Sub-Alfvénic Solar Wind Observed by the Parker Solar Probe: Characterization of Turbulence, Anisotropy, Intermittency, and Switchback

  title={Sub-Alfv{\'e}nic Solar Wind Observed by the Parker Solar Probe: Characterization of Turbulence, Anisotropy, Intermittency, and Switchback},
  author={Riddhi Bandyopadhyay and William H. Matthaeus and D. J. Mccomas and Rohit Chhiber and Arcadi V. Usmanov and J. Huang and Roberto Livi and Davin E. Larson and Justin C. Kasper and A. W. Case and Michael Stevens and Phyllis L. Whittlesey and O. M. Romeo and Stuart. D. Bale and John W. Bonnell and Thierry Dudok de Wit and Keith Goetz and Peter R. Harvey and Robert J. Macdowall and David M. Malaspina and Marc P. Pulupa},
  journal={The Astrophysical Journal Letters},
In the lower solar coronal regions where the magnetic field is dominant, the Alfvén speed is much higher than the wind speed. In contrast, the near-Earth solar wind is strongly super-Alfvénic, i.e., the wind speed greatly exceeds the Alfvén speed. The transition between these regimes is classically described as the “Alfvén point” but may in fact occur in a distributed Alfvén critical region. NASA’s Parker Solar Probe (PSP) mission has entered this region, as it follows a series of orbits that… 

The Turbulent Properties of the Sub-Alfvénic Solar Wind Measured by the Parker Solar Probe

For the first time, Parker Solar Probe (PSP) observed the sub-Alfvénic solar wind where the solar wind bulk speed drops below the local Alfvén speed for an extended period of time. Here, we report on

Turbulence and Waves in the Sub-Alfvénic Solar Wind Observed by the Parker Solar Probe during Encounter 10

During its 10th orbit around the Sun, the Parker Solar Probe sampled two intervals where the local Alfvén speed exceeded the solar wind speed, lasting more than 10 hours in total. In this paper, we

Observations of Cross Scale Energy Transfer in the Inner Heliosphere by Parker Solar Probe

The solar wind, a continuous flow of plasma from the sun, not only shapes the near Earth space environment but also serves as a natural laboratory to study plasma turbulence in conditions that are not

Magnetic Field Intermittency in the Solar Wind: Parker Solar Probe and SolO Observations Ranging from the Alfvén Region up to 1 AU

Parker Solar Probe (PSP) and SolO data are utilized to investigate magnetic field intermittency in the solar wind (SW). Small-scale intermittency (20−100 d i ) is observed to radially strengthen when

Isotropization and Evolution of Energy-containing Eddies in Solar Wind Turbulence: Parker Solar Probe, Helios 1, ACE, WIND, and Voyager 1

We examine the radial evolution of correlation lengths perpendicular ( λC⊥ ) and parallel ( λC∥ ) to the magnetic-field direction, computed from solar wind magnetic-field data measured by Parker



Alfvénic velocity spikes and rotational flows in the near-Sun solar wind

Observations of solar-wind plasma at heliocentric distances of about 35 solar radii reveal an increasing rotational component to the flow velocity of the solar wind around the Sun, peaking at 35 to 50 kilometres per second—considerably above the amplitude of the waves.

Some Turbulent Predictions for Parker Solar Probe

From the the solar photosphere to the outer heliosphere, the Sun's plasma properties are fluctuating with a broad range of temporal and spatial scales. In fact, a turbulent cascade of energy from

Highly structured slow solar wind emerging from an equatorial coronal hole

Measurements from the Parker Solar Probe show that slow solar wind near the Sun’s equator originates in coronal holes, and plasma-wave measurements suggest the existence of electron and ion velocity-space micro-instabilities that are associated with plasma heating and thermalization processes.

Strong Preferential Ion Heating is Limited to within the Solar Alfvén Surface

The decay of the solar wind helium-to-hydrogen temperature ratio due to Coulomb thermalization can be used to measure how far from the Sun strong preferential ion heating occurs. Previous work has

The Properties of the Solar Corona and Its Connection to the Solar Wind

The corona is a layer of hot plasma that surrounds the Sun, traces out its complex magnetic field, and ultimately expands into interplanetary space as the supersonic solar wind. Although much has

Probing the Energetic Particle Environment near the Sun

Observations of the near-Sun energetic particle radiation environment over the first two orbits of the Parker Solar Probe find a variety of energetic particle events accelerated both locally and remotely including by corotating interaction regions, impulsive events driven by acceleration near the Sun, and an event related to a coronal mass ejection.

Contextual Predictions for the Parker Solar Probe. I. Critical Surfaces and Regions

The solar corona and young solar wind may be characterized by critical surfaces—the sonic, Alfvén, and first plasma-β unity surfaces—that demarcate regions where the solar wind flow undergoes certain

Switchbacks in the Near-Sun Magnetic Field: Long Memory and Impact on the Turbulence Cascade

One of the most striking observations made by Parker Solar Probe during its first solar encounter is the omnipresence of rapid polarity reversals in a magnetic field that is otherwise mostly radial.

Observations of Energetic-particle Population Enhancements along Intermittent Structures near the Sun from the Parker Solar Probe

Observations at 1 au have confirmed that enhancements in measured energetic-particle (EP) fluxes are statistically associated with “rough” magnetic fields, i.e., fields with atypically large spatial

Impact of Switchbacks on Turbulent Cascade and Energy Transfer Rate in the Inner Heliosphere

Recent Parker Solar Probe (PSP) observations of inner heliospheric plasma have shown an abundant presence of Alfvénic polarity reversal of the magnetic field, known as “switchbacks.” While their