Ground state of the thermosphere and substorm time thermospheric response

The thermospheric composition (O/N2 ratio and NO) condition represents the state of the thermosphere. Significant changes in thermospheric composition and neutral wind are often observed during non-storm time (e.g. a weak substorm on May 29, 2023) due to continous energy and momentum input from solar wind to the geospace.  It is challenging to find days when the solar wind impact is minimized and the geospace is at its ground state (super quiet) or undisturbed conditon. After a search of SuperMAG database over two decades (2002-2022), we finally identified a few super quiet intervals with (1) AE or SME < 50 nT, SymH > 0 nT), and (2) low auroral intensities (N₂ LBHS (140-150 nm) < 500 R) over 48 consecutive hours or longer. We report one super quiet interval (November 6-7, 2009) with no O/N2 depletion or NO enhancment which represents a “geopace ground state”.