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Title: INWARD MOTIONS IN THE OUTER SOLAR CORONA BETWEEN 7 AND 12 R {sub ⊙}: EVIDENCE FOR WAVES OR MAGNETIC RECONNECTION JETS?

Abstract

DeForest et al. used synoptic visible-light image sequences from the COR2 coronagraph on board the STEREO-A spacecraft to identify inbound wave motions in the outer corona beyond 7 solar radii and inferred, from the observation, that the Alfvén surface separating the magnetically dominated corona from the flow dominated wind must be located beyond at least 12 solar radii from the Sun over polar coronal holes and beyond 15 solar radii in the streamer belt. Here, we attempt identification of the observed inward signal by theoretically reconstructing height-speed diagrams and comparing them to the observed profiles. Interpretation in terms of Alfvén waves or Alfvénic turbulence appears to be ruled out by the fact that the observed signal shows a deceleration of inward motion when approaching the Sun. Fast magnetoacoustic waves are not directly ruled out in this way, as it is possible for inward waves observed in quadrature, but not propagating exactly radially, to suffer total reflection as the Alfvén speed rises close to the Sun. However, the reconstructed signal in the height-speed diagram has the wrong concavity. A final possibility is decelerating reconnection jets, most probably from component reconnection, in the accelerating wind: the profile in this case appears tomore » match the observations very well. This interpretation does not alter the conclusion that the Alfvén surface must be at least 12 solar radii from the photosphere. Further observations should help constrain this process, never identified previously in this way, in the distance range from 7 to 12 solar radii.« less

Authors:
;  [1];  [2]
  1. EPSS, UCLA, Los Angeles, CA (United States)
  2. Southwest Research Institute, 1050 Walnut Street, Boulder, CO (United States)
Publication Date:
OSTI Identifier:
22654286
Resource Type:
Journal Article
Resource Relation:
Journal Name: Astrophysical Journal Letters; Journal Volume: 825; 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; ACCELERATION; ALFVEN WAVES; COMPARATIVE EVALUATIONS; FAST MAGNETOACOUSTIC WAVES; IMAGES; MAGNETIC RECONNECTION; MAGNETOACOUSTICS; MAGNETOHYDRODYNAMICS; PHOTOSPHERE; QUADRATURES; REFLECTION; SOLAR CORONA; SOLAR WIND; SPACE VEHICLES; SUN; SURFACES; TURBULENCE; VELOCITY; VISIBLE RADIATION

Citation Formats

Tenerani, Anna, Velli, Marco, and DeForest, Craig, E-mail: annatenerani@epss.ucla.edu. INWARD MOTIONS IN THE OUTER SOLAR CORONA BETWEEN 7 AND 12 R {sub ⊙}: EVIDENCE FOR WAVES OR MAGNETIC RECONNECTION JETS?. United States: N. p., 2016. Web. doi:10.3847/2041-8205/825/1/L3.
Tenerani, Anna, Velli, Marco, & DeForest, Craig, E-mail: annatenerani@epss.ucla.edu. INWARD MOTIONS IN THE OUTER SOLAR CORONA BETWEEN 7 AND 12 R {sub ⊙}: EVIDENCE FOR WAVES OR MAGNETIC RECONNECTION JETS?. United States. doi:10.3847/2041-8205/825/1/L3.
Tenerani, Anna, Velli, Marco, and DeForest, Craig, E-mail: annatenerani@epss.ucla.edu. Fri . "INWARD MOTIONS IN THE OUTER SOLAR CORONA BETWEEN 7 AND 12 R {sub ⊙}: EVIDENCE FOR WAVES OR MAGNETIC RECONNECTION JETS?". United States. doi:10.3847/2041-8205/825/1/L3.
@article{osti_22654286,
title = {INWARD MOTIONS IN THE OUTER SOLAR CORONA BETWEEN 7 AND 12 R {sub ⊙}: EVIDENCE FOR WAVES OR MAGNETIC RECONNECTION JETS?},
author = {Tenerani, Anna and Velli, Marco and DeForest, Craig, E-mail: annatenerani@epss.ucla.edu},
abstractNote = {DeForest et al. used synoptic visible-light image sequences from the COR2 coronagraph on board the STEREO-A spacecraft to identify inbound wave motions in the outer corona beyond 7 solar radii and inferred, from the observation, that the Alfvén surface separating the magnetically dominated corona from the flow dominated wind must be located beyond at least 12 solar radii from the Sun over polar coronal holes and beyond 15 solar radii in the streamer belt. Here, we attempt identification of the observed inward signal by theoretically reconstructing height-speed diagrams and comparing them to the observed profiles. Interpretation in terms of Alfvén waves or Alfvénic turbulence appears to be ruled out by the fact that the observed signal shows a deceleration of inward motion when approaching the Sun. Fast magnetoacoustic waves are not directly ruled out in this way, as it is possible for inward waves observed in quadrature, but not propagating exactly radially, to suffer total reflection as the Alfvén speed rises close to the Sun. However, the reconstructed signal in the height-speed diagram has the wrong concavity. A final possibility is decelerating reconnection jets, most probably from component reconnection, in the accelerating wind: the profile in this case appears to match the observations very well. This interpretation does not alter the conclusion that the Alfvén surface must be at least 12 solar radii from the photosphere. Further observations should help constrain this process, never identified previously in this way, in the distance range from 7 to 12 solar radii.},
doi = {10.3847/2041-8205/825/1/L3},
journal = {Astrophysical Journal Letters},
number = 1,
volume = 825,
place = {United States},
year = {Fri Jul 01 00:00:00 EDT 2016},
month = {Fri Jul 01 00:00:00 EDT 2016}
}