LOCALIZED PLASMA DENSITY ENHANCEMENTS OBSERVED IN<i>STEREO</i>COR1

Jones, S. I.; Davila, J. M.

doi:10.1088/0004-637x/701/2/1906

Cited by 18 publications

(14 citation statements)

References 16 publications

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“…Hundhausen 1977;Gosling et al 1981;McComas et al 1998; and the recent review by Abbo et al 2016). However, the speed around 300 km s −1 that we found is higher than the slow wind speeds reported on the basis of measurements of blobs by Sheeley et al (1997); Wang et al (2000b); Sheeley & Wang (2007); and Jones & Davila (2009). This is probably due to the transient increase of the solar wind speed in streamers after the passage of the CME-driven shock.…”

Section: Statistical Analysis Of the Streamer Wave Eventscontrasting

confidence: 87%

Properties of Streamer Wave Events Observed during the STEREO Era

Decraemer

Zhukov

Doorsselaere

2020

ApJ

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Transverse waves are sometimes observed in solar helmet streamers, typically after the passage of a coronal mass ejection (CME). The CME-driven shock wave moves the streamer sideways, and a decaying oscillation of the streamer is observed after the CME passage. Previous works generally reported observations of streamer oscillations taken from a single vantage point (typically the SOHO spacecraft). We conduct a data survey searching for streamer wave events observed by the COR2 coronagraphs onboard the STEREO spacecraft. For the first time, we report observations of streamer wave events from multiple vantage points, by using the COR2 instrument on both STEREO A and B, as well as the SOHO/LASCO C2+C3 coronagraphs. We investigate the properties of streamer waves by comparing the different events and performing a statistical analysis. Common observational features give us additional insight on the physical nature of streamer wave events. The most important conclusion is that there appears to be no relation between the speed of the CME and the phase speed of the resulting streamer wave, indicating that the streamer wave speed is determined by the physical properties of the streamer rather than the properties of the CME. This result makes streamer waves events excellent candidates for coronal seismology studies. From a comparison between the measured phase speeds and the phase speeds calculated from the measured periods and wavelengths, we could determine that the speed of the post-shock solar wind flow in our streamers is around 300 km s −1 .

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Section: Statistical Analysis Of the Streamer Wave Eventscontrasting

confidence: 87%

Properties of Streamer Wave Events Observed during the STEREO Era

Decraemer

Zhukov

Doorsselaere

2020

ApJ

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“…In the interpretation of Sheeley et al (1997), the velocity profile of the blobs (which resembles that of slow streamer blowouts) reflects that of the surrounding SSW. Using the STEREO/COR1 coronagraph, Jones and Davila (2009) have also detected and measured the speeds of small density enhancements inside r ∼ 2 R ⊙ ; however, many of the features that they tracked are likely to have been associated with CME eruptions rather than streamer blobs.…”

Section: Some Results From Soho/uvcs Instrumentmentioning

confidence: 99%

Slow Solar Wind: Observations and Modeling

et al. 2016

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While it is certain that the fast solar wind originates from coronal holes, where and how the slow solar wind (SSW) is formed remains an outstanding question in solar physics even in the post-SOHO era. The quest for the SSW origin forms a major objective for the planned future missions such as the Solar Orbiter and Solar Probe Plus. Nonetheless, results from spacecraft data, combined with theoretical modeling, have helped to investigate many aspects of the SSW. Fundamental physical properties of the coronal plasma have been derived from spectroscopic and imaging remote-sensing data and in situ data, and these results have provided crucial insights for a deeper understanding of the origin and acceleration of the SSW. Advanced models of the SSW in coronal streamers and other structures have been developed using 3D MHD and multi-fluid equations. However, the following questions remain open: What are the source regions and their contributions to the SSW? What is the role of the magnetic topology in the corona for the origin, acceleration and energy deposition of the SSW? What are the possible acceleration and heating mechanisms for the SSW? The aim of this review is to present insights on the SSW origin and formation gathered from the discussions at the International Space Science Institute (ISSI) by the Team entitled "Slow solar wind sources and acceleration mechanisms in the corona" held in Bern (Switzerland) in March 2014 and 2015.

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“…Using n e ~ 4 × 10 12 m −3 , and solar wind speed V SW for this heliocentric offset as 50 km s −1 [ Imamura et al ., ; Jones and Davila , ], the estimated F SW in the equatorial quiescent Sun is 0.4 W m −2 . If we were to include this value for the solar wind flow speed in equation by replacing V A with V A + V SW and also by including the convection of wave kinetic energy [e.g., Hollweg , , equation (17)], we would obtain an increase of the wave energy flux density of about 20%.…”

Section: Discussionmentioning

confidence: 99%

Faraday rotation fluctuations of MESSENGER radio signals through the equatorial lower corona near solar minimum

et al. 2017

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Faraday rotation (FR) of transcoronal radio transmissions from spacecraft near superior conjunction enables study of the temporal variations in coronal plasma density, velocity, and magnetic field. The MESSENGER spacecraft 8.4 GHz radio, transmitting through the corona with closest line‐of‐sight approach 1.63–1.89 solar radii and near‐equatorial heliolatitudes, was recorded soon after the deep solar minimum of solar cycle 23. During egress from superior conjunction, FR gradually decreased, and an overlay of wave‐like FR fluctuations (FRFs) with periods of hundreds to thousands of seconds was found. The FRF power spectrum was characterized by a power law relation, with the baseline spectral index being −2.64. A transient power increase showed relative flattening of the spectrum and bands of enhanced spectral power at 3.3 mHz and 6.1 mHz. Our results confirm the presence of coronal FRF similar to those described previously at greater solar offset. Interpreted as Alfvén waves crossing the line of sight radially near the proximate point, low‐frequency FRF convey an energy flux density higher than that of the background solar wind kinetic energy, but only a fraction of that required to accelerate the solar wind. Even so, this fraction is quite variable and potentially escalates to energetically significant values with relatively modest changes in estimated magnetic field strength and electron concentration. Given the uncertainties in these key parameters, as well as in solar wind properties close to the Sun at low heliolatitudes, we cannot yet confidently assign the quantitative role for Alfvén wave energy from this region in driving the slow solar wind.

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LOCALIZED PLASMA DENSITY ENHANCEMENTS OBSERVED INSTEREOCOR1

Cited by 18 publications

References 16 publications

Properties of Streamer Wave Events Observed during the STEREO Era

Properties of Streamer Wave Events Observed during the STEREO Era

Slow Solar Wind: Observations and Modeling

Faraday rotation fluctuations of MESSENGER radio signals through the equatorial lower corona near solar minimum

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