The High Energy Telescope for STEREO

Rosenvinge, T. T. von; Reames, D. V.; Baker, R.; Hawk, J.; Nolan, Jackson; Ryan, L.; Shuman, S.; Wortman, Kristin; Mewaldt, R. A.; Cummings, A. C.; Cook, W. R.; Labrador, A. W.; Leske, R. A.; Wiedenbeck, M. E.

doi:10.1007/s11214-007-9300-5

Cited by 114 publications

(47 citation statements)

References 9 publications

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“…The fact that the particles appear to have traveled to the Earth via the eastern "leg" of the magnetic cloud may also have influenced the path length and connectivity. Thus, although we might expect the smooth fields and large particle mean free paths in magnetic clouds (e.g., Tranquille et al, 1987) to provide easy access for energetic particles to 1 AU, especially when the magnetic cloud and the particle event originate in the same active region, this is apparently not always the case. Without observations of the SEP event from a near-Earth spacecraft outside the magnetic cloud, it is difficult to assess the impact of the magnetic cloud on the peak particle intensity.…”

Section: Summary and Discussionmentioning

confidence: 99%

The Solar Energetic Particle Event of 14 December 2006

et al. 2009

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ations in the particle intensity that occurred during the first few hours. These fluctuations were observed inside a magnetic cloud that originated in a solar event on 13 December and show both similarities and variations at the different spacecraft. Interestingly, the most striking difference is between observations at the two closely-separated STEREO spacecraft. In particular, large fluctuations in the proton intensity were seen by the High Energy Telescope (HET) on STEREO A, and to a lesser extent at Wind and ACE, but not by the STEREO B HET. We conclude that the differences in intensity-time profiles were caused by anisotropies in the particle distribution and the different viewing directions of the individual particle telescopes. The intensity/anisotropy variations suggest that flux tubes with different particle propagation conditions existed within this magnetic cloud despite the absence of local magnetic field signatures associated with these regions. The intensity fluctuations are similar to those occasionally seen in impulsive particle events. There were also spacecraftto-spacecraft differences during the onset of the particle event. An initial rapid onset of energetic (> 40 MeV) protons was observed by the STEREO A and B spacecraft outside the magnetic cloud, but not by spacecraft such as SOHO that were already inside the magnetic cloud at this time. The latter spacecraft observed a slower, lower intensity increase. Evidently, energetic proton propagation from the solar event to the vicinity of Earth was inhibited within the magnetic cloud compared to outside.

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Section: Summary and Discussionmentioning

confidence: 99%

The Solar Energetic Particle Event of 14 December 2006

et al. 2009

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“…25-10.4 MeV (Müller-Mellin et al 1995). In addition, we use measurements from High Energy Telescope (HET; von Rosenvinge et al 2008), Plasma and Suprathermal Ion Composition (PLASTIC) solar wind data (Galvin et al 2008), the STEREO radio and plasma Wave (SWAVES) radio emission spectra (Bougeret et al 2008), Extrem Ultra Violet Imager (EUVI; Howard et al 2008), and Magnetometer (MAG) data (Acuña et al 2008) from the two STEREO s/c.…”

Section: Instrumentationmentioning

confidence: 99%

Unexpected spatial intensity distributions and onset timing of solar electron events observed by closely spaced STEREO spacecraft

Klassen

Dresing

Gómez-Herrero

et al. 2016

A&A

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We present multi-spacecraft observations of four solar electron events using measurements from the Solar Electron Proton Telescope (SEPT) and the Electron Proton Helium INstrument (EPHIN) on board the STEREO and SOHO spacecraft, respectively, occurring between 11 October 2013 and 1 August 2014, during the approaching superior conjunction period of the two STEREO spacecraft. At this time the longitudinal separation angle between STEREO-A (STA) and STEREO-B (STB) was less than 72• . The parent particle sources (flares) of the four investigated events were situated close to, in between, or to the west of the STEREO's magnetic footpoints. The STEREO measurements revealed a strong difference in electron peak intensities (factor ≤12) showing unexpected intensity distributions at 1 AU, although the two spacecraft had nominally nearly the same angular magnetic footpoint separation from the flaring active region (AR) or their magnetic footpoints were both situated eastwards from the parent particle source. Furthermore, the events detected by the two STEREO imply a strongly unexpected onset timing with respect to each other: the spacecraft magnetically best connected to the flare detected a later arrival of electrons than the other one. This leads us to suggest the concept of a rippled peak intensity distribution at 1 AU formed by narrow peaks (fingers) superposed on a quasi-uniform Gaussian distribution. Additionally, two of the four investigated solar energetic particle (SEP) events show a so-called circumsolar distribution and their characteristics make it plausible to suggest a two-component particle injection scenario forming an unusual, non-uniform intensity distribution at 1 AU.

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“…This earlier flare was western as viewed by STEREO-B and it is clear from the ~1 MeV electrons and >10 MeV protons intensities from the High Energy Telescope (HET [von Rosenvinge, et al 2008]; not shown) that this event did produce particles. However, the protons intensities from this event were decaying when a second, stronger increase due to the later solar activity occurred (both events were also distinctly observed in electrons).…”

Section: Discussionmentioning

confidence: 95%

Investigating the longitude dependence of solar energetic particle spectra

Cohen

Mason

Mewaldt

et al. 2012

AIP Conference Proceedings

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Wave associated anomalous drag during magnetic field reconnection Phys. Plasmas 18, 102902 (2011) The effect of spectral anisotropy of fast magnetosonic turbulence on the plasma heating at the proton kinetic scales Phys. Plasmas 17, 112902 (2010) Abstract. We examine the traits of six solar energetic particle events observed simultaneously by instruments on ACE and at least one of the twin STEREO spacecraft. We compare the time profiles and spectra of energetic oxygen as a function of the longitudinal separation of the observer from the solar source region. We find systematic trends in the rise and peak times with source longitude that are consistent with those determined from single spacecraft studies. However, we also find two events where the rise times were surprisingly rapid when the source region was over the western limb relative to the observer. This has potential consequences for space weather predictions of radiation hazards. No clear trend is apparent for hardness of the event-integrated spectra with source longitude contrary to trends seen in the single spacecraft studies.

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The High Energy Telescope for STEREO

Cited by 114 publications

References 9 publications

The Solar Energetic Particle Event of 14 December 2006

The Solar Energetic Particle Event of 14 December 2006

Unexpected spatial intensity distributions and onset timing of solar electron events observed by closely spaced STEREO spacecraft

Investigating the longitude dependence of solar energetic particle spectra

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