First Observations of a Foreshock Bubble at Earth: Implications for Magnetospheric Activity and Energetic Particle Acceleration

Earth?s foreshock, which is the quasi-parallel region upstream of the bow shock, is a unique plasma region capable of generating several kinds of large-scale phenomena, each of which can impact the magnetosphere resulting in global effects. Interestingly, such phenomena have also been observed at planetary foreshocks throughout our solar system. Recently, a new type of foreshock phenomena has been predicted: foreshock bubbles, which are large-scale disruptions of both the foreshock and incident solar wind plasmas that can result in global magnetospheric disturbances. Here we present unprecedented, multi-point observations of foreshock bubbles at Earth using a combination of spacecraft and ground observations primarily from the Time History of Events and Macroscale Interactions during Substorms (THEMIS) mission, and we include detailed analysis of the events? global effects on the magnetosphere and the energetic ions and electrons accelerated by them, potentially by a combination of first and second order Fermi and shock drift acceleration processes. This new phenomena should play a role in energetic particle acceleration at collisionless, quasi-parallel shocks throughout the Universe

Characterization of radio active aerosols in Tehran research reactor containment

The objectives of this research were to determine the levels of radioactivity in the Tehran research reactor containment and to investigate the mass-size distribution, composition, and concentration of radio nuclides during operation of the reactor. A cascade impactor sampler was used to determine the size-activity distributions of radioactive aerosols in each of the sampling stations. Levels of α and β activities were determined based on a counting method using a liquid scintillation counter and smear tests. The total average mass fractions of fine particles (particle diameter dp <1 µm) in all of the sampling stations were approximately 26.75 , with the mean and standard deviation of 52.15 ± 19.75 µg/m3. The total average mass fractions of coarse particles were approximately 73.2, with the mean and standard deviation of 71.34 ± 24.57 µg/m3. In addition to natural radionuclides, artificial radionuclides, such as 24Na,91Sr,131I,133I,103Ru,82Br, and 140La, may be released into the reactor containment structure. Maximum activity was associated with accumulation-mode particles with diameters less than 400 nm. The results obtained from liquid scintillation counting suggested that the mean specific activity of alpha particles in fine and coarse-modes were 89.7 and 10.26 , respectively. The mean specific activity of beta particles in fine and coarse-modes were 81.15 and 18.51 , respectively. A large fraction ofthe radionuclides' mass concentration in the Tehran research reactor containment was associated with coarse-mode particles, in addition, a large fraction of the activity in the aerosol particles was associated with accumulation-mode particles. © 2015, Vinca Inst Nuclear Sci. All rights reserved

Dependence of CMI Growth Rates on Electron Velocity Distributions and Perturbation by Solitary Waves

We calculate growth rates and corresponding gains for RX and LO mode radiation associated with the cyclotron maser instability for parameterized horseshoe electron velocity distributions. The velocity distribution function was modeled to closely fit the electron distribution functions observed in the auroral cavity. We systematically varied the model parameters as well as the propagation direction to study the dependence of growth rates on model parameters. The growth rate depends strongly on loss cone opening angle, which must be less than $90^{o}$ for significant CMI growth. The growth rate is sharply peaked for perpendicular radiation ($k_{\parallel} = 0$), with a full-width at half-maximum $1.7^{o}$, in good agreement with observed k-vector orientations and numerical simulations. The fractional bandwidth varied between 10$^{-4}$ and 10$^{-2}$, depending most strongly on propagation direction. This range encompasses nearly all observed fractional AKR burst bandwidths. We find excellent agreement between the computed RX mode emergent intensities and observed AKR intensities assuming convective growth length $L_c\approx$20-40 km and group speed 0.15$c$. The only computed LO mode growth rates compatible observed LO mode radiation levels occurred for number densities more than 100 times the average energetic electron densities measured in auroral cavities. This implies that LO mode radiation is not produced directly by the CMI mechanism but more likely results from mode conversion of RX mode radiation. We find that perturbation of the model velocity distribution by large ion solitary waves (ion holes) can enhance the growth rate by a factor of 2-4. This will result in a gain enhancement more than 40 dB depending on the convective growth length within the structure. Similar enhancements may be caused by EMIC waves.Comment: 21 pages, 11 figures. J. Geophys. Res. 2007 (accepted

Reliability and Performance Analysis of a Fault Tolerant Data Handling Protocol for Aerospace Applications

Data communication inside the satellite is one of the most important factors in satellite design. For this purpose, a variety of protocols have been developed in recent years. Controller Area Network (CAN) is one of the well-developed protocols to be used in the On-Board Data Handling (OBDH) systems for communication and geosynchronous satellites. Nonetheless, for aerospace applications which demand radiation hardened integrated circuits, a full featured stand-alone Rad-Hard CAN controller is unavailable. HDL (Hardware Description Language) based IP(Intellectual Property) Cores which are widely developed to be implemented on Rad-Hard FPGAs are more attractive. This paper proposes a novel fault tolerant CAN controller based on FPGAs to provide on-board data handling requirements of the communication satellites. We outline some practical topologies and discuss their complexities and reliability. Despite the fact that the most famous methods like TMR (Triple Modular Redundancy), are very common among designers, the reliability analyses show that these methods are unable to tolerate single upsets in routing matrixes. This paper proposes a robust data bus controller based on dual duplex redundancy on FPGAs. The fault injection experiments reveal that the proposed approach represents better performance respective to the conventional hardware redundancy. Furthermore, the experiments show that the capability of tolerating SEU effects by the proposed method is increased up to 7.17 times with respect to a regular design. The proposed architecture imposes 16.26% and 5.2% overhead in the required resources and the operating frequency in comparison to the regular TMR method

Traveling foreshocks and transient foreshock phenomena

We use the multispacecraft capabilities of the Cluster and Time History of Events and Macroscale Interactions during Substorms (THEMIS) missions to show that two types of foreshock may be detected in spacecraft data. One is the global foreshock that appears upstream of the Earth's quasi-parallel bow shock under steady or variable interplanetary magnetic field. Another type is a traveling foreshock that is bounded by two rotational discontinuities in the interplanetary magnetic field and propagates along the bow shock. Foreshock compressional boundaries are found at the edges of both types of foreshock. We show that isolated foreshock cavities are a subset of the traveling foreshocks that form when two bounding rotational discontinuities are so close that the ultralow-frequency waves do not develop in the region between them. We also report observations of a spontaneous hot flow anomaly inside a traveling foreshock. This means that other phenomena, such as foreshock cavitons, may also exist inside this type of foreshock. In the second part of this work we present statistical properties of phenomena related to the foreshock, namely, foreshock cavities, cavitons, spontaneous hot flow anomalies, and foreshock compressional boundaries. We show that spontaneous hot flow anomalies are the most depleted transient structures in terms of the B field and plasma density inside them and that the foreshock compressional boundaries and foreshock cavities are closely related structures

Transient Foreshock Structures Upstream of Mars: Implications of the Small Martian Bow Shock

We characterize the nature of magnetic structures in the foreshock region of Mars associated with discontinuities in the solar wind. The structures form at the upstream edge of moving foreshocks caused by slow rotations in the interplanetary magnetic field (IMF). The solar wind plasma density and the IMF strength noticeably decrease inside the structures' core, and a compressional shock layer is present at their sunward side, making them consistent with foreshock bubbles (FBs). Ion populations responsible for these structures include backstreaming ions that only appear within the moving foreshock, and accelerated reflected ions from the quasi-perpendicular bow shock. Both ion populations accumulate near the upstream edge of the moving foreshock which facilitates FB formation. Reflected ions with hybrid trajectories that straddle between the quasi-perpendicular and quasi-parallel bow shocks during slow IMF rotations contribute to formation of foreshock transients.Comment: Submitted to Geophysical Research Letter

Ion Acceleration by Flux Transfer Events in the Terrestrial Magnetosheath

We report ion acceleration by flux transfer events in the terrestrial magnetosheath in a global two-dimensional hybrid-Vlasov polar plane simulation of Earth's solar wind interaction. In the model we find that propagating flux transfer events created in magnetic reconnection at the dayside magnetopause drive fast-mode bow waves in the magnetosheath, which accelerate ions in the shocked solar wind flow. The acceleration at the bow waves is caused by a shock drift-like acceleration process under stationary solar wind and interplanetary magnetic field upstream conditions. Thus, the energization is not externally driven but results from plasma dynamics within the magnetosheath. Energetic proton populations reach the energy of 30 keV, and their velocity distributions resemble time-energy dispersive ion injections observed by the Cluster spacecraft in the magnetosheath.Peer reviewe

Seizure Clusters, Seizure Severity Markers, and SUDEP Risk.

Rationale: Seizure clusters may be related to Sudden Unexpected Death in Epilepsy (SUDEP). Two or more generalized convulsive seizures (GCS) were captured during video electroencephalography in 7/11 (64%) patients with monitored SUDEP in the MORTEMUS study. It follows that seizure clusters may be associated with epilepsy severity and possibly with SUDEP risk. We aimed to determine if electroclinical seizure features worsen from seizure to seizure within a cluster and possible associations between GCS clusters, markers of seizure severity, and SUDEP risk. Methods: Patients were consecutive, prospectively consented participants with drug-resistant epilepsy from a multi-center study. Seizure clusters were defined as two or more GCS in a 24-h period during the recording of prolonged video-electroencephalography in the Epilepsy monitoring unit (EMU). We measured heart rate variability (HRV), pulse oximetry, plethysmography, postictal generalized electroencephalographic suppression (PGES), and electroencephalography (EEG) recovery duration. A linear mixed effects model was used to study the difference between the first and subsequent seizures, with a level of significance set at p < 0.05. Results: We identified 112 GCS clusters in 105 patients with 285 seizures. GCS lasted on average 48.7 ± 19 s (mean 49, range 2-137). PGES emerged in 184 (64.6%) seizures and postconvulsive central apnea (PCCA) was present in 38 (13.3%) seizures. Changes in seizure features from seizure to seizure such as seizure and convulsive phase durations appeared random. In grouped analysis, some seizure features underwent significant deterioration, whereas others improved. Clonic phase and postconvulsive central apnea (PCCA) were significantly shorter in the fourth seizure compared to the first. By contrast, duration of decerebrate posturing and ictal central apnea were longer. Four SUDEP cases in the cluster cohort were reported on follow-up. Conclusion: Seizure clusters show variable changes from seizure to seizure. Although clusters may reflect epilepsy severity, they alone may be unrelated to SUDEP risk. We suggest a stochastic nature to SUDEP occurrence, where seizure clusters may be more likely to contribute to SUDEP if an underlying progressive tendency toward SUDEP has matured toward a critical SUDEP threshold

Granulomatous pyoderma preceding chronic recurrent multifocal osteomyelitis triggered by vaccinations in a two-year-old boy: a case report

<p>Abstract</p> <p>Introduction</p> <p>Chronic recurrent multifocal osteomyelitis is a rare, systemic, aseptic, inflammatory disorder that involves different sites. Pathogenesis of chronic recurrent multifocal osteomyelitis is currently unknown.</p> <p>Case presentation</p> <p>A two-year-old Caucasian boy, diagnosed with chronic recurrent multifocal osteomyelitis with granulomatous pyoderma following routine vaccinations is presented for the first time in the literature.</p> <p>Conclusion</p> <p>We conclude that antigen exposures might have provoked this inflammatory condition for our case. Skin and/or bone lesions following vaccinations should raise suspicion of an inflammatory response such as chronic recurrent multifocal osteomyelitis only after thorough evaluation for chronic infection, autoimmune, immunodeficiency or vasculitic diseases.</p