Coronal Mass Ejections and the Rise Profiles of 0.3 MeV Electron Events

1994 ◽  
Vol 144 ◽  
pp. 479-482 ◽  
Author(s):  
S. W. Kahler ◽  
V. G. Stolpovskii ◽  
E. I. Daibog
Keyword(s):  
Short Duration ◽  
Coronal Mass Ejections ◽  
Interplanetary Space ◽  
Shock Acceleration ◽  
Relativistic Electrons ◽  
X Ray ◽  
Long Duration

AbstractThere is some evidence to suggest that relativistic electrons observed in interplanetary space may be produced in coronal shocks. If so, the rise phases of such events may be longer than those not arising in shocks. To test this possibility, we examined the rise profiles ofE< 0.3MeVelectron events observed on the Helios spacecraft. First we compared rise times of electron events associated with short-duration X-ray flares to events with long-duration X-ray flares. The latter events are more likely than the former to be associated with coronal shocks and coronal mass ejections (CMEs). For a smaller group of electron events we determined the rise times as a function of the speed of the CME observed with the NRL Solwind coronagraph to see whether higher shock speeds resulted in longer event rise times. The data show a weak indication that event rise times increase with CME presence and with CME speed, thus suggesting a role for shock acceleration.

scholarly journals Radio observations of the merging galaxy cluster Abell 520

2019 ◽  
Vol 622 ◽  
pp. A20 ◽  
Author(s):  
D. N. Hoang ◽  
T. W. Shimwell ◽  
R. J. van Weeren ◽  
G. Brunetti ◽  
H. J. A. Röttgering ◽  
...  
Keyword(s):  
Mach Number ◽  
Radio Emission ◽  
Low Frequency ◽  
Galaxy Cluster ◽  
Shock Acceleration ◽  
Relativistic Electrons ◽  
Diffusive Shock Acceleration ◽  
Cluster Emission ◽  
X Ray ◽  
Extended Radio

Context. Extended synchrotron radio sources are often observed in merging galaxy clusters. Studies of the extended emission help us to understand the mechanisms in which the radio emitting particles gain their relativistic energies. Aims. We examine the possible acceleration mechanisms of the relativistic particles that are responsible for the extended radio emission in the merging galaxy cluster Abell 520. Methods. We performed new 145 MHz observations with the LOw Frequency ARay (LOFAR) and combined these with archival Giant Metrewave Radio Telescope (GMRT) 323 MHz and Very Large Array (VLA) 1.5 GHz data to study the morphological and spectral properties of extended cluster emission. The observational properties are discussed in the framework of particle acceleration models associated with cluster merger turbulence and shocks. Results. In Abell 520, we confirm the presence of extended (760 × 950 kpc2) synchrotron radio emission that has been classified as a radio halo. The comparison between the radio and X-ray brightness suggests that the halo might originate in a cocoon rather than from the central X-ray bright regions of the cluster. The halo spectrum is roughly uniform on the scale of 66 kpc. There is a hint of spectral steepening from the SW edge towards the cluster centre. Assuming diffusive shock acceleration (DSA), the radio data are suggestive of a shock Mach number of ℳSW = 2.6−0.2+0.3 that is consistent with the X-ray derived estimates. This is in agreement with the scenario in which relativistic electrons in the SW radio edge gain their energies at the shock front via acceleration of either thermal or fossil electrons. We do not detect extended radio emission ahead of the SW shock that is predicted if the emission is the result of adiabatic compression. An X-ray surface brightness discontinuity is detected towards the NE region that may be a counter shock of Mach number ℳNEX = 1.52±0.05. This is lower than the value predicted from the radio emission which, assuming DSA, is consistent with ℳNE = 2.1 ± 0.2. Conclusions. Our observations indicate that the radio emission in the SW of Abell 520 is likely effected by the prominent X-ray detected shock in which radio emitting particles are (re-)accelerated through the Fermi-I mechanism. The NE X-ray discontinuity that is approximately collocated with an edge in the radio emission hints at the presence of a counter shock.

scholarly journals On the Relation Between GRB Classes and X-ray Flashes

10.14311/1496 ◽  
2012 ◽  
Vol 52 (1) ◽  
Author(s):  
Z. Bagoly ◽  
P. Veres ◽  
I. Horváth ◽  
A. Mészáros ◽  
L. G. Balázs
Keyword(s):  
Physical Properties ◽  
Short Duration ◽  
Classification Scheme ◽  
Gamma Ray ◽  
Gamma Ray Bursts ◽  
The Other ◽  
X Ray ◽  
Intermediate Group ◽  
Long Duration

Gamma-ray bursts are usually classified into either short-duration or long-duration bursts. Going beyond the short-long classification scheme, it has been shown on statistical grounds that a third, intermediate population is needed in this classification scheme. We are looking for physical properties which discriminate the intermediate duration bursts from the other two classes. As the intermediate group is the softest, we argue that we have related them with X-ray flashes among the GRBs. We give a new, probabilistic definition for this class of events.

The Solar Energetic Particle Event of March 15 2013 - Characterization of the interplanetary medium conditions 

2021 ◽  
Author(s):  
Antonio Niemela ◽  
Nicolas Wijsen ◽  
Luciano Rodriguez ◽  
Jasmina Magdalenic ◽  
Stefaan Poedts
Keyword(s):  
Interplanetary Medium ◽  
Interplanetary Space ◽  
Solar Energetic Particle ◽  
Solar Energetic Particle Event ◽  
Coupled Models ◽  
Particle Radiation ◽  
X Ray ◽  
Particle Population ◽  
Long Duration

<p>On March 15, 2013, an Earth directed halo CME, associated with an SEP event, was observed. This study aims to characterize the interplanetary medium conditions in which the event propagated, in order to make the first steps towards the validation of the modeling of SEPs employing two recently coupled models, EUHFORIA (EUropean Heliosferic FORcasting Information Asset) and PARADISE (PArticle Radiation Asset Directed at Interplanetary Space Exploration).<br><br></p><p>The Sun in the days prior and after the event was very active, with several strong flares and coronal mass ejections during this period. The main event was associated with the long duration GOES M1.1 X-ray flare originating from the active region (AR) 11692, located at N11E12. Imagers aboard SOHO and STEREO spacecrafts observed the CME launch at 7:12 UT and the projected line of the sight speed was estimated to be about 1060 km/s. A rise in the $>$10 MeV GOES proton count was observed the following day, with flux exceeding the 1000 pfu threshold, and stayed above it for several days. Another strong CME was launched, within the following hours, towards the west but with a good magnetic connection to Earth's position, which could have accelerated even further the particle population seeded by the main event.</p><p><br>We model the solar wind and its transients CMEs with EUHFORIA, in order to obtain the realistic conditions of the ambient plasma through which the associated particles are propagating. Different spatial and temporal resolutions of the model will be explored to run the newly developed model for energetic protons PARADISE in an optimal environment and make a step towards better SEP predictions.</p>

scholarly journals Electron Acceleration in Solar Flares

1989 ◽  
Vol 104 (1) ◽  
pp. 95-103
Author(s):  
Wolfgang Dröge ◽  
Peter Meyer ◽  
Paul Evenson ◽  
Dan Moses
Keyword(s):  
Power Law ◽  
Distribution Functions ◽  
Shock Acceleration ◽  
Fermi Acceleration ◽  
Diffusive Shock Acceleration ◽  
X Ray ◽  
Electron Spectra ◽  
Flare Loops ◽  
Long Duration ◽  
The One

AbstractFor the period September 1978 to December 1982 we have identified 55 solar flare particle events for which our instruments on board the ISEE-3 (ICE) spacecraft detected electrons above 10 MeV. Combining our data with those from the ULEWAT spectrometer (MPI Garching and University of Maryland) electron spectra in the range from 0.1 to 100 MeV were obtained. The observed spectral shapes can be divided into two classes. The spectra of the one class can be fit by a single power law in rigidity over the entire observed range. The spectra of the other class deviate from a power law, instead exhibiting a steepening at low rigidities and a flattening at high rigidities. Events with power-law spectra are associated with impulsive (< 1 hr duration) soft X-ray emission, whereas events with hardening spectra are associated with long-duration (> 1 hr) soft X-ray emission. The characteristics of long-duration events are consistent with diffusive shock acceleration taking place high in the corona. Electron spectra of short-duration flares are well reproduced by the distribution functions derived from a model assuming simultaneous second-order Fermi acceleration and Coulomb losses operating in closed flare loops.

White-Light Coronal Structures: Streamers and CMEs

1994 ◽  
Vol 144 ◽  
pp. 82
Author(s):  
E. Hildner
Keyword(s):  
Emission Line ◽  
Electron Density ◽  
White Light ◽  
Coronal Mass Ejections ◽  
X Rays ◽  
Solar Cycles ◽  
Temperature Function ◽  
X Ray ◽  
Eclipse Observations ◽  
Coronal Structures

AbstractOver the last twenty years, orbiting coronagraphs have vastly increased the amount of observational material for the whitelight corona. Spanning almost two solar cycles, and augmented by ground-based K-coronameter, emission-line, and eclipse observations, these data allow us to assess,inter alia: the typical and atypical behavior of the corona; how the corona evolves on time scales from minutes to a decade; and (in some respects) the relation between photospheric, coronal, and interplanetary features. This talk will review recent results on these three topics. A remark or two will attempt to relate the whitelight corona between 1.5 and 6 R⊙to the corona seen at lower altitudes in soft X-rays (e.g., with Yohkoh). The whitelight emission depends only on integrated electron density independent of temperature, whereas the soft X-ray emission depends upon the integral of electron density squared times a temperature function. The properties of coronal mass ejections (CMEs) will be reviewed briefly and their relationships to other solar and interplanetary phenomena will be noted.

Solar Filaments as Tracers of Subsurface Processes

2000 ◽  
Vol 179 ◽  
pp. 177-183
Author(s):  
D. M. Rust
Keyword(s):  
Magnetic Fields ◽  
Magnetic Flux ◽  
Coronal Mass Ejections ◽  
Interplanetary Space ◽  
Intermediate Stage ◽  
Coronal Plasma ◽  
Magnetic Helicity ◽  
The Sun ◽  
New Paradigm ◽  
Solar Filaments

AbstractSolar filaments are discussed in terms of two contrasting paradigms. The standard paradigm is that filaments are formed by condensation of coronal plasma into magnetic fields that are twisted or dimpled as a consequence of motions of the fields’ sources in the photosphere. According to a new paradigm, filaments form in rising, twisted flux ropes and are a necessary intermediate stage in the transfer to interplanetary space of dynamo-generated magnetic flux. It is argued that the accumulation of magnetic helicity in filaments and their coronal surroundings leads to filament eruptions and coronal mass ejections. These ejections relieve the Sun of the flux generated by the dynamo and make way for the flux of the next cycle.

ASCAObservation of a Long‐Duration X‐Ray Flare from the W UMa–Type Binary VW Cephei

1998 ◽  
Vol 492 (2) ◽  
pp. 761-766 ◽  
Author(s):  
C. S. Choi ◽  
T. Dotani
Keyword(s):  
X Ray ◽  
Long Duration

Optimal Energy Storage Portfolio for High and Ultrahigh Carbon-Free and Renewable Power Systems

2021 ◽  
Author(s):  
Omar J Guerra ◽  
Joshua Eichman ◽  
Paul Denholm
Keyword(s):  
Energy Storage ◽  
Power Systems ◽  
Short Duration ◽  
Current Literature ◽  
Optimal Energy ◽  
Renewable Power ◽  
Long Duration ◽  
Storage Technologies

Achieving 100% carbon-free or renewable power systems can be facilitated by the deployment of energy storage technologies at all timescales, including short-duration, long-duration, and seasonal scales; however, most current literature...

Intracellular analysis of trigeminal motoneuron rhythmical activity during stimulation of pontomedullary reticular formation in anesthetized guinea pig

1989 ◽  
Vol 62 (6) ◽  
pp. 1225-1236 ◽  
Author(s):  
S. M. Gurahian ◽  
S. H. Chandler ◽  
L. J. Goldberg
Keyword(s):  
Reticular Formation ◽  
Short Duration ◽  
Field Potential ◽  
Membrane Potentials ◽  
Repetitive Stimulation ◽  
Jaw Movements ◽  
Postsynaptic Potentials ◽  
Duration Stimulus ◽  
Long Duration ◽  
Stimulation Of

1. The effects of repetitive stimulation of the nucleus pontis caudalis and nucleus gigantocellularis (PnC-Gi) of the reticular formation on jaw opener and closer motoneurons were examined. The PnC-Gi was stimulated at 75 Hz at current intensities less than 90 microA. 2. Rhythmically occurring, long-duration, depolarizing membrane potentials in jaw opener motoneurons [excitatory masticatory drive potential (E-MDP)] and long-duration hyperpolarizing membrane potentials [inhibitory masticatory drive potentials (I-MDP)] in jaw closer motoneurons were evoked by 40-Hz repetitive masticatory cortex stimulation. These potentials were completely suppressed by PnC-Gi stimulation. PnC-Gi stimulation also suppressed the short-duration, stimulus-locked depolarizations [excitatory postsynaptic potentials (EPSPs)] in jaw opener motoneurons and short-duration, stimulus-locked hyperpolarizations [inhibitory postsynaptic potentials (IPSPs)] in jaw closer motoneurons, evoked by the same repetitive cortical stimulation. 3. Short pulse train (3 pulses; 500 Hz) stimulation of the masticatory area of the cortex in the absence of rhythmical jaw movements activated the short-latency paucisynaptic corticotrigeminal pathways and evoked short-duration EPSPs and IPSPs in jaw opener and closer motoneurons, respectively. The same PnC-Gi stimulation that completely suppressed rhythmical MDPs, and stimulus-locked PSPs evoked by repetitive stimulation to the masticatory area of the cortex, produced an average reduction in PSP amplitude of 22 and 17% in jaw closer and opener motoneurons, respectively. 4. PnC-Gi stimulation produced minimal effects on the amplitude of the antidromic digastric field potential or on the intracellularly recorded antidromic digastric action potential. Moreover, PnC-Gi stimulation had little effect on jaw opener or jaw closer motoneuron membrane resting potentials in the absence of rhythmical jaw movements (RJMs). PnC-Gi stimulation produced variable effects on conductance pulses elicited in jaw opener and closer motoneurons in the absence of RJMs. 5. These results indicate that the powerful suppression of cortically evoked MDPs in opener and closer motoneurons during PnC-Gi stimulation is most likely not a result of postsynaptic inhibition of trigeminal motoneurons. It is proposed that this suppression is a result of suppression of activity in neurons responsible for masticatory rhythm generation.

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