skip to main content
OSTI.GOV title logo U.S. Department of Energy
Office of Scientific and Technical Information

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. 2016. "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 = 2016,
month = 7
}
  • We study 14 large solar jets observed in polar coronal holes. In EUV movies from the Solar Dynamics Observatory/Atmospheric Imaging Assembly (AIA), each jet appears similar to most X-ray jets and EUV jets that erupt in coronal holes; but each is exceptional in that it goes higher than most, so high that it is observed in the outer corona beyond 2.2 R{sub Sun} in images from the Solar and Heliospheric Observatory/Large Angle Spectroscopic Coronagraph (LASCO)/C2 coronagraph. From AIA He ii 304 Å movies and LASCO/C2 running-difference images of these high-reaching jets, we find: (1) the front of the jet transitsmore » the corona below 2.2 R{sub Sun} at a speed typically several times the sound speed; (2) each jet displays an exceptionally large amount of spin as it erupts; (3) in the outer corona, most of the jets display measureable swaying and bending of a few degrees in amplitude; in three jets the swaying is discernibly oscillatory with a period of order 1 hr. These characteristics suggest that the driver in these jets is a magnetic-untwisting wave that is basically a large-amplitude (i.e., nonlinear) torsional Alfvén wave that is put into the reconnected open field in the jet by interchange reconnection as the jet erupts. From the measured spinning and swaying, we estimate that the magnetic-untwisting wave loses most of its energy in the inner corona below 2.2 R{sub Sun}. We point out that the torsional waves observed in Type-II spicules might dissipate in the corona in the same way as the magnetic-untwisting waves in our big jets, and thereby power much of the coronal heating in coronal holes.« less
  • The heliosphere is formed due to interaction between the solar wind (SW) and local interstellar medium (LISM). The shape and position of the heliospheric boundary, the heliopause, in space depend on the parameters of interacting plasma flows. The interplay between the asymmetrizing effect of the interstellar magnetic field and charge exchange between ions and neutral atoms plays an important role in the SW–LISM interaction. By performing three-dimensional, MHD plasma/kinetic neutral atom simulations, we determine the width of the outer heliosheath—the LISM plasma region affected by the presence of the heliosphere—and analyze quantitatively the distributions in front of the heliopause. Itmore » is shown that charge exchange modifies the LISM plasma to such extent that the contribution of a shock transition to the total variation of plasma parameters becomes small even if the LISM velocity exceeds the fast magnetosonic speed in the unperturbed medium. By performing adaptive mesh refinement simulations, we show that a distinct boundary layer of decreased plasma density and enhanced magnetic field should be observed on the interstellar side of the heliopause. We show that this behavior is in agreement with the plasma oscillations of increasing frequency observed by the plasma wave instrument onboard Voyager 1. We also demonstrate that Voyager observations in the inner heliosheath between the heliospheric termination shock and the heliopause are consistent with dissipation of the heliospheric magnetic field. The choice of LISM parameters in this analysis is based on the simulations that fit observations of energetic neutral atoms performed by Interstellar Boundary Explorer .« less