Conjugate observations of dayside and nightside VLF chorus and QP emissions between Arase (ERG) and Kannuslehto, Finland

Abstract We compare for the first time two conjugate events showing simultaneous very low frequency (VLF) wave observations between the same ground station and spacecraft, at different geomagnetic conditions and on opposite sides of the magnetosphere. Waves were observed at Kannuslehto (MLAT = 64.4°N, L=5.46), Finland, and on board Arase (Exploration of energization and Radiation in Geospace, ERG) in the inner magnetosphere. Case 1 on 28 March 2017 shows quasiperiodic (QP) emissions and chorus simultaneously observed on the postmidnight side during the recovery phase of a storm, with sustained high solar wind speed and AE index. Case 2 on 30 November 2017 shows clear one‐to‐one correspondence of QP elements on the noonside during geomagnetic quiet time (Dst>10 nT and AE<100 nT). We present the characteristics of both cases, focusing on coherence and spatial extent of the waves, electron density, and magnetic field variations. We report that the magnetic field gradient plays a role in the changes of spectral features of the waves

Investigation of small‐scale electron density irregularities observed by the Arase and Van Allen Probes satellites inside and outside the plasmasphere

Abstract In situ electron density profiles obtained from Arase in the night magnetic local time (MLT) sector and from RBSP‐B covering all MLTs are used to study the small‐scale density irregularities present in the plasmasphere and near the plasmapause. Electron density perturbations with amplitudes >10% from background density and with time‐scales less than 30‐min are investigated here as the small‐scale density irregularities. The statistical survey of the density irregularities is carried out using nearly 2 years of density data obtained from RBSP‐B and 4 months of data from Arase satellites. The results show that density irregularities are present globally at all MLT sectors and L‐shells both inside and outside the plasmapause, with a higher occurrence at L > 4. The occurrence of density irregularities is found to be higher during disturbed geomagnetic and interplanetary conditions. The case studies presented here revealed: (1) The plasmaspheric density irregularities observed during both quiet and disturbed conditions are found to coexist with the hot plasma sheet population. (2) During quiet periods, the plasma waves in the whistler‐mode frequency range are found to be modulated by the small‐scale density irregularities, with density depletions coinciding well with the decrease in whistler intensity. Our observations suggest that different source mechanisms are responsible for the generation of density structures at different MLTs and geomagnetic conditions

Plasma and field observations in the magnetospheric source region of a stable auroral red (SAR) arc by the Arase satellite on 28 March 2017

Abstract A stable auroral red (SAR) arc is an aurora with a dominant 630 nm emission at subauroral latitudes. SAR arcs have been considered to occur due to the spatial overlap between the plasmasphere and the ring‐current ions. In the overlap region, plasmaspheric electrons are heated by ring‐current ions or plasma waves, and their energy is then transferred down to the ionosphere where it causes oxygen red emission. However, there have been no study conducted so far that quantitatively examined plasma and electromagnetic fields in the magnetosphere associated with SAR arc. In this paper, we report the first quantitative evaluation of conjugate measurements of a SAR arc observed at 2204 UT on 28 March 2017 and investigate its source region using an all‐sky imager at Nyrölä (magnetic latitude: 59.4°N), Finland, and the Arase satellite. The Arase observation shows that the SAR arc appeared in the overlap region between a plasmaspheric plume and the ring‐current ions and that electromagnetic ion cyclotron waves and kinetic Alfven waves were not observed above the SAR arc. The SAR arc was located at the ionospheric trough minimum identified from a total electron content map obtained by the GNSS receiver network. The Swarm satellite flying in the ionosphere also passed the SAR arc at ~2320 UT and observed a decrease in electron density and an increase in electron temperature during the SAR‐arc crossing. These observations suggest that the heating of plasmaspheric electrons via Coulomb collision with ring‐current ions is the most plausible mechanism for the SAR‐arc generation

Visualization of rapid electron precipitation via chorus element wave-particle interactions

Abstract Chorus waves, among the most intense electromagnetic emissions in the Earth’s magnetosphere, magnetized planets, and laboratory plasmas, play an important role in the acceleration and loss of energetic electrons in the plasma universe through resonant interactions with electrons. However, the spatial evolution of the electron resonant interactions with electromagnetic waves remains poorly understood owing to imaging difficulties. Here we provide a compelling visualization of chorus element wave–particle interactions in the Earth’s magnetosphere. Through in-situ measurements of chorus waveforms with the Arase satellite and transient auroral flashes from electron precipitation events as detected by 100-Hz video sampling from the ground, Earth’s aurora becomes a display for the resonant interactions. Our observations capture an asymmetric spatial development, correlated strongly with the amplitude variation of discrete chorus elements. This finding is not theoretically predicted but helps in understanding the rapid scattering processes of energetic electrons near the Earth and other magnetized planets

An International Retrospective Observational Study of Liver Functional Deterioration after Repeat Liver Resection for Patients with Hepatocellular Carcinoma

Whether albumin and bilirubin levels, platelet counts, ALBI, and ALPlat scores could be useful for the assessment of permanent liver functional deterioration after repeat liver resection was examined, and the deterioration after laparoscopic procedure was evaluated. For 657 patients with liver resection of segment or less in whom results of plasma albumin and bilirubin levels and platelet counts before and 3 months after surgery could be retrieved, liver functional indicators were compared before and after surgery. There were 268 patients who underwent open repeat after previous open liver resection, and 224 patients who underwent laparoscopic repeat after laparoscopic liver resection. The background factors, liver functional indicators before and after surgery and their changes were compared between both groups. Plasma levels of albumin (p = 0.006) and total bilirubin (p = 0.01) were decreased, and ALBI score (p = 0.001) indicated worse liver function after surgery. Laparoscopic group had poorer preoperative performance status and liver function. Changes of liver functional values before and after surgery and overall survivals were similar between laparoscopic and open groups. Plasma levels of albumin and bilirubin and ALBI score could be the indicators for permanent liver functional deterioration after liver resection. Laparoscopic group with poorer conditions showed the similar deterioration of liver function and overall survivals to open group

Multicenter Propensity Score-Based Study of Laparoscopic Repeat Liver Resection for Hepatocellular Carcinoma: A Subgroup Analysis of Cases with Tumors Far from Major Vessels.

Less morbidity is considered among the advantages of laparoscopic liver resection (LLR) for HCC patients. However, our previous international, multi-institutional, propensity score-based study of emerging laparoscopic repeat liver resection (LRLR) failed to prove this advantage. We hypothesize that these results may be since the study included complex LRLR cases performed during the procedure's developing stage. To examine it, subgroup analysis based on propensity score were performed, defining the proximity of the tumors to major vessels as the indicator of complex cases. Among 1582 LRLR cases from 42 international high-volume liver surgery centers, 620 cases without the proximity to major vessels (more than 1 cm far from both first-second branches of Glissonian pedicles and major hepatic veins) were selected for this subgroup analysis. A propensity score matching (PSM) analysis was performed based on their patient characteristics, preoperative liver function, tumor characteristics and surgical procedures. One hundred and fifteen of each patient groups of LRLR and open repeat liver resection (ORLR) were earned, and the outcomes were compared. Backgrounds were well-balanced between LRLR and ORLR groups after matching. With comparable operation time and long-term outcome, less blood loss (283.3±823.0 vs. 603.5±664.9 mL, p = 0.001) and less morbidity (8.7 vs. 18.3 %, p = 0.034) were shown in LRLR group than ORLR. Even in its worldwide developing stage, LRLR for HCC patients could be beneficial in blood loss and morbidity for the patients with less complexity in surgery

An International Retrospective Observational Study of Liver Functional Deterioration after Repeat Liver Resection for Patients with Hepatocellular Carcinoma

Simple Summary For 657 cases of segment or less repeat liver resection with results of plasma albumin and bilirubin levels and platelet counts before and 3 months after surgery, the indicators were compared before and after surgery. There were 268 open repeat after open and 224 cases laparoscopic repeat after laparoscopic liver resection. The background factors and liver functional indicators before and after surgery, and the changes were compared between both groups. Plasma levels of albumin (p = 0.006) and total bilirubin (p = 0.01) were decreased, and ALBI score (p = 0.001) indicated worse liver function after surgery. Though laparoscopic group had poorer performance status and liver function, changes of the values and overall survivals were similar between both groups. Plasma levels of albumin and bilirubin and ALBI score could be the liver functional indicators for liver functional deterioration after liver resection. The laparoscopic group with poorer conditions showed a similar deterioration of liver function and overall survival to the open group. Whether albumin and bilirubin levels, platelet counts, ALBI, and ALPlat scores could be useful for the assessment of permanent liver functional deterioration after repeat liver resection was examined, and the deterioration after laparoscopic procedure was evaluated. For 657 patients with liver resection of segment or less in whom results of plasma albumin and bilirubin levels and platelet counts before and 3 months after surgery could be retrieved, liver functional indicators were compared before and after surgery. There were 268 patients who underwent open repeat after previous open liver resection, and 224 patients who underwent laparoscopic repeat after laparoscopic liver resection. The background factors, liver functional indicators before and after surgery and their changes were compared between both groups. Plasma levels of albumin (p = 0.006) and total bilirubin (p = 0.01) were decreased, and ALBI score (p = 0.001) indicated worse liver function after surgery. Laparoscopic group had poorer preoperative performance status and liver function. Changes of liver functional values before and after surgery and overall survivals were similar between laparoscopic and open groups. Plasma levels of albumin and bilirubin and ALBI score could be the indicators for permanent liver functional deterioration after liver resection. Laparoscopic group with poorer conditions showed the similar deterioration of liver function and overall survivals to open group.N