In agreement with K10, we showed that the H Lyman α transit observations (Vidal-Madjar et al., 2003, 2004; Ben-Jaffel, 2007, 2008; Ben-Jaffel and Hosseini, 2010) can be fitted with a layer of H in the thermosphere that is described by three simple parameters. These are the pressure at the bottom of the H layer, the mean temperature in the thermosphere, and a cutoff level due to ionization. The most important parameters are the pressure at the lower boundary and the mean temperature. Because H is the dominant species in the thermosphere, the data can be used to estimate the temperature of the thermosphere. Choosing a lower boundary pressure of 1 μbar based on the location of the H2/H dissociation front in recent photochemical models (Moses et al., 2011) and observational constraints (France et al., 2010), we estimated a mean temperature of about 8250 K in the thermosphere below 3Rp. However, the uncertainty of the observations is large, and the 1σ upper and lower limits on this temperature are approximately 6000 K and 11,000 K, respectively.4
lower boundar
pressure
1 μbar
μbar
thermosphere below 3Rp
temperature
about 8250 K
K
thermosphere below 3Rp
temperature
approximately 6000 K
K
thermosphere below 3Rp
temperature
11,000 K
K