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2020
Authors: McManus Michael D., Bowen Trevor A., Mallet Alfred, Chen Christopher H. K., Chandran Benjamin D. G., et al.
Title: Cross Helicity Reversals in Magnetic Switchbacks
Abstract:

We consider 2D joint distributions of normalized residual energy, σr(s, t), and cross helicity, σc(s, t), during one day of Parker Solar Probe's (PSP's) first encounter as a function of wavelet scale s. The broad features of the distributions are similar to previous observations made by Helios in slow solar wind, namely well-correlated and fairly Alfvénic wind, except for a population with negative cross helicity that is seen at shorter wavelet scales. We show that this population is due to the presence of magnetic switchbacks, or brief periods where the magnetic field polarity reverses. Such switchbacks have been observed before, both in Helios data and in Ulysses data in the polar solar wind. Their abundance and short timescales as seen by PSP in its first enc. . .
Date: 02/2020 Publisher: The Astrophysical Journal Supplement Series Pages: 67 DOI: 10.3847/1538-4365/ab6dce Available at: https://iopscience.iop.org/article/10.3847/1538-4365
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Authors: Bowen Trevor A., Mallet Alfred, Huang Jia, Klein Kristopher G., Malaspina David M., et al.
Title: Ion-scale Electromagnetic Waves in the Inner Heliosphere
Abstract:

Understanding the physical processes in the solar wind and corona that actively contribute to heating, acceleration, and dissipation is a primary objective of NASA's Parker Solar Probe (PSP) mission. Observations of circularly polarized electromagnetic waves at ion scales suggest that cyclotron resonance and wave─particle interactions are dynamically relevant in the inner heliosphere. A wavelet-based statistical study of circularly polarized events in the first perihelion encounter of PSP demonstrates that transverse electromagnetic waves at ion resonant scales are observed in 30─50% of radial field intervals. Average wave amplitudes of approximately 4 nT are measured, while the mean duration of wave events is on the order of 20 s; however, long-duration wave events can exist withou. . .
Date: 02/2020 Publisher: The Astrophysical Journal Supplement Series Pages: 66 DOI: 10.3847/1538-4365/ab6c65 Available at: https://iopscience.iop.org/article/10.3847/1538-4365/
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