UNUSUAL TRENDS IN SOLAR P-MODE FREQUENCIES DURING THE CURRENT EXTENDED MINIMUM

Journal Article · Wed Mar 10 04:00:00 EST 2010 · Astrophysical Journal Letters

DOI:https://doi.org/10.1088/2041-8205/711/2/L84; COUNTRY OF INPUT: INTERNATIONAL ATOMIC ENERGY AGENCY (IAEA)· OSTI ID:21305113

Tripathy, S C; Jain, K; Hill, F

We investigate the behavior of the intermediate-degree mode frequencies of the Sun during the current extended minimum phase to explore the time-varying conditions in the solar interior. Using contemporaneous helioseismic data from the Global Oscillation Network Group (GONG) and the Michelson Doppler Imager (MDI), we find that the changes in resonant mode frequencies during the activity minimum period are significantly greater than the changes in solar activity as measured by different proxies. We detect a seismic minimum in MDI p-mode frequency shifts during 2008 July-August but no such signature is seen in mean shifts computed from GONG frequencies. We also analyze the frequencies of individual oscillation modes from GONG data as a function of latitude and observe a signature of the onset of the solar cycle 24 in early 2009. Thus, the intermediate-degree modes do not confirm the onset of the cycle 24 during late 2007 as reported from the analysis of the low-degree Global Oscillations at Low Frequency frequencies. Further, both the GONG and MDI frequencies show a surprising anti-correlation between frequencies and activity proxies during the current minimum, in contrast to the behavior during the minimum between cycles 22 and 23.

• OSTI ID: 21305113
• Journal Information: Astrophysical Journal Letters, Journal Name: Astrophysical Journal Letters Journal Issue: 2 Vol. 711; ISSN 2041-8205
• Country of Publication: United States
• Language: English

Related Subjects

79 ASTRONOMY AND ASTROPHYSICS
99 GENERAL AND MISCELLANEOUS
OSCILLATION MODES
OSCILLATIONS
SOLAR ACTIVITY
SOLAR CYCLE
SUN