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Title: Photospheric Velocity Structures during the Emergence of Small Active Regions on the Sun

Abstract

We study the plasma flows in the solar photosphere during the emergence of two small active regions, NOAA 9021 and 10768. Using Solar and Heliospheric Observatory /Michelson Doppler Imager data, we find that the strong plasma upflows appear at the initial stage of active region formation, with maximum upflow velocities of −1650 and −1320 m s{sup −1}. The structures with enhanced upflows have size ∼8 Mm in diameter, and they exist for 1–2 hr. The parameters of the enhanced upflows are consistent with those of the large active region NOAA 10488, which may suggest the possibility that the elementary emerging magnetic loops that appear at the earliest phase of active region formation have similar properties, irrespective of scales of active regions. Comparison between the observations and a numerical simulation of magnetic flux emergence shows a striking consistency. We find that the driving force of the plasma upflow is at first the gas pressure gradient and later the magnetic pressure gradient.

Authors:
 [1];  [2]
  1. Institute of Solar-Terrestrial Physics SB RAS, Lermontov St., 126a, 664033 Irkutsk (Russian Federation)
  2. National Astronomical Observatory of Japan, 2-21-1 Osawa, Mitaka, Tokyo 181-8588 (Japan)
Publication Date:
OSTI Identifier:
22661139
Resource Type:
Journal Article
Resource Relation:
Journal Name: Astrophysical Journal; Journal Volume: 839; Journal Issue: 1; Other Information: Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
79 ASTROPHYSICS, COSMOLOGY AND ASTRONOMY; COMPARATIVE EVALUATIONS; COMPUTERIZED SIMULATION; MAGNETIC FIELDS; MAGNETIC FLUX; PHOTOSPHERE; PLASMA; PRESSURE GRADIENTS; SUN; VELOCITY

Citation Formats

Khlystova, Anna, and Toriumi, Shin, E-mail: hlystova@iszf.irk.ru, E-mail: shin.toriumi@nao.ac.jp. Photospheric Velocity Structures during the Emergence of Small Active Regions on the Sun. United States: N. p., 2017. Web. doi:10.3847/1538-4357/AA688F.
Khlystova, Anna, & Toriumi, Shin, E-mail: hlystova@iszf.irk.ru, E-mail: shin.toriumi@nao.ac.jp. Photospheric Velocity Structures during the Emergence of Small Active Regions on the Sun. United States. doi:10.3847/1538-4357/AA688F.
Khlystova, Anna, and Toriumi, Shin, E-mail: hlystova@iszf.irk.ru, E-mail: shin.toriumi@nao.ac.jp. Mon . "Photospheric Velocity Structures during the Emergence of Small Active Regions on the Sun". United States. doi:10.3847/1538-4357/AA688F.
@article{osti_22661139,
title = {Photospheric Velocity Structures during the Emergence of Small Active Regions on the Sun},
author = {Khlystova, Anna and Toriumi, Shin, E-mail: hlystova@iszf.irk.ru, E-mail: shin.toriumi@nao.ac.jp},
abstractNote = {We study the plasma flows in the solar photosphere during the emergence of two small active regions, NOAA 9021 and 10768. Using Solar and Heliospheric Observatory /Michelson Doppler Imager data, we find that the strong plasma upflows appear at the initial stage of active region formation, with maximum upflow velocities of −1650 and −1320 m s{sup −1}. The structures with enhanced upflows have size ∼8 Mm in diameter, and they exist for 1–2 hr. The parameters of the enhanced upflows are consistent with those of the large active region NOAA 10488, which may suggest the possibility that the elementary emerging magnetic loops that appear at the earliest phase of active region formation have similar properties, irrespective of scales of active regions. Comparison between the observations and a numerical simulation of magnetic flux emergence shows a striking consistency. We find that the driving force of the plasma upflow is at first the gas pressure gradient and later the magnetic pressure gradient.},
doi = {10.3847/1538-4357/AA688F},
journal = {Astrophysical Journal},
number = 1,
volume = 839,
place = {United States},
year = {Mon Apr 10 00:00:00 EDT 2017},
month = {Mon Apr 10 00:00:00 EDT 2017}
}