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The fast solar wind's high speeds and nonthermal features require that significant heating occurs well above the Sun's surface. Two leading theories seem incompatible: low-frequency "Alfv\'enic" turbulence, which transports energy outwards…
The variability of helium abundance in the solar corona and the solar wind is an important signature of solar activity, solar cycle, solar wind sources, as well as coronal heating processes. Motivated by recently reported remote sensing UV…
The probability distributions (PDFs) of the differences of any physical variable in the intermittent, turbulent interplanetary medium are scale dependent. Strong non-Gaussianity of solar wind fluctuations applies for short time-lag…
We operate the six German stations of the LOw Frequency ARray as standalone telescopes to observe more than 100 pulsars every week. To date, we have collected almost four years of high-quality data at an unprecedented weekly cadence. This…
We analyze a merged Parker Solar Probe ($PSP$) and Solar Orbiter ($SO$) dataset covering heliocentric distances $13 \ R_{\odot} \lesssim R \lesssim 220$ $R_{\odot}$ to investigate the radial evolution of power and spectral-index anisotropy…
We make use of the Parker Solar Probe (PSP) data to explore the nature of solar wind turbulence focusing on the Alfv\'enic character and power spectra of the fluctuations and their dependence on distance and context (i.e. large scale solar…
At kinetic scales in the solar wind, instabilities transfer energy from particles to fluctuations in the electromagnetic fields while restoring plasma conditions towards thermodynamic equilibrium. We investigate the interplay between…
In this paper, I present the results on large-scale evolution of density turbulence of solar wind in the inner heliosphere during 1985 - 2009. At a given distance from the Sun, the density turbulence is maximum around the maximum phase of…
Weakly collisional plasmas are subject to nonlinear relaxation processes, which can operate at rates much faster than the particle collision frequencies. This causes the plasma to respond like a magnetised fluid despite having long particle…
We analyze helioseismic waves near the solar equator in the presence of magnetic fields deep within the solar radiative zone. We find that reasonable magnetic fields can significantly alter the shapes of the wave profiles for helioseismic…
We present a study of magnetic field fluctuations, in a slow solar wind stream, close to ion scales, where an increase of the level of magnetic compressibility is observed. Here, the nature of these compressive fluctuations is found to be…
Local inversions are often observed in the heliospheric magnetic field (HMF), but their origins and evolution are not yet fully understood.Parker Solar Probe has recently observed rapid, Alfvenic, HMF inversions in the inner heliosphere,…
We derive formulae connecting the frequency variations in the spectrum of solar oscillations to the dynamical quantities that are expected to change over the solar activity cycle. This is done for both centroids and the asymmetric part of…
Solar flare accelerated electron beams propagating away from the Sun can interact with the turbulent interplanetary media, producing plasma waves and type III radio emission. These electron beams are detected near the Earth with a double…
Non-thermal electron populations are observed throughout the heliosphere. The relaxation of an electron beam is known to produce Langmuir waves which, in turn, may substantially modify the electron distribution function. As the Langmuir…
The solar wind in the inner heliosphere has been observed by Parker Solar Probe (PSP) to exhibit abundant wave activities. The cyclotron wave modes in the sense of ions or electrons are among the most crucial wave components. However, their…
The two-state solar wind paradigm is based on observations showing that slow and fast solar wind have distinct properties like helium abundances, kinetic signatures, elemental composition, and charge-state ratios. Nominally, the fast wind…
Although the solar wind flows primarily outward from the Sun to interplanetary space, there are times when small-scale plasma inflows are observed. Inward-propagating density fluctuations in polar coronal holes were detected by the COR2…
Meridional flow in the solar interior plays an important role in redistributing angular momentum and transporting magnetic flux inside the Sun. Although it has long been recognized that the meridional flow is predominantly poleward at the…
The Bandt-Pompe permutation entropy and the Jensen-Shannon statistical complexity are used to analyze fluctuating time series of three different plasmas: the magnetohydrodynamic (MHD) turbulence in the plasma wind tunnel of the Swarthmore…