摘要:

Coronal mass ejections (CMEs) are a major transient input of mass and energy into the solar wind. We review some of the past and present concepts that influence the development of models of coronal mass ejections, both for CME initiation and CME evolution and propagation in the solar wind. We use the flux cancellation model to illustrate present research on CMEs. Primarily for convenience, modeling of CME propagation has usually been treated separately from the initiation problem. We suggest that future computational modeling of interplanetary CMEs is likely to emphasize the need to study coronal initiation and solar wind propagation together. © 2003 American Institute of Physics

ISSN:0094-243X    

DOI:10.1063/1.1618691

出版商:AIP    

年代:1903

数据来源: AIP

摘要:

We investigate possible links between the activity manifestations in the solar corona and conditions in the solar wind. For the reduction of this immense task we have selected 206 events in the solar wind in 1997 – 2000 corresponding to geomagnetic events withAp> 20 (compiled into a database athttp://alpha.sinp.msu.ru/apev). Up to now, 24 events during the epoch of low solar activity (January 1997 – January 1998) are investigated. The solar wind conditions monitored by ACE and WIND spacecraft were traced back to the solar corona observed by SOHO/EIT. The search for coronal signatures which are probably associated with the disturbed solar wind conditions was performed. The coronal sources of these 24 events are identified, namely: eruptions in active regions, filament eruptions and coronal holes. It is shown that halo and partial halo CMEs observed within the SOHO/LASCO sensitivity limits are not necessary indicators of Earth‐directed eruptions, and coronal EUV dimmings can be used as a complementary indicator. We also found that a structure now conventionally called a “sigmoid” cannot be represented as a single S‐shaped loop (flux tube), but exhibits an assembly of many smaller structures. It could be formed and destroyed via eruptions. © 2003 American Institute of Physics

ISSN:0094-243X    

DOI:10.1063/1.1618692

出版商:AIP    

年代:1903

数据来源: AIP

摘要:

Between November 2000 and October 2001 the Ulysses spacecraft performed a fast traversal of the heliospheric latitudes between 80°S and 80°N, a period close to the activity maximum of the current solar cycle. This paper provides an overview of the Ulysses observations of the transient solar wind structures associated with coronal mass ejections (ICMEs) during this period. Compared to the previous Ulysses fast latitude scan near solar minimum in 1995, many more ICME related signatures were observed in the present data set. Events were encountered spread over the full latitude range between 80°S and 80°N. Those at high northern latitudes, where fast solar wind from a northern polar coronal hole had become re‐established, were of the over‐expanding type first identified in Ulysses data at mid‐latitudes near solar minimum. The signatures of these events and their latitude dependence are discussed and some ongoing and possible future studies with this data set are described. © 2003 American Institute of Physics

ISSN:0094-243X    

DOI:10.1063/1.1618693

出版商:AIP    

年代:1903

数据来源: AIP

摘要:

The fast‐moving protons from the solar wind plasma convert into energetic hydrogen atoms by charge‐exchange with the background hydrogen from the interstellar medium. If created in the excited state, the energetic atoms will emit photons, with frequency Doppler‐shifted away from the resonance frequency range of the background hydrogen. We estimate the flux and the spectrum of photons from the de‐excitation of the H(2p) state of the energetic hydrogen atoms deriving from the pick‐up protons in the solar wind and from the thermal protons in the hot plasma region beyond the solar wind termination shock. We also discuss the possibility of detection of the photon flux from this source. © 2003 American Institute of Physics

ISSN:0094-243X    

DOI:10.1063/1.1618694

出版商:AIP    

年代:1903

数据来源: AIP

摘要:

During the current solar maximum (Cycle 23), several major CMEs associated with solar flares produced large transient flows and shocks which were observed by widely‐separated spacecraft such as Wind at Earth and Voyager 2 beyond 60 AU. Using data from these spacecraft and numerical models, we study shock propagation and interaction in the outer heliosphere. We demonstrate that a strong shock in the distant heliosphere could be an outer heliospheric remnant of a strong shock in the inner heliosphere (“one to one” relationship), or it could be an outcome of the successive interaction and merging of a series of interplanetary shocks (“one to many” relationship). © 2003 American Institute of Physics

ISSN:0094-243X    

DOI:10.1063/1.1618695

出版商:AIP    

年代:1903

数据来源: AIP

摘要:

Interplanetary scintillation (IPS) measurements made with the Solar‐Terrestrial Environment Laboratory, Nagoya University, multi‐station system at 327 MHz are used to study the global structure of the interplanetary counterpart of coronal mass ejections (so‐called interplanetary CMEs or ICMEs). We have analyzed our IPS data of four ICME events which occurred successively in July 2000; those are 2000 July 10, 11, 12 and 14 events (the last one corresponds to “Bastille day event”). We have employed the model fitting method to obtain unbiased three‐dimensional properties of ICME from IPS observations. The parameters determined here include the location of the ICME center, the e‐folding radial thickness and angular span, anisotropy of the angular extent, the local enhancement factor, the (average) expansion speed, and its angular dependence. The results suggest that the global shape of July 12 and 14 events were loop‐like; the latitude angular span of these events was much smaller than the longitude one. The July 10 and 11 events are found to be explained excellently by a shell‐shape ICME model. The mass contained by the ICME has been estimated using information on the global structure obtained here. © 2003 American Institute of Physics

ISSN:0094-243X    

DOI:10.1063/1.1618696

出版商:AIP    

年代:1903

数据来源: AIP

摘要:

The notion that a magnetic cloud may consist not of one but of a few closely interacting magnetic tubes came from the analysis of the relation between the electron temperature Teand plasma density Ne(Fainberg et al. 1996). The log‐log plot of Teversus Neof data in the 10–13 June 1993 Ulysses magnetic cloud revealed two polytropes (both with &ggr;e< 1) which have been attributed by Osherovich, Fainberg and Stone (1999a) to two helices embedded in the same cylindrical flux rope. In contrast to configurations with cylindrical symmetry, magnetic configurations with helical symmetry allow a description of many helices which in cross section look like distorted flux ropes. We present elements of the magnetic and thermodynamic structure of the Oct 18–21, 1995 magnetic cloud observed by Wind. Our research is complementary to previous studies of this cloud by other authors (Larson et al. 1997; Lepping et al. 1997; Janoo et al. 1998). The log‐log plots of Tevs Nesuggest that this cloud consists of eight magnetic tubes with polytropic indices below unity and a few non‐coherent structures for which the polytropic relation is not valid. The solar wind quasi‐invariant (Osherovich et al., 1999b) for this cloud strongly anti‐correlates with the Dst index for the resulting magnetic storm. © 2003 American Institute of Physics

ISSN:0094-243X    

DOI:10.1063/1.1618697

出版商:AIP    

年代:1903

数据来源: AIP

摘要:

We found a new class of solutions for MHD equations that satisfies the condition that cylindrical flux ropes can expand self‐similarly even when the polytropic index &ggr; is larger than 1. We achieved this by including the effects of elongation along the symmetry axis as well as radial expansion and assuming that the radial expansion rate is the same as the elongation rate. © 2003 American Institute of Physics

ISSN:0094-243X    

DOI:10.1063/1.1618698

出版商:AIP    

年代:1903

数据来源: AIP

摘要:

Trying to get light into the paradigm of forecasting geomagnetic activity, we have looked for a relationship between geoeffectiveness and the orientation and helicity of magnetic clouds. During the years 1995–2000, we have selected all the geomagnetic storms with Dst index less than −70 nT. Then, we have inspected WIND data looking for a possible magnetic cloud related to every storm event. When a magnetic cloud is encountered, we have fitted to experimental data a model that we have developed for the magnetic cloud topology in order to obtain the attitude of the magnetic cloud and its helicity. On the basis of the results obtained, a close relationship is observed between the orientation of the magnetic cloud and its helicity, and the geomagnetic activity. © 2003 American Institute of Physics

ISSN:0094-243X    

DOI:10.1063/1.1618699

出版商:AIP    

年代:1903

数据来源: AIP

摘要:

This paper summarizes the numerical results obtained by three‐dimensional MHD simulations of the interaction between the solar wind and interstellar medium inRatkiewicz and Ben‐Jaffel[2002],Ratkiewicz and McKenzie[2002], andRatkiewicz and Webb[2002]. We analyze the configuration in which Maxwell stresses lead to squeezing and/or pushing the heliospheric boundary. In particular, we explain the mechanism giving rise to a suction effect of the heliopause. Numerical results for the case of aligned interstellar MHD flow are compared with previous studies. © 2003 American Institute of Physics

ISSN:0094-243X    

DOI:10.1063/1.1618700

出版商:AIP    

年代:1903

数据来源: AIP