scholarly journals Nature of Large-Scale Solar Magnetic Field and Complexity of HCS as Observed in Interplanetary Plasma

1990 ◽  
Vol 142 ◽  
pp. 343-344
Author(s):  
T E Girish ◽  
S R Prabhakaran Nayar
Keyword(s):  
Magnetic Field ◽  
Solar Wind ◽  
Large Scale ◽  
Solar Magnetic Field ◽  
Solar Rotation ◽  
Solar Wind Plasma ◽  
Heliospheric Current Sheet ◽  
The North ◽  
Interplanetary Plasma ◽  
South Asymmetry

The properties of the interplanetary plasma and magnetic field near 1 AU is determined by the nature of large-scale solar magnetic field and the associated structure of the heliospheric current sheet (HCS). Magnetic multipoles often present near the solar equator affect the solar wind plasma and magnetic field (IMF) near earth's orbit. The observation of four or more IMF sectors per solar rotation and the north-south asymmetry in the HCS are observational manifestations of the influence of solar magnetic multipoles, especially the quadrupole on the interplanetary medium (Schultz, 1973; Girish and Nayar, 1988). The solar wind plasma is known to be organised around the HCS. In this work, we have investigated the possibility of inferring i) the relative dipolar and quadrupolar heliomagnetic contributions to the HCS geometry from the observation of four sector IMF structure near earth and ii) the properties of the north-south asymmetry in HCS geometry about the heliographic equator from IMF and solar wind observations near 1 AU.

HelioSwarm: The Nature of Turbulence in Space Plasmas

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

<p>Recently selected for phase A study for NASA’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.  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. </p>

A Turbulent Heliosheath Driven by Rayleigh Taylor Instability

2021 ◽  
Author(s):  
Merav Opher ◽  
James Drake ◽  
Gary Zank ◽  
Gabor Toth ◽  
Erick Powell ◽  
...  
Keyword(s):  
Magnetic Field ◽  
Solar Wind ◽  
Large Scale ◽  
Neutral Atom ◽  
Solar Magnetic Field ◽  
Characteristic Time Scale ◽  
Rayleigh Taylor Instability ◽  
Scale Turbulence ◽  
Magnetohydrodynamic Simulations ◽  
Rt Instability

Abstract The heliosphere is the bubble formed by the solar wind as it interacts with the interstellar medium (ISM). Studies show that the solar magnetic field funnels the heliosheath solar wind (the shocked solar wind at the edge of the heliosphere) into two jet-like structures1-2. Magnetohydrodynamic simulations show that these heliospheric jets become unstable as they move down the heliotail1,3 and drive large-scale turbulence. However, the mechanism that produces of this turbulence had not been identified. Here we show that the driver of the turbulence is the Rayleigh-Taylor (RT) instability caused by the interaction of neutral H atoms streaming from the ISM with the ionized matter in the heliosheath (HS). The drag between the neutral and ionized matter acts as an effective gravity which causes a RT instability to develop along the axis of the HS magnetic field. A density gradient exists perpendicular to this axis due to the confinement of the solar wind by the solar magnetic field. The characteristic time scale of the instability depends on the neutral H density in the ISM and for typical values the growth rate is ~ 3 years. The instability destroys the coherence of the heliospheric jets and magnetic reconnection ensues, allowing ISM material to penetrate the heliospheric tail. Signatures of this instability should be observable in Energetic Neutral Atom (ENA) maps from future missions such as IMAP4. The turbulence driven by the instability is macroscopic and potentially has important implications for particle acceleration.

scholarly journals Time Evolution of the Large-Scale Solar Magnetic Field

1971 ◽  
Vol 43 ◽  
pp. 588-594 ◽  
Author(s):  
Martin D. Altschuler ◽  
Gordon Newkirk ◽  
Dorothy E. Trotter ◽  
Robert Howard
Keyword(s):  
Magnetic Field ◽  
Time Evolution ◽  
Large Scale ◽  
Solar Magnetic Field ◽  
Magnetic Polarity ◽  
Zonal Harmonic ◽  
The North

The six years of data from the Mt. Wilson Magnetic Atlas were analyzed in terms of surface harmonics. Between 1959 and 1962 the dominant harmonic corresponded to a dipole lying in the plane of the equator (2 sectors). There was also a significant zonal harmonic in which both solar poles had the same magnetic polarity, opposite to that at the equator. From the end of 1962 through 1964, the harmonic corresponding to 4 sectors was dominant. In 1965 and 1966, the harmonic of the north-south dipole became significant.

scholarly journals Sector Structure of the Solar Magnetic Field

1971 ◽  
Vol 43 ◽  
pp. 744-753 ◽  
Author(s):  
John M. Wilcox
Keyword(s):  
Magnetic Field ◽  
Large Scale ◽  
Solar Magnetic Field ◽  
Photospheric Magnetic Field ◽  
The Other ◽  
The Sun ◽  
Sector Structure ◽  
Sector Boundary ◽  
The North

The solar sector structure consists of a boundary in the north-south direction such that on one side of the boundary the large-scale weak photospheric magnetic field is predominantly directed out of the Sun, and on the other side of the boundary this field is directed into the Sun. The region westward of a solar sector boundary tends to be unusually quiet and the region eastward of a solar sector boundary tends to be unusually active. This tendency is discussed in terms of flares, coronal enhancements, plage structure and geomagnetic response.

scholarly journals Satellite observations of currents and waves in space plasmas

1988 ◽  
Vol 6 (3) ◽  
pp. 503-511 ◽  
Author(s):  
T. A. Potemra ◽  
M. J. Engebretson ◽  
L. J. Zanetti ◽  
R. E. Erlandson ◽  
P. F. Bythrow
Keyword(s):  
Magnetic Field ◽  
Solar Wind ◽  
Geomagnetic Field ◽  
Large Scale ◽  
Field Experiments ◽  
Outer Space ◽  
Solar Wind Plasma ◽  
Field Configuration ◽  
The Earth ◽  
Field Lines

When viewed from outer space, the earth's magnetic field does not resemble a simple dipole, but is severely distorted into a comet-shaped configuration by the continuous flow of solar wind plasma. A complicated system of currents flows within this distorted magnetic field configuration called the ‘magnetosphere’ (See figure 1). For example, the compression of the geomagnetic field by the solar wind on the dayside of the earth is associated with a large-scale current flowing across the geomagnetic field lines, called the ‘Chapman-Ferraro’ or magnetopause current. The magnetospheric system includes large-scale currents that flow in the ‘tail’, the ring current that flows at high altitudes around the equator of the earth, field-aligned ‘Birkeland’ currents that flow along geomagnetic field lines into and away from the two auroral regions, and a complex system of currents that flows completely within the layers of the ionosphere, the earth's ionized atmosphere. The intensities of these various currents reach millions of amperes and are closely related to solar activity. The geomagnetic field lines can also oscillate, like giant vibrating strings, at specified resonant frequencies. The effects of these vibrations, sometimes described as ‘standing Alfvén waves’, have been observed on the ground in magnetic field recordings dating back to the beginning of the century. Observations of currents and waves with satellite-borne magnetic field experiments have provided a new perspective on the complicated plasma processes that occur in the magnetosphere. Some of the new observations are described here.

scholarly journals Compressive fluctuations in the solar wind and their polytropic index

1996 ◽  
Vol 14 (5) ◽  
pp. 510-517 ◽  
Author(s):  
B. Bavassano ◽  
R. Bruno ◽  
H. Rosenbauer
Keyword(s):  
Magnetic Field ◽  
Solar Wind ◽  
Solar Rotation ◽  
Polytropic Index ◽  
Constant Density ◽  
The Sun ◽  
Thermal Pressure ◽  
Fast Wind ◽  
Pressure Equilibrium ◽  
Interplanetary Plasma

Abstract. Magnetohydrodynamic compressive fluctuations of the interplanetary plasma in the region from 0.3 to 1 AU have been characterized in terms of their polytropic index. Following Chandrasekhar's approach to polytropic fluids, this index has been determined through a fit of the observed variations of density and temperature. At least three different classes of fluctuations have been identified: (1) variations at constant thermal pressure, in low-speed solar wind and without a significant dependence on distance, (2) adiabatic variations, mainly close to 1 AU and without a relevant dependence on wind speed, and (3) variations at nearly constant density, in fast wind close to 0.3 AU. Variations at constant thermal pressure are probably a subset of the ensemble of total-pressure balanced structures, corresponding to cases in which the magnetic field magnitude does not vary appreciably throughout the structure. In this case the pressure equilibrium has to be assured by its thermal component only. The variations may be related to small flow-tubes with approximately the same magnetic-field intensity, convected by the wind in conditions of pressure equilibrium. This feature is mainly observed in low-velocity solar wind, in agreement with the magnetic topology (small open flow-tubes emerging through an ensemble of closed structures) expected for the source region of slow wind. Variations of adiabatic type may be related to magnetosonic waves excited by pressure imbalances between contiguous flow-tubes. Such imbalances are probably built up by interactions between wind flows with different speeds in the spiral geometry induced by the solar rotation. This may account for the fact that they are mainly found at a large distance from the sun. Temperature variations at almost constant density are mostly found in fast flows close to the sun. These are the solar wind regions with the best examples of incompressible behaviour. They are characterized by very stable values for particle density and magnetic intensity, and by fluctuations of Alfvénic type. It is likely that temperature fluctuations in these regions are a remnant of thermal features in the low solar atmosphere. In conclusion, the polytropic index appears to be a useful tool to understand the nature of the compressive turbulence in the interplanetary plasma, as far as the frozen-in magnetic field does not play a crucial role.

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