Parker Solar Probe Bibliography

2019

The Wide-field Imager for the Parker Solar Probe (PSP/WISPR) comprises two telescopes that record white-light total brightness [B] images of the solar corona. Their fields of view cover a widely changing range of heliocentric heights over the 24 highly eccentric orbits planned for the mission. In this work, the capability of PSP/WISPR data to carry out tomographic reconstructions of the three-dimensional (3D) distribution of the coronal electron density is investigated. Based on the precise orbital information of the mission, B-images for Orbits 1, 12, and 24 are synthesized from a 3D magnetohydrodynamic model of the corona. For each orbit, the time series of synthetic images is used to carry out a tomographic reconstruction of the coronal electron density and results are compared with the model. As the PSP perihelion decreases, the range of heights that can be tomographically reconstructed progressively shifts to lower values, and the period required to gather the data decreases. For…
2019


In this Letter we propose a practical methodology to interpret future Parker Solar Probe (PSP) turbulent time signals even when Taylor s hypothesis is not valid. By extending Kraichnan s sweeping model used in hydrodynamics we derive the Eulerian spacetime correlation function in magnetohydrodynamic (MHD) turbulence. It is shown that in MHD, the temporal decorrelation of small-scale fluctuations arises from a combination of hydrodynamic sweeping induced by large-scale fluid velocity delta u(0) and by the Alfvenic propagation along the local magnetic field. The resulting temporal part of the spacetime correlation function is used to determine the field-perpendicular wavenumber range
2019


We examine Alfven Wave Solar atmosphere Model (AWSoM) predictions of the first Parker Solar Probe (PSP) encounter. We focus on the 12 day closest approach centered on the first perihelion. AWSoM allows us to interpret the PSP data in the context of coronal heating via Alfven wave turbulence. The coronal heating and acceleration is addressed via outward-propagating low-frequency Alfven waves that are partially reflected by Alfven speed gradients. The nonlinear interaction of these counter-propagating waves results in a turbulent energy cascade. To apportion the wave dissipation to the electron and anisotropic proton temperatures, we employ the results of the theories of linear wave damping and nonlinear stochastic heating as described by Chandran et al. We find that during the first encounter, PSP was in close proximity to the heliospheric current sheet (HCS) and in the slow wind. PSP crossed the HCS two times, at 2018 November 3 UT 01:02 and 2018 November 8 UT 19:09, with perihelion…
2019


The recently launched Parker Solar Probe (PSP) mission is expected to provide unprecedented views of the solar corona and inner heliosphere. In addition to instruments devoted to taking measurements of the local solar wind, the spacecraft carries a visible imager: the Wide-field Imager for Solar PRobe (WISPR). WISPR will take advantage of the proximity of the spacecraft to the Sun to perform local imaging of the near-Sun environment. WISPR will observe coronal structures at high spatial and time resolutions, although the observed plane-of-sky will rapidly change because of the fast transit at the perihelia. We present a concise description of the PSP mission, with particular regard to the WISPR instrument, discussing its main scientific goals, targets of observations, and outlining the possible synergies with current and upcoming space missions.
2019


Parker-spiral theory predicts that the heliospheric magnetic field (HMF) will have components of opposite polarity radially toward the Sun and tangentially antiparallel to the solar rotation direction (i.e., in Geocentric Solar Ecliptic (GSE) coordinates, with BX/BY<0). This theory explains the average orientation of the HMF very well indeed but does not predict the so-called ortho-gardenhose (hereafter OGH) flux with which is frequently observed. We here study the occurrence and structure of OGH flux, as seen in near-Earth space (heliocentric distance AU) by the Wind and Advanced Composition Explorer (ACE) spacecraft (for 1995-2017, inclusive) and by the Helios-1 and -2 spacecraft at 0.29(for December 1974 to August 1981), in order to evaluate the contributions to OGH flux generation of the various mechanisms and factors that are not accounted for by Parker-spiral theory. We study the loss of OGH flux with increasing averaging timescale between 16seconds and 100 hours and so…
2019


Accurate reconstruction of global solar-wind structure is essential for connecting remote and in situ observations of solar plasma, and hence understanding formation and release of solar wind. Information can routinely be obtained from photospheric magnetograms, via coronal and solar-wind modelling, and directly from in situ observations, typically at large heliocentric distances (most commonly near 1 AU). Magnetogram-constrained modelling has the benefit of reconstructing global solar-wind structure, but with relatively large spatial and/or temporal errors. In situ observations, on the other hand, make accurate temporal measurements of solar-wind structure, but are highly localised. We here use a data assimilative (DA) approach to combine these two sources of information as a first step towards producing a solar-wind reanalysis dataset that optimally combines model and observation. The physics of solar wind stream interaction is used to extrapolate in heliocentric distance, while the…
2019


The Parker Solar Probe (PSP) primary mission extends seven years and consists of 24 orbits of the Sun with descending perihelia culminating in a closest approach of similar to 9.8 R-circle dot. In the course of these orbits PSP will pass through widely varying conditions, including anticipated large variations of turbulence properties, such as energy density, correlation scales, and cross helicities. Here we employ global magnetohydrodynamic simulations with self-consistent turbulence transport and heating to preview conditions that will likely be encountered by PSP by assuming suitable boundary conditions at the coronal base. The code evolves large-scale parameters-such as the velocity, magnetic field, and temperature-as well as the turbulent energy density, cross helicity, and correlation scale. These computed quantities provide the basis for evaluating additional useful parameters that are derivable from the primary model outputs. Here we illustrate one such possibility in which…
2019


2018

<p>Robustly identifying the solar sources of individual packets of solar wind measured in interplanetary space remains an open problem. We set out to see if this problem is easier to tackle using solar wind measurements closer to the Sun than 1 au, where the mixing and dynamical interaction of different solar wind streams is reduced. Using measurements from the Helios mission, we examined how the proton core temperature anisotropy and cross-helicity varied with distance. At 0.3 au there are two clearly separated anisotropic and isotropic populations of solar wind that are not distinguishable at 1 au. The anisotropic population is always Alfv\ enic and spans a wide range of speeds. In contrast the isotropic population has slow speeds, and contains a mix of Alfv\ enic wind with constant mass fluxes and non-Alfv\ enic wind with large and highly varying mass fluxes. We split the in situ measurements into three categories according these observations, and suggest that these…
2018


<p>The inner magnetosphere including the radiation belt and ring current environment is replete with high-frequency fluctuations with peak intensity occurring near upper-hybrid frequency and/or multiple harmonic electron cyclotron frequencies above and below the upper-hybrid frequency. Past and contemporary spacecraft missions, including the Van Allen Probes, were designed to detect the electric field spectrum only for these high-frequency fluctuations. Making use of the recently formulated generalized theory of electromagnetic spontaneous emission in thermal magnetized plasmas, it is shown that upper-hybrid/multiple harmonic electron cyclotron emissions are characterized by a significant magnetic field component, even in the high-frequency regime. Such a prediction may potentially be tested by upcoming spacecraft missions including the Solar Probe Orbiter and Parker Solar Probe. The present finding may also have a potentially significant ramification for the broader…
2018


<p>To test a technique to be used on the white-light imager onboard the recently launched Parker Solar Probe mission, we performed a numerical differentiation of the brightness profiles along the photometric axis of the F-corona models that are derived from STEREO Ahead Sun Earth Connection Heliospheric Investigation observations recorded with the HI-1 instrument between 2007 December and 2014 March. We found a consistent pattern in the derivatives that can be observed from any S/C longitude between about 18\textdegree and 23\textdegree elongation with a maximum at about 21\textdegree. These findings indicate the presence of a circumsolar dust density enhancement that peaks at about 23\textdegree elongation. A straightforward integration of the excess signal in the derivative space indicates that the brightness increase over the background F-corona is on the order of 1.5\%-2.5\%, which implies an excess dust density of about 3\%-5\% at the center of the ring. This study has also…
2018


<p>In situ spacecraft observations provide much-needed constraints on theories of solar wind formation and release, particularly the highly variable slow solar wind, which dominates near-Earth space. Previous studies have shown an association between local inversions in the heliospheric magnetic field (HMF) and solar wind released from the vicinity of magnetically closed coronal structures. We here show that in situ properties of inverted HMF are consistent with the same hot coronal source regions as the slow solar wind. We propose that inverted HMF is produced by solar wind speed shear, which results from interchange reconnection between a coronal loop and open flux tube, and introduces a pattern of fast-slow-fast wind along a given HMF flux tube. This same loop-opening process is thought to be central to slow solar wind formation. The upcoming Parker Solar Probe and Solar Orbiter missions provide a unique opportunity to directly observe these processes and thus determine the…
2018


<p>In science news around the world, the U.S. National Institutes of Health (NIH) responds to a report on "foreign influences," Australia slashes its future research funding, Mars\textquoterights methane mystery deepens, and the Paris agreement on climate change survives a contentious rulemaking session in Poland. Also, astronomers discover the solar system\textquoterights farthest-known planet, NIH comes under fire for clinical trial reporting results, the late Paul Allen bequests a new immunology research institute, and NASA\textquoterights Parker Solar Probe makes its first dip into the sun\textquoterights atmosphere. Plus, a new study suggests tourists and scientists are making Antarctica\textquoterights birds sick, and an interview with a Harvard University historian helps explain India\textquoterights monsoon\textemdashone of Asia\textquoterights most important weather patterns.</p>
2018


<p>Interplanetary coronal mass ejections (ICMEs) often cause Forbush decreases (Fds) in the flux of galactic cosmic rays (GCRs). We investigate how a single ICME, launched from the Sun on 2014 February 12, affected GCR fluxes at Mercury, Earth, and Mars. We use GCR observations from MESSENGER at Mercury, ACE/LRO at the Earth/Moon, and MSL at Mars. We find that Fds are steeper and deeper closer to the Sun, and that the magnitude of the magnetic field in the ICME magnetic ejecta as well as the \textquotedblleftstrength\textquotedblright of the ICME sheath both play a large role in modulating the depth of the Fd. Based on our results, we hypothesize that (1) the Fd size decreases exponentially with heliocentric distance, and (2) that two-step Fds are more common closer to the Sun. Both hypotheses will be directly verifiable by the upcoming Parker Solar Probe and Solar Orbiter missions. This investigation provides the first systematic study of the changes in GCR modulation as a…
2018


<p>The fast solar wind shows a wide spectrum of transverse magnetic and velocity field perturbations. These perturbations are strongly correlated in the sense of Alfv\ en waves propagating mostly outward, from the Sun to the interplanetary medium. They are likely to be fundamental to the acceleration and the heating of the solar wind. However, the precise origin of the broadband spectrum is unknown to date. Typical periods of chromospheric Alfv\ en waves are limited to a few minutes, and any longer period perturbations should be strongly reflected at the transition region. In this work, we show that minute long Alfv\ enic fluctuations are unstable to the parametric instability. Parametric instability enables an inverse energy cascade by exciting several-hour-long periods of Alfv\ enic fluctuations together with strong density fluctuations (typically between 1 and 20 R <sub>☉</sub>). These results may improve our understanding of the origin of the solar wind turbulent…
2018


<p>In this paper, weak-turbulence theory is used to investigate the nonlinear evolution of the parametric instability in three-dimensional low-β plasmas at wavelengths much greater than the ion inertial length under the assumption that slow magnetosonic waves are strongly damped. It is shown analytically that the parametric instability leads to an inverse cascade of Alfv\ en wave quanta, and several exact solutions to the wave kinetic equations are presented. The main results of the paper concern the parametric decay of Alfv\ en waves that initially satisfy e<sup>+</sup> >> e<sup>-</sup>, where e<sup>+</sup> and e<sup>-</sup> are the frequency (f) spectra of Alfv\ en waves propagating in opposite directions along the magnetic field lines. If e<sup>+</sup> initially has a peak frequency f<sub>0</sub> (at which fe<sup>+</sup> is maximized) and an \textquoterightinfrared\textquoteright scaling…
2018


<p>The current fleet of space-based solar observatories offers us a wealth of opportunities to study solar flares over a range of wavelengths. Significant advances in our understanding of flare physics often come from coordinated observations between multiple instruments. Consequently, considerable efforts have been, and continue to be, made to coordinate observations among instruments ( e.g. through the Max Millennium Program of Solar Flare Research). However, there has been no study to date that quantifies how many flares have been observed by combinations of various instruments. Here we describe a technique that retrospectively searches archival databases for flares jointly observed by the Ramaty High Energy Solar Spectroscopic Imager (RHESSI), Solar Dynamics Observatory (SDO)/ EUV Variability Experiment (EVE - Multiple EUV Grating Spectrograph (MEGS)-A and -B, Hinode/( EUV Imaging Spectrometer, Solar Optical Telescope, and X-Ray Telescope), and Interface Region Imaging…
2018


<p>Deep-space exploration of the inner heliosphere is in an unprecedented golden age, with the recent and forthcoming launches of the Parker Solar Probe (PSP) and Solar Orbiter (SolO) missions, respectively. In order to both predict and understand the prospective observations by PSP and SolO, we perform forward MHD modeling of the 3D inner heliosphere at solar minimum, and synthesize the white-light (WL) emission that would result from Thomson scattering of sunlight from the coronal and heliospheric plasmas. Both solar rotation and spacecraft trajectory should be considered when reconstructing quiescent large-scale solar-wind streams from PSP and SolO WL observations. When transformed from a static coordinate system into a corotating one, the elliptical orbit of PSP becomes a multiwinding spiral. The innermost spiral winding of this corotating PSP orbit takes the form of a closed \textquotedblleftheart shape\textquotedblright within around 80 R <sub>☉</sub> of the…
2018


<p>Spacecraft observations have shown that the proton temperature in the solar wind falls off with radial distance more slowly than expected for an adiabatic prediction. Usually, previous studies have been focused on the evolution of the solar-wind plasma by using the bulk speed as an order parameter to discriminate different regimes. In contrast, here, we study the radial evolution of pure and homogeneous fast streams (i.e. well-defined streams of coronal-hole plasma that maintain their identity during several solar rotations) by means of re-processed particle data, from the HELIOS satellites between 0.3 and 1 au. We have identified 16 intervals of unperturbed high-speed coronal-hole plasma, from three different sources and measured at different radial distances. The observations show that, for all three streams, (i) the proton density decreases as expected for a radially expanding plasma, unlike previous analysis that found a slower decrease; (ii) the magnetic field deviates…
2018


<p>Solar wind turbulence within high-speed streams is reviewed from the point of view of embedded single nonlinear Alfv\ en wave cycles, discontinuities, magnetic decreases (MDs), and shocks. For comparison and guidance, cometary plasma turbulence is also briefly reviewed. It is demonstrated that cometary nonlinear magnetosonic waves phase-steepen, with a right-hand circular polarized foreshortened front and an elongated, compressive trailing edge. The former part is a form of "wave breaking" and the latter that of "period doubling." Interplanetary nonlinear Alfv\ en waves, which are arc polarized, have a 180\textdegree foreshortened front and with an elongated trailing edge. Alfv\ en waves have polarizations different from those of cometary magnetosonic waves, indicating that helicity is a durable feature of plasma turbulence. Interplanetary Alfv\ en waves are noted to be spherical waves, suggesting the possibility of additional local generation. They…
2018


<p>We report the presence of intermittent, short discrete enhancements in plasma speed in the near-Sun high-speed solar wind. Lasting tens of seconds to minutes in spacecraft measurements at 0.3 au, speeds inside these enhancements can reach 1000 km s<sup>-1</sup>, corresponding to a kinetic energy up to twice that of the bulk high-speed solar wind. These events, which occur around 5 per cent of the time, are Alfv\ enic in nature with large magnetic field deflections and are the same temperature as the surrounding plasma, in contrast to the bulk fast wind which has a well-established positive speed-temperature correlation. The origin of these speed enhancements is unclear but they may be signatures of discrete jets associated with transient events in the chromosphere or corona. Such large short velocity changes represent a measurement and analysis challenge for the upcoming Parker Solar Probe and Solar Orbiter missions.</p>
2018


<p>Solar coronal jets are small, transient, collimated ejections most easily observed in coronal holes (CHs). The upcoming Parker Solar Probe (PSP) mission provides the first opportunity to encounter CH jets in situ near the Sun and examine their internal structure and dynamics. Using projected mission orbital parameters, we have simulated PSP encounters with a fully three-dimensional magnetohydrodynamic (MHD) model of a CH jet. We find that three internal jet regions, featuring different wave modes and levels of compressibility, have distinct identifying signatures detectable by PSP. The leading Alfv\ en wave front and its immediate wake are characterized by trans-Alfv\ enic plasma flows with mild density enhancements. This front exhibits characteristics of a fast switch-on MHD shock, whose arrival is signaled by the sudden onset of large-amplitude transverse velocity and magnetic-field oscillations highly correlated in space and time. The trailing portion is characterized by…
2018


<p>Alfv\ enic fluctuations are very common features in the solar wind and are found especially within the main portion of fast-wind streams while the slow wind usually is less Alfv\ enic and more variable. In general, the fast and slow winds show many differences, which span from the large-scale structure to small-scale phenomena, including also a different turbulent behaviour. Recent studies, however, have shown that even the slow wind can sometimes be highly Alfv\ enic, with fluctuations as large as those of the fast wind. This study is devoted to presenting many facets of this Alfv\ enic slow solar wind, including for example the study of the source regions and their connection to coronal structures, large-scale properties, and microscale phenomena and also impact on the spectral features. This study will be conducted performing a comparative analysis with the typical slow wind and with the fast wind. It has been found that the fast wind and the Alfv\ enic slow wind share…
2018


<p>In this work we advocate for the idea that two seemingly unrelated 80-year-old mysteries\textemdashthe nature of dark matter and the high temperature of the million degree solar corona\textemdashmay have resolutions that lie within the same physical framework. The current paradigm is that the corona is heated by nanoflares, which were originally proposed as miniature versions of the observed solar flares. It was recently suggested that the nanoflares could be identified as annihilation events of the nuggets from the axion quark nugget (AQN) dark matter model. This model was invented as an explanation of the observed ratio Ω<sub>dark</sub>̃Ω<sub>visible</sub>, based only on cosmological and particle physics considerations. In this new paradigm, the AQN particles moving through the coronal plasma and annihilating with normal matter can lead to the drastic change of temperatures seen in the Sun\textquoterights transition region (TR), and significantly…
2018


<p>Context. The Parker Solar Probe (PSP; formerly Solar Probe Plus) mission will be humanitys first in situ exploration of the solar corona with closest perihelia at 9.86 solar radii (R<sub>☉</sub>) distance to the Sun. It will help answer hitherto unresolved questions on the heating of the solar corona and the source and acceleration of the solar wind and solar energetic particles. The scope of this study is to model the solar-wind environment for PSPs unprecedented distances in its prime mission phase during the years 2018 to 2025. The study is performed within the Coronagraphic German And US SolarProbePlus Survey (CGAUSS) which is the German contribution to the PSP mission as part of the Wide-field Imager for Solar PRobe. Aim. We present an empirical solar-wind model for the inner heliosphere which is derived from OMNI and Helios data. The German-US space probes Helios 1 and Helios 2 flew in the 1970s and observed solar wind in the ecliptic within heliocentric…
2018


<p>A component of space weather, electron beams are routinely accelerated in the solar atmosphere and propagate through interplanetary space. Electron beams interact with Langmuir waves resulting in type III radio bursts. They expand along the trajectory and, using kinetic simulations, we explore the expansion as the electrons propagate away from the Sun. Specifically, we investigate the front, peak, and back of the electron beam in space from derived radio brightness temperatures of fundamental type III emission. The front of the electron beam travels at speeds from 0.2c to 0.7c, significantly faster than the back of the beam, which travels at speeds between 0.12c and 0.35c. The difference in speed between the front and the back elongates the electron beam in time. The rate of beam elongation has a 0.98 correlation coefficient with the peak velocity, in line with predictions from type III observations. The inferred speeds of electron beams initially increase close to the…
2018


<p>In situ measurements of the fast solar wind reveal non-thermal distributions of electrons, protons, and minor ions extending from 0.3 au to the heliopause. The physical mechanisms responsible for these non-thermal properties and the location where these properties originate remain open questions. Here, we present spectroscopic evidence, from extreme ultraviolet spectroscopy, that the velocity distribution functions (VDFs) of minor ions are already non-Gaussian at the base of the fast solar wind in a coronal hole, at altitudes of \&lt;1.1 R <sub>☉</sub>. Analysis of Fe, Si, and Mg spectral lines reveals a peaked line-shape core and broad wings that can be characterized by a kappa VDF. A kappa distribution fit gives very small kappa indices off-limb of κ ≈ 1.9-2.5, indicating either (a) ion populations far from thermal equilibrium, (b) fluid motions such as non-Gaussian turbulent fluctuations or non-uniform wave motions, or (c) some combination of both. These…
2018


After 60 years of technological and materials development, in August this year the Parker Solar Probe set off on its journey to skim the atmosphere of the Sun. Mission Scientist Adam Szabo summarizes this ambitious adventure.
2018