A low upper limit on the subsurface rise speed of solar active regions
arXiv:1607.05250 · doi:10.1126/sciadv.1600557
Abstract
Magnetic field emerges at the surface of the Sun as sunspots and active regions. This process generates a poloidal magnetic field from a rising toroidal flux tube, it is a crucial but poorly understood aspect of the solar dynamo. The emergence of magnetic field is also important because it is a key driver of solar activity. We show that measurements of horizontal flows at the solar surface around emerging active regions, in combination with numerical simulations of solar magnetoconvection, can constrain the subsurface rise speed of emerging magnetic flux. The observed flows imply that the rise speed of the magnetic field is no larger than 150 m/s at a depth of 20 Mm, that is, well below the prediction of the (standard) thin flux tube model but in the range expected for convective velocities at this depth. We conclude that convective flows control the dynamics of rising flux tubes in the upper layers of the Sun and cannot be neglected in models of flux emergence.
arXiv commentPublished in Science Advances. DOI: 10.1126/sciadv.1600557
References in corpus (17)
- The case for a distributed solar dynamo shaped by near-surface shear
- Numerical simulations of quiet Sun magnetism: On the contribution from a small-scale dynamo
- Simulation of the Formation of a Solar Active Region
- Local Helioseismology: Three Dimensional Imaging of the Solar Interior
- Magnetic Wreaths and Cycles in Convective Dynamos
- Numerical simulations of active region scale flux emergence: From spot formation to decay
- On the Formation of Active Regions
- Three dimensional non-linear evolution of a magnetic flux tube in a spherical shell: Influence of turbulent convection and associated mean flows
- 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
- Surface-focused Seismic Holography of Sunspots: I. Observations
- Photospheric and Subphotospheric Dynamics of Emerging Magnetic Flux
- Global Dynamics of Subsurface Solar Active Regions
- Helioseismology of Pre-Emerging Active Regions I: Overview, Data, and Target Selection Criteria
- Time-Distance analysis of the Emerging Active Region NOAA 10790
- Doubts about the crucial role of the rising-tube mechanism in the formation of sunspot groups
- Data compression for local correlation tracking of solar granulation
Cited by in corpus (27)
- Emergence of magnetic flux generated in a solar convective dynamo. I: Formation of Sunspots and Active regions, and Origin of Their Asymmetries
- Magnetic Flux Emergence and Decay Rates for Preceder and Follower Sunspots Observed with HMI
- On rising magnetic flux tube and formation of sunspots in a deep domain
- IRIS observations of magnetic interactions in the solar atmosphere between pre-existing and emerging magnetic fields. I. Overall evolution
- A Tale of Two Emergences: Sunrise II Observations of Emergence Sites in a Solar Active Region
- SDO/HMI survey of emerging active regions for helioseismology
- Average motion of emerging solar active region polarities II: Joy's law
- Magnetic concentrations in stratified turbulence: the negative effective magnetic pressure instability
- Average motion of emerging solar active region polarities I: Two phases of emergence
- Flows around Averaged Solar Active Regions
- High-wavenumber solar -mode strengthening prior to active region formation
- The origin and early evolution of a bipolar magnetic region in the solar photosphere
- Signal and noise in helioseismic holography
- Current systems of coronal loops in 3D MHD simulations
- Photospheric Velocity Structures during the Emergence of Small Active Regions on the Sun
- Imaging the Sun's near-surface flows using mode-coupling 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
- Exploring the Connection between Helioseismic Travel Time Anomalies and the Emergence of Large Active Regions during Solar Cycle 24
- Average solar active region: I. Intensities, velocities, and the photospheric magnetic field
- A new look at sunspot formation using theory and observations
- Observed Joys law of Bipolar Magnetic Region tilts at the emergence supports the thin flux tube model
- Evolution of the magnetic field and flows of solar active regions with persistent magnetic bipoles before emergence
- Solar active region scaling laws revisited
- Solar Interior
- Magnetic bipoles in rotating turbulence with coronal envelope
- Evolution of solar surface inflows around emerging active regions
- Thermomagnetic Ettingshausen-Nernst effect in tachocline, magnetic reconnection phenomenon in lower layers, axion mechanism of solar luminosity variations, coronal heating problem solution and mechanism of ADM variations around BH