Temporal variation of the 3-micron hydrocarbon emissions at the 8-micron north polar hot spot of Jupiter: Comparison with solar wind activity

Abstract

We have obtained Gemini/GNIRS 3.3-3.4 μm spectra of Jupiter at 65^o North latitude over a range of longitudes roughly centered on the 8-μm CH₄ north polar hot spot (8CNPHS). The spectra were measured on four occasions during a four-month period in 2018, in order to search for variability of the 3-μm emissions of CH₄ and C₂H₆. The observed locations of the brightest spots of the C₂H₆ and CH₄ emissions at 65^oN differed in longitude typically by 20^o during this period. The peak emission intensities of these species showed large variations, with the highest intensities 3-4 times greater than the lowest intensities. In addition, the brightest 3-μm CH₄ emissions and hottest temperatures at the 8CNPHS were significantly less than those at the 3-μm CH₄ north polar hot spot (3CNPHS, Kim et al., 2015). Recently, Sinclair et al. (2019) reported a coincidence between solar wind dynamical pressure and the 8-μm brightening of the 8CNPHS. In contrast, we find lack of correlation in our data between the 3-μm hydrocarbon emission intensities at the 8CNPHS and the solar wind strength. We also find lack of correlation between H₃⁺ intensities and the solar wind strength during the period. However, due to the limited observational data, it is too early to conclude whether this lack of correlation indicates that the solar wind activity induced no significant changes in local temperatures (<40 K) and/or mixing ratios of these molecules. Our observing period was close to the historic grand solar minimum. The detailed influence of the solar activity on the 3 and 8 μm brightness at the 8CNPHS is not quantitatively understood at the present time.