Plasma Bubble Formation Research Articles

Efficient plasma electron accelerator driven by linearly chirped multi-10-TW laser pulses

The temporal rearrangement of the spectral components of an ultrafast and intense laser pulse, i.e., the chirp of the pulse, offers significant possibilities for controlling its interaction with matter and plasma. In the propagation of ultra-strong laser pulses within the self-induced plasma, laser pulse chirp can play a major role in the dynamics of wakefield and plasma bubble formation, as well as in the electron injection and related electron acceleration. Here, we experimentally demonstrate the control of the generation efficiency of a relativistic electron beam, with respect to maximum electron energy and current, by accurately varying the chirp value of a multi-10-TW laser pulse. We explicitly show that positively chirped laser pulses, i.e., pulses with instantaneous frequency increasing with time, accelerate electrons in the order of 100 MeV much more efficiently in comparison to unchirped or negatively chirped pulses. Corresponding Particle-In-Cell simulations strongly support the experimental results, depicting a smoother plasma bubble density distribution and electron injection conditions that favor the maximum acceleration of the electron beam, when positively chirped laser pulses are used. Our results, aside from extending the validity of similar studies reported for PW laser pulses, provide the ground for understanding the subtle dynamics of an efficient plasma electron accelerator driven by chirped laser pulses.

COSMIC observation of stratospheric gravity wave and ionospheric scintillation correlation

A correlation study is performed to investigate possible connections between the stratospheric gravity waves and the ionospheric plasma bubble induced GPS signal scintillations. Using the COSMIC 1 neutral temperature data (10–30 km), we extract gravity wave amplitudes with vertical wavelengths from 2.5 to 10 km within the latitudinal range from 37.5S to 37.5N. We then calculated the occurrence of high GPS L1 amplitude scintillation (S4 > 0.2) in the equatorial region (25S and 25N). The high S4 values showed consistent higher correlations with gravity waves at the equator than those away from the equator for all vertical wavelengths between 2010 and 2013. While the peak correlation is only ~0.2, the consistency over different wavelengths and years suggests a possible link, which could be through seeding of plasma bubbles and/or modulation of the neutral wind dynamo by gravity waves. We see the need for further study based on statistics of simultaneous observations of gravity waves, ionospheric scintillations, and other ionospheric and thermospheric parameters, which can lead to a better understanding of the plasma bubble formation mechanism.

Further complexities on the pre-reversal vertical drift modeling over the Brazilian region: A comparison between long-term observations and model results

The vertical component of the plasma drift, especially the evening-time pre-reversal drift, constitutes an important aspect of the nighttime electrodynamics of the equatorial ionosphere. Over the years, several studies using measurements and models have been performed to understand the characteristics of this process and its implications for the development of the instabilities leading to the plasma bubble formation and ionospheric scintillation. However, the Brazilian region presents some unique features that bring some difficulties for the vertical drift prognosis, which is required for the scintillation forecasting. These features are mainly related to the geomagnetic field lines topology that presents strong differences when compared to those of other equatorial longitudes. In this work, some of the difficulties for the pre-reversal vertical drift modeling and estimation are discussed; also, a dataset containing long-term observation (2001–2009) is compared with a widely used empirical model. The results show an intrinsic trend of underestimation by the model, which seems to be independent of latitude and seasonality thus suggesting an additional contribution arising from sources other than solely the geomagnetic topology. Also, the results indicate that the deviation can vary in the range of 0–40 m/s and the percentage error enhances with increasing values of pre-reversal vertical drift peak and reduces with increasing F10.7 values, thereby, indicating a clear possibility of meridional winds contribution which is not included in the empirical model used and may account for these differences.

Temporal Variation of Ionospheric Scintillation in Relation with Ionospheric Total Electron Content (TEC) over Ethiopia

In this study the amplitude scintillation intensity index (S4) and ionospheric total electron content (TEC) data of the year 2012 obtained from Global Positioning System Scintillation Network and Decision (GPS-SCINDA) receiver was analyzed. The diurnal, monthly and seasonal variation of amplitude scintillation intensity index S4 and ionospheric total electron content (TEC) observed from the analyzed data. It is found that intense scintillation occurred during the day time with a small frequency and very frequent occurrences of relatively moderate scintillation during the night time but the vertical total electron content weak at night time than day time. it is observed that ionospheric scintillation intensity index in March, April, February, September– December recorded scintillation events at moderate and intense levels, and these events were generally localized within 1930 LT–2400 LT and All other months experienced weak scintillation of various degrees of occurrences. The scintillation showed a seasonal variation characterized by intense values in March equinox compare to that of in June solstice season. The diurnal variations of amplitude scintillation intensity index S4 in relation with TEC showed that there is more scintillation and TEC around 15:00 to 20:00 UT and this is may be due to the enhancement of equatorial spread F and formation of plasma bubble during the night.

Ionospheric plasma dynamics and instability caused by upward currents above thunderstorms

AbstractThunderstorms are electric generators, which drive currents upwardly into the ionosphere. In this paper, we examine the effects of thunderstorm upward current on the ionosphere. We use a thunderstorm model to calculate the three‐dimensional current flows in the atmosphere and to simulate the upward current above the thunderstorm with the tripole‐charge structure. The upward current flows into the ionosphere, while the associated electric field causes the plasma E × B motion. The caused plasma motion redistributes the plasma density, leading to ionospheric density variations. In the nighttime ionosphere, the E × B motion may also cause the formation of plasma bubbles.

Numerical simulation of equatorial plasma bubbles over Cachimbo: COPEX campaign

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 355km at around 18:35 LT, and for the prereversal peak enhancement of the vertical plasma drift (Vp) less than 30m/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<30m/s and Vp>30m/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>30m/s. In the analyzed cases we have considered the competition of other geophysical parameters in the generation of plasma structures.

UP-03.081 Transureteral Ureterolithotripsy of Ureteral Calculi: Which Is Best, Pneumatic or Holmium Laser Technique?

Urinary calculi are important problem in urology. Ureteral stones can cause obstructive uropathy and subsequent deterioration of renal function. Extracorporeal shockwave lithotripsy (SWL) and rigid and flexible ureteroscopy have greatly improved the urologist's ability to treat ureteral calculi. However, the success rate of SWL for impacted ureteral calculi is reportedly low. For stone fragmentation, a variety of lithotripters can be used, including ultrasonic, electrohydraulic, pneumatic and laser lithotriptors. Pneumatic lithotripsy and holmium:YAG lithotripsy have reported favorable outcomes. The Swiss Lithoclast developed in Lausanne, Switzerland, fragments the stones by oscillary movements of metal probe against the stones like a jack hammer. The thermal effect produced by holmium:YAG laser pulses are due to formation of plasma bubble. This bubble at the tip of the fiber connected to the holmium:YAG laser makes it possible to work on stones and soft tissues. Our aim was compare two types of lithotripter: holmium: YAG laser and pneumatic one in transurethral ureterolithotripsy (TUL) for management of ureteral calculi ≥1cm.

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

[1] 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.

The impact of gravity waves rising from convection in the lower atmosphere on the generation and nonlinear evolution of equatorial bubble

Abstract. The nonlinear evolution of equatorial F-region plasma bubbles under varying ambient ionospheric conditions and gravity wave seeding perturbations in the bottomside F-layer is studied. To do so, the gravity wave propagation from the convective source region in the lower atmosphere to the thermosphere is simulated using a model of gravity wave propagation in a compressible atmosphere. The wind perturbation associated with this gravity wave is taken as a seeding perturbation in the bottomside F-region to excite collisional-interchange instability. A nonlinear model of collisional-interchange instability (CII) is implemented to study the influences of gravity wave seeding on plasma bubble formation and development. Based on observations during the SpreadFEx campaign, two events are selected for detailed studies. Results of these simulations suggest that gravity waves can play a key role in plasma bubble seeding, but that they are also neither necessary nor certain to do so. Large gravity wave perturbations can result in deep plasma bubbles when ionospheric conditions are not conducive by themselves; conversely weaker gravity wave perturbations can trigger significant bubble events when ionospheric conditions are more favorable. But weak gravity wave perturbations in less favorable environments cannot, by themselves, lead to strong plasma bubble responses.

Atypical current sheets and plasma bubbles: A self‐consistent kinetic model

As revealed by CLUSTER observations, thin current sheets in the magnetotail may strongly differ from the conventional Harris profile due to the effects of embedding and bifurcation. At the same time, they often have no signatures of collisionless magnetic reconnection. A universal phenomenon involving such atypical current sheets, which is connected but not identical to reconnection, is the formation of plasma bubbles. We present a self‐consistent kinetic model of plasma bubbles based on a 2‐D generalization of earlier atypical current sheet models that also takes into account the south‐then‐north sense of Bz perturbations typical for earthward traveling compression regions and fast flows in the central plasma sheet. The new model predicts that the dominant structural element of bubbles is a region of the local reduction of the cross‐tail current provided by the current bifurcation effect.

Creation and expansion of a magnetized plasma bubble for plasma propulsion

We discuss the coupled expansion of a plasma cloud and a neutral gas, both originating from a point-like source located in space and submitted to the action of an external flux of ionizing radiation. This problem is relevant to the artificial magnetospheric propulsion scheme for solar system exploration. We establish the relevant space and time scales for particle diffusion and plasma bubble formation. Emphasis is placed on the low ionization and high collisionallity of the plasma near the point source, leading to the existence of a small ionosphere surrounding the source, where (contrary to the more common views of this propulsion scheme) the ions are not magnetized. The possibility of direct plasma creation by an initial purely neutral gas release is also envisaged.

Plasma bubble formation induced by holmium laser: an in vitro study

Objectives To use the elementary physical measurements of temperature and size to prove that the thermal effects produced by the holmium laser's pulses are due to the formation of a plasma bubble. The physical phenomenon related to high temperatures generated during procedures with the holmium laser (holmium:yttrium-aluminum-garnet) was the object of our interest. Methods Using a double micrometric slide attached to a 550-μm optic fiber and two thermocouples submerged in water, a series of pulses of 0.8 J at 10 to 30 Hz was delivered from a holmium:yttrium-aluminum-garnet laser, and we recorded temperatures on both frontal and lateral planes. Subsequently, samples of prostatic tissue and small stones were treated with 1.5 J at 20 Hz on both frontal and lateral planes. Results Treatment with 1.5 J at 30 Hz (frontal plane) and with 1.5 J at 20 Hz (lateral plane) produced the ablation of the structure of the thermocouple at 2 mm and 1 mm, respectively, indicating plasma formation. The dimensions of the bubble after the delivery of 1.5 J at 20 Hz was 2 × 1.5 mm. Coagulation of the prostatic tissue took place at 1 mm from the plasma bubble, on both frontal and lateral planes. Conclusions The plasma bubble that forms at the tip of the fiber connected to the holmium:yttrium-aluminum-garnet laser makes it possible to work on stones and soft tissues. The coagulation of the prostatic tissue is caused by the hot water-vapor bubble that forms on the edge of the plasma bubble. During lithotripsy, guidewires and baskets within the expansion area of the plasma bubble risk damage.

IONOSPHERIC OBSERVATION USING KOREAN SATELLITES

We report the results of the ionospheric measurement obtained from the instruments on board the Korea Multi-Purpose Satellite - 1 (KOMPSAT-l). We observed a deep electron density trough in the nighttime equatorial ionosphere during the great magnetic storm on 15 July 2000. We attribute the phenomena to the up-lifted F-layer caused by the enhanced eastward electric field, while the spacecraft passed underneath the layer. We also present the results of our statistical study on the equatorial plasma bubble formation. We confirm the previous results regarding its seasonal and longitudinal dependence. In addition, we obtain new statistical results of the bubble temperature variations. The whole data set of measurement for more than a year is compared with the International Reference Ionosphere (IRI). It is seen that the features of the electron density and temperature along the magnetic equator are more prominent in the KOMPSAT-l observations than in the IRI model.

Holmium laser in endourology: The phenomena related to plasma bubble formation

Holmium laser in endourology: The phenomena related to plasma bubble formation

A high-frequency downhole sparker sound source for crosswell seismic surveying

Traditionally seismic exploration techniques have not been widely used in hard rock mining and exploration environments. To facilitate faster and more accurate shallow high-resolution seismic surveys a high-frequency electric discharge (sparker) seismic source was developed. The main design requirements of this source were that it (1) achieve rapid downhole firing, (2) fit down surface diamond drill holes (70mm diameter), (3) provide similar energy level and frequency content to a seismic detonator so as to produce useful sharp signals over a distance up to 200 meters, and (4) it should be highly repeatable and reliable.The sparker system consists of a surface control and power source, winch cable and depth encoder, and a downhole probe. The 22kg downhole probe, which has a diameter of 60mm and length of approximately 3m, produces a discharge energy output of 480J. The innovation with this sparker is that the 60μF 5000V discharge capacitor is contained within the downhole probe, thus overcoming the problem of significant power loss through the high resistance of the cable and the effects of inductance experienced by other surface capacitor arc discharge sources. The sparker described does not include a discharge chamber, but instead relies on the saline conditions of a fluid filled borehole to enable explosive plasma bubble formation to occur.Initial field tests in the hard rock environment of Kambalda Western Australia provided some very encouraging results. The ability of the sparker to operate in a borehole under hydrostatic heads in excess of 250m and to produce clearly received signal at distances in excess of 100m was demonstrated. The output signal of a single shot of the sparker compared very favourably with that produced by a seismic detonator under the same conditions. The firing rate in the field was found to be approximately 5 shots per minute. Repeatability of the signal was excellent.

Relationship between generation of equatorial F-region plasma bubbles and thermospheric dynamics

Simultaneous zenith measurements of the OI 630.0 nm and 557.7 nm nightglow emissions, using a multi-channel tilting filter type photometer and nighttime thermospheric neutral wind velocities from the Doppler shifts of the OI 630.0 nm emission line, using a Fabry-Perot interferometer, have been carried out at Cachoeira Paulista (23°S, 45°W), Brazil, during 1988–1991. These measurements constitute a unique opportunity to study the relationship between the generation of F-region plasma bubbles (regions of depleted electron densities) and thermospheric dynamics. During the period of March 1988 to June 1991, we have 9 nights on which there were nearly full nights of simultaneous observations of thermospheric wind velocities (zonal and meridional) and the OI 630.0 nm and 557.7 nm emissions showing formation of plasma bubbles. On the night of March 18, 1991, the zonal wind was unusually strong in the beginning of the night (300 m/s) and this night shows very strong formation of plasma bubbles, indicating that a strong zonal wind in some way may be connected with plasma bubble formation through the electric field created by the interaction between the zonal wind and the Earth's magnetic field. However, both the zonal and meridional winds on several nights with, and without plasma bubbles, are comparable. This feature possibly indicates only a secondary role of thermospheric winds in the generation of the equatorial ionospheric plasma depletions. It should be pointed out that an analysis of the nocturnal intensity variations of simultaneous mesospheric (E-region) emissions (OI 557.7 nm, O 2 atm. 864.5 nm, NaD 589.0 nm and OH (9-4) 775.0 nm) on all the nine nights studied, shows the presence of gravity waves, indicating possible relation between wave processes in the mesosphere and F-region irregularities.

Occurrence characteristics of low latitude ionosphere irregularities observed by impedance probe on board the Hinotori satellite.

The statistical analyses of occurrence characteristics of the plasma bubbles and blobs are made by using more than 1000 cases of observation data from the swept frequency impedance probe aboard the Hinotori satellite. The results show that formations of the plasma bubbles have the following characteristics. 1) The spatial distribution of the occurrence of the plasma bubbles is in the equatorial region within ±30° of the magnetic dip latitude centered around the magnetic equator, 2) the occurrence of the plasma bubbles is limited in the nighttime; favorable periods of the plasma bubble formation depend on the type of the plasma bubbles; multiple plasma bubbles (MPB) have tendency to be generated in pre-midnight, while quasi periodic plasma bubbles (QPB) show their maximum occurrence in the post-midnight period. Solitary plasma bubbles (SPB) occur, however, rather independently to the local time in so far as in the night period, 3) the magnetic activity also controls the occurrence of the plasma bubbles; the occurrence of MPB phenomena shifts the peak period to the midnight side with increasing magnetic activity and the occurrence of QPB phenomena which covers the period from midnight to the morning side shows the expansion of their occurrence into late morning period with increasing magnetic activity, 4) correlation of the occurrence of the plasma bubbles to the solar radiation flux represented by F10.7 solar radio flux is evident for MPB and QPB while there is no relation between F10.7 and the occurrence of SPB. Occurrence of the plasma blobs has a complementary nature with that of the plasma bubbles. The occurrence region of the plasma blobs is limited in the edge parts of the plasma bubble occurrence region being limited in the nighttime. The occurrence of the plasma blobs decreases with increasing magnetic activity, while there is a strong anti-correlation of the occurrence of the plasma blobs to the solar radiation (F10.7). The relation of occurrence of the plasma bubbles and blobs to the development of the equatorial anomaly and the asymmetrical distributions of the background electron density suggests the importance of the generalized Rayleigh-Taylor instability including the effects of the electric field and the neutral wind in addition to the gravitational force for the generation of the plasma bubbles and blobs.