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Authors: Lavraud B., Fargette N., Réville V., Szabo A., Huang J., et al.
Title: The Heliospheric Current Sheet and Plasma Sheet during Parker Solar Probe’s First Orbit

We present heliospheric current sheet (HCS) and plasma sheet (HPS) observations during Parker Solar Probe’s (PSP) first orbit around the Sun. We focus on the eight intervals that display a true sector boundary (TSB; based on suprathermal electron pitch angle distributions) with one or several associated current sheets. The analysis shows that (1) the main density enhancements in the vicinity of the TSB and HCS are typically associated with electron strahl dropouts, implying magnetic disconnection from the Sun, (2) the density enhancements are just about twice that in the surrounding regions, suggesting mixing of plasmas from each side of the HCS, (3) the velocity changes at the main boundaries are either correlated or anticorrelated with magnetic field changes, consistent with magneti. . .
Date: 05/2020 Publisher: The Astrophysical Journal Pages: L19 DOI: 10.3847/2041-8213/ab8d2d Available at:
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Authors: Szabo Adam, Larson Davin, Whittlesey Phyllis, Stevens Michael L., Lavraud Benoit, et al.
Title: The Heliospheric Current Sheet in the Inner Heliosphere Observed by the Parker Solar Probe

The Parker Solar Probe (PSP) completed its first solar encounter in 2018 November, bringing it closer to the Sun than any previous mission. This allowed in situ investigation of the heliospheric current sheet (HCS) inside the orbit of Venus. The Parker observations reveal a well defined magnetic sector structure placing the spacecraft in a negative polarity region for most of the encounter. The observed current sheet crossings are compared to the predictions of both potential field source surface and magnetohydrodynamic models. All the model predictions are in good qualitative agreement with the observed crossings of the HCS. The models also generally agree that the HCS was nearly parallel with the solar equator during the inbound leg of the encounter and more significantly inclined dur. . .
Date: 02/2020 Publisher: The Astrophysical Journal Supplement Series Pages: 47 DOI: 10.3847/1538-4365/ab5dac Available at:
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Authors: Perrone D., D’Amicis R., De Marco R., Matteini L., Stansby D., et al.
Title: Highly Alfvénic slow solar wind at 0.3 au during a solar minimum: Helios insights for Parker Solar Probe and Solar Orbiter

Alfvénic fluctuations in solar wind are an intrinsic property of fast streams, while slow intervals typically have a very low degree of Alfvénicity, with much more variable parameters. However, sometimes a slow wind can be highly Alfvénic. Here we compare three different regimes of solar wind, in terms of Alfvénic content and spectral properties, during a minimum phase of the solar activity and at 0.3 au. We show that fast and Alfvénic slow intervals share some common characteristics. This would suggest a similar solar origin, with the latter coming from over-expanded magnetic field lines, in agreement with observations at 1 au and at the maximum of the solar cycle. Due to the Alfvénic nature of the fluctuations in both fast and Alfvénic slow winds, we observe a well-defined corr. . .
Date: 01/2020 Publisher: Astronomy & Astrophysics Pages: A166 DOI: 10.1051/0004-6361/201937064 Available at:
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Authors: Bale S. D., Badman S. T., Bonnell J. W., Bowen T. A., Burgess D., et al.
Title: Highly structured slow solar wind emerging from an equatorial coronal hole

During the solar minimum, when the Sun is at its least active, the solar wind is observed at high latitudes as a predominantly fast (more than 500 kilometres per second), highly Alfvénic rarefied stream of plasma originating from deep within coronal holes. Closer to the ecliptic plane, the solar wind is interspersed with a more variable slow wind of less than 500 kilometres per second. The precise origins of the slow wind streams are less certain; theories and observations suggest that they may originate at the tips of helmet streamers, from interchange reconnection near coronal hole boundaries, or within coronal holes with highly diverging magnetic fields. The heating mechanism required to drive the solar wind is also unresolved, although candidate mechanisms include Alfvé;n-wave tur. . .
Date: 12/2019 Publisher: Nature Pages: 237 - 242 DOI: 10.1038/s41586-019-1818-7 Available at:
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Authors: Stenborg Guillermo, and Howard Russell A.
Title: A Heuristic Approach to Remove the Background Intensity on White-light Solar Images. I. STEREO /HI-1 Heliospheric Images

White-light coronal and heliospheric imagers observe scattering of photospheric light from both dust particles (the F-Corona) and free electrons in the corona (the K-corona). The separation of the two coronae is thus vitally important to reveal the faint K-coronal structures (e.g., streamers, co-rotating interaction regions, coronal mass ejections, etc.). However, the separation of the two coronae is very difficult, so we are content in defining a background corona that contains the F- and as little K- as possible. For both the LASCO-C2 and LASCO-C3 coronagraphs aboard the Solar and Heliospheric Observatory (SOHO) and the white-light imagers of the SECCHI suite aboard the Solar Terrestrial Relationships Observatory (STEREO), a time-dependent model of the background corona is generated f. . .
Date: 04/2017 Publisher: The Astrophysical Journal Pages: 68 DOI: 10.3847/1538-4357/aa6a12 Available at:
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