Found 6 results
Author Title Type [ Year(Asc)]
Filters: Author is Parashar, T. N.  [Clear All Filters]
2020
Authors: Chhiber Rohit, Goldstein M L., Maruca B. A., Chasapis A., Matthaeus W. H., et al.
Title: Clustering of Intermittent Magnetic and Flow Structures near Parker Solar Probe ’s First Perihelion—A Partial-variance-of-increments Analysis
Abstract:

During the Parker Solar Probe's (PSP) first perihelion pass, the spacecraft reached within a heliocentric distance of ̃37 R and observed numerous magnetic and flow structures characterized by sharp gradients. To better understand these intermittent structures in the young solar wind, an important property to examine is their degree of correlation in time and space. To this end, we use the well-tested partial variance of increments (PVI) technique to identify intermittent events in FIELDS and SWEAP observations of magnetic and proton-velocity fields (respectively) during PSP's first solar encounter, when the spacecraft was within 0.25 au from the Sun. We then examine distributions of waiting times (WT) between events with varying separation and PVI thresholds. We find powe. . .
Date: 02/2020 Publisher: The Astrophysical Journal Supplement Series Pages: 31 DOI: 10.3847/1538-4365/ab53d2 Available at: https://iopscience.iop.org/article/10.3847/1538-4365/ab53d2
More Details

Authors: Bandyopadhyay Riddhi, Goldstein M. L., Maruca B. A., Matthaeus W. H., Parashar T. N., et al.
Title: Enhanced Energy Transfer Rate in Solar Wind Turbulence Observed near the Sun from Parker Solar Probe
Abstract:

Direct evidence of an inertial-range turbulent energy cascade has been provided by spacecraft observations in heliospheric plasmas. In the solar wind, the average value of the derived heating rate near 1 au is ∼10 3 Jkg −1 s −1  ∼103Jkg−1s−1 , an amount sufficient to account for observed departures from adiabatic expansion. Parker Solar Probe, even during its first solar encounter, offers the first opportunity to compute, in a similar fashion, a fluid-scale energy decay rate, much closer to the solar corona than any prior in situ observations. Using the Politano─Pouquet third-order law and the von Kármán decay law, we estimate the fluid-range energy transfer rate in the inner heliosphere, at heliocentric distance R ranging from 54 RDate: 02/2020 Publisher: The Astrophysical Journal Supplement Series Pages: 48 DOI: 10.3847/1538-4365/ab5dae Available at: https://iopscience.iop.org/article/10.3847/1538-4365/ab5dae
More Details

Authors: Parashar T. N., Goldstein M. L., Maruca B. A., Matthaeus W. H., Ruffolo D., et al.
Title: Measures of Scale-dependent Alfvénicity in the First PSP Solar Encounter
Abstract:

The solar wind shows periods of highly Alfvénic activity, where velocity fluctuations and magnetic fluctuations are aligned or antialigned with each other. It is generally agreed that solar wind plasma velocity and magnetic field fluctuations observed by the Parker Solar Probe (PSP) during the first encounter are mostly highly Alfvénic. However, quantitative measures of Alfvénicity are needed to understand how the characterization of these fluctuations compares with standard measures from prior missions in the inner and outer heliosphere, in fast wind and slow wind, and at high and low latitudes. To investigate this issue, we employ several measures to quantify the extent of Alfvénicity—the Alfvén ratio rA, the normalized cross helicity σc, the normalized r. . .
Date: 02/2020 Publisher: The Astrophysical Journal Supplement Series Pages: 58 DOI: 10.3847/1538-4365/ab64e6 Available at: https://iopscience.iop.org/article/10.3847/1538-4365/ab64e6
More Details

Authors: Bandyopadhyay Riddhi, Matthaeus W. H., Parashar T. N., Chhiber R., Ruffolo D., et al.
Title: Observations of Energetic-particle Population Enhancements along Intermittent Structures near the Sun from the Parker Solar Probe
Abstract:

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 derivatives or increments, as measured by the Partial Variance of Increments (PVI) method. One way to interpret this observation is as an association of the EPs with trapping or channeling within magnetic flux tubes, possibly near their boundaries. However, it remains unclear whether this association is a transport or local effect; i.e., the particles might have been energized at a distant location, perhaps by shocks or reconnection, or they might experience local energization or re-acceleration. The Parker Solar Probe (PSP), even in its first two orbits, offers a unique opportunity to study. . .
Date: 02/2020 Publisher: The Astrophysical Journal Supplement Series Pages: 61 DOI: 10.3847/1538-4365/ab6220 Available at: https://iopscience.iop.org/article/10.3847/1538-4365/ab6220
More Details

Authors: Qudsi R. A., Maruca B. A., Matthaeus W. H., Parashar T. N., Bandyopadhyay Riddhi, et al.
Title: Observations of Heating along Intermittent Structures in the Inner Heliosphere from PSP Data
Abstract:

The solar wind proton temperature at 1 au has been found to be correlated with small-scale intermittent magnetic structures, i.e., regions with enhanced temperature are associated with coherent structures, such as current sheets. Using Parker Solar Probe data from the first encounter, we study this association using measurements of the radial proton temperature, employing the partial variance of increments (PVI) technique to identify intermittent magnetic structures. We observe that the probability density functions of high PVI events have higher median temperatures than those with lower PVI. The regions in space where PVI peaks were also locations that had enhanced temperatures when compared with similar regions, suggesting a heating mechanism in the young solar wind that is associated. . .
Date: 02/2020 Publisher: The Astrophysical Journal Supplement Series Pages: 46 DOI: 10.3847/1538-4365/ab5c19 Available at: https://iopscience.iop.org/article/10.3847/1538-4365/ab5c19
More Details

2019
Authors: Parashar T. N., Cuesta M., and Matthaeus W. H.
Title: Reynolds Number and Intermittency in the Expanding Solar Wind: Predictions Based on Voyager Observations
Abstract:

The large-scale features of the solar wind are examined in order to predict small-scale features of turbulence in unexplored regions of the heliosphere. The strategy is to examine how system size, or effective Reynolds number Re, varies, and then how this quantity influences observable statistical properties, including intermittency properties of solar wind turbulence. The expectation based on similar hydrodynamics scalings is that the kurtosis, of the small-scale magnetic field increments, will increase with increasing Re. Simple theoretical arguments as well as Voyager observations indicate that effective interplanetary turbulence Re decreases with increasing heliocentric distance. The decrease of scale-dependent magnetic increment kurtosis with increasing heliocentric distance is ver. . .
Date: 10/2019 Publisher: The Astrophysical Journal Pages: L57 DOI: 10.3847/2041-8213/ab4a82 Available at: https://iopscience.iop.org/article/10.3847/2041-8213/ab4a82
More Details