Do Inner Planets Modulate the Space Environment of the Earth?

Abstract

Variabilities in the solar wind cause disturbances throughout the heliosphere on all temporal and spatial scales, which leads to changeable space weather. As a view of space weather forecasting, in particular, it is important to know direct and indirect causes modulating the space environment near the Earth in advance. Recently, there are discussions on a role of the interaction of the solar wind with Mercury in affecting the solar wind velocity in the Earth's neighborhood during its inferior conjunctions. In this study we investigate a question of whether other parameters describing the space environment near the Earth are modulated by the inner planets' wake, by examining whether the interplanetary magnetic field and the proton density in the solar wind observed by the Advanced Composition Explorer (ACE) spacecraft, and the geomagnetic field via the Dst index and Auroral Electrojet index (AE index) are dependent upon the relative position of the inner planets. We find there are indeed apparent variations. For example, the mean variations of the geomagnetic fields measured in the Earth's neighborhood apparently have varied with a timescale of about 10 to 25 days. Those variations in the parameters we have studied, however, turn out to be a part of random fluctuations and have nothing to do with the relative position of inner planets. Moreover, it is found that variations of the proton density in the solar wind, the Dst index, and the AE index are distributed with the Gaussian distribution. Finally, we point out that some of properties in the behavior of the random fluctuation are to be studied.

Statistical Properties of Geomagnetic Activity Indices and Solar Wind Parameters

“…The present analysis is carried out using the superimposed epoch method for 10 parameters in total as listed in the next section (Kim & Chang 2014). To apply the technique for a selected parameter, we first chop the entire data-string of time series into several substrings with an appropriate length.…”

Spectral Analysis of Geomagnetic Activity Indices and Solar Wind Parameters

“…Secondly, we attempt to search for any signatures of influence on the space environment near the Earth by inner planets revolving around the Sun (see, Kim & Chang 2014). Supposed that the inner planets make its shadow up to the Earth's orbit at 1 AU from the Sun and disturb the Earth's space environment, there must be a periodic perturbative signal in geomagnetic activity data corresponding to the synodic period of inner planets.…”