WawHelioIonMP: A Semiempirical Tool for the Determination of Latitudinal Variation in the Ionization Rate of Interstellar Hydrogen and the Solar Wind

Abstract

The latitudinal structure of the solar wind varies during the cycle of solar activity. Analysis of this variation is important for understanding the solar activity and interpretation of observations of heliospheric energetic neutral hydrogen atoms and interstellar neutral (ISN) atoms inside the heliosphere, which yield information on the heliosphere and its interaction with the interstellar medium. Existing methods of retrieving this information from indirect remote-sensing measurements of phenomena, including the heliospheric backscatter glow and interplanetary scintillations of remote radio sources, are challenging to apply in real time. Here, we propose a method WawHelioIonMP of approximate retrieval of latitudinal profiles of the ionization rates of ISN H using a machine-learning-based interpretation of the helioglow. Assuming that we know their history during two past solar cycles and have observations of the helioglow for close-to-circumsolar circles with a radius close to 90°, we derive statistically an algebraic relation between the ionization profiles and lightcurves. With the relation reversed, we are then able to derive the ionization rate profiles based on observed light curves, such as those planned for the GLObal solar Wind Structure (GLOWS) experiment on the forthcoming NASA mission Interstellar Mapping and Acceleration Probe (IMAP). The application of this method is straightforward and rapid because complex simulations are no longer needed. We present the method of retrieval of the profiles of the ionization rates, leaving the discussion of details of the decomposition of the retrieved ionization rate profiles into profiles of the solar wind speed and density to a future paper.

Keywords

• Solar wind
• Principal component analysis
• Heliosphere
• Solar extreme ultraviolet emission