Reconstruction of Helio-Latitudinal Structure of the Solar Wind Proton Speed and Density

Abstract

The modeling of the heliosphere requires continuous three-dimensional solar wind data. The in-situ out-of-ecliptic measurements are very rare, so that other methods of solar wind detection are needed. We use the remote-sensing data of the solar wind speed from observations of interplanetary scintillation (IPS) to reconstruct spatial and temporal structures of the solar wind proton speed from 1985 to 2013. We developed a method of filling the data gaps in the IPS observations to obtain continuous and homogeneous solar wind speed records. We also present a method to retrieve the solar wind density from the solar wind speed, utilizing the invariance of the solar wind dynamic pressure and energy flux with latitude. To construct the synoptic maps of the solar wind speed we use the decomposition into spherical harmonics of each of the Carrington rotation map. To fill the gaps in time we apply the singular spectrum analysis to the time series of the coefficients of spherical harmonics. We obtained helio-latitudinal profiles of the solar wind proton speed and density over almost three recent solar cycles. The accuracy in the reconstruction is, due to computational limitations, about 20 %. The proposed methods allow us to improve the spatial and temporal resolution of the model of the solar wind parameters presented in our previous paper (Sokół et al., Solar Phys. 285, 167, 2013) and give a better insight into the time variations of the solar wind structure. Additionally, the solar wind density is reconstructed more accurately and it fits better to the in-situ measurements from Ulysses.

Tracking the Solar Cycle Through Ibex Observations of Energetic Neutral Atom Flux Variations at the Heliospheric Poles

“…The lowenergy ENA flux varies with changes in the SW dynamic pressure over the course of the solar cycle, which is generally in phase with the sunspot number, whereas the high-energy Figure 9. Heliolatitude vs.time map of the SW speed reconstructed from interplanetary scintillation (IPS) data and OMNI data, as described in Sokół et al (2015). Figure 10.…”

“…Because the SW dynamic pressure is regarded as an SW invariant with heliolatitude (McComas et al . 2008), we use the dynamic pressure calculated from the ecliptic OMNI-2 archive (King & Papitashvili 2005) as a proxy for P 1 au in the polar regions (see also thediscussion in Sokół et al 2013 andSokół et al 2015). The upper plot is for the north pole,and the lower isfor the south pole.…”

“…These velocity evolution maps are based on interplanetary scintillation (IPS) data collected by the Institute for Space-Earth Environmental Research (ISEE, formerly STEL) at Nagoya University, Japan (Tokumaru et al 2012), and are routinely used by the IBEX team as input into the ENA survival probability model Sokół et al 2013Sokół et al , 2015. Here, we present the SW speed reconstruction to compare it to the PCH area.…”

Response times of Cassini/INCA > 5.2 keV ENAs and Voyager ions in the heliosheath over the solar cycle

“…The solar wind energy flux and density at 1 AU show a coherent decay with time (peak to basin ratio of~2) up to early 2010 and a recovery in both quantities thereafter (e.g. Figure 9 in [41]). This, as expected (e.g.…”

“…Recent studies [41] have undertaken a significant effort to calculate the solar wind parameters as a function of time for the in-ecliptic solar wind data at 1 AU from the OMNI database. The solar wind energy flux and density at 1 AU show a coherent decay with time (peak to basin ratio of~2) up to early 2010 and a recovery in both quantities thereafter (e.g.…”