共查询到20条相似文献，搜索用时 15 毫秒
1.
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
2.
M. Youssef 《Earth, Moon, and Planets》2012,109(1-4):13-27
We studied the relation between the near-Earth signatures of the interplanetary coronal mass ejections (ICMEs) shocks such as sudden storms commencement (SSC), and their counterparts of coronal mass ejections (CMEs) observed near-Sun by solar and heliospheric observatory (SOHO)/large angle and spectrometric coronagraph (LASCO) coronagraph during 1996?C2008. Our result showed that there is a good correlation between the travel time of the ICMEs shocks and their associated radial speeds. Also we have separated the ICME shocks into two groups according to their effective acceleration and deceleration. The results showed that the faster ICME shocks (with negative accelerations which decelerated by solar wind plasma) are more correlated to their associated travel time than those with positive accelerations. 相似文献
3.
H. R. Lai C. T. Russell L. K. Jian X. Blanco-Cano B. J. Anderson J. G. Luhmann A. Wennmacher 《Solar physics》2012,278(2):421-433
The two major sources of collisionless shocks in the solar wind are interplanetary coronal mass ejections (ICMEs) and stream
interaction regions (SIRs). Previous studies show that some SIR-associated shocks form between Venus and Earth while most
form beyond 1 AU. Here we examine the high-resolution magnetometer records from Helios 1 and 2 obtained between 0.28 and 1 AU and from MESSENGER obtained between 0.3 and 0.7 AU to further refine our understanding
as to where, and in what context, shocks are formed in the inner solar system. From Helios data (Helios 1 from 1974 to 1981 and Helios 2 from 1976 to 1980), we find there were only a few shocks observed inside the orbit of Venus with the closest shock to the
Sun at 0.29 AU. We find that there is a strong correlation between shock occurrence and solar activity as measured by the
sunspot number. Most of the shocks inside of the orbit of Venus appear to be associated with ICMEs. Even the ICME-associated
shocks are quite weak inside the orbit of Venus. By comparing MESSENGER and STEREO results, from 2007 to 2009, we find that
in the deep solar minimum, SIR-driven shocks began to form at about 0.4 AU and increased in number with heliocentric distance. 相似文献
4.
S. E. Gibson G. de Toma B. Emery P. Riley L. Zhao Y. Elsworth R. J. Leamon J. Lei S. McIntosh R. A. Mewaldt B. J. Thompson D. Webb 《Solar physics》2011,274(1-2):5-27
Throughout months of extremely low solar activity during the recent extended solar-cycle minimum, structural evolution continued to be observed from the Sun through the solar wind and to the Earth. In 2008, the presence of long-lived and large low-latitude coronal holes meant that geospace was periodically impacted by high-speed streams, even though solar irradiance, activity, and interplanetary magnetic fields had reached levels as low as, or lower than, observed in past minima. This time period, which includes the first Whole Heliosphere Interval (WHI 1: Carrington Rotation (CR) 2068), illustrates the effects of fast solar-wind streams on the Earth in an otherwise quiet heliosphere. By the end of 2008, sunspots and solar irradiance had reached their lowest levels for this minimum (e.g., WHI 2: CR 2078), and continued solar magnetic-flux evolution had led to a flattening of the heliospheric current sheet and the decay of the low-latitude coronal holes and associated Earth-intersecting high-speed solar-wind streams. As the new solar cycle slowly began, solar-wind and geospace observables stayed low or continued to decline, reaching very low levels by June??C?July 2009. At this point (e.g., WHI 3: CR 2085) the Sun?CEarth system, taken as a whole, was at its quietest. In this article we present an overview of observations that span the period 2008??C?2009, with highlighted discussion of CRs 2068, 2078, and 2085. We show side-by-side observables from the Sun??s interior through its surface and atmosphere, through the solar wind and heliosphere and to the Earth??s space environment and upper atmosphere, and reference detailed studies of these various regimes within this topical issue and elsewhere. 相似文献
5.
E. K. J. Kilpua M. Mierla A. N. Zhukov L. Rodriguez A. Vourlidas B. Wood 《Solar physics》2014,289(10):3773-3797
We examine solar sources for 20 interplanetary coronal mass ejections (ICMEs) observed in 2009 in the near-Earth solar wind. We performed a detailed analysis of coronagraph and extreme ultraviolet (EUV) observations from the Solar Terrestrial Relations Observatory (STEREO) and Solar and Heliospheric Observatory (SOHO). Our study shows that the coronagraph observations from viewpoints away from the Sun–Earth line are paramount to locate the solar sources of Earth-bound ICMEs during solar minimum. SOHO/LASCO detected only six CMEs in our sample, and only one of these CMEs was wider than 120°. This demonstrates that observing a full or partial halo CME is not necessary to observe the ICME arrival. Although the two STEREO spacecraft had the best possible configuration for observing Earth-bound CMEs in 2009, we failed to find the associated CME for four ICMEs, and identifying the correct CME was not straightforward even for some clear ICMEs. Ten out of 16 (63 %) of the associated CMEs in our study were “stealth” CMEs, i.e. no obvious EUV on-disk activity was associated with them. Most of our stealth CMEs also lacked on-limb EUV signatures. We found that stealth CMEs generally lack the leading bright front in coronagraph images. This is in accordance with previous studies that argued that stealth CMEs form more slowly and at higher coronal altitudes than non-stealth CMEs. We suggest that at solar minimum the slow-rising CMEs do not draw enough coronal plasma around them. These CMEs are hence difficult to discern in the coronagraphic data, even when viewed close to the plane of the sky. The weak ICMEs in our study were related to both intrinsically narrow CMEs and the non-central encounters of larger CMEs. We also demonstrate that narrow CMEs (angular widths ≤?20°) can arrive at Earth and that an unstructured CME may result in a flux rope-type ICME. 相似文献
6.
M. J. Owens 《Solar physics》2018,293(8):122
Magnetic field and plasma properties of the solar wind measured in near-Earth space are a convolution of coronal source conditions and in-transit processes which take place between the corona and near-Earth space. Elemental composition and heavy ion charge states, however, are not significantly altered during transit to Earth and thus such properties can be used to diagnose the coronal source conditions of the solar wind observed in situ. We use data from the Advanced Composition Explorer (ACE) spacecraft to statistically quantify differences in the coronal source properties of interplanetary coronal mass ejections (ICMEs). Magnetic clouds, ICMEs which contain a magnetic flux-rope signature, display heavy ion properties consistent with significantly hotter coronal source regions than non-cloud ICMEs. Specifically, magnetic clouds display significantly elevated ion charge states, suggesting they receive greater heating in the low corona. Further dividing ICMEs by speed, however, shows this effect is primarily limited to fast magnetic clouds and that in terms of heavy ion properties, slow magnetic clouds are far more similar to non-cloud ICMEs. As such, fast magnetic clouds appear distinct from other ICME types in terms of both ion charge states and elemental composition. ICME speed, rather ICME type, correlates with helium abundance and iron charge state, consistent with fast ICMEs being heated through the more extended corona. Fast ICMEs also tend to be embedded within faster ambient solar wind than slow ICMEs, though this could be partly the result of in-transit drag effects. These signatures are discussed in terms of spatial sampling of ICMEs and from fundamentally different coronal formation and release processes. 相似文献
7.
I. G. Richardson 《Solar physics》2014,289(10):3843-3894
Previous studies have discussed the identification of interplanetary coronal mass ejections (ICMEs) near the Earth based on various solar wind signatures. In particular, methods have been developed of identifying regions of anomalously low solar wind proton temperatures (T p) and plasma compositional anomalies relative to the composition of the ambient solar wind that are frequently indicative of ICMEs. In this study, similar methods are applied to observations from the Ulysses spacecraft that was launched in 1990 and placed in a heliocentric orbit over the poles of the Sun. Some 279 probable ICMEs are identified during the spacecraft mission, which ended in 2009. The identifications complement those found independently in other studies of the Ulysses data, but a number of additional events are identified. The properties of the ICMEs detected at Ulysses and those observed near the Earth and in the inner heliosphere are compared. 相似文献
8.
We study the influence of the large-scale interplanetary magnetic field configuration on the solar energetic particles (SEPs) as detected at different satellites near Earth and on the correlation of their peak intensities with the parent solar activity. We selected SEP events associated with X- and M-class flares at western longitudes, in order to ensure good magnetic connection to Earth. These events were classified into two categories according to the global interplanetary magnetic field (IMF) configuration present during the SEP propagation to 1 AU: standard solar wind or interplanetary coronal mass ejections (ICMEs). Our analysis shows that around 20 % of all particle events are detected when the spacecraft is immersed in an ICME. The correlation of the peak particle intensity with the projected speed of the SEP-associated coronal mass ejection is similar in the two IMF categories of proton and electron events, ≈?0.6. The SEP events within ICMEs show stronger correlation between the peak proton intensity and the soft X-ray flux of the associated solar flare, with correlation coefficient r=0.67±0.13, compared to the SEP events propagating in the standard solar wind, r=0.36±0.13. The difference is more pronounced for near-relativistic electrons. The main reason for the different correlation behavior seems to be the larger spread of the flare longitude in the SEP sample detected in the solar wind as compared to SEP events within ICMEs. We discuss to what extent observational bias, different physical processes (particle injection, transport, etc.), and the IMF configuration can influence the relationship between SEPs and coronal activity. 相似文献
9.
10.
Measurement of the floor in the interplanetary magnetic field and estimation of the time-invariant open magnetic flux of the
Sun require knowledge of closed magnetic flux carried away by coronal mass ejections (CMEs). In contrast with previous papers,
we do not use global solar parameters to estimate such values: instead we identify different large-scale types of solar wind
for the 1976 – 2000 interval to obtain the fraction of interplanetary CMEs (ICMEs). By calculating the magnitude of the interplanetary
magnetic field B averaged over two Carrington rotations, the floor of the magnetic field can be estimated from the B value at a solar cycle minimum when the number of ICMEs is minimal. We find a value of 4.65±0.6 nT, in good agreement with
previous results. 相似文献
11.
An extended Ulysses interplanetary coronal mass ejections (ICMEs) list is used to statistically study the occurrence rate of ICMEs, the interaction
of ICMEs with solar wind, and the magnetic field properties in ICMEs. About 43% of the ICMEs are identified as magnetic clouds
(MCs). It is found that the occurrence rate of ICMEs approximately follows the solar activity level, except for the second
solar orbit; the rate is higher in the southern heliolatitude than in the northern heliolatitude; and it roughly decreases
with the increase of ICME speeds. Our results show that the speed difference between the ICME and the solar wind in front
of it shows a slight decrease with increasing heliocentric distance for ICMEs preceded by a shock, whereas no such dependence
is found for the ICMEs without shock association. It is also found that approximately 23% of the ICMEs are associated with
radial field events, in which the interplanetary magnetic field with near-radial direction lasts for many hours, in the Ulysses detected range, and these associated events are not necessarily confined to fast ICMEs or the trailing portions of ICMEs.
Nearly all these associated events occur during the period of declining solar wind speed and most of them occur at low heliolatitudes. 相似文献
12.
Barbara A. Emery Ian G. Richardson David S. Evans Frederick J. Rich Gordon R. Wilson 《Solar physics》2011,274(1-2):399-425
The behavior of a number of solar wind, radiation belt, auroral and geomagnetic parameters is examined during the recent extended solar minimum and previous solar cycles, covering the period from January 1972 to July 2010. This period includes most of the solar minimum between Cycles 23 and 24, which was more extended than recent solar minima, with historically low values of most of these parameters in 2009. Solar rotational periodicities from 5 to 27 days were found from daily averages over 81 days for the parameters. There were very strong 9-day periodicities in many variables in 2005?–?2008, triggered by recurring corotating high-speed streams (HSS). All rotational amplitudes were relatively large in the descending and early minimum phases of the solar cycle, when HSS are the predominant solar wind structures. There were minima in the amplitudes of all solar rotational periodicities near the end of each solar minimum, as well as at the start of the reversal of the solar magnetic field polarity at solar maximum (～?1980, ～?1990, and ～?2001) when the occurrence frequency of HSS is relatively low. Semiannual equinoctial periodicities, which were relatively strong in the 1995?–?1997 solar minimum, were found to be primarily the result of the changing amplitudes of the 13.5- and 27-day periodicities, where 13.5-day amplitudes were better correlated with heliospheric daily observations and 27-day amplitudes correlated better with Earth-based daily observations. The equinoctial rotational amplitudes of the Earth-based parameters were probably enhanced by a combination of the Russell-McPherron effect and a reduction in the solar wind-magnetosphere coupling efficiency during solstices. The rotational amplitudes were cross-correlated with each other, where the 27-day amplitudes showed some of the weakest cross-correlations. The rotational amplitudes of the >?2 MeV radiation belt electron number fluxes were progressively weaker from 27- to 5-day periods, showing that processes in the magnetosphere act as a low-pass filter between the solar wind and the radiation belt. The A p/K p magnetic currents observed at subauroral latitudes are sensitive to proton auroral precipitation, especially for 9-day and shorter periods, while the A p/K p currents are governed by electron auroral precipitation for 13.5- and 27-day periodicities. 相似文献
13.
E. K. J. Kilpua J. G. Luhmann J. Gosling Y. Li H. Elliott C. T. Russell L. Jian A. B. Galvin D. Larson P. Schroeder K. Simunac G. Petrie 《Solar physics》2009,256(1-2):327-344
It has been realized for some time that the slow solar wind with its embedded heliospheric current sheet often exhibits complex features suggesting at least partially transient origin. In this paper we investigate the structure of the slow solar wind using the observations by the Wind and STEREO spacecraft during two Carrington rotations (2054 and 2055). These occur at the time of minimum solar activity when the interplanetary medium is dominated by recurrent high-speed streams and large-scale interplanetary coronal mass ejections (ICMEs) are rare. However, the signatures of transients with small scale-sizes and/or low magnetic field strength (comparable with the typical solar wind value, ～?5 nT) are frequently found in the slow solar wind at these times. These events do not exhibit significant speed gradients across the structure, but instead appear to move with the surrounding flow. Source mapping using models based on GONG magnetograms suggests that these transients come from the vicinity of coronal source surface sector boundaries. In situ they are correspondingly observed in the vicinity of high density structures where the dominant electron heat flux reverses its flow polarity. These weak transients might be indications of dynamical changes at the coronal hole boundaries or at the edges of the helmet streamer belt previously reported in coronagraph observations. Our analysis supports the idea that even at solar minimum, a considerable fraction of the slow solar wind is transient in nature. 相似文献
14.
Coronal mass ejections and high-speed streams from the Sun, and related structures formed and evolved in interplanetary space,
i.e. interplanetary manifestations of CMEs (ICMEs) and stream interaction regions (SIRs)/corotating interaction regions (CIRs),
are mainly responsible for geomagnetic disturbances in the Earth’s magnetic environment. However, the presence or absence
of associated/finer structures of ICMEs (e.g., shock/sheath, magnetic cloud) and SIRs/CIRs (forward and reverse shocks, stream
interface) might influence their geoeffectiveness as these features within large-scale structures of ICMEs and SIRs display
different and varying plasma and field characteristics. In this work, we analyze the solar-wind plasma and field parameters
(plasma velocity, density and pressure, magnetic field, its north-south component and electric field) together with geomagnetic
activity parameters (kp and Dst), applying the method of superposed epoch analysis. By systematically changing the time of passage of different features
as epochs, e.g. discontinuities/shocks, CMEs/magnetic clouds in ICMEs and discontinuities/forward shocks in SIRs/CIRs, we
study the relative geoeffectiveness of not only the large-scale structures (ICMEs/SIRs/CIRs), but of their finer features
also. We critically analyze the differences in geoeffectiveness due to different structures and features, with distinct plasma/field
characteristics, and we utilize these results to understand the mechanism during their interaction with geospace. 相似文献
15.
In this study, we investigate the interplanetary consequences and travel time details of 58 coronal mass ejections (CMEs) in the Sun–Earth distance. The CMEs considered are halo and partial halo events of width \({>}\,120\)°. These CMEs occurred during 2009?–?2013, in the ascending phase of the Solar Cycle 24. Moreover, they are Earth-directed events that originated close to the centre of the solar disk (within about \(\pm30\)° from the Sun’s centre) and propagated approximately along the Sun–Earth line. For each CME, the onset time and the initial speed have been estimated from the white-light images observed by the LASCO coronagraphs onboard the SOHO space mission. These CMEs cover an initial speed range of \({\sim}\,260\,\mbox{--}\,2700~\mbox{km}\,\mbox{s}^{-1}\). For these CMEs, the associated interplanetary shocks (IP shocks) and interplanetary CMEs (ICMEs) at the near-Earth environment have been identified from in-situ solar wind measurements available at the OMNI data base. Most of these events have been associated with moderate to intense IP shocks. However, these events have caused only weak to moderate geomagnetic storms in the Earth’s magnetosphere. The relationship of the travel time with the initial speed of the CME has been compared with the observations made in the previous Cycle 23, during 1996?–?2004. In the present study, for a given initial speed of the CME, the travel time and the speed at 1 AU suggest that the CME was most likely not much affected by the drag caused by the slow-speed dominated heliosphere. Additionally, the weak geomagnetic storms and moderate IP shocks associated with the current set of Earth-directed CMEs indicate magnetically weak CME events of Cycle 24. The magnetic energy that is available to propagate CME and cause geomagnetic storm could be significantly low. 相似文献
16.
Svalgaard and Cliver (Astrophys. J. Lett. 661, L203, 2007) proposed that the solar-wind magnetic-field strength [B] at Earth has a ??floor?? value of ??4.6 nT in yearly averages, which is approached but not broached at solar minima. They attributed the floor to a constant baseline solar open flux. In both 2008 and 2009, the notion of such a floor was undercut by annual B averages of ??4 nT. Here we present a revised view of both the level and the concept of the floor. Two independent correlations indicate that B has a floor of ??2.8 nT in yearly averages. These are i) a relationship between solar polar-field strength and yearly averages of B for the last four 11-year minima (B MIN), and ii) a precursor relationship between peak sunspot number for cycles 14??C?23 and B MIN at their preceding minima. These correlations suggest that at 11-year minima, B consists of i) a floor of ??2.8 nT, and ii) a component primarily due to the solar polar fields that varies from ??0 nT to ??3 nT. The solar polar fields provide the ??seed?? for the subsequent sunspot maximum. Removing the ??2.8 nT floor from B MIN brings the percentage decrease in B between the 1996 and 2009 minima into agreement with the corresponding decrease in solar polar-field strength. Based on a decomposition of the solar wind (from 1972??C?2009) into high-speed streams, coronal mass ejections, and slow solar wind, we suggest that the source of the floor in B is the slow solar wind. During 2009, Earth was in slow solar-wind flows ??70% of the time. We propose that the floor corresponds to a baseline (non-cyclic or ground state) open solar flux of ??8×1013 Wb, which originates in persistent small-scale (supergranular and granular) field. 相似文献
17.
Interplanetary structures such as shocks, sheaths, interplanetary counterparts of coronal mass ejections (ICMEs), magnetic clouds, and corotating interaction regions (CIRs) are of special interest for the study of the transient modulation of galactic cosmic rays (GCRs). These structures modulate the GCR intensity with varying amplitudes and recovery-time profiles. It is known that ICMEs are mainly responsible for Forbush decreases in the GCR intensity. However, not all of the ICMEs produce such decreases in GCR intensity. We utilize GCR intensity data recorded by neutron monitors and solar-wind plasma/field data during the passage of ICMEs with different features and structures, and we perform a superposed-epoch analysis of the data. We also adopt the best-fit approach with suitable functions to interpret the observed similarities and differences in various parameters. Using the GCR-effectiveness as a measure of the cosmic-ray response to the passage of ICMEs, about half of the ICMEs identified during 1996?–?2009 are found to produce moderate to very large intensity depressions in GCR intensity. The ICMEs associated with halo CMEs, magnetic-cloud (MC) structures, bidirectional superthermal electron (BDE) signatures, and those driving shocks are 1.5 to 4 times more GCR effective than the ICMEs not associated with these structures/features. Further, the characteristic recovery time of GCR intensity due to shock/BDE/MC/halo-CME-associated ICMEs is larger than those due to ICMEs not associated with these structures/features. 相似文献
18.
The properties of the heliospheric magnetic field and the solar wind were substantially different in the unusual solar minimum between Cycles 23 and 24: the magnetic-field strength was substantially reduced, as were the flow properties of the solar wind, such as the mass flux. Explanations for these changes are offered that do not require any substantial reconsideration of the general understandings of the behavior of the heliospheric magnetic field and the solar wind that were developed in the minimum of Cycle 22?–?23. Solar-wind composition data are used to demonstrate that there are two distinct regions of solar wind: solar wind likely to originate from the stalk of the streamer belt (the highly elongated loops that underlie the heliospheric current sheet), and solar wind from outside this region. The region outside the streamer-stalk region is noticeably larger in the minimum of Cycle 23?–?24; however, the increased area can account for the reduction in the heliospheric magnetic-field strength in this minimum. Thus, the total magnetic flux contained in this region is the same in the two minima. Various correlations among the solar-wind mass flux and coronal electron temperature inferred from solar-wind charge states were developed for the Cycle 22?–?23 solar minimum. The data for the minimum of Cycle 23?–?24 suggest that the correlations still hold, and thus the basic acceleration mechanism is unchanged in this minimum. 相似文献
19.
R. P. Kane 《Solar physics》2006,233(1):107-115
This paper examines the variations of coronal mass ejections (CMEs) and interplanetary CMEs (ICMEs) during solar cycle 23
and compares these with those of several other indices. During cycle 23, solar and interplanetary parameters had an increase
from 1996 (sunspot minimum) to ∼2000, but the interval 1998–2002 had short-term fluctuations. Sunspot numbers had peaks in
1998, 1999, 2000 (largest), 2001 (second largest), and 2002. Other solar indices had matching peaks, but the peak in 2000
was larger than the peak in 2001 only for a few indices, and smaller or equal for other solar indices. The solar open magnetic
flux had very different characteristics for different solar latitudes. The high solar latitudes (45∘–90∘) in both N and S hemispheres had flux evolutions anti-parallel to sunspot activity. Fluxes in low solar latitudes (0∘–45∘) evolved roughly parallel to sunspot activity, but the finer structures (peaks etc. during sunspot maximum years) did not
match with sunspot peaks. Also, the low latitude fluxes had considerable N–S asymmetry. For CMEs and ICMEs, there were increases
similar to sunspots during 1996–2000, and during 2000–2002, there was good matching of peaks. But the peaks in 2000 and 2001
for CMEs and ICMEs had similar sizes, in contrast to the 2000 peak being greater than the 2001 peak for sunspots. Whereas
ICMEs started decreasing from 2001 onwards, CMEs continued to remain high in 2002, probably due to extra contribution from
high-latitude prominences, which had no equivalent interplanetary ICMEs or shocks. Cosmic ray intensity had features matching
with those of sunspots during 2000–2001, with the 2000 peak (on a reverse scale, actually a cosmic ray decrease or trough)
larger than the 2001 peak. However, cosmic ray decreases started with a delay and ended with a delay with respect to sunspot
activity. 相似文献
20.
T.R. McEnulty J.G. Luhmann I. de Pater D.A. Brain A. Fedorov T.L. Zhang E. Dubinin 《Planetary and Space Science》2010,58(14-15):1784-1791
We have used the ion mass analyzer (IMA) and magnetometer (MAG) on Venus Express (VEX) to study escaping O+ during interplanetary coronal mass ejections (ICMEs). Data from 389 VEX orbits during 2006 and 2007 revealed 265 samples of high energy pick-up ion features in 197 separate orbits. Magnetometer data during the same time period showed 17 ICMEs. The interplanetary conditions associated with the ICMEs clearly accelerate the pick-up ions to higher energies at lower altitudes compared to undisturbed solar wind. However, there is no clear dependence of the pick-up ion flux on ICMEs which may be attributed to the fact that this study used data from a period of low solar activity, when ICMEs are slow and weak relative to solar maximum. Alternatively, atmospheric escape rates may not be significantly changed during ICME events. 相似文献