Organization of Energetic Particles by the Solar Wind Structure During the Declining to Minimum Phase of Solar Cycle 23

We investigate the organization of the low energy energetic particles (≤1 MeV) by solar wind structures, in particular corotating interaction regions (CIRs) and shocks driven by interplanetary coronal mass ejections, during the declining-to-minimum phase of Solar Cycle 23 from Carrington rotation 1999 to 2088 (January 2003 to October 2009). Because CIR-associated particles are very prominent during the solar minimum, the unusually long solar minimum period of this current cycle provides an opportunity to examine the overall organization of CIR energetic particles for a much longer period than during any other minimum since the dawn of the Space Age. We find that the particle enhancements associated with CIRs this minimum period recurred for many solar rotations, up to 30 at times, due to several high-speed solar wind streams that persisted. However, very few significant CIR-related energetic particle enhancements were observed towards the end of our study period, reflecting the overall weak high-speed streams that occurred at this time. We also contrast the solar minimum observations with the declining phase when a number of solar energetic particle events occurred, producing a mixed particle population. In addition, we compare the observations from this minimum period with those from the previous solar cycle. One of the main differences we find is the shorter recurrence rate of the high-speed solar wind streams (～10 solar rotations) and the related CIR energetic particle enhancements for the Solar Cycle 22 minimum period. Overall our study provides insight into the coexistence of different populations of energetic particles, as well as an overview of the large-scale organization of the energetic particle populations approaching the beginning of Solar Cycle 24.     

Corotating Shock Waves and the Solar-wind Source of Energetic Ion bundances: Power Laws in $$/Q$Q$

We find that element abundances in energetic ions accelerated by shock waves formed at corotating interaction regions (CIRs) mirror the abundances of the solar wind modified by a decreasing power-law dependence on the mass-to-charge ratio \(A\)/\(Q\) of the ions. This behavior is similar in character to the well-known power-law dependence on \(A\)/\(Q\) of abundances in large gradual solar energetic particles (SEP). The CIR ions reflect the pattern of \(A\)/\(Q\), with \(Q\) values of the source plasma temperature or freezing-in temperature of 1.0?–?1.2 MK typical of the fast solar wind in this case. Thus the relative ion abundances in CIRs are of the form \((A\mbox{/}Q)^{a}\), where \(a\) is nearly always negative and evidently decreases with distance from the shocks, which usually begin beyond 1 AU. For one unusual historic CIR event where \(a \approx 0\), the reverse shock wave of the CIR seems to occur at 1 AU, and these abundances of the energetic ions become a direct proxy for the abundances of the fast solar wind.     

Properties of Stream Interactions at One AU During 1995 – 2004

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     

Current and high-$\beta $ sheets in CIR streams: statistics and interaction with the HCS and the magnetosphere

Thirty events of CIR streams (corotating interaction regions between fast and slow solar wind) were analyzed in order to study statistically plasma structure within the CIR shear zones and to examine the interaction of the CIRs with the heliospheric current sheet (HCS) and the Earth’s magnetosphere. The occurrence of current layers and high-beta plasma sheets in the CIR structure has been estimated. It was found that on average, each of the CIR streams had four current layers in its structure with a current density of more than \(0.12~\mbox{A}/\mbox{m}^{2}\) and about one and a half high-beta plasma regions with a beta value of more than five. Then we traced how and how often the high-speed stream associated with the CIR can catch up with the heliospheric current sheet (HCS) and connect to it. The interface of each fourth CIR stream coincided in time within an hour with the HCS, but in two thirds of cases, the CIR connection with the HCS was completely absent. One event of the simultaneous observation of the CIR stream in front of the magnetosphere by the ACE satellite in the vicinity of the \(L1\) libration point and the Wind satellite in the remote geomagnetic tail was considered in detail. Measurements of the components of the interplanetary magnetic field and plasma parameters showed that the overall structure of the stream is conserved. Moreover, some details of the fine structure are also transferred through the magnetosphere. In particular, the so-called “magnetic hole” almost does not change its shape when moving from \(L1\) point to a neighborhood of \(L2\) point.     

In situ Observations of CIRs on STEREO,Wind, and ACE During 2007 – 2008

During the 2007 and 2008 solar minimum period, STEREO, Wind, and ACE observed numerous Corotating Interaction Regions (CIRs) over spatial separations that began with all the spacecraft close to Earth, through STEREO separation angles of ～?80 degrees in the fall of 2008. Over 35 CIR events were of sufficient intensity to allow measurement of He and heavy ion spectra using the IMPACT/SIT, EPACT/STEP and ACE/ULEIS instruments on STEREO, Wind, and ACE, respectively. In addition to differences between the spacecraft expected on the basis of simple corotation, we observed several events where there were markedly different time-intensity profiles from one spacecraft to the next. By comparing the energetic particle intensities and spectral shapes along with solar wind speed we examine the extent to which these differences are due to temporal evolution of the CIR or due to variations in connection to a relatively stable interaction region. Comparing CIRs in the 1996?–?1997 solar minimum period vs. 2007?–?2008, we find that the 2007?–?2008 period had many more CIRs, reflecting the presence of more high-speed solar wind streams, whereas 1997 had almost no CIR activity.

     

Solar Wind Sources in the Late Declining Phase of Cycle 23: Effects of the Weak Solar Polar Field on High Speed Streams

The declining phases of solar cycles are known for their high speed solar wind streams that dominate the geomagnetic responses during this period. Outstanding questions about these streams, which can provide the fastest winds of the solar cycle, concern their solar origins, persistence, and predictability. The declining phase of cycle 23 has lasted significantly longer than the corresponding phases of the previous two cycles. Solar magnetograph observations suggest that the solar polar magnetic field is also ～?2?–?3 times weaker. The launch of STEREO in late 2006 provided additional incentive to examine the origins of what is observed at 1 AU in the recent cycle, with the OMNI data base at the NSSDC available as an Earth/L1 baseline for comparisons. Here we focus on the year 2007 when the solar corona exhibited large, long-lived mid-to-low latitude coronal holes and polar hole extensions observed by both SOHO and STEREO imagers. STEREO provides in situ measurements consistent with rigidly corotating solar wind stream structure at up to ～?45° heliolongitude separation by late 2007. This stability justifies the use of magnetogram-based steady 3D solar wind models to map the observed high speed winds back to their coronal sources. We apply the WSA solar wind model currently running at the NOAA Space Weather Prediction Center with the expectation that it should perform its best at this quiet time. The model comparisons confirm the origins of the observed high speed streams expected from the solar images, but also reveal uncertainties in the solar wind source mapping associated with this cycle’s weaker solar polar fields. Overall, the results illustrate the importance of having accurate polar fields in synoptic maps used in solar wind forecast models. At the most fundamental level, they demonstrate the control of the solar polar fields over the high speed wind sources, and thus one specific connection between the solar dynamo and the solar wind character.     

A Multispacecraft Analysis of a Small-Scale Transient Entrained by Solar Wind Streams

The images taken by the Heliospheric Imagers (HIs), part of the SECCHI imaging package onboard the pair of STEREO spacecraft, provide information on the radial and latitudinal evolution of the plasma compressed inside corotating interaction regions (CIRs). A plasma density wave imaged by the HI instrument onboard STEREO-B was found to propagate towards STEREO-A, enabling a comparison between simultaneous remote-sensing and in situ observations of its structure to be performed. In situ measurements made by STEREO-A show that the plasma density wave is associated with the passage of a CIR. The magnetic field compressed after the CIR stream interface (SI) is found to have a planar distribution. Minimum variance analysis of the magnetic field vectors shows that the SI is inclined at 54° to the orbital plane of the STEREO-A spacecraft. This inclination of the CIR SI is comparable to the inclination of the associated plasma density wave observed by HI. A small-scale magnetic cloud with a flux rope topology and radial extent of 0.08 AU is also embedded prior to the SI. The pitch-angle distribution of suprathermal electrons measured by the STEREO-A SWEA instrument shows that an open magnetic field topology in the cloud replaced the heliospheric current sheet locally. These observations confirm that HI observes CIRs in difference images when a small-scale transient is caught up in the compression region.     

Mapping Solar Wind Streams from the Sun to 1 AU: A Comparison of Techniques

A variety of techniques exist for mapping solar wind plasma and magnetic field measurements from one location to another in the heliosphere. Such methods are either applied to extrapolate solar data or coronal model results from near the Sun to 1 AU (or elsewhere), or to map in-situ observations back to the Sun. In this study, we estimate the sensitivity of four models for evolving solar wind streams from the Sun to 1 AU. In order of increasing complexity, these are: i) ballistic extrapolation; ii) ad hoc kinematic mapping; iii) 1-D upwinding propagation; and iv) global heliospheric MHD modeling. We also consider the effects of the interplanetary magnetic field on the evolution of the stream structure. The upwinding technique is a new, simplified method that bridges the extremes of ballistic extrapolation and global heliospheric MHD modeling. It can match the dynamical evolution captured by global models, but is almost as simple to implement and as fast to run as the ballistic approximation.     

Statistical relationship between solar wind conditions and geomagnetic storms in 1998-2008

Applying ACE data and pressure-corrected Dst index (Dst*), annual distributions of solar wind structures detected at L1 point (the first Lagrangian point between solar-terrestrial interval) and correlations between solar wind structures and geomagnetic storms in 1998-2008 have been studied. It was found that, within the Earth's upstream solar wind, the dominant feature was interplanetary coronal mass ejections (ICMEs), primarily magnetic clouds, during solar maximum period but corotating interaction regions (CIRs) at solar minimum. During rising and declining phases, solar wind features became unstable for the complicated solar corona transition processes between the maximum and minimum phases, and there was a high CIR occurrence rate in 2003, the early period of the declining phase, for the Earth's upstream solar wind was dominated by high-speed southern coronal-hole outflows at that time. The occurrence rate of sector boundary crossing (SBC) events was evidently higher at the late half of declining phase and minimum period. ICMEs mainly centered on the maximum period but CIRs on all the declining phase. The occurrence rate of ICMEs was 1.3 times of that of CIRs, and more than half of ICMEs were magnetic clouds (MCs). Half of magnetic clouds could drive interplanetary shock and played a crucial role for geomagnetic storms generation, especially intense storms (Dst*≤100 nT), in which 45% were jointly induced by sheath region and driving MC structure. Sixty percent of intense storms were totally induced by shock-driving MCs; moreover, 74% of intense storms were driven by magnetic clouds, 81% of them driven by ICMEs. Shock-driving MC was the most geoeffective interplanetary source for four fifths of it able to lead to storms and more than one-third to intense storms. The rest of intense storms (19%) were induced just by 3% of all detected CIRs, and most of CIRs (53%) were corresponding to nearly 40% moderate and small storms (−100 nT<Dst*≤−30 nT). The true sector boundary crossing (SBC) events actually had no obvious geoeffectiveness, just 6% of them corresponding to small storms.     

Multi-Spacecraft Observations: Stream Interactions and Associated Structures

The stream interaction region (SIR), formed when a fast stream overtakes a preceding slow stream, is the predominant large-scale solar wind structure at this early phase of the STEREO mission. Using multi-spacecraft observations from STEREO A and B, ACE, Wind, and Ulysses in 2007, we analyze three stream interaction events in depth in May, August, and November of 2007, respectively, when the spacecraft had quite different spatial separations. We attempt to determine the causes of the differences in the SIR properties, whether they are spatial or temporal variations, and also to examine the steepening or widening of the SIR during its radial evolution. The presence and characteristics of associated shocks, the relation to the heliospheric current sheet, and other structures are also studied.     

Statistical Analysis of the Relationships among Coronal Holes,Corotating Interaction Regions,and Geomagnetic Storms

We have examined the relationships among coronal holes (CHs), corotating interaction regions (CIRs), and geomagnetic storms in the period 1996?–?2003. We have identified 123 CIRs with forward and reverse shock or wave features in ACE and Wind data and have linked them to coronal holes shown in National Solar Observatory/Kitt Peak (NSO/KP) daily He i 10?830 Å maps considering the Sun?–?Earth transit time of the solar wind with the observed wind speed. A sample of 107 CH?–?CIR pairs is thus identified. We have examined the magnetic polarity, location, and area of the CHs as well as their association with geomagnetic storms (Dst≤?50 nT). For all pairs, the magnetic polarity of the CHs is found to be consistent with the sunward (or earthward) direction of the interplanetary magnetic fields (IMFs), which confirms the linkage between the CHs and the CIRs in the sample. Our statistical analysis shows that (1) the mean longitude of the center of CHs is about 8°E, (2) 74% of the CHs are located between 30°S and 30°N (i.e., mostly in the equatorial regions), (3) 46% of the CIRs are associated with geomagnetic storms, (4) the area of geoeffective coronal holes is found to be larger than 0.12% of the solar hemisphere area, and (5) the maximum convective electric field E _y in the solar wind is much more highly correlated with the Dst index than any other solar or interplanetary parameter. In addition, we found that there is also a semiannual variation of CIR-associated geomagnetic storms and discovered new tendencies as follows: For negative-polarity coronal holes, the percentage (59%; 16 out of 27 events) of CIRs associated with geomagnetic storms in the first half of the year is much larger than that (25%; 6 out of 24 events) in the second half of the year and the occurrence percentage (63%; 15 out of 24 events) of CIR-associated storms in the southern hemisphere is significantly larger than that (26%; 7 out of 27 events) in the northern hemisphere. Positive-polarity coronal holes exhibit an opposite tendency.     

Spatial Distribution of Solar Energetic Particles in the Inner Heliosphere

We study the spatial distribution of solar energetic particles (SEPs) throughout the inner heliosphere during six large SEP events from the period 1977 through 1979, as deduced from observations on the Helios 1 and 2, IMP 7 and 8, ISEE 3, and Voyager 1 and 2 spacecraft. Evidence of intensity maxima associated with the expanding shock wave is commonly seen along its central and western flanks, although the region of peak acceleration or “nose” of the shock is sometimes highly localized in longitude. In one event (1 January 1978) a sharp peak in 20?–?30 MeV proton intensities is seen more strongly by Voyager at ～?2 AU than it is by spacecraft at nearby longitudes at ～?1 AU. Large spatial regions, or “reservoirs,” often exist behind the shocks with spatially uniform SEP intensities and invariant spectra that decrease adiabatically with time as their containment volume expands. Reservoirs are seen to sweep past 0.3 AU and can extend out many AU. Boundaries of the reservoirs can vary with time and with particle velocity, rather than rigidity. In one case, a second shock wave from the Sun reaccelerates protons that retain the same hard spectrum as protons in the reservoir from the preceding SEP event. Thus reservoirs can provide not only seed particles but also a “seed spectrum” with a spectral shape that is unchanged by a weaker second shock.     

The Whole Heliosphere Interval in the Context of a Long and Structured Solar Minimum: An Overview from Sun to Earth

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.     

The Bastille day Shocks and Merged Interaction Region

Near 1 AU the solar wind structure associated with the solar flare of 14 July 2000 (Bastille Day) consisted of a large high-speed stream of 15 July and five nearby small streams during a 10-day period. At the leading edge of the large high-speed stream, in less than 6 hours, the flow speed increased from 600 km s⁻¹ to 1100 km s⁻¹, the magnetic field intensity increased from 10 nT to 60 nT, and an interaction region was identified. The interaction region was bounded between the pair of a forward shock F and a reverse shock R. Additional forward shocks were also identified at the leading edge of each of the five smaller streams. This paper presents a magnetohydrodynamics (MHD) simulation using ACE plasma and magnetic field data near 1 AU as input to study the radial evolution of the Bastille Day solar wind event. The two shocks, F and R, propagated in opposite directions away from each other in the solar wind frame and interacted with neighboring shocks and streams; the spatial and temporal extent of the interaction region continued to increase with the heliocentric distance. The solar wind was restructured from a series of streams at 1 AU to a huge merged interaction region (MIR) extending over a period of 12 days at 5.5 AU. Throughout the interior of the MIR bounded by the shock pair F and R the magnetic field intensity was a few times stronger than that outside the MIR. The simulation shows how merging of shocks, collision of shocks, and formation of new shocks contributed to the evolution process.     

Energetic protons associated with a forward-reverse interplanetary shock pair at 1 A.U.

A forward-reverse interplanetary shock was observed on 25 March 1969 by the magnetometer and plasma detector on the HEOS-1 satellite. This relatively rare event was described by Chao et al (1972) who concluded that the shock pair was formed at a distance 0.10–0.13 A.U. upstream of the Earth as a result of the interaction between a fast and a slow solar wind streams. Simultaneous observations of 1 MeV solar proton fluxes were also performed on HEOS-1. A characteristic intensity peak was observed as the forward shock passed by the spacecraft. The evolution of the proton intensity, together with a detailed analysis of anisotropies and pitch angle distributions show a complex dynamic picture of the effect of the forward shock on the ambient proton population. Significant changes in particle fluxes are seen to be correlated with fluctuations in the magnetic field. It is suggested that simple geometrical models of shock-associated acceleration should be expanded to include the effect of magnetic fluctuations on particle fluxes. The interaction region limited by the forward and reverse shocks contained a large variety of magnetic fluctuations. Following the tangential discontinuity separating the fast solar wind stream from the preceding slow stream, a sunward flow was observed in the proton data, followed by a small but significant drop in intensity prior to the reverse shock.     

Ten cycles of solar and geomagnetic activity

Series of 110 years of sunspot numbers and indices of geomagnetic activity are used with 17 years of solar wind data in order to study through solar cycles both stream and shock event solar activity. According to their patterns on Bartels diagrams of geomagnetic indices, stable wind streams and transient solar activities are separated from each other. Two classes of stable streams are identified: equatorial streams occurring sporadically, for several months, during the main phase of sunspot cycles and both polar streams established, for several years, at each cycle, before sunspot minimum. Polar streams are the first activity of solar cycles. For study of the relationship between transient geomagnetic phenomena and sunspot activity, we raise the importance of the contribution, at high spot number, of severe storms and, at low spot number, of short lived and unstable streams. Solar wind data are used to check and complete the above results. As a conclusion, we suggest a unified scheme of solar activity evolution with a starting point every eleventh year, a total duration of 17 years and an overlapping of 6 years between the first and the last phase of both successive series of phenomena: first, from polar field reversal to sunspot minimum, a phase of polar wind activity of the beginning cycle is superimposed on the weak contribution of shock events of the ending cycle; secondly, an equatorial phase mostly of shock events is superimposed on a variable contribution of short lived and sporadic stable equatorial stream activities; and thirdly a phase of low latitude shock events is superimposed on the polar stream interval of the following cycle.     

High-Speed Solar Wind Streams and Geomagnetic Storms During Solar Cycle 24

An updated catalog is created of 303 well-defined high-speed solar wind streams that occurred in the time period 2009?–?2016. These streams are identified from solar and interplanetary measurements obtained from the OMNIWeb database as well as from the Solar and Heliospheric Observatory (SOHO) database. This time interval covers the deep minimum observed between the last two Solar Cycles 23 and 24, as well as the ascending, the maximum, and part of the descending phases of the current Solar Cycle 24. The main properties of solar-wind high-speed streams, such as their maximum velocity, their duration, and their possible sources are analyzed in detail. We discuss the relative importance of all those parameters of high-speed solar wind streams and especially of their sources in terms of the different phases of the current cycle. We carry out a comparison between the characteristic parameters of high-speed solar wind streams in the present solar cycle with those of previous solar cycles to understand the dependence of their long-term variation on the cycle phase. Moreover, the present study investigates the varied phenomenology related to the magnetic interactions between these streams and the Earth’s magnetosphere. These interactions can initiate geomagnetic disturbances resulting in geomagnetic storms at Earth that may have impact on technology and endanger human activity and health.     

Low energy ions in corotating interaction regions at 1 AU: Observations

The spacecraft ISEE-3 was launched in August 1978 and subsequently placed in orbit about the Sun-Earth L1 libration point where it continuously monitored the particles and fields in interplanetary space until mid-1982. The ISEE-3 Energetic Proton Anisotropy Spectrometer makes 3-dimensional intensity measurements of 35–1600 keV, Z ? 1 ions. This data is used in conjunction with simultaneous solar wind plasma and magnetic field data from the same spacecraft to study the properties of ions in interaction regions lying at the leading edges of nine corotating high speed solar wind streams observed during October 1978–July 1979. Seven streams have an enhancement of ? 300 keV ions in the compressed fast stream plasma between the stream interface and interaction region trailing edge. These enhancements are associated with plasma heating to above 3 × 10⁵ K, have soft spectra (spectral index ～ 4.5?6.0) and in five cases show anti-solar streaming in the solar wind frame.     

Impact of CIR Storms on Thermosphere Density Variability during the Solar Minimum of 2008

The solar minimum of 2008 was exceptionally quiet, with sunspot numbers at their lowest in 75 years. During this unique solar-minimum epoch, however, solar-wind high-speed streams emanating from near-equatorial coronal holes occurred frequently and were the primary contributor to the recurrent geomagnetic activity at Earth. These conditions enabled the isolation of forcing by geomagnetic activity on the preconditioned solar minimum state of the upper atmosphere caused by Corotating Interaction Regions (CIRs). Thermosphere density observations around 400 km from the CHAMP satellite are used to study the thermosphere density response to solar-wind high-speed streams/CIRs. Superposed epoch results show that the thermosphere density responds to high-speed streams globally, and the density at 400 km changes by 75% on average. The relative changes of neutral density are comparable at different latitudes, although its variability is largest at high latitudes. In addition, the response of thermosphere density to high-speed streams is larger at night than in daytime, indicating the preconditioning effect of the thermosphere response to storms. Finally, the thermosphere density variations at the periods of 9 and 13.5 days associated with CIRs are linked to the spatial distribution of low?–?middle latitude coronal holes on the basis of the EUVI observations from STEREO.     

In-situ Observations of a Co-rotating Interaction Region at Venus Identified by IPS and STEREO

This paper reports on the first combination of results from in-situ plasma measurements at Venus, using data from Venus Express, and remote sensing data from observations of interplanetary scintillation (IPS). In so doing, we demonstrate the value of combining remote sensing and in-situ techniques for the purpose of investigating interaction between solar wind, under several different conditions, and the Venusian magnetosphere. The ion mass analyser instrument (IMA) is used to investigate solar wind interaction with the Venusian magnetosphere in the presence of two different solar wind phenomena; a co-rotating interaction region (CIR) and a coronal mass ejection (CME). The CIR, detected with IPS and sampled in-situ at Venus is found to dramatically affect upstream solar wind conditions. These case studies demonstrate how combining results from these different data sources can be of considerable value when investigating such phenomena.