Lowdegree Helioseismology with AIA R Howe F Hill

Low-degree Helioseismology with AIA R. Howe F. Hill, R. Komm, A. -M. Broomhall, W. J. Chaplin, Y. Elsworth

Introduction � AIA aboard SDO is best known for spectacular coronal images, BUT … � AIA’s 4500 (Visible continuum), 1700 (UV continuum), 1600 (CIV) bands are sensitive to helioseismic modes. � We can use the DATAMEAN keyword to form an l=0 time series without exporting the images. � Results can be compared with HMI and Bi. SON observations.

Data: Sample Images 4500 1700 1600

Querying the JSOC Database

Database query result

Data series � Available data series for AIA are: ◦ aia_test. synoptic: May 1 -11, 18 -20. 10242 images, mean cadence 90 s for 1600, 1700, 4500. ◦ aia_test. synoptic 2 has slower cadence (mean 120 s for 1600, 110 s for 1700, 103 s for 4500) from May 20. ◦ Series aia_test. lev 1 has full cadence from June 09. ◦ 4500 only at 1 h from June 5. � For HMI we use hmi_test. V_45 s and hmi_test. Ic_45 s from May 1. � Bi. SON 0 -d time series, 40 s cadence, May 1 -11. � Concentrate on May 1 -11 (“Period 1”) and June 10 -26 (“Period 2”).

Issues for the analysis � The data release is still in “beta testing” phase: coverage and cadence are irregular. � Ultraviolet channels are sensitive to flares. � HMI data have strong diurnal variation (mostly observer motion, with contribution from nonlinear calibration. ) � Data are interpolated to regular cadence (60 s for AIA, 45 s for HMI), detrended with 15 minute moving mean, and have spikes rejected.

AIA 1600 (lev 1_test. synoptic[2])

AIA 1600 (lev 1_test)

AIA 1700 (lev 1_test. synoptic[2])

AIA 1700 (lev 1_test)

AIA 4500 (lev 1_test. synoptic[2] )

Bi. SON V

HMI V (55 days)

HMI Continuum Intensity (55 days)

Comparisons with HMI velocity – period 1

Comparisons with HMI velocity – period 1

Comparisons with HMI velocity – period 1

Comparisons with HMI velocity – period 1

Comparison with HMI V: period 2

Comparison with HMI V: second period

Comparison with HMI V: period 2

Comparison with HMI V: second period

Comparison with HMI V: second period

Correlation with HMI V (period 1)

Correlation with HMI V (period 2)

Spectral Comparison: HMI V vs AIA 1700 (period 2)

Spectral Comparison: HMI V vs AIA 1700 (period 2)

HMI V vs Bi. SON power spectra

Discussion and Conclusions � AIA 1600 and 1700 bands (at full cadence) look promising for helioseismology, though slightly noisier than HMI velocity. ◦ Slight phase difference from velocity signal. ◦ May have slightly less power in low-frequency modes, more in high-frequency, than velocity data. ◦ Little or no granulation noise. � HMI velocity has very good signal/noise. � Longer stretches of high-cadence data will be needed to establish the detailed characteristics of the ultraviolet acoustic power spectrum.

Acknowledgments � SDO data courtesy SDO (NASA) and the AIA and HMI consortia. � Bi. SON is operated by the High Resolution Optical Spectroscopy group of the School of Physics and Astronomy at the University of Birmingham, UK, in collaboration with Sheffield Hallam University, UK. It is funded by the Science and Technology Facilities Council (STFC).

About the logo Thanks to Pete Marenfield of NOAO for the artistic finishing touches.