Browsing by Author "R. Qudsi"

Filter results by typing the first few letters
Now showing 1 - 4 of 4
  • No Thumbnail Available
    PublicationMetadata only
    Clustering of Intermittent Magnetic and Flow Structures near Parker Solar Probe's First Perihelion - A Partial-variance-of-increments Analysis
    (2020-02-01) Rohit Chhiber; M. L. Goldstein; B. A. Maruca; A. Chasapis; W. H. Matthaeus; D. Ruffolo; R. Bandyopadhyay; T. N. Parashar; R. Qudsi; T. Dudok De Wit; S. D. Bale; J. W. Bonnell; K. Goetz; P. R. Harvey; R. J. MacDowall; D. Malaspina; M. Pulupa; J. C. Kasper; K. E. Korreck; A. W. Case; M. Stevens; P. Whittlesey; D. Larson; R. Livi; M. Velli; N. Raouafi; Universite d'Orleans; University of Minnesota Twin Cities; Space Sciences Laboratory at UC Berkeley; University of California, Los Angeles; University of Michigan, Ann Arbor; University of California, Berkeley; University of Maryland, Baltimore County; University of Delaware; Johns Hopkins University Applied Physics Laboratory; Imperial College London; Mahidol University; Smithsonian Astrophysical Observatory; NASA Goddard Space Flight Center; The Bartol Research Institute; University of Colorado Boulder
    © 2020. The American Astronomical Society. All rights reserved.. During the Parker Solar Probe's (PSP) first perihelion pass, the spacecraft reached within a heliocentric distance of ∼37 R o˙ 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 power-law distributions for WT shorter than a characteristic scale comparable to the correlation time of the fluctuations, suggesting a high degree of correlation that may originate in a clustering process. WT longer than this characteristic time are better described by an exponential, suggesting a random memory-less Poisson process at play. These findings are consistent with near-Earth observations of solar wind turbulence. The present study complements the one by Dudok de Wit et al., which focuses on WT between observed "switchbacks" in the radial magnetic field.
  • No Thumbnail Available
    PublicationMetadata only
    Enhanced Energy Transfer Rate in Solar Wind Turbulence Observed near the Sun from Parker Solar Probe
    (2020-02-01) Riddhi Bandyopadhyay; M. L. Goldstein; B. A. Maruca; W. H. Matthaeus; T. N. Parashar; D. Ruffolo; R. Chhiber; A. Usmanov; A. Chasapis; R. Qudsi; Stuart D. Bale; J. W. Bonnell; Thierry Dudok De Wit; Keith Goetz; Peter R. Harvey; Robert J. MacDowall; David M. Malaspina; Marc Pulupa; J. C. Kasper; K. E. Korreck; A. W. Case; M. Stevens; P. Whittlesey; D. Larson; R. Livi; K. G. Klein; M. Velli; N. Raouafi; Universite d'Orleans; University of Minnesota Twin Cities; Space Sciences Laboratory at UC Berkeley; University of California, Los Angeles; University of Michigan, Ann Arbor; University of California, Berkeley; University of Maryland, Baltimore County; Queen Mary, University of London; Johns Hopkins University Applied Physics Laboratory; Imperial College London; Mahidol University; The University of Arizona; Smithsonian Astrophysical Observatory; NASA Goddard Space Flight Center; The Bartol Research Institute; University of Colorado Boulder
    © 2020. The American Astronomical Society. All rights reserved.. 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 ∼103 Jkg-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 R o˙ (0.25 au) to 36 R o˙ (0.17 au). The energy transfer rate obtained near the first perihelion is about 100 times higher than the average value at 1 au, which is in agreement with estimates based on a heliospheric turbulence transport model. This dramatic increase in the heating rate is unprecedented in previous solar wind observations, including those from Helios, and the values are close to those obtained in the shocked plasma inside the terrestrial magnetosheath.
  • No Thumbnail Available
    PublicationMetadata only
    Measures of Scale-dependent Alfvénicity in the First PSP Solar Encounter
    (2020-02-01) T. N. Parashar; M. L. Goldstein; M. L. Goldstein; B. A. Maruca; W. H. Matthaeus; D. Ruffolo; R. Bandyopadhyay; R. Chhiber; R. Chhiber; A. Chasapis; R. Qudsi; D. Vech; D. Vech; D. A. Roberts; S. D. Bale; S. D. Bale; S. D. Bale; J. W. Bonnell; T. Dudok De Wit; K. Goetz; P. R. Harvey; R. J. MacDowall; D. Malaspina; M. Pulupa; J. C. Kasper; J. C. Kasper; K. E. Korreck; A. W. Case; M. Stevens; P. Whittlesey; D. Larson; R. Livi; M. Velli; N. Raouafi; Universite d'Orleans; University of Minnesota Twin Cities; Space Sciences Laboratory at UC Berkeley; University of California, Los Angeles; University of Michigan, Ann Arbor; University of California, Berkeley; University of Maryland, Baltimore County; Imperial College London; Mahidol University; Smithsonian Astrophysical Observatory; NASA Goddard Space Flight Center; Johns Hopkins University; The Bartol Research Institute; University of Colorado Boulder
    © 2020. The American Astronomical Society. All rights reserved.. 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 r A, the normalized cross helicity σ c , the normalized residual energy σ r , and the cosine of angle between velocity and magnetic fluctuations . We show that despite the overall impression that the Alfvénicity is large in the solar wind sampled by PSP during the first encounter, during some intervals the cross helicity starts decreasing at very large scales. These length scales (often >1000d i ) are well inside inertial range, and therefore, the suppression of cross helicity at these scales cannot be attributed to kinetic physics. This drop at large scales could potentially be explained by large scale shears present in the inner heliosphere sampled by PSP. In some cases, despite the cross helicity being constant down to the noise floor, the residual energy decreases with scale in the inertial range. These results suggest that it is important to consider all these measures to quantify Alfvénicity.
  • No Thumbnail Available
    PublicationMetadata only
    Observations of Energetic-particle Population Enhancements along Intermittent Structures near the Sun from the Parker Solar Probe
    (2020-02-01) Riddhi Bandyopadhyay; W. H. Matthaeus; T. N. Parashar; R. Chhiber; D. Ruffolo; M. L. Goldstein; B. A. Maruca; A. Chasapis; R. Qudsi; D. J. McComas; E. R. Christian; J. R. Szalay; C. J. Joyce; J. Giacalone; N. A. Schwadron; D. G. Mitchell; M. E. Hill; M. E. Wiedenbeck; R. L. McNutt; M. I. Desai; Stuart D. Bale; J. W. Bonnell; Thierry Dudok De Wit; Keith Goetz; Peter R. Harvey; Robert J. MacDowall; David M. Malaspina; Marc Pulupa; M. Velli; J. C. Kasper; K. E. Korreck; M. Stevens; A. W. Case; N. Raouafi; California Institute of Technology; Universite d'Orleans; University of Minnesota Twin Cities; Space Sciences Laboratory at UC Berkeley; University of New Hampshire Durham; University of California, Los Angeles; University of Michigan, Ann Arbor; University of California, Berkeley; University of Maryland, Baltimore County; University of Delaware; Queen Mary, University of London; Johns Hopkins University Applied Physics Laboratory; Imperial College London; Mahidol University; The University of Arizona; Smithsonian Astrophysical Observatory; NASA Goddard Space Flight Center; Princeton University; University of Texas at San Antonio; The Bartol Research Institute; University of Colorado Boulder
    © 2020. The American Astronomical Society. All rights reserved.. 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 this statistical correlation closer to the corona. As a first step, we analyze the separate correlation properties of the EPs measured by the Integrated Science Investigation of the Sun (ISo˙IS) instruments during the first solar encounter. The distribution of time intervals between a specific type of event, i.e., the waiting time, can indicate the nature of the underlying process. We find that the ISo˙IS observations show a power-law distribution of waiting times, indicating a correlated (non-Poisson) distribution. Analysis of low-energy (∼15 - 200 keV/nuc) ISo˙IS data suggests that the results are consistent with the 1 au studies, although we find hints of some unexpected behavior. A more complete understanding of these statistical distributions will provide valuable insights into the origin and propagation of solar EPs, a picture that should become clear with future PSP orbits.