Lifetimes of High-Degree p Modes in the Quiet and Active Sun

TL;DR

This study investigates how the lifetimes of high-degree solar p-modes vary with the solar activity cycle, revealing that lifetimes decrease with increased activity, especially in active regions, with smaller variations in quiet regions.

Contribution

It provides the first detailed analysis of high-degree p-mode lifetime variations across different solar activity phases in both active and quiet regions.

Findings

Lifetimes decrease by about 13% from solar minimum to maximum in active regions.

Lifetimes in quiet regions decrease by approximately 4-10% over the cycle.

Lifetimes are longer when active regions are avoided.

Abstract

We study variations of the lifetimes of high-degree solar p-modes in the quiet and active Sun with the solar activity cycle. The lifetimes in the degree range 300 - 600 and frequency 2.5 - 4.5 mHz were computed from SOHO/MDI data in an area including active regions and quiet Sun using the time-distance technique. We applied our analysis to the data in four different phases of solar activity: in 1996 (at minimum), 1998 (rising phase), 2000 (at maximum) and 2003 (declining phase). The results from the area with active regions show that the lifetime decreases as activity increases. The maximal lifetime variations are between solar minimum in 1996 and maximum in 2000; the relative variation averaged over all mode degree values and frequencies is a decrease of about 13%. The lifetime reductions relative to 1996 are about 7% in 1998 and about 10% in 2003. The lifetime computed in the quiet region still decreases with solar activity although the decrease is smaller. On average, relative to 1996, the lifetime decrease is about 4% in 1998, 10% in 2000 and 8% in 2003. Thus, measured lifetime increases when regions of high magnetic activity are avoided. Moreover, the lifetime computed in quiet regions also shows variations with activity cycle.