SDO/HMI survey of emerging active regions for helioseismology

Abstract

Observations from the Solar Dynamics Observatory (SDO) have the potential for allowing the helioseismic study of the formation of hundreds of active regions, which would enable us to perform statistical analyses. Our goal is to collate a uniform data set of emerging active regions observed by the SDO/HMI instrument suitable for helioseismic analysis up to seven days before emergence. We restricted the sample to active regions that were visible in the continuum and emerged into quiet Sun largely avoiding pre-existing magnetic regions. As a reference data set we paired a control region (CR), with the same latitude and distance from central meridian, with each emerging active region (EAR). We call this data set, which is currently comprised of 105 emerging active regions observed between May 2010 and November 2012, the SDO Helioseismic Emerging Active Region (SDO/HEAR) survey. To demonstrate the utility of a data set of a large number of emerging active regions, we measure the relative east-west velocity of the leading and trailing polarities from the line-of-sight magnetogram maps during the first day after emergence. The latitudinally averaged line-of-sight magnetic field of all the EARs shows that, on average, the leading (trailing) polarity moves in a prograde (retrograde) direction with a speed of 121 +/- 22 m/s (-70 +/- 13 m/s) relative to the Carrington rotation rate in the first day. However, relative to the differential rotation of the surface plasma, the east-west velocity is symmetric, with a mean of 95 +/- 13 m/s. The SDO/HEAR data set will not only be useful for helioseismic studies, but will also be useful to study other features such as the surface magnetic field evolution of a large sample of EARs.

arXiv commentAccepted by Astronomy and Astrophysics, 11 figures, one longtable; update corrects units in Figure 1

References in corpus (15)

• The Helioseismic and Magnetic Imager (HMI) Vector Magnetic Field Pipeline: SHARPs -- Space-weather HMI Active Region Patches
• The case for a distributed solar dynamo shaped by near-surface shear
• Simulation of the Formation of a Solar Active Region
• Buoyant Magnetic Loops Generated by Global Convective Dynamo Action
• Solar Flux Emergence Simulations
• Comparing Simulations of Rising Flux Tubes Through the Solar Convection Zone with Observations of Solar Active Regions: Constraining the Dynamo Field Strength
• Helioseismology of Pre-Emerging Active Regions II: Average Emergence Properties
• A low upper limit on the subsurface rise speed of solar active regions
• Tilt Angle and Footpoint Separation of Small and Large Bipolar Sunspot Regions Observed with HMI
• Signatures of Emerging Subsurface Structures in Acoustic Power Maps
• Mean-field and direct numerical simulations of magnetic flux concentrations from vertical field
• Helioseismology of Pre-Emerging Active Regions I: Overview, Data, and Target Selection Criteria
• Helioseismology of Pre-Emerging Active Regions III: Statistical Analysis
• Helioseismic Holography of an Artificial Submerged Sound Speed Perturbation and Implications for the Detection of Pre-Emergence Signatures of Active Regions
• Local helioseismology and the active Sun

Cited by in corpus (17)

• Emergence of magnetic flux generated in a solar convective dynamo. I: Formation of Sunspots and Active regions, and Origin of Their Asymmetries
• Waves in the lower solar atmosphere: the dawn of next-generation solar telescopes
• SMARPs and SHARPs: Two Solar Cycles of Active Region Data
• Average motion of emerging solar active region polarities II: Joy's law
• Magnetic helicity and energy of emerging solar active regions and their erruptivity
• Average motion of emerging solar active region polarities I: Two phases of emergence
• The rotation rate of solar active and ephemeral regions -- II. Temporal variations of the rotation rates
• Application and interpretation of deep learning for identifying pre-emergence magnetic-field patterns
• On Strengthening of the Solar f-mode Prior to Active Region Emergence Using the Fourier-Hankel Analysis
• Coriolis force acting on near-surface horizontal flows during simulations of flux emergence produces a tilt angle consistent with Joy's law on the Sun
• Average solar active region: I. Intensities, velocities, and the photospheric magnetic field
• A new look at sunspot formation using theory and observations
• Emerging Dimming as Coronal Heating Episodes
• Pre-emergence Signatures Of Horizontal Divergent Flows In Solar Active Regions
• Evolution of the magnetic field and flows of solar active regions with persistent magnetic bipoles before emergence
• Testing solar surface flux transport models in the first days after active region emergence
• Evolution of solar surface inflows around emerging active regions