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Title: THE NAKED EMERGENCE OF SOLAR ACTIVE REGIONS OBSERVED WITH SDO/HMI

Abstract

We take advantage of the HMI/SDO instrument to study the naked emergence of active regions (ARs) from the first imprints of the magnetic field on the solar surface. To this end, we followed the first 24 hr in the life of two rather isolated ARs that appeared on the surface when they were about to cross the central meridian. We analyze the correlations between Doppler velocities and the orientation of the vector magnetic field, consistent finding that the horizontal fields connecting the main polarities are dragged to the surface by relatively strong upflows and are associated with elongated granulation that is, on average, brighter than its surroundings. The main magnetic footpoints, on the other hand, are dominated by vertical fields and downflowing plasma. The appearance of moving dipolar features (MDFs, of opposite polarity to that of the AR) in between the main footpoints is a rather common occurrence once the AR reaches a certain size. The buoyancy of the fields is insufficient to lift up the magnetic arcade as a whole. Instead, weighted by the plasma that it carries, the field is pinned down to the photosphere at several places in between the main footpoints, giving life to the MDFsmore » and enabling channels of downflowing plasma. MDF poles tend to drift toward each other, merge and disappear. This is likely to be the signature of a reconnection process in the dipped field lines, which relieves some of the weight allowing the magnetic arcade to finally rise beyond the detection layer of the Helioseismic and Magnetic Imager spectral line.« less

Authors:
 [1]
  1. High Altitude Observatory (NCAR), 3080 Center Green Dr., Boulder, CO 80301 (United States)
Publication Date:
OSTI Identifier:
22086451
Resource Type:
Journal Article
Journal Name:
Astrophysical Journal
Additional Journal Information:
Journal Volume: 759; Journal Issue: 1; Other Information: Country of input: International Atomic Energy Agency (IAEA); Journal ID: ISSN 0004-637X
Country of Publication:
United States
Language:
English
Subject:
79 ASTROPHYSICS, COSMOLOGY AND ASTRONOMY; ASTRONOMY; CORRELATIONS; GRANULATION; MAGNETIC FIELDS; ORIENTATION; PHOTOSPHERE; PLASMA; POLARIMETRY; SUN; SUNSPOTS; SURFACES; TOPOLOGY

Citation Formats

Centeno, Rebecca. THE NAKED EMERGENCE OF SOLAR ACTIVE REGIONS OBSERVED WITH SDO/HMI. United States: N. p., 2012. Web. doi:10.1088/0004-637X/759/1/72.
Centeno, Rebecca. THE NAKED EMERGENCE OF SOLAR ACTIVE REGIONS OBSERVED WITH SDO/HMI. United States. doi:10.1088/0004-637X/759/1/72.
Centeno, Rebecca. Thu . "THE NAKED EMERGENCE OF SOLAR ACTIVE REGIONS OBSERVED WITH SDO/HMI". United States. doi:10.1088/0004-637X/759/1/72.
@article{osti_22086451,
title = {THE NAKED EMERGENCE OF SOLAR ACTIVE REGIONS OBSERVED WITH SDO/HMI},
author = {Centeno, Rebecca},
abstractNote = {We take advantage of the HMI/SDO instrument to study the naked emergence of active regions (ARs) from the first imprints of the magnetic field on the solar surface. To this end, we followed the first 24 hr in the life of two rather isolated ARs that appeared on the surface when they were about to cross the central meridian. We analyze the correlations between Doppler velocities and the orientation of the vector magnetic field, consistent finding that the horizontal fields connecting the main polarities are dragged to the surface by relatively strong upflows and are associated with elongated granulation that is, on average, brighter than its surroundings. The main magnetic footpoints, on the other hand, are dominated by vertical fields and downflowing plasma. The appearance of moving dipolar features (MDFs, of opposite polarity to that of the AR) in between the main footpoints is a rather common occurrence once the AR reaches a certain size. The buoyancy of the fields is insufficient to lift up the magnetic arcade as a whole. Instead, weighted by the plasma that it carries, the field is pinned down to the photosphere at several places in between the main footpoints, giving life to the MDFs and enabling channels of downflowing plasma. MDF poles tend to drift toward each other, merge and disappear. This is likely to be the signature of a reconnection process in the dipped field lines, which relieves some of the weight allowing the magnetic arcade to finally rise beyond the detection layer of the Helioseismic and Magnetic Imager spectral line.},
doi = {10.1088/0004-637X/759/1/72},
journal = {Astrophysical Journal},
issn = {0004-637X},
number = 1,
volume = 759,
place = {United States},
year = {2012},
month = {11}
}