Search

It remains a technical challenge to perform "superior mesenteric artery (SMA) first" approach for laparoscopic right hemicolectomy with complete mesocolon excision (CME) as the vascular anatomy of the right colon varies a lot, which may cause difficulty in early location of SMA and the risk of vascular damage during central vascular ligation (CVL). The purpose of this study was to describe a new "SMA first" approach for laparoscopic CME with CVL in right hemicolectomy with Treitz's ligament and ileocolic vascular pedicle as the anatomical landmarks for early identification of and exposure of SMA.This procedure was performed on 21 patients with right colon cancer between March 2020 and August 2021. To start, the transverse mesocolon was retracted to expose the ligament of Treitz, and the pedicle of ileocolic vessels was anteriorly grasped. Next, the peritoneum near the right border of the ligament of Treitz was divided along the left side of SMA until the peritoneum below the ileocolic vessels. Next, the mesenteric lymphatic adipose tissue outside of the sheath of SMA was dissected from medial to lateral. Then, laparoscopic right hemicolectomy with complete mesocolic excision (CME) was performed. Patients' preoperative baseline characteristics and intraoperative and postoperative complications were examined.The median operative time was 180 min, and the median intraoperative blood loss was 50 ml (interquartile range 40-90). Chylous leakage occurred in four patients, and all the patients resolved with percutaneous drainage. The total harvested lymph nodes was 21.0 (range 16-27). The median times to first flatus and liquid diet intake were both 3.0 days. The median number of postoperative hospital days was 10.0 days. No severe postoperative complications, such as abdominal infection, anastomotic leakage, or bleeding, were observed.This new "SMA first" approach is safe and technically feasible for laparoscopic CME with CVL in right hemicolectomy.

Purpose: To uncover the functional effect of homologous domain-associated protein kinase 2 (HIPK2) on the viability of cisplatin (DDP)-resistant gastric cancer (GC) cells and elucidate the possible mechanism of action.Methods: The effect of DDP on GC viability and apoptotic rate was evaluated using MTT and flow cytometry (FCM) assays. The potential effect of HIPK2 on DDP sensitivity and cell apoptosis was investigated in the presence of cisplatin while the effect of HIPK2 on p53 activation was determined by immunoblot assay.Results: HIPK2 expression was decreased in DDP-resistant GC cell while upregulation of HIPK2 reduced growth, but promoted apoptosis in DDP-resistant GC cells. Further investigations showed that HIPK2 promoted p53 activation, while suppression of p53 weakened the inhibitory effect of HIPK2 on DDP-resistance in GC cells.Conclusion: The results suggest that HIPK2 is a promising and important therapeutic factor for the regulation of the resistance of GC cells to DDP. Thus, may have a role to play in the management of gastric cancer Keywords: Gastric cancer, Cisplatin, HIPK2, Homologous domain-associated protein kinase 2, p53 pathway, Therapeutic target

Background Circular RNAs (circRNAs) are endogenous non-coding RNAs, which are associated with various biological processes, including microRNA (miRNA) interaction, protein binding and regulatory splicing. circRNA_0005529 (circ_0005529) is derived from vacuolar protein sorting 33 homologue B (VPS33B), and its biological role in gastric cancer (GC) has not been examined. In this study, the expression and location of circ_0005529 and microRNA-527 (miR-527) were determined by qRT-PCR and fluorescence in situ hybridization (FISH). Cell proliferation and cell migration were determined by MTT, EdU incorporation, colony formation, wound scratch and transwell assays. In addition, immunohistochemistry and western blotting were performed to determine the expressions of specificity protein 1 (Sp1), PCNA, c-myc, E-cadherin and N-cadherin. Western blotting and luciferase reporter assay were performed to study the interaction between circ_0005529 and miR-527 or miR-527 and Sp1. The functional effects of circ_0005529 on GC through regulating Sp1 were further evaluated using xenograft and metastatic mouse models in vivo. Results Our results showed that circ_0005529 was upregulated in GC tissues and cells, and had promoting effects on cell proliferation and cell migration. Mechanism analysis suggested that circ_0005529 could bind to microRNA-527 (miR-527) and reduce its expression. The interaction between miR-527 and Sp1 in GC was systematically studied. In addition, the results indicated that Sp1 upregulation could rescue the effects on cell proliferation and migration caused by circ_0005529. Moreover, the inhibitory effects of circ_0005529 downregulation on GC growth and metastasis were evaluated in mouse models. These findings suggested that the axis of circ_0005529/miR-527/Sp1 may serve as a promising treatment target for GC diagnosis and treatment. Conclusions These findings suggested that the signal axis of circ_0005529/miR-527/Sp1 may has the potential to be explored as a novel therapeutic target for GC diagnosis and treatment. Graphical abstract Mechanism diagram: During GC development, overexpressed circ_0005529 sponged miR-527 and then upregulated the expression of Sp1. Subsequently, epithelial-mesenchymal transition (EMT), cell proliferation and cell migration were promoted, which ultimately facilitated the tumor metastasis

After abdominoperineal resection, low anterior resection, and end colostomy for lower rectal cancer, it is necessary to reconstruct the pelvic peritoneum to avoid small bowel obstruction, perineal hernia, and radiation enteritis in patients for whom postoperative radiotherapy is planned. However, pelvic peritoneal closure is technically difficult in patients who lack enough peritoneum to cover the defect or have received neoadjuvant radiation and have a rigid pelvis.The impact of this innovation is to reconstruct the pelvic peritoneum with the distal ileal mesentery laparoscopically.After removal of the tumor, the distal ileal mesentery was selected to completely cover the defect. Subsequently, suturing of the ileal mesentery to the posterior wall of the urinary bladder and all sides of the pelvic cavity was performed. Finally, the patients were returned to the headfirst supine position to ensure that there was no small bowel falling into the pelvic dead space.All surgical procedures were successfully performed laparoscopically from January 2019 to April 2021. No perineal complications or intestinal obstructions occurred during the follow-up period.This novel technique was found to be safe and effective. Moreover, it provided an economical method for the reconstruction of the pelvic peritoneum using autologous material, which could preserve the small intestine in the abdomen to avoid related complications. Additional larger series of patients with longer follow-up are needed to validate the safety and feasibility of this method.

Eosinophilic gastroenteritis is not only easy to ignore in clinical practice, but also easy to miss in the process of pathological diagnosis. There is a need to consider it in the differential diagnosis of alimentary disease.

Background. Anastomotic leakage (AL) remains one of the serious complications after colonic surgery. Method. A prospective interventional study to assess a modified technique of creating the ileocolic, colic-colic, and colorectal side-to-side anastomoses using a circular stapler. The primary endpoint was to evaluate the safety and efficacy of this technique in the reduction of AL. Computed tomography scan was performed when AL was clinically suspected. Result. One hundred and forty-five patients who underwent colonic resection between January 2015 and August 2018 were included. One patient underwent surgery for severe inflammatory bowel disease, and the others underwent surgery for colonic cancer. The procedures were open surgeries, including right hemicolectomy (n = 79 [54.5%]), left hemicolectomy (n = 29 [20%]), sigmoidectomy (n = 30 [20.7%]), and transverse colectomy (n = 7 [4.8%]). In 23 patients with ascending colonic obstruction, emergency right colectomy with primary anastomosis was performed. Two surgeons performed the operations (52.4% and 47.6%, respectively), and intraoperative blood loss was 50 to 100 mL. The operative time was 160 to 240 minutes. There was no mortality postoperatively, and 26 (17.9%) patients developed complications. One patient who underwent transverse colonic cancer resection developed a clinical AL (0.7%). After ileostomy, the patient was discharged with no other serious complication. The median of postoperative hospital stay was 8 days (range = 5-18 days). Conclusion. This modified technique is a safe and efficient method for anastomotic configuration in colonic surgery.

Summary Background Heterotopic gastric mucosa in the upper esophagus (HGMUE) is reported to be related to gastroesophageal reflux disease (GERD). This study investigated the prevalence of GERD and the use of salivary pepsin to diagnose gastroesophageal reflux, especially proximal reflux, in HGMUE patients. Methods One hundred and fifty-three HGMUE patients and 50 healthy volunteers were studied. All subjects took a reflux symptom index questionnaire (RSI); underwent endoscopy, barium esophagogram, high-resolution manometry (HRM), and 24-hour multichannel intraluminal impedance-pH-metry (MII-pH); and salivary pepsin test. Results Ninety-five (62.1%) HGMUE patients but no control subjects were diagnosed with GERD. The salivary pepsin concentration, RSI score, DeMeester score, acid exposure time (AET), total reflux episodes, proximal acidic reflux episodes, and proximal weakly acidic reflux episodes were significantly higher in the HGMUE group than in the control group (P Conclusions GERD, especially GERD with proximal acid reflux and related symptoms, was common in HGMUE patients. The salivary pepsin test could be an additional useful test for testing reflux in HGMUE patients, but it will not replace the MII-pH.

In steady state, magnetic flux conservation must be maintained in Saturn’s magnetosphere. The Enceladus plumes add mass to magnetic flux tubes in the inner magnetosphere, and centrifugal force pulls the mass-loaded flux tubes outward. Those flux tubes are carried outward to the magnetotail where they deposit their mass and return to the mass loading region. It may take days for the magnetic flux to be carried outward to the tail, but the return of the nearly empty flux tubes can last only several hours, with speeds of inward motion around 200 km/s. Using time sequences of Cassini particle count rate, the difference in curvature drift and gradient drift is accounted for to determine the return speed, age, and starting dipole L-shell of return flux tubes. Determination of this flux-return process improves our understanding of the magnetic flux circulation at Saturn and provides insight into how other giant planets remove the mass added by their moons.

Parker Solar Probe (PSP) aims at exploring the nascent solar wind close to the Sun. Meanwhile, PSP is also expected to encounter small objects like comets and asteroids. In this work, we survey the ephemerides to find a chance of recent encounter, and then model the interaction between released dusty plasmas and solar wind plasmas. On 2019 September 2, a comet-like object 322P/SOHO just passed its perihelion flying to a heliocentric distance of 0.12 au, and swept by PSP at a relative distance as close as 0.025 au. We present the dynamics of dust particles released from 322P, forming a curved dust tail. Along the PSP path in the simulated inner heliosphere, the states of plasma and magnetic field are sampled and illustrated, with the magnetic field sequences from simulation results being compared directly with the in-situ measurements from PSP. Through comparison, we suggest that 322P might be at a deficient activity level releasing limited dusty plasmas during its way to becoming a “rock comet”. We also present images of solar wind streamers as recorded by WISPR, showing an indication of dust bombardment for the images superposed with messy trails. We observe from LASCO coronagraph that 322P was transiting from a dimming region to a relatively bright streamer during its perihelion passage, and simulate to confirm that 322P was flying from relatively faster to slower solar wind streams, modifying local plasma states of the streams.

At the Earth’s magnetopause, flux tubes observed by the Magnetospheric Multiscale (MMS) spacecraft in “entangled” pairs have been interpreted as a precursory stage to the formation of a new pair of...

Additional file 5. Supplementary Tables.

Although laparoscopic Nissen fundoplication (LNF) is a kind of minimally invasive surgery, some transition time may still be required to allow the fundoplicated stomach to adapt to the new anatomical position. We observed transient delayed gastric emptying (DGE) post-LNF in our preliminary study. This study aimed to investigate the occurrence rate and development of transient DGE post-LNF. Patients who underwent LNF for gastroesophageal reflux disease (GERD) at our institution were recruited consecutively. They were treated with standardized LNF and prospectively followed up for 2 months. Proper diet guidance and/or pharmacologic therapy were given during these 2 months. GERD Health-Related Quality of Life (GERD-HRQL), DGE symptoms, and DGE status were evaluated preoperatively and postoperatively. Fifty-one patients underwent LNF and completed a 2-month follow-up. LNF succeeded in all patients. Prior to LNF, no DGE was identified. At the 1-month follow-up, LNF led to a significant reduction in the GERD-HRQL total score but a significantly increased DGE score. Endoscopically, DGE was identified in forty-seven (n = 47, 92.2%) patients. At the 2-month follow-up, the GERD-HRQL scores continued to show decreases compared to the 1 month. The DGE score returned to the baseline value. Endoscopically, no DGE was identified in any patients (n = 0, 0.0%). Transient DGE is a very common one-month post-LNF but can recover quickly in the second month following LNF.

Flux transfer events (FTEs), as flux ropes (FRs), are considered key agents for solar wind energy to enter the terrestrial magnetosphere. Recent observations identify entangled flux tubes that coll...

The abnormal expression of cadherin-11 (CDH11) affects the progression of several types of cancer. However, the expression pattern and prognostic value of CDH11 in gastric cancer (GC) have not been reported. In the present study, the expression of CDH11 in patients with GC and its effect on their survival were analyzed using public cancer databases. The expression of CDH11 in GC tissues was significantly higher compared with that in normal gastric tissues. The expression of CDH11 was higher in advanced GC compared with early GC, and increased CDH11 was associated with tumor progression and poor prognosis in patients with GC. The high level of methylation in the promoter of CDH11 in GC tissues was not sufficient to reverse the upregulation of CDH11 caused by transcriptional activation. Finally, the expression pattern and prognostic significance of CDH11 in GC were validated using data from patients with GC recruited for the present study. Collectively, the present results demonstrated that CDH11 was upregulated in GC tissues, and suggested that high CDH11 expression may be associated with progression and poor prognosis in GC.

Magnetic reconnection is a mechanism that allows rapid and explosive energy transfer from the magnetic field to the plasma. The magnetopause is the interface between the shocked solar wind plasma and Earth’s magnetosphere. Reconnection enables the transport of momentum from the solar wind into Earth’s magnetosphere. Because of its importance in this regard, magnetic reconnection has been extensively studied in the past and is the primary goal of the ongoing Magnetospheric Multiscale (MMS) mission. During magnetic reconnection, the originally anti-parallel fields annihilate and reconnect in a thinned current sheet. In the vicinity of a reconnection site, a prominently increased curvature of the magnetic field (and smaller radius of curvature) marks the region where the particles start to deviate from their regular gyro-motion and become available for energy conversion. Before MMS, there were no closely separated multi-spacecraft missions capable of resolving these micro-scale curvature features, nor examining particle dynamics with sufficiently fast cadence.In this study, we use measurements from the four MMS spacecraft to determine the curvature of the field lines and the plasma properties near the reconnection site. We use this method to study FTEs (flux ropes) on the magnetopause, and the interaction between co-existing FTEs. Our study not only improves our understanding of magnetic reconnection, but also resolves the relationship between FTEs and structures on the magnetopause.

Interplanetary Field Enhancements are phenomena in the interplanetary magnetic field, first discovered near Venus, during an extremely long duration (12 hours) and large size (about 0.1 AU) passage across the Pioneer Venus spacecraft. Three and a half hours later and 21 x 106 km farther from the Sun, this structure, somewhat weaker and off to the side of the expected radial path of any solar initiated disturbance, was seen by first Venera 13 and then Venera 14, trailing behind V13. Since this discovery, many smaller such disturbances have been observed and attributed to collisions of small rocks in space at speeds of about 20 km/s at 1 AU and faster, closer to the Sun. All sightings with magnetometers and other space plasma instruments give very precise measurements of the radial structure (of usually the magnetic field), but the scale transverse to the solar radius is poorly defined, as is the temporal evolution of the structure from single spacecraft data.On January 16, 2018, near Earth, 12 spacecraft equipped with plasma spectrometers and magnetometers observed the passage of a single Interplanetary Field Enhancement. The magnetic field profiles at the four 1 AU spacecraft were very similar. The profiles were obtained at different times appropriate to their locations. The 4 Cluster spacecraft were closer to the Earth and in a region in which the solar wind had slowed down because of the Earth’s bow wave (shock) in the solar wind. The disturbance in the shocked solar wind occurred at the time expected if the IFE structure had not been slowed by the plasma, but rather had proceeded with the momentum it had prior to the shock crossing. If the disturbance causing particles are small bits of rock (not protons), then they should have kept most of their momentum in crossing the bow shock. We view this as a complete test of the dust producing collisional origin of these Interplanetary Field Enhancements, and a clear demonstration of how the solar wind clears out the dust in the inner solar system produced by the continuing destructive collisional process.

The hot electron beams that Dawn detected at Ceres can be explained by fast-Fermi acceleration at a temporary bow shock. A shock forms when the solar wind encounters a temporary atmosphere, similar to a cometary coma. We use a magnetohydrodynamic model to quantitatively reproduce the 3-D shock surface at Ceres, and deduce the atmosphere characteristics that are required to create such a shock. Our most simple model requires about 1.8 kg/s, or 6×1025/s water vapor production rate to form such a shock. Such an estimate relies on characteristics of the solar wind-Ceres interaction. We present several case studies to show how these conditions affect our estimate. In addition, we contrast these cases with the smaller and narrower shock caused by a subsurface induction. Our multi-fluid model reveals the asymmetry introduced by the large gyroradius of the heavy pickup ions, and further constrains the IMF direction during the events.

D3 lymphadenectomy is important for accurate staging and provides long-term benefits, especially for T3–4/N + tumors.1,2 Both D3 lymphadenectomy as well as complete mesocolic excision (CME) require central ligation of vessels at their origins to ensure radical resection.3 Currently, superior mesentery vein (SMV) is navigated by ileocolic vessels while its sheath is dissected stepwise from caudal to cranial.4–6 This report describes a new medial-to-lateral approach for laparoscopic right hemicolectomy with D3 + CME. The patient was a 47-year-old man with diagnosis of hepatic flexure cancer (cT4N1M0). First, the pedicle of the middle colic vessels and ileocolic vessels were both grasped, then the sheath of SMV was dissected at its left side as there are fewer blood vessels entering here compared with its right side. Second, after identification of middle colic artery (MCA), SMV was skeletonized from medial to lateral and no. 213 and no. 203 lymph nodes were dissected. Third, MCA and ileocolic vein and artery (ICV and ICA) were ligated at their roots. After separating the transverse mesocolon from the duodenum, the branches of the Henle trunk were exposed and no. 223 lymph nodes were dissected. Accessory right colic vein, right colic vein, and middle colic vein were ligated respectively. Fourth, the ascending mesocolon was separated from the retroperitoneal tissues through the front side of Toldt’s fascia, the mesocolon was mobilized completely, and the tumor was removed en bloc. The operation time was 175 min, with estimated blood loss of 50 ml. The patient recovered well without bleeding complications and was discharged on postoperative day 7. Histology revealed moderately differentiated adenocarcinoma with 5 of 24 lymph nodes involved (pT3N2M0). The medial-to-lateral approach presented in the video might be helpful for standardization of laparoscopic D3 + CME for right-sided colon cancer.

Magnetic reconnection occurs in current sheets in various plasma environments, and the reconnection process is controlled by the current sheet characteristics. Most theoretical and simulation studies of magnetic reconnection are based on the neutral current sheet model in which the current is primarily carried by ions. Current sheets in natural plasmas (e.g., in Earth's magnetotail), however, are usually charged with nonzero electric field, and usually the current therein is primarily carried by electrons. Here using particle-in-cell simulations, we study magnetic reconnection in a charged, electron-dominant current sheet and show that reconnection in this current sheet is weaker, has a larger diffusion region, and occurs more easily than reconnection in the neutral, ion-dominant current sheet. Two other current sheet characteristics, the background density and background temperature, also affect the reconnection process significantly.

Characterized by a cusp-shaped enhancement in the magnetic field strength, the magnetic structure in the solar wind, called an interplanetary field enhancement (IFE), has been investigated since its discovery. To understand its three-dimensional magnetic field geometry, we study an IFE detected by five spacecraft simultaneously. Field lines are seen draping around in the upstream region and rotating in the ambient convection electric field direction in the downstream region. Earlier studies suggest that IFEs are created when the solar wind accelerates newly formed dust clouds. Both signatures found in our study support this hypothesis: the field line draping is caused by dust-solar wind momentum exchange, while the field line rotation is a typical signature of dusty plasma pickup. The force that exchanges the momentum is approximately 106 N. This study illustrates the nature of the interaction between two flowing plasmas of very different mass-to-charge ratio.

Rationale: Oral ingestion of glyphosate can induce gastrointestinal symptoms such as vomiting, abdominal pain, and hematochezia. Timely and effective treatment of pyloric stenosis caused by glyphosate poisoning is important. Patient concerns: The patient had a poor appetite, accompanied by nausea and vomiting of a small amount of dark brown material that resembled blood clots several times a day. Gastroscopy revealed gastric ulcer, a large pyloric antrum ulcer, and a deformed stomach cavity. Diagnosis: Pyloric stenosis due to glyphosate poisoning in a 36-year-old man. Interventions: The patients received distal gastrectomy and subsequently transferred to the ICU for further treatment. A mechanical ventilator was used to assist breathing. Outcomes: Follow-up was conducted 3 years after surgery. The patient had no problem with food ingestion and experienced no discomfort, such as vomiting, nausea, coughing, or expectoration. Lessons: Gastrectomy is necessary to treat pyloric stenosis caused by glyphosate poisoning.

Strongly conducting or magnetized obstacles in a flowing plasma generate structures called Alfven wings, which mediate momentum transfer between the obstacle and the plasma. Nonconducting obstacles such as airless planetary bodies can generate such structures, which, however, have so far been seen only in sub-Alfvenic regime. A novel statistical analysis of simultaneous measurements made by two ARTEMIS satellites, one in the solar wind upstream of the Moon and one in the downstream wake, and comparison of the data with results of a three-dimensional hybrid model of the interaction reveal that the perturbed plasma downstream of the Moon generates Alfven wings in super-Alfvenic solar wind. In the wake region, magnetic field lines bulge toward the Moon and the plasma flows are significantly perturbed. We use the simulation to show that some of the observed bends of the field result from field-aligned currents. The perturbations in the wake thus arise from a combination of compressional and Alfvenic perturbations. Because of the super-Alfvenic background flow of the solar wind, the two Alfven wings fold back to form a small intersection angle. The currents that form the Alfven wing in the wake are driven by both plasma flow deceleration and a gradient of plasma pressure, positive down the wake from the region just downstream of the Moon. Such Alfven wing structures, caused by pressure gradients in the wake and the resulting plasma slowdown, should exist downstream of any nonconducting body in a super-Alfvenic plasma flow.

It is well accepted that cold plasma sourced by Enceladus is ultimately lost to the solar wind, while the magnetic flux convecting outward with the plasma must return to the inner magnetosphere. However, whether the interchange or reconnection, or a combination of the two processes is the dominant mechanism in returning the magnetic flux is still under debate. Initial Cassini observations have shown that the magnetic flux returns in the form of flux tubes in the inner magnetosphere. Here we investigate those events with 10 year Cassini magnetometer data and confirm that their magnetic signatures are determined by the background plasma environments: inside (outside) the plasma disk, the returning magnetic field is enhanced (depressed) in strength. The distribution, temporal variation, shape, and transportation rate of the flux tubes are also characterized. The flux tubes break into smaller ones as they convect in. The shape of their cross section is closer to circular than fingerlike as produced in the simulations based on the interchange mechanism. In addition, no sudden changes in any flux tube properties can be found at the “boundary” which has been claimed to separate the reconnection and interchange-dominant regions. On the other hand, reasonable cold plasma loss rate and outflow velocity can be obtained if the transport rate of the magnetic flux matches the reconnection rate, which supports reconnection alone as the dominant mechanism in unloading the cold plasma from the inner magnetosphere and returning the magnetic flux from the tail.

Charged dust exists in various regions in the Solar System. How this charged dust interacts with the surrounding plasma is not well understood. In this study we neglect the charging process and treat the charged dust as a fluid interacting with the ambient magnetized plasma fluid. The model reproduces the expected plasma deceleration with both positively charged and negatively charged dust, but a new effect arises. Negatively charged dust causes the magnetic field to bend in the direction of the convection electric field, while positively charged dust causes the opposite magnetic field bending. Consequently, the interaction does not only result in a perpendicular shift in the downstream current system, but also a rotation in these currents. We present quantitative results using the multi-fluid MHD code BATSRUS for both subsonic and supersonic interactions. We find that the same perpendicular bending exists for all counter-streaming interaction problems, independent of the shape of the dust cloud. The new model can be applied to plasma interaction studies including, but not limited to, charged dust particles in the solar wind, cometary plasma, the Enceladus plume, and active plasma releases, such as the Active Magnetospheric Particle Tracer Experiment (AMPTE) mission. The predicted behavior is consistent with observations at Enceladus.

The Deep Space 1 (DS1) spacecraft passed the sunward side of Comet 19P/Borrelly in 2001. Along its relatively north–south orbit, a set of plasma density and velocity measurement revealed a northward shift of the plasma boundaries and the mass loading peak. Both onboard and ground based telescopes found evidence for asymmetric distribution of the dust and neutrals. In this paper, five mass-loading patterns are studied to present the first study of the effect of non-spherical neutral distribution profiles on the solar wind-cometary plasma interaction environment. Using magnetohydrodynamic simulations, it is found that a combination of Gaussian and cosine neutral jet distribution, with cosine being the major part, can fit the DS1 general plasma measurement well, with a total gas production rate of around 5 × 10 28 s −1 . These model-data comparisons indicate that the general plasma distribution around Comet Borrelly can be explained with its aspherical neutral jet distribution. However, such neutral jets by themselves are insufficient to produce the density offset in the central peak. Kinetic effects, such as finite gyroradius may be required to create the offset plasma peak.

On 2007 January 12, comet C/2006 P1 (McNaught) passed its perihelion at 0.17 AU. Abundant remote observations offer plenty of information on the neutral composition and neutral velocities within 1 million kilometers of the comet nucleus. In early February, the Ulysses spacecraft made an in situ measurement of the ion composition, plasma velocity, and magnetic field when passing through the distant ion tail and the ambient solar wind. The measurement by Ulysses was made when the comet was at around 0.8 AU. With the constraints provided by remote and in situ observations, we simulated the plasma environment of Comet C/2006 P1 (McNaught) using a multi-species comet MHD model over a wide range of heliocentric distances from 0.17 to 1.75 AU. The solar wind interaction of the comet at various locations is characterized and typical subsolar standoff distances of the bow shock and contact surface are presented and compared to analytic solutions. We find the variation in the bow shock standoff distances at different heliocentric distances is smaller than the contact surface. In addition, we modified the multi-species model for the case when the comet was at 0.7 AU and achieved comparable water group ion abundances, proton densities, plasma velocities, and plasma temperatures to the Ulysses/SWICS and SWOOPS observations. We discuss the dominating chemical reactions throughout the comet-solar wind interaction region and demonstrate the link between the ion composition near the comet and in the distant tail as measured by Ulysses.

[1] Applying a 2.5-D hybrid simulation, we have studied the particle acceleration caused by magnetic reconnection. The results show that the reconnection process will not only heat all the particles, but also accelerate a few particles to comparatively high velocities (about 2.0vA). Such selective accelerating makes the velocity distribution of all particles changed from the Maxwellian distribution, to a shell or quasi-shell distribution. In addition, this shape varies with the change of particle positions. In order to study the accelerating process occurring near the X-type neutral point, we have observed the time-variation of velocities and positions of selected particles. Among the particles flowed out inside the reconnection region, some are trapped in the magnetic mirror, with a convolution radius that outsteps the width of the reconnection region. These particles can thus construct the lowspeed part of the fluid near the boundary of outflow regions. On the other hand, there are three kinds of drifting trajectory for particles entering the reconnection region beside the X-type neutral point: flee along the field lines, be trapped in the magnetic mirror, and traverse the local field lines. The ratios of particles undergoing the three kinds of trajectory are about 70%, 20%, 10%, respectively.

[1] In 2009 and 2010, the Cassini spacecraft made seven targeted Enceladus flybys along trajectories parallel to the equatorial plane. The magnetometer on board Cassini made a complete set of vector field distribution measurements on these tracks and observed significant perturbations that further constrained the location of the momentum-exchange region. These observations were made not only above and below the moon Enceladus, but also above and below the momentum-loading center. The observed field perturbations are consistent with previous interpretations of the interaction. Southernly-biased Io-type, Alfven-wing signatures are penetrated by Cassini. In addition to the draping due to the slowing down, the magnetic field drapes away from Saturn, indicating that the dust in the plume is predominantly negatively charged. No Saturnward or anti-Saturnward tilt of the plume is identified.

[1] Between May and October in 2007 and 2008, the five THEMIS spacecraft recorded a total of 3701 instances of bipolar magnetic variations in the magnetopause normal direction associated with enhancements of field magnitude that are interpreted as flux transfer events (FTEs) on the magnetopause and/or associated perturbations in the background magnetosphere and magnetosheath. When spacecraft traversed the FTE structures, the velocity components tangential to the magnetopause were generally antisunward, consistent with the sheath flow direction. On the other hand, when the spacecraft were located within the low-latitude boundary layer (LLBL) in the magnetosphere and remotely sensed the perturbations related to FTEs on the magnetopause, the velocity tangential to the magnetopause was found to be antisunward near the magnetopause but sunward further in from the magnetopause. The normal component variations for both groups had the same bipolar structure with inward flows followed by outward flows. This pattern has the form of a flow vortex just inside the magnetopause associated with an FTE moving in an antisunward direction at or outside of the magnetopause. A 2-dimensional magnetohydrodynamic (MHD) simulation code has been developed to understand the flow perturbations outside an FTE. Our simulation starts from an explicit solution, in which it is assumed that the plasma is inviscid and incompressible and no flow vortex is present. Only when we impose finite viscosity near the FTEs do flow vortices develop. However, the origin of this viscosity remains unknown.

[1] The major momentum‐loading source in Saturn’s magnetosphere, Enceladus, has been studied with seven Cassini flybys between 2005 and 2008. In this paper, we first use parameter tests with our 3‐D magnetohydrodynamic simulation to demonstrate and determine the sensitivity of the interaction to both electron impact rates and charge‐ exchange rates. We also investigate the reasons behind our previous discovery that in the plume, within about two Enceladus radii of the plume’s source, the momentum‐loading rates per unit ion and neutral density are orders of magnitude lower than at greater distances. We find that depletion of hot electrons and variations in charge‐exchange rates are two possible explanations for such a reduction of the momentum‐loading rates. Assisted by the Cassini observations, we use our understanding of the plasma interaction to determine the temporal variation of Enceladus’ neutral plume, which is important in understanding its origin, as well as the geological evolution of this icy moon. We base our study on magnetometer observations during all seven flybys to present the first comparative analysis to all flybys in 2005 and 2008. It is found that the maximum variation in gas production rates is one third the largest rate. The plasma momentum‐ loading rate ranges from 0.8 to 1.9 kg/s, which is consistent with previous studies.

[1] In 2008, the Cassini spacecraft made four close Enceladus flybys along similar trajectories. During these flybys the magnetometer recorded the time-varying magnetic field associated with the plasma interaction with Enceladus and its plume. Close to Enceladus, the Cassini magnetometer observed 4% to 7% enhancement in the magnetic field magnitude, associated with the slowing down of the ambient plasma. Herein we examine these four flybys, estimate the deceleration of the flow, locate the momentum-loading center for each pass, and compare their pass to pass variability. Even though the spacecraft trajectories were similar, two different types of perturbations were observed at distances greater than 5 Enceladus radii downstream, and to the north of the moon. Ion-cyclotron waves were observed during each of the flybys, with pass to pass wave amplitudes varying in a similar manner as the enhancement of the field magnitude.

[1] The interaction of Saturn's inner magnetosphere with its moons ranges from the addition of significant quantities of gas, dust, and plasma, causing significant consequences for the dynamics and energetics of the entire Saturnian magnetosphere, to the simple absorption of plasma and energetic particles by the icy moons with non-electrically conducting interiors. The interaction with these moons is complex with the contribution of many physical processes, depending on the geometry of any plume, the structure of the atmosphere, and its interaction with the surface and interior of the moon, the latter by induced fields. Our ultimate goal is to understand the complexities of this interaction and its temporal variations, especially at Enceladus. In this paper we use magnetohydrodynamics (MHD) code for addressing the flow around obstacles that are simpler than the Enceladus interaction. These simulations both help us understand the interaction with other icy moons and prepare us for the simulation of the flow around Enceladus. The processes involved include ordinary collisions, impact ionization, photoionization, and charge exchange. We examine a series of simple canonical interactions before we later apply our simulation where the multiple processes are occurring simultaneously with asymmetric geometries. We apply our 3-D MHD model to simulate the interaction between the Saturnian corotational plasma flow for the following cases: an absorbing body having an insulating surface; ion pickup via photo and impact ionization from a spherically symmetric neutral cloud; charge exchange with such a neutral cloud; and ion pickup at an insulating, absorbing body with an atmosphere acted upon by the sum of the three ionization processes. In addition to validating the model and obtaining a deeper understanding of the consequences of each interaction, we can immediately make some conclusions about the Enceladus interaction. We find that the magnetometer data are most consistent with the surface of Enceladus being absorbing and insulating, rather than the surface being reflecting and electrically conducting. For the conditions in the corotating flow at Enceladus, the perturbation to the plasma flow produced by photo/impact ionization is an order of magnitude smaller than that produced by charge exchange. Moreover, the perturbation to the magnetic field Bz component by a spherically symmetric mass loading source alone is an order of magnitude smaller than that observed in the neighborhood of the plume. Thus, the perturbation observed in the magnetometer data is primarily due to the mass loading in the plume, which is primarily ion-neutral charge exchange. The geometry and source strength of the plume are investigated in a following paper.

[1] The Saturnian moons in the inner magnetosphere are immersed in a plasma disk that rotates much faster than the moon's Keplerian speed. The interaction of the rotating plasma with the moons results in a disturbance in the Saturnian magnetospheric plasma that depends on the nature of obstacle that the moon represents. In particular at Enceladus, such perturbations in the magnetic field and flowing plasma enable us to infer the 3-D shape of the Enceladus plume and its outgassing rate. In this paper, we apply our 3-D magnetohydrodynamic model to extensively study the effects of different plume and disk plasma conditions on the interaction. By finding the best agreement with the observations of two diagnostic flybys, one with its point of closest approach on the upstream side and the other on the downstream side, we determine the plume intensity and configuration. We find that mass loading in the plume is less efficient close to the surface of the moon, where the neutral density is the highest. For E2 and E5, the opening angle of the plume is about 20°, and the plume is tilted toward the corotating direction. The upstream density has a significant effect on the mass loading rate, while its effect on the magnitude of the magnetic perturbation is less significant. An upstream velocity component in the Saturn direction helps to explain the observed magnetic perturbation in the By component and signals the need to consider Enceladus's effect on the global plasma circulation in addition to the local effect. Quantitative comparisons of the simulated and observed interaction are provided.

By traversing the plume erupting from high southern latitudes on Saturn's moon Enceladus, Cassini orbiter instruments can directly sample the material therein. Cassini Plasma Spectrometer, CAPS, data show that a major plume component comprises previously-undetected particles of nanometer scales and larger that bridge the mass gap between previously observed gaseous species and solid icy grains. This population is electrically charged both negative and positive, indicating that subsurface triboelectric charging, i.e., contact electrification of condensed plume material may occur through mutual collisions within vents. The electric field of Saturn's magnetosphere controls the jets' morphologies, separating particles according to mass and charge. Fine-scale structuring of these particles' spatial distribution correlates with discrete plume jets' sources, and reveals locations of other possible active regions. The observed plume population likely forms a major component of high velocity nanometer particle streams detected outside Saturn's magnetosphere. Citation: Jones, G. H., et al. (2009), Fine jet structure of electrically charged grains in Enceladus' plume, Geophys. Res. Lett., 36, L16204, doi:10.1029/2009GL038284.

Two Sun-grazing comets were recently imaged in the low solar corona by space telescopes in unprecedented detail, revealing a wide range of new phenomena. This sparked growing interest in the interaction of comets with the coronal plasma and magnetic field and their diagnostic potential as solar probes. However, interpretation of such rich observational data requires profound understanding of relevant physical processes in an unexplored regime. Here advanced numerical modeling can provide critical clues. To this end, we present a prototype, multi-fluid, magnetohydrodynamic model of a steady-state comet in the low solar corona. These simulation results are compared with previously modeled comets in the solar wind environment. By inspecting their projection and column densities, we find a dominance of O6 + ions in the cometary tail, which can explain the observed extreme ultraviolet emission. The tail is found to be comparable to recent EUV images of these comets. In addition, the comet tail appears wider when the observer's line of sight is perpendicular rather than parallel to the local magnetic field. This is opposite to the trend in the interplanetary space permeated in the solar wind, because the ratio between dynamic pressure and magnetic pressure is an order of magnitude smaller than at 1 AU. On the other hand, we find that iron ions in the comet head build up to a density comparable to that of oxygen ions, but are unlikely to form a visible tail because of the shorter mean free paths of the neutrals.