Modeling the evolution of chorus waves into plasmaspheric hiss

Plasmaspheric hiss (PH) is a band-limited, incoherent whistler mode emission found predominantly in the plasmasphere or high-density plasma regions in the near-Earth space environment. Since its discovery in the late 1960s, PH has been recognized as playing an important role in shaping the structure and dynamics of the Earth's electron radiation belts and creating the slot region that separates the inner and outer belts. However, the origin of PH has been a topic of intense debate for over four decades. Here we present a model for the origin of PH that involves the evolution of chorus waves into the PH spectrum. We perform extensive ray tracing using the HOTRAY code and calculate Landau damping using newly developed suprathermal flux maps from THEMIS observations, that are L and magnetic local time dependent, for both inside and outside the plasmasphere. Our results show remarkable consistency with the observed statistical characteristics of hiss, including the day/night asymmetry in wave power, frequency spectrum, geomagnetic control of PH, quasi-parallel equatorial wave normal angles, and confinement within the plasmasphere. Our model also reproduces ancillary features such as exohiss and extremely low frequency (ELF) hiss and might be related to a previously reported phenomenon called lower hybrid resonance duct trapping in the ionosphere. A detailed analysis of ray morphologies shows a separation into four distinct groups, which correspond to (1) rays that are trapped at the plasmapause, (2) PH rays, (3) ELF hiss rays, and (4) rays that represent the bulk of the chorus ray power

Etiological diagnosis, prognostic significance and role of electrophysiological study in patients with Brugada ECG and syncope.

BACKGROUND: Syncope is considered a risk factor for life-threatening arrhythmias in Brugada patients. Distinguishing a benign syncope from one due to ventricular arrhythmias is often difficult, unless an ECG is recorded during the episode. Aim of the study was to analyze the characteristics of syncopal episodes in a large population of Brugada patients and evaluate the role of electrophysiological study (EPS) and the prognosis in the different subgroups. METHODS AND RESULTS: One hundred ninety-five Brugada patients with history of syncope were considered. Syncope were classified as neurally mediated (group 1, 61%) or unexplained (group 2, 39%) on the basis of personal and family history, clinical features, triggers, situations, associated signs, concomitant therapy. Most patients underwent EPS; they received ICD or implantable loop-recorder on the basis of the result of investigations and physician's judgment. At 62±45months of mean follow-up, group 1 showed a significantly lower incidence of arrhythmic events (2%) as compared to group 2 (9%, p<0.001). Group 2 patients with positive EPS showed the highest risk of arrhythmic events (27%). No ventricular events occurred in subjects with negative EPS. CONCLUSION: Etiological definition of syncope in Brugada patients is important, as it allows identifying two groups with different outcome. Patients with unexplained syncope and ventricular fibrillation induced at EPS have the highest risk of arrhythmic events. Patients presenting with neurally mediated syncope showed a prognosis similar to that of the asymptomatic and the role of EPS in this group is unproven

Transitional Activities in Elite Football: Frequency, Type, Effect on Match Outcome and the Novel Concept of Clusters

The aims of this study were to analyze the effect of contextual variables on physical metrics during transitions and investigate repeated transitional activities during transitions. Data was collected from 10 matches (23 elite soccer players). A total of 4249 individual observations were recorded including 1164 positive transitions (defense-to-attack), 1269 negative transitions (attack-to-defense), 1120 fast attacks, and 696 high pressure activities. Metrics per minute (m·min-1) as well as absolute variables: Total Distance (TD), high-speed running distance (HSRD, >19.8km·h-1), sprint distance (SD, >25.2km·h-1), relative high-speed running distance (VelB4), relative sprint distance (VelB5), acceleration distance (AccB3 Dist., distance with variations in running speed >3m·s-2), the number of high-intensity accelerations (HI Acc, >3m·s-2) and decelerations (HI Dec, >3m·s-2) were quantified. Significant effects of match half were found for TD (p <.001; ES =.03), HSRD (p = .023; ES = .012), VelB4 (p < .001; ES = .04), and HI Dec (p = .037; ES = .010). Match outcome had a relation to TD (m), HSRD (m) (p < .001), SD (m) and VelB4 (m) (p = .011) as well as VelB5 (m), and AccB3 Dist. distance (m) (p = .002 and p = .020, respectively). Performance in lost matches was lower in the 2nd half (p≤0.05). This study indicates that players are exposed to repeated short and intermittent high velocity actions together, highlighting the need to move away from 90min averages and pay more attention to transitional activities in modern training design

Worst Case Scenarios in Soccer Training and Competition: Analysis of Playing Position, Congested Periods, and Substitutes

Aim: To understand mean (WCSₘₑₐₙ) and peak (WCSₚₑₐₖ) worst case scenarios within training and game play in male professional soccer. Methods: Thirty-one (n = 31) first team players were monitored across 37 matches and 14 MD-3 sessions. Playing status was distinguished, football drills analyzed, and performance explored in long-period: >6 days, moderate-period: 5–6 days, and congested-period: ≤4 days. Relative total distance (TD), high-speed running distance (HSRD, >19.8 km·h⁻¹), sprint distance (SD, >25.2 km·h⁻²), accelerations/decelerations (A+D, >3 m·s⁻²), accelerations (Acc, >3 m·s⁻²), and decelerations (Dec, >−3 m·s⁻²) were measured as well as Maximum acceleration (Max Acc; m·s⁻²) and deceleration (Max Dec; m·s⁻²). Results: Analysis of variance found differences between matches and training in WCSmean for TD, HSRD, SD, and Max Dec in all positions (p  .275). Fullbacks displayed differences between match and training in Max Acc (moderate ESs; p  .05). Main effects of playing status were discovered for all metrics except Max Dec (p  .124). Analysis showed differences between long- and congested-period for A+D and Dec (large ESs; p ≤ .05). Conclusions: Findings provide more insights into short peak intensity demands of soccer showing that the maximum high velocity action of acceleration and deceleration is not being replicated in training. Nonstarters lack maximum intensity exposure in matches (WCSₚₑₐₖ) increasing the gap between training and competition even higher during congested fixture periods

On the storm‐time evolution of relativistic electron phase space density in Earth's outer radiation belt

Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/98813/1/jgra50151.pd

Physical match demands across different playing positions during transitional play and high-pressure activities in elite soccer.

This study explored physical match demands across different playing positions during transitional play, to inform the need for position-specific training interventions. Data was collected using 10 Hz GPS units from 10 competitive matches including 23 elite soccer players of the 1st Polish Division (Ekstraklasa) in season 2020–21. A total of 4249 positional observations were made; center backs (n = 884), full backs (n = 972), central defensive midfielders (n = 236), central attacking midfielders (n = 270), central midfielders (n = 578), wingers (n = 778), and attackers (n = 531). Match data reflected distances covered per minute (m·min−1): total distance (TD), high-speed running distance (HSRD, > 19.8 km·h⁻¹), sprint distance (SD, > 25.2 km·h⁻¹), and the frequency of high-intensity accelerations and decelerations (A+D, > 3 m·s⁻²; n·min⁻¹). Total absolute sprint distance (SD, > 25.2 km·h⁻¹) and total relative sprint distance (Rel B5) were also quantified. A univariate analysis of variance revealed position-specific differences. Significant effects of position were found for all analysed metrics during transitional play (large ESs; p < .001). Central attacking midfielders displayed higher TD (m·min⁻¹), fullbacks covered highest SD (m·min⁻¹) and wingers achieved the highest A+D (n ·min⁻¹) (p ≤ 0.05). Centre backs displayed the lowest physical outputs when compared to all other positions, except in A+D (n ·min⁻¹) during defensive transitions (p ≤ 0.05). Attackers displayed the highest physical metrics during high pressure activities (p ≤ 0.05). Coaches should carefully consider positional transitional demands to better inform training design. With specific attention paid to drills that replicate game play

Unraveling the formation region and frequency of chorus spectral gaps

Electromagnetic ion cyclotron (EMIC) waves could cause a simultaneous dropout of radiation belt electrons and ring current protons. However, their effects on the dropout of both plasma populations have not been quantified in previous studies. In this paper, we model the simultaneous dropout of MeV electrons and hundreds of keV protons observed by Van Allen Probes within ∼40 min on 27 February 2014. The wave and particle measurements during the period of most intense EMIC waves at ∼ 5.2 are used to calculate the quasilinear diffusion coefficients and simulate the evolution of both energetic electrons and protons. Our model well captures the dropout of electrons with energies >1 MeV and pitch angles 200 keV and pitch angles >40°. This is the first modeling work quantitatively reproducing the simultaneous dropout of both populations due to EMIC wave scattering.AGS-1847818 - National Science Foundation; 80NSSC19K0845 - NASAAccepted manuscrip

Competing source and loss mechanisms due to wave-particle interactions in Earth’s outer radiation belt during the 30 September to 3 October 2012 geomagnetic storm

Abstract Drastic variations of Earth’s outer radiation belt electrons ultimately result from various competing source, loss, and transport processes, to which wave-particle interactions are critically important. Using 15 spacecraft including NASA’s Van Allen Probes, THEMIS, and SAMPEX missions and NOAA’s GOES and POES constellations, we investigated the evolution of the outer belt during the strong geomagnetic storm of 30 September to 3 October 2012. This storm’s main phase dropout exhibited enhanced losses to the atmosphere at L*\u3c 4, where the phase space density (PSD) of multi-MeV electrons dropped by over an order of magnitude in1 MeV electrons and energetic protons, SAMPEX \u3e1 MeV electrons, and ground observations of band-limited Pc1-2 wave activity, we show that this sudden loss was consistent with pitch angle scattering by electromagnetic ion cyclotron waves in the dusk magnetic local time sector at 3\u3c L*\u3c 4. At 4\u3c L*\u3c 5, local acceleration was also active during the main and early recovery phases, when growing peaks in electron PSD were observed by both Van Allen Probes and THEMIS. This acceleration corresponded to the period when IMF Bz was southward, the AE index was \u3e300 nT, and energetic electron injections and whistler-mode chorus waves were observed throughout the inner magnetosphere for \u3e12 h. After this period, Bz turned northward, and injections, chorus activity, and enhancements in PSD ceased. Overall, the outer belt was depleted by this storm. From the unprecedented level of observations available, we show direct evidence of the competitive nature of different wave-particle interactions controlling relativistic electron fluxes in the outer radiation belt

Resonant excitation of whistler waves by a helical electron beam

Chorus-like whistler-mode waves that are known to play a fundamental role in driving radiation-belt dynamics are excited on the Large Plasma Device by the injection of a helical electron beam into a cold plasma. The mode structure of the excited whistler wave is identified using a phase-correlation technique showing that the waves are excited through a combination of Landau resonance, cyclotron resonance and anomalous cyclotron resonance. The dominant wave mode excited through cyclotron resonance is quasi-parallel propagating, whereas wave modes excited through Landau resonance and anomalous cyclotron resonance propagate at oblique angles that are close to the resonance cone. An analysis of the linear wave growth rates captures the major observations in the experiment. The results have important implications for the generation process of whistler waves in the Earth's inner magnetosphere

Pc1-Pc2 waves and energetic particle precipitation during and after magnetic storms: superposed epoch analysis and case studies

Magnetic pulsations in the Pc1-Pc2 frequency range (0.1-5 Hz) are often observed on the ground and in the Earth's magnetosphere during the aftermath of geomagnetic storms. Numerous studies have suggested that they may play a role in reducing the fluxes of energetic ions in the ring current; more recent studies suggest they may interact parasitically with radiation belt electrons as well. We report here on observations during 2005 from search coil magnetometers and riometers installed at three Antarctic stations, Halley (-61.84 degrees magnetic latitude, MLAT), South Pole (-74.18 degrees MLAT), and McMurdo (-79.96 degrees MLAT), and from energetic ion detectors on the NOAA Polar-orbiting Operational Environment Satellites (POES). A superposed epoch analysis based on 13 magnetic storms between April and September 2005 as well as case studies confirm several earlier studies that show that narrowband Pc1-Pc2 waves are rarely if ever observed on the ground during the main and early recovery phases of magnetic storms. However, intense broadband Pi1-Pi2 ULF noise, accompanied by strong riometer absorption signatures, does occur during these times. As storm recovery progresses, the occurrence of Pc1-Pc2 waves increases, at first in the daytime and especially afternoon sectors but at essentially all local times later in the recovery phase (typically by days 3 or 4). During the early storm recovery phase the propagation of Pc1-Pc2 waves through the ionospheric waveguide to higher latitudes was more severely attenuated. These observations are consistent with suggestions that Pc1-Pc2 waves occurring during the early recovery phase of magnetic storms are generated in association with plasmaspheric plumes in the noon-to-dusk sector, and these observations provide additional evidence that the propagation of waves to ground stations is inhibited during the early phases of such storms. Analysis of 30- to 250-keV proton data from four POES satellites during the 24-27 August and 18-19 July 2005 storm intervals showed that the location of the inner edge of the ring current matched well with the plasmapause model of O'Brien and Moldwin (2003). However, the POES data showed no evidence of the consequences of electromagnetic ion cyclotron waves (localized proton precipitation) during main and early recovery phase. During later stages of the recovery phase, when such precipitation was observed, it was coincident with intense wave events at Halley, and it occurred at L shells near or up to 1 RE outside the modeled plasmapause but well equatorward of the isotropy boundary