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L. K. Jian C. T. Russell J. G. Luhmann P. J. MacNeice D. Odstrcil P. Riley J. A. Linker R. M. Skoug J. T. Steinberg 《Solar physics》2011,273(1):179-203
During the latitudinal alignment in 2004, ACE and Ulysses encountered two stream interaction regions (SIRs) each Carrington rotation from 2016 to 2018, at 1 and 5.4 AU, respectively.
More SIR-driven shocks were observed at 5.4 AU than at 1 AU. Three small SIRs at 1 AU merged to form a strong SIR at 5.4 AU.
We compare the Enlil model results with spacecraft observations from four aspects: i) the accuracy of the latest versions of models (WSA v2.2 and Enlil v2.7) vs. old versions (WSA v1.6 and Enlil v2.6), ii) the sensitivity to different solar magnetograms (MWO vs. NSO), iii) the sensitivity to different coronal models (WSA vs. MAS), iv) the predictive capability at 1 AU vs. 5.4 AU. We find the models can capture field sector boundaries with some time offset. Although the new versions have improved
the SIR timing prediction, the time offset can be up to two days at 1 AU and four days at 5.4 AU. The models cannot capture
some small-scale structures, including shocks and small SIRs at 1 AU. For SIRs, the temperature and total pressure are often
underestimated, while the density compression is overestimated. For slow wind, the density is usually overestimated, while
the temperature, magnetic field, and total pressure are often underestimated. The new versions have improved the prediction
of the speed and density, but they need more robust scaling factors for magnetic field. The Enlil model results are very sensitive
to different solar magnetograms and coronal models. It is hard to determine which magnetogram-coronal model combination is
superior to others. Higher-resolution solar and coronal observations, a mission closer to the Sun, together with simulations
of greater resolution and added physics, are ways to make progress for the solar wind modeling. 相似文献
2.
A. Papaioannou O. Malandraki A. Belov R. Skoug H. Mavromichalaki E. Eroshenko A. Abunin S. Lepri 《Solar physics》2010,266(1):181-193
In this work an analysis of a series of complex cosmic ray events that occurred between 17 January 2005 and 23 January 2005
using solar, interplanetary and ground based cosmic ray data is being performed. The investigated period was characterized
both by significant galactic cosmic ray (GCR) and solar cosmic ray (SCR) variations with highlighted cases such as the noticeable
series of Forbush effects (FEs) from 17 January 2005 to 20 January 2005, the Forbush decrease (FD) on 21 January 2005 and
the ground level enhancement (GLE) of the cosmic ray counter measurements on 20 January 2005. The analysis is focusing on
the aforementioned FE cases, with special attention drawn on the 21 January 2005, FD event, which demonstrated several exceptional
features testifying its uniqueness. Data from the ACE spacecraft, together with GOES X-ray recordings and LASCO CME coronagraph
images were used in conjunction to the ground based recordings of the Worldwide Neutron Monitor Network, the interplanetary
data of OMNI database and the geomagnetic activity manifestations denoted by K
p and D
st indices. More than that, cosmic ray characteristics as density, anisotropy and density gradients were also calculated. The
results illustrate the state of the interplanetary space that cosmic rays crossed and their corresponding modulation with
respect to the multiple extreme solar events of this period. In addition, the western location of the 21 January 2005 solar
source indicates a new cosmic ray feature, which connects the position of the solar source to the cosmic ray anisotropy variations.
In the future, this feature could serve as an indicator of the solar source and can prove to be a valuable asset, especially
when satellite data are unavailable. 相似文献
3.
Lavraud B. Gosling J. T. Rouillard A. P. Fedorov A. Opitz A. Sauvaud J.-A. Foullon C. Dandouras I. Génot V. Jacquey C. Louarn P. Mazelle C. Penou E. Phan T. D. Larson D. E. Luhmann J. G. Schroeder P. Skoug R. M. Steinberg J. T. Russell C. T. 《Solar physics》2009,256(1-2):379-392
We analyze Wind, ACE, and STEREO (ST-A and ST-B) plasma and magnetic field data in the vicinity of the heliospheric current sheet (HCS) crossed by all spacecraft between 22:15 UT on 31 March and 01:25 UT on 1 April 2007 corresponding to its observation at ST-A and ST-B, which were separated by over 1800 R E (or over 1200 R E across the Sun?–?Earth line). Although only Wind and ACE provided good ion flow data in accord with a solar wind magnetic reconnection exhaust at the HCS, the magnetic field bifurcation typical of such exhausts was clearly observed at all spacecraft. They also all observed unambiguous strahl mixing within the exhaust, consistent with the sunward flow deflection observed at Wind and ACE and thus with the formation of closed magnetic field lines within the exhaust with both ends attached to the Sun. The strong dawnward flow deflection in the exhaust is consistent with the exhaust and X-line orientations obtained from minimum variance analysis at each spacecraft so that the X-line is almost along the GSE Z-axis and duskward of all the spacecraft. The observation of strahl mixing in extended and intermittent layers outside the exhaust by ST-A and ST-B is consistent with the formation of electron separatrix layers surrounding the exhaust. This event also provides further evidence that balanced parallel and antiparallel suprathermal electron fluxes are not a necessary condition for identification of closed field lines in the solar wind. In the present case the origin of the imbalance simply is the mixing of strahls of substantially different strengths from a different solar source each side of the HCS. The inferred exhaust orientations and distances of each spacecraft relative to the X-line show that the exhaust was likely nonplanar, following the Parker spiral orientation. Finally, the separatrix layers and exhausts properties at each spacecraft suggest that the magnetic reconnection X-line location and/or reconnection rate were variable in both space and time at such large scales.
相似文献4.
Foullon C. Lavraud B. Wardle N. C. Owen C. J. Kucharek H. Fazakerley A. N. Larson D. E. Lucek E. Luhmann J. G. Opitz A. Sauvaud J.-A. Skoug R. M. 《Solar physics》2009,259(1-2):389-416
Solar Physics - Multiple current sheet crossings are ubiquitous features of the solar wind associated with high-beta plasma sheets, notably during the passage of the heliospheric current sheet... 相似文献
5.
We present a comprehensive survey of 230 interplanetary CMEs (ICMEs) during 1995 – 2004 using Wind and ACE in situ observations near one AU, and examine the solar-cycle variation of the occurrence rate, shock association rate, scale size,
velocity change, and other properties of ICMEs. The ICME occurrence rate increases (from 5 in 1996 to 40 in 2001) with solar
activity; and 66% of all ICMEs occurred with shock(s). A compound parameter, the total pressure perpendicular to the magnetic
field (Pt), i.e., the sum of magnetic and perpendicular plasma thermal pressures, assists us in effectively distinguishing ICMEs from other
solar-wind structures such as stream interactions, and in quantifying the interaction strength. We interpret the characteristic
signatures of the Pt temporal variation in terms of the inferred distance perpendicular to the flow to the center of the obstacle. Group 1 includes
events that appear to be traversed near the ICME center, showing an apparent enhanced central Pt; Group 3 represents ICMEs passed far away from the center, displaying a rapid rise and then gradual decay in Pt; and Group 2 includes events with intermediate signatures. About 36% of 198 classifiable ICMEs are Group 1 events, consistent
with the conventional wisdom that at one AU a magnetic cloud is found during crossings of only ~1/3 of ICMEs. Our set of Group
1 ICMEs and the set of magnetic clouds from other researchers have significant overlap and a similar solar-cycle dependence.
The rough decline of the Group 1 fraction as solar activity increases, is consistent with rough increases of scale size, shock
percentage, and peak Pt. These results call into question the need to have different mechanisms to create differently appearing ICMEs. Rather it
is possible that all ICMEs have a central flux rope that is traversed about 33% of the time, but in the majority of cases
is missed by the spacecraft.
Electronic Supplementary Material Supplementary material is available for this article at 相似文献
6.
Smith C.W. Ness N.F. Burlaga L.F. Skoug R.M. McComas D.J. Zurbuchen T.H. Gloeckler G. Haggerty D.K. Gold R.E. Desai M.I. Mason G.M. Mazur J.E. Dwyer J.R. Popecki M.A. Möbius E. Cohen C.M.S. Leske R.A. 《Solar physics》2001,204(1-2):227-252
We present ACE observations for the six-day period encompassing the Bastille Day 2000 solar activity. A high level of transient
activity at 1 AU, including ICME-driven shocks, magnetic clouds, shock-accelerated energetic particle populations, and solar
energetic ions and electrons, are described. We present thermal ion composition signatures for ICMEs and magnetic clouds from
which we derive electron temperatures at the source of the disturbances and we describe additional enhancements in some ion
species that are clearly related to the transient source. We describe shock acceleration of 0.3–2.0 MeV nucl−1 protons and minor ions and the relative inability of some of the shocks to accelerate significant energetic ion populations
near 1 AU. We report the characteristics of < 20 MeV nucl−1 solar energetic ions and < 0.32 MeV electrons and attempt to relate the release of energetic electrons to particular source
regions. 相似文献
7.
L. K. Jian C. T. Russell J. G. Luhmann R. M. Skoug J. T. Steinberg 《Solar physics》2008,249(1):85-101
We present comprehensive surveys of 203 stream interaction regions (SIRs) and 124 interplanetary CMEs (ICMEs) during 1979 – 1988
using Pioneer Venus Orbiter (PVO) in situ solar-wind observations at 0.72 AU and examine the solar-cycle variations of the occurrence rate, shock association rate,
duration, width, maximum total perpendicular pressure (P
t), maximum dynamic pressure, maximum magnetic field intensity, and maximum velocity change of these two large-scale solar-wind
structures. The medians, averages, and histogram distributions of these parameters are also reported. Furthermore, we sort
ICMEs into three groups based on the temporal profiles of P
t, and we investigate the variations of the fractional occurrence rate of three groups of ICMEs with solar activity. We find
that the fractional occurrence rate of magnetic-cloud-like ICMEs declined with solar activity, consistent with our former
1-AU results. This study at 0.72 AU provides a point of comparison in the inner heliosphere for examining the radial evolution
of SIRs and ICMEs. The width of SIRs and ICMEs increases by 0.04 and 0.1 AU, respectively, and the maximum P
t decreases to about 1/3 from Venus to Earth orbit. In addition, our work establishes the statistical properties of the solar-wind
conditions at 0.72 AU that control the solar-wind interaction with Venus and its atmosphere loss by related processes.
Electronic Supplementary Material The online version of this article () contains supplementary material, which is available to authorized users. 相似文献
8.
A stream interaction region (SIR) forms when a fast solar stream overtakes a slow stream, leading to structure that evolves
as an SIR moves away from the Sun. Based on Wind (1995 – 2004) and ACE (1998 – 2004) in situ observations, we have conducted a comprehensive survey of SIRs at one AU, including a separate assessment of the longer-lasting
corotating interaction regions (CIRs) that recur on more than one solar rotation. In all there are 196 CIRs, accounting for
about 54% of the 365 SIRs. The largest proportion of CIRs to SIRs (64%) appears in 1999, and the smallest proportion (49%)
is in 2002. Over the ten years, the annual number of SIR events varies little, from 32 up to 45. On average, the occurrence
rate of shocks at SIRs at one AU is about 24%. Seventy percent of the SIRs with shocks have only forward shocks, more than
twice the percentage of SIRs with only reverse shocks. This preponderance of forward shocks is consistent with the deflections
of forward and reverse shocks relative to the ecliptic plane. In order to help address the effect of SIRs and CIRs on geomagnetic
activity, we determine the solar-cycle variation of the event duration, scale size, the change in velocity from slow stream
to fast stream, and the solar-cycle variation of the maximum magnetic field, peak total perpendicular pressure, and other
properties. These statistics also provide a baseline for future studies at other heliocentric distances and for validating
heliospheric models.
Electronic Supplementary Material Supplementary material is available for this article at 相似文献
9.
L. K. Jian C. T. Russell J. G. Luhmann R. M. Skoug J. T. Steinberg 《Solar physics》2008,250(2):375-402
We have performed a survey of the characteristics of two types of large spatial-scale solar-wind structures, stream interaction
regions (SIRs), and interplanetary coronal mass ejections (ICMEs), near 5.3 AU, using solar-wind observations from Ulysses. Our study is confined to the three aphelion passes of Ulysses, and also within ± 10° of the solar ecliptic plane, covering a part of 1992, 1997 – 1998, and 2003 – 2005, representing three
slices of different phases of the solar activity cycle. Overall, there are 54 SIRs and 60 ICMEs in the survey. Many are merged
in hybrid events, suggesting that they have undergone multiple interactions prior to reaching Jovian orbit. About 91% of SIRs
occur with shocks, with 47% of such shocks being forward – reverse shock pairs. The solar-wind velocity sometimes stays constant
or even decreases within the interaction region near 5.3 AU, in contrast with the gradual velocity increase during SIRs at
1 AU. Shocks are driven by 58% of ICMEs, with 94% of them being forward shocks. Some ICMEs seem to have multiple small flux
ropes with different scales and properties. We quantitatively compare various properties of SIRs and ICMEs at 5.3 AU, and
study their statistical distributions and variations with solar activity. The width, maximum dynamic pressure, and peak perpendicular
pressure of SIRs all become larger than ICMEs. Dynamic pressure (P
dyn) is expected to be important for Jovian magnetospheric activity. We have examined the distributions of P
dyn of SIRs, ICMEs, and general solar wind, but these cannot explain the observed bimodal distribution of the location of the
Jovian magnetopause. By comparing the properties of SIRs and ICMEs at 0.72, 1, and 5.3 AU, we find that the ICME expansion
slows down significantly between 1 and 5.3 AU. Some transient and small streams in the inner heliosphere have merged into
a single interaction region.
Electronic Supplementary Material The online version of this article () contains supplementary material, which is available to authorized users. 相似文献
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