From Hydrogen backscatter glow to solar wind structure – how we do it with IMAP/GLOWS

Solar wind features a latitudinal structure that evolves during the solar activity cycle. The only in-situ measurements of the solar wind speed and density available so far were performed by Ulysses at the turn of the 20th and 21st centuries. They showed the general behavior of the solar wind speed and density. However, details of possible asymmetries and regular structure evolution at shorter time scales could not be established because the measurements were performed in-situ along a highly elliptical orbit with a period of the order of half of the solar cycle.

Complementary methods of monitoring the solar wind latitudinal profiles include remote-sensing observations such as hydrogen Lyman-α backscatter glow observations. Helioglow maps observed by SOHO/SWAN suggested that the solar wind flux temporarily features flux maxima at mid-latitudes.

Insight from Ulysses resulted in a hypothesis that the energy flux of solar wind is latitudinally invariant, which cannot be verified without additional observations. A confirmation of this invariance would be an important milestone in the understanding of the solar wind emission mechanism and would provide a handy tool supporting the retrieval of the solar wind structure from observations of the helioglow.

GLObal solar Wind Structure (GLOWS) is a Lyman-α photometer onboard Interstellar Mapping and Acceleration Probe (IMAP), dedicated to helioglow observations optimized for the retrieval of the solar wind structure. We present how GLOWS observations will be used to infer the structure of the solar wind and to verify the hypothesis of latitudinal invariance of the solar wind energy flux.