1.0 eV and kT = 5-50 eV, with a density of 10-100/cu cm. The total plasma density is relatively constant with latitude. First measurements of the equatorially trapped plasma and coincident UHR measurements show that the trapped plasma is found in conjunction with equatorial noise.

  11. Onset conditions of bubbles and blobs: A case study on 2 March 2009

    NASA Astrophysics Data System (ADS)

    Kil, H.; Choi, H.-S.; Heelis, R. A.; Paxton, L. J.; Coley, W. R.; Miller, E. S.

    2011-03-01

    The onset conditions for bubbles and blobs are investigated by analyzing the Communication/Navigation Outage Forecasting System satellite/Coupled Ion-Neutral Dynamics Investigation instrument data on 2 March 2009. A series of bubbles and blobs are detected in the longitude regions 180°-240°E and 240°-295°E, respectively. Bubbles are detected at low latitudes before midnight. Blobs are detected at 14°-25° magnetic latitude, between 2300 and 0500 LT in the altitude range of 400-480 km. The distinguishing feature in the longitude region where bubbles are detected is an enhancement in background plasma density with respect to that in the longitude region where bubbles are absent. Blobs are detected in a longitude region where fluctuations in the plasma density exist over a broad latitude range. The total ion density (and O+ density) and H+ density perturbations are in-phase at the locations of bubbles and out of phase at the locations of blobs. Bubbles are not detected in the longitude region where blobs are detected. The different characteristics of bubbles and blobs and their creation under different geophysical conditions indicate that creation of blobs need not be associated with bubbles.

  12. Assessing model representations of stratospheric equatorial waves

    NASA Astrophysics Data System (ADS)

    Schultz, Colin

    2014-07-01

    Some westward-propagating Rossby-gravity waves and eastward Kelvin waves can travel up through the atmosphere following their formation in the tropical troposphere. Once they reach the stratosphere, these waves dissipate, releasing their energy. Known as stratospheric equatorial waves, these Rossby-gravity and Kelvin waves are an important aspect driving the quasi-biennial oscillation (QBO), a roughly monthly reversal, in the direction of the equatorial stratospheric winds. Similar to other atmospheric systems, such as the El Niño-Southern Oscillation or the North Atlantic Oscillation, the phase of the QBO affects global weather patterns, particularly in North America and western Europe.

  13. Equatorial waves in the stratosphere of Uranus

    NASA Technical Reports Server (NTRS)

    Hinson, David P.; Magalhaes, Julio A.

    1991-01-01

    Analyses of radio occultation data from Voyager 2 have led to the discovery and characterization of an equatorial wave in the Uranus stratosphere. The observed quasi-periodic vertical atmospheric density variations are in close agreement with theoretical predictions for a wave that propagates vertically through the observed background structure of the stratosphere. Quantitative comparisons between measurements obtained at immersion and at emersion yielded constraints on the meridional and zonal structure of the wave; the fact that the two sets of measurements are correlated suggests a wave of planetary scale. Two equatorial wave models are proposed for the wave.

  14. Digital hf radar observations of equatorial spread-F

    SciTech Connect

    Argo, P.E.

    1984-01-01

    Modern digital ionosondes, with both direction finding and doppler capabilities can provide large scale pictures of the Spread-F irregularity regions. A morphological framework has been developed that allows interpretation of the hf radar data. A large scale irregularity structure is found to be nightward of the dusk terminator, stationary in the solar reference frame. As the plasma moves through this foehn-wall-like structure it descends, and irregularities may be generated. Localized upwellings, or bubbles, may be produced, and they drift with the background plasma. The spread-F irregularity region is found to be best characterized as a partly cloudy sky, due to the patchiness of the substructures. 13 references, 16 figures.

  15. Polarizing bubble collisions

    SciTech Connect

    Czech, Bart?omiej; Larjo, Klaus; Levi, Thomas S.; Sigurdson, Kris [Department of Physics and Astronomy, University of British Columbia, Vancouver, BC V6T 1Z1 (Canada); Kleban, Matthew, E-mail: czech@phas.ubc.ca, E-mail: mk161@nyu.edu, E-mail: larjo@phas.ubc.ca, E-mail: tslevi@phas.ubc.ca, E-mail: krs@phas.ubc.ca [CCPP, Department of Physics, New York University, New York, NY 10003 (United States)

    2010-12-01

    We predict the polarization of cosmic microwave background (CMB) photons that results from a cosmic bubble collision. The polarization is purely E-mode, symmetric around the axis pointing towards the collision bubble, and has several salient features in its radial dependence that can help distinguish it from a more conventional explanation for unusually cold or hot features in the CMB sky. The anomalous ''cold spot'' detected by the Wilkinson Microwave Anisotropy Probe (WMAP) satellite is a candidate for a feature produced by such a collision, and the Planck satellite and other proposed surveys will measure the polarization on it in the near future. The detection of such a collision would provide compelling evidence for the string theory landscape.

  16. Sonoluminescence, sonochemistry and bubble dynamics of single bubble cavitation

    NASA Astrophysics Data System (ADS)

    Hatanaka, Shin-ichi

    2012-09-01

    The amount of hydroxyl radicals produced from a single cavitation bubble was quantified by terephthalate dosimetry at various frequencies and pressure amplitudes, while the dynamics of the single bubble was observed by stroboscopic and light-scattering methods. Also, sonoluminescence (SL), sonochemiluminescence (SCL) of luminol, and sodium atom emission (Na*) in the cavitation field were observed. The amount of hydroxyl radicals per cycle as well as the intensity of SL was proportional to pressure amplitude at every frequency performed, and it decreased with increasing frequency. When the single bubble was dancing with a decrease in pressure amplitude, however, the amount of hydroxyl radicals was greater than that for the stable bubble at the higher pressure amplitude and did not significantly decrease with frequency. Furthermore, SCL and Na* were detected only under unstable bubble conditions. These results imply that the instability of bubbles significantly enhances sonochemical efficiency for non-volatile substances in liquid phase.

  17. Slurry bubble column hydrodynamics

    NASA Astrophysics Data System (ADS)

    Rados, Novica

    Slurry bubble column reactors are presently used for a wide range of reactions in both chemical and biochemical industry. The successful design and scale up of slurry bubble column reactors require a complete understanding of multiphase fluid dynamics, i.e. phase mixing, heat and mass transport characteristics. The primary objective of this thesis is to improve presently limited understanding of the gas-liquid-solid slurry bubble column hydrodynamics. The effect of superficial gas velocity (8 to 45 cm/s), pressure (0.1 to 1.0 MPa) and solids loading (20 and 35 wt.%) on the time-averaged solids velocity and turbulent parameter profiles has been studied using Computer Automated Radioactive Particle Tracking (CARPT). To accomplish this, CARPT technique has been significantly improved for the measurements in highly attenuating systems, such as high pressure, high solids loading stainless steel slurry bubble column. At a similar set of operational conditions time-averaged gas and solids holdup profiles have been evaluated using the developed Computed Tomography (CT)/Overall gas holdup procedure. This procedure is based on the combination of the CT scans and the overall gas holdup measurements. The procedure assumes constant solids loading in the radial direction and axially invariant cross-sectionally averaged gas holdup. The obtained experimental holdup, velocity and turbulent parameters data are correlated and compared with the existing low superficial gas velocities and atmospheric pressure CARPT/CT gas-liquid and gas-liquid-solid slurry data. The obtained solids axial velocity radial profiles are compared with the predictions of the one dimensional (1-D) liquid/slurry recirculation phenomenological model. The obtained solids loading axial profiles are compared with the predictions of the Sedimentation and Dispersion Model (SDM). The overall gas holdup values, gas holdup radial profiles, solids loading axial profiles, solids axial velocity radial profiles and solids shear stress radial profiles are correlated using several widely used empirical correlations that are modified and improved to better represent present data.

  18. Bubble dynamics in drinks

    NASA Astrophysics Data System (ADS)

    Brou?ková, Zuzana; Trávní?ek, Zden?k; Šafa?ík, Pavel

    2014-03-01

    This study introduces two physical effects known from beverages: the effect of sinking bubbles and the hot chocolate sound effect. The paper presents two simple "kitchen" experiments. The first and second effects are indicated by means of a flow visualization and microphone measurement, respectively. To quantify the second (acoustic) effect, sound records are analyzed using time-frequency signal processing, and the obtained power spectra and spectrograms are discussed.

  19. Time and Space Dependent Stochastic Acceleration Model for the Fermi Bubbles

    E-print Network

    Sasaki, K; Terasawa, T

    2015-01-01

    Fermi-LAT reveals two huge gamma-ray bubbles existing in the Galactic Center, called 'Fermi Bubbles'. The existence of two microwave bubbles at the same region are also reported by the observation by WMAP, dubbed 'WMAP haze'. In order to explain these components, It has been argued that the gamma-rays arise from Inverse-Compton scattering of relativistic electrons accelerated by plasma turbulence, and the microwaves are radiated by synchrotron radiation. But no previous research reproduces both the Fermi Bubbles and WMAP haze under typical magnetic fields in the galaxy. We assume that shocks present in the bubbles and the efficiency of the acceleration by plasma turbulence, 'stochastic acceleration', changes with the distance from the shock front. The distance from the shock front increases with time, accordingly the efficiency of the acceleration changes with time. We also consider the time development of the electrons escape from the turbulence by diffusive loss. Our model succeed to reproduce both the obse...

  20. Space plasma physics research

    NASA Technical Reports Server (NTRS)

    Comfort, Richard H.; Horwitz, James L.

    1993-01-01

    During the course of this grant, work was performed on a variety of topics and there were a number of significant accomplishments. A summary of these accomplishments is included. The topics studied include empirical model data base, data reduction for archiving, semikinetic modeling of low energy plasma in the inner terrestrial magnetosphere and ionosphere, O(+) outflows, equatorial plasma trough, and plasma wave ray-tracing studies. A list of publications and presentations which have resulted from this research is also included.

  1. In Search of the Big Bubble

    ERIC Educational Resources Information Center

    Simoson, Andrew; Wentzky, Bethany

    2011-01-01

    Freely rising air bubbles in water sometimes assume the shape of a spherical cap, a shape also known as the "big bubble". Is it possible to find some objective function involving a combination of a bubble's attributes for which the big bubble is the optimal shape? Following the basic idea of the definite integral, we define a bubble's surface as…

  2. Bubble dynamics, shock waves and sonoluminescence

    Microsoft Academic Search

    C.-D. Ohl; T. Kurz; R. Geisler; O. Lindau; W. Lauterborn

    1999-01-01

    Sound and light emission by bubbles is studied experimentally. Single bubbles kept in a bubble trap and single laser-generated bubbles are investigated using ultrafast and high-speed photography in combination with hydrophones. The optical observation at 20 million frames per second of the shock waves emitted has proven instrumental in revealing the dynamic process upon bubble collapse. When jet formation is

  3. Stable Multibubble Sonoluminescence Bubble Patterns

    SciTech Connect

    Posakony, Gerald J.; Greenwood, Lawrence R.; Ahmed, Salahuddin

    2006-06-30

    Multibubble standing wave patterns can be generated from a flat piezoceramic transducer element propagating into water. By adding a second transducer positioned at 90 degrees from the transducer generating the standing wave, a 3-dimensional volume of stable single bubbles can be established. Further, the addition of the second transducer stabilizes the bubble pattern so that individual bubbles may be studied. The size of the bubbles and the separation of the standing waves depend on the frequency of operation. Two transducers, operating at frequencies above 500 kHz, provided the most graphic results for the configuration used in this study. At these frequencies stable bubbles exhibit a bright sonoluminescence pattern. Whereas stable SBSL is well-known, stable MBSL has not been previously reported. This paper includes discussions of the acoustic responses, standing wave patterns, and pictorial results of the separation of individual bubble of sonoluminescence in a multibubble sonoluminescence environment.

  4. Electrowetting of a soap bubble

    E-print Network

    Arscott, Steve

    2013-01-01

    A proof-of-concept demonstration of the electrowetting-on-dielectric of a sessile soap bubble is reported here. The bubbles are generated using a commercial soap bubble mixture - the surfaces are composed of highly doped, commercial silicon wafers covered with nanometre thick films of Teflon. Voltages less than 40V are sufficient to observe the modification of the bubble shape and the apparent bubble contact angle. Such observations open the way to inter alia the possibility of bubble-transport, as opposed to droplet-transport, in fluidic microsystems (e.g. laboratory-on-a-chip) - the potential gains in terms of volume, speed and surface/volume ratio are non-negligible.

  5. Electrowetting of a soap bubble

    E-print Network

    Steve Arscott

    2013-04-25

    A proof-of-concept demonstration of the electrowetting-on-dielectric of a sessile soap bubble is reported here. The bubbles are generated using a commercial soap bubble mixture - the surfaces are composed of highly doped, commercial silicon wafers covered with nanometre thick films of Teflon. Voltages less than 40V are sufficient to observe the modification of the bubble shape and the apparent bubble contact angle. Such observations open the way to inter alia the possibility of bubble-transport, as opposed to droplet-transport, in fluidic microsystems (e.g. laboratory-on-a-chip) - the potential gains in terms of volume, speed and surface/volume ratio are non-negligible.

  6. Equatorial currents in the Western Indian ocean.

    PubMed

    Luyten, J R; Fieux, M; Gonella, J

    1980-08-01

    Measurements were made in the equatorial Indian Ocean during spring and summer 1979 from the Somali coast to 62 degrees E in the interior of the western basin. The detailed vertical profiles of horizontal current show that the energetic dominance throughout the region of variability was on vertical scales of several hundreds of meters, confined to within a few degrees of the equator, as observed in 1976. The near-surface equatorial circulation responded directly to variations in the wind field, and satellite-tracked drifter buoys showed the equatorial surface jet extending across the width of the ocean. This eastward flow is generated by the eastward winds that appear in the interval between the northeast and southwest monsoons. The zonal velocity fluctuations extended in a consistent pattern over the observation region. The time and meridional scales of the variability were similar to those observed in 1976, suggesting that the velocity field is dominated by long-term, equatorially trapped motions with long zonal scales. PMID:17756843

  7. Empirical modelling of equatorial ionospheric scintillation

    Microsoft Academic Search

    P. K. Pasricha; B. M. Reddy

    1986-01-01

    A computer-based model of ionospheric scintillations has been developed by Fremouw (socalled the WBMOD model) to give a mean scintillation index for a given set of observing conditions. The WBMOD model incorporates some of the scintillation observations made with the DNA wideband satellite. A comparison is made between the scintillation morphology observed at an equatorial station Ooty with the one

  8. An improved model of equatorial scintillation

    Microsoft Academic Search

    J. A. Secan; R. M. Bussey; E. J. Fremouw; Sa. Basu

    1995-01-01

    One of the main limitations of the modeling work that went into the equatorial section of the Wideband ionospheric scintillation model (WBMOD) was that the data set used in the modeling was limited to two stations near the dip equator (Ancon, Peru, and Kwajalein Island, in the North Pacific Ocean) at two fixed local times (nominally 1000 and 2200). Over

  9. Equatorial scintillation model. Technical report, 1 February 1983-30 April 1985

    Microsoft Academic Search

    E. J. Fremouw; R. E. Robins

    1985-01-01

    Radiowave scintillation in the presence of natural and\\/or high-altitude nuclear disturbances has the potential to disrupt numerous transionospheric radio and radar systems. This report develops a model characterizing the plasma-density irregularities that produce scintillation in the naturally disturbed equatorial F layer. The model is incorporated into Program WBMOD along with subroutines for computing both link geometry and scintillation indices, the

  10. Thermal protons in the morning magnetosphere - Filling and heating near the equatorial plasmapause

    Microsoft Academic Search

    G. L. Wrenn; J. J. Sojka; J. F. E. Johnson

    1984-01-01

    Measurements of the cold-proton velocity distribution near the morning equatorial plasmapause, obtained with the suprathermal plasma analyzers (SPA) on GEOS-1 during a magnetic-storm period on November 25-30, 1977, are reported and analyzed. The SPA instruments, data acquisition, and analysis techniques are explained, and the results are presented graphically. A 0.5-1.5-eV plasmapause interaction region, where the scattering and heating of ionospheric

  11. Bubbly wake of surface vessels

    NASA Astrophysics Data System (ADS)

    Caillé, François; Magnaudet, Jacques; Clanet, Christophe

    2006-11-01

    We study the length of the bubbly wake of surface vessels. This wake is important for the boat security since it can extend to several ship length and thus increases the detectability of the ship by torpedoes. The image analysis of the wake of real scale ships reveals the sensitivity of the length to propellers. We have thus conducted a systematic study in the laboratory of the interaction bubble/propeller, trying to address several questions:- what is the role of cavitation?- is the propeller able to attract the bubbles present along the ship at the sea surface?- if attracted, can these bubble be broken by the propeller?

  12. When sound slows down bubbles

    E-print Network

    Remi Dangla; Cedric Poulain

    2010-04-06

    We present experimental evidence that a bubble moving in a fluid in which a well-chosen acoustic noise is superimposed can be significantly slowed down for moderate acoustic pressures. Through mean velocity measurements, we show that a condition for this effect to occur is for the acoustic noise spectrum to match or overlap the bubble's fundamental resonant mode. By rendering the bubble's oscillations and translational movements using high speed video, we evidence that radial oscillations have no effect on the mean velocity, while above a critical sound pressure threshold, Faraday waves are triggered and are responsible for the bubble's drag increase.

  13. Fluid Dynamics of Bubbly Liquids

    NASA Astrophysics Data System (ADS)

    Tsang, Ying H.; Koch, Donald L.; Sangani, Ashok S.

    2002-11-01

    Bubbles with high Reynolds number and low Weber number may produce a fluid velocity disturbance that can be approximated by a potential flow. We studied the behavior of the inertially dominated suspensions of bubbles of about 1.5 mm diameter in vertical and inclined channels. The gradual decrease of bubble velocity as volume fraction increases is in qualitative agreement with the predictions. By inclining the channel, the resulting buoyancy variation drives a shear flow and provides a means of observing the effects of weak shear on a bubbly liquid. The tendency of buoyancy driven motion to cause the bubbles to accumulate on the upper wall is balanced by lift forces and an effective bubble-phase diffusivity in the cross-channel direction. The bubble velocity gradient can be understood in terms of a balance of the component of the buoyancy force parallel to the channel and an effective viscosity associated with the Reynolds stresses produced by bubble-induced liquid velocity fluctuations. The effective viscosity required to explain the measured bubble velocity gradient is about 1000 times that of the suspending liquid. A pipe flow with the liquid being recirculated, which provides a larger range of shear to buoyancy motion, is under construction.

  14. Bubble Measuring Instrument and Method

    NASA Technical Reports Server (NTRS)

    Kline-Schoder, Robert (Inventor); Magari, Patrick J. (Inventor)

    2002-01-01

    Method and apparatus are provided for a non-invasive bubble measuring instrument operable for detecting, distinguishing, and counting gaseous embolisms such as bubbles over a selectable range of bubble sizes of interest. A selected measurement volume in which bubbles may be detected is insonified by two distinct frequencies from a pump transducer and an image transducer. respectively. The image transducer frequency is much higher than the pump transducer frequency. The relatively low-frequency pump signal is used to excite bubbles to resonate at a frequency related to their diameter. The image transducer is operated in a pulse-echo mode at a controllable repetition rate that transmits bursts of high-frequency ultrasonic signal to the measurement volume in which bubbles may be detected and then receives the echo. From the echo or received signal, a beat signal related to the repetition rate may be extracted and used to indicate the presence or absence of a resonant bubble. In a preferred embodiment, software control maintains the beat signal at a preselected frequency while varying the pump transducer frequency to excite bubbles of different diameters to resonate depending on the range of bubble diameters selected for investigation.

  15. Helium bubble bursting in tungsten

    SciTech Connect

    Sefta, Faiza [University of California, Berkeley, California 94720 (United States); Juslin, Niklas [University of Tennessee, Knoxville, Tennessee 37996 (United States); Wirth, Brian D., E-mail: bdwirth@utk.edu [University of Tennessee, Oak Ridge National Laboratory, Knoxville, Tennessee 37996 (United States)

    2013-12-28

    Molecular dynamics simulations have been used to systematically study the pressure evolution and bursting behavior of sub-surface helium bubbles and the resulting tungsten surface morphology. This study specifically investigates how bubble shape and size, temperature, tungsten surface orientation, and ligament thickness above the bubble influence bubble stability and surface evolution. The tungsten surface is roughened by a combination of adatom “islands,” craters, and pinholes. The present study provides insight into the mechanisms and conditions leading to various tungsten topology changes, which we believe are the initial stages of surface evolution leading to the formation of nanoscale fuzz.

  16. Bubble measuring instrument and method

    NASA Technical Reports Server (NTRS)

    Kline-Schoder, Robert (Inventor); Magari, Patrick J. (Inventor)

    2003-01-01

    Method and apparatus are provided for a non-invasive bubble measuring instrument operable for detecting, distinguishing, and counting gaseous embolisms such as bubbles over a selectable range of bubble sizes of interest. A selected measurement volume in which bubbles may be detected is insonified by two distinct frequencies from a pump transducer and an image transducer, respectively. The image transducer frequency is much higher than the pump transducer frequency. The relatively low-frequency pump signal is used to excite bubbles to resonate at a frequency related to their diameter. The image transducer is operated in a pulse-echo mode at a controllable repetition rate that transmits bursts of high-frequency ultrasonic signal to the measurement volume in which bubbles may be detected and then receives the echo. From the echo or received signal, a beat signal related to the repetition rate may be extracted and used to indicate the presence or absence of a resonant bubble. In a preferred embodiment, software control maintains the beat signal at a preselected frequency while varying the pump transducer frequency to excite bubbles of different diameters to resonate depending on the range of bubble diameters selected for investigation.

  17. Bubble Measuring Instrument and Method

    NASA Technical Reports Server (NTRS)

    Kline-Schoder, Robert (Inventor); Magari, Patrick J. (Inventor)

    2002-01-01

    Method and apparatus are provided for a non-invasive bubble measuring instrument operable for detecting, distinguishing, and counting gaseous embolisms such as bubbles over a selectable range of bubble sizes of interest. A selected measurement volume in which bubbles may be detected is insonified by two distinct frequencies from a pump transducer and an image transducer, respectively. The image transducer frequency is much higher than the pump transducer frequency. The relatively low-frequency pump signal is used to excite bubbles to resonate at a frequency related to their diameter. The image transducer is operated in a pulse-echo mode at a controllable repetition rate that transmits bursts of high-frequency ultrasonic signal to the measurement volume in which bubbles may be detected and then receives the echo. From the echo or received signal, a beat signal related to the repetition rate may be extracted and used to indicate the presence or absence of a resonant bubble. In a preferred embodiment, software control maintains the beat signal at a preselected frequency while varying the pump transducer frequency to excite bubbles of different diameters to resonate depending on the range of bubble diameters selected for investigation.

  18. Bubble Measuring Instrument and Method

    NASA Technical Reports Server (NTRS)

    Kline-Schoder, Robert (Inventor); Magari, Patrick J. (Inventor)

    2002-01-01

    Method and apparatus are provided for a non-invasive bubble measuring instrument operable for detecting. distinguishing, and counting gaseous embolisms such as bubbles over a selectable range of bubble sizes of interest. A selected measurement volume in which bubbles may be detected is insonified by two distinct frequencies from a pump transducer and an image transducer, respectively. The image transducer frequency is much higher than the pump transducer frequency. The relatively low-frequency pump signal is used to excite bubbles to resonate at a frequency related to their diameter. The image transducer is operated in a pulse-echo mode at a controllable repetition rate that transmits bursts of high-frequency ultrasonic signal to the measurement volume in which bubbles may be detected and then receive, the echo. From the echo or received signal, a beat signal related to the repetition rate may be extracted and used to indicate the presence or absence of a resonant bubble. In a preferred embodiment, software control maintains the beat signal at a preselected frequency while varying the pump transducer frequency to excite bubbles of different diameters to resonate depending on the range of bubble diameters selected for investigation.

  19. Wave Forcing of Saturn's Equatorial Oscillation

    NASA Technical Reports Server (NTRS)

    Flasar, F. M.; Schlinder, P. J.; Guerlet, S.; Fouchet, T.

    2011-01-01

    Ground-based measurements and Cassini data from CIRS thermal-infrared spectra and radio-occultation soundings have characterized the spatial structure and temporal behavior of a 15-year equatorial oscillation in Saturn's stratosphere. The equatorial region displays a vertical pattern of alternating warm and cold anomalies and, concomitantly, easterly and westerly winds relative to the cloud-top winds, with a peak-to-peak amplitude of 200 m/s. Comparison of the Cassini data over a four-year period has established that the pattern of mean zonal winds and temperatures descends at a rate of roughly I scale height over 4 years. This behavior is reminiscent of the equatorial oscillations in Earth's middle atmosphere. Here the zonal-mean spatial structure and descending pattern are driven by the absorption of vertically propagating waves. The maximum excursions in the pattern of easterly and westerly winds is determined by the limits of the zonal phase velocities of the waves. Here we report on the characterization of the waves seen in the temperature profiles retrieved from the Cassini radio-occultation soundings. The equatorial profiles exhibit a complex pattern of wavelike structure with dimensions one pressure scale height and smaller. We combine a spectral decomposition with a WKBJ analysis, where the vertical wavelength is assumed to vary slowly with the ambient static stability and doppler-shifted phase velocity of the wave. Use of the temperature and zonal wind maps from CIRS makes this approach viable. On Earth, the wave forcing associated with the equatorial oscillations generates secondary meridional circulations that affect the mean flow and planetary wave ducting well away from the equator. This may relate to the triggering of the recently reported mid-latitude storms on Saturn.

  20. plasmas

    NASA Astrophysics Data System (ADS)

    Zhang, H. Y.; Jin, C. G.; Yang, Y.; Ye, C.; Zhuge, L. J.; Wu, X. M.

    2014-12-01

    As-deposited HfO2 films were modified by CHF3, C4F8, and mixed C4F8/O2 plasmas in a dual-frequency capacitively coupled plasma chamber driven by radio frequency generators of 60 MHz as the high frequency (HF) source and 2 MHz as the low frequency source (60/2 MHz). The influences of various surface plasma treatments under CHF3, C4F8, and C4F8/O2 were investigated in order to understand the chemical and structural changes in thin-film systems, as well as their influence on the electrical properties. Fluorine atoms were incorporated into the HfO2 films by either CHF3 or C4F8 plasma treatment; meanwhile, the C/F films were formed on the surface of the HfO2 films. The formation of C/F layers decreased the k value of the gate stacks because of its low dielectric constant. However, the addition of O2 gas in the discharge gases suppressed the formation of C/F layers. After thermal annealing, tetragonal HfO2 phase was investigated in both samples treated with CHF3 and C4F8 plasmas. However, the samples treated with O-rich plasmas showed monoclinic phase, which indicated that the addition of O plasmas could influence the Hf/O ratio of the HfO2 films. The mechanism of the t-HfO2 formation was attributed to oxygen insufficiency generated by the incorporation of F atoms. The capacitors treated with C4F8/O2 plasmas displayed the highest k value, which ascribed that the C/F layers were suppressed and the tetragonal phase of HfO2 was formed. Good electrical properties, especially on the hysteresis voltage and frequency dispersion, were obtained because the bulk traps were passivated by the incorporation of F atoms. However, the H-related traps were generated during the CHF3 plasma treatments, which caused the performance degradation. All the treated samples showed lower leakage current density than the as-deposited HfO2 films at negative bias due to the reduced trap-assisted tunneling by the incorporation of F to block the electrons transferring from metal electrode to the trap level.

  1. Microfluidic Actuation Using Electrochemically Generated Bubbles

    E-print Network

    Sachs, Frederick

    Microfluidic Actuation Using Electrochemically Generated Bubbles Susan Z. Hua,*, Frederick Sachs, Buffalo, New York 14260 Bubble-based actuation in microfluidic applications is attractive owing closing) rate increases with applied voltage, small microfluidic dimensions accelerate bubble deflation

  2. A bubbling bolt

    E-print Network

    Guillaume Bossard; Stefanos Katmadas

    2014-05-16

    We present a new solvable system, solving the equations of five-dimensional ungauged N=1 supergravity coupled to vector multiplets, that allows for non-extremal solutions and reduces to a known system when restricted to the floating brane Ansatz. A two-centre globally hyperbolic smooth geometry is obtained as a solution to this system, describing a bubble linking a Gibbons--Hawking centre to a charged bolt. However this solution turns out to violate the BPS bound, and we show that its generalisation to an arbitrary number of Gibbons--Hawking centres never admits a spin structure.

  3. Bubble levitation and translation under single-bubble sonoluminescence conditions.

    PubMed

    Matula, Thomas J

    2003-08-01

    Bubble levitation in an acoustic standing wave is re-examined for conditions relevant to single-bubble sonoluminescence. Unlike a previous examination [Matula et al., J. Acoust. Soc. Am. 102, 1522-1527 (1997)], the stable parameter space [Pa,R0] is accounted for in this realization. Forces such as the added mass force and drag are included, and the results are compared with a simple force balance that equates the Bjerknes force to the buoyancy force. Under normal sonoluminescence conditions, the comparison is quite favorable. A more complete accounting of the forces shows that a stably levitated bubble does undergo periodic translational motion. The asymmetries associated with translational motion are hypothesized to generate instabilities in the spherical shape of the bubble. A reduction in gravity results in reduced translational motion. It is hypothesized that such conditions may lead to increased light output from sonoluminescing bubbles. PMID:12942960

  4. Stable tridimensional bubble clusters in multi-bubble sonoluminescence (MBSL).

    PubMed

    Rosselló, J M; Dellavale, D; Bonetto, F J

    2015-01-01

    In the present work, stable clusters made of multiple sonoluminescent bubbles are experimentally and theoretically studied. Argon bubbles were acoustically generated and trapped using bi-frequency driving within a cylindrical chamber filled with a sulfuric acid aqueous solution (SA85w/w). The intensity of the acoustic pressure field was strong enough to sustain, during several minutes, a large number of positionally and spatially fixed (without pseudo-orbits) sonoluminescent bubbles over an ellipsoidally-shaped tridimensional array. The dimensions of the ellipsoids were studied as a function of the amplitude of the applied low-frequency acoustic pressure (PAc(LF)) and the static pressure in the fluid (P0). In order to explain the size and shape of the bubble clusters, we performed a series of numerical simulations of the hydrodynamic forces acting over the bubbles. In both cases the observed experimental behavior was in excellent agreement with the numerical results. The simulations revealed that the positionally stable region, mainly determined by the null primary Bjerknes force (F?Bj), is defined as the outer perimeter of an axisymmetric ellipsoidal cluster centered in the acoustic field antinode. The role of the high-frequency component of the pressure field and the influence of the secondary Bjerknes force are discussed. We also investigate the effect of a change in the concentration of dissolved gas on the positional and spatial instabilities through the cluster dimensions. The experimental and numerical results presented in this paper are potentially useful for further understanding and modeling numerous current research topics regarding multi-bubble phenomena, e.g. forces acting on the bubbles in multi-frequency acoustic fields, transient acoustic cavitation, bubble interactions, structure formation processes, atomic and molecular emissions of equal bubbles and nonlinear or unsteady acoustic pressure fields in bubbly media. PMID:24974006

  5. Lithospheric Flexural Modeling of Iapetus' Equatorial Ridge

    NASA Astrophysics Data System (ADS)

    Zheng, W.; Ip, W.-H.; Teng, L. S.

    2012-04-01

    Iapetus, which is one of Saturn's ball-shaped satellites, has some unique features in the Solar System. This satellite has a mean radius of 735 km, and there is an approximately 20-kilometer-high mountain lying precisely on its equator. The mountain is known as an "equatorial ridge" since it makes Iapetus appear walnut shaped. The origin of the equatorial ridge is attributed to several hypotheses, including different endogenesis and exogenesis processes. In this work, we attempted to construct a flexural model of the equatorial ridge using elastic lithosphere theory. The equatorial ridge is treated as a linear load which exerts uniform force on Iapetus' hard shell (i.e. elastic lithosphere of Iapetus). To calculate the deflection of surface, we use the Digital Terrain Model (DTM) data of Iapetus' leading side published by Giese et al. (2008). Giese et al. also pointed out that the elastic lithospheric thickness of Iapetus must exceed 100 km to support the ridge without deflecting. However, we found possible evidence in the DTM data that implied deflection. There are two sites of surface depression on the northern side of the equatorial ridge. The few-kilometer deflection implies a thinner lithosphere than previous suggested. Assume that the thickness of elastic lithosphere is only 5% below of the radius of Iapetus, so the flat-Earth and one-plate condition could adapt to the flexure model of Iapetus. Based on analysis of the distance between a bulge and the ridge, the calculated lithospheric thickness is 6-10 km. The new result seems controversial, but the modeled surface profile is highly consistent with numerical ridge DTM profile extracted from Giese et al. (2008). Thinner lithosphere also supports the contraction model proposed by Sandwell and Schubert (2010) since the bucking harmonic degree increases. In the other hand, the transformation layer between hard shell and plastic inner core may need constraint on thermal history or crystal form of ice. In conclusion, The flexural model of Iapetus' equatorial ridge reveals the possibility of thinner hard shell, fits the surface profile, and supplies more clues to the origin of Iapetus, the interesting satellite in the Solar System.

  6. Why Are Bubbles So Colorful?

    NSDL National Science Digital Library

    Optical Society of America

    2008-01-01

    In this activity, learners explore why they can see colors in bubbles and why they change. Learners also examine what thin slits do to light and how this phenomenon is similar to that of bubbles and oil slicks. Note: This activity works best outside in the sunlight.

  7. Phase Diagrams for Sonoluminescing Bubbles

    Microsoft Academic Search

    Sascha Hilgenfeldt; Detlef Lohse; Michael P. Brenner

    1996-01-01

    Sound driven gas bubbles in water can emit light pulses. This phenomenon is called sonoluminescence (SL). Two different phases of single bubble SL have been proposed: diffusively stable and diffusively unstable SL. We present phase diagrams in the gas concentration vs forcing pressure state space and also in the ambient radius vs gas concentration and vs forcing pressure state spaces.

  8. Sonoluminescing bubbles and mass diffusion

    Microsoft Academic Search

    Ritva Löfstedt; Keith Weninger; Seth Putterman; Bradley P. Barber

    1995-01-01

    The transduction of sound into light by a pulsating bubble in water occurs when its maximum radius is about ten times greater than its ambient radius. For such high-amplitude motion, the steady-state balance of mass flow between the bubble and gas dissolved in the surrounding fluid can be maintained by diffusion only at low partial pressures, about 3 Torr. The

  9. Bubble formation in microgravity

    NASA Technical Reports Server (NTRS)

    Antar, Basil N.

    1996-01-01

    An extensive experimental program was initiated for the purpose of understanding the mechanisms leading to bubble generation during fluid handling procedures in a microgravity environment. Several key fluid handling procedures typical for PCG experiments were identified for analysis in that program. Experiments were designed to specifically understand how such procedures can lead to bubble formation. The experiments were then conducted aboard the NASA KC-135 aircraft which is capable of simulating a low gravity environment by executing a parabolic flight attitude. However, such a flight attitude can only provide a low gravity environment of approximately 10-2go for a maximum period of 30 seconds. Thus all of the tests conducted for these experiments were designed to last no longer than 20 seconds. Several experiments were designed to simulate some of the more relevant fluid handling procedures during protein crystal growth experiments. These include submerged liquid jet cavitation, filling of a cubical vessel, submerged surface scratch, attached drop growth, liquid jet impingement, and geysering experiments. To date, four separate KC-135 flight campaigns were undertaken specifically for performing these experiments. However, different experiments were performed on different flights.

  10. Bubble formation in microgravity

    NASA Technical Reports Server (NTRS)

    Antar, Basil N.

    1994-01-01

    Two KC-135 flight campaigns have been conducted to date which are specifically dedicated to study bubble formation in microgravity. The first flight was conducted during March 14-18, 1994, and the other during June 20-24, 1994. The results from the June 1994 flight have not been analyzed yet, while the results from the March flight have been partially analyzed. In the first flight three different experiments were performed, one with the specific aim at determining whether or not cavitation can take place during any of the fluid handling procedures adopted in the shuttle bioprocessing experiments. The other experiments were concerned with duplicating some of the procedures that resulted in bubble formation, namely the NCS filling procedure and the needle scratch of a solid surface. The results from this set of experiments suggest that cavitation did not take place during any of the fluid handling procedures. The results clearly indicate that almost all were generated as a result of the breakup of the gas/liquid interface. This was convincingly demonstrated in the scratch tests as well as in the liquid fill tests.

  11. Model of single bubble sonoluminescence

    SciTech Connect

    An Yu; Ying, C.F. [Department of Physics, Tsinghua University, Beijing 100084 (China); Institute of Acoustics, Chinese Academy of Science, Beijing 100080 (China)

    2005-03-01

    The temperature within and the sonoluminescence characteristics of a stable inert-gas single bubble grown in water under some given conditions are computed by using a model that is as sufficiently complete as we can manage, except that possible chemical reactions within the bubble are neglected. We work with several different versions of the equation describing the motion of the bubble wall, which are usually considered to give merely slight differences; or vary a parameter in the formula calculating the net increment of the water condensed at the bubble wall. It is found that the final outcomes of the temperature and the sonoluminescence can be significantly different in some cases. This illustration points to the importance of differentiating among the various seemingly similar equations and of adopting the correct value of the parameter used in the computation model of a single bubble.

  12. Steady-state Hadronic Gamma-Ray Emission from 100-Myr-Old Fermi Bubbles

    NASA Astrophysics Data System (ADS)

    Crocker, Roland M.; Bicknell, Geoffrey V.; Carretti, Ettore; Hill, Alex S.; Sutherland, Ralph S.

    2014-08-01

    Fermi Bubbles are enigmatic ?-ray features of the Galactic bulge. Both putative activity (within few × Myr) connected to the Galactic center super-massive black hole and, alternatively, nuclear star formation have been claimed as the energizing source of the Bubbles. Likewise, both inverse-Compton emission by non-thermal electrons ("leptonic" models) and collisions between non-thermal protons and gas ("hadronic" models) have been advanced as the process supplying the Bubbles' ?-ray emission. An issue for any steady state hadronic model is that the very low density of the Bubbles' plasma seems to require that they accumulate protons over a multi-gigayear timescale, much longer than other natural timescales occurring in the problem. Here we present a mechanism wherein the timescale for generating the Bubbles' ?-ray emission via hadronic processes is ~few × 108 yr. Our model invokes the collapse of the Bubbles' thermally unstable plasma, leading to an accumulation of cosmic rays and magnetic field into localized, warm (~104 K), and likely filamentary condensations of higher-density gas. Under the condition that these filaments are supported by non-thermal pressure, the hadronic emission from the Bubbles is L ? ~= 2 × 1037 erg s-1 \\dot{M}_{in}/(0.1 \\, {M_\\odot } yr-1 ) \\ T_{FB}^2/(3.5 \\times 10^7 K)2 M fil/M pls, equal to their observed luminosity (normalizing to the star-formation-driven mass flux into the Bubbles and their measured plasma temperature and adopting the further result that the mass in the filaments, M fil is approximately equal to the that of the Bubbles' plasma, M pls).

  13. Metallic ions in the equatorial ionosphere

    NASA Technical Reports Server (NTRS)

    Aikin, A. C.; Goldberg, R. A.

    1972-01-01

    Four positive ion composition measurements of the equatorial E region made at Thumba, India, are presented. During the day, the major ions between 90 and 125 km are NO(+) and O2(+). A metallic ion layer centered at 92 km is observed, and found to contain Mg(+), Fe(+), Ca(+), K(+), Al(+), and Na(+) ions. The layer is explained in terms of a similarly shaped latitude distribution of neutral atoms which are photoionized and charge-exchanged with NO(+) and O2(+). Three body reactions form molecular metallic ions which are rapidly lost by dissociative ion-electron recombination. Nighttime observations show downward drifting of the metallic ion layer caused by equatorial dynamo effects. These ions react and form neutral metals which exchange charges with NO(+) and O2(+) to produce an observed depletion of those ions within the metallic ion region.

  14. Swarm equatorial electric field chain: First results

    NASA Astrophysics Data System (ADS)

    Alken, P.; Maus, S.; Chulliat, A.; Vigneron, P.; Sirol, O.; Hulot, G.

    2015-02-01

    The eastward equatorial electric field (EEF) in the E region ionosphere drives many important phenomena at low latitudes. We developed a method of estimating the EEF from magnetometer measurements of near-polar orbiting satellites as they cross the magnetic equator, by recovering a clean signal of the equatorial electrojet current and modeling the observed current to determine the electric field present during the satellite pass. This algorithm is now implemented as an official Level-2 Swarm product. Here we present first results of EEF estimates from nearly a year of Swarm data. We find excellent agreement with independent measurements from the ground-based coherent scatter radar at Jicamarca, Peru, as well as horizontal field measurements from the West African Magnetometer Network magnetic observatory chain. We also calculate longitudinal gradients of EEF measurements made by the A and C lower satellite pair and find gradients up to about 0.05 mV/m/deg with significant longitudinal variability.

  15. Empirical modelling of equatorial ionospheric scintillation

    NASA Astrophysics Data System (ADS)

    Pasricha, P. K.; Reddy, B. M.

    1986-06-01

    A computer-based model of ionospheric scintillations has been developed by Fremouw (socalled the WBMOD model) to give a mean scintillation index for a given set of observing conditions. The WBMOD model incorporates some of the scintillation observations made with the DNA wideband satellite. A comparison is made between the scintillation morphology observed at an equatorial station Ooty with the one evolved with the WBMOD model. Morphological features at other stations in the equatorial region are briefly described. The WBMOD model predicts the pre-midnight maximum seen at the Indian longitudes. The seasonal pattern reproduced by the model incorporates longitudinal variability. The solar activity dependence in the model seems to be rather high. Empirical expressions giving the dependence of scintillation index on morphological parameters are obtained

  16. Atmosphere dynamics in the equatorial meteor zone

    NASA Technical Reports Server (NTRS)

    Kascheev, B. L.

    1987-01-01

    The study of the atmospheric circulation of the Earth from its surface to the altitudes of 100 to 110 km is essential for establishing atmospheric motion regularities with a view toward perfecting weather forecasting. The main results of the Soviet equatorial meteor expedition (SEME) are presented. A continuous cycle of measurements was carried out. Considerable interdiurnal variation of the zonal component was observed. Importantly, in the meridional component, the prevalence of a two day component was established in the equatorial meteor zone for the first time. The pronounced westward motion of the atmosphere over the equator is noted. The SEME data analysis has shown that the meteor zone is characterized by flashes of intensity of the internal gravity waves and turbulence at highest instability moments of atmosphere due to tidal motion.

  17. THE FERMI BUBBLES. II. THE POTENTIAL ROLES OF VISCOSITY AND COSMIC-RAY DIFFUSION IN JET MODELS

    SciTech Connect

    Guo Fulai; Mathews, William G. [UCO/Lick Observatory, Department of Astronomy and Astrophysics, University of California, Santa Cruz, CA 95064 (United States); Dobler, Gregory [Kavli Institute for Theoretical Physics, University of California, Santa Barbara Kohn Hall, Santa Barbara, CA 93106 (United States); Oh, S. Peng, E-mail: fulai@ucolick.org [Department of Physics, University of California, Santa Barbara Kohn Hall, Santa Barbara, CA 93106 (United States)

    2012-09-10

    The origin of the Fermi bubbles recently detected by the Fermi Gamma-ray Space Telescope in the inner Galaxy is mysterious. In the companion paper Guo and Mathews (Paper I), we use hydrodynamic simulations to show that they could be produced by a recent powerful active galactic nucleus (AGN) jet event. Here, we further explore this scenario to study the potential roles of shear viscosity and cosmic-ray (CR) diffusion on the morphology and CR distribution of the bubbles. We show that even a relatively low level of viscosity ({mu}{sub visc} {approx}> 3 g cm{sup -1} s{sup -1}, or {approx}0.1%-1% of Braginskii viscosity in this context) could effectively suppress the development of Kelvin-Helmholtz instabilities at the bubble surface, resulting in smooth bubble edges as observed. Furthermore, viscosity reduces circulating motions within the bubbles, which would otherwise mix the CR-carrying jet backflow near bubble edges with the bubble interior. Thus viscosity naturally produces an edge-favored CR distribution, an important ingredient to produce the observed flat gamma-ray surface brightness distribution. Generically, such a CR distribution often produces a limb-brightened gamma-ray intensity distribution. However, we show that by incorporating CR diffusion that is strongly suppressed across the bubble surface (as inferred from sharp bubble edges) but is close to canonical values in the bubble interior, we obtain a reasonably flat gamma-ray intensity profile. The similarity of the resulting CR bubble with the observed Fermi bubbles strengthens our previous result in Paper I that the Fermi bubbles were produced by a recent AGN jet event. Studies of the nearby Fermi bubbles may provide a unique opportunity to study the potential roles of plasma viscosity and CR diffusion on the evolution of AGN jets and bubbles.

  18. Basin Resonances in the Equatorial Indian Ocean

    NASA Astrophysics Data System (ADS)

    Han, W.; McCreary, J. P.; Masumoto, Y.; Vialard, J.; Duncan, B.

    2011-12-01

    Previous studies investigated resonant excitation of second-baroclinic-mode ( n= 2) equatorial Kelvin and Rossby waves, which form the semiannual (180-day) and 90-day resonances in the equatorial Indian Ocean (IO). This paper examines unresolved issues, including the reason why the 90-day resonance is concentrated in the eastern ocean, the timescale to establish the resonance, and the impact of complex basin geometry. A hierarchy of ocean models is used: an idealized 1-dimensional (1-d) model, a linear continuously stratified ocean model (LCSM), and an ocean general circulation model (OGCM) forced by QuikSCAT wind during 2000-2008. The observed 180-day and 90-day zonal surface current and sea level exhibit similar structures as those of basin resonances. Model results indicate that the eastern-basin concentration of the 90-day resonance happens because the westward-propagating Rossby wave is damped more than the eastward-propagating Kelvin wave, and superposition with other baroclinic modes further enhances the eastern maximum and weakens sea level variability near the western equatorial boundary. Without resonance, there are no peaks - although there are significant powers - at the 90-day and 180-day periods. The key timescale for the establishment of all resonances is the time it takes a Kelvin wave to cross the basin and first-meridional-mode (l = 1) Rossby wave to return. Thus, even though the 90-day winds have significant temporal variability, the 90-day resonance can be frequently excited in the real IO as evidenced by satellite-observed and OGCM-simulated sea level. The presence of the Indian subcontinent enhances the influence of equatorial variability in the north IO, especially along the west coast of India. The Maldives Islands weaken the 180-day resonance amplitude, but affect the 90-day resonance little because they fall in its "node" region. Additionally, resonance at 120-day period for the n = 1 mode is noted.

  19. Breaking of balanced and unbalanced equatorial waves.

    PubMed

    Bouchut, F; Le Sommer, J; Zeitlin, V

    2005-03-01

    A clear-cut signature of a wave-breaking event is irreversible modification of the mean flow. In this paper, we provide examples of different breaking mechanisms and show that breaking scenario of equatorial waves in the beta-plane shallow water model is determined by the degree of balance between the zonal component of the Coriolis force and the pressure gradient. Our analysis is based on a specially designed numerical method which guarantees two essential conditions to simulate nonlinear equatorial waves: (i) the scheme converges toward weak solutions including shocks and (ii) preserves the steadiness of balanced stationary solutions. This allows for accurate diagnostics of Lagrangian invariants of motion such as passive tracer density or potential vorticity. For unbalanced waves, the lack of balance leads to shock formation in finite time. In shock fronts, the variation of the dissipation rate induces a nonadvective potential vorticity flux and violates the local potential vorticity conservation valid for smooth solutions. This dissipative breaking mechanism is generic for unbalanced waves and is associated with enhanced mixing. For long, balanced (Rossby) waves, breaking consists in appearance of recirculation regions. It results in the formation of propagating patterns, the equatorial modons, which trap fluid particles. Such breaking occurs during the propagation of Rossby wave packets with positive geopotential anomaly and is strengthened by decreasing fluid depth. The modons are robust and collide quasielastically with Kelvin waves. PMID:15836268

  20. Multiple Influences on Equatorial Atlantic Variability

    NASA Astrophysics Data System (ADS)

    Behera, S. K.; Richter, I.; Masumoto, Y.; Taguchi, B.; Sasaki, H.; Yamagata, T.

    2013-12-01

    The equatorial Atlantic hosts a zonal mode of variability that is associated with signif-icant precipitation anomalies over tropical South America and Africa. Warm and cold events are referred to as Atlantic Niños and Niñas, respectively, due to their apparent similarity with El Niño-Southern Oscillation (ENSO) events. Like ENSO, the Atlantic zonal mode is thought to involve a positive feedback mechanism, in which weakening of the equatorial easterlies, thermocline deepening, and SST warming mutually rein-force each other. In the present study we use NCEP reanalysis, a high-resolution OGCM hindcast, and a coupled GCM to re-examine the dynamics governing Atlantic Ni-ños. We find that equatorial wind stress forcing and ENSO-like dynamics can explain some of the observed warm events but not all of them. In particular there are warm events that occur despite easterly surface wind anomalies in the preceding months. This is due to sub-surface warm anomalies at approximately 5N that are advected toward the equator. The sub-surface warming is linked to downwelling wind stress curl anomalies north of the equator. These, in turn, are related to SST anomalies in the northern tropical Atlantic (NTA), which induce weakening of the trade winds in the northern tropical Atlantic. Our results suggest an indirect pathway through which NTA SST anomalies can influence the zonal mode of variability.

  1. Magnetospheric space plasma investigations

    NASA Technical Reports Server (NTRS)

    Comfort, Richard H.; Horwitz, James L.

    1993-01-01

    The topics addressed are: (1) generalized semikinetic models; (2) collision-collisionless transition model; (3) observation of O+ outflows; (4) equatorial transitions; (5) inner plasmasphere-ionosphere coupling; (6) plasma wave physical processes; (7) ULF wave ray-tracing; and (8) nighttime anomalous electron heating events.

  2. Digital ionosonde observations during equatorial spread F-italic

    SciTech Connect

    Argo, P.E.; Kelley, M.C.

    1986-05-01

    In this paper we present and discuss equatorial spread F-italic data taken with a digital ionosonde/HF radar located at Huancayo, Peru. A modified phenomenology is developed which uses the system's ability to do echo location. The onset of irregularities is seen to occur in the east and to move westward, while inside this large-scale structure the plasma is found to drift eastward. A very curious difference has been identified between spread F-italic observations with the ionosonde and with the VHF radar at Jicamarca. At VHF, spread F-italic onset often occurs when the ionosphere is rising, whereas in all five examples presented here, the digital ionosonde detected onset when the apparent ionosphere motion was downward. The result even held on the one night of common data taking. The effect could be instrumental but may be related to the considerable orographic differences in the two sites. Isolated scattering patches are observed and are tentatively identified as detached or ''fossil'' plumes. At frequencies above the nominal f-italic/sub 0/F-italic/sub 2/ the system (and other ionosondes) may in fact function as a coherent radar. During one night, data were obtained simultaneously with the HF radar, a rocket, and the Jicamarca VHF radar. Comparisons of these data are discussed in detail. Finally, additional evidence is presented that acoustic gravity waves play a role in the development of equatorial spread F-italic and in the formation of detached plumes. To be self-consistent, the gravity waves must come from nearby sources such as the tropical rain forest to the east of Jicamarca.

  3. Initial thermal plasma observations from ISEE-1

    Microsoft Academic Search

    C. R. Baugher; C. R. Chappell; J. L. Horwitz; E. G. Shelley; D. T. Young

    1980-01-01

    The initial measurements of magnetospheric thermal ions by the Plasma Composition Experiment on ISEE-1 are presented to demonstrate the surprising variety in this plasma population. The data provide evidence that the adiabatic mapping of the high latitude ionosphere to the equatorial plasma trough provides an insufficient description of the origin, transport, and accumulation processes which supply low energy ions to

  4. Optimization of the ITER electron cyclotron equatorial launcher for improved heating and current drive functional capabilities

    NASA Astrophysics Data System (ADS)

    Farina, D.; Henderson, M.; Figini, L.; Saibene, G.

    2014-06-01

    The design of the ITER Electron Cyclotron Heating and Current Drive (EC H&CD) system has evolved in the last years both in goals and functionalities by considering an expanded range of applications. A large effort has been devoted to a better integration of the equatorial and the upper launchers, both from the point of view of the performance and of the design impact on the engineering constraints. However, from the analysis of the ECCD performance in two references H-mode scenarios at burn (the inductive H-mode and the advanced non-inductive scenario), it was clear that the EC power deposition was not optimal for steady-state applications in the plasma region around mid radius. An optimization study of the equatorial launcher is presented here aiming at removing this limitation of the EC system capabilities. Changing the steering of the equatorial launcher from toroidal to poloidal ensures EC power deposition out to the normalized toroidal radius ? ? 0.6, and nearly doubles the EC driven current around mid radius, without significant performance degradation in the core plasma region. In addition to the improved performance, the proposed design change is able to relax some engineering design constraints on both launchers.

  5. Optimization of the ITER electron cyclotron equatorial launcher for improved heating and current drive functional capabilities

    SciTech Connect

    Farina, D.; Figini, L. [Istituto di Fisica del Plasma, Consiglio Nazionale delle Ricerche, EURATOM-ENEA-CNR Association, via Cozzi 53, 20125 Milano (Italy); Henderson, M. [ITER Organization, 13108 Saint-Paul-lez-Durance (France); Saibene, G. [Fusion for Energy, c/Josep Pla 2, Torres Diagonal Litoral-B3, E-08019 Barcelona (Spain)

    2014-06-15

    The design of the ITER Electron Cyclotron Heating and Current Drive (EC H and CD) system has evolved in the last years both in goals and functionalities by considering an expanded range of applications. A large effort has been devoted to a better integration of the equatorial and the upper launchers, both from the point of view of the performance and of the design impact on the engineering constraints. However, from the analysis of the ECCD performance in two references H-mode scenarios at burn (the inductive H-mode and the advanced non-inductive scenario), it was clear that the EC power deposition was not optimal for steady-state applications in the plasma region around mid radius. An optimization study of the equatorial launcher is presented here aiming at removing this limitation of the EC system capabilities. Changing the steering of the equatorial launcher from toroidal to poloidal ensures EC power deposition out to the normalized toroidal radius ????0.6, and nearly doubles the EC driven current around mid radius, without significant performance degradation in the core plasma region. In addition to the improved performance, the proposed design change is able to relax some engineering design constraints on both launchers.

  6. Strings on Bubbling Geometries

    E-print Network

    Hai Lin; Alexander Morisse; Jonathan P. Shock

    2011-07-27

    We study gauge theory operators which take the form of a product of a trace with a Schur polynomial, and their string theory duals. These states represent strings excited on bubbling AdS geometries which are dual to the Schur polynomials. These geometries generically take the form of multiple annuli in the phase space plane. We study the coherent state wavefunction of the lattice, which labels the trace part of the operator, for a general Young tableau and their dual description on the droplet plane with a general concentric ring pattern. In addition we identify a density matrix over the coherent states on all the geometries within a fixed constraint. This density matrix may be used to calculate the entropy of a given ensemble of operators. We finally recover the BMN string spectrum along the geodesic near any circle from the ansatz of the coherent state wavefunction.

  7. Constrained Vapor Bubble

    NASA Technical Reports Server (NTRS)

    Huang, J.; Karthikeyan, M.; Plawsky, J.; Wayner, P. C., Jr.

    1999-01-01

    The nonisothermal Constrained Vapor Bubble, CVB, is being studied to enhance the understanding of passive systems controlled by interfacial phenomena. The study is multifaceted: 1) it is a basic scientific study in interfacial phenomena, fluid physics and thermodynamics; 2) it is a basic study in thermal transport; and 3) it is a study of a heat exchanger. The research is synergistic in that CVB research requires a microgravity environment and the space program needs thermal control systems like the CVB. Ground based studies are being done as a precursor to flight experiment. The results demonstrate that experimental techniques for the direct measurement of the fundamental operating parameters (temperature, pressure, and interfacial curvature fields) have been developed. Fluid flow and change-of-phase heat transfer are a function of the temperature field and the vapor bubble shape, which can be measured using an Image Analyzing Interferometer. The CVB for a microgravity environment, has various thin film regions that are of both basic and applied interest. Generically, a CVB is formed by underfilling an evacuated enclosure with a liquid. Classification depends on shape and Bond number. The specific CVB discussed herein was formed in a fused silica cell with inside dimensions of 3x3x40 mm and, therefore, can be viewed as a large version of a micro heat pipe. Since the dimensions are relatively large for a passive system, most of the liquid flow occurs under a small capillary pressure difference. Therefore, we can classify the discussed system as a low capillary pressure system. The studies discussed herein were done in a 1-g environment (Bond Number = 3.6) to obtain experience to design a microgravity experiment for a future NASA flight where low capillary pressure systems should prove more useful. The flight experiment is tentatively scheduled for the year 2000. The SCR was passed on September 16, 1997. The RDR is tentatively scheduled for October, 1998.

  8. A Comparison of Solar Cycle Variations in the Equatorial Rotation Rates of the Sun's Subsurface, Surface, Corona, and Sunspot Groups

    NASA Astrophysics Data System (ADS)

    Javaraiah, J.

    2013-10-01

    Using the Solar Optical Observing Network (SOON) sunspot-group data for the period 1985 - 2010, the variations in the annual mean equatorial-rotation rates of the sunspot groups are determined and compared with the known variations in the solar equatorial-rotation rates determined from the following data: i) the plasma rotation rates at 0.94R?,0.95R?,…,1.0R? measured by the Global Oscillation Network Group (GONG) during the period 1995 - 2010, ii) the data on the soft-X-ray corona determined from Yohkoh/SXT full-disk images for the years 1992 - 2001, iii) the data on small bright coronal structures (SBCS) that were traced in Solar and Heliospheric Observatory (SOHO)/EIT images during the period 1998 - 2006, and iv) the Mount Wilson Doppler-velocity measurements during the period 1986 - 2007. A large portion (up to ? 30? latitude) of the mean differential-rotation profile of the sunspot groups lies between those of the internal differential-rotation rates at 0.94R? and 0.98R?. The variation in the yearly mean equatorial-rotation rate of the sunspot groups seems to be lagging behind that of the equatorial-rotation rate determined from the GONG measurements by one to two years. The amplitude of the GONG measurements is very small. The solar-cycle variation in the equatorial-rotation rate of the solar corona closely matches that determined from the sunspot-group data. The variation in the equatorial-rotation rate determined from the Mount Wilson Doppler-velocity data closely resembles the corresponding variation in the equatorial-rotation rate determined from the sunspot-group data that included the values of the abnormal angular motions (> |3?| day-1) of the sunspot groups. Implications of these results are pointed out.

  9. Relationship between vertical ExB drift and F2-layer characteristics in the equatorial ionosphere at solar minimum conditions

    NASA Astrophysics Data System (ADS)

    Oyekola, Oyedemi S.

    2012-07-01

    Equatorial and low-latitude electrodynamics plays a dominant role in determining the structure and dynamics of the equatorial and low-latitude ionospheric F-region. Thus, they constitute essential input parameters for quantitative global and regional modeling studies. In this work, hourly median value of ionosonde measurements namely, peak height F2-layer (hmF2), F2-layer critical frequency (foF2) and propagation factor M(3000)F2 made at near equatorial dip latitude, Ouagadougou, Burkina Faso (12oN, 1.5oW; dip: 1.5oN) and relevant F2-layer parameters such as thickness parameter (Bo), electron temperature (Te), ion temperature (Ti), total electron content (TEC) and electron density (Ne, at the fixed altitude of 300 km) provided by the International Reference Ionosphere (IRI) model for the longitude of Ouagadougou are contrasted with the IRI vertical drift model to explore in detail the monthly climatological behavior of equatorial ionosphere and the effects of equatorial vertical plasma drift velocities on the diurnal structure of F2-layer parameters. The analysis period covers four months representative of solstitial and equinoctial seasonal periods during solar minimum year of 1987 for geomagnetically quiet-day. We show that month-by-month morphological patterns between vertical E×B drifts and F2-layer parameters range from worst to reasonably good and are largely seasonally dependent. A cross-correlation analysis conducted between equatorial drift and F2-layer characteristics yield statistically significant correlations for equatorial vertical drift and IRI-Bo, IRI-Te and IRI-TEC, whereas little or no acceptable correlation is obtained with observational evidence. Assessment of the association between measured foF2, hmF2 and M(3000)F2 illustrates consistent much more smaller correlation coefficients with no systematic linkage. In general, our research indicates strong departure from simple electrodynamically controlled behavior.

  10. Acoustic Propagation Through Clustered Bubble Clouds

    Microsoft Academic Search

    Thomas C. Weber; Anthony P. Lyons; David L. Bradley

    2007-01-01

    One of the underlying assumptions in the effective medium theory describing the propagation of acoustic waves through bubble clouds is that the probability of an individual bubble being located at some position in space is independent of the locations of other bubbles. However, bubbles within naturally occurring clouds may be influenced by the dynamics of the fluids in which they

  11. On sonoluminescence of an oscillating gas bubble

    Microsoft Academic Search

    Harvey P. Greenspan; Ali Nadim

    1993-01-01

    It is proposed that shock dynamics within the gas of a small bubble explains sonoluminescence—the emission of visible radiation in response to spherically symmetric, ultrasonic excitation of a gas bubble in a liquid. As the bubble radius oscillates, shock waves develop from spherical sound waves created inside the gas bubble. As any such shock propagates toward the center, it strengthens

  12. Physical Processes for Single Bubble Sonoluminescence

    Microsoft Academic Search

    Ho-Young Kwak; Jung Hee Na

    1997-01-01

    Analytic solutions for a sonoluminescing gas bubble have been obtained, which provide density, pressure and temperature distributions for the gas inside bubble oscillating under ultrasonic field. The solutions have revealed that sonoluminescence should occur just prior to the bubble collapse and its duration is less than 300 ps and that increase and subsequent rapid decrease in bubble wall acceleration induce

  13. Experiments with electron bubbles in liquid helium

    Microsoft Academic Search

    Ambarish Ghosh

    2005-01-01

    When a free electron is injected into liquid helium, it forms a microscopic bubble essentially free of helium atoms. The electron bubble is an excellent textbook example of a quantum mechanical particle confined in a potential well. The bubble is also a powerful tool to study superfluidity. In this dissertation, we describe various experiments on electron bubbles using standard ultrasonic

  14. Sonoluminescing Air Bubbles Rectify Argon

    SciTech Connect

    Lohse, D.; Hilgenfeldt, S. [Fachbereich Physik der Universitaet Marburg, Renthof 6, 35032 Marburg (Germany)] [Fachbereich Physik der Universitaet Marburg, Renthof 6, 35032 Marburg (Germany); Brenner, M.P. [Department of Mathematics, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139 (United States)] [Department of Mathematics, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139 (United States); Dupont, T.F. [Department of Computer Science, University of Chicago, Chicago, Illinois 60637 (United States)] [Department of Computer Science, University of Chicago, Chicago, Illinois 60637 (United States); Johnston, B. [Department of Physics, University of Chicago, Chicago, Illinois 60637 (United States)] [Department of Physics, University of Chicago, Chicago, Illinois 60637 (United States)

    1997-02-01

    The dynamics of single bubble sonoluminescence (SBSL) strongly depends on the percentage of inert gas within the bubble. We propose a theory for this dependence, based on a combination of principles from sonochemistry and hydrodynamic stability. The nitrogen and oxygen dissociation and subsequent reaction to water soluble gases implies that strongly forced air bubbles eventually consist of pure argon. Thus it is the partial argon (or any other inert gas) pressure which is relevant for stability. The theory provides quantitative explanations for many aspects of SBSL. {copyright} {ital 1997} {ital The American Physical Society}

  15. Hot Gas in the Circumstellar Bubble S308

    NASA Astrophysics Data System (ADS)

    Chu, You-Hua; Guerrero, Martín A.; Gruendl, Robert A.; García-Segura, Guillermo; Wendker, Heinrich J.

    2003-12-01

    S308 is a circumstellar bubble blown by the WN4 star HD 50896. It is one of the only two single-star bubbles that show detectable diffuse X-ray emission. We have obtained XMM-Newton EPIC observations of the northwest quadrant of S308. The diffuse X-ray emission shows a limb-brightened morphology, with a clear gap extending from the outer edge of the diffuse X-ray emission to the outer rim of the nebular shell. The X-ray spectrum of the diffuse emission is very soft and is well fitted by an optically thin plasma model for an N-enriched plasma at temperatures of ~1.1×106 K. A hotter gas component may exist but its temperature is not well constrained since it contributes less than 6% of the observed X-ray flux. The total X-ray luminosity of S308, extrapolated from the bright northwest quadrant, is <=(1.2+/-0.5)×1034 ergs s-1. We have used the observed bubble dynamics and the physical parameters of the hot interior gas of S308, in conjunction with the circumstellar bubble model of García-Segura & Mac Low, to demonstrate that the X-ray-emitting gas must be dominated by mixed-in nebular material.

  16. Dynamics Explorer observations of equatorial spread F - Evidence for drift waves

    NASA Technical Reports Server (NTRS)

    Hoegy, W. R.; Curtis, S. A.; Brace, L. H.; Maynard, N. C.; Heelis, R. A.

    1982-01-01

    Recent DE-2 data from the Langmuir probe, vector electric field, and ion drift meter instruments are employed to study equatorial spread F in the frequency regime of the low frequency drift and the lower hybrid drift instabilities. Strong electron density gradients topside equatorial F region correspond to regions of high electric field waves and large ion drift velocities. The electric field waves are seen in two distinct wavelength ranges which correspond to the parameter regimes of the low frequency drift and the lower hybrid drift instabilities. In the smaller of the two wavelength ranges the lower hybrid drift instability is found to be unstable, based on the ion drift velocity and the other plasma parameters measured on DE-2, and using published theory. Thus there is experimental evidence that the lower hybrid drift instability may produce the observed short wavelength waves without invoking a cascading mechanism.

  17. Progress of the ITER equatorial vis/IR wide angle viewing system optical design.

    PubMed

    Davi, M; Corre, Y; Guilhem, D; Jullien, F; Reichle, R; Salasca, S; Travère, J M; de la Cal, E; Manzanares, A; de Pablos, J L; Migozzi, J B

    2008-10-01

    The equatorial vis/IR wide angle viewing system is present in four ITER diagnostic equatorial ports. This instrument will cover a large field of view with high spatial and temporal resolutions, to provide real time temperature measurements of plasma facing components, spectral data in the visible range, information on runaway electrons, and pellet tracking. This diagnostic needs to be reliable, precise, and long lasting. Its design is driven by both the tokamak severe environment and the high performances required for machine protection. The preliminary design phase is ongoing. Paramount issues are being tackled, relative to wide spectral band optical design, material choice, and optomechanical difficulties due to the limited space available for this instrument in the ports, since many other diagnostics and services are also present. Recent progress of the diagnostic optical design and status of associated R&D are presented. PMID:19044654

  18. Aspherical bubble dynamics and oscillation times

    SciTech Connect

    Vogel, A.; Noack, J. [Meizinisches Laserzentrum Luebeck (Germany); Chapyak, E.J.; Godwin, R.P. [Los Alamos National Lab., NM (United States)

    1999-06-01

    The cavitation bubbles common in laser medicine are rarely perfectly spherical and are often located near tissue boundaries, in vessels, etc., which introduce aspherical dynamics. Here, novel features of aspherical bubble dynamics are explored by time-resolved photography and numerical simulations. The growth-collapse period of cylindrical bubbles of large aspect ratio (length:diameter {approximately}20) differs only slightly from twice the Rayleigh collapse time for a spherical bubble with an equivalent maximum volume. This fact justifies using the temporal interval between the acoustic signals emitted upon bubble creation and collapse to estimate the maximum bubble volume. As a result, hydrophone measurements can provide an estimate of the bubble size and energy even for aspherical bubbles. The change of the oscillation period of bubbles near solid walls and elastic (tissue-like) boundaries relative to that of isolated spherical bubbles is also investigated.

  19. Smashing Bubbles and Vanishing Sugar.

    ERIC Educational Resources Information Center

    Ward, Alan

    1979-01-01

    Science activities with soap bubbles for primary school children are described in this article. Another activity involves children in determining the whereabouts of sugar as it dissolves in water. (SA)

  20. Silicon-nitrogen coupling in the equatorial Pacific upwelling zone

    Microsoft Academic Search

    John P. Dunne; James W. Murray; Anthony K. Aufdenkampe; Stephane Blain; Martine Rodier

    1999-01-01

    We describe the role of diatoms on nitrogen and silicon cycling in the equatorial Pacific upwelling zone (EUZ) using water column nutrient data from 19 equatorial cruises and particle concentration, new production, and sediment trap data from the U.S. Joint Global Ocean Flux Study (JGOFS) equatorial Pacific (EqPac), France JGOFS fluxes in the Pacific (FLUPAC), and U.S. Zonal Flux cruises.

  1. Heating the bubbly gas of galaxy clusters with weak shocks and sound waves

    E-print Network

    S. Heinz; E. Churazov

    2005-09-26

    Using hydrodynamic simulations and a technique to extract the rotational component of the velocity field, we show how bubbles of relativistic gas inflated by AGN jets in galaxy clusters act as a catalyst, transforming the energy carried by sound and shock waves to heat. The energy is stored in a vortex field around the bubbles which can subsequently be dissipated. The efficiency of this process is set mainly by the fraction of the cluster volume filled by (sub-)kpc scale filaments and bubbles of relativistic plasma.

  2. Driving bubbles out of glass

    NASA Technical Reports Server (NTRS)

    Mattox, D. M.

    1981-01-01

    Surface tension gradient in melt forces gas bubbles to surface, increasing glass strength and transparency. Conventional chemical and buoyant fining are extremely slow in viscous glasses, but tension gradient method moves 250 um bubbles as rapidly as 30 um/s. Heat required for high temperature part of melt is furnished by stationary electrical or natural-gas heater; induction and laser heating are also possible. Method has many applications in industry processes.

  3. Oscillation of Droplets and Bubbles

    Microsoft Academic Search

    N. Ashgriz; M. Movassat

    \\u000a A liquid droplet may go through shape oscillation if it is forced out of its equilibrium spherical shape, while gas bubbles\\u000a undergo both shape and volume oscillations because they are compressible. This can happen when droplets and bubbles are exposed\\u000a to an external flow or an external force. Liquid droplet oscillation is observed during the atomization process when a liquid

  4. Lunar influence on equatorial atmospheric angular momentum

    NASA Astrophysics Data System (ADS)

    Bizouard, Christian; Zotov, Leonid; Sidorenkov, Nikolay

    2014-11-01

    This study investigates the relationship between the equatorial atmospheric angular momentum oscillation in the nonrotating frame and the quasi-diurnal lunar tidal potential. Between 2 and 30 days, the corresponding equatorial component, called Celestial Atmospheric Angular Momentum (CEAM), is mostly constituted of prograde circular motions, especially of a harmonic at 13.66 days, a sidelobe at 13.63 days, and of a weekly broadband variation. A simple equilibrium tide model explains the 13.66 day pressure term as a result of the O1 lunar tide. The powerful episodic fluctuations between 5 and 8 days possibly reflect an atmospheric normal mode excited by the tidal waves Q1 (6.86 days) and ?1 (7.095 days). The lunar tidal influence on the spectral band from 2 to 30 days is confirmed by two specific features, not occurring for seasonal band dominated by the solar thermal effect. First, Northern and Southern Hemispheres contribute equally and synchronously to the CEAM wind term. Second, the pressure and wind terms are proportional, which follows from angular momentum budget considerations where the topographic and friction torques on the solid Earth are much smaller than the one resulting from the equatorial bulge. Such a configuration is expected for the case of tidally induced circulation, where the surface pressure variation is tesseral and cannot contribute to the topographic torque, and tidal winds blow only at high altitudes. The likely effects of the lunar-driven atmospheric circulation on Earth's nutation are estimated and discussed in light of the present-day capabilities of space geodetic techniques.

  5. MACSAT - A Near Equatorial Earth Observation Mission

    NASA Astrophysics Data System (ADS)

    Kim, B. J.; Park, S.; Kim, E.-E.; Park, W.; Chang, H.; Seon, J.

    MACSAT mission was initiated by Malaysia to launch a high-resolution remote sensing satellite into Near Equatorial Orbit (NEO). Due to its geographical location, Malaysia can have large benefits from NEO satellite operation. From the baseline circular orbit of 685 km altitude with 7 degrees of inclination, the neighboring regions around Malaysian territory can be frequently monitored. The equatorial environment around the globe can also be regularly observed with unique revisit characteristics. The primary mission objective of MACSAT program is to develop and validate technologies for a near equatorial orbit remote sensing satellite system. MACSAT is optimally designed to accommodate an electro-optic Earth observation payload, Medium-sized Aperture Camera (MAC). Malaysian and Korean joint engineering teams are formed for the effective implementation of the satellite system. An integrated team approach is adopted for the joint development for MACSAT. MAC is a pushbroom type camera with 2.5 m of Ground Sampling Distance (GSD) in panchromatic band and 5 m of GSD in four multi-spectral bands. The satellite platform is a mini-class satellite. Including MAC payload, the satellite weighs under 200 kg. Spacecraft bus is designed optimally to support payload operations during 3 years of mission life. The payload has 20 km of swath width with +/- 30 o of tilting capability. 32 Gbits of solid state recorder is implemented as the mass image storage. The ground element is an integrated ground station for mission control and payload operation. It is equipped with S- band up/down link for commanding and telemetry reception as well as 30 Mbps class X-band down link for image reception and processing. The MACSAT system is capable of generating 1:25,000-scale image maps. It is also anticipated to have capability for cross-track stereo imaging for Digital elevation Model (DEM) generation.

  6. Modeling the Local Bubble

    NASA Astrophysics Data System (ADS)

    Cox, D. P.

    Modeling the Local Bubble is one of those activities fraught with danger. It is very easy to be too naive, to fail to consider the dependence of the model on assumptions about the nearby ambient state, or the likelihood of such a structure. It is similarly easy to become so caught up in the details of the vicinity that it is unclear where to begin a necessarily idealized modeling effort. And finally, it is important to remember that the data we have may in some cases be lying to us, and that we have not yet learned to read their facial expressions quite carefully enough. That said, I've tried in this paper to be helpful to those who may wish to take the risks. I surveyed the very most basic stories that the data seem to tell, and pointed out the standard coincidences that may be telling us a lot about what is happening, but may turn out once again to have been just coincidences. I've described 5 distinct conceptions that in one flavor or another pretty well survey the collection of mental images that have so far been carried by those who've attempted models. One may be right, or something entirely different may be more appropriate. It's at least vital to realize that a conception comes first, followed by a simplified model of details. I've also included a long list of questions directed at observers. Some have partial answers, some one wouldn't know today quite how to approach. But it is a list that students of the soft x-ray background, interstellar absorption lines, possible instrumentation, and the heliosphere may wish to review from time to time, just to see whether they can figure out how to be more helpful. There is another list for modelers, things the models must address, however-so-flimsily if necessary, because there are strong observational constraints (and stronger ones coming) on what can and cannot be present in the local ISM. To that I've added a few remarks concerning x-ray emission coming from beyond the Local Bubble, and another few on how x-ray emission from within the solar system might be contaminating what we see. That last bit is new, exciting, and possibly wrong, but it is an example of the ongoing wariness I believe one has to take toward the facts in the case. By the way, Dieter, it really was a great meeting.

  7. Bubbles and foams in microfluidics.

    PubMed

    Huerre, Axel; Miralles, Vincent; Jullien, Marie-Caroline

    2014-09-28

    Microfluidics offers great tools to produce highly-controlled dispersions of gas into liquid, from isolated bubbles to organized microfoams. Potential technological applications are manifold, from novel materials to scaffolds for tissue engineering or enhanced oil recovery. More fundamentally, microfluidics makes it possible to investigate the physics of complex systems such as foams at scales where the capillary forces become dominant, in model experiments involving few well-controlled parameters. In this context, this review does not have the ambition to detail in a comprehensive manner all the techniques and applications involving bubbles and foams in microfluidics. Rather, it focuses on particular consequences of working at the microscale, under confinement, and hopes to provide insight into the physics of such systems. The first part of this work focuses on bubbles, and more precisely on (i) bubble generation, where the confinement can suppress capillary instabilities while inertial effects may play a role, and (ii) bubble dynamics, paying special attention to the lubrication film between bubble and wall and the influence of confinement. The second part addresses the formation and dynamics of microfoams, emphasizing structural differences from macroscopic foams and the influence of the confinement. PMID:24913678

  8. Equatorial Oscillations in Jupiter's and Saturn's Atmospheres

    NASA Technical Reports Server (NTRS)

    Flasar, F. Michael; Guerlet, S.; Fouchet, T.; Schinder, P. J.

    2011-01-01

    Equatorial oscillations in the zonal-mean temperatures and zonal winds have been well documented in Earth's middle atmosphere. A growing body of evidence from ground-based and Cassini spacecraft observations indicates that such phenomena also occur in the stratospheres of Jupiter and Saturn. Earth-based midinfrared measurements spanning several decades have established that the equatorial stratospheric temperatures on Jupiter vary with a cycle of 4-5 years and on Saturn with a cycle of approximately 15 years. Spectra obtained by the Composite Infrared Spectrometer (CIRS) during the Cassini swingby at the end of 2000, with much better vertical resolution than the ground-based data, indicated a series of vertically stacked warm and cold anomalics at Jupiter's equator; a similar structurc was seen at Saturn's equator in CIRS limb measurements made in 2005, in the early phase of Cassini's orbital tour. The thermal wind equation implied similar patterns of mean zonal winds increasing and decreasing with altitude. On Saturn the peak-to-pcak amplitude of this variation was nearly 200 meters per second. The alternating vertical pattern of wanner and colder cquatorial tcmperatures and easterly and westerly tendencies of the zonal winds is seen in Earth's equatorial oscillations, where the pattern descends with time, The Cassini Jupiter and early Saturn observations were snapshots within a limited time interval, and they did not show the temporal evolution of the spatial patterns. However, more recent Saturn observations by CIRS (2010) and Cassini radio-occultation soundings (2009-2010) have provided an opportunity to follow the change of the temperature-zonal wind pattern, and they suggest there is descent, at a rate of roughly one scale height over four years. On Earth, the observed descent in the zonal-mean structure is associated with the absorption of a combination of vertically propagating waves with easlerly and westerly phase velocities. The peak-to-peak zonal wind amplitude in the oscillation pattern and the rate of descent constrain the absorbed wave flux of zonal momentum. On Saturn this is approximately 0.05 square meters per square seconds, which is comparable to if not greater than that associated with the terrestrial oscillations. We discuss possible candidates for the absorbed waves on Saturn. On Earth the wave forcing of the equatorial oscillation generales secondary circulations that can affcct the temperature and wind structure at latitudes well away from the equator, and we discuss possible evidence of that on Saturn.

  9. The equatorial electrojet satellite and surface comparison

    NASA Technical Reports Server (NTRS)

    Cain, J. C. (editor); Sweeney, R. E. (editor)

    1972-01-01

    The OGO 4 and 6 (POGO) magnetic field results for the equatorial electrojet indicate that while the present models are approximately correct, the possibility of a westward component must be incorporated. The scatter diagrams of POGO amplitudes and surface data show a correlation. The ratios between the amplitudes estimated from surface data and those at 400 km altitude are as follows: India 5 to 8, East Africa (Addis Ababa) 4, Central Africa 3, West Africa (Nigeria) 3, South America (Huancayo) 5, and Philippines 5. The variation in the ratio is due to the conductivity structure of the earth in various zones.

  10. An equatorial coronal hole at solar minimum

    NASA Technical Reports Server (NTRS)

    Bromage, B. J. I.; DelZanna, G.; DeForest, C.; Thompson, B.; Clegg, J. R.

    1997-01-01

    The large transequatorial coronal hole that was observed in the solar corona at the end of August 1996 is presented. It consists of a north polar coronal hole called the 'elephant's trunk or tusk'. The observations of this coronal hole were carried out with the coronal diagnostic spectrometer onboard the Solar and Heliospheric Observatory (SOHO). The magnetic field associated with the equatorial coronal hole is strongly connected to that of the active region at its base, resulting in the two features rotating at almost the same rate.

  11. Fading of Jupiter's South Equatorial Belt

    NASA Technical Reports Server (NTRS)

    Sola, Michael A.; Orton, Glenn; Baines, Kevin; Yanamandra-Fisher, Padma

    2011-01-01

    One of Jupiter's most dominant features, the South Equatorial Belt, has historically gone through a "fading" cycle. The usual dark, brownish clouds turn white, and after a period of time, the region returns to its normal color. Understanding this phenomenon, the latest occurring in 2010, will increase our knowledge of planetary atmospheres. Using the near infrared camera, NSFCAM2, at NASA's Infrared Telescope Facility in Hawaii, images were taken of Jupiter accompanied by data describing the circumstances of each observation. These images are then processed and reduced through an IDL program. By scanning the central meridian of the planet, graphs were produced plotting the average values across the central meridian, which are used to find variations in the region of interest. Calculations using Albert4, a FORTRAN program that calculates the upwelling reflected sunlight from a designated cloud model, can be used to determine the effects of a model atmosphere due to various absorption, scattering, and emission processes. Spectra that were produced show ammonia bands in the South Equatorial Belt. So far, we can deduce from this information that an upwelling of ammonia particles caused a cloud layer to cover up the region. Further investigations using Albert4 and other models will help us to constrain better the chemical make up of the cloud and its location in the atmosphere.

  12. Central Equatorial Pacific Experiment (CEPEX). Design document

    SciTech Connect

    Not Available

    1993-04-01

    The Earth`s climate has varied significantly in the past, yet climate records reveal that in the tropics, sea surface temperatures seem to have been remarkably stable, varying by less than a few degrees Celsius over geologic time. Today, the large warm pool of the western Pacific shows similar characteristics. Its surface temperature always exceeds 27{degree}C, but never 31{degree}C. Heightened interest in this observation has been stimulated by questions of global climate change and the exploration of stabilizing climate feedback processes. Efforts to understand the observed weak sensitivity of tropical sea surface temperatures to climate forcing has led to a number of competing ideas about the nature of this apparent thermostat. Although there remains disagreement on the processes that regulate tropical sea surface temperature, most agree that further progress in resolving these differences requires comprehensive field observations of three-dimensional water vapor concentrations, solar and infrared radiative fluxes, surface fluxes of heat and water vapor, and cloud microphysical properties. This document describes the Central Equatorial Pacific Experiment (CEPEX) plan to collect such observations over the central equatorial Pacific Ocean during March of 1993.

  13. The Centaurus A Northern Middle Lobe as a Buoyant Bubble

    E-print Network

    Curtis J. Saxton; Ralph S. Sutherland; Geoffrey V. Bicknell

    2001-07-30

    We model the northern middle radio lobe of Centaurus A (NGC 5128) as a buoyant bubble of plasma deposited by an intermittently active jet. The extent of the rise of the bubble and its morphology imply that the ratio of its density to that of the surrounding ISM is less than 10^{-2}, consistent with our knowledge of extragalactic jets and minimal entrainment into the precursor radio lobe. Using the morphology of the lobe to date the beginning of its rise through the atmosphere of Centaurus A, we conclude that the bubble has been rising for approximately 140Myr. This time scale is consistent with that proposed by Quillen et al. (1993) for the settling of post-merger gas into the presently observed large scale disk in NGC 5128, suggesting a strong connection between the delayed re-establishment of radio emission and the merger of NGC 5128 with a small gas-rich galaxy. This suggests a connection, for radio galaxies in general, between mergers and the delayed onset of radio emission. In our model, the elongated X-ray emission region discovered by Feigelson et al. (1981), part of which coincides with the northern middle lobe, is thermal gas that originates from the ISM below the bubble and that has been uplifted and compressed. The "large-scale jet" appearing in the radio images of Morganti et al. (1999) may be the result of the same pressure gradients that cause the uplift of the thermal gas, acting on much lighter plasma, or may represent a jet that did not turn off completely when the northern middle lobe started to buoyantly rise. We propose that the adjacent emission line knots (the "outer filaments") and star-forming regions result from the disturbance, in particular the thermal trunk, caused by the bubble moving through the extended atmosphere of NGC 5128.

  14. OH Production Enhancement in Bubbling Pulsed Discharges

    SciTech Connect

    Lungu, Cristian P.; Porosnicu, Corneliu; Jepu, Ionut; Chiru, Petrica; Zaroschi, Valentin; Lungu, Ana M. [National Institute for Laser, Plasma and Radiation Physics, Bucharest, 077125 (Romania); Saito, Nagahiro; Bratescu, Maria; Takai, Osamu [Ecotopia Science Institute, Nagoya University, Nagoya, 464-8603 (Japan); Velea, Theodor; Predica, Vasile [R and D National Institute for Nonferous and Rare Metals, Pantelimon, Jud. Ilfov, 077145 (Romania)

    2010-10-13

    The generation of active species, such as H{sub 2}O{sub 2}, O{sup *}, OH*, HO{sub 2}*, O{sub 3}, N{sub 2}{sup *}, etc, produced in aqueous solutions by HV pulsed discharges was studied in order to find the most efficient way in waste water treatment taking into account that these species are almost stronger oxidizers than ozone. Plasma was generated inside gas bubbles formed by the argon, air and oxygen gas flow between the special designed electrodes. The pulse width and pulse frequency influence was studied in order to increase the efficiency of the OH active species formation. The produced active species were investigated by optical emission spectroscopy and correlated with electrical parameters of the discharges (frequency, pulse width, amplitude, and rise and decay time).

  15. Bubble behavior in a Taylor vortex.

    PubMed

    Deng, Rensheng; Wang, Chi-Hwa; Smith, Kenneth A

    2006-03-01

    We present a study on the behavior of air bubbles captured in a Taylor vortex formed in the annulus between two concentric cylinders. It is found that small bubbles stay either at certain locations near the vortex cores or in the outflow regions along the inner cylinder. If bubbles of the same size are introduced, a variety of bubble structures (such as ring, chain, cluster, etc.) appear due to different mechanisms. For bubbles of nonuniform size, orbit crossing of small and large bubbles is observed. Droplets and particles can also be captured in Taylor vortices, and these exhibit certain unique features. PMID:16605650

  16. Subsurface ocean argon disequilibrium reveals the equatorial Pacific shadow zone

    E-print Network

    Archer, David

    Subsurface ocean argon disequilibrium reveals the equatorial Pacific shadow zone Eric Gehrie,1 outcrops in high latitudes. We present dissolved argon data that distinguishes a diapycnally ventilated), Subsurface ocean argon disequilibrium reveals the equatorial Pacific shadow zone, Geophys. Res. Lett., 33, L

  17. IRON PHOTOCHEMISTRY IN SEAWATER FROM THE EQUATORIAL PACIFIC

    EPA Science Inventory

    The photochemistry of iron in surface waters, and its implications to iron bioavailability, was examined on two cruises to the equatorial Pacific. ecktop incubations were performed with equatorial seawater to which iron was added in various chemical forms. esults showed clear diu...

  18. Synoptic Wave Perturbations and Convective Systems over Equatorial Africa

    Microsoft Academic Search

    Hanh Nguyen; Jean-Philippe Duvel

    2008-01-01

    Spectral analysis of the outgoing longwave radiation (OLR) time series over equatorial Africa reveals large oscillations of the convection with periods of between 3 and 6 days. In March and April, when the intertropical convergence zone (ITCZ) migrates northward and crosses equatorial Africa, this periodic behavior is most pronounced with a marked peak at 5-6 days. Robust horizontal and vertical

  19. Equatorial scintillation model. Technical report, 1 February 1983-30 April 1985

    SciTech Connect

    Fremouw, E.J.; Robins, R.E.

    1985-09-30

    Radiowave scintillation in the presence of natural and/or high-altitude nuclear disturbances has the potential to disrupt numerous transionospheric radio and radar systems. This report develops a model characterizing the plasma-density irregularities that produce scintillation in the naturally disturbed equatorial F layer. The model is incorporated into Program WBMOD along with subroutines for computing both link geometry and scintillation indices, the latter by means of phase screen diffraction theory. The model is based on similarly extensive analysis of wideband data from two equatorial stations. It describes irregularities at an effective height of 350 km that are isotropic across the geomagnetic field and elongated by a factor of 50 along the field and whose one-dimensional spatial power spectrum obeys a single-regime power law with a (negative) spectral index of 1.5. The height-integrated spectral strength of the irregularities is modeled as a function of solar epoch (sunspot number), the angle between the sunset terminator and the geomagnetic field line through the equatorial F layer point in question (a measure of seasonal and longitudinal variation), time after E-layer sunset on that field line, and the F-layer magnetic apex latitude of the point. The report also highlights a factor missing from complete characterization of the joint seasonal/longitudinal variation of scintillation, thought to depend upon thermospheric neutral winds.

  20. Observations of the generation of eastward equatorial electric fields near dawn

    NASA Astrophysics Data System (ADS)

    Kelley, M. C.; Rodrigues, F. S.; Pfaff, R. F.; Klenzing, J.

    2014-09-01

    We report and discuss interesting observations of the variability of electric fields and ionospheric densities near sunrise in the equatorial ionosphere made by instruments onboard the Communications/Navigation Outage Forecasting System (C/NOFS) satellite over six consecutive orbits. Electric field measurements were made by the Vector Electric Field Instrument (VEFI), and ionospheric plasma densities were measured by Planar Langmuir Probe (PLP). The data were obtained on 17 June 2008, a period of solar minimum conditions. Deep depletions in the equatorial plasma density were observed just before sunrise on three orbits, for which one of these depletions was accompanied by a very large eastward electric field associated with the density depletion, as previously described by de La Beaujardière et al. (2009), Su et al. (2009) and Burke et al. (2009). The origin of this large eastward field (positive upward/meridional drift), which occurred when that component of the field is usually small and westward, is thought to be due to a large-scale Rayleigh-Taylor process. On three subsequent orbits, however, a distinctly different, second type of relationship between the electric field and plasma density near dawn was observed. Enhancements of the eastward electric field were also detected, one of them peaking around 3 mV m-1, but they were found to the east (later local time) of pre-dawn density perturbations. These observations represent sunrise enhancements of vertical drifts accompanied by eastward drifts such as those observed by the San Marco satellite (Aggson et al., 1995). Like the San Marco measurements, the enhancements occurred during winter solstice and low solar flux conditions in the Pacific longitude sector. While the evening equatorial ionosphere is believed to present the most dramatic examples of variability, our observations exemplify that the dawn sector can be highly variable as well.

  1. Probing helium nano-bubble formation in tungsten with grazing incidence small angle x-ray scattering

    NASA Astrophysics Data System (ADS)

    Thompson, M.; Kluth, P.; Doerner, R. P.; Kirby, N.; Corr, C.

    2015-04-01

    Helium nano-bubble formation in plasma facing materials has emerged as a major concern for the next-step fusion experiment ITER, where helium plasmas will be used during the tokamak's start-up phase. Here, we demonstrate that grazing incidence small-angle x-ray scattering is a powerful technique for the analysis of helium nano-bubble formation in tungsten. We measured helium bubbles with sizes between 1.5–2.5 nm in tungsten exposed to helium plasma at 700 °C, where a smaller number of larger bubbles were also observed. Depth distributions can be estimated by taking successive measurements across a range of x-ray incidence angles. Compared with traditional approaches in the field, such as transmission electron microscopy, this technique provides information across a much larger volume with high statistical precision, whilst also being non-destructive.

  2. Shock formation within sonoluminescence bubbles

    SciTech Connect

    Vuong, V.Q. [University of California, Irvine, Department of Mechanical and Aerospace Engineering, Irvine, California 92697-3975 (United States)] [University of California, Irvine, Department of Mechanical and Aerospace Engineering, Irvine, California 92697-3975 (United States); Szeri, A.J. [University of California at Berkeley, Department of Mechanical Engineering, Berkeley, California 94720-1740 (United States)] [University of California at Berkeley, Department of Mechanical Engineering, Berkeley, California 94720-1740 (United States); Young, D.A. [Lawrence Livermore National Laboratory, Livermore, California 94550 (United States)] [Lawrence Livermore National Laboratory, Livermore, California 94550 (United States)

    1999-01-01

    A strong case has been made by several authors that sharp, spherically symmetric shocks converging on the center of a spherical bubble driven by a strong acoustic field give rise to rapid compression and heating that produces the brief flash of light known as sonoluminescence. The formation of such shocks is considered. It is found that, although at the main collapse the bubble wall does indeed launch an inwardly-traveling compression wave, and although the subsequent reflection of the wave at the bubble center produces a very rapid temperature peak, the wave is prevented from steepening into a sharp shock by an adverse gradient in the sound speed caused by heat transfer. It is shown that the mathematical characteristics of the flow can be prevented from accumulating into a shock front by this adverse sound speed gradient. A range of results is presented for a variety of bubble ambient radii and sound field amplitudes suggested by experiments. The time scale of the peak temperature in the bubble is set by the dynamics of the compression wave: this is typically in the range 100{endash}300 ps (FWHM) in concert with recent measurements of the sonoluminescence pulse width. {copyright} {ital 1999 American Institute of Physics.}

  3. Ethnic diversity deflates price bubbles

    PubMed Central

    Levine, Sheen S.; Apfelbaum, Evan P.; Bernard, Mark; Bartelt, Valerie L.; Zajac, Edward J.; Stark, David

    2014-01-01

    Markets are central to modern society, so their failures can be devastating. Here, we examine a prominent failure: price bubbles. Bubbles emerge when traders err collectively in pricing, causing misfit between market prices and the true values of assets. The causes of such collective errors remain elusive. We propose that bubbles are affected by ethnic homogeneity in the market and can be thwarted by diversity. In homogenous markets, traders place undue confidence in the decisions of others. Less likely to scrutinize others’ decisions, traders are more likely to accept prices that deviate from true values. To test this, we constructed experimental markets in Southeast Asia and North America, where participants traded stocks to earn money. We randomly assigned participants to ethnically homogeneous or diverse markets. We find a marked difference: Across markets and locations, market prices fit true values 58% better in diverse markets. The effect is similar across sites, despite sizeable differences in culture and ethnic composition. Specifically, in homogenous markets, overpricing is higher as traders are more likely to accept speculative prices. Their pricing errors are more correlated than in diverse markets. In addition, when bubbles burst, homogenous markets crash more severely. The findings suggest that price bubbles arise not only from individual errors or financial conditions, but also from the social context of decision making. The evidence may inform public discussion on ethnic diversity: it may be beneficial not only for providing variety in perspectives and skills, but also because diversity facilitates friction that enhances deliberation and upends conformity. PMID:25404313

  4. Data-driven numerical simulations of equatorial spread F in the Peruvian sector: 2. Autumnal equinox

    NASA Astrophysics Data System (ADS)

    Hysell, D. L.; Milla, M. A.; Condori, L.; Meriwether, J. W.

    2014-08-01

    An ongoing effort to simulate plasma instability in the equatorial ionosphere leading to equatorial spread F (ESF) in the American sector is described. Ionospheric state parameters including plasma number density and vector drift velocity profiles were measured at the Jicamarca Radio Observatory in the period between 20 September and 3 October 2013. Coherent radar backscatter from plasma irregularities was recorded simultaneously, and images of the irregularities were calculated using aperture synthesis methods. Neutral winds were measured by the red line Fabry-Perot interferometers at Jicamarca and Arequipa, Peru. A fully 3-D numerical simulation of ionospheric irregularities, initialized and forced using parameterizations derived from measurements and empirical models, was used to reproduce the ESF activity observed. Simulations were able to recover many of the features of the irregularities, although some important anomalies can be noted. ESF events in which the first appearance of radar plumes occurred either very early or very late were not reproduced in simulation and may be indicative of nonlocal influence.

  5. Gravity driven flows of bubble suspensions.

    NASA Astrophysics Data System (ADS)

    Zenit, Roberto; Koch, Donald L.; Sangani, Ashok K.

    1999-11-01

    Experiments on vertical and inclined channels were performed to study the behavior of a mono-dispersed bubble suspension for which the dual limit of large Reynolds number and small Weber number is satisfied. A uniform stream of 1.5 mm diameter bubbles is produced by a bank of identical capillaries and coalescence is inhibited by addition of salt to the water. Measurements of the liquid velocity and bubble-probe collision rate are obtained with a hot wire anemometer. The gas volume fraction, bubble velocity, velocity variance and chord length are measured using a dual impedance probe. Image analysis is used to quantify the distributions of bubble size and aspect ratio. For vertical channels the bubble velocity is observed to decrease as the bubble concentration increases in accord with the predictions of Spelt and Sangani (1998). The bubble velocity variance arises largely due to bubble-wall and bubble-bubble collisions. For inclined channels, the strength of the shear flow is controlled by the extent of bubble segregation and the effective viscosity of the bubble phase. The measurements are compared with solutions of the averaged equations of motion for a range of gas volume fractions and channel inclination angles.

  6. Direct numerical simulations of bidisperse bubbly flows

    NASA Astrophysics Data System (ADS)

    Bunner, Bernard; Göz, Manfred; Sommerfeld, Martin; Tryggvason, Gretar

    2001-11-01

    Three-dimensional direct numerical simulations of homogeneous bidisperse bubbly flows at finite Reynolds numbers are presented. A front-tracking/finite-difference method is used to accurately follow the motion of N1 large bubbles of volume V1 and N2 small bubbles of volume V_2. Periodic boundary conditions are used to approximate homogeneous flows. The effect of the interaction between the large bubbles and the small bubbles on the statistical properties of the flow is studied. These statistical properties include the rise velocity, fluctuation velocity, and dispersion cofficient of the bubbles as well as the fluctuation velocity and kinetic energy spectrum of the liquid. To characterize the respective position and motion of the bubbles, the pair probability density is examined. The void fraction ranges between 2% and 12%. Two cases are considered. In the first case, V_1=2V2 and N_1=N_2. The results are found to be quantitatively similar to the results of the monodisperse simulations. In the second case, V_1=8V2 and N1 < N_2. The results exhibit strong differences from the monodisperse simulation results. The small bubbles experience much higher fluctuations relative to their rise velocity tham the large bubbles. The liquid kinetic energy is larger than in the monodisperse case. It appears that the small bubbles hinder the motion of the large bubbles and the large bubbles pull the small bubbles along as they rise.

  7. VISUALIZATION OF SOAP BUBBLE GEOMETRIES Fred Almgren (mathematician)

    E-print Network

    Sullivan, John M.

    VISUALIZATION OF SOAP BUBBLE GEOMETRIES Fred Almgren (mathematician) Department of Mathematics ABSTRACT The authors discuss mathematical soap bubble problems and a new technique for generating computer soap bubble possesses an exquisite perfection of form. Soap bubbles are lovely physical manifestations

  8. Bubble Simulation Using Level Set-Boundary Element Method

    E-print Network

    Tan, Kiok Lim

    In bubble dynamics, an underwater bubble may evolve from being singly-connected to being toroidal. Furthermore, two or more individual bubbles may merge to form a single large bubble. These dynamics involve significant ...

  9. Observations of the Geopause at the Equatorial Magnetopause: Density and Temperature

    NASA Technical Reports Server (NTRS)

    Chandler, M. O.; Moore, T. E.

    2003-01-01

    Magnetic flux tubes containing plasmaspheric ion density and composition have been observed in the region between the classical plasmapause and the magnetopause. New observations show that these ion distributions exist at the equatorial, post-noon magnetopause. Comparison to observations of similar distributions at geosynchronous orbit and to simulations leads to the conclusion that these ions are convected from these regions to the magnetopause. This represents an extension of the geopause to the outer edge of the magnetosphere on the dayside. The presence of ion densities > 10 cu cm in this region must have profound impact on the nature of plasma processes that occur there.

  10. Bubbles Responding to Ultrasound Pressure

    NASA Technical Reports Server (NTRS)

    2003-01-01

    The Bubble and Drop Nonlinear Dynamics (BDND) experiment was designed to improve understanding of how the shape and behavior of bubbles respond to ultrasound pressure. By understanding this behavior, it may be possible to counteract complications bubbles cause during materials processing on the ground. This 12-second sequence came from video downlinked from STS-94, July 5 1997, MET:3/19:15 (approximate). The BDND guest investigator was Gary Leal of the University of California, Santa Barbara. The experiment was part of the space research investigations conducted during the Microgravity Science Laboratory-1R mission (STS-94, July 1-17 1997). Advanced fluid dynamics experiments will be a part of investigations plarned for the International Space Station. (435KB, 13-second MPEG, screen 160 x 120 pixels; downlinked video, higher quality not available) A still JPG composite of this movie is available at http://mix.msfc.nasa.gov/ABSTRACTS/MSFC-0300162.html.

  11. Statistical Analysis for VHF Radar Parameters at SÃO LUÍS, Jicamarca and Christmas Island Equatorial Stations

    NASA Astrophysics Data System (ADS)

    de la cruz cueva, R. Y.; Paula, E. R.; Kherani, E. A.

    2013-05-01

    Equatorial Spread F (ESF) is a manifestation of ionospheric interchange instabilities in the nighttime equatorial F region. These instabilities generate plasma density irregularities with scale sizes ranging from kilometers to thousands of kilometers. The irregularities can be detected from varieties of instruments such as digisonde, coherent and incoherent scatter radars, in situ space probes, and airglow photometers. In the present study, statistics of various aspects of spread F occurrence are presented from HF/VHF radar and incoherent scatter radar located at three equatorial stations: Christmas Island (2oN, 202.6oE, 2.9oN dip latitude, VHF radar), São Luís (2.59oS, 315.8oE, 0.5oS dip latitude, HF radar) and Jicamarca (12oS, 283.1oE, 0.6oN dip latitude, ISR). The radar parameters presented here are the onset altitude and onset time of the bottom-type and plume, and the peak altitude of the plume which are known to be associated with the spread F occurrence characteristics. The study reveals novel features namely, seasonal and solar flux dependence of spread F occurrence over Christmas island /São Luís, and longitudinal dependence of spread F occurrence characteristics from these three stations based on the chosen parameters. The importance of this work lies in the radar parameter empirical model developed combining statistical analysis of three equatorial and longitudinally separated stations, which is important to study the irregularity generation mechanisms, for space weather forecasting and nowcasting programs, and improving scintillation warning models. These parameters show generally linear correlation with solar flux index (F10.7 cm) and variation with season and magnetic declination angle. The fit correlation with F10.7cm is shown as useful information to implement one spread-F development empirical model based on small scale irregularities detected by VHF radars.

  12. Evidence for a Rayleigh-Taylor type instability and upwelling of depleted density regions during equatorial spread F

    NASA Technical Reports Server (NTRS)

    Kelley, M. C.; Haerendel, G.; Kappler, H.; Valenzuela, A.; Balsley, B. B.; Carter, D. A.; Ecklund, W. L.; Carlson, C. W.; Haeusler, B.; Torbert, R.

    1976-01-01

    Recent rocket probe, barium cloud and radar measurements conducted during equatorial spread F conditions are interpreted in terms of a Rayleigh-Taylor gravitational instability operating on the bottomside of the F peak. The persistent theoretical problems associated with strong radar echoes typically observed in patch-like structures at high altitudes are explained in terms of regions of depleted plasma density which buoyantly rise against the gravitational field.

  13. Upper tropospheric equatorial waves in ECMWF analyses

    NASA Technical Reports Server (NTRS)

    Randel, William J.

    1992-01-01

    An observational study is presented of travelling waves in the near-equatorial upper tropospheric wind field as revealed in operational analyses produced by the European Center for Medium-range Weather Forecasts (ECMWF) over the years 1980-1987. Space-time spectra are presented that reveal the seasonal and interannual variability of traveling waves in the tropical wind fields. The zonal wind spectra exhibit a majority of power in the lowest resolved frequencies, and there is a lack of notable spectral peaks. The upper tropospheric meridional wind spectra show maxima for westward-propagating zonal waves 4-7 with 6- to 10-day periods. The events are also longitudinally localized, with a preference for westward-propagating waves occurring over the eastern Pacific Ocean during August-September. The waves exhibit maximum amplitudes in the upper troposphere and weak coherence with the near-surface layers of the atmosphere.

  14. Equatorial anomeric triflates from mannuronic acid esters.

    PubMed

    Walvoort, Marthe T C; Lodder, Gerrit; Mazurek, Jaroslaw; Overkleeft, Herman S; Codée, Jeroen D C; van der Marel, Gijsbert A

    2009-09-01

    Activation of mannuronic acid esters leads to a conformational mixture of alpha-anomeric triflates, in which the equatorial triflate ((1)C(4) chair) is formed preferentially. This unexpected intermediate clearly opposes the anomeric effect and is mainly stabilized by the electron-withdrawing carboxylate function at C-5. Because the anomeric center carries a significant positive charge, the (1)C(4) mannopyranosyl chair approximates the favored (3)H(4) half-chair oxacarbenium ion conformation. The excellent beta-selectivity in glycosylations of mannuronates is postulated to originate from the cooperative action of the triflate counterion and the (stereo)electronic effects governing oxacarbenium ion stabilization in the transition state leading to the 1,2-cis product. PMID:19663422

  15. Three dimensional Visualization of Jupiter's Equatorial Region

    NASA Technical Reports Server (NTRS)

    1997-01-01

    Frames from a three dimensional visualization of Jupiter's equatorial region. The images used cover an area of 34,000 kilometers by 11,000 kilometers (about 21,100 by 6,800 miles) near an equatorial 'hotspot' similar to the site where the probe from NASA's Galileo spacecraft entered Jupiter's atmosphere on December 7th, 1995. These features are holes in the bright, reflective, equatorial cloud layer where warmer thermal emission from Jupiter's deep atmosphere can pass through. The circulation patterns observed here along with the composition measurements from the Galileo Probe suggest that dry air may be converging and sinking over these regions, maintaining their cloud-free appearance. The bright clouds to the right of the hotspot as well as the other bright features may be examples of upwelling of moist air and condensation.

    This frame is a view to the west, from between the cloud layers and over the patchy white clouds to the east of the hotspot. This is probably an area where moist convection is occurring over large horizontal distances, similar to the atmosphere over the equatorial ocean on Earth. The clouds are high and thick, and are observed to change rapidly over short time scales.

    Galileo is the first spacecraft to image Jupiter in near-infrared light (which is invisible to the human eye) using three filters at 727, 756, and 889 nanometers (nm). Because light at these three wavelengths is absorbed at different altitudes by atmospheric methane, a comparison of the resulting images reveals information about the heights of clouds in Jupiter's atmosphere. This information can be visualized by rendering cloud surfaces with the appropriate height variations.

    The visualization reduces Jupiter's true cloud structure to two layers. The height of a high haze layer is assumed to be proportional to the reflectivity of Jupiter at 889 nm. The height of a lower tropospheric cloud is assumed to be proportional to the reflectivity at 727 nm divided by that at 756 nm. This model is overly simplistic, but is based on more sophisticated studies of Jupiter's cloud structure. The upper and lower clouds are separated in the rendering by an arbitrary amount, and the height variations are exaggerated by a factor of 25.

    The lower cloud is colored using the same false color scheme used in previously released image products, assigning red, green, and blue to the 756, 727, and 889 nanometer mosaics, respectively. Light bluish clouds are high and thin, reddish clouds are low, and white clouds are high and thick. The dark blue hotspot in the center is a hole in the lower cloud with an overlying thin haze.

    The images used cover latitudes 1 to 10 degrees and are centered at longitude 336 degrees west. The smallest resolved features are tens of kilometers in size. These images were taken on December 17, 1996, at a range of 1.5 million kilometers (about 930,000 miles) by the Solid State Imaging (CCD) system on NASA's Galileo spacecraft.

    The Jet Propulsion Laboratory, Pasadena, CA manages the Galileo mission for NASA's Office of Space Science, Washington, DC. JPL is an operating division of California Institute of Technology (Caltech).

    This image and other images and data received from Galileo are posted on the World Wide Web, on the Galileo mission home page at URL http://galileo.jpl.nasa.gov.

  16. Bursting Bubbles and Bilayers

    PubMed Central

    Wrenn, Steven P.; Dicker, Stephen M.; Small, Eleanor F.; Dan, Nily R.; Mleczko, Micha?; Schmitz, Georg; Lewin, Peter A.

    2012-01-01

    This paper discusses various interactions between ultrasound, phospholipid monolayer-coated gas bubbles, phospholipid bilayer vesicles, and cells. The paper begins with a review of microbubble physics models, developed to describe microbubble dynamic behavior in the presence of ultrasound, and follows this with a discussion of how such models can be used to predict inertial cavitation profiles. Predicted sensitivities of inertial cavitation to changes in the values of membrane properties, including surface tension, surface dilatational viscosity, and area expansion modulus, indicate that area expansion modulus exerts the greatest relative influence on inertial cavitation. Accordingly, the theoretical dependence of area expansion modulus on chemical composition - in particular, poly (ethylene glyclol) (PEG) - is reviewed, and predictions of inertial cavitation for different PEG molecular weights and compositions are compared with experiment. Noteworthy is the predicted dependence, or lack thereof, of inertial cavitation on PEG molecular weight and mole fraction. Specifically, inertial cavitation is predicted to be independent of PEG molecular weight and mole fraction in the so-called mushroom regime. In the “brush” regime, however, inertial cavitation is predicted to increase with PEG mole fraction but to decrease (to the inverse 3/5 power) with PEG molecular weight. While excellent agreement between experiment and theory can be achieved, it is shown that the calculated inertial cavitation profiles depend strongly on the criterion used to predict inertial cavitation. This is followed by a discussion of nesting microbubbles inside the aqueous core of microcapsules and how this significantly increases the inertial cavitation threshold. Nesting thus offers a means for avoiding unwanted inertial cavitation and cell death during imaging and other applications such as sonoporation. A review of putative sonoporation mechanisms is then presented, including those involving microbubbles to deliver cargo into a cell, and those - not necessarily involving microubbles - to release cargo from a phospholipid vesicle (or reverse sonoporation). It is shown that the rate of (reverse) sonoporation from liposomes correlates with phospholipid bilayer phase behavior, liquid-disordered phases giving appreciably faster release than liquid-ordered phases. Moreover, liquid-disordered phases exhibit evidence of two release mechanisms, which are described well mathematically by enhanced diffusion (possibly via dilation of membrane phospholipids) and irreversible membrane disruption, whereas liquid-ordered phases are described by a single mechanism, which has yet to be positively identified. The ability to tune release kinetics with bilayer composition makes reverse sonoporation of phospholipid vesicles a promising methodology for controlled drug delivery. Moreover, nesting of microbubbles inside vesicles constitutes a truly “theranostic” vehicle, one that can be used for both long-lasting, safe imaging and for controlled drug delivery. PMID:23382772

  17. Bubble memory module for spacecraft application

    NASA Technical Reports Server (NTRS)

    Hayes, P. J.; Looney, K. T.; Nichols, C. D.

    1985-01-01

    Bubble domain technology offers an all-solid-state alternative for data storage in onboard data systems. A versatile modular bubble memory concept was developed. The key module is the bubble memory module which contains all of the storage devices and circuitry for accessing these devices. This report documents the bubble memory module design and preliminary hardware designs aimed at memory module functional demonstration with available commercial bubble devices. The system architecture provides simultaneous operation of bubble devices to attain high data rates. Banks of bubble devices are accessed by a given bubble controller to minimize controller parts. A power strobing technique is discussed which could minimize the average system power dissipation. A fast initialization method using EEPROM (electrically erasable, programmable read-only memory) devices promotes fast access. Noise and crosstalk problems and implementations to minimize these are discussed. Flight memory systems which incorporate the concepts and techniques of this work could now be developed for applications.

  18. Behavior of Rapidly Sheared Bubble Suspensions

    NASA Technical Reports Server (NTRS)

    Sangani, A. S.; Kushch, V. I.; Hoffmann, M.; Nahra, H.; Koch, D. L.; Tsang, Y.

    2002-01-01

    An experiment to be carried out aboard the International Space Station is described. A suspension consisting of millimeter-sized bubbles in water containing some dissolved salt, which prevents bubbles from coalescing, will be sheared in a Couette cylindrical cell. Rotation of the outer cylinder will produce centrifugal force which will tend to accumulate the bubbles near the inner wall. The shearing will enhance collisions among bubbles creating thereby bubble phase pressure that will resist the tendency of the bubbles to accumulate near the inner wall. The bubble volume fraction and velocity profiles will be measured and compared with the theoretical predictions. Ground-based research on measurement of bubble phase properties and flow in vertical channel are described.

  19. TECHNOLOGY ASSESSMENT OF FINE BUBBLE AERATORS

    EPA Science Inventory

    This technology assessment addresses design and evaluation of fine bubble aeration equipment. It discusses the associated gas transfer theory used as the basis for measuring water and wastewater oxygenation efficiency. Mixing requirements are also discussed. While bubble aeration...

  20. Unorthodox bubbles when boiling in cold water

    NASA Astrophysics Data System (ADS)

    Parker, Scott; Granick, Steve

    2014-01-01

    High-speed movies are taken when bubbles grow at gold surfaces heated spotwise with a near-infrared laser beam heating water below the boiling point (60-70 °C) with heating powers spanning the range from very low to so high that water fails to rewet the surface after bubbles detach. Roughly half the bubbles are conventional: They grow symmetrically through evaporation until buoyancy lifts them away. Others have unorthodox shapes and appear to contribute disproportionately to heat transfer efficiency: mushroom cloud shapes, violently explosive bubbles, and cavitation events, probably stimulated by a combination of superheating, convection, turbulence, and surface dewetting during the initial bubble growth. Moreover, bubbles often follow one another in complex sequences, often beginning with an unorthodox bubble that stirs the water, followed by several conventional bubbles. This large dataset is analyzed and discussed with emphasis on how explosive phenomena such as cavitation induce discrepancies from classical expectations about boiling.

  1. Unorthodox bubbles when boiling in cold water.

    PubMed

    Parker, Scott; Granick, Steve

    2014-01-01

    High-speed movies are taken when bubbles grow at gold surfaces heated spotwise with a near-infrared laser beam heating water below the boiling point (60-70?°C) with heating powers spanning the range from very low to so high that water fails to rewet the surface after bubbles detach. Roughly half the bubbles are conventional: They grow symmetrically through evaporation until buoyancy lifts them away. Others have unorthodox shapes and appear to contribute disproportionately to heat transfer efficiency: mushroom cloud shapes, violently explosive bubbles, and cavitation events, probably stimulated by a combination of superheating, convection, turbulence, and surface dewetting during the initial bubble growth. Moreover, bubbles often follow one another in complex sequences, often beginning with an unorthodox bubble that stirs the water, followed by several conventional bubbles. This large dataset is analyzed and discussed with emphasis on how explosive phenomena such as cavitation induce discrepancies from classical expectations about boiling. PMID:24580324

  2. Temperature Nonequilibration during Single-Bubble Sonoluminescence

    E-print Network

    Suslick, Kenneth S.

    Temperature Nonequilibration during Single-Bubble Sonoluminescence David J. Flannigan*, and Kenneth Information ABSTRACT: Single-bubble sonoluminescence (SBSL) spectra from liquids having low vapor pressures the observation and quantification of nonequilibrated temperatures during sonoluminescence. For SBSL from aqueous

  3. Colliding bubble universes in eternal inflation

    E-print Network

    Thomas, Nathaniel C. (Nathaniel Cabot)

    2011-01-01

    We briefly summarize arguments for inflation and discuss eternal inflation. We then discuss the motion of domain walls and null shells that form in two-bubble collision processes in both the global and in-bubble FRW ...

  4. Oscillating bubbles in ultrasonic acoustic field

    NASA Astrophysics Data System (ADS)

    Matsumoto, K.; Ueno, I.

    2009-02-01

    Behavior of oscillating bubbles is of fundamental study for acoustic cavitations, and is of great importance for medical field. For example, angiographic and diagnosis of cancer of liver. We focused on behavior of multiple air bubbles exposed to ultrasonic wave. The bubbles were injected into the static water from a vertical capillary tube, and then the ultrasonic wave of 20 kHz was applied from above toward the bubbles. Vibrating motion of the bubbles was captured by a high-speed camera at frame rates up to 45000 fps. Excitations of surface wave and shape oscillation with distinct mode number were realized. Correlation between the accelerated bubble behavior and the bubble-bubble distance.

  5. Removal of hydrogen bubbles from nuclear reactors

    NASA Technical Reports Server (NTRS)

    Jenkins, R. V.

    1980-01-01

    Method proposed for removing large hydrogen bubbles from nuclear environment uses, in its simplest form, hollow spheres of palladium or platinum. Methods would result in hydrogen bubble being reduced in size without letting more radioactivity outside reactor.

  6. Climatic trends of the equatorial undercurrent: A backup mechanism for sustaining the equatorial Pacific production

    NASA Astrophysics Data System (ADS)

    Ruggio, Raffaele; Vichi, Marcello; Paparella, Francesco; Masina, Simona

    2013-07-01

    The Equatorial Undercurrent (EUC) is the major source of iron to the equatorial Pacific and it is sensitive to climatic changes as other components of the tropical Pacific. This work proposes a methodology based on a Lagrangian approach aimed at understanding the changes in the transport of iron rich waters to the EUC in a future climate change scenario, using climate model data from an Earth system model. A selected set of regions from the northern and southern extra-equatorial Pacific has been chosen. These regions are characterized by the presence of iron sources from continental shelf processes like the Papua New Guinea region and atmospheric deposition like the northern subtropical gyre. The trajectories that reach the EUC during the 20th and the 21st century departing from these areas have been analyzed using a set of statistics designed to determine variations in the amount of transport and in the travel times of the water masses. The transport of waters to the EUC from the north Pacific subtropical gyre and from the Bismarck Sea is projected to increase during the 21st century. The increase is particularly significant for water masses from the northern subtropical gyre, with travel times lower than 10 years in the second half of the 21st century. This increased interaction between the extra-tropics and the EUC may bring additional iron-rich waters in the high-nutrient low-chlorophyll region of the equatorial Pacific compatibly with the significant increase of the simulated net primary production found in the biogeochemical model, thus partly offsetting the anticipated decrease of production implied by the surface warming.

  7. Initial thermal plasma observations from ISEE-1

    NASA Technical Reports Server (NTRS)

    Baugher, C. R.; Chappell, C. R.; Horwitz, J. L.; Shelley, E. G.; Young, D. T.

    1980-01-01

    The initial measurements of magnetospheric thermal ions by the Plasma Composition Experiment on ISEE-1 are presented to demonstrate the surprising variety in this plasma population. The data provide evidence that the adiabatic mapping of the high latitude ionosphere to the equatorial plasma trough provides an insufficient description of the origin, transport, and accumulation processes which supply low energy ions to the outer plasmasphere and plasma trough.

  8. The QUEST Large-Area Equatorial Survey

    NASA Astrophysics Data System (ADS)

    Coppi, P.; Snyder, J.; QUEST Collaboration

    1999-12-01

    The QUEST (Quasar Equatorial Survey Team) collaboration, a joint venture between Yale University, Indiana University, and CIDA in Venezuela, has instrumented the focal plane of the 1m CIDA Schmidt telescope with an 8k x 8k CCD mosaic camera. The camera operates in driftscan mode, covering a 300 sq.deg. (2.4ox120o) swath of sky in one night. Using filters, we obtain up to 4 colors per object simultaneously, and using the telescope's 3.2o objective prism, we obtain slitless (10-30 Angstroms resolution) spectra for all objects. With the current version of the instrument, the equatorial sky between ? =+/- 6o is accessible ( 2000 sq.deg. in a typical season). The camera is well-suited for large-area objective prism and variability studies. We present an overview of the camera and data system, and highlight some of our first science results. These include: the detection of the optical afterglow from a gamma-ray burst with a 2 degree radius error box only 3 hours after the event; the detection of new, faint (mb 18-19) RR Lyrae stars; a multi-band, multi-epoch survey of the entire Orion OB1 association ( 120 sq.deg.) to V?< 20, in order to obtain a comprehensive census of the low mass young stellar population (down to 0.2\\> Msun); and a 700 sq. deg H? emission line catalog containing 700 objects with redshifts 0

  9. The good, the bad and the bubbly. Micro bubble behavior under ultrasound.

    E-print Network

    Greenaway, Alan

    The good, the bad and the bubbly. Micro bubble behavior under ultrasound. Michael Conneely Division of Physics The good, the bad and the bubbly. Micro bubble behavior under ultrasound. PaLS Open Day 2013 #12] microsecond behaviour of microbubbles in Ultrasound fields. · Direct relevance across therapeutic

  10. Numerical simulations of single bubble sonoluminescence

    SciTech Connect

    Mourad, P.D. (Appl. Phys. Lab., Univ. of Washington, Seattle, WA 98195 (United States)); Marcus, D.L. (Lawrence Livermore Natl. Lab., Livermore, CA 94551 (United States)); Roy, R.A.; Matula, T.J. (Univ. of Washington, Seattle, WA 98195 (United States))

    1994-11-01

    A higher-order Godunov method is used to solve the spherically symmetric, compressible Euler equations with an ideal gas equation of state as a model for single bubble sonoluminescence. Basic shock physics is discussed in this context, exploring how modeled variations of the bubble interior support or suppress the generation and propagation of shock waves within the bubble as well as the interaction of a shock with the bubble interface. [Work supported by ONR through the ONR/ARL program.

  11. Multicompartment hydrodynamic model for slurry bubble columns

    Microsoft Academic Search

    Ion Iliuta; Damien Desvigne; Jérôme Anfray; Nicolas Dromard; Daniel Schweich

    2008-01-01

    A core-annulus multicompartment two-dimensional two-bubble class model accounting for slurry recirculation and coupled with catalyst transport was developed as a part and parcel of the analysis of the behavior of slurry bubble column reactors at high gas throughputs corresponding to the churn turbulent flow regime. The model analyzed the contributions of bubble-induced turbulence closures, bubble coalescence and breakup phenomena, and

  12. Silent bubbles - Their effects and detection

    NASA Technical Reports Server (NTRS)

    Powell, Michael R.

    1990-01-01

    This paper discusses the concept of the 'silent bubble' (a phenomenon due to gas phase formation in tissues, which does not lead to frank decompression sickness). Special attention is given to the conditions for silent bubbles formation, the methods of their detecton, and to their pathophysiology. Data relating the gas formation in blood and the symptoms of decompression sickness indicate that the distinction between the silent bubbles and clinical ones is often vague and that a bubble-free decompression never existed.

  13. Soap bubbles in paintings: Art and science

    Microsoft Academic Search

    F. Behroozi

    2008-01-01

    Soap bubbles became popular in 17th century paintings and prints primarily as a metaphor for the impermanence and fragility of life. The Dancing Couple (1663) by the Dutch painter Jan Steen is a good example which, among many other symbols, shows a young boy blowing soap bubbles. In the 18th century the French painter Jean-Simeon Chardin used soap bubbles not

  14. BUBBLE COMPUTATION, GRANULAR TEMPERATURES, AND REYNOLDS STRESSES

    Microsoft Academic Search

    Jonghwun Jung; Dimitri Gidaspow; Isaac K. Gamwo

    2006-01-01

    Bubbles were simulated in a two-dimensional fluidized bed with a constant inlet velocity using two computer codes, the IIT code and the MFIX code. The computational results were compared to the Jung et al. (2005) experiments in a thin bubbling bed of 530 ?m glass beads. The use of higher order numerics produces better bubble resolution due to smaller numerical diffusion.

  15. Black hole formation from colliding bubbles

    E-print Network

    Ian G. Moss

    1994-05-21

    Some indication of conditions that are necessary for the formation of black holes from the collision of bubbles during a supercooled phase transition in the the early universe are explored. Two colliding bubbles can never form a black hole. Three colliding bubbles can refocus the energy in their walls to the extent that it becomes infinite.

  16. Shock Wave Emissions of a Sonoluminescing Bubble

    Microsoft Academic Search

    Joachim Holzfuss; Matthias Ruggeberg; Andreas Billo

    1998-01-01

    A single bubble in water is excited by a standing ultrasound wave. At high intensity the bubble starts to emit light. Together with the emitted light pulse, a shock wave is generated in the liquid at collapse time. The time-dependent velocity of the outward-travelling shock is measured with an imaging technique. The pressure in the shock and in the bubble

  17. 25 July 2002 Sonoluminescence: Bubble power

    E-print Network

    Suslick, Kenneth S.

    25 July 2002 Sonoluminescence: Bubble power When a gas bubble in a liquid is excited by ultrasonic. These flashes of light, known as 'sonoluminescence', occur as the bubble implodes, or cavitates. Now Didenko­397 (2002); doi:10.1038/nature00895 | First Paragraph | Full Text (HTML / PDF) | Sonoluminescence: Inside

  18. Alternative model of single-bubble sonoluminescence

    Microsoft Academic Search

    Kyuichi Yasui

    1997-01-01

    A model of single-bubble sonoluminescence (SBSL) is constructed. In the model, the temperature is assumed to be spatially uniform inside the bubble except at the thermal boundary layer near the bubble wall even at the strong collapse based on the theoretical results of Kwak and Na [Phys. Rev. Lett. 77, 4454 (1996)]. In the model, the effect of the kinetic

  19. Hydrodynamic Solutions for a Sonoluminescing Gas Bubble

    Microsoft Academic Search

    Ho-Young Kwak; Jung Hee Na

    1996-01-01

    Analytic solutions for a sonoluminescing gas bubble have been obtained, which provide density, pressure, and temperature distributions for the gas inside a bubble oscillating under an ultrasonic field. The solutions show that sonoluminescence occurs due to the increase and subsequent decrease in bubble wall acceleration which induces a thermal spike. It also turns out that the number of electrons ionized,

  20. Passive acoustic analysis of complex bubbly flows

    Microsoft Academic Search

    Richard Manasseh

    2004-01-01

    A technique for extracting data from a complex bubbly flow is reviewed, beginning with fundamental laboratory and theoretical developments of the method and ending with an illustration of the technique in practice. Passive bubble acoustics involves 'listening' to the sounds naturally emitted by bubbles and exploiting these data to infer properties of the system. In many industrial plants, the multiphase

  1. Tetrad bubble domain chip arrangement for multiplexing

    NASA Technical Reports Server (NTRS)

    Almasi, G. S.

    1973-01-01

    Rotating magnetic field of bubble domain memory is used to obtain time-division multiplexing of bubble domain circuits into quadrants. Memory bits are assigned on bit-per-chip rather than bit-per-module basis; power is reduced by circulating only portion of bubbles at a time.

  2. Bubbularium: See the Colors in Bubbles

    NSDL National Science Digital Library

    2012-06-26

    With little more than a flashlight, a straw, and a plastic lid, make an observatory so you can see the amazing colors in bubbles. Learn about how light travels in waves and how the frequency of a light wave determines which color you see. The activity also has a recipe for "bubble juice" so you'll have some bubbles to work with.

  3. Heliospheric plasma sheets N. U. Crooker,1

    E-print Network

    California at Berkeley, University of

    sheet (HPS) encasing the heliospheric current sheet shows a high degree of variability. A study of 52 that only half concur with both high-beta plasma and current sheets, as required for an HPS. The remaining et al. [1990a] designated the heliospheric plasma sheet (HPS) as the equatorial solar wind sandwiched

  4. Data collapse of the spectra of water-based stable single-bubble sonoluminescence

    SciTech Connect

    Levinsen, Mogens T. [BioComplexity Laboratory, Niels Bohr Institute, Blegdamsvej 17, DK-2100 Copenhagen O (Denmark)

    2010-09-15

    In the early days of stable single-bubble sonoluminescence, it was strongly debated whether the emission was blackbody radiation or whether the bubble was transparent to its own radiation (volume emission). Presently, the volume emission picture is nearly universally accepted. We present new measurements of spectra with apparent color temperatures ranging from 6000 to 21 000 K. We show through data collapse that within experimental uncertainty, apart from a constant, the spectra of strongly driven stable single-bubble sonoluminescence in water can be written as the product between a universal function of wavelength and a functional form that only depends on wavelength and apparent temperature but has no reference to any other parameter specific to the experimental situation. This remarkable result does question our theoretical understanding of the state of the plasma in the interior of strongly driven stable sonoluminescent bubbles.

  5. Upscaling energy concentration in multifrequency single-bubble sonoluminescence with strongly degassed sulfuric acid.

    PubMed

    Dellavale, Damián; Rechiman, Ludmila; Rosselló, Juan Manuel; Bonetto, Fabián

    2012-07-01

    Single-bubble sonoluminescence (SBSL) was explored under a variety of multifrequency excitations. In particular, biharmonic excitation was used to produce SBSL for unprecedented low dissolved noble gas concentrations in a sulfuric acid solution. Reducing the amount of dissolved noble gas makes it possible to reach higher acoustic pressures on the SL bubble, which otherwise are not attainable because of the Bjerknes instability. By using biharmonic excitation, we were able to experimentally trap and to spatially stabilize SL bubbles for xenon pressure overhead as low as 1 mbar. As a result, we have access to regions in phase space where the plasma temperatures are higher than the ones reached before for bubbles driven at ?30 kHz. PMID:23005538

  6. Data collapse of the spectra of water-based stable single-bubble sonoluminescence.

    PubMed

    Levinsen, Mogens T

    2010-09-01

    In the early days of stable single-bubble sonoluminescence, it was strongly debated whether the emission was blackbody radiation or whether the bubble was transparent to its own radiation (volume emission). Presently, the volume emission picture is nearly universally accepted. We present new measurements of spectra with apparent color temperatures ranging from 6000 to 21?000 K. We show through data collapse that within experimental uncertainty, apart from a constant, the spectra of strongly driven stable single-bubble sonoluminescence in water can be written as the product between a universal function of wavelength and a functional form that only depends on wavelength and apparent temperature but has no reference to any other parameter specific to the experimental situation. This remarkable result does question our theoretical understanding of the state of the plasma in the interior of strongly driven stable sonoluminescent bubbles. PMID:21230187

  7. Upscaling energy concentration in multifrequency single-bubble sonoluminescence with strongly degassed sulfuric acid

    NASA Astrophysics Data System (ADS)

    Dellavale, Damián; Rechiman, Ludmila; Rosselló, Juan Manuel; Bonetto, Fabián

    2012-07-01

    Single-bubble sonoluminescence (SBSL) was explored under a variety of multifrequency excitations. In particular, biharmonic excitation was used to produce SBSL for unprecedented low dissolved noble gas concentrations in a sulfuric acid solution. Reducing the amount of dissolved noble gas makes it possible to reach higher acoustic pressures on the SL bubble, which otherwise are not attainable because of the Bjerknes instability. By using biharmonic excitation, we were able to experimentally trap and to spatially stabilize SL bubbles for xenon pressure overhead as low as 1mbar. As a result, we have access to regions in phase space where the plasma temperatures are higher than the ones reached before for bubbles driven at ?30kHz.

  8. Powering of cool filaments in cluster cores by buoyant bubbles - I. Qualitative model

    NASA Astrophysics Data System (ADS)

    Churazov, E.; Ruszkowski, M.; Schekochihin, A.

    2013-11-01

    Cool-core clusters (e.g. Perseus or M87) often possess a network of bright gaseous filaments, observed in radio, infrared, optical and X-ray bands. We propose that these filaments are powered by the reconnection of the magnetic field in the wakes of buoyant bubbles. Active galactic nucleus (AGN)-inflated bubbles of relativistic plasma rise buoyantly in the cluster atmosphere, stretching and amplifying the field in the wake to values of ? = 8?Pgas/B2 ˜ 1. The field lines in the wake have opposite directions and are forced together as the bubble motion stretches the filament. This setup bears strong similarity to the coronal loops on the Sun or to the Earth's magnetotail. The reconnection process naturally explains both the required level of local dissipation rate in filaments and the overall luminosity of filaments. The original source of power for the filaments is the potential energy of buoyant bubbles, inflated by the central AGN.

  9. Role of acoustic-gravity waves in generating equatorial ionospheric irregularities

    SciTech Connect

    Argo, P.E.

    1980-01-01

    Irregularities in the equatorial ionospheric plasma (F-layer) have been observed and studied for many years. Even so, the creation mechanisms have successfully remained a source of controversy for equally many years. This is mainly due to the difficulty in observing the irregularities, because in situ measurements give a spatial trace at a near single time, while radio observations have tended to give a series of height profiles with changing time. One mechanism is the spatial resonance amplification of traveling ionospheric disturbance (TIDs) generated by acoustic gravity waves. As the wave profile in the plasma steepens, the stored energy begins to release through the Rayleigh-Taylor instability, which then creates a spectrum of smaller scale irregularities. In this dissertation the interaction of the acoustic gravity wave and the ionospheric plasma are examined, and it is found that the above mechanism is indeed feasible. In Chapter 3, the interaction between a neutral wave and the plasma is quantified, and the condiions for growth of resonant plasma waves is established. These conditions are met during the post-sunset period near the geomagnetic equator, which is exactly when and where the irregularities are encountered. For irregularity generation the Rayleigh-Taylor mechanism requires a steep positive gradient of density - a fact that previously has seemed to be impossible on the topside of the F-layer. However, in this thesis it is shown that acoustic gravity waves can generate positive slopes even on the topsideF-layer. Consequently, acoustic gravity waves constitute a single mechanism that can be used to explain both bottomside and topside irregularities. Experimental evidence for the creation of equatorial ionospheric irregularities by acoustic gravity waves has been sparse, although wavelike structures appear to permeate the irregularity profiles.

  10. Pulling bubbles from a bath

    E-print Network

    Kao, Justin C. T.

    Deposition of bubbles on a wall withdrawn from a liquid bath is a phenomenon observed in many everyday situations—the foam lacing left behind in an emptied glass of beer, for instance. It is also of importance to the many ...

  11. The Coming Law School Bubble

    ERIC Educational Resources Information Center

    Krauss, Michael I.

    2011-01-01

    In this article, the author explains how forty years of politicized hiring in the law schools has left its destructive mark. The results are potentially catastrophic: Market forces and internal law school policies may be combining to produce a legal education bubble the likes of which the country has never seen. (Contains 11 footnotes.)

  12. Models of cylindrical bubble pulsation

    PubMed Central

    Ilinskii, Yurii A.; Zabolotskaya, Evgenia A.; Hay, Todd A.; Hamilton, Mark F.

    2012-01-01

    Three models are considered for describing the dynamics of a pulsating cylindrical bubble. A linear solution is derived for a cylindrical bubble in an infinite compressible liquid. The solution accounts for losses due to viscosity, heat conduction, and acoustic radiation. It reveals that radiation is the dominant loss mechanism, and that it is 22 times greater than for a spherical bubble of the same radius. The predicted resonance frequency provides a basis of comparison for limiting forms of other models. The second model considered is a commonly used equation in Rayleigh-Plesset form that requires an incompressible liquid to be finite in extent in order for bubble pulsation to occur. The radial extent of the liquid becomes a fitting parameter, and it is found that considerably different values of the parameter are required for modeling inertial motion versus acoustical oscillations. The third model was developed by V. K. Kedrinskii [Hydrodynamics of Explosion (Springer, New York, 2005), pp. 23–26] in the form of the Gilmore equation for compressible liquids of infinite extent. While the correct resonance frequency and loss factor are not recovered from this model in the linear approximation, it provides reasonable agreement with observations of inertial motion. PMID:22978863

  13. Electrolysis Bubbles Make Waterflow Visible

    NASA Technical Reports Server (NTRS)

    Schultz, Donald F.

    1990-01-01

    Technique for visualization of three-dimensional flow uses tiny tracer bubbles of hydrogen and oxygen made by electrolysis of water. Strobe-light photography used to capture flow patterns, yielding permanent record that is measured to obtain velocities of particles. Used to measure simulated mixing turbulence in proposed gas-turbine combustor and also used in other water-table flow tests.

  14. Bubble-driven inertial micropump

    NASA Astrophysics Data System (ADS)

    Torniainen, Erik D.; Govyadinov, Alexander N.; Markel, David P.; Kornilovitch, Pavel E.

    2012-12-01

    The fundamental action of the bubble-driven inertial micropump is investigated. The pump has no moving parts and consists of a thermal resistor placed asymmetrically within a straight channel connecting two reservoirs. Using numerical simulations, the net flow is studied as a function of channel geometry, resistor location, vapor bubble strength, fluid viscosity, and surface tension. Two major regimes of behavior are identified: axial and non-axial. In the axial regime, the drive bubble either remains inside the channel, or continues to grow axially when it reaches the reservoir. In the non-axial regime, the bubble grows out of the channel and in all three dimensions while inside the reservoir. The net flow in the axial regime is parabolic with respect to the hydraulic diameter of the channel cross-section, but in the non-axial regime it is not. From numerical modeling, it is determined that the net flow is maximal when the axial regime crosses over to the non-axial regime. To elucidate the basic physical principles of the pump, a phenomenological one-dimensional model is developed and solved. A linear array of micropumps has been built using silicon-SU8 fabrication technology that is used to manufacture thermal inkjet printheads. Semi-continuous pumping across a 2 mm-wide channel has been demonstrated experimentally. Measured net flow with respect to viscosity variation is in excellent agreement with simulation results.

  15. Animation of Bubbles in Liquid

    Microsoft Academic Search

    Jeong-mo Hong; Chang-hun Kim

    2003-01-01

    We present a new fluid animation technique in which liquid and gas interact with each other, using the example of bubbles rising in water. In contrast to previous studies which only focused on one fluid, our system considers both the liquid and the gas simultaneously. In addition to the flowing motion, the interactions between liquid and gas cause buoyancy, surface

  16. Neutron Detection via Bubble Chambers

    SciTech Connect

    Jordan, David V.; Ely, James H.; Peurrung, Anthony J.; Bond, Leonard J.; Collar, J. I.; Flake, Matthew; Knopf, Michael A.; Pitts, W. K.; Shaver, Mark W.; Sonnenschein, Andrew; Smart, John E.; Todd, Lindsay C.

    2005-10-06

    The results of a Pacific Northwest National Laboratory (PNNL) exploratory research project investigating the feasibility of fast neutron detection using a suitably prepared and operated, pressure-cycled bubble chamber are described. The research was conducted along two parallel paths. Experiments with a slow pressure-release Halon chamber at the Enrico Fermi Institute at the University of Chicago showed clear bubble nucleation sensitivity to an AmBe neutron source and insensitivity to the 662 keV gammas from a 137Cs source. Bubble formation was documented via high-speed (1000 frames/sec) photography, and the acoustic signature of bubble formation was detected using a piezo-electric transducer element mounted on the base of the chamber. The chamber’s neutron sensitivity as a function of working fluid temperature was mapped out. The second research path consisted of the design, fabrication, and testing of a fast pressure-release Freon-134a chamber at PNNL. The project concluded with successful demonstrations of the PNNL chamber’s AmBe neutron source sensitivity and 137Cs gamma insensitivity. The source response tests of the PNNL chamber were documented with high-speed photography.

  17. Breaking waves, turbulence and bubbles

    NASA Astrophysics Data System (ADS)

    Gemmrich, Johannes; Vagle, Svein; Thomson, Jim

    2014-05-01

    The air-sea fluxes of heat, momentum, and gases are to a large extent affected by wave-induced turbulence in the near-surface ocean layer, and are generally increased over the fluxes in a law-of-the-wall type boundary layer. However, air-bubbles generated during the wave breaking process may affect the density stratification and in turn reduce turbulence intensity in the near-surface layer. The turbulence field beneath surface waves is rather complex and provides great challenges for detailed observations. We obtained high resolution near-surface velocity profiles, bubble cloud measurements and video recordings of the breaking activity in a coastal strait. Conditions ranged from moderate to strong wind forcing with wind speed ranging from 5 m/s to 20 m/s. Estimates of the dissipation rates of turbulence kinetic energy are calculated from the in-situ velocity measurements. We find dissipation rates, fluctuating by more than two orders of magnitude, are closely linked to the air-fraction associated with micro-bubbles. Combining these turbulence estimates and the bubble cloud characteristics we infer differences in the strength of wave breaking and its effect on wave-induced mixing and air-sea exchange processes.

  18. Affirmative Discrimination and the Bubble

    ERIC Educational Resources Information Center

    Clegg, Roger

    2011-01-01

    In this essay, the author discusses how affirmative action contributed to an unnatural rise in enrollments in college. In considering the higher education bubble, he makes the case that as the opposition to preferences continues to build, the momentum of this trend will only increase as funding shrinks. He offers some tentative answers to a series…

  19. The Trouble With Bubble Gum

    NSDL National Science Digital Library

    Richard Konicek-Moran

    2010-03-12

    Most students are totally unaware of the amount of sugar in bubble gum and don't know that they are literally eating sugar in huge amounts. In this chapter, the author is concerned with finding out what happens to the weight of gum when it is chewed, whic

  20. Phase and coherence of longitudinally separated equatorial ionospheric scintillation

    NASA Astrophysics Data System (ADS)

    Shume, E. B.; Mannucci, A. J.

    2013-12-01

    This paper presents the first calculation of phase and coherence of cross-wavelet transform applied on longitudinally separated VHF and L-band equatorial ionospheric scintillation. The cross-wavelet analysis has utilized scintillation observations made over equatorial South America and Christmas Island. Part of the results of this study has been reported recently in the Geophysical Research Letters by Shume and Mannucci (2013). The phase and coherence analysis were employed on pairs of scintillation observations separated by longitudes thereby to develop VHF and L-band scintillation (and equatorial spread F) forecast tools west of observation sites.

  1. Plasma Clouds in the Magnetosphere

    Microsoft Academic Search

    S. E. DeForest; C. E. McIlwain

    1971-01-01

    Previous equatorial observations of the magnetospheric plasma [Gringauz, 1961; Frank, 1967 a, b, c, 1970; Vasyliunas, 19'6.8; Frank and Owens, 1970] have been made from spacecraft that made rapid but infrequent traversals of the region between 5 and 20 Rr or, as for the Vela spacecraft Bame et al., 1967], remained at great distances. The ATS I observations [Freeman and

  2. The Degradation of Organic Pollutants by Bubble Discharge in Water

    NASA Astrophysics Data System (ADS)

    Zhu, Linan; Wang, Yongjun; Ren, Zhijun; Liu, Guifang; Kang, Kai

    2013-10-01

    Organic pollutants could be degraded by using bubble discharge in water with gas aeration in the discharge reactor and more plasma can be generated in the discharge process. When pulsed high voltage was applied between electrodes with gas aerated into the reactor, it showed that bubbles were broken, which meant that breakdown took place. It could also be observed that the removal rate of phenol increased with increasing discharge voltage or pulse frequency, and with reducing initial phenol concentration or solution electric conductivity. It could remove more amount of phenol by oxygen aeration. With increasing oxygen flow rate, the removal rate increased. There was little difference with air or nitrogen aeration for phenol removal. The solution temperature after discharge increased to a great extent. However, this part of energy consumption did not contribute to the reaction, which led to a reduction in the energy utilization efficiency.

  3. Theory of supercompression of vapor bubbles and nanoscale thermonuclear fusion

    SciTech Connect

    Nigmatulin, Robert I.; Akhatov, Iskander Sh.; Topolnikov, Andrey S.; Bolotnova, Raisa Kh.; Vakhitova, Nailya K.; Lahey, Richard T. Jr.; Taleyarkhan, Rusi P. [Institute of Mechanics, Ufa Branch of the Russian Academy of Sciences, 6 Karl Marx Street, Ufa 450000 (Russian Federation); Department of Mechanical, Aerospace, and Nuclear Engineering, Rensselaer Polytechnic Institute, 110 8th Street, Troy, New York 12180-3590 (United States); School of Nuclear Engineering, Purdue University, West Lafayette, Indiana 47907-1290 (United States)

    2005-10-01

    This paper provides the theoretical basis for energetic vapor bubble implosions induced by a standing acoustic wave. Its primary goal is to describe, explain, and demonstrate the plausibility of the experimental observations by Taleyarkhan et al. [Science 295, 1868 (2002); Phys. Rev. E 69, 036109 (2004)] of thermonuclear fusion for imploding cavitation bubbles in chilled deuterated acetone. A detailed description and analysis of these data, including a resolution of the criticisms that have been raised, together with some preliminary HYDRO code simulations, has been given by Nigmatulin et al. [Vestnik ANRB (Ufa, Russia) 4, 3 (2002); J. Power Energy 218-A, 345 (2004)] and Lahey et al. [Adv. Heat Transfer (to be published)]. In this paper a hydrodynamic shock (i.e., HYDRO) code model of the spherically symmetric motion for a vapor bubble in an acoustically forced liquid is presented. This model describes cavitation bubble cluster growth during the expansion period, followed by a violent implosion during the compression period of the acoustic cycle. There are two stages of the bubble dynamics process. The first, low Mach number stage, comprises almost all the time of the acoustic cycle. During this stage, the radial velocities are much less than the sound speeds in the vapor and liquid, the vapor pressure is very close to uniform, and the liquid is practically incompressible. This process is characterized by the inertia of the liquid, heat conduction, and the evaporation or condensation of the vapor. The second, very short, high Mach number stage is when the radial velocities are the same order, or higher, than the sound speeds in the vapor and liquid. In this stage high temperatures, pressures, and densities of the vapor and liquid take place. The model presented herein has realistic equations of state for the compressible liquid and vapor phases, and accounts for nonequilibrium evaporation/condensation kinetics at the liquid/vapor interface. There are interacting shock waves in both phases, which converge toward and reflect from the center of the bubble, causing dissociation, ionization, and other related plasma physics phenomena during the final stage of bubble collapse. For a vapor bubble in a deuterated organic liquid (e.g., acetone), during the final stage of collapse there is a nanoscale region (diameter {approx}100 nm) near the center of the bubble in which, for a fraction of a picosecond, the temperatures and densities are extremely high ({approx}10{sup 8} K and {approx}10 g/cm{sup 3}, respectively) such that thermonuclear fusion may take place. To quantify this, the kinetics of the local deuterium/deuterium (D/D) nuclear fusion reactions was used in the HYDRO code to determine the intensity of the fusion reactions. Numerical HYDRO code simulations of the bubble implosion process have been carried out for the experimental conditions used by Taleyarkhan et al. [Science 295, 1868 (2002); Phys. Rev. E 69, 036109 (2004)] at Oak Ridge National Laboratory. The results show good agreement with the experimental data on bubble fusion that was measured in chilled deuterated acetone.

  4. Bubble Universe Dynamics After Free Passage

    E-print Network

    Pontus Ahlqvist; Kate Eckerle; Brian Greene

    2014-12-26

    We consider bubble collisions in single scalar field theories with multiple vacua. Recent work has argued that at sufficiently high impact velocities, collisions between such bubble vacua are governed by 'free passage' dynamics in which field interactions can be ignored during the collision, providing a systematic process for populating local minima without quantum nucleation. We focus on the time period that follows the bubble collision and provide evidence that, for certain potentials, interactions can drive significant deviations from the free-passage bubble profile, thwarting the production of bubbles with different field values.

  5. Bubble departure size in flow boiling

    NASA Astrophysics Data System (ADS)

    Guan, Peng; Jia, Li; Yin, Liaofei; Tan, Zetao

    2014-12-01

    Flow boiling experiments were conducted in a vertical annular channel to study bubble departure characteristics. Deionized water was used as the working fluid, and the tests were performed at atmospheric pressure. Bubble departure diameters were obtained from the images which were captured by a high-speed digital camera. The relationship between bubble contact diameter and departure diameter was discussed. A new model base on force balance analysis, taking bubble contact diameter into account for predicting bubble departure diameter is proposed in this study. A good agreement between predicted and measured results is achieved.

  6. Bubble Universe Dynamics After Free Passage

    NASA Astrophysics Data System (ADS)

    Ahlqvist, Pontus; Eckerle, Kate; Greene, Brian

    2015-03-01

    We consider bubble collisions in single scalar field theories with multiple vacua. Recent work has argued that at sufficiently high impact velocities, collisions between such bubble vacua are governed by `free passage' dynamics in which field interactions can be ignored during the collision, providing a systematic process for populating local minima without quantum nucleation. We focus on the time period that follows the bubble collision and provide evidence that, for certain potentials, interactions can drive significant deviations from the free-passage bubble profile, thwarting the production of bubbles with different field values.

  7. Three dimensional Visualization of Jupiter's Equatorial Region

    NASA Technical Reports Server (NTRS)

    1997-01-01

    Frames from a three dimensional visualization of Jupiter's equatorial region. The images used cover an area of 34,000 kilometers by 11,000 kilometers (about 21,100 by 6,800 miles) near an equatorial 'hotspot' similar to the site where the probe from NASA's Galileo spacecraft entered Jupiter's atmosphere on December 7th, 1995. These features are holes in the bright, reflective, equatorial cloud layer where warmer thermal emission from Jupiter's deep atmosphere can pass through. The circulation patterns observed here along with the composition measurements from the Galileo Probe suggest that dry air may be converging and sinking over these regions, maintaining their cloud-free appearance. The bright clouds to the right of the hotspot as well as the other bright features may be examples of upwelling of moist air and condensation.

    This frame is a view to the northeast, from between the cloud layers and above the streaks in the lower cloud leading towards the hotspot. The hotspot is clearly visible as a deep blue feature. The cloud streaks end near the hotspot, consistent with the idea that clouds traveling along these streak lines descend and evaporate as they approach the hotspot. The upper haze layer is slightly bowed upwards above the hotspot.

    Galileo is the first spacecraft to image Jupiter in near-infrared light (which is invisible to the human eye) using three filters at 727, 756, and 889 nanometers (nm). Because light at these three wavelengths is absorbed at different altitudes by atmospheric methane, a comparison of the resulting images reveals information about the heights of clouds in Jupiter's atmosphere. This information can be visualized by rendering cloud surfaces with the appropriate height variations.

    The visualization reduces Jupiter's true cloud structure to two layers. The height of a high haze layer is assumed to be proportional to the reflectivity of Jupiter at 889 nm. The height of a lower tropospheric cloud is assumed to be proportional to the reflectivity at 727 nm divided by that at 756 nm. This model is overly simplistic, but is based on more sophisticated studies of Jupiter's cloud structure. The upper and lower clouds are separated in the rendering by an arbitrary amount, and the height variations are exaggerated by a factor of 25.

    The lower cloud is colored using the same false color scheme used in previously released image products, assigning red, green, and blue to the 756, 727, and 889 nanometer mosaics, respectively. Light bluish clouds are high and thin, reddish clouds are low, and white clouds are high and thick. The dark blue hotspot in the center is a hole in the lower cloud with an overlying thin haze.

    The images used cover latitudes 1 to 10 degrees and are centered at longitude 336 degrees west. The smallest resolved features are tens of kilometers in size. These images were taken on December 17, 1996, at a range of 1.5 million kilometers (about 930,000 miles) by the Solid State Imaging (CCD) system on NASA's Galileo spacecraft.

    The Jet Propulsion Laboratory, Pasadena, CA manages the Galileo mission for NASA's Office of Space Science, Washington, DC. JPL is an operating division of California Institute of Technology (Caltech).

    This image and other images and data received from Galileo are posted on the World Wide Web, on the Galileo mission home page at URL http://www.jpl.nasa.gov/ galileo.

  8. Three dimensional Visualization of Jupiter's Equatorial Region

    NASA Technical Reports Server (NTRS)

    1997-01-01

    Frames from a three dimensional visualization of Jupiter's equatorial region. The images used cover an area of 34,000 kilometers by 11,000 kilometers (about 21,100 by 6,800 miles) near an equatorial 'hotspot' similar to the site where the probe from NASA's Galileo spacecraft entered Jupiter's atmosphere on December 7th, 1995. These features are holes in the bright, reflective, equatorial cloud layer where warmer thermal emission from Jupiter's deep atmosphere can pass through. The circulation patterns observed here along with the composition measurements from the Galileo Probe suggest that dry air may be converging and sinking over these regions, maintaining their cloud-free appearance. The bright clouds to the right of the hotspot as well as the other bright features may be examples of upwelling of moist air and condensation.

    This frame is a view to the southeast, from between the cloud layers and over the north center of the region. The tall white clouds in the lower cloud deck are probably much like large terrestrial thunderclouds. They may be regions where atmospheric water powers vertical convection over large horizontal distances.

    Galileo is the first spacecraft to image Jupiter in near-infrared light (which is invisible to the human eye) using three filters at 727, 756, and 889 nanometers (nm). Because light at these three wavelengths is absorbed at different altitudes by atmospheric methane, a comparison of the resulting images reveals information about the heights of clouds in Jupiter's atmosphere. This information can be visualized by rendering cloud surfaces with the appropriate height variations.

    The visualization reduces Jupiter's true cloud structure to two layers. The height of a high haze layer is assumed to be proportional to the reflectivity of Jupiter at 889 nm. The height of a lower tropospheric cloud is assumed to be proportional to the reflectivity at 727 nm divided by that at 756 nm. This model is overly simplistic, but is based on more sophisticated studies of Jupiter's cloud structure. The upper and lower clouds are separated in the rendering by an arbitrary amount, and the height variations are exaggerated by a factor of 25.

    The lower cloud is colored using the same false color scheme used in previously released image products, assigning red, green, and blue to the 756, 727, and 889 nanometer mosaics, respectively. Light bluish clouds are high and thin, reddish clouds are low, and white clouds are high and thick. The dark blue hotspot in the center is a hole in the lower cloud with an overlying thin haze.

    The images used cover latitudes 1 to 10 degrees and are centered at longitude 336 degrees west. The smallest resolved features are tens of kilometers in size. These images were taken on December 17, 1996, at a range of 1.5 million kilometers (about 930,000 miles) by the Solid State Imaging (CCD) system on NASA's Galileo spacecraft.

    The Jet Propulsion Laboratory, Pasadena, CA manages the Galileo mission for NASA's Office of Space Science, Washington, DC. JPL is an operating division of California Institute of Technology (Caltech).

    This image and other images and data received from Galileo are posted on the World Wide Web, on the Galileo mission home page at URL http://www.jpl.nasa.gov/ galileo.

  9. Three dimensional Visualization of Jupiter's Equatorial Region

    NASA Technical Reports Server (NTRS)

    1997-01-01

    Frames from a three dimensional visualization of Jupiter's equatorial region. The images used cover an area of 34,000 kilometers by 11,000 kilometers (about 21,100 by 6,800 miles) near an equatorial 'hotspot' similar to the site where the probe from NASA's Galileo spacecraft entered Jupiter's atmosphere on December 7th, 1995. These features are holes in the bright, reflective, equatorial cloud layer where warmer thermal emission from Jupiter's deep atmosphere can pass through. The circulation patterns observed here along with the composition measurements from the Galileo Probe suggest that dry air may be converging and sinking over these regions, maintaining their cloud-free appearance. The bright clouds to the right of the hotspot as well as the other bright features may be examples of upwelling of moist air and condensation.

    This frame is a view from the southwest looking northeast, from an altitude just above the high haze layer. The streaks in the lower cloud leading towards the hotspot are visible. The upper haze layer is mostly flat, with notable small peaks that can be matched with features in the lower cloud. In reality, these areas may represent a continuous vertical cloud column.

    Galileo is the first spacecraft to image Jupiter in near-infrared light (which is invisible to the human eye) using three filters at 727, 756, and 889 nanometers (nm). Because light at these three wavelengths is absorbed at different altitudes by atmospheric methane, a comparison of the resulting images reveals information about the heights of clouds in Jupiter's atmosphere. This information can be visualized by rendering cloud surfaces with the appropriate height variations.

    The visualization reduces Jupiter's true cloud structure to two layers. The height of a high haze layer is assumed to be proportional to the reflectivity of Jupiter at 889 nm. The height of a lower tropospheric cloud is assumed to be proportional to the reflectivity at 727 nm divided by that at 756 nm. This model is overly simplistic, but is based on more sophisticated studies of Jupiter's cloud structure. The upper and lower clouds are separated in the rendering by an arbitrary amount, and the height variations are exaggerated by a factor of 25.

    The lower cloud is colored using the same false color scheme used in previously released image products, assigning red, green, and blue to the 756, 727, and 889 nanometer mosaics, respectively. Light bluish clouds are high and thin, reddish clouds are low, and white clouds are high and thick. The dark blue hotspot in the center is a hole in the lower cloud with an overlying thin haze.

    The images used cover latitudes 1 to 10 degrees and are centered at longitude 336 degrees west. The smallest resolved features are tens of kilometers in size. These images were taken on December 17, 1996, at a range of 1.5 million kilometers (about 930,000 miles) by the Solid State Imaging (CCD) system on NASA's Galileo spacecraft.

    The Jet Propulsion Laboratory, Pasadena, CA manages the Galileo mission for NASA's Office of Space Science, Washington, DC. JPL is an operating division of California Institute of Technology (Caltech).

    This image and other images and data received from Galileo are posted on the World Wide Web, on the Galileo mission home page at URL http://galileo.jpl.nasa.gov.

  10. Three dimensional Visualization of Jupiter's Equatorial Region

    NASA Technical Reports Server (NTRS)

    1997-01-01

    Frames from a three dimensional visualization of Jupiter's equatorial region. The images used cover an area of 34,000 kilometers by 11,000 kilometers (about 21,100 by 6,800 miles) near an equatorial 'hotspot' similar to the site where the probe from NASA's Galileo spacecraft entered Jupiter's atmosphere on December 7th, 1995. These features are holes in the bright, reflective, equatorial cloud layer where warmer thermal emission from Jupiter's deep atmosphere can pass through. The circulation patterns observed here along with the composition measurements from the Galileo Probe suggest that dry air may be converging and sinking over these regions, maintaining their cloud-free appearance. The bright clouds to the right of the hotspot as well as the other bright features may be examples of upwelling of moist air and condensation.

    This frame is a view from above and to the south of the visualized area, showing the entire model. The entire region is overlain by a thin, transparent haze. In places the haze is high and thick, especially to the east (to the right of) the hotspot.

    Galileo is the first spacecraft to image Jupiter in near-infrared light (which is invisible to the human eye) using three filters at 727, 756, and 889 nanometers (nm). Because light at these three wavelengths is absorbed at different altitudes by atmospheric methane, a comparison of the resulting images reveals information about the heights of clouds in Jupiter's atmosphere. This information can be visualized by rendering cloud surfaces with the appropriate height variations.

    The visualization reduces Jupiter's true cloud structure to two layers. The height of a high haze layer is assumed to be proportional to the reflectivity of Jupiter at 889 nm. The height of a lower tropospheric cloud is assumed to be proportional to the reflectivity at 727 nm divided by that at 756 nm. This model is overly simplistic, but is based on more sophisticated studies of Jupiter's cloud structure. The upper and lower clouds are separated in the rendering by an arbitrary amount, and the height variations are exaggerated by a factor of 25.

    The lower cloud is colored using the same false color scheme used in previously released image products, assigning red, green, and blue to the 756, 727, and 889 nanometer mosaics, respectively. Light bluish clouds are high and thin, reddish clouds are low, and white clouds are high and thick. The dark blue hotspot in the center is a hole in the lower cloud with an overlying thin haze.

    The images used cover latitudes 1 to 10 degrees and are centered at longitude 336 degrees west. The smallest resolved features are tens of kilometers in size. These images were taken on December 17, 1996, at a range of 1.5 million kilometers (about 930,000 miles) by the Solid State Imaging (CCD) system on NASA's Galileo spacecraft.

    The Jet Propulsion Laboratory, Pasadena, CA manages the Galileo mission for NASA's Office of Space Science, Washington, DC. JPL is an operating division of California Institute of Technology (Caltech).

    This image and other images and data received from Galileo are posted on the World Wide Web, on the Galileo mission home page at URL http://www.jpl.nasa.gov/ galileo.

  11. Three dimensional Visualization of Jupiter's Equatorial Region

    NASA Technical Reports Server (NTRS)

    1997-01-01

    Frames from a three dimensional visualization of Jupiter's equatorial region. The images used cover an area of 34,000 kilometers by 11,000 kilometers (about 21,100 by 6,800 miles) near an equatorial 'hotspot' similar to the site where the probe from NASA's Galileo spacecraft entered Jupiter's atmosphere on December 7th, 1995. These features are holes in the bright, reflective, equatorial cloud layer where warmer thermal emission from Jupiter's deep atmosphere can pass through. The circulation patterns observed here along with the composition measurements from the Galileo Probe suggest that dry air may be converging and sinking over these regions, maintaining their cloud-free appearance. The bright clouds to the right of the hotspot as well as the other bright features may be examples of upwelling of moist air and condensation.

    This frame is a view to the northeast, from between the cloud layers and above the streaks in the lower cloud leading towards the hotspot. The upper haze layer has some features that match the lower cloud, such as the bright streak in the foreground of the frame. These are probably thick clouds that span several tens of vertical kilometers.

    Galileo is the first spacecraft to image Jupiter in near-infrared light (which is invisible to the human eye) using three filters at 727, 756, and 889 nanometers (nm). Because light at these three wavelengths is absorbed at different altitudes by atmospheric methane, a comparison of the resulting images reveals information about the heights of clouds in Jupiter's atmosphere. This information can be visualized by rendering cloud surfaces with the appropriate height variations.

    The visualization reduces Jupiter's true cloud structure to two layers. The height of a high haze layer is assumed to be proportional to the reflectivity of Jupiter at 889 nm. The height of a lower tropospheric cloud is assumed to be proportional to the reflectivity at 727 nm divided by that at 756 nm. This model is overly simplistic, but is based on more sophisticated studies of Jupiter's cloud structure. The upper and lower clouds are separated in the rendering by an arbitrary amount, and the height variations are exaggerated by a factor of 25.

    The lower cloud is colored using the same false color scheme used in previously released image products, assigning red, green, and blue to the 756, 727, and 889 nanometer mosaics, respectively. Light bluish clouds are high and thin, reddish clouds are low, and white clouds are high and thick. The dark blue hotspot in the center is a hole in the lower cloud with an overlying thin haze.

    The images used cover latitudes 1 to 10 degrees and are centered at longitude 336 degrees west. The smallest resolved features are tens of kilometers in size. These images were taken on December 17, 1996, at a range of 1.5 million kilometers (about 930,000 miles) by the Solid State Imaging (CCD) system on NASA's Galileo spacecraft.

    The Jet Propulsion Laboratory, Pasadena, CA manages the Galileo mission for NASA's Office of Space Science, Washington, DC. JPL is an operating division of California Institute of Technology (Caltech).

    This image and other images and data received from Galileo are posted on the World Wide Web, on the Galileo mission home page at URL http://www.jpl.nasa.gov/ galileo.

  12. Zigzagging bubbles rising side by side

    NASA Astrophysics Data System (ADS)

    Sanada, Toshiyuki; Sone, Daiji; Saito, Takayuki

    2007-11-01

    The interaction between zigzagging bubbles (d=2.9mm) rising side by side and its surrounding liquid motion in quiescent water were experimentally investigated. Hypodermic needles and a bubble generator utilizing pressure oscillation were employed to exactly extract and highly reproduce the interaction between the liquid-phase motion and bubble motion at the collision. The recursive cross correlation PIV technique made it possible to obtain the accurate velocity field of the surrounding liquid motion of a pair of bubbles. The experiments were conducted by changing the initial bubble distance. As a result, the two types of velocity fluctuation of bubbles were mainly observed after the collisions. The first case, only the horizontal velocity of each bubbles obviously decreased. The second case, both the horizontal and the vertical velocity decreased. This difference is considered to be due to the different surrounding liquid motion, especially the formation of vorticity.

  13. Formation of the equatorial thermosphere anomaly trough: Local time and solar cycle variations

    NASA Astrophysics Data System (ADS)

    Hsu, Vicki W.; Thayer, Jeffrey P.; Lei, Jiuhou; Wang, Wenbin

    2014-12-01

    This paper evaluates the formation and behavior of the equatorial thermosphere anomaly (ETA) trough in neutral temperature and mass density using the National Center for Atmospheric Research thermosphere-ionosphere electrodynamics general circulation model under quiet geomagnetic activity and March equinox conditions. The driving mechanism for the generation of the ETA trough in the model is field-aligned ion drag. In our simulations, during the daytime, field-aligned ion drag on the north-south flanks of the magnetic equator causes a divergence in meridional winds, leading to an upward change in vertical winds, adiabatic cooling, and a reduction in neutral temperature of about 30 K over the magnetic equator near 400 km. This response closely links ETA behavior to variations in the equatorial ionosphere anomaly (EIA) associated with local time and solar cycle. As the EIA begins to disappear in the evening, the processes in the ETA mechanism recede, causing the ETA trough to subside. The ETA trough is not completely eliminated until about after 23:00 LT. In our simulations, the trough becomes more prominent as the solar cycle progresses from low (F10.7=80) to high (F10.7=180), in agreement with observations. The neutral-ion collision frequency (proportional to variations in electron density) controls ETA day-to-night and solar cycle variations, while plasma scale height and gradients in electron number density and plasma temperature produce a secondary structure in ETA local time behavior that varies with solar cycle levels.

  14. Generation of Bubbly Suspensions in Low Gravity

    NASA Technical Reports Server (NTRS)

    Nahra, Henry K.; Hoffmann, Monica I.; Hussey, Sam; Bell, Kimberly R.

    2000-01-01

    Generation of a uniform monodisperse bubbly suspension in low gravity is a rather difficult task because bubbles do not detach as easily as on Earth. Under microgravity, the buoyancy force is not present to detach the bubbles as they are formed from the nozzles. One way to detach the bubbles is to establish a detaching force that helps their detachment from the orifice. The drag force, established by flowing a liquid in a cross or co-flow configuration with respect to the nozzle direction, provides this additional force and helps detach the bubbles as they are being formed. This paper is concerned with studying the generation of a bubbly suspension in low gravity in support of a flight definition experiment titled "Behavior of Rapidly Sheared Bubbly Suspension." Generation of a bubbly suspension, composed of 2 and 3 mm diameter bubbles with a standard deviation <10% of the bubble diameter, was identified as one of the most important engineering/science issues associated with the flight definition experiment. This paper summarizes the low gravity experiments that were conducted to explore various ways of making the suspension. Two approaches were investigated. The first was to generate the suspension via a chemical reaction between the continuous and dispersed phases using effervescent material, whereas the second considered the direct injection of air into the continuous phase. The results showed that the reaction method did not produce the desired bubble size distribution compared to the direct injection of bubbles. However, direct injection of air into the continuous phase (aqueous salt solution) resulted in uniform bubble-diameter distribution with acceptable bubble-diameter standard deviation.

  15. Molecular dynamics simulation of deuterium trapping and bubble formation in tungsten

    NASA Astrophysics Data System (ADS)

    Yang, Xue; Hassanein, Ahmed

    2013-03-01

    The interaction between plasma particles and tungsten as plasma facing material is one of the critical issues in successfully using tungsten in Tokamak reactors environment. The deuterium bombardment of monocrystalline tungsten was modeled by molecular dynamics simulation using LAMMPS code and Tersoff type interatomic potential. The deuterium trapping rate, implantation depth, and the stopping time in tungsten at several temperatures ranging from 600 to 2000 K bombarded by 5-100 eV deuterium atoms were simulated. Deuterium bubble formation at near tungsten surface was also studied. Irradiated monocrystalline tungsten became amorphous state prior to deuterium cluster formation, and gas bubbles were observed in the 600, 900, and 1200 K tungsten samples. The formation of gas bubbles were caused by the near surface deuterium super-saturation region and the subsequent plastic deformation induced by the local high gas pressure.

  16. Dynamics of the equatorial undercurrent and its determination

    E-print Network

    Wacongne, Sophie

    1988-01-01

    This study focuses on the zonal weakening, eastern termination and seasonal variations of the Atlantic equatorial undercurrent (EUC). The main and most original contribution of the dissertation is a detailed analysis of ...

  17. Suppression of cavitation inception by gas bubble injection: a numerical study focusing on bubble-bubble interaction.

    PubMed

    Ida, Masato; Naoe, Takashi; Futakawa, Masatoshi

    2007-10-01

    The dynamic behavior of cavitation and gas bubbles under negative pressure has been studied numerically to evaluate the effect of gas bubble injection into a liquid on the suppression of cavitation inception. In our previous studies, it was demonstrated by direct observation that cavitation occurs in liquid mercury when mechanical impacts are imposed, and this will cause cavitation damage in spallation neutron sources, in which liquid mercury is bombarded by a high-power proton beam. In the present paper, we describe numerical investigations of the dynamics of cavitation bubbles in liquid mercury using a multibubble model that takes into account the interaction of a cavitation bubble with preexisting gas bubbles through bubble-radiated pressure waves. The numerical results suggest that, if the mercury includes gas bubbles whose equilibrium radius is much larger than that of the cavitation bubble, the explosive expansion of the cavitation bubble (i.e., cavitation inception) is suppressed by the positive-pressure wave radiated by the injected bubbles, which decreases the magnitude of the negative pressure in the mercury. PMID:17995108

  18. Gradient drift eigenmodes in the equatorial electrojet

    NASA Technical Reports Server (NTRS)

    Wang, X.-H.; Bhattacharjee, A.

    1994-01-01

    The problem of kilometer-scale irregularities in the daytime equatorial electrojet is revisited by means of an eigenmode analysis of the gradient drift instability. Realistic physical parameters are used, including the modeled altitude variations of ion and electron collision frequencies and mobilities. The full fourth-order system of two coupled differential equations (each of second order) for the denisty and electrostatic potential perturbations is solved numerically by a relaxation technique. Under some approximations, the fourth-order system can be shown to reduce to a second-order differential equation for the perturbed potential or density. The latter is solved using a shooting technique and provides initial guesses for numerical solutions to the full problem. It is shown that the linear growth rate peaks for kilometer-scale waves, contrary to the findings of recent initial-value studies. This occurs because the equilibrium velocity shear is much more effective as a damping mechanism for short-wavelength modes than it is for the longer, kilometer-scale modes. These results provide a natural qualitative explanation for the observed dominance of kilometer-scale structures in the daytime electrojet spectrum.

  19. POGO observations of the equatorial electrojet

    NASA Technical Reports Server (NTRS)

    Cain, J. C.; Sweeney, R. E.

    1972-01-01

    During intervals in 1967 to 1970, the OGO-4 and 6 spacecraft made over 2000 traversals over the equatorial electrojet in the altitude range 400-800 km when local times were between 9 and 15 hours. These spacecraft carried total field magnetometers making measurements to an accuracy of 2 gamma with a sample rate greater than once a second. Delta F values, the deviations from these observations, were formed from an internal reference model. The results were plotted for a 30 deg band about the equator, and the characteristics of the electrojet effect in the data were investigated. This effect was characterized by a sharp negative V-signature of some 16-19 deg in width and a variable amplitude. The position of this minimum was found to lie within 0.5 deg of the dip equator. A slight northward shift was noted at the longitude of Huancayo. The jet amplitudes were normalized to 400 km amplitudes and observed to be highly variable in time. Amplitudes over the longitude range 50 to 90 deg W averaged 60% higher than elsewhere, as expected, due to the weaker main field. However, though the scatter of amplitudes is high, the expected minima in east Asia was not evident. It was speculated that this could be due to a less conducting upper mantle in this area.

  20. Nanoplankton mixotrophy in the eastern equatorial Pacific

    NASA Astrophysics Data System (ADS)

    Stukel, Michael R.; Landry, Michael R.; Selph, Karen E.

    2011-03-01

    Heterotrophic bacteria, cyanobacteria, and picoeukaryotic algae dominate the plankton community of high nutrient-low chlorophyll (HNLC) areas of the eastern equatorial Pacific (EEP). While grazing on these picoplankton is often attributed to aplastidic zooflagellates, mixotrophic nanoflagellates (phagotrophic phototrophs) may also exert a large grazing pressure. We assessed the relative contributions of mixotrophic nanoplankton and obligate heterotrophs to picoplankton phagotrophy in mixed-layer water of the EEP using 0.8-?m Fluorescently-Labeled Bacteria (FLB). Obligate heterotrophs and phototrophs were distinguished from their ratios of microscopically measured red (chlorophyll a) to green (proflavin-stained protein) fluorescence. Sampling sites were located along a nutrient gradient formed by a tropical instability wave at 0.5°N between 123.5°W and 128°W and at 1.75°N, 125°W. The majority of ingested particles were found within 3-5 ?m flagellates, with 54% of the demonstrated phagotrophs belonging to the high-pigment putatively phototrophic population and obligate heterotrophs responsible for 51% of the demonstrated phagotrophy due to their greater propensity to ingest multiple prey. The importance of mixotrophy as a means of alleviating nutrient stress is indicated by a strong inverse relationship between the proportion of community FLB uptake by mixotrophs and ambient nutrient concentration. Low ambient Fe concentration and a demonstrated community response to Fe-addition in shipboard grow-out experiments suggest that mixotrophs were primarily engaging in phagotrophy to offset Fe-deficiencies.

  1. Gravity waves in the equatorial MLT region

    NASA Astrophysics Data System (ADS)

    Kovalam, S.; Vincent, R. A.; Love, P.

    2006-02-01

    Observations of MF radar winds made at Christmas Island (2N, 157W) between 1990 and 1997 are used to produce daily values of gravity wave variances in the equatorial mesosphere and lower thermosphere (70 100 km). Gravity wave activity is modulated on number of time scales, ranging from diurnal through seasonal to intraseasonal and interannual. A semiannual variation is particularly evident. In this paper we examine the possibility of using the wave variances in the MLT to estimate the momentum flux spectrum near the source height in the troposphere. To test our ideas we focus on modeling observations in April 1993 and April 1994, months which had very different background winds and tides. A linear gravity wave model is used in combination with ray-tracing techniques to investigate the propagation of wave spectra through representative zonal wind and temperature fields, including the effects of tidal winds and temperatures. The magnitude and diurnal variation of observed wave variance are used to constrain the momentum fluxes as a function of height and time. A number of source distributions were tested using this technique. It was found that the observations impose rather strong constraints on the source-level spectrum. A spectrum that has a bias to toward eastward propagating waves gave the best correspondence with observations. Our results have significance for the design and constraint of gravity wave parameterization schemes used in climate models.

  2. Vertical motions in the equatorial middle atmosphere

    NASA Technical Reports Server (NTRS)

    Weisman, M. L.

    1979-01-01

    A single station vertical velocity equation which considers ageostrophic and diabatic effects derived from the first law of thermodynamics and a generalized thermal wind relation is presented. An analysis and verification procedure which accounts for measurement and calculation errors as well as time and space continuity arguments and theoretical predictions are described. Vertical velocities are calculated at every kilometer between 25 and 60 km and for approximately every three hours for the above diurnal period at Kourou (French Guiana), Fort Sherman (Panama Canal Zone), Ascension Island, Antigua (British West Indies) and Natal (Brazil). The results, plotted as time series cross sections, suggest vertical motions ranging in magnitude from 1 or 2 cm/sec at 30 km to as much as 15 cm/sec at 60 km. Many of the general features of the results agree well with atmospheric tidal predictions but many particular features suggest that both smaller time scale gravity waves (periods less than 6 hours) and synoptic type waves (periods greater than 1 day) may be interacting significantly with the tidal fields. The results suggest that vertical motions can be calculated for the equatorial middle atmosphere and must be considered a significant part of the motion for time scales from 8 to 24 hours.

  3. An improved model of equatorial scintillation

    NASA Astrophysics Data System (ADS)

    Secan, J. A.; Bussey, R. M.; Fremouw, E. J.; Basu, Sa.

    1995-05-01

    One of the main limitations of the modeling work that went into the equatorial section of the Wideband ionospheric scintillation model (WBMOD) was that the data set used in the modeling was limited to two stations near the dip equator (Ancon, Peru, and Kwajalein Island, in the North Pacific Ocean) at two fixed local times (nominally 1000 and 2200). Over the past year this section of the WBMOD model has been replaced by a model developed using data from three additional stations (Ascension Island, in the South Atlantic Ocean, Huancayo, Peru, and Manila, Phillipines; data collected under the auspices of the USAF Phillips Laboratory Geophysics Directorate) which provide a greater diversity in both latitude and longitude, as well as cover the entire day. The new model includes variations with latitude, local time, longitude, season, solar epoch, and geomagnetic activity levels. The way in which the irregularity strength parameter CkL is modeled has also been changed. The new model provides the variation of the full probability distribution function (PDF) of log (CkL) rather than simply the average of log (CkL). This permits the user to specify a threshold on scintillation level, and the model will calculate the percent of the time that scintillation will exceed that level in the user-specified scenario. It will also permit calculation of scintillation levels at a user-specified percentile. A final improvement to the WBMOD model is the implementation of a new theory for calculating S4 on a two-way channel.

  4. Lagrangian sources of frontogenesis in the equatorial Atlantic front

    NASA Astrophysics Data System (ADS)

    Giordani, Hervé; Caniaux, Guy

    2014-09-01

    Estimating the processes that control the north equatorial sea surface temperature (SST)-front on the northern edge of the cold tongue in the tropical Atlantic is a key issue for understanding the dynamics of the oceanic equatorial Atlantic and the West African Monsoon. Diagnosis of the frontogenetic forcings on a realistic high-resolution simulation was used to identify the processes involved in the formation and evolution of the equatorial SST-front. The turbulent forcing associated with the mixed-layer turbulent heat flux was found to be systematically frontolytic while the dynamic forcing associated with currents was found to be frontogenetic for the equatorial SST-front. Nevertheless, the low-frequency component of the turbulent forcing was frontogenetic and initiated the SST-front which was then amplified and maintained by the leading dynamic forcing. This forcing was mainly driven by the meridional convergence of the northern South Equatorial Current (nSEC) and the Guinea Current, which points out the essential role played by the circulation in the equatorial SST-front evolution. The quasi-biweekly variability of the equatorial SST-front and its forcings were found to be more strongly coupled to the wind energy flux (WEF) than to the surface wind stress. In fact the WEF controlled the convergence/divergence of the nSEC and Guinea Current and thus the meridional component of the leading dynamic forcing. The WEF explains the equatorial SST-front development better than the wind does because it is a coupled ocean-atmosphere process.

  5. Lagrangian sources of frontogenesis in the equatorial Atlantic front

    NASA Astrophysics Data System (ADS)

    Giordani, Hervé; Caniaux, Guy

    2014-12-01

    Estimating the processes that control the north equatorial sea surface temperature (SST)-front on the northern edge of the cold tongue in the tropical Atlantic is a key issue for understanding the dynamics of the oceanic equatorial Atlantic and the West African Monsoon. Diagnosis of the frontogenetic forcings on a realistic high-resolution simulation was used to identify the processes involved in the formation and evolution of the equatorial SST-front. The turbulent forcing associated with the mixed-layer turbulent heat flux was found to be systematically frontolytic while the dynamic forcing associated with currents was found to be frontogenetic for the equatorial SST-front. Nevertheless, the low-frequency component of the turbulent forcing was frontogenetic and initiated the SST-front which was then amplified and maintained by the leading dynamic forcing. This forcing was mainly driven by the meridional convergence of the northern South Equatorial Current (nSEC) and the Guinea Current, which points out the essential role played by the circulation in the equatorial SST-front evolution. The quasi-biweekly variability of the equatorial SST-front and its forcings were found to be more strongly coupled to the wind energy flux ( WEF) than to the surface wind stress. In fact the WEF controlled the convergence/divergence of the nSEC and Guinea Current and thus the meridional component of the leading dynamic forcing. The WEF explains the equatorial SST-front development better than the wind does because it is a coupled ocean-atmosphere process.

  6. Mesospheric planetary wave signatures in the equatorial electrojet

    Microsoft Academic Search

    T. K. Ramkumar; S. Gurubaran; R. Rajaram

    2009-01-01

    Using five years (1994–1998) of simultaneous and collocated measurements of horizontal winds associated with mesosphere and lower thermosphere (MLT) region and geomagnetic field measurements in the Indian geomagnetic dip equatorial region, an extensive experimental study has been made on the influences of mesospheric planetary waves on the equatorial electrojet (EEJ). The winds are measured using medium-frequency (MF) radar (1.98 MHz)

  7. Polydispersed solids behavior in a bubble column. [Slurry bubble columns

    SciTech Connect

    Smith, D.N.; Ruether, J.A.; Stiegel, G.J.

    1984-01-01

    New data and theory are presented for describing polydispersed solids in slurry bubble columns. Axial solids concentration distributions were measured in a 0.108-m-ID slurry bubble column apparatus operated at steady-state conditions. Slurry and gas superficial velocities ranged from 0.007 to 0.02 m/s and 0.03 to 0.20 m/s, respectively. The liquid phase was water and the solid phase consisted of binary or ternary mixtures of narrow-sized fractions of glass spheres. The experimental data have been used to develop a method for predicting average solids loadings and axial distributions of solids in a bubble column with a one-dimensional sedmentation-dispersion model. Correlations are given for the hindered settling velocity, the solids dispersion coefficient, and the solids concentration at the top and bottom of the column. The effect of a distribution of particle size is interpreted by summation of the concentration of solids for each discrete particle size fraction. 12 refs., 13 figs.

  8. Shockwave and cavitation bubble dynamics of atmospheric air

    NASA Astrophysics Data System (ADS)

    Leela, Ch.; Bagchi, S.; Tewari, Surya P.; Kiran, P. Prem

    2013-11-01

    The generation and evolution of laser induced shock waves (SWs) and the hot core plasma (HCP) created by focusing 7 ns, 532 nm laser pulses in ambient air is studied using time resolved shadowgraphic imaging technique. The dynamics of rapidly expanding plasma releasing SWs into the ambient atmosphere were studied for time delays ranging from nanoseconds to milliseconds with ns temporal resolution. The SW is observed to get detached from expanding HCP at around 3?s. Though the SWs were found to expand spherically following the Sedov-Taylor theory, the rapidly expanding HCP shows asymmetric expansion during both the expansion and cooling phase similar to that of inertial cavitation bubble (CB) dynamics. The asymmetric expansion of HCP leads to oscillation of the plasma boundary, eventually leading to collapse by forming vortices formed by the interaction of ambient air.

  9. Large-scale Electric Field Structures in the Daytime Equatorial Electrojet Oobserved From Alcontara, Brazil

    NASA Astrophysics Data System (ADS)

    Pfaff, R. F.; Freudenreich, H.; Swartz, W.

    2001-05-01

    During the Guar Rocket/Radar Campaign conducted from August-October, 1994, three NASA rockets were launched from Alcontara, Brazil that returned detailed measurements of the DC electric fields, current density, and plasma number density within the unstable daytime equatorial electrojet. The electric field and plasma density data reveal considerable structuring in the middle and lower portion of the electrojet (90-105 km) where the ambient plasma density gradient is unstable. Although the electric field amplitudes are largest (~10-15 mV/m) in the zonal direction, considerable structure (~5-10 mV/m) is also observed in the vertical electric field component as well, implying that the dominant large scale waves involve significant vertical interaction and coupling within the narrow altitude range where they are observed. Furthermore, a detailed examination of the phase of the waveforms show that on some, but not all occasions, locally enhanced eastward fields are associated with locally enhanced upwards (polarization) electric fields, in a manner suggested by Kudeki et al. [JGR, 90, p. 429, 1985] to explain backscatter radar spectral asymmetries. The largest amplitude waveforms imply scales of ~0.5-1.5 km, although the spectrum of irregularities is quite broad, extending to less than 10m. Indeed, evidence for secondary two stream and gradient drift waves is also observed. For each flight, simultaneous VHF CUPRI backscatter vertical echoes also show the presence of both large scale waves and secondary 3 m structures within the same regions. The measurements are discussed in terms of theories involving the non-linear evolution and structuring of plasma waves in the daytime equatorial electrojet.

  10. Influence of Assimilation of Subsurface Temperature Measurements on Simulations of Equatorial Undercurrent and South Equatorial Current Along the Pacific Equator

    NASA Technical Reports Server (NTRS)

    Halpern, David; Leetmaan, Ants; Reynolds, Richard W.; Ji, Ming

    1997-01-01

    Equatorial Pacific current and temperature fields were simulated with and without assimilation of subsurface temperature measurements for April 1992 - March 1995, and compared with moored bouy and research vessel current measurements.

  11. Shock-Wave Propagation and Cavitation Bubble Oscillation by Nd:YAG Laser Ablation of a Metal in Water

    Microsoft Academic Search

    Xiao Chen; Rong-Qing Xu; Jian-Ping Chen; Zhong-Hua Shen; Lu Jian; Xiao-Wu Ni

    2004-01-01

    A highly sensitive fiber-optic sensor based on optical beam deflection is applied for investigating the propagation of a laser-induced plasma shock wave, the oscillation of a cavitation bubble diameter, and the development of a bubble-collapse-induced shock wave when a Nd:YAG laser pulse is focused upon an aluminum surface in water. By the sequence of experimental waveforms detected at different distances,

  12. THE DEPTHS OF HYDROGEN AND HELIUM BUBBLES IN TUNGSTEN: A COMPARISON

    E-print Network

    Krasheninnikov, Arkady V.

    THE DEPTHS OF HYDROGEN AND HELIUM BUBBLES IN TUNGSTEN: A COMPARISON K. O. E. HENRIKSSON,* K of self-trapping and defect trapping of hydrogen and helium implanted into tungsten has been investigated-facing materials contain heavy chemical ele- ments, e.g., tungsten, since energy loss in the plasma is proportional

  13. Etiology of gas bubble disease

    SciTech Connect

    Bouck, G.R.

    1980-11-01

    Gas bubble disease is a noninfectious, physically induced process caused by uncompensated hyperbaric pressure of total dissolved gases. When pressure compensation is inadequate, dissolved gases may form emboli (in blood) and emphysema (in tissues). The resulting abnormal physical presence of gases can block blood vessels (hemostasis) or tear tissues, and may result in death. Population mortality is generally skewed, in that the median time to death occurs well before the average time to death. Judged from mortality curves, three stages occur in gas bubble disease: (1) a period of gas pressure equilibrium, nonlethal cavitation, and increasing morbidity; (2) a period of rapid and heavy mortality; and (3) a period of protracted survival, despite lesions, and dysfunction that eventually terminates in total mortality. Safe limits for gas supersaturation depend on species tolerance and on factors that differ among hatcheries and rivers, between continuous and intermittent exposures, and across ranges of temperature and salinity.

  14. Soap bubbles in paintings: Art and science

    NASA Astrophysics Data System (ADS)

    Behroozi, F.

    2008-12-01

    Soap bubbles became popular in 17th century paintings and prints primarily as a metaphor for the impermanence and fragility of life. The Dancing Couple (1663) by the Dutch painter Jan Steen is a good example which, among many other symbols, shows a young boy blowing soap bubbles. In the 18th century the French painter Jean-Simeon Chardin used soap bubbles not only as metaphor but also to express a sense of play and wonder. In his most famous painting, Soap Bubbles (1733/1734) a translucent and quavering soap bubble takes center stage. Chardin's contemporary Charles Van Loo painted his Soap Bubbles (1764) after seeing Chardin's work. In both paintings the soap bubbles have a hint of color and show two bright reflection spots. We discuss the physics involved and explain how keenly the painters have observed the interaction of light and soap bubbles. We show that the two reflection spots on the soap bubbles are images of the light source, one real and one virtual, formed by the curved surface of the bubble. The faint colors are due to thin film interference effects.

  15. Bubble-Induced Cave Collapse

    PubMed Central

    Girihagama, Lakshika; Nof, Doron; Hancock, Cathrine

    2015-01-01

    Conventional wisdom among cave divers is that submerged caves in aquifers, such as in Florida or the Yucatan, are unstable due to their ever-growing size from limestone dissolution in water. Cave divers occasionally noted partial cave collapses occurring while they were in the cave, attributing this to their unintentional (and frowned upon) physical contact with the cave walls or the aforementioned “natural” instability of the cave. Here, we suggest that these cave collapses do not necessarily result from cave instability or contacts with walls, but rather from divers bubbles rising to the ceiling and reducing the buoyancy acting on isolated ceiling rocks. Using familiar theories for the strength of flat and arched (un-cracked) beams, we first show that the flat ceiling of a submerged limestone cave can have a horizontal expanse of 63 meters. This is much broader than that of most submerged Florida caves (~ 10 m). Similarly, we show that an arched cave roof can have a still larger expanse of 240 meters, again implying that Florida caves are structurally stable. Using familiar bubble dynamics, fluid dynamics of bubble-induced flows, and accustomed diving practices, we show that a group of 1-3 divers submerged below a loosely connected ceiling rock will quickly trigger it to fall causing a “collapse”. We then present a set of qualitative laboratory experiments illustrating such a collapse in a circular laboratory cave (i.e., a cave with a circular cross section), with concave and convex ceilings. In these experiments, a metal ball represented the rock (attached to the cave ceiling with a magnet), and the bubbles were produced using a syringe located at the cave floor. PMID:25849088

  16. HBT Interferometry for Sonoluminescence Bubble

    E-print Network

    Hama, Y; Padula, S S; Padula, Sandra S.

    1996-01-01

    The two-photon correlation of the light pulse emitted from a sonoluminescence bubble is discussed. It is shown that several important information about the mechanism of light emission, such as the time-scale and the shape of the emission region could be obtained from the HBT interferometry. We also argue that such a measurement may serve to reject one of the two currently suggested emission mechanisms, i.e., thermal process versus dynamical Casimir effect.

  17. HBT Interferometry for Sonoluminescence Bubble

    E-print Network

    Y. Hama; T. Kodama; Sandra S. Padula

    1996-12-18

    The two-photon correlation of the light pulse emitted from a sonoluminescence bubble is discussed. It is shown that several important information about the mechanism of light emission, such as the time-scale and the shape of the emission region could be obtained from the HBT interferometry. We also argue that such a measurement may serve to reject one of the two currently suggested emission mechanisms, i.e., thermal process versus dynamical Casimir effect.

  18. Plasma refilling rates for L = 2.3–3.8 flux tubes

    Microsoft Academic Search

    Yuki Obana; Frederick W. Menk; Ichiro Yoshikawa

    2010-01-01

    Measurements of the eigenfrequency of geomagnetic field lines can provide information on the plasma mass density near the equatorial plane of the magnetosphere. Data from an extended meridional array of ground magnetometers therefore allow the radial density distribution, and its temporal variation, to be remotely monitored. Using cross-phase analysis of magnetometer array data, we determined the equatorial mass density during

  19. Unsteady thermocapillary migration of bubbles

    NASA Technical Reports Server (NTRS)

    Dill, Loren H.; Balasubramaniam, R.

    1988-01-01

    Upon the introduction of a gas bubble into a liquid possessing a uniform thermal gradient, an unsteady thermo-capillary flow begins. Ultimately, the bubble attains a constant velocity. This theoretical analysis focuses upon the transient period for a bubble in a microgravity environment and is restricted to situations wherein the flow is sufficiently slow such that inertial terms in the Navier-Stokes equation and convective terms in the energy equation may be safely neglected (i.e., both Reynolds and Marangoni numbers are small). The resulting linear equations were solved analytically in the Laplace domain with the Prandtl number of the liquid as a parameter; inversion was accomplished numerically using a standard IMSL routine. In the asymptotic long-time limit, the theory agrees with the steady-state theory of Young, Goldstein, and Block. The theory predicts that more than 90 percent of the terminal steady velocity is achieved when the smallest dimensionless time, i.e., the one based upon the largest time scale-viscous or thermal-equals unity.

  20. Sonoluminescing bubbles and mass diffusion

    SciTech Connect

    Loefstedt, R.; Weninger, K.; Putterman, S.; Barber, B.P. [Department of Physics, University of California, Los Angeles, California 90024 (United States)] [Department of Physics, University of California, Los Angeles, California 90024 (United States)

    1995-05-01

    The transduction of sound into light by a pulsating bubble in water occurs when its maximum radius is about ten times greater than its ambient radius. For such high-amplitude motion, the steady-state balance of mass flow between the bubble and gas dissolved in the surrounding fluid can be maintained by diffusion only at low partial pressures, about 3 Torr. The observation of sonoluminescence (SL) from bubbles in 200 Torr solutions of air in water requires the action of some as yet unknown mass flow mechanism. On the other hand, gas solutions prepared at low partial pressures, in the diffusion-controlled regime, enable one to achieve SL in gases that do not emit light at higher partial pressures. These include hydrogenic gases and gases with a ratio of specific heats close to unity, which hardly heat up upon adiabatic compression. Experiments that probe the role of mass transfer in SL are presented along with the implications of their comparison to a multiple-time-scale analysis of mass diffusion.

  1. Long-Term Changes in the Equatorial Pacific Trade Winds.

    NASA Astrophysics Data System (ADS)

    Clarke, Allan J.; Lebedev, Anna

    1996-05-01

    Past work has shown that surface zonal equatorial wind stress, zonally integrated from one side of the Pacific to the other, is the key variable for estimating long-term El Niño behavior in the eastern Pacific. The long-term behavior of this key variable is difficult to determine directly because of the paucity of the equatorial wind observations and because of false trends in the wind data introduced by gradual changes in the methods of wind measurement. However, surface pressure data generally does not suffer from these false trends and theory suggests that this key wind variable is linearly related to the difference (p) of surface atmospheric pressure between the eastern and western equatorial Pacific. Detrended COADS pressure in the eastern and western equatorial Pacific and post 1960 detrended equatorial wind stress zonally averaged across the Pacific were used to verify this relationship. Pressure difference and zonally averaged equatorial zonal windstress () were highly correlated (r = 0.90) and the regression also showed that advection of zonal momentum contributes substantially to the momentum balance in the equatorial atmospheric boundary layer. Further, hindcasts of eastern equatorial Pacific sea surface temperature and sea level indicated that from p was more accurate than from winds even since 1960 when wind data were more plentiful. This suggests that the simple pressure difference p is an effective way to monitor both in the past and in the future.Using the p time series as a proxy for zonally integrated wind stress suggests that the equatorial trades strengthened during the early and mid-1930s, weakened from the late 1930s to late 1950s, strengthened during the 1960s, and weakened rapidly since. This pattern is qualitatively consistent with the long record of sea surface temperature measurements at Puerto Chicama (Peru). The more recent rapid weakening is consistent with trends in several physical variables reported previously by others. The long-term changes affect El Niño-La Niña intensity and contribute significantly to sea level rise on the western coast of the Americans. A proxy record of eastern Pacific sea surface temperature from coral suggests that such long-term (decade and longer) weakening and strengthening of the Pacific equatorial trades has occurred before major anthropogenic greenhouse gas release and at least back to 1600 AD.

  2. A Drying Trend in Central Equatorial Africa

    NASA Astrophysics Data System (ADS)

    Diem, J.; Hartter, J.; Ryan, S. J.; Palace, M. W.

    2013-12-01

    There has been considerable uncertainty about changes in rainfall over central equatorial Africa over the past three decades due to a lack of reliable rainfall data in the region. This region contains the northern portion of the Albertine Rift, which is one of the world's hotspots for biodiversity, and within this region there is an exploding human population dependent on rainfed agriculture. Both the human population and conservation/preservation areas are becoming increasingly sensitive to changes in rainfall. There now exists an accurate, high-resolution, satellite based precipitation dataset, African Rainfall Climatology version 2 (ARC2), for the region that provides daily rainfall estimates from 1983 to the present. Here we show significant declines in monthly and annual rainfall in west-central Uganda, which exists in the far northeastern portion of the Rift, from 1983-2012. The decrease in annual rainfall was 110 mm per decade. Therefore, the current annual rainfall of approximately 1,200 mm is less than 80% of the annual rainfall three decades ago. The drying trend most likely extended westward into the Congo Basin. There were significant increasing (decreasing) trends in light-rainfall (heavy-rainfall) days over the period. Using results from previous studies, Indian Ocean warming and increasing carbonaceous aerosols from biomass burning in tropical Africa, are explored as potential causes of the drying trend. The aim of the study is not to find the fingerprint of local and regional anthropogenic forcings on the drying trend, but our results suggest that those forcings could be a leading cause of the drying trend.

  3. Mechanism of bubble detachment from vibrating walls

    SciTech Connect

    Kim, Dongjun; Park, Jun Kwon, E-mail: junkeun@postech.ac.kr; Kang, Kwan Hyoung [Department of Mechanical Engineering, Pohang University of Science and Technology (POSTECH), San 31, Hyoja-dong, Pohang 790-784 (Korea, Republic of)] [Department of Mechanical Engineering, Pohang University of Science and Technology (POSTECH), San 31, Hyoja-dong, Pohang 790-784 (Korea, Republic of); Kang, In Seok [Department of Chemical Engineering, Pohang University of Science and Technology (POSTECH), San 31, Hyoja-dong, Pohang 790-784 (Korea, Republic of)] [Department of Chemical Engineering, Pohang University of Science and Technology (POSTECH), San 31, Hyoja-dong, Pohang 790-784 (Korea, Republic of)

    2013-11-15

    We discovered a previously unobserved mechanism by which air bubbles detach from vibrating walls in glasses containing water. Chaotic oscillation and subsequent water jets appeared when a wall vibrated at greater than a critical level. Wave forms were developed at water-air interface of the bubble by the wall vibration, and water jets were formed when sufficiently grown wave-curvatures were collapsing. Droplets were pinched off from the tip of jets and fell to the surface of the glass. When the solid-air interface at the bubble-wall attachment point was completely covered with water, the bubble detached from the wall. The water jets were mainly generated by subharmonic waves and were generated most vigorously when the wall vibrated at the volume resonant frequency of the bubble. Bubbles of specific size can be removed by adjusting the frequency of the wall's vibration.

  4. Ostwald ripening in multiple-bubble nuclei

    NASA Astrophysics Data System (ADS)

    Watanabe, Hiroshi; Suzuki, Masaru; Inaoka, Hajime; Ito, Nobuyasu

    2014-12-01

    The Ostwald ripening of bubbles is studied by molecular dynamics simulations involving up to 679 × 106 Lennard-Jones particles. Many bubbles appear after depressurizing a system that is initially maintained in the pure-liquid phase, and the coarsening of bubbles follows. The self-similarity of the bubble-size distribution function predicted by Lifshitz-Slyozov-Wagner theory is directly confirmed. The total number of bubbles decreases asymptotically as t-x with scaling exponent x. As the initial temperature increases, the exponent changes from x = 3/2 to 1, which implies that the growth of bubbles changes from interface-limited (the t1/2 law) to diffusion-limited (the t1/3 law) growth.

  5. Formation of Jets and Equatorial Superrotation on Jupiter

    E-print Network

    Tapio Schneider; Junjun Liu

    2008-09-26

    The zonal flow in Jupiter's upper troposphere is organized into alternating retrograde and prograde jets, with a prograde (superrotating) jet at the equator. Existing models posit as the driver of the flow either differential radiative heating of the atmosphere or intrinsic heat fluxes emanating from the deep interior; however, they do not reproduce all large-scale features of Jupiter's jets and thermal structure. Here it is shown that the difficulties in accounting for Jupiter's jets and thermal structure resolve if the effects of differential radiative heating and intrinsic heat fluxes are considered together, and if upper-tropospheric dynamics are linked to a magnetohydrodynamic (MHD) drag that acts deep in the atmosphere. Baroclinic eddies generated by differential radiative heating can account for the off-equatorial jets; meridionally propagating equatorial Rossby waves generated by intrinsic convective heat fluxes can account for the equatorial superrotation. The zonal flow extends deeply into the atmosphere, with its speed changing with depth, up to depths at which the MHD drag acts. The theory is supported by simulations with an energetically consistent general circulation model of Jupiter's outer atmosphere. A simulation that incorporates differential radiative heating and intrinsic heat fluxes reproduces Jupiter's observed jets and thermal structure and makes testable predictions about as-yet unobserved aspects thereof. A control simulation that incorporates only differential radiative heating but not intrinsic heat fluxes produces off-equatorial jets but no equatorial superrotation; another control simulation that incorporates only intrinsic heat fluxes but not differential radiative heating produces equatorial superrotation but no off-equatorial jets.

  6. Bubbles generated from wind-steepened breaking waves: 2. Bubble plumes, bubbles, and wave characteristics

    Microsoft Academic Search

    Ira Leifer; Guillemette Caulliez; Gerrit de Leeuw

    2006-01-01

    Measurements of breaking-wave-generated bubble plumes were made in fresh (but not clean) water in a large wind-wave tunnel. To preserve diversity, a classification scheme was developed on the basis of plume dimensions and “optical density,” or the plume's ability to obscure the background. Optically dense plumes were due to the presence of a peak at large radius in the plume

  7. Buoyancy Driven Shear Flows of Bubble Suspensions

    NASA Astrophysics Data System (ADS)

    Hill, R. J.; Zenit, R.; Chellppannair, T.; Koch, D. L.; Spelt, P. D. M.; Sangani, A.

    1998-11-01

    In this work the gas volume fraction and the root-mean-squared fluid velocity are measured in buoyancy driven shear flows of bubble suspensions in a tall, inclined, rectangular channel. The experiments are performed under conditions where We << 1 and Re >> 1 , so that the bubbles are relatively undeformed and the flow is inviscid and approximately irrotational. Nitrogen is introduced through an array of capillaries at the base of a .2x.02x2 m channel filled with an aqueous electrolyte solution (0.06 molL-1 MgSO_4). The rising bubbles generate a unidirectional shear flow, where the denser suspension at the lower surface of the channel falls, while the less dense suspension at the upper surface rises. Hot-film anemometry is used to measure the resulting gas volume fraction and fluid velocity profiles. The bubble collision rate with the sensor is related to the gas volume fraction and the mean and variance of the bubble velocity using an experimentally measured collision surface area for the sensor. Bubble collisions with the sensor are identified by the characteristic slope of the hot-film anemometer signal when bubbles collide with the sensor. It is observed that the steady shear flow develops a bubble phase pressure gradient across the channel gap as the bubbles interchange momentum through direct collisions. The discrete phase presssure gradient balances the buoyancy force driving bubbles toward the upper surface resulting in a steady void fraction profile across the gap width. The strength of the shear flow is controlled by the extent of bubble segregation and by the effective viscosity of the bubble phase. The measurements are compared with solutions of the averaged equations of motion (Kang et al. 1997; Spelt and Sangani, 1998), for a range of gas volume fractions and channel inclination angles.

  8. Mechanisms for stable single bubble sonoluminescence

    SciTech Connect

    Brenner, M.P. [Department of Mathematics, MIT, Cambridge, Massachusetts 02139 (United States)] [Department of Mathematics, MIT, Cambridge, Massachusetts 02139 (United States); Lohse, D. [Fachbereich Physik der Universitaet Marburg, Renthof 6, 35032 Marburg (Germany)] [Fachbereich Physik der Universitaet Marburg, Renthof 6, 35032 Marburg (Germany); [Department of Mathematics, The University of Chicago, Chicago, Illinois 60637 (United States); Oxtoby, D. [Department of Chemistry and James Franck Institute, The University of Chicago, Chicago, Illinois 60637 (United States)] [Department of Chemistry and James Franck Institute, The University of Chicago, Chicago, Illinois 60637 (United States); Dupont, T.F. [Department of Mathematics, The University of Chicago, Chicago, Illinois 60637 (United States)] [Department of Mathematics, The University of Chicago, Chicago, Illinois 60637 (United States)

    1996-02-01

    A gas bubble trapped in water by an oscillating acoustic field is expected to either shrink or grow on a diffusive time scale, depending on the forcing strength and the bubble size. At high ambient gas concentration this has long been observed. However, recent sonoluminescence experiments show that when the ambient gas concentration is low the bubble can be stable for days. This paper discusses mechanisms leading to stability. {copyright} {ital 1996 The American Physical Society.}

  9. Shock Pulse from a Sonoluminescing Gas Bubble

    NASA Astrophysics Data System (ADS)

    Lee, Yoon-Pyo; Karng, Sarng; Jeon, Jin-Seok; Kwak, Ho-Young

    1997-09-01

    The shock pulse emanating from a sonoluminescing gas bubble was calculated by using the analytical solutions of the conservation equations for the gas inside the bubble and the Kirkwood-Bethe hypothesis for the outgoing wave. The rise time and the magnitude of the pulse signal are in good agreement with the observed values, which may provide the approximate value of the gas pressure at near the collapse of the sonoluminescing gas bubble.

  10. Generator for single bubbles of controllable size

    NASA Astrophysics Data System (ADS)

    Ohl, C. D.

    2001-01-01

    A new type of apparatus for the production of single bubbles of adjustable size is presented. A single bubble is generated by injecting a short burst of gas into a liquid channel flow. The radius of the bubble can be varied continuously from 300 ?m up to a 3 mm by adjusting the timing of a valve injecting the gas. The device works also in liquids with variable pressure and can be microcomputer controlled.

  11. Collapse of vacuum bubbles in a vacuum

    SciTech Connect

    Ng, Kin-Wang; Wang, Shang-Yung [Institute of Physics, Academia Sinica, Taipei, Taiwan 11529 (China); Department of Physics, Tamkang University, Tamsui, Taiwan 25137 (China)

    2011-02-15

    We revisit the dynamics of a false vacuum bubble in a background de Sitter spacetime. We find that there exists a large parameter space that allows the bubble to collapse into a black hole or to form a wormhole. This may have interesting implications for the creation of a baby universe in the laboratory, the string landscape where the bubble nucleation takes place among a plenitude of metastable vacua, and the inflationary physics.

  12. Lattice Boltzmann Study of Bubble Dynamics

    Microsoft Academic Search

    Ismail Oguz Kurtoglu; Ching-Long Lin

    2006-01-01

    The purpose of this work is to assess the applicability of a new two-phase immiscible lattice Boltzmann method based on phase-field method to single bubble dynamics over a wide range of flow regimes. In two-dimensional domain, the bubble geometry, the interface deformation, and the bubble rise characteristics, such as terminal velocity, drag coefficient, and wake properties, are investigated and quantified

  13. DNA Bubble Life Time in Denaturation

    E-print Network

    Zh. S. Gevorkian; Chin-Kun Hu

    2010-10-11

    We have investigated the denaturation bubble life time for a homogeneous as well as for a heterogeneous DNA within a Poland-Scheraga model. It is shown that at criticality the bubble life time for a homogeneous DNA is finite provided that the loop entropic exponent c>2 and has a scaling dependence on DNA length for c<2. Heterogeneity in the thermodynamical limit makes the bubble life time infinite for any entropic exponent.

  14. Cusped Bubbles Rising through Polyelectrolyte Solutions

    NASA Astrophysics Data System (ADS)

    Belmonte, Andrew; Sostarecz, Michael

    2000-11-01

    It is well known that a bubble rising in a polymer fluid can have a cusp-like tail. We report on an experimental study of bubbles rising through solutions of glycerol/water with the addition of the polymer xanthan gum, a polyelectrolyte which becomes more rigid as the free ion concentration is increased. The addition of salt also decreases the elasticity of the xanthan gum solutions, and we observe its effects on the velocity and shape of the cusped bubble.

  15. Size, structure and dynamics of “large” bubbles in a two-dimensional slurry bubble column

    Microsoft Academic Search

    J. W. A. De Swart; R. E. van Vliet; R. Krishna

    1996-01-01

    This paper reports preliminary results of a study on the hydrodynamics of a two-dimensional slurry bubble column. Experiments have been carried out with air\\/paraffin oil slurries with solids concentrations of 0, 28.3 and 38.6 vol% of porous silica particles (mean diameter of 38 ?m). Bubble sizes, bubble coalescence and bubble break-up rates were determined by video image analysis. Increasing slurry

  16. Bubbly wake: the role of the propeller

    NASA Astrophysics Data System (ADS)

    Caille, Francois

    2005-11-01

    We study the length of the bubbly wake of surface vessels. This wake is important for the boat security since it can extend to several ship length and thus increases the detectability of the ship by torpedoes. The image analysis of the wake of real scale ships reveals the sensitivity of the length to propellers. We have thus conducted a systematic study in the laboratory of the interaction bubble/propeller, trying to address several questions:- what is the role of cavitation?- is the propeller able to attract the bubbles present along the ship at the sea surface?- if attracted, can these bubble be broken by the propeller?

  17. Instability and Subsequent Evolution of Electroweak Bubbles

    E-print Network

    Marc Kamionkowski; Katherine Freese

    1992-08-04

    Bubbles in a first-order electroweak phase transition are nucleated with radii $R_0$ and expand with velocity $v$. If $v$ is subsonic, a bubble becomes unstable to non-spherical perturbations when its radius is roughly $10^4\\, R_0$. These perturbations accelerate the transition, and the effective velocity of bubble growth rapidly becomes supersonic. The transition should subsequently proceed spherically via detonation. If for some reason the onset of detonation is postponed, the surface area of the bubbles may be enhanced by $10^5$. We discuss consequences for electroweak baryogenesis.

  18. Laminar bubbly flow in a vertical channel

    NASA Astrophysics Data System (ADS)

    Lu, Jiacai

    2005-11-01

    Direct numerical simulations are used to examine the buoyant rise of many nearly spherical bubbles in laminar flows in vertical channels. The lift force on spherical bubbles leads to a very simple flow structure in terms of the void fraction distribution and the average liquid velocity. The numerical results show that at steady state the number density of bubbles in the center of the channel is always such that the fluid mixture there is in hydrostatic equilibrium and the velocity is uniform. For upflow, excess bubbles are pushed to the walls, forming a bubble rich layer, one bubble diameter thick. For downflow, bubbles are drawn into the channel core, leading to a wall layer with no bubbles, of a thickness determined by the pressure gradient and the average void fraction. For the downflow, the void fraction profile and the velocity profile can be predicted analytically, but for upflow the velocity increase across the wall-layer must be obtained from the simulations. The behaviour of the bubbles in the middle of the channel, including the slip velocity and their velocity fluctuations, is well predicted by results for homogeneous flows in fully periodic domains.

  19. The universe out of a breathing bubble

    E-print Network

    Eduardo I. Guendelman; Nobuyuki Sakai

    2008-04-14

    We consider the model of a false vacuum bubble with a thin wall where the surface energy density is composed of two different components, "domain-wall" type and "dust" type, with opposite signs. We find stably oscillating solutions, which we call "breathing bubbles". By decay to a lower mass state, such a breathing bubble could become either i) a child universe or ii) a bubble that "eats up" the original universe, depending on the sign of the surface energy of the "domain-wall" component. We also discuss the effect of the finite-thickness corrections to the thin-wall approximation and possible origins of the energy contents of our model.

  20. Gas disengagement technique in a slurry bubble column operated in the coalesced bubble regime

    Microsoft Academic Search

    D. J. Lee; X. Luo; L.-S. Fan

    1999-01-01

    The gas disengagement technique is discussed in detail and is applied in a two-dimensional bubble column and slurry bubble column to obtain the bubble size distribution. Flow characteristics including velocities of each phase and dispersed phase size distribution during the gas disengagement process are obtained by using an advanced image analysis tool including a particle image velocimetry technique. It is

  1. Dynamics of Vapour Bubbles in Nucleate Boiling. 1; Basic Equations of Bubble Evolution

    NASA Technical Reports Server (NTRS)

    Buyevich, Yu A.; Webbon, Bruce W.; Callaway, Robert (Technical Monitor)

    1995-01-01

    We consider the behaviour of a vapour bubble formed at a nucleation site on a heated horizontal wall. There is no forced convection of an ambient liquid, and the bubble is presumably separated from the wall by a thin liquid microlayer. The energy conservation law results in a variational equation for the mechanical energy of the whole system consisting of the bubble and liquid. It leads to a set of two strongly nonlinear equations which govern bubble expansion and motion of its centre of mass. A supplementary equation to find out the vapour temperature follows from consideration of heat transfer to the bubble, both from the bulk of surrounding liquid and through the microlayer. The average thickness of the microlayer is shown to increase monotonously with time as the bubble meniscus spreads along the wall. Bubble expansion is driven by the pressure head between vapour inside and liquid far away from the bubble, with due allowance for surface tension and gravity effects. It is resisted by inertia of liquid being placed into motion as the bubble grows. The inertia originates also a force that presses the bubble to the wall. This force is counteracted by the buoyancy and an effective surface tension force that tends to transform the bubble into a sphere. The analysis brings about quite a new formulation of the familiar problem of bubble growth and detachment under conditions of nucleate pool boiling.

  2. Estimating the daytime Equatorial Ionization Anomaly strength from electric field proxies

    NASA Astrophysics Data System (ADS)

    Stolle, C.; Manoj, C.; Lühr, H.; Maus, S.; Alken, P.

    2008-09-01

    The Equatorial Ionization Anomaly (EIA) is a significant feature of the low-latitude ionosphere. During daytime, the eastward electric field drives a vertical plasma fountain at the magnetic equator creating the EIA. Since the eastward electric field is also the driving force for the Equatorial Electrojet (EEJ), the latter is positively correlated with the EIA strength. We investigate the correlation between the zonal electric field and the EIA in the Peruvian sector and compare the results with correlations of the EEJ versus EIA strength. Analyzing 5 years of Challenging Minisatellite Payload (CHAMP) electron density measurements, plasma drift readings from the Jicamarca Unattended Long-term Investigations of the Ionosphere and Atmosphere (JULIA) radar, and magnetic field observations at Huancayo and Piura, we find the EEJ strength and the zonal electric field to be suitable proxies for the EIA intensity. Both analyses reveal high correlation coefficients of cc > 0.8. A typical response time of the EIA to variations in the zonal electric field is ˜1-2 h, and it is ˜2-4 h after EEJ strength variations. Quantitative expressions are provided, which directly relate the EIA parameters to both proxies. From these relations, we infer that an EIA develops also during weak Counter Electrojets (CEJs), but no EIA forms when the vertical plasma drift is zero. For positive EEJ magnetic signatures to form, a minimum eastward electric field of 0.2 mV/m is required on average. The above-mentioned delay between EIA and EEJ variations of ˜3 h is further confirmed by the investigation of the EIA response to transitions from CEJ to EEJ, e.g., during late morning hours.

  3. Equatorial superrotation in a thermally driven zonally symmetric circulation

    NASA Technical Reports Server (NTRS)

    Mayr, H. G.; Harris, I.

    1981-01-01

    Near the equator where the Coriolis force vanishes, the momentum balance for the axially symmetric circulation is established between horizontal and vertical diffusion, which, a priori, does not impose constraints on the direction or magnitude of the zonal winds. Solar radiation absorbed at low latitudes is a major force in driving large scale motions with air rising near the equator and falling at higher latitudes. In the upper leg of the meridional cell, angular momentum is redistributed so that the atmosphere tends to subrotate (or corotate) at low latitudes and superrotate at high latitudes. In the lower leg, however, the process is reversed and produces a tendency for the equatorial region to superrotate. The outcome depends on the energy budget which is closely coupled to the momentum budget through the thermal wind equation; a pressure (temperature) maximum is required to sustain equatorial superrotation. Such a condition arises in regions which are convectively unstable and the temperature lapse rate is superadiabatic. It should arise in the tropospheres of Jupiter and Saturn; planetary energy from the interior is carried to higher altitudes where radiation to space becomes important. Upward equatorial motions in the direct and indirect circulations (Ferrel-Thomson type) imposed by insolation can then trap dynamic energy for equatorial heating which can sustain the superrotation of the equatorial region.

  4. Equatorial Winds on Saturn and the Stratospheric Oscillation

    NASA Technical Reports Server (NTRS)

    Li, Liming; Jian, Xun; Ingersoll, Andrew P.; DelGenio, Anthony D.; Porco, Carolyn C.; West, Robert A.; Vasavada, Ashwin R.; Ewald, Shawn P.; Conrath, Barney J.; Gierasch, Peter J.; Simon-Miller, Amy A.; Nixon, Conor A.; Achterberg, Richard K.; Orton, Glenn S.; Fletcher, Leigh N.; Baines, Kevin H.

    2011-01-01

    The zonal jets on the giant planets are generally thought to be stable with time. Recently, there are still some debates about the general thought. Here, we report a significant temporal variation of the equatorial jet at high-altitude on Saturn. Long-term (2004-2009) observations by Cassini reveal that wind speed at the 60-mbar level increased from 270 m/s in 2004 to 290 m/s in 2008, while the wind speed has been mostly constant over time at the 500-mbar level in the southern equatorial region. The Cassini observations further reveal that the equatorial jet intensified approximately 60 m/s in the stratosphere (1-5 mbar) from 2005 to 2008. The fact that the wind acceleration is weaker at the 60-mbar level (approximately 20 m/s) than at the 1-mbar level (approximately 60 m/s) demonstrates that the equatorial oscillation is damped when it propagates downwards to the tropopause around 60 mbar. The direct measurement of the varying equatorial jet around the tropopause also serves as a key boundary condition when deriving the thermal wind fields in the stratosphere.

  5. The annual cycle in equatorial convection and sea surface temperature

    SciTech Connect

    Mitchell, T.P.; Wallace, J.M. (Washington Univ., Seattle (United States) NASA, Goddard Space Flight Center, Greenbelt, MD (United States))

    1992-10-01

    The coupled atmosphere-ocean system in the equatorial eastern Pacific and Atlantic exhibits a distinct annual cycle that is reflected in contrasting conditions at the times of the two equinoxes. The contrasts are so strong that they dominate the annual march of zonally averaged outgoing long wave radiation for the equatorial belt. The March equinox corresponds to the warm season when the equatorial cold tongues in the eastern Pacific and Atlantic area absent. With the onset of summer monsoon convection over Colombia, Central America, and West Africa in May-June, northward surface winds strengthen over the eastern Pacific and Atlantic, the equatorial cold tongues reappear, and the marine convection shifts from the equatorial belt to the intertropical convergence zones (ITCZs) along 8 deg N. On the basis of observational evidence concerning the timing and year-to-year regularity of the surface wind changes during the development of the cold tongues, it is argued that (1) the increase in the northward surface winds in response to the onset of the northern summer monsoon may be instrumental in reestablishing the cold tongues, and (2) positive feedbacks involving both the zonal and meridional wind components contribute to the remarkable robustness of the cold tongue-ITCZs complexes in both oceans. 36 refs.

  6. The annual cycle in equatorial convection and sea surface temperature

    NASA Technical Reports Server (NTRS)

    Mitchell, Todd P.; Wallace, John M.

    1992-01-01

    The coupled atmosphere-ocean system in the equatorial eastern Pacific and Atlantic exhibits a distinct annual cycle that is reflected in contrasting conditions at the times of the two equinoxes. The contrasts are so strong that they dominate the annual march of zonally averaged outgoing long wave radiation for the equatorial belt. The March equinox corresponds to the warm season when the equatorial cold tongues in the eastern Pacific and Atlantic area absent. With the onset of summer monsoon convection over Colombia, Central America, and West Africa in May-June, northward surface winds strengthen over the eastern Pacific and Atlantic, the equatorial cold tongues reappear, and the marine convection shifts from the equatorial belt to the intertropical convergence zones (ITCZs) along 8 deg N. On the basis of observational evidence concerning the timing and year-to-year regularity of the surface wind changes during the development of the cold tongues, it is argued that (1) the increase in the northward surface winds in response to the onset of the northern summer monsoon may be instrumental in reestablishing the cold tongues, and (2) positive feedbacks involving both the zonal and meridional wind components contribute to the remarkable robustness of the cold tongue-ITCZs complexes in both oceans.

  7. Equatorial Density Irregularity Structures at Intermediate Scales and Their Temporal Evolution

    NASA Technical Reports Server (NTRS)

    Kil, Hyosub; Heelis, R. A.

    1998-01-01

    We examine high resolution measurements of ion density in the equatorial ionosphere from the AE-E satellite during the years 1977-1981. Structure over spatial scales from 18 km to 200 m is characterized by the spectrum of irregularities at larger and smaller scales and at altitudes above 350 km and below 300 km. In the low-altitude region, only small amplitude large-scale (lambda greater than 5 km) density modulations are often observed, and thus the power spectrum of these density structures exhibits a steep spectral slope at kilometer scales. In the high-altitude region, sinusoidal density fluctuations, characterized by enhanced power near 1-km scale, are frequently observed during 2000-0200 LT. However, such fluctuations are confined to regions at the edges of larger bubble structures where the average background density is high. Small amplitude irregularity structures, observed at early local time hours, grow rapidly to high-intensity structures in about 90 min. Fully developed structures, which are observed at late local time hours, decay very slowly producing only-small differences in spectral characteristics even 4 hours later. The local time evolution of irregularity structure is investigated by using average statistics for low-(1% less than sigma less than 5%) and high-intensity (sigma greater than 10%) structures. At lower altitudes, little chance in the spectral slope is seen as a function of local time, while at higher attitudes the growth and maintenance of structures near 1 km scales dramatically affects the spectral slope.

  8. 21 CFR 870.4205 - Cardiopulmonary bypass bubble detector.

    Code of Federal Regulations, 2010 CFR

    2010-04-01

    ...false Cardiopulmonary bypass bubble detector. 870.4205 Section 870.4205...4205 Cardiopulmonary bypass bubble detector. (a) Identification. A cardiopulmonary bypass bubble detector is a device used to detect...

  9. Fluid mechanics of bubble capture by the diving bell spider

    E-print Network

    Brooks, Alice (Alice P.)

    2010-01-01

    The water spider, a unique member of its species, is used as inspiration for a bubble capture mechanism. Bubble mechanics are studied in the pursuit of a biomimetic solution for transporting air bubbles underwater. Careful ...

  10. Colorful Demos with a Long-Lasting Soap Bubble.

    ERIC Educational Resources Information Center

    Behroozi, F.; Olson, D. W.

    1994-01-01

    Describes several demonstrations that feature interaction of light with soap bubbles. Includes directions about how to produce a long-lasting stationary soap bubble with an easily changeable size and describes the interaction of white light with the bubble. (DDR)

  11. Dark-current-free laser-plasma acceleration in blowout regime using nonlinear plasma lens

    NASA Astrophysics Data System (ADS)

    Kalmykov, S. Y.

    2013-01-01

    It is demonstrated that a thin dense plasmas lab (lens), placed before a multi-centimeter-length, low-density plasma (accelerator), overfocuses an incident petawatt laser pulse at a controlled location inside the accelerator, creating an expanding electron density bubble that traps plasma electrons over a brief time interval. As soon as the pulse stabilizes and self-guiding begins, the bubble stabilizes and transforms into the ?rst (non-broken) bucket of a conventional three-dimensional nonlinear plasma wave, eliminating any chance for further injection. A well collimated, quasi-monoenergetic electron bunch with a zero low-energy background further accelerates to a multi-GeV energy.

  12. Tether radiation in Juno-type and circular-equatorial Jovian orbits

    NASA Astrophysics Data System (ADS)

    Sanchez-Torres, A.; Sanmartin, J. R.

    2011-12-01

    Wave radiation by a conductor carrying a steady current in both a polar, highly eccentric, low perijove orbit, as in NASA's planned Juno mission, and an equatorial low Jovian orbit (LJO) mission below the intense radiation belts, is considered. Both missions will need electric power generation for scientific instruments and communication systems. Tethers generate power more efficiently than solar panels or radioisotope power systems (RPS). The radiation impedance is required to determine the current in the overall tether circuit. In a cold plasma model, radiation occurs mainly in the Alfvén and fast magnetosonic modes, exhibiting a large refraction index. The radiation impedance of insulated tethers is determined for both modes and either mission. Unlike the Earth ionospheric case, the low-density, highly magnetized Jovian plasma makes the electron gyrofrequency much larger than the plasma frequency; this substantially modifies the power spectrum for either mode by increasing the Alfvén velocity. Finally, an estimation of the radiation impedance of bare tethers is considered. In LJO, a spacecraft orbiting in a slow downward spiral under the radiation belts would allow determining magnetic field structure and atmospheric composition for understanding the formation, evolution, and structure of Jupiter. Additionally, if the cathodic contactor is switched off, a tether floats electrically, allowing e-beam emission that generate auroras. On/off switching produces bias/current pulses and signal emission, which might be used for Jovian plasma diagnostics.

  13. Effects of Heavy Ions on ULF Wave Resonances Near the Equatorial Region

    SciTech Connect

    D.-H.Lee, J.R. Johnson, K. Kim and K.-S.Kim

    2008-11-20

    Pc1-2 ULF waves are strongly associated with the presence of various ions in the magnetosphere. We investigate the role of heavy ion resonances in nonuniform plasmas near the equatorial region. By adopting the invariant imbedding method, the coupled plasma wave equations are solved in an exact manner to calculate the resonant absorption at the ion-ion hybrid resonance. Our results show that irreversible mode conversion occurs at the resonance, which absorbs the fast wave energy. It is found that waves near the resonances appear with linear polarization, and their amplitude and frequency are sensitive to the properties of the heavy ion plasma composition. We examine how these resonances occur for various H+ - He+ populations in detail by performing an accurate calculation of the mode conversion effciency. Because the multi-ion hybrid resonance locations in cold plasmas are determined by simple parameters such as the fraction of the ion number density of each species and the magnetic field, we suggest that it is possible to monitor heavy ion composition by examining the peak frequencies of linearly polarized wave events in either electric field or magnetic field spectral data.

  14. Is the Local Bubble dead?

    E-print Network

    Dieter Breitschwerdt; Donald P. Cox

    2004-01-21

    We give a summary of the current state of Local Bubble research, resulting from the discussions of a dedicated panel meeting. After more than 25 years of intense observational and theoretical work, we are still far from a coherent picture, although a probable one emerges at the horizon. A multi-supernova origin seems to be the best guess, with non-equilibrium cooling and soft X-ray emission accompanying its expansion. In addition our vantage point may force us to accept a substantial but quantitatively unknown contribution from heliospheric emission.

  15. Biosynthesis within a bubble architecture

    NASA Astrophysics Data System (ADS)

    Choi, Hyo-Jick; Montemagno, Carlo D.

    2006-05-01

    Sub-cellular compartmentalization is critical to life; it minimizes diffusion effects and enables locally high concentrations of biochemicals for improved reaction kinetics. We demonstrate an example of in vitro biochemical synthesis inside the water channels of foam using engineered artificial organelles (bacteriorhodopsin and F0F1-ATP synthase reconstituted polymer vesicles) as functional units to produce ATP. These results show that the interstitial space of bubbles serves as a metaphor for sub-cellular structure, providing a new platform for both investigating cellular metabolism and the engineering of biofunctional materials and systems.

  16. Problem Solving: Bubble Gum Contest

    NSDL National Science Digital Library

    WGHB Boston

    2013-01-01

    This professional development video clip presents students engaged in The Common Core Practice Standard #1—Make sense of problems and persevere in solving them. The learners gather data for a bubble gum contest, as part of a larger activity involving recording data and writing up results. Students understand the problem and persevere with the task as they independently go to other classrooms to conduct their survey. Additional resources include a video transcript, teaching tips, and a link to a professional development reflection activity based upon the video.

  17. Equatorial Imaging with e-MERLIN Including the Chilbolton Antenna

    E-print Network

    Ian Heywood; Hans-Rainer Kloeckner; Steve Rawlings

    2008-01-14

    We discuss the equatorial imaging benefits that arise from the addition of the 25-metre dish at Chilbolton to the e-MERLIN array. Its inclusion considerably enhances the capabilities of e-MERLIN on and below the equator. This will become particularly important in the era of ALMA and other upcoming southern hemisphere facilities. We present simulated observations of point sources in the equatorial region of the sky which is the target area for many existing sky surveys. We find that the additional baselines created by the inclusion of the Chilbolton dish favourably adjust the beam shape of e-MERLIN to a more compact and circular shape, with significantly reduced sidelobe structure. Putting aside the benefits of increased collecting area, the modified beam shape has implications for more rapidly reaching a given completeness limit for equatorial surveys.

  18. Dynamo region and the equatorial electrojet in the Jovian atmosphere

    NASA Astrophysics Data System (ADS)

    Raghavarao, R.; Dagar, R.

    1983-06-01

    The existence of the dynamo region is identified in the atmosphere of Jupiter. It is found that the dynamo region extends from an altitude of 130 km (0.153 mbar) to 330 km (0.027 microbar) reckoned from zero altitude corresponding to 43.8 mbar pressure level. Physical features of the equatorial electrojet in the ionosphere of Jupiter are modelled in detail. The Jovian equatorial electrojet has a maximum eastward current density of about 1.5 A/sq km at an altitude of 270 km (0.33 microbar) with a latitudinal half width of about + or - 11 degrees. The thickness of the equatorial half width is 100 km in altitude range. The type I instability in the electrojet can exist only if the electron streaming velocity exceeds the value of about 250 m/s.

  19. Numerical investigation of electron self-injection in the nonlinear bubble regime

    NASA Astrophysics Data System (ADS)

    Benedetti, C.; Schroeder, C. B.; Esarey, E.; Rossi, F.; Leemans, W. P.

    2013-10-01

    The process of electron self-injection in the nonlinear bubble wake generated by a short and intense laser pulse propagating in a uniform underdense plasma is studied by means of fully self-consistent particle-in-cell simulations and test-particle simulations. We consider a wake generated by a non-evolving laser driver traveling with a prescribed velocity, which then sets the structure and the velocity of the wake, so the injection dynamics is decoupled from driver evolution, but a realistic structure for the wakefield is retained. We show that a threshold for self-injection into a non-evolving bubble wake exists, and we characterize the dependence of the self-injection threshold on laser intensity, wake velocity, and plasma temperature for a range of parameters of interest for current and future laser-plasma accelerators.

  20. Multi-point observations of the inner boundary of the plasma sheet during geomagnetic disturbances

    E-print Network

    California at Berkeley, University of

    of the equatorial dusk-side plasma in the string-of-pearls configuration, allowing the dynamics of particle- sphere in a string-of-pearls configuration, successively crossing geostationary orbit, allowing

  1. Dynamics of Vapour Bubbles in Nucleate Boiling. 2; Evolution of Thermally Controlled Bubbles

    NASA Technical Reports Server (NTRS)

    Buyevich, Yu A.; Webbon, Bruce W.; Callaway, Robert (Technical Monitor)

    1995-01-01

    The previously developed dynamic theory of growth and detachment of vapour bubbles under conditions of nucleate pool boiling is applied to study motion and deformation of a bubble evolving at a single nucleation site. The bubble growth is presumed to be thermally controlled, and two components of heat transfer to the bubble are accounted of: the one from the bulk of surrounding liquid and the one due to heat conduction across a liquid microlayer formed underneath the bubble. Bubble evolution is governed by the buoyancy and an effective surface tension force, both the forces making the bubble centre of mass move away from the wall and, thus, assisting its detachment. Buoyancy-controlled and surface-tension-controlled regimes are considered separately in a meticulous way. The duration of the whole process of bubble evolution till detachment, the rate of growth, and the bubble departure size are found as functions of time and physical and operating parameters. Some repeatedly observed phenomena, such as an influence of gravity on the growth rate, are explained. Inferences of the model agree qualitatively with available experimental evidence, and conclusions pertaining to the dependence on gravity of the bubble radius at detachment and the whole time of the bubble development when being attached to the wall are confirmed quantitatively.

  2. The Fermi Bubbles and Galactic Centre Star Formation

    NASA Astrophysics Data System (ADS)

    Crocker, Roland

    We construct a simple model of the star-formation- (and resultant supernova) driven mass and energy flows through the inner˜200pc (in diameter) of the Galaxy. Our modelling is constrained, in particular, by the non-thermal radio continuum and ?-ray signals detected from the region. The region's star-formation activity drives an outflow of plasma, cosmic rays, and entrained, cooler gas. The plasma outflow from the Galactic Centre (GC) reaches a height of a few kpc and is compellingly related to the recently-discovered Fermi Bubbles by a number of pieces of evidence. In general, our investigations explicitly reveal the GC's important role in the Milky Ways wider stellar ecology.

  3. Dynamics of exploding plasmas in a large magnetized plasma

    SciTech Connect

    Niemann, C.; Gekelman, W.; Constantin, C. G.; Everson, E. T.; Schaeffer, D. B.; Clark, S. E.; Zylstra, A. B.; Pribyl, P.; Tripathi, S. K. P.; Bondarenko, A. S. [Department of Physics and Astronomy, University of California Los Angeles, Los Angeles, California 90095 (United States); Winske, D. [Los Alamos National Laboratory, Los Alamos, New Mexico 87545 (United States); Larson, D.; Glenzer, S. H. [Lawrence Livermore National Laboratory, Livermore, California 94550 (United States)

    2013-01-15

    The dynamics of an exploding laser-produced plasma in a large ambient magneto-plasma was investigated with magnetic flux probes and Langmuir probes. Debris-ions expanding at super-Alfvenic velocity (up to M{sub A}=1.5) expel the ambient magnetic field, creating a large (>20 cm) diamagnetic cavity. We observe a field compression of up to B/B{sub 0}=1.5 as well as localized electron heating at the edge of the bubble. Two-dimensional hybrid simulations reproduce these measurements well and show that the majority of the ambient ions are energized by the magnetic piston and swept outside the bubble volume. Nonlinear shear-Alfven waves ({delta}B/B{sub 0}>25%) are radiated from the cavity with a coupling efficiency of 70% from magnetic energy in the bubble to the wave.

  4. Dynamics of exploding plasmas in a large magnetized plasma

    NASA Astrophysics Data System (ADS)

    Niemann, C.; Gekelman, W.; Constantin, C. G.; Everson, E. T.; Schaeffer, D. B.; Clark, S. E.; Winske, D.; Zylstra, A. B.; Pribyl, P.; Tripathi, S. K. P.; Larson, D.; Glenzer, S. H.; Bondarenko, A. S.

    2013-01-01

    The dynamics of an exploding laser-produced plasma in a large ambient magneto-plasma was investigated with magnetic flux probes and Langmuir probes. Debris-ions expanding at super-Alfvénic velocity (up to MA=1.5) expel the ambient magnetic field, creating a large (>20 cm) diamagnetic cavity. We observe a field compression of up to B /B0=1.5 as well as localized electron heating at the edge of the bubble. Two-dimensional hybrid simulations reproduce these measurements well and show that the majority of the ambient ions are energized by the magnetic piston and swept outside the bubble volume. Nonlinear shear-Alfvén waves (?B/B0>25%) are radiated from the cavity with a coupling efficiency of 70% from magnetic energy in the bubble to the wave.

  5. Metal quotas of plankton in the equatorial Pacific Ocean

    NASA Astrophysics Data System (ADS)

    Twining, Benjamin S.; Baines, Stephen B.; Bozard, James B.; Vogt, Stefan; Walker, Elyse A.; Nelson, David M.

    2011-03-01

    The micronutrient metals Mn, Fe, Co, Ni and Zn are required for phytoplankton growth, and their availability influences ocean productivity and biogeochemistry. Here we report the first direct measurements of these metals in phytoplankton and protozoa from the equatorial Pacific Ocean. Cells representing 4 functional groups (diatoms, autotrophic flagellates, heterotrophic flagellates and autotrophic picoplankton) were collected from the surface mixed layer using trace-metal clean techniques during transects across the equator at 110°W and along the equator between 110°W and 140°W. Metal quotas were determined for individual cells with synchrotron x-ray fluorescence microscopy, and cellular stoichiometries were calculated relative to measured P and S, as well as to C calculated from biovolume. Bulk particulate (>3 ?m) metal concentrations were also determined at 3 stations using inductively coupled plasma mass spectrometry for comparison to single-cell stoichiometries. Phosphorus-normalized Mn, Fe, Ni and Zn ratios were significantly higher in diatoms than other cell types, while Co stoichiometries were highest in autotrophic flagellates. The magnitude of these effects ranged from approximately 2-fold for Mn in diatoms and autotrophic flagellates to nearly an order of magnitude for Fe in diatoms and picoplankton. Variations in S-normalized metal stoichiometries were also significant but of lower magnitude (1.4 to 6-fold). Cobalt and Mn quotas were 1.6 and 3-fold higher in autotrophic than heterotrophic flagellates. Autotrophic picoplankton were relatively enriched in Ni but depleted in Zn, matching expectations based on known uses of these metals in prokaryotes and eukaryotes. Significant spatial variability in metal stoichiometries was also observed. At two stations deviations in Fe stoichiometries reflected features in the dissolved Fe distribution. At these same stations, high Ni stoichiometries in autotrophic flagellates were correlated with elevated ammonium and depressed nitrate concentrations. The spatial effects may have resulted from the passage of tropical instability waves along the equator. Comparison of bulk and single-cell results show similar Mn:P ratios at 2 of 3 stations, but Fe:P and Ni:P were systematically higher in bulk material and Co:P was lower. These results suggest an overrepresentation of diatoms or diatom-based detritus in the bulk fraction. Taken together, the analyses present a generalized stoichiometry of Fe?Zn>Mn?Ni>Co in the plankton. Diatom Fe quotas exceeded minimum subsistence levels, characteristic of cells growing actively on oxidized N sources. This study demonstrates the subst antial biogeochemical insight that can be gained from studies of metal quotas in individual functional groups.

  6. Mechanism of single-bubble sonoluminescence

    Microsoft Academic Search

    Kyuichi Yasui

    1999-01-01

    The mechanism of the light emission of single-bubble sonoluminescence (SBSL) is studied theoretically based on the quasiadiabatic compression model. It is concluded that SBSL is not the blackbody radiation but the thermal radiation. It is clarified that the shape of the spectrum is determined by the temperature inside the bubble and the intensity is determined by the rates of the

  7. Drops and Bubble in Materials Science

    NASA Astrophysics Data System (ADS)

    Doremus, R. H.

    1982-03-01

    The formation of extended p-n junctions in semiconductors by drop migration, mechanisms and morphologies of migrating drops and bubbles in solids and nucleation and corrections to the Volmer-Weber equations are discussed. Bubble shrinkage in the processing of glass, the formation of glass microshells as laser-fusion targets, and radiation-induced voids in nuclear reactors were examined.

  8. Drops and Bubble in Materials Science

    NASA Technical Reports Server (NTRS)

    Doremus, R. H.

    1982-01-01

    The formation of extended p-n junctions in semiconductors by drop migration, mechanisms and morphologies of migrating drops and bubbles in solids and nucleation and corrections to the Volmer-Weber equations are discussed. Bubble shrinkage in the processing of glass, the formation of glass microshells as laser-fusion targets, and radiation-induced voids in nuclear reactors were examined.

  9. Continuous-data FIFO bubble shift register

    NASA Technical Reports Server (NTRS)

    Chen, T. T.

    1977-01-01

    Simple loop first-in-first-out (FIFO) bubble memory shift register has continuous storage capability. Bubble shift register simplifies chip-control electronics by enabling all control functions to be alined at same bit. FIFO shift register is constructed from passive replicator and annihilator combinations.

  10. The Minnaert Bubble: An Acoustic Approach

    ERIC Educational Resources Information Center

    Devaud, Martin; Hocquet, Thierry; Bacri, Jean-Claude; Leroy, Valentin

    2008-01-01

    We propose an "ab initio" introduction to the well-known Minnaert pulsating bubble at graduate level. After a brief recall of the standard stuff, we begin with a detailed discussion of the radial movements of an air bubble in water. This discussion is managed from an acoustic point of view, and using the Lagrangian rather than the Eulerian…

  11. The Physics of Foams, Droplets and Bubbles

    ERIC Educational Resources Information Center

    Sarker, Dipak K.

    2013-01-01

    Foams or bubble dispersions are common to milkshakes, bread, champagne froth, shaving mousse, shampoo, crude oil extraction systems, upholstery packing and bubble wrap, whereas the term droplet is often synonymous with either a small drop of water or a drop of oil--a type of coarse dispersion. The latter are seen in butter and milk, household…

  12. Measuring the surface tension of soap bubbles

    NASA Technical Reports Server (NTRS)

    Sorensen, Carl D.

    1992-01-01

    The objectives are for students to gain an understanding of surface tension, to see that pressure inside a small bubble is larger than that inside a large bubble. These concepts can be used to explain the behavior of liquid foams as well as precipitate coarsening and grain growth. Equipment, supplies, and procedures are explained.

  13. Simple sorting algorithms and their Bubble sort

    E-print Network

    Alechina, Natasha

    ;Complexity of bubble sort · For an array of size n, in the worst case: 1st passage through the inner loop: n-1 comparisons and n-1 swaps · ... · (n-1)st passage through the inner loop: one comparison and one;Bubble sort of a linked list Node border = null; // first node in the sorted part while (border != head

  14. Simple sorting algorithms and their Bubble sort

    E-print Network

    Alechina, Natasha

    Complexity of bubble sort · For an array of size n, in the worst case: 1st passage through the inner loop: n-1 comparisons and n-1 swaps · ... · (n-1)st passage through the inner loop: one comparison and one;2 Bubble sort of a linked list Node border = null; // first node in the sorted part while (border != head

  15. Longitudinal Variation and Waves in Jupiter's South Equatorial Wind Jet

    NASA Technical Reports Server (NTRS)

    Simon-Miller, A. A.; Rogers, John H.; Gierasch, Peter J.; Choi, David; Allison, Michael; Adamoli, Gianluigi; Mettig, Hans-Joerg

    2012-01-01

    We have conducted a detailed study of the cloud features in the strong southern equatorial wind jet near 7.5 S planetographic latitude. To understand the apparent variations in average zonal wind jet velocity at this latitude [e.g.. 1,2,3], we have searched for variations iIi both feature latitude and velocity with longitude and time. In particular, we focused on the repetitive chevron-shaped dark spots visible on most dates and the more transient large anticyclonic system known as the South Equatorial Disturbance (SED). These small dark spots are interpreted as cloud holes, and are often used as material tracers of the wind field.

  16. Observations of ELF electromagnetic waves associated with equatorial spread F

    NASA Technical Reports Server (NTRS)

    Kelley, M. C.; Holtet, J. A.; Tsurutani, B. T.

    1979-01-01

    Extreme low frequency electromagnetic waves have been observed below the F peak in the equatorial ionosphere by instruments onboard OGO-6. Electrostatic wave observations indicate that the steep gradient was unstable to the process which causes equatorial spread F above the region where the electromagnetic waves were observed. The data are very similar to observations near the polar cusp and give further evidence that ELF waves are excluded from regions of rapid and irregular density increases. Low level electromagnetic waves with similar properties were occasionally observed on the nightside by the OVI-17 electric field sensor and may be plasmaspheric hiss which has propagated to low altitude.

  17. Giant bubble pinch-off

    E-print Network

    Raymond Bergmann; Devaraj van der Meer; Mark Stijnman; Marijn Sandtke; Andrea Prosperetti; Detlef Lohse

    2006-01-24

    Self-similarity has been the paradigmatic picture for the pinch-off of a drop. Here we will show through high-speed imaging and boundary integral simulations that the inverse problem, the pinch-off of an air bubble in water, is not self-similar in a strict sense: A disk is quickly pulled through a water surface, leading to a giant, cylindrical void which after collapse creates an upward and a downward jet. Only in the limiting case of large Froude number the neck radius $h$ scales as $h(-\\log h)^{1/4} \\propto \\tau^{1/2}$, the purely inertial scaling. For any finite Froude number the collapse is slower, and a second length-scale, the curvature of the void, comes into play. Both length-scales are found to exhibit power-law scaling in time, but with different exponents depending on the Froude number, signaling the non-universality of the bubble pinch-off.

  18. Gas bubble dynamics in soft materials

    E-print Network

    J. M. Solano-Altamirano; John D. Malcolm; Saul Goldman

    2014-10-14

    Epstein and Plesset's seminal work on the rate of gas bubble dissolution and growth in a simple liquid is generalized to render it applicable to a gas bubble embedded in a soft elastic medium. Both the underlying diffusion equation and the expression for the gas bubble pressure were modified to allow for the non-zero shear modulus of the elastic medium. The extension of the diffusion equation results in a trivial shift (by an additive constant) in the value of the diffusion coefficient, and does not change the form of the rate equations. But the use of a Generalized Young-Laplace equation for the bubble pressure resulted in significant differences on the dynamics of bubble dissolution and growth, relative to a simple liquid medium. Depending on whether the salient parameters (solute concentration, initial bubble radius, surface tension, and shear modulus) lead to bubble growth or dissolution, the effect of allowing for a non-zero shear modulus in the Generalized Young-Laplace equation is to speed up the rate of bubble growth, or to reduce the rate of bubble dissolution, respectively. The relation to previous work on visco-elastic materials is discussed, as is the connection of this work to the problem of Decompression Sickness (specifically, "the bends"). Examples of tissues to which our expressions can be applied are provided. Also, a new phenomenon is predicted whereby, for some parameter values, a bubble can be metastable and persist for long times, or it may grow, when embedded in a homogeneous under-saturated soft elastic medium.

  19. Gas bubble dynamics in soft materials.

    PubMed

    Solano-Altamirano, J M; Malcolm, John D; Goldman, Saul

    2015-01-01

    Epstein and Plesset's seminal work on the rate of gas bubble dissolution and growth in a simple liquid is generalized to render it applicable to a gas bubble embedded in a soft elastic solid. Both the underlying diffusion equation and the expression for the gas bubble pressure were modified to allow for the non-zero shear modulus of the medium. The extension of the diffusion equation results in a trivial shift (by an additive constant) in the value of the diffusion coefficient, and does not change the form of the rate equations. But the use of a generalized Young-Laplace equation for the bubble pressure resulted in significant differences on the dynamics of bubble dissolution and growth, relative to an inviscid liquid medium. Depending on whether the salient parameters (solute concentration, initial bubble radius, surface tension, and shear modulus) lead to bubble growth or dissolution, the effect of allowing for a non-zero shear modulus in the generalized Young-Laplace equation is to speed up the rate of bubble growth, or to reduce the rate of bubble dissolution, respectively. The relation to previous work on visco-elastic materials is discussed, as is the connection of this work to the problem of Decompression Sickness (specifically, "the bends"). Examples of tissues to which our expressions can be applied are provided. Also, a new phenomenon is predicted whereby, for some parameter values, a bubble can be metastable and persist for long times, or it may grow, when embedded in a homogeneous under-saturated soft elastic medium. PMID:25382720

  20. Primary Particles from different bubble generation techniques

    NASA Astrophysics Data System (ADS)

    Butcher, A. C.; King, S. M.; Rosenoern, T.; Nilsson, E. D.; Bilde, M.

    2011-12-01

    Sea spray aerosols (SSA) are of major interest to global climate models due to large uncertainty in their emissions and ability to form Cloud Condensation Nuclei (CCN). In general, SSA are produced from wind breaking waves that entrain air and cause bubble bursting on the ocean surface. Preliminary results are presented for bubble generation, bubble size distribution, and CCN activity for laboratory generated SSA. In this study, the major processes of bubble formation are examined with respect to particle emissions. It has been suggested that a plunging jet closely resembles breaking wave bubble entrainment processes and subsequent bubble size distributions (Fuentes, Coe et al. 2010). Figure 1 shows the different particle size distributions obtained from the various bubble generation techniques. In general, frits produce a higher concentration of particles with a stronger bimodal particle size distribution than the various jet configurations used. The experiments consist of a stainless steel cylinder closed at both ends with fittings for aerosol sampling, flow connections for the recirculating jet, and air supply. Bubble generation included a recirculating jet with 16 mm or 4 mm nozzles, a stainless steel frit, or a ceramic frit. The chemical composition of the particles produced via bubble bursting processes has been probed using particle CCN activity. The CCN activity of sodium chloride, artificial sea salt purchased from Tropic Marin, and laboratory grade artificial sea salt (Kester, Duedall et al. 1967) has been compared. Considering the the limits of the shape factor as rough error bars for sodium chloride and bubbled sea salt, the CCN activity of artificial sea salt, Tropic Marin sea salt, and sodium chloride are not significantly different. This work has been supported by the Carlsberg Foundation.