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

Mason, G. M.; Desai, M. I.; Korth, A.; Bučík, R.; Rosenvinge, T. T. von; Simunac, K. D. C.

doi:10.1007/s11207-009-9367-0

Cited by 39 publications

(57 citation statements)

References 30 publications

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“…Considering the rotation rate of the Sun, and the longitudinal separation between the spacecraft, this means that there is variability on the time scale of 1.5 -2 days. CIR observations at different spacecraft have been compared by Mason et al (2009) and more specifically in reference to STEREO observations (Leske et al, 2008) and Wind observations (Sanderson et al, 1998). These authors also noted that features present in in-situ data from one spacecraft are not always observed when one would expect at another spacecraft with an angular separation, as noticed here.…”

Section: Cir Periodicity and Predicted Arrival Timesmentioning

confidence: 62%

“…There are, of course, some factors to keep in mind when considering these results. From the observations presented in the previous sections, it is apparent that during the period under study, solar-wind source regions on the solar surface can last for multiple solarrotation periods; however, a given source does not eject material with constant properties on time scales of even a few days, in agreement with Mason et al (2009). This suggests possible sources of error in solar-wind analysis techniques that assume a constant propagation speed over the entire CIR.…”

Section: Discussionmentioning

confidence: 81%

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Corotating Interaction Regions as Seen by the STEREO Heliospheric Imagers 2007 – 2010

et al. 2015

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NASA's Solar Terrestrial Relations Observatory (STEREO) mission has coincided with a pronounced solar minimum. This allowed for easier detection of corotating interaction regions (CIRs). CIRs are formed by the interaction between fast and slow solarwind streams ejected from source regions on the solar surface that rotate with the Sun. High-density plasma blobs that have become entrained at the stream interface can be tracked out to large elongations in data from the Heliospheric Imager (HI) instruments onboard STEREO. These blobs act as tracers of the CIR itself such that their HI signatures can be used to estimate CIR source location and radial speed. We estimate the kinematic properties of solar-wind transients associated with 40 CIRs detected by the HI instrument onboard the STEREO-A spacecraft between 2007 and 2010. We identify in-situ signatures of these transients at L1 using the Advanced Composition Explorer (ACE) and compare the in-situ parameters with the HI results. We note that solar-wind transients associated with CIRs appear to travel at or close to the slow solar-wind speed preceding the event as measured in situ. We also highlight limitations in the commonly used analysis techniques of solar-wind transients by considering variability in the solar wind.

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Section: Cir Periodicity and Predicted Arrival Timesmentioning

confidence: 62%

Section: Discussionmentioning

confidence: 81%

Corotating Interaction Regions as Seen by the STEREO Heliospheric Imagers 2007 – 2010

et al. 2015

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“…Kirk et al (2009) stated that the north and south polar-hole areas were reduced by ≈ 15 % in 2007 compared with 1996. Mason et al (2009) found that during the recent Minimum 23/24 in comparison with the previous one (22/23) there were many more co-rotating interaction regions observed, connected with the existence of more high-speed streams of solar wind. Moreover, a low solar-wind dynamic pressure, ≈ 40 % in comparison with the previous minimum, was observed (Mewaldt et al, 2010) and this was caused by the drop in the average proton density, which was ≈ 5.5 cm −3 , being less dense in comparison with the previous three minima by ≈ 70 % (Jian, Russell, and Luhmann, 2011).…”

Section: Introductionmentioning

confidence: 71%

Energy Spectrum of the Recurrent Variation of Galactic Cosmic Rays During the Solar Minimum of Cycles 23/24

Gil

Alania

2016

Sol Phys

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The Sun during the recent epoch of solar activity operated in a different way than during the last 60 years, being less active. We study temporal changes of the energy spectrum of the first three harmonics of the 27-day variation of the galactic cosmic rays (GCR) intensity during the unusual, recent solar minimum, between Solar Cycles 23 and 24 (SC 23/24) and compare with four previous minima. We show that the energy spectrum of the amplitudes of the recurrent variation of the GCR intensity is hard in the maximum epochs and is soft in the minimum epochs during Solar Cycles 20 -24, but with peculiarities during the Solar Minimum 23/24. In particular, while the energy/rigidity spectrum of the amplitudes of the first harmonic of the recurrent variation of the GCR intensity behaves practically the same as for previous epochs, the energy/rigidity spectrum of the amplitudes of the second and the third harmonics demonstrates a pronounced softening. We attribute this phenomenon to the decrease of the extension of the heliosphere caused by the decrease of the solar-wind dynamic pressure during the unusual Solar Minimum 23/24.

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“…Other effects may be important including the merging of CIRs in the outer heliosphere, the latitudinal extent of the CIR shocks (Richardson et al, 1993), and the connection to the CIR (Mason et al, 2009). The tendency for the higher peak intensities associated with the recurrent CIRs was seen in a survey by Mason et al (2008a) and Richardson et al (1993).…”

Section: Cir2 Eventmentioning

confidence: 97%

“…wind plasma and magnetic field parameters measured by the PLASTIC instrument and the magnetometer sensor. Both of those events are included in the survey of Mason et al (2009).…”

Section: Observationsmentioning

confidence: 99%

STEREO Observations of Energetic Ions in Corotating Interaction Regions During the May 2007 Solar Events

et al. 2009

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Elemental composition and energy spectra of ∼ 0.1 -1.0 MeV/n heavy ions were analyzed in two corotating interaction region (CIR) events starting on 18 May (CIR1), and 24 May (CIR2), 2007, that occurred during two weak solar energetic particle (SEP) events. The data were taken by the Suprathermal Ion Telescope (SIT) instruments onboard STEREO-A and B. The ion intensity increases related to the CIR2 were much more pronounced compared to those associated with the CIR1, although the total pressure, the magnetic field magnitude and the speed difference between high and slow solar wind were less enhanced. We found that the ratio of CIR2 to CIR1 helium fluence decreases with energy as a power -law below ∼ 1 MeV/n. The energy spectra of hydrogen and helium inside the CIR2 region are much softer compared to the spectra observed in the CIR1 region. Based on these findings, we argue that the larger intensities in the CIR2 event could be due to an additional source population. The elemental abundances in CIR2 and the high-speed stream of the CIR1 region have a SEP-like composition. The energy spectra of hydrogen and helium inside the CIR2 were close to the preceding SEP event spectra. The similarity in the elemental abundances and in the spectral slopes suggests that the seed population of CIR2 are ions from the preceding SEP event. For the CIR1 event the ions seem to be contaminated by SEPs.

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

Cited by 39 publications

References 30 publications

Corotating Interaction Regions as Seen by the STEREO Heliospheric Imagers 2007 – 2010

Corotating Interaction Regions as Seen by the STEREO Heliospheric Imagers 2007 – 2010

Energy Spectrum of the Recurrent Variation of Galactic Cosmic Rays During the Solar Minimum of Cycles 23/24

STEREO Observations of Energetic Ions in Corotating Interaction Regions During the May 2007 Solar Events

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