The IMPACT Solar Wind Electron Analyzer (SWEA)

Sauvaud, J. A.; Larson, D. E.; Aoustin, C.; Curtis, D. W.; Médale, J. L.; Fedorov, A.; Rouzaud, Jean-Noël; Luhmann, J. G.; Moreau, Thibault; Schröder, Philipp; Dandouras, I.; Penou, E.

doi:10.1007/978-0-387-09649-0_9

Cited by 36 publications

(37 citation statements)

References 20 publications

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“…We found that alpha number density (in red) shows little if any depletion in the HPS compared to the adjacent regions, so the change in the alpha to proton density ratio is attributed primarily to the increase in protons. All three spacecraft (ST-A, ST-B, and ACE) observed a modest increase in the density of iron ions (green traces) coincident with the HPS, consistent with observations presented by Schmid, Bochsler, and Geiss (1988). CR 2054, 2055, and 2057 were free of transients, so we do not attribute the increase in iron density to remnants of ICMEs.…”

Section: Summary and Discussionsupporting

confidence: 87%

“…Separation in heliographic latitude, though small, is the most likely explanation for the disparities between observation points. Lastly, in the absence of ICME material we observed a modest enhancement in the density of iron ions with each crossing of the HPS, similar to the observations of Schmid, Bochsler, and Geiss (1988). This supports the conclusion of Wimmer-Schweingruber (1994) that gravitational stratification at the solar source region is not responsible for the well-observed N a /N p de-(c) Figure 12 (Continued.…”

Section: (B)supporting

confidence: 86%

“…STEREO magnetic field data are from the Magnetic Field Experiment (MAG, Acuña et al, 2008). Electron pitch angle distributions (PADs) are from the Solar Wind Electron Analyzer (SWEA, Sauvaud et al, 2008). MAG and SWEA are both part of the In-Situ Measurements of Particles and CME Transients (IMPACT) suite .…”

Section: Datamentioning

confidence: 99%

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The Heliospheric Plasma Sheet Observed in situ by Three Spacecraft over Four Solar Rotations

et al. 2012

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In this paper we present in situ observations of the heliospheric plasma sheet (HPS) from STEREO-A, Wind, and STEREO-B over four solar rotations in the declining phase of Solar Cycle 23, covering late March through late June 2007. During this time period the three spacecraft were located in the ecliptic plane, and were gradually separating in heliographic longitude from about 3 degrees to 14 degrees. Crossings of the HPS were identified using the following criteria: reversal of the interplanetary magnetic field sector, enhanced proton density, and local minima in both the proton specific entropy argument and in the alpha particle-to-proton number density ratio (N a /N p ). Two interplanetary coronal mass ejections (ICMEs) were observed during the third solar rotation of our study period, which disrupted the HPS from its quasi-stationary state. We find differences in the in situ proton parameters at the HPS between the three spacecraft despite temporal separations of less than one day. We attribute these differences to both small separations in heliographic latitude and radial evolution of the solar wind leading to the development of compression The Sun 360 Guest Editors: Bernhard Fleck, Bernd Heber, and Angelos Vourlidas regions associated with stream interaction regions (SIRs). We also observed a modest enhancement in the density of iron ions at the HPS.

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Section: Summary and Discussionsupporting

confidence: 87%

Section: (B)supporting

confidence: 86%

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The Heliospheric Plasma Sheet Observed in situ by Three Spacecraft over Four Solar Rotations

et al. 2012

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“…Instruments [7] In addition to the SECCHI imaging suite described in paper 1, each of the STEREO spacecraft also carries a comprehensive suite of in situ instrumentation, including the Plasma and Suprathermal Ion Composition (PLASTIC) [Galvin et al, 2008] and the In Situ Measurements of Particles and CME Transients (IMPACT) packages. Magnetic field measurements from the magnetometer (MAG) [Acuña et al, 2008] and suprathermal electron observations from the Solar Wind Electron Analyzer (SWEA) [Sauvaud et al, 2008], two components of the IMPACT package, are used in the present study together with the solar wind ion moments derived from measurements made by the PLASTIC package. In situ measurements of near-Earth solar wind electron and ion as well as suprathermal electrons made by the Solar Wind Electron, Proton, Alpha Monitor investigation (SWEPAM) [McComas et al, 1998], solar wind composition measured by the Solar Wind Ion Composition Spectrometer and the Solar Wind Ion Mass Spectrometer (SWICS/SWIS) [Gloeckler et al, 1998] and measurements of the magnetic field by the magnetic field investigation (MAG) [Smith et al, 1998] on board the Advanced Composition Explorer (ACE) are also used in the present paper.…”

Section: Introductionmentioning

confidence: 99%

Intermittent release of transients in the slow solar wind: 2. In situ evidence

et al. 2010

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[1] In paper 1, we showed that the Heliospheric Imager (HI) instruments on the pair of NASA STEREO spacecraft can be used to image the streamer belt and, in particular, the variability of the slow solar wind which originates near helmet streamers. The observation of intense intermittent transient outflow by HI implies that the corresponding in situ observations of the slow solar wind and corotating interaction regions (CIRs) should contain many signatures of transients. In the present paper, we compare the HI observations with in situ measurements from the STEREO and ACE spacecraft. Analysis of the solar wind ion, magnetic field, and suprathermal electron flux measurements from the STEREO spacecraft reveals the presence of both closed and partially disconnected interplanetary magnetic field lines permeating the slow solar wind. We predict that one of the transients embedded within the second CIR (CIR-D in paper 1) should impact the near-Earth ACE spacecraft. ACE measurements confirm the presence of a transient at the time of CIR passage; the transient signature includes helical magnetic fields and bidirectional suprathermal electrons. On the same day, a strahl electron dropout is observed at STEREO-B, correlated with the passage of a high-plasma beta structure. Unlike ACE, STEREO-B observes the transient a few hours ahead of the CIR. STEREO-A, STEREO-B, and ACE spacecraft observe very different slow solar wind properties ahead of and during the CIR analyzed in this paper, which we associate with the intermittent release of transients.

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“…ACE and Wind thus measured very similar solar wind conditions and in this work we will use primarily Wind measurements to describe the conditions at L1. Our data sets come from the magnetometers, plasma analyzers (PLASTIC) and solar wind electron analyzers (SWEA) on STEREO described in Acuna et al (2008), Galvin et al (2008), and Sauvaud et al (2008), respectively, the magnetometer and 3D plasma analyzer (3DP) on Wind (Lepping et al, 1995;Lin et al, 1995), and the plasma analyzer (SWEPAM) and plasma spectrometer (SWICS) on ACE.…”

Section: Introductionmentioning

confidence: 99%

Small Solar Wind Transients and Their Connection to the Large-Scale Coronal Structure

et al. 2009

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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.

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The IMPACT Solar Wind Electron Analyzer (SWEA)

Cited by 36 publications

References 20 publications

The Heliospheric Plasma Sheet Observed in situ by Three Spacecraft over Four Solar Rotations

The Heliospheric Plasma Sheet Observed in situ by Three Spacecraft over Four Solar Rotations

Intermittent release of transients in the slow solar wind: 2. In situ evidence

Small Solar Wind Transients and Their Connection to the Large-Scale Coronal Structure

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