Winners announced for the Space Weather Competition. Visit for details.

Thermosphere response to one-day, intense EUV-solar flux increase

Carine Briand - Observatoire de Paris-PSL; Kelsey Doerksen - PLANET, United States; Florent Deleflie - Observatoire de Paris-PSL, France

Session:  Thermosphere-Ionosphere Interactions and Effects


EUV solar flux is known to play a crucial role in the thermosphere equilibrium during periods of low solar activity. Being the primary heating source of the atmosphere, it induces fluctuations on different time scales, from the solar rotation to seasonal, as well as diurnal local time and latitude dependence.

During periods of solar activity, geomagnetic activity and X-flux become the main sources of density perturbations. They act on shorter time scales (days to hours). The large X-flux increase dominates the other EM-radiation and masks their possible role. Models have been used to investigate the role of EUV irradiance on long time scales. We present results on the role of EUV-flux variation on the intermediate time scales of one to two days, from observational data.

Four intense and rather long duration (1 to 2 days) EUV-enhancements, isolated from geomagnetic storms and large X-flares, have been detected during the period 2002-2010. They were observed simultaneously from the two channels of SOHO/SEM. The neutral density disturbances have been studied from CHAMP and GRACE measurements. We show that these events, although rare, can produce noticeable (>20%) density perturbation. Minor geomagnetic storms are also often observed. We discuss the possible links between them.

Approaching deadlines:

Registration opens:

16 July 2020

Abstract submission opens:

16 July 2020

European Space Weather Medals:

6 September 2020

Registration deadline:

25 September 2020

Registration deadline: [extended]

10 October 2020

Abstract submission deadline:

4 September 2020