(Poster) Cutoff periods of slow magnetoacoustic gravity waves in a stratified solar atmosphere

ANDREA COSTA; SIEYRA, M V; ERNESTO ZURBRIGGEN

San Juan

Congreso; Towards Future Research on Space Weather: Concepts and Tools (FRESWED); 2019

IAFE, ICATE, etc

Assuming the thin flux tube model we study slow magnetoacoustic gravity waves (cutoff periods) across the solar transition region, from the base of the solar chromosphere to the lower corona. We introduce an analytical model that contemplates the temperature variation across the transition region, with a corresponding variation of the mean atomic mass considering also different intensities and inclination curves of the magnetic field, in a gravitational stratified atmosphere in hydrostatic equilibrium (g=cte). Generally, at all heights the slow magnetoacoustic cutoff period is significantly lower than the corresponding acoustic one [3]. Changes in the magnetic field intensity move the period profiles to higher coronal levels and at large coronal heights the acoustic and slow magnetoacoustic periods converge.Within the approximations assumed by the thin flux tube model, we also show that almost straight magnetic field regions (e.g. sunspot umbras) are associated with low periods (lower than 5 min) independently of the magnetic field strength and the solar atmospheric level. The periods associated with inclined magnetic field lines increase with increasing solar atmospheric height. While the period values are smaller than 5 min at the chromospheric level they reach up to 80 min at the coronal level.