预测由于内旋太阳周期变化引起的全球尺度太阳Rossby模的频率变化
Predicting frequency changes of global-scale solar Rossby modes due to solar cycle changes in internal rotation
摘要:
上下文在过去的两个太阳活动周中,人们在太阳上观测到了大尺度的赤道Rossby模。目的。我们研究了时变纬向流对Rossby模式频率的影响。方法.一阶微扰理论的方法是用来获得预期的模式频率的变化,由于在内部旋转速率的扰动的表达式。结果利用日震反演的时变旋转,我们预测了Rossby模频率的变化,方位角阶数从m = 1到m = 15,在过去的两个太阳活动周。对于m = 1模式,峰-峰频率变化小于1 nHz,随m增长,并且对于m = 15达到25 nHz。结论.由于有限的模式寿命的模式频率上的观测不确定性,我们发现,预测的频率偏移接近检测的极限。
英文摘要:
Context. Large-scale equatorial Rossby modes have been observed on the Sun over the last two solar cycles. Aims. We investigate the impact of the time-varying zonal flows on the frequencies of Rossby modes. Methods. A first-order perturbation theory approach is used to obtain an expression for the expected shift in the mode frequencies due to perturbations in the internal rotation rate. Results. Using the time-varying rotation from helioseismic inversions we predict the changes in Rossby mode frequencies with azimuthal orders from m = 1 to m = 15 over the last two solar cycles. The peak-to-peak frequency change is less than 1 nHz for the m = 1 mode, grows with m, and reaches 25 nHz for m = 15. Conclusions. Given the observational uncertainties on mode frequencies due to the finite mode lifetimes, we find that the predicted frequency shifts are near the limit of detectability.
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