The Magnetic Field of a Coronal Hole in the Heliosphere: The Inverse Square Law

Abstract

In this paper, we show that inside the magnetic force tube formed by the open field of the coronal hole (CH), the magnetic field (MF) decreases with the distance from the Sun according to the inverse square law. In the study, we select such time periods when there were no active formations on the solar disk, with the exception of CHs (period 2006–2009, the minimum phase of the 23rd activity cycle). The main result of the study, the inverse square law, was obtained by comparing the duration of the CH passage through the central meridian with the duration of the increase in the SW velocity caused by these CHs in the Earth’s orbit. The ratio of the two indicated time intervals turns out to be very close to unity. The data from SOHO (Solar and Heliospheric Observatory), GGS WIND (Global Geospace Science Program WIND), and ACE (Advanced Composition Explorer) spacecraft were used. A special computer program was used to digitize the CH coordinates on daily EIT images at the λ195 Å (SOHO) line and calculate the CH areas in the sector affecting the SW parameters (ellipse 0.6R_o by 0.3R_o). Based on the inverse square law, MF (~2 G) and the particle flux density (~1.2 × 10¹³ particles/s cm²) on the solar surface at the base of 15 studied CHs were calculated using the SW parameters near the Earth’s orbit.