Electrostatic Waves with Rapid Frequency Shifts in the Solar Wind Sunward of 1/3 AU

During its first five orbits, the FIELDS plasma wave investigation on board Parker Solar Probe (PSP)&#160; has observed a multitude of plasma waves, including electrostatic whistler and electron Bernstein waves (Malaspina et al. 2020), sunward propagating whistlers (Agapitov et al. 2020), ion-scale electromagnetic waves (Verniero et al. 2020, Bowen et al. 2020) and Alfven, slow and fast mode waves (Chaston et al. 2020).The importance of these waves lies in their potential to redistribute the energy of the solar wind among different particles species (wave-particle interactions) or different types of waves (wave-wave interactions). The abundance of waves and instabilities observed with PSP points to their central role in the regulation of this energy exchange.Here we present first observations of an intermittent, electrostatic and broadband plasma wave that is ubiquitous in the range of distances that PSP has probed so far. A unique feature of these waves (FDWs) is a frequency shift that occurs on millisecond timescales. In the frame of the spacecraft, FDWs usually appear between the electron cyclotron and electron plasma frequencies.We develop a detection algorithm that identifies the FDWs in low cadence spectra. We analyze them using various statistical techniques. We establish their phenomenology and compare the magnetic fluctuations of the background magnetic field at times of FDWs and at times without FDWs. We establish their polarization with respect to the background magnetic field and search for correlations with various plasma parameters and features in the electron, proton and alpha particle distribution moments. We also investigate possible plasma wave modes that could be responsible for the growth of FDWs and the instability mechanisms that could be generating them.&#160;Lily Kromyda*(1), David M. Malaspina (1,2), Robert E. Ergun(1,2) , Jasper Halekas(3), Michael L. Stevens(4) , Jennifer Verniero(5), Alexandros Chasapis(2) , Daniel Vech(2) , Stuart D. Bale(5,6) , John W. Bonnell(5) , Thierry Dudok de Wit(7) , Keith Goetz(8) , Katherine Goodrich(5) , Peter R. Harvey(5) , Robert J. MacDowall(9) , Marc Pulupa(5) , Anthony W. Case(4) , Justin C. Kasper(10) , Kelly E. Korreck(4) , Davin Larson(5) , Roberto Livi(5) , Phyllis Whittlesey(5)(1) Astrophysical and Planetary Sciences Department, University of Colorado, Boulder, CO, USA(2) Laboratory for Atmospheric and Space Physics, University of Colorado, Boulder, CO, USA(3) &#160;University of Iowa, Iowa City, IA, USA(4) Harvard-Smithsonian Center for Astrophysics, Cambridge, MA, USA(5) &#160;Space Sciences Laboratory, University of California, Berkeley, CA, USA(6) Physics Department, University of California, Berkeley, CA, USA(7) &#160;LPC2E, CNRS, and University of Orleans, Orleans, France(8) &#160;School of Physics and Astronomy, University of Minnesota, Minneapolis, MN, USA(9) &#160;NASA Goddard Space Flight Center, Greenbelt, MD, USA(10) University of Michigan, Ann Arbor, MI, USA

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HelioSwarm: The Nature of Turbulence in Space Plasmas

10.5194/egusphere-egu21-12092 ◽

2021 ◽

Author(s):

Harlan Spence ◽

Kristopher Klein ◽

HelioSwarm Science Team

Keyword(s):

Magnetic Field ◽

Solar Wind ◽

Large Scale ◽

Solar Wind Plasma ◽

Turbulent Energy ◽

Space Plasmas ◽

Plasma Parameters ◽

Astrophysical Plasmas ◽

Ion Distributions ◽

Background Magnetic Field

Recently selected for phase A study for NASA&#8217;s Heliophysics MidEx Announcement of Opportunity, the HelioSwarm Observatory proposes to transform our understanding of the physics of turbulence in space and astrophysical plasmas by deploying nine spacecraft to measure the local plasma and magnetic field conditions at many points, with separations between the spacecraft spanning MHD and ion scales.&#160;&#160;HelioSwarm resolves the transfer and dissipation of turbulent energy in weakly-collisional magnetized plasmas with a novel configuration of spacecraft in the solar wind. These simultaneous multi-point, multi-scale measurements of space plasmas allow us to reach closure on two science goals comprised of six science objectives: (1) reveal how turbulent energy is transferred in the most probable, undisturbed solar wind plasma and distributed as a function of scale and time; (2) reveal how this turbulent cascade of energy varies with the background magnetic field and plasma parameters in more extreme solar wind environments; (3) quantify the transfer of turbulent energy between fields, flows, and ion heat; (4) identify thermodynamic impacts of intermittent structures on ion distributions; (5) determine how solar wind turbulence affects and is affected by large-scale solar wind structures; and (6) determine how strongly driven turbulence differs from that in the undisturbed solar wind.&#160;

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MHD and Ion Kinetic Waves in Field-aligned Flows Observed by Parker Solar Probe

The Astrophysical Journal ◽

10.3847/1538-4357/ac28fb ◽

2021 ◽

Vol 922 (2) ◽

pp. 188

Author(s):

L.-L. Zhao ◽

G. P. Zank ◽

J. S. He ◽

D. Telloni ◽

L. Adhikari ◽

...

Keyword(s):

Magnetic Field ◽

Solar Wind ◽

Whistler Wave ◽

Spectral Energy ◽

Small Scale ◽

The Sun ◽

Fast Mode ◽

Magnetic Fluctuations ◽

Background Magnetic Field ◽

Ion Cyclotron

Abstract Parker Solar Probe (PSP) observed predominately Alfvénic fluctuations in the solar wind near the Sun where the magnetic field tends to be radially aligned. In this paper, two magnetic-field-aligned solar wind flow intervals during PSP’s first two orbits are analyzed. Observations of these intervals indicate strong signatures of parallel/antiparallel-propagating waves. We utilize multiple analysis techniques to extract the properties of the observed waves in both magnetohydrodynamic (MHD) and kinetic scales. At the MHD scale, outward-propagating Alfvén waves dominate both intervals, and outward-propagating fast magnetosonic waves present the second-largest contribution in the spectral energy density. At kinetic scales, we identify the circularly polarized plasma waves propagating near the proton gyrofrequency in both intervals. However, the sense of magnetic polarization in the spacecraft frame is observed to be opposite in the two intervals, although they both possess a sunward background magnetic field. The ion-scale plasma wave observed in the first interval can be either an inward-propagating ion cyclotron wave (ICW) or an outward-propagating fast-mode/whistler wave in the plasma frame, while in the second interval it can be explained as an outward ICW or inward fast-mode/whistler wave. The identification of the exact kinetic wave mode is more difficult to confirm owing to the limited plasma data resolution. The presence of ion-scale waves near the Sun suggests that ion cyclotron resonance may be one of the ubiquitous kinetic physical processes associated with small-scale magnetic fluctuations and kinetic instabilities in the inner heliosphere.

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Experimental and numerical investigation of plasma parameters in the magnetosheath

MATEC Web of Conferences ◽

10.1051/matecconf/201814503003 ◽

2018 ◽

Vol 145 ◽

pp. 03003

Author(s):

Polya Dobreva ◽

Monio Kartalev ◽

Olga Nitcheva ◽

Natalia Borodkova ◽

Georgy Zastenker

Keyword(s):

Magnetic Field ◽

Solar Wind ◽

Numerical Investigation ◽

Euler Equations ◽

Ideal Gas ◽

Bow Shock ◽

Plasma Parameters ◽

Wind Spacecraft ◽

The Magnetic Field ◽

Good Agreement

We investigate the behaviour of the plasma parameters in the magnetosheath in a case when Interball-1 satellite stayed in the magnetosheath, crossing the tail magnetopause. In our analysis we apply the numerical magnetosheath-magnetosphere model as a theoretical tool. The bow shock and the magnetopause are self-consistently determined in the process of the solution. The flow in the magnetosheath is governed by the Euler equations of compressible ideal gas. The magnetic field in the magnetosphere is calculated by a variant of the Tsyganenko model, modified to account for an asymmetric magnetopause. Also, the magnetopause currents in Tsyganenko model are replaced by numericaly calulated ones. Measurements from WIND spacecraft are used as a solar wind monitor. The results demonstrate a good agreement between the model-calculated and measured values of the parameters under investigation.

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On the probability distribution function of small-scale interplanetary magnetic field fluctuations

Annales Geophysicae ◽

10.5194/angeo-22-3751-2004 ◽

2004 ◽

Vol 22 (10) ◽

pp. 3751-3769 ◽

Cited By ~ 38

Author(s):

R. Bruno ◽

V. Carbone ◽

L. Primavera ◽

F. Malara ◽

L. Sorriso-Valvo ◽

...

Keyword(s):

Magnetic Field ◽

Solar Wind ◽

Robust Statistics ◽

Interplanetary Space ◽

Parametric Instability ◽

Field Vector ◽

Small Scale ◽

Magnetic Fluctuations ◽

Mhd Turbulence ◽

The One

Abstract. In spite of a large number of papers dedicated to the study of MHD turbulence in the solar wind there are still some simple questions which have never been sufficiently addressed, such as: a) Do we really know how the magnetic field vector orientation fluctuates in space? b) What are the statistics followed by the orientation of the vector itself? c) Do the statistics change as the wind expands into the interplanetary space? A better understanding of these points can help us to better characterize the nature of interplanetary fluctuations and can provide useful hints to investigators who try to numerically simulate MHD turbulence. This work follows a recent paper presented by some of the authors which shows that these fluctuations might resemble a sort of random walk governed by Truncated Lévy Flight statistics. However, the limited statistics used in that paper did not allow for final conclusions but only speculative hypotheses. In this work we aim to address the same problem using more robust statistics which, on the one hand, forces us not to consider velocity fluctuations but, on the other hand, allows us to establish the nature of the governing statistics of magnetic fluctuations with more confidence. In addition, we show how features similar to those found in the present statistical analysis for the fast speed streams of solar wind are qualitatively recovered in numerical simulations of the parametric instability. This might offer an alternative viewpoint for interpreting the questions raised above.

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The low-frequency break observed in the slow solar wind magnetic spectra

Astronomy and Astrophysics ◽

10.1051/0004-6361/201935841 ◽

2019 ◽

Vol 627 ◽

pp. A96 ◽

Cited By ~ 16

Author(s):

R. Bruno ◽

D. Telloni ◽

L. Sorriso-Valvo ◽

R. Marino ◽

R. De Marco ◽

...

Keyword(s):

Magnetic Field ◽

Solar Wind ◽

Low Frequency ◽

Slow Solar Wind ◽

Velocity Spectrum ◽

Plasma Parameters ◽

Solar Wind Magnetic Field ◽

Fast Wind ◽

Slow Wind ◽

First Time

Fluctuations of solar wind magnetic field and plasma parameters exhibit a typical turbulence power spectrum with a spectral index ranging between ∼5/3 and ∼3/2. In particular, at 1 AU, the magnetic field spectrum, observed within fast corotating streams, also shows a clear steepening for frequencies higher than the typical proton scales, of the order of ∼3 × 10−1 Hz, and a flattening towards 1/f at frequencies lower than ∼10−3 Hz. However, the current literature reports observations of the low-frequency break only for fast streams. Slow streams, as observed to date, have not shown a clear break, and this has commonly been attributed to slow wind intervals not being long enough. Actually, because of the longer transit time from the Sun, slow wind turbulence would be older and the frequency break would be shifted to lower frequencies with respect to fast wind. Based on this hypothesis, we performed a careful search for long-lasting slow wind intervals throughout 12 years of Wind satellite measurements. Our search, based on stringent requirements not only on wind speed but also on the level of magnetic compressibility and Alfvénicity of the turbulent fluctuations, yielded 48 slow wind streams lasting longer than 7 days. This result allowed us to extend our study to frequencies sufficiently low and, for the first time in the literature, we are able to show that the 1/f magnetic spectral scaling is also present in the slow solar wind, provided the interval is long enough. However, this is not the case for the slow wind velocity spectrum, which keeps the typical Kolmogorov scaling throughout the analysed frequency range. After ruling out the possible role of compressibility and Alfvénicity for the 1/f scaling, a possible explanation in terms of magnetic amplitude saturation, as recently proposed in the literature, is suggested.

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Cassini observations of magnetic holes in the solar wind and Saturn magnetosheath

10.5194/egusphere-egu2020-100 ◽

2020 ◽

Author(s):

Tomas Karlsson ◽

Lina Hadid ◽

Michiko Morooka ◽

Jan-Erik Wahlund

Keyword(s):

Magnetic Field ◽

Solar Wind ◽

Field Strength ◽

Magnetic Field Strength ◽

High Time Resolution ◽

Magnetic Field Direction ◽

Scale Size ◽

Background Magnetic Field ◽

Cycle Dependence ◽

The Magnetic Field

We present the first Cassini observations of magnetic holes on the near-Saturn solar wind and magnetosheath, based on data from the MAG magnetometer. We conclude that magnetic holes (defined as isolated decreases of at least 50% compared to the background magnetic field strength) are common in both regions. We present statistical properties of the magnetic holes, including scale size, depth of the magnetic field reduction, orientation, change in magnetic field direction over the holes, and solar cycle dependence. For magnetosheath magnetic holes, also high-time resolution density measurements from the LP Langmuir probe are available, allowing us to study the anti-correlation of density and magnetic field strength in the magnetic holes. We compare to recent results from MESSENGER observations from Mercury orbit, and finally discuss the possible importance of magnetic holes in solar wind-magnetosphere interaction at Saturn.

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Dispersion relation analysis of turbulent magnetic field fluctuations in fast solar wind

Annales Geophysicae ◽

10.5194/angeo-31-1949-2013 ◽

2013 ◽

Vol 31 (11) ◽

pp. 1949-1955 ◽

Cited By ~ 21

Author(s):

C. Perschke ◽

Y. Narita ◽

S. P. Gary ◽

U. Motschmann ◽

K.-H. Glassmeier

Keyword(s):

Magnetic Field ◽

Solar Wind ◽

High Speed ◽

Energy Transport ◽

Normal Modes ◽

Frequency Dispersion ◽

Dispersion Relations ◽

Wave Number ◽

Magnetic Fluctuations ◽

Speed Solar Wind

Abstract. Physical processes of the energy transport in solar wind turbulence are a subject of intense studies, and different ideas exist to explain them. This manuscript describes the investigation of dispersion properties in short-wavelength magnetic turbulence during a rare high-speed solar wind event with a flow velocity of about 700 km s−1 using magnetic field and ion data from the Cluster spacecraft. Using the multi-point resonator technique, the dispersion relations (i.e., frequency versus wave-number values in the solar wind frame) of turbulent magnetic fluctuations with wave numbers near the inverse ion inertial length are determined. Three major results are shown: (1) the wave vectors are uniformly quasi-perpendicular to the mean magnetic field; (2) the fluctuations show a broad range of frequencies at wavelengths around the ion inertial length; and (3) the direction of propagation at the observed wavelengths is predominantly in the sunward direction. These results suggest the existence of high-frequency dispersion relations partly associated with normal modes on small scales. Therefore nonlinear energy cascade processes seem to be acting that are not described by wave–wave interactions.

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Non-diffusive pitch-angle scattering of a distribution of energetic particles by coherent whistler waves

10.5194/egusphere-egu21-3604 ◽

2021 ◽

Author(s):

Young Dae Yoon ◽

Paul Bellan

Keyword(s):

Magnetic Field ◽

Single Particle ◽

Pitch Angle ◽

Present Theory ◽

Space Physics ◽

Particle Analysis ◽

Angle Scattering ◽

Background Magnetic Field ◽

Particle Simulations ◽

Uniform Background

A recent study and a companion talk [1] showed that an exact rearrangement of the relativistic particle equation of motion under a coherent circularly-polarized electromagnetic wave leads to an equation describing the motion of the &#8220;frequency mismatch&#8221; parameter &#958; under a pseudo-potential &#968;(&#958;). When the particle undergoes a so-called &#8220;two-valley motion&#8221; in &#958;-space, it experiences large changes in &#958; and thus its pitch-angle because &#958; is a function of the particle&#8217;s velocity parallel to the background magnetic field. This single-particle analysis is extended [2] to a distribution of relativistic particles. First, the condition for two-valley motion is derived with parameters relevant to magnetospheric contexts. Single-particle simulations verify that particles which satisfy this condition indeed undergo large pitch-angle fluctuations. Second, assuming a relativistic Maxwellian particle distribution, the fraction of particles that undergo two-valley motion is analytically derived and is numerically verified by Monte-Carlo simulations. A significant fraction (1% - 5%) of the distribution undergoes two-valley motion for typical magnetospheric parameters. For sufficiently fast interactions where a uniform background magnetic field and a constant wave frequency can be assumed, the widely-used second-order trapping theory [3] is shown to be an erroneous approximation of the present theory.&#160;[1] P. M. Bellan, Phys. Plasmas, 20 (4), Art. No. 042117 (2013)[2] Y. D. Yoon and P. M. Bellan, JGR Space Physics, 125 (6), Art. No. e2020JA027796 (2020)[3] D. Nunn, Planet. and Space Sci., 22 (3), 349-378 (1974)&#160;

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Low-frequency Whistler Waves Modulate Electrons and Generate Higher-frequency Whistler Waves in the Solar Wind

The Astrophysical Journal ◽

10.3847/1538-4357/ac2e97 ◽

2021 ◽

Vol 923 (2) ◽

pp. 216

Author(s):

S. T. Yao ◽

Q. Q. Shi ◽

Q. G. Zong ◽

A. W. Degeling ◽

R. L. Guo ◽

...

Keyword(s):

Solar Wind ◽

Electromagnetic Fields ◽

Low Frequency ◽

Space Physics ◽

Lower Hybrid ◽

High Temporal Resolution ◽

Modulation Amplitude ◽

Whistler Waves ◽

Direction Parallel ◽

Background Magnetic Field

Abstract The role of whistler-mode waves in the solar wind and the relationship between their electromagnetic fields and charged particles is a fundamental question in space physics. Using high-temporal-resolution electromagnetic field and plasma data from the Magnetospheric MultiScale spacecraft, we report observations of low-frequency whistler waves and associated electromagnetic fields and particle behavior in the Earth’s foreshock. The frequency of these whistler waves is close to half the lower-hybrid frequency (∼2 Hz), with their wavelength close to the ion gyroradius. The electron bulk flows are strongly modulated by these waves, with a modulation amplitude comparable to the solar wind velocity. At such a spatial scale, the electron flows are forcibly separated from the ion flows by the waves, resulting in strong electric currents and anisotropic ion distributions. Furthermore, we find that the low-frequency whistler wave propagates obliquely to the background magnetic field ( B 0), and results in spatially periodic magnetic gradients in the direction parallel to B 0. Under such conditions, large pitch-angle electrons are trapped in wave magnetic valleys by the magnetic mirror force, and may provide free perpendicular electron energy to excite higher-frequency whistler waves. This study offers important clues and new insights into wave–particle interactions, wave generation, and microscale energy conversion processes in the solar wind.

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Statistical Differences of Magnetic Field Kinks Observed by PSP and WIND

10.5194/egusphere-egu21-14696 ◽

2021 ◽

Author(s):

Chuanpeng Hou ◽

Xingyu Zhu ◽

Rui Zhuo ◽

Jiansen He

Keyword(s):

Magnetic Field ◽

Solar Wind ◽

Radial Velocity ◽

Slow Solar Wind ◽

Number Density ◽

Ion Temperature ◽

Group I ◽

Rotational Discontinuity ◽

Background Magnetic Field ◽

The Magnetic Field

Parker Solar Probe&#8217;s (PSP) observations near the sun show the extensive presence of magnetic field kinks (switchback for large kinks) in the slow solar wind. These kinks are usually accompanied by the enhancement of radial solar wind velocity and ion temperature, increasing or decreasing of number density. The magnetic field kinks have also been observed by WIND and Ulysses to exist near and beyond 1 AU, respectively. In this study, we statistically analyze the property difference of magnetic field kinks observed by PSP and WIND. We obtain the following four points of results. (1) Inside the PSP-kinks, the radial velocity and protons&#8217; temperature increase while density shows enhancement or descent. However, inside the WIND-kinks, besides the slight enhancement of radial velocity, the density and temperature show no obvious change compared with the outside plasma. (2) By employing the Walen-test of kinks, we find that, R components of some PSP-kinks but not all satisfy the rotational discontinuity (RD) features, while the three components of most WIND-kinks well match the RD features. (3) The correlation between magnetic field and velocity inside the PSP-kinks and WIND-kinks does not show significant differences. (4) Both the PSP-kinks and WIND-kinks can be divided into two groups based on the histograms of &#952;Bn, where B is the background magnetic field, and n is the normal direction of kink. The first group (group-I) has &#952;Bn concentrating around 20&#176; for PSP-kinks and 30&#176; for WIND-kinks, indicating that the satellites were crossing the same kinked interplanetary magnetic field (IMF) from the upstream to the downstream. The second group (group-II) has &#952;Bn concentrating around 90&#176; for PSP-kinks and WIND-kinks, suggesting that the satellites were crossing an interface between the unkinked and kinked IMF regions. Our findings help better understanding the nature of kinks and provide the observational basis for testifying models about radial propagation and evolution of magnetic field kinks.

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