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30 Oct NASA ROSES 2015

Posted at 12:45h in Projects by
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NASA ROSES 2015

Title: Spectral analysis of the plasma and magnetic fields at the edge of the heliosphere using Voyager data

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We proposed to characterize the turbulence in the solar wind, heliosheath, and local interstellar medium. We are developing an advanced spectral analysis technique based on several independent data gap reconstruction methods. We consider a spectral result reliable if three of these independent analysis methods give the same answer. These techniques will be used to characterize the turbulence, in some regions for the first time and in some regions over a much larger frequency range (by orders of magnitude) than previously possible. In addition to the analysis of current data, this work will prepare the ground for the spectral analysis of LISM plasma data when V2 crosses the heliopause. The Voyagers (V1, V2) are the only operating spacecraft providing us with in situ data from the outermost part of heliosphere. The inner heliosheath (IHS) is the region of space between the termination shock (TS) and the heliopause (HP). The HP is a tangential discontinuity that separates the solar wind (SW) from the local interstellar medium (LISM).

For more details see:

The structure of magnetic turbulence in the Heliosheath region observed by Voyager 2 at 106 AU
Magnetic Turbulence Spectra and Intermittency in the Heliosheath and in the Local Interstellar Medium 
Voyager 2 solar plasma and magnetic field spectral analysis for intermediate data sparsity
 

Figure 1. Voyager 2 data considered in the present study, observation period 2013.824-2016.0. Top to bottom: the magnetic- field magnitude B =|B|; the azimuthal angle = tan ^-1(BT /BR)

Figure 2. Power spectral density of magnetic field fluctuations, anisotropy and compressibility

Figure 3.  Structure functions of magnetic field increments

Figure 4. Probability density functions of the plasma velocity and magnetic field fluctuations. (a) Normalized probability density function of the angle 𝜓 between the radial direction and the local velocity (red line) and magnetic (blue line) fields. The magnetic field is generally tilted 85 to 105∘ with respect to the radial direction. (b–d) Normalized probability density function of the plasma velocity and magnetic field components in the radial (Figure 2b), tangential (Figure 2c), and normal (Figure 2d) directions, and of their module (Figure 2e), normalized as in equation (1). For more details see Journal of Geophysical Research: Space Physics 2015