Acceleration of electrons in absence of detectable optical flares deduced from type III radio bursts,Hα activity and soft X-ray emission     

Kane  S. R.  Kreplin  R. W.  Martres  M. -J.  Pick  M.  Soru-Escaut  I. 《Solar physics》1974,38(2):483-497

The relationship between H absorption features, type III radio bursts and soft X-ray emission has been examined in order to determine the characteristics of the particle acceleration process operating when a H-flare may not be detectable. It is found that transient H activity observed in the absence of reported flares is associated with production of relatively weak type III radio and soft X-ray emission. Since such optical phenomena are much more frequent than flares themselves, it is concluded that instabilities generating fast particles may be produced in the corona in a quasi-continuous way with coincident perturbations in the lower solar atmosphere.The soft X-ray component, which is similar to the precursor in flares, is not necessarily the direct product of fast particles, but is probably associated with some type of heating since both the soft X-ray emission and the H features exhibit a similar evolution, the type III bursts occurring near the maximum of this perturbation. The observations are consistent with a model in which the electron acceleration region is located at an altitude where the ion density is 10⁹ cm^–3 and most of the accelerated electrons( 20 keV) are confined to coronal altitudes where the ion density is 10¹⁰ cm^–3.  相似文献   

Über eine Neue Methode zur Herstellung von Karten Topographischer Korrektionen     

Miloš Pick 《Studia Geophysica et Geodaetica》1958,2(4):334-344

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Solar coronal streamers observed at 169 MHz with the Nançay East-West radioheliograph     

F. Axisa  Y. Avignon  M. J. Martres  M. Pick  P. Simon 《Solar physics》1971,19(1):110-127

The slowly varying component of the Sun at 169 MHz for the period August 1962 to March 1966 has been studied, using daily data from the East West radioheliograph at Nançay.By relating these radio data to the optical features visible on the solar disc (calcium plages and filaments), this thermal radio-emission can be satisfactorily interpreted as originating in both helmets and active streamers:The radio-sources responsible for this emission are linked to the presence of filaments. Depending on the cases, these filaments are either very far from any calcium plage, or closely associated with them.The cross-sectional area of such sources is often far from having circular symmetry and seems to be closely related to the configuration of the underlying filament itself.In several cases, the altitude of the sources can be estimated, and a typical value of about 270000 km is found. In this respect no significant difference is found between radio-sources related to a filament closely associated with a calcium plage, and those which are related to a filament very far from such plages.At 169 MHz, coronal enhancements provide a relatively small contribution to the slowly varying component.Finally, the observations are used to derive a morphological model for streamers in the medium corona, and several implications of such a model are briefly discussed.  相似文献   

Relationship between type III and microwave radiobursts and the role of magnetic configuration     

M. Pick 《Solar physics》1977,53(1):241-242

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How Can Active Region Plasma Escape into the Solar Wind from Below a Closed Helmet Streamer?     

C. H. Mandrini  F. A. Nuevo  A. M. Vásquez  P. Démoulin  L. van Driel-Gesztelyi  D. Baker  J. L. Culhane  G. D. Cristiani  M. Pick 《Solar physics》2014,289(11):4151-4171

Recent studies show that active-region (AR) upflowing plasma, observed by the EUV-Imaging Spectrometer (EIS) onboard Hinode, can gain access to open-field lines and be released into the solar wind (SW) via magnetic-interchange reconnection at magnetic null-points in pseudo-streamer configurations. When only one bipolar AR is present on the Sun and is fully covered by the separatrix of a streamer, such as AR 10978 in December 2007, it seems unlikely that the upflowing AR plasma can find its way into the slow SW. However, signatures of plasma with AR composition have been found at 1 AU by Culhane et al. (Solar Phys. 289, 3799, 2014) that apparently originated west of AR 10978. We present a detailed topology analysis of AR 10978 and the surrounding large-scale corona based on a potential-field source-surface (PFSS) model. Our study shows that it is possible for the AR plasma to move around the streamer separatrix and be released into the SW via magnetic reconnection, which occurs in at least two main steps. We analyse data from the Nançay Radioheliograph (NRH) in a search for evidence of the chain of magnetic reconnections that we propose. We find a noise storm above the AR and several varying sources at 150.9 MHz. Their locations suggest that they might be associated with particles accelerated during the first-step reconnection process at a null point well outside of the AR. We find no evidence of the second reconnection step in the radio data, however. Our results demonstrate that even when it appears highly improbable for the AR plasma to reach the SW, indirect channels involving a sequence of reconnections can make it possible.  相似文献   

Measurements of hot plasmas in the magnetosphere of Jupiter     

L.J. Lanzerotti  T.P. Armstrong  C.G. Maclennan  G.M. Simnett  A.F. Cheng  R.E. Gold  D.J. Thomson  S.M. Krimigis  K.A. Anderson  S.E. Hawkins III  M. Pick  E.C. Roelof  E.T. Sarris  S.J. Tappin 《Planetary and Space Science》1993,41(11-12)

This paper presents an overview of a number of the principal findings regarding the hot plasmas (E 50 keV) in Jupiter's magnetosphere by the HISCALE instrument during the encounter of the Ulysses spacecraft with the planet in February 1992. The hot plasma ion fluxes measured by HI-SCALE in the dayside magnetosphere are similar to those measured in the same energy range in this region by the Voyager spacecraft in 1979. Within the dayside plasma sheet, the hot-ion energy densities are comparable with, or larger than, the magnetic field energy densities; these hot ions are found to corotate at about one-half the planetary corotational speed. For ions of energies 500 keV/nucleon, the protons contributed from 50–60% to as much as 80% of the energy content of these plasmas. Strong, magnetic-field-aligned streaming was found for both the ions and electrons in the high-latitude duskside magnetosphere. The ion and electron pitch-angle distributions could be characterized by cos²⁵ α throughout many of the high anisotropy intervals of the outbound pass. There is some evidence in the ion pitch-angle distributions for a corotational component in the hot plasmas at high Jovian latitudes. While there are limitations owing to the finite geometries of the detector telescope systems on the determination of the angular spreads of the ion and electron beams, the measurements show that there are intervals when the particle distributions are not bidirectional. At such times, locally the hot plasmas could be carrying currents of 10⁻⁴μAm⁻². The temporal variations in the streaming electron fluxes are substantially larger than the variations measured for the fluxes that are more locally mirroring. The temporal variations contain periodicities that may correspond to hydromagnetic wave frequencies in the magnetosphere as well as to larger scale motions of magnetospheric plasmas. On nearly half of the days for about a 130 day interval around the time of the Ulysses encounter with the planet, particles of Jovian origin were measured in the interplanetary medium. An event discussed herein shows evidence of an energy dependence of the particle release process from the planetary magnetosphere into the interplanetary medium.  相似文献   

Observations of beam propagation     

M. Pick  G. H. J. Van Den Oord 《Solar physics》1990,130(1-2):83-99

We discuss the observational evidence for propagating electron distributions in the solar corona as obtained from type III observations. The location of the beam acceleration region together with the effects of the ambient medium on beam propagation are discussed in the framework of recent observational and theoretical developments. The results of combined X-ray and radio observations obtained during and after the Solar Maximum Year are summarized. Special attention is paid to the effect of the small-scale structure of the corona on the observed radio emission. We outline various desirable developments which are necessary to improve the understanding of the behaviour of charged particle beams in magnetized plasmas.  相似文献   

Association between gradual hard X-Ray emission and metric continua during large flares     

L. Klein  K. Anderson  M. Pick  G. Trottet  N. Vilmer  S. Kane 《Solar physics》1983,84(1-2):295-310

X-ray radiation is used to study coronal phenomena in conjunction with meter wave observations during some large solar flares. It is found that metric flare continua and moving type IV bursts are associated with gradual and long lasting (a few tens of minutes) microwave and hard X-ray emissions. The detailed temporal analysis reveals that although metric and hard X-ray sources are located at very different heights, both kinds of emission result from a common and continuous/repetitive injection of electrons in the corona. The late part of the metric event (stationary type IV burst) is only associated with soft X-ray radiation. This indicates that the mean energy of the radiating electrons is lower during stationary type IV bursts than during the earlier parts of the event.  相似文献   

A Radio Burst and Its Associated CME on March 17, 2002     

Y. Yan  M. Pick  M. Wang  S. Krucker  A. Vourlidas 《Solar physics》2006,239(1-2):277-292

In this study, we present a detailed analysis, based on multiwavelength observations and magnetic field extrapolation, of a radio and X-ray event observed on March 17, 2002. This event was accompanied by a Coronal Mass Ejection (CME) observed by the Large-Angle Spectrometric Coronagraph (LASCO) aboard SOHO. During the main event, the Reuven Ramaty High-Energy Solar Spectroscopic Imager (RHESSI) mission observed a hard X-ray emission correlated in time with the development of a type III burst group. The CME development, the hard X-ray emission, and the type III burst group appear to be closely associated. The multifrequency Nançay Radioheliograph (NRH) shows that the type III bursts are produced at a distance from the active region that progressively increases with time. Their emitting sources are distributed along the western edge of the CME. We conclude the type III electron beams propagate in the interface region between the ascending CME and the neighboring open field lines. Due to the development of the CME, this region becomes progressively highly compressed. By measuring, at each frequency, the shift versus time of the type III positions, we estimate that the electron density in this compression region increased roughly by a factor of 10 over a few minutes. Another signature of this compression region is a narrow white light feature interpreted as a coronal shock driven by the CME lateral expansion.  相似文献   

Coronal and heliospheric observations of solar particle events     

Monique Pick 《Astrophysics and Space Science》1996,243(1):179-186

Observations of accelerated particle beams are used to probe the coronal and interplanetary magnetic field structures over large distances from the Sun on the order of a few AU and for various heliolatitudes. It is shown that the propagation of low energy particles is very much controled by discrete interplanetary magnetic field structures. These discrete magnetic structures are sometimes embedded within interplanetary solar wind plasma disturbances, commonly called CMEs. The connection between the corona and the interplanetary medium is discussed. These observations lead to new insights on the origin of accelerated particles detected in association with CMEs.  相似文献