Particle Release Time Research Articles

Capsule polymer flooding for enhanced oil recovery

To solve the problems of shear degradation and injection difficulties in conventional polymer flooding, the capsule polymer flooding for enhanced oil recovery (EOR) was proposed. The flow and oil displacement mechanisms of this technique were analyzed using multi-scale flow experiments and simulation technology. It is found that the capsule polymer flooding has the advantages of easy injection, shear resistance, controllable release in reservoir, and low adsorption retention, and it is highly capable of long-distance migration to enable viscosity increase in deep reservoirs. The higher degree of viscosity increase by capsule polymer, the stronger the ability to suppress viscous fingering, resulting in a more uniform polymer front and a larger swept range. The release performance of capsule polymer is mainly sensitive to temperature. Higher temperatures result in faster viscosity increase by capsule polymer solution. The salinity has little impact on the rate of viscosity increase. The capsule polymer flooding is suitable for high-water-cut reservoirs for which conventional polymer flooding techniques are less effective, offshore reservoirs by polymer flooding in largely spaced wells, and medium to low permeability reservoirs where conventional polymers cannot be injected efficiently. Capsule polymer flooding should be customized specifically, with the capsule particle size and release time to be determined depending on target reservoir conditions to achieve the best displacement effect.

Coupling of potential habitat models with particle tracking experiments to examine larval fish dispersal and connectivity in deep water regions.

Computing Lagrangian trajectories with ocean circulation models is a powerful way to infer larval dispersal pathways and connectivity. Defining release areas and timing of particles to represent larval habitat realistically is critical to obtaining representative dispersal pathways. However, it is challenging due to spatial and temporal variability in larval density. Forward-tracking particle experiments were conducted to study larval connectivity of four species (neritic or mesopelagic) in the Gulf of Mexico's (GoM) deep-water region. A seasonal climatology coupled with predicted potential larval habitat models based on generalized additive models was used to delimit the particle dispersal origin. Two contrasting mesoscale circulation patterns were examined: (1) high Loop Current (LC) intrusion, absence of recently detached LC anticyclonic eddies (LC-ACE), and no interaction between LC-ACEs and the semi-permanent cyclonic eddy (CE) in the Bay of Campeche (BoC), and (2) limited LC intrusion, a recently detached LC-ACE, and interaction between LC-ACEs and the BoC's CE. To simulate larval transport, virtual larvae were randomly released in the potential habitats and advected for 30 days with the velocity fields of the HYbrid Coordinate Ocean Model with hourly-resolution assimilation. Potential habitat location and size played a major role in dispersal and connectivity. A greater percentage of particles were retained in potential habitats restricted to the southern BoC, suggesting lower connectivity with other GoM regions than those encompassing most of the BoC or the central Gulf. Mesoscale feature interactions in the western GoM and BoC led to greater dispersion along the western basin. By contrast, the absence of ACE-CE interaction in the BoC led to greater retention and less connectivity between the southern and northern GoM. Under high LC intrusion, particles seeded north of the Yucatan Shelf were advected through the Florida Straits and dispersed within the GoM. Coupling potential habitat models with particle experiments can help characterize the dispersal and connectivity of fish larvae in oceanic systems.

Investigating Particle Paths in Intracranial Aneurysms: A Parametric Study

A large part of computational fluid dynamics (CFD) studies in hemodynamics concentrates on the berry-like bulgings on cerebral vessel walls, called intracranial aneurysms (IA). One technique is the calculation of particle paths, which can help understand important physiological processes like thrombus formation or drug propagation. The problem is that the particle paths can display chaotic nature even in simple flows, thus, investigating the effects of parameters on the particle paths is essential. The method used in this study consists of four steps. The first step is to voxelize the observed domain into a uniform voxel grid, the second step is to simulate the velocity flow field using the lattice-Boltzmann method, then to calculate one million particle paths using a fourth-order Runge-Kutta integrator. Lastly, the final step is the calculation of the relative perimeter, relative area and their ratio (P/A ratio) for each outlet when the particle release plane is colored according to the outlets the particles took. Five patient-specific cases were investigated. After a voxel size and integrator time step dependence study, the effect of the presence of the aneurysm sack and the particle release time within the heart cycle were assessed. Based on five geometries, the presence of the aneurysm sac increases the P/A ratio (which is a direct link to the chaotic nature of the particle paths), and when the particles are released near the peak and the decelerating phase of the heart cycle, the P/A ratio also significantly increases.

Dynamic Analysis of Aerosol Release from a Pressurized Metered Dose Inhaler Combined with a Valved Holding Chamber Using Simplified Laser Photometry.

Background: A pressurized metered dose inhaler combined with a valved holding chamber (pMDI+VHC) is used to prevent upper airway complications and improve the efficiency of inhaled drug delivery; however, the aerodynamic behavior of the released particles has not been well investigated. This study aimed at clarifying the particle release profiles of a VHC using simplified laser photometry. Methods: An inhalation simulator comprised a computer-controlled pump and a valve system that withdrew aerosol from a pMDI+VHC using a jump-up flow profile. A red laser illuminated the particles leaving VHC and evaluated the intensity of the light reflected by the released particles. Results: The data suggested that the output (OPT) from the laser reflection system represented particle concentration rather than particle mass, and the latter was calculated as OPT × instantaneous withdrawn flow (WF). Summation of OPT hyperbolically decreased with flow increment, whereas summation of OPT × instantaneous flow was not influenced by WF strength. Particle release trajectories consisted of three phases, namely increment with a parabolic curve, flat, and decrement with exponential decay phases. The flat phase appeared exclusively at low-flow withdrawal. These particle release profiles suggest the importance of early phase inhalation. The hyperbolic relationship between WF and particle release time revealed the minimal required withdrawal time at an individual withdrawal strength. Conclusions: The particle release mass was calculated as laser photometric output × instantaneous flow. Simulation of the released particles suggested the importance of early phase inhalation and predicted the minimally required withdrawal time from a pMDI+VHC.

Achieving Targeted Delivery of Chemotherapeutic Particles to Small Airway Tumors via Pulmonary Route Using Endotracheal Catheters: A CFPD Study.

Tracheobronchial tumors, while uncommon, are often malignant in adults. Surgical removal is the primary therapy for non-metastatic lung malignancies, but it is only possible in a small percentage of non-small-cell lung cancer patients and is limited by the number and location of tumors, as well as the patient's overall health. This study proposes an alternative treatment: administering aerosolized chemotherapeutic particles via the pulmonary route using endotracheal catheters to target lung tumors. To improve delivery efficiency to the lesion, it is essential to understand local drug deposition and particle transport dynamics. This study uses an experimentally validated computational fluid particle dynamics (CFPD) model to simulate the transport and deposition of inhaled chemotherapeutic particles in a 3-dimensional tracheobronchial tree with 10 generations (G). Based on the particle release maps, targeted drug delivery strategies are proposed to enhance particle deposition at two lung tumor sites in G10. Results indicate that controlled drug release can improve particle delivery efficiencies at both targeted regions. The use of endotracheal catheters significantly affects particle delivery efficiencies in targeted tumors. The parametric analysis shows that using smaller catheters can deliver more than 74% of particles to targeted tumor sites, depending on the location of the tumor and the catheter diameter used, compared to less than 1% using conventional particle administration methods. Furthermore, the results indicate that particle release time has a significant impact on particle deposition under the same inhalation profile. This study serves as a first step in understanding the impact of catheter diameter on localized endotracheal injection for targeting tumors in small lung airways.

Connectivity networks and delineation of disconnected coastal provinces along the Indian coastline using large‐scale Lagrangian transport simulations

AbstractOcean circulation is the engine of dispersal and population connectivity in marine ecosystems, knowledge of which is essential for conservation planning. Understanding connectivity patterns at a large scale can help define the spatial extent of metapopulations. In this study, we built connectivity networks from Lagrangian transport simulations of neutrally buoyant particles released along the Indian coastline, a significant region in the Indian Ocean. We assessed the variation in connectivity networks across release periods for the major drivers of oceanography including the two monsoonal seasons, El Niño–Southern Oscillation (ENSO) years and for the entire range of region‐specific pelagic larval durations (PLDs) for marine invertebrates. We detected well‐connected communities, mapped frequent connectivity breaks, and assessed the functional role of coastal areas within the connectivity network using node metrics. Network characteristics did not differ based on the ENSO year, but varied with season and PLD. Connectance for the Indian coastline was relatively low, ranging from 0.5% to 3.4%, and increased significantly for PLD larger than 20 d. The number of cohesive coastal communities decreased gradually from 60 (PLD < 4 d) to 30 (PLD > 20 d) with increasing PLD. Despite variation in the location of connectivity breaks with the time of particle release within a monsoonal season, four disconnected provinces were consistently identified across the entire PLD range, which partially overlapped with observed genetic and biogeographic breaks reported along the Indian coastline. Our results support the adoption of a coordinated management framework within each of the four provinces delineated in the present study.

The first widespread solar energetic particle event observed by Solar Orbiter on 2020 November 29

Context.On 2020 November 29, the first widespread solar energetic particle (SEP) event of solar cycle 25 was observed at four widely separated locations in the inner (≲1 AU) heliosphere. Relativistic electrons as well as protons with energies > 50 MeV were observed by Solar Orbiter (SolO), Parker Solar Probe, the Solar Terrestrial Relations Observatory (STEREO)-A and multiple near-Earth spacecraft. The SEP event was associated with an M4.4 class X-ray flare and accompanied by a coronal mass ejection and an extreme ultraviolet (EUV) wave as well as a type II radio burst and multiple type III radio bursts.Aims.We present multi-spacecraft particle observations and place them in context with source observations from remote sensing instruments and discuss how such observations may further our understanding of particle acceleration and transport in this widespread event.Methods.Velocity dispersion analysis (VDA) and time shift analysis (TSA) were used to infer the particle release times at the Sun. Solar wind plasma and magnetic field measurements were examined to identify structures that influence the properties of the energetic particles such as their intensity. Pitch angle distributions and first-order anisotropies were analyzed in order to characterize the particle propagation in the interplanetary medium.Results.We find that during the 2020 November 29 SEP event, particles spread over more than 230° in longitude close to 1 AU. The particle onset delays observed at the different spacecraft are larger as the flare–footpoint angle increases and are consistent with those from previous STEREO observations. Comparing the timing when the EUV wave intersects the estimated magnetic footpoints of each spacecraft with particle release times from TSA and VDA, we conclude that a simple scenario where the particle release is only determined by the EUV wave propagation is unlikely for this event. Observations of anisotropic particle distributions at SolO, Wind, and STEREO-A do not rule out that particles are injected over a wide longitudinal range close to the Sun. However, the low values of the first-order anisotropy observed by near-Earth spacecraft suggest that diffusive propagation processes are likely involved.

Correcting Photo Reflection Method Output and Its Application in the Dynamic Analysis of Particle Release from Dry Powder Inhalers.

Background: The photo reflection method (PRM) is used to measure light reflected from particles released from dry powder inhalers (DPIs). This simple method depicts time trajectories of released drugs; however, it underestimates the number of particles at high peak inhalation flow rates (PIFs). In this study, we aimed to correct this underestimation and clarify whether long inhalation is necessary for capsule-type DPIs, using this unique method. Methods: To establish quantitative measurements using the PRM, several types of DPIs were inhaled with square-wave inhalations at different PIFs using an inhalation simulator, and the total emitted dose (TED) and the release time of the TED (TTED) were measured. Next, capsule-type DPIs were inhaled using inhalation patterns of patients with chronic obstructive pulmonary disease (COPD), and particle release time trajectories were recorded. Results: For all DPIs, except for Turbuhaler® (TBH), both TED and TTED were hyperbolically decreased with an increase in the PIF of square-wave inhalations. TED correction using the TTED showed flat TED changes at high PIF ranges. The patient inhalation analysis showed that the corrected TEDs of seven COPD inhalation patterns were not significantly different. The PRM further revealed that the inhaled flow rate and release time of all seven patterns were sufficient to release particles in the capsule. Conclusions: The inhaled flow rate and TTED that exceeded specific conditions enabled complete particle release from the DPIs except for TBH. Therefore, an extremely long inhalation is not required for capsule-type DPIs. Our corrected time trajectory analysis using the PRM provides a new strategy for the particle release analysis of DPIs.

Deposition of bolus and continuously inhaled aerosols in rhythmically moving terminal alveoli

The particle dynamics in an oscillating alveolus under tidal breathing can be dramatically different from those in a static alveolus. Despite its close relevance to pulmonary drug delivery and health risk from airborne exposure, quantifications of alveolar deposition are scarce due to its inaccessibility to in vivo measurement instruments, tiny size to replicate in vitro, and dynamic wall motions to model. The objective of this study is to introduce a numerical method to quantify alveolar deposition with continuous particle release in a rhythmically oscillating alveolus by integrating the deposition curves for bolus aerosols and use this method to develop correlations applicable in assessing alveolar drug delivery efficiency or dosimetry of inhaled toxicants. An idealized blind-end terminal alveolus model was developed with rhythmically moving alveolar boundary conditions in phase with tidal breathing. The dynamic wall expansion mode and magnitude were based on experimentally measured chest wall motions and tidal volumes. A well-validated Lagrangian tracking model was used to simulate the transport and deposition of inhaled micrometer particles. Large differences were observed between dynamic and static alveoli in particle motion, deposition onset, and final alveolar deposition fraction. Alveolar deposition of bolus aerosols is highly sensitive to breath-holding duration, particle release time, and alveolar dimension. For 1 µm particles, there exists a cut-off release time (zero bolus deposition), which decreases with alveolar size (i.e., 1.0 s in a 0.2-mm-diameter alveolus and 0.56 s in a 0.8-mm-diameter alveolus). The cumulative alveolar deposition was predicted to be 39% for a 0.2-mm-diameter alveolus, 22% for a 0.4-mm-diameter alveolus, and 10% for a 0.8-mm-diameter alveolus. A cumulative alveolar deposition correlation was developed for inhalation delivery with a prescribed period of drug release and the second correlation for the time variation of alveolar deposition of ambient aerosols, both of which captured the relative dependence of the particle release time and alveolar dimension.

Capacity Limits of Diffusion-Based Molecular Timing Channels With Finite Particle Lifetime

This paper introduces capacity limits for molecular timing (MT) channels, where information is modulated in the release timing of small information particles with finite lifetime, and decoded from the time of arrivals at the receiver. It is shown that the random time of arrival can be represented as an additive noise channel, and for the diffusion-based MT (DBMT) channel this noise is distributed according to the Levy distribution. Lower and upper bounds on the capacity of the DBMT channel are derived for the case where the delay associated with the propagation of the information particles in the channel is finite, namely, when the information particles dissipate after a finite time interval. For the case where a single particle is released per channel use, these bounds are shown to be tight. When the transmitter simultaneously releases a large number of particles, the detector at the receiver may not be able to precisely detect the arrival time of all the particles. Therefore, two alternative models are considered: 1) detection based on the particle that arrives first or 2) detection based on the average arrival times. Lower and upper bounds on the capacities of these two models are derived, and the lower bound also provides a lower bound for the capacity of the DBMT channel. It is shown that by controlling the lifetime of the information particles, the capacity can increase polylogarithmically with the number of released particles. As each particle takes a random independent path, this diversity of paths is analogous to receiver diversity and can be used to considerably increase the achievable data rates.

Targeted Drug Delivery to Upper Airways Using a Pulsed Aerosol Bolus and Inhaled Volume Tracking Method.

The pulmonary route presents an attractive delivery pathway for topical treatment of lung diseases. While significant progress has been achieved in understanding the physical underpinnings of aerosol deposition in the lungs, our ability to target or confine the deposition of inhalation aerosols to specific lung regions remains meagre. Here, we present a novel inhalation proof-of-concept in silico for regional targeting in the upper airways, quantitatively supported by computational fluid dynamics (CFD) simulations of inhaled micron-sized particles (i.e. 1-10 μm) using an intubated, anatomically-realistic, multi-generation airway tree model. Our targeting strategy relies on selecting the particle release time, whereby a short-pulsed bolus of aerosols is injected into the airways and the inhaled volume of clean air behind the bolus is tracked to reach a desired inhalation depth (i.e. airway generations). A breath hold maneuver then follows to facilitate deposition, via sedimentation, before exhalation resumes and remaining airborne particles are expelled. Our numerical findings showcase how particles in the range 5-10 μm combined with such inhalation methodology are best suited to deposit in the upper airways, with deposition fractions between 0.68 and unity. In contrast, smaller (< 2 μm) particles are less than optimal due to their slow sedimentation rates. We illustrate further how modulating the volume inhaled behind the pulsed bolus, prior to breath hold, may be leveraged to vary the targeted airway sites. We discuss the feasibility of the proposed inhalation framework and how it may help pave the way for specialized topical lung treatments.

Comparison of the coronal mass ejection shock acceleration of three widespread SEP events during solar cycle 24

AbstractWe studied three solar energetic particle (SEP) events observed on 14 August 2010, 3 November 2011, and 5 March 2013 by Solar Terrestrial Relations Observatory (STEREO) A, B, and near‐Earth (L1) spacecraft with a longitudinal distribution of particles &gt;90°. Using a forward modeling method combined with extreme ultraviolet and white‐light images, we determined the angular extent of the shock, the time and location (cobpoint) of the shock intersection with the magnetic field line connecting to each spacecraft, and compute the shock speed at the cobpoint of each spacecraft. We then examine whether the observations of SEPs at each spacecraft were accelerated and injected by the spatially extended shocks or whether another mechanism such as cross‐field transport is required for an alternative explanation. Our analyses results indicate that the SEPs observed at the three spacecraft on 3 November, STEREO B (STB) and L1 on 14 August, and the 5 March SEP event at STEREO A (STA) can be explained by the direct shock acceleration. This is consistent with the observed significant anisotropies, short time delays between particle release times and magnetic connection times, and sharp rises in the SEP time profiles. Cross‐field diffusion is the likely cause for the 14 August SEP event observed by STA and the 5 March SEPs observed by STB and L1 spacecraft, as particle observations featured weak electron aniotropies and slow rising intensity profiles. Otherwise, the wide longitudinal spread of these SEP increases would require an existence of a circumsolar shock, which may not be a correct assumption in the corona and heliosphere.

Observations of a Coronal Shock Wave and the Production of Solar Energetic Particles

Abstract We present a study that clarifies the acceleration source/mechanism of the solar energetic particle (SEP) event on 2011 August 9. Based on the assumption of scatter-free propagation of charged particles along the interplanetary magnetic field, the solar particle release times of the electrons and protons are derived and both found to be in the decay phase of the flare emission. Furthermore, we compare the peak-flux spectra of the in situ particles and the remote-sensing hard X-ray photons and find a weak correlation between them. In particular, we note that an extreme ultraviolet shock wave, presumed to be a signature of coronal mass ejection (CME) shock front on the solar surface, and an associated type II radio burst were observed alongside this event. Under the framework of diffusive shock acceleration, the derived shock compression ratio can accelerate particles with a theoretical spectral index , which is comparable to the observational index of ∼2.0. Our results appear to support the notion that the coronal shock wave was most likely responsible for the SEP event. Specifically, we find that the electrons were released in a low coronal site at ∼0.58 solar radii, and protons were released when the CME-driven shock propagated to ∼1.38 solar radii. The multi-spacecraft observations, in addition, reveal the connection between the acceleration of shock waves and the release of SEPs.

Coastal amplification of supply and transport (CAST): a new hypothesis about the persistence of Calanus finmarchicus in the Gulf of Maine

AbstractThe lipid-rich calanoid copepod, Calanus finmarchicus, plays a critical role in the pelagic food web of the western North Atlantic and particularly in the Gulf of Maine ecosystem. Deep basins along the continental shelf harbour high abundance of diapausing C. finmarchicus during the summer and fall. In Wilkinson Basin in the western Gulf of Maine, C. finmarchicus has persisted in large concentrations despite recent significant warming that could potentially threaten the existence of the population in this region. Identifying the major source of diapausing individuals is critical to the understanding of mechanisms that allow population persistence. In this study, Lagrangian tracking experiments using an individual-based copepod life cycle model and simulation of environmental conditions during an exceptionally warm year (2012) suggest that coastal waters are the major upstream source for individuals entering dormancy in Wilkinson Basin over summertime, although pathways and distribution patterns vary with the release timing of particles. Both model results and observation data support the Coastal Amplification of Supply and Transport (CAST) hypothesis as an explanation for the persistence of C. finmarchicus population in the western Gulf of Maine. The mechanism involves the coastal amplification of supply (spring reproduction/summer growth in the food-rich coastal region) and transport to the receiving Wilkinson Basin that is capable of harbouring the diapausing stock.

Energy dependence of SEP electron and proton onset times

AbstractWe study the large solar energetic particle (SEP) events that were detected by GOES in the &gt;10 MeV energy channel during December 2006 to March 2014. We derive and compare solar particle release (SPR) times for the 0.25–10.4 MeV electrons and 10–100 MeV protons for the 28 SEP events. In the study, the electron SPR times are derived with the time‐shifting analysis (TSA) and the proton SPR times are derived using both the TSA and the velocity dispersion analysis (VDA). Electron anisotropies are computed to evaluate the amount of scattering for the events under study. Our main results include (1) near‐relativistic electrons and high‐energy protons are released at the same time within 8 min for most (16 of 23) SEP events. (2)There exists a good correlation between electron and proton acceleration, peak intensity, and intensity time profiles. (3) The TSA SPR times for 90.5 MeV and 57.4 MeV protons have maximum errors of 6 min and 10 min compared to the proton VDA release times, respectively, while the maximum error for 15.4 MeV protons can reach to 32 min. (4) For 7 low‐intensity events of the 23, large delays occurred for 6.5 MeV electrons and 90.5 MeV protons relative to 0.5 MeV electrons. Whether these delays are due to times needed for the evolving shock to be strengthened or due to particle transport effects remains unsolved.

Proton activity of the Sun in current solar cycle 24**Supported by the National Natural Science Foundation of China.

We present a study of seven large solar proton events in the current solar cycle 24 (from 2009 January up to the current date). They were recorded by the GOES spacecraft with the highest proton fluxes being over 200 pfu for energies >10 MeV. In situ particle measurements show that: (1) The profiles of the proton fluxes are highly dependent on the locations of their solar sources, namely flares or coronal mass ejections (CMEs), which confirms the “heliolongitude rules” associated with solar energetic particle fluxes; (2) The solar particle release (SPR) times fall in the decay phase of the flare emission, and are in accordance with the times when the CMEs travel to an average height of 7.9 solar radii; and (3) The time differences between the SPR and the flare peak are also dependent on the locations of the solar active regions. The results tend to support the scenario of proton acceleration by the CME-driven shock, even though there exists a possibility of particle acceleration at the flare site, with subsequent perpendicular diffusion of accelerated particles in the interplanetary magnetic field. We derive the integral time-of-maximum spectra of solar protons in two forms: a single power-law distribution and a power law roll-over with an exponential tail. It is found that the unique ground level enhancement that occurred in the event on 2012 May 17 displays the hardest spectrum and the largest roll-over energy which may explain why this event could extend to relativistic energies.

INTERACTION BETWEEN TWO CORONAL MASS EJECTIONS IN THE 2013 MAY 22 LARGE SOLAR ENERGETIC PARTICLE EVENT

We investigate the eruption and interaction of two coronal mass ejections (CMEs) during the large 2013 May 22 solar energetic particle event using multiple spacecraft observations. Two CMEs, having similar propagation directions, were found to erupt from two nearby active regions (ARs), AR11748 and AR11745, at ~08:48 UT and ~13:25 UT, respectively. The second CME was faster than the first CME. Using the graduated cylindrical shell model, we reconstructed the propagation of these two CMEs and found that the leading edge of the second CME caught up with the trailing edge of the first CME at a height of ~6 solar radii. After about two hours, the leading edges of the two CMEs merged at a height of ~20 solar radii. Type II solar radio bursts showed strong enhancement during this two hour period. Using the velocity dispersion method, we obtained the solar particle release (SPR) time and the path length for energetic electrons. Further assuming that energetic protons propagated along the same interplanetary magnetic field, we also obtained the SPR time for energetic protons, which were close to that of electrons. These release times agreed with the time when the second CME caught up with the trailing edge of the first CME, indicating that the CME-CME interaction (and shock-CME interaction) plays an important role in the process of particle acceleration in this event.

GROUND LEVEL ENHANCEMENT IN THE 2014 JANUARY 6 SOLAR ENERGETIC PARTICLE EVENT

We present a study of the 2014 January 6 solar energetic particle (SEP) event, which produced a small ground level enhancement (GLE), making it the second GLE of this unusual solar cycle 24. This event was primarily observed by the South Pole neutron monitors (increase of ~2.5%) whereas a few other neutron monitors recorded smaller increases. The associated coronal mass ejection (CME) originated behind the western limb and had the speed of 1960 km/s. The height of the CME at the start of the associated metric type II radio burst, which indicates the formation of a strong shock, was measured to be 1.61 Rs using a direct image from STEREO-A/EUVI. The CME height at the time of GLE particle release (determined using the South Pole neutron monitor data) was directly measured as 2.96 Rs, from the STEREO-A/COR1 white-light observations. These CME heights are consistent with those obtained for the GLE71, the only other GLE of the current cycle as well as cycle-23 GLEs derived using back-extrapolation. GLE72 is of special interest because it is one of the only two GLEs of cycle 24, one of the two behind-the-limb GLEs and one of the two smallest GLEs of cycles 23 and 24.

An Updated View of Solar Eruptive Flares and the Development of Shocks and CMEs: History of the 2006 December 13 GLE-Productive Extreme Event

Abstract An extreme 2006 December 13 event marked the onset of the Hinode era, being the last major flare in the solar cycle 23 observed with NoRH and NoRP. The event produced a fast CME, strong shock, and a big particle event responsible for GLE70. We endeavor to clarify the relations between the eruptions, shock wave, and flare, and to shed light on a debate over the origin of energetic protons. One concept relates it to flare processes. Another one associates the acceleration of ions with a bow shock driven by a CME at (2-4)R⊙. The latter scenario is favored by a delayed particle release time after the flare. However, our previous studies have established that a shock wave is typically excited by an impulsively erupting magnetic rope (future CME core) during the flare rise, while the outer CME surface evolves from an arcade whose expansion is driven from inside. Observations of the 2006 December 13 event reveal two shocks following each other, whose excitation scenario contradicts the delayed CME-driven bowshock hypothesis. Actually, the shocks developed much earlier, and could accelerate protons still before the flare peak. Then, the two shocks merged into a single stronger one, and only decelerated and dampened long afterwards.

Coronal magnetic topology and the production of solar impulsive energetic electrons

We investigate two candidate solar sources or active regions (ARs) in association with a solar impulsive energetic electron (SIEE) event on 2002 October 20. The solar particle release (SPR) times of SIEEs are derived by using their velocity dispersion with consideration of the instrumental effect. It is found that there are double electron injections at the Sun. The low-energy (<13 keV) electron injection coincides with a C6.6 flare in AR10154 and is accompanied with prominent type III radio bursts rather than a stronger M1.8 flare in AR10160. The M1.8 flare produces, however, faint type III radio bursts. Whereas electrons of 25 to 300 keV are released 9 min later when a jet-like CME travels to 2.6 solar radii. We further examine the coronal magnetic configurations above the two ARs based on the potential field source surface (PFSS) model. It is found that open field lines, rooted in AR10154 and well connected to the Earth, provide escaping channels for energetic electrons. Only a small portion of magnetic fields are opened above AR10160, being responsible for the faint type III radio bursts. These lines are, however, not well connected, making it impossible for SIEEs detection by near-Earth spacecraft. The results appear to establish a physical link between coronal magnetic topology, formation of type III radio bursts, and production of SIEEs.