Kavli Affiliate: John D. Richardson

| First 5 Authors: Luca Gallana, Federico Fraternale, Michele Iovieno, Sophie M. Fosson, Enrico Magli

| Summary:

The Voyager probes are the furthest, still active, spacecraft ever launched

from Earth. During their 38-year trip, they have collected data regarding solar

wind properties (such as the plasma velocity and magnetic field intensity).

Unfortunately, a complete time evolution of the measured physical quantities is

not available. The time series contains many gaps which increase in frequency

and duration at larger distances. The aim of this work is to perform a spectral

and statistical analysis of the solar wind plasma velocity and magnetic field

using Voyager 2 data measured in 1979, when the gaps/signal ratio is of order

of unity. This analysis is achieved using four different data reconstruction

techniques: averages on linearly interpolated subsets, correlation of linearly

interpolated data, compressed sensing spectral estimation, and maximum

likelihood data reconstruction. With five frequency decades, the spectra we

obtained have the largest frequency range ever computed at 5 astronomical units

from the Sun; spectral exponents have been determined for all the components of

the velocity and magnetic field fluctuations. Void analysis is also useful in

recovering other spectral properties such as integral scales (see for instance

Table 4) and, if the confidence level of the measurements is sufficiently high,

the decay variation in the small scale range due, for instance, to dissipative

effects.

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