Period ratios for standing kink and sausage modes in magnetized structures with siphon flow on the Sun

• 来源期刊: 天文和天体物理学研究
• 年，卷（期）: 2016,（6）
• 页码范围: 69-84
• 页数: 16页
• 语种: 英文
• DOI: 10.1088/1674-4527/16/6/092

摘要

Standing oscillations with multiple periods have been found in a number of atmospheric structures on the Sun.The ratio of the period of the fundamental to twice the one of its first overtone,P1/2P2,is important in applications of solar magneto-seismology.We examine how field-aligned flows impact P1/2P2 of standing modes in solar magnetic cylinders.For coronal loops,the flow effects are significant for both fast kink and sausage modes.For kink modes,they reduce P1/2P2 by up to 17％ relative to the static case even when the density contrast between the loop and its surroundings approaches infinity.For sausage modes,the reduction in P1/2P2 due to flow is typically (～＜) 5.5％ compared with the static case.However,the threshold aspect ratio,only above which can trapped sausage modes be supported,may increase dramatically with the flow magnitude.For photospheric tubes,the flow effect on P1/2P2 is not as strong.However,when applied to sausage modes,introducing field-aligned flows offers more possibilities in interpreting the multiple periods that have recently been measured.We conclude that field-aligned flows should be taken into account to help better understand what causes the departure of P1/2P2 from unity.